Document MGLvQD2Y93b7E4K36qGKZaLEy

Ua^J- /-JL/-6 V APRi Date_____ f -J-6SL This book, is the pont'ertv of F.tbvl Cor poration a ad is aligned as desk copy to: ''ha ___________ __ Please return ih: hook to the Chemical Development Library when no longer Deeded. E7bVL GliOfiJAl &v.u/: <4mT L'"hArY ?. 5. ;?. 341 3A7CN ROUSE 1. Lhu-SiANA Safety and Accident Prevention in Chemical Operations Safety and Accident Prevention in Chemical Operations HOWARD H. FAWCETT Research Laboratory General Electric Company Schenectady. New York Now: Technical Secretary National Academy of Sciences-- United States Coast Guard Advisory Committee on Hazardous Materials WILLIAM S. WOOD Safety Engineer Research and Development Division Sun Oil Company Marcus Hook, Pennsylvania Interscience Publishers a Division of John Wiley & Sons New York London Sydney ETC 03014 N Copyright 1965 BY John Wiley & Sons, Inc. All Rights Reserved This book or any part thereof must not be reproduced in any form without the written permission of the publisher. Library of Congress Catalog Card Number: 65-12712 PRINTED IN THE UNITED STATES OF AMERICA ETC 03016 Foreword Realities in Accident Causation The popular present day concept of an accident is: To the victim and his family ultimate tragedy, To the witness a profound and horrifying experience which in time becomes a conversation piece, To his company a preventable and irreparable loss of an employee, To the public a news item, To the legal courts an "act of God," To the government a statistic, and To the nation a tragic, unnecessary loss. Despite all one hears concerning this modern age, accidents are as preventable today as they were in the dim past when man would roll a stone over his big toe while securing his cave for the night. The safety engineer, as with all professional men concerned with the pres ervation of life and limb, has no illusions about defining an accident. To him an accident is a series of coincidental events whose climax results in personal injury, property damage, or both. He holds that these series of events are within the scope of human control barring an "act of God." The successful safety engineer is not permitted the luxury of loose thinking and glib generalizations in arriving at his definitions. He can have no part of the alibi psychosis which today has become so much a part of human behaviorism that it is almost autogenetic. When he speaks of an "act of God," he is referring to an accident vit ETC 03017 viii Foreword whose cause analysis failed to show in the series of events a contribu tory act of commission or omission on the part of any person. The "act of God" accidents are rare, and many safety engineers are hard pressed to cite one such accident, even after many years of expe rience. Their very scarcity demands a descriptive comparison here. If a man is walking down the road under a clear blue sky and because of some freak of nature beyond our understanding or control he is struck by lightning and killed, the cause analysis can truthfully read "an act of God." If the same man continues gauging and sampling steel tanks as a thunderstorm approaches and he is killed by lightning, to the safety engineer this is not an "act of God" because the deceased, through an act or omission of an act, has contributed to the cause of his own death. Understandably, the rigid interpretive definitions of the safety engi neer often do not receive general popular acceptance, either by man agement or personnel. To ignore or discourage the best thinking of the safety engineer is as asinine as a patient offering his doctor an additional fee for a more favorable diagnosis. Following fatal acci dents there is sometimes a tendency for those concerned to seek the cover of an alibi or even a false alibi, but no alibi or group of alibis can explain away that pathetic occupant of the morgue slab. The natural tendency of our ever-present, highly developed defense mechanisms to taint our definition with alibis is a violation of the basic law of self-preservation. Such violations often make possible the series of events whose climax consists of an accident. If we create these series of events, they are within the scope of our control. In the field of accident prevention to be inaccurate in definition is to turn away from today's error only to come face to face with tomorrow's tragedy. Cause Analysis The lessons taught the injured (if he survives) and others con cerned are the only items that may be entered on the credit side of the ledger when an accident is experienced. Safe practices, codes, standards, and regulations have not been created from the known laws of physics, chemistry, and physiology alone. All safety codes and regulations bear the unqualified endorsement of the ghostly hands of industry's early accident victims. No execu tive, regardless of scope of authority or vastness of organization, can acquire a sound accident prevention program by merely giving orders. He can only initiate, guide, and support it. Safety programs that Foreword ix yield constant low-frequency and severity rates are the results of the co-operative efforts of all, from executive management to the newest employee. A prerequisite to successful cooperation is the realization that safety is efficiency. We cannot have one without the other. All groups that make up the people of industry agree on the worth and desirability of safety's objective, yet solidarity is often lost when enforcement is necessary to insure attainment of an accident-free plant. It is not enough for management to provide safe facilities and procedures. There must be a fair and equitable discipline to maintain safe working conditions. When deliberate safety violations occur there should be no compro mise in discipline for the sake of expediency. Any such doubtful bene fits acquired are but temporary and in their passing sow the seeds of destruction in the form of accidents, just as fixing a traffic ticket may contribute in a small but important way to the death of the next child killed on the highway. One of the most important and necessary weapons in the war against accidents is the cause analysis. To be effective the method of analyz ing the causes of accidents must be accurate, thorough, logical, im personal, simple, and readily understood. by all parties concerned. The type of cause analysis known as "the immediate cause and con tributing factor" most nearly meets all the above requirements. Accident investigation is seldom simple, but the less complicated the method used the greater the chance of uncovering the true causes in an acceptable manner. Many times the cause of the injury is erro neously given as the cause of the accident. A caustic liquid splashing into the eye is cause of the injury, but whatever circumstance per mitted the liquid to leave its proper containment is the cause of the accident. If the analysis is to be of use in accident prevention, logic must prevail. It is not enough to say that "while injured was climbing the ladder he failed to keep a secure grip on the ladder rungs" especially when the contributing factors reveal that the injured was carrying a section of hose over his shoulder and a bucket in one hand while climb ing the ladder. Repetitive use of the expression "the injured failed to do" this or that indicates either dishonest reporting or the failure of supervision to carry out its mission. If every employee always followed orders, there would be 75% less foremen in industry. The very act of be stowing the title of foreman is recognition of leadership ability, the ability not only to receive and properly give orders, but to see that the orders are carried out efficiently. x Foreword Chronic employee failure is supervision failure. If there is a gen eral sense of justifiable pride in the maintenance of a good safety record, then there must be a general acceptance of responsibility for a bad record. The safety engineer abhors the title of expert, reluc tantly accepts the title of specialist, and he of all persons must "prac tice what he preaches." A safety engineer [the author] once investigated an accident where an employee suffered a serious injury from a fall while descending stairs from tank tops to the ground. All conditions at the accident site appeared normal, and the safety engineer submitted a smug report stating in part "the actions of the injured were the greatest contribu tion to the cause." The very next day at the very same time a second employee was injured under identical conditions. This time a more thorough investigation revealed an unannounced change in processing which released deadly hydrogen sulphide gas in the area. This lack of interdepartmental communication changed a normally safe opera tion into a potential death trap. The safety engineer, when construct ing his second cause analysis, gave as one of the contributing factors, "Failure of the safety department to properly investigate the previous accident." When a series of accidents arises from identical causes, then super vision must bear an increasing proportion of responsibility for each succeeding accident. The theory of calculated risk, so necessary to competitive progress, must be limited to dollars and cents. Any attempt by supervision or employee to apply this theory to life and limb can only end in eventual disaster. The preceding statement is generally accepted as a matter of principle, yet in the daily score of industrial accidents, many are the result of ignoring this principle. The overextension of equipment and inadequate maintenance by supervision, the departure from safe practices and regulations (the so-called short cut) by the individual employee are more common forms of violating this principle. Calculated risk to life and limb would be a small problem if those who did the calculating were the only persons exposed to the risk. Just as the navigator must know where he has been in order to plot the course to his destination, so too must industry know through proper analysis what caused the acci dents of yesterday, how to insure maximum safety today, and how to plan intelligent accident prevention of tomorrow. The Specter of Monotony There are certain types of accidents whose causes remain the same through the years; only the victims are new. These causes have noth- Foreword x* ing to do with modern processes and advanced technology. They are the same causes that brought injury and death to our fathers' and grandfathers' generations. The plasterer who lost the sight of an eye from contact with quicklime, and his son, who twenty years later lost an eye while carrying out an unguarded ether distillation, are equally handicapped. The fact that the father went as far as the sixth grade in school and the son was a college graduate seems to have little or no bearing on the cause of their accidents. The father had seen fellow workers blinded while committing the unsafe act that cost him his eye, and the son understood well the peroxide instability that brought about his permanent disability. Education alone is not complete protection against this type of accident. An experienced operator can reprimand a helper for not wearing goggles while drawing acid from a drum and the next day suffer severe burns while "rodding" out a plugged line with the valve open. Ex perience alone is not complete protection against this type of acci dent. The superintendent of a gas works was awakened by his wife during the night because she had detected a strong odor of gas in the house. He berated his wife for having turned on the lights in the presence of gas. Having made this contribution to his wife's educa tion, he turned out the lights and in doing so blew up the house. Technical knowledge alone is not complete protection against this type of accident. The safety man readily admits that all cause analyses contain the element of error, but the term error implies that judgment has been exercised whereas in many accident causes judgment is lacking en tirely. The term, negligence, cannot be used as an overall description. Negligence smacks of deliberate neglect or mental and physical lazi ness. The courts of the land use the term, negligence, as a yardstick to measure the degree of responsibility. The word carelessness is inept, bearing as it does the connotation of "couldn't care less." In the area of chronic accident causes the only term that can be applied to behaviorism that is otherwise an insult to our intelligence is "mental lapse." Mental lapse is often the prime mover that sets in motion the series of events that end in disaster. The causes of mental lapses can be varied and complex, but they all have one thing in common. They flourish in an atmosphere of monotony. The expression "another day, another dollar" is a familiar form of acknowledging the impact of monotony on our daily lives. Most of us have a remarkably short concentration span even under ideal con ditions. Distraction, the antithesis of concentration, usually arises from two general sources: external, such as noise and motion, and internal, the never ending thought processes that are the price of in- xii Foreword tellect. Through experience acquired from practice we develop indus trial skill to a high degree as an individual, as a department, as a plant, and as an industry. This skill, absolutely necessary for safe operation, is not static in the sense that once attained, perfection re sults automatically. In the field of accident prevention it is paradoxical that the most skillful are in the greatest need of additional skills. If a safety en gineer arrives at that "predisaster" stage knowing all the answers, he becomes the epitome of hazards. The rubber mill operator who has developed sufficient mental and manual dexterity to meet his work quota and daydream at the same time has not necessarily acquired sufficient skill to afford protection against accidents. He has succumbed to the influence of monotony, and the slightest change in repetitive function, either human or me chanical, can bring him face to face with deadly peril, as the rotation of the rollers hypnotizes the thought processes. The psychological sins of accident causation are monotony and complacency. The most deadly is monotony. Since the turn of the century, industry has made the greatest progress in the history of mankind. We have turned from splitting wood to splitting the atom, adding immeasurably to our store of knowledge. Whether this knowledge will result in a better or a shorter life for us all only the future can tell. We do know with certainty that we cannot relax our efforts in accident prevention, for as members of supervision we are the custodians of a sacred trust; that is, the pro tection of life and limb. Just as the surgeon or the lawyer cannot let the element of monotony interfere with his daily life and death struggles, so we too cannot permit accident prevention to become monotonous. In this work we are fortified and inspired by the high est of ideals, but there is also a selfish motivation. The mortuary is the abode of pure democracy, and the accident we fail to prevent may be our own. Alfred J. Goranrt Preface It is perhaps significant that no one has heretofore collected under one cover a treatise on safety in the chemical industry. The diversity of problems has caused most of the outstanding men in the field of chemical safety to specialize to a considerable degree, thus few can didates would be qualified to write a book covering the whole subject. We, the editors, likewise felt our incompetence, and for this reason we have tried to collect some of the best thinking of leaders in their respective specialties. We feel that herein is reflected the distilled wisdom and judgment of practical men and women who have made some phase of accident prevention their life work, and who have demonstrated over and over in their daily endeavors, that accidents can be prevented and controlled. This book is highly experimental It certainly is far from perfect, and the editors consider it only a first attempt to provide a useful reference for people involved with chemical safety. Hopefully it will encourage research and publica tion of further, needed information on chemical safety--perhaps another book. Since effective control of accidental injury and property damage in chemical operations is based on such a broad spectrum of knowledge, the scope of this book is necessarily quite wide. Chemical safety re quires the study of man in his industrial environment, considers the properties of the materials involved, requires exhaustive analysis of the chemical reaction or operation, and also covers the final packag ing and shipping of the product in an acceptable manner. At any place in this chain, loss of control may lead to injury: from mechani cal forces, from fires, from explosives, or from toxicity. These acci dents in addition to injuring the worker, possibly causing permanent injury or even death, also constitute a financial loss. They delay the process and reduce the contribution that the industry makes to society. Losses due to accidents can be materially reduced by application of the principles set forth in this book. Each chapter discusses a phase of chemical safety with direct application in many operations. In- xiii xiv Preface eluded are numerous literature references which will enable the reader to make a more thorough study than is possible here. Even if this book were perfect, we concede that it would still not prevent all accidents, for, as we have tried to emphasize, we do not completely understand the human being who works surrounded by the bewildering array of tanks, pipes, valves, vessels, and pumps used in chemical operations. The more nearly we approach, biologi cally and psychologically, an adequate understanding of man, the more nearly we will find success in accident control. Many whose names do not appear in print have supported and en couraged us in the preparation of this book. To these behind-thescenes friends, we extend our sincere appreciation and gratitude. To the supervisors in the chemical industry, to the designers of chemical equipment, to the safety personnel involved with chemical operations, to the management of chemical and related industries, we submit this book in the sincere hope that it will be a useful tool in helping to prevent injuries and losses due to accidents in chemical operations. Howard H. Fawcett William S. Wood Washington, D.C. West Chester, Pennsylvania December, 1964 Contents 1. Why Safety? Howard H. Fawcett 2. Who Makes Safety? Howard H. Fawcett 3. Organized Labor's Interest in Safety Elwood D. Swisher 4. Chemical Hazards and Worker Safety Stanley F. Spence 5. Safety Aspects of Site Selection, Plant Layout, and Unit Plot D. M. Liston 6. Services and Facilities David T. Smith 7. Hazards of Commercial Chemical Reactions George T. Austin 8. Hazards of Commercial Chemical Operations George T. Austin 9. Process Design W. G. Hudson 10. Instrumentation for Safe Operation Donald Richmond 11. Design and Inspection of Pressure Vessels Elliott MacDermod 12. Safety Education and Training M. A. Gimbel 13. Personal Behavior--Rules and Regulations M. A. Gimbel 14. Impact of Occupational Medicine on Safety 1 9 14 21 35 63 80 92 108 132 155 209 219 ETC 03025 ETC 03026 Contributing Authors George T. Austin, Ph.D. Chairman, Department of Chem istry and Engineering and Chief Chemical Engineer in the Divi sion of Industrial Research Washington State University Pullman, Washington Arthur H. Christian Division Safety Engineer American Viscose Division FMC Corporation Philadelphia, Pennsylvania Howard H. Fawcett, Technical Sec retary National Academy of Sciences-- United States Coast Guard Ad visory Committee on Hazard ous Materials Washington, D. C. John H. Foulger, M.D., Ph.D. Consultant, Clinical and Indus trial Toxicology Wilmington, Delaware Michael A. Gimbel Safety Consultant Havertown, Pennsylvania Alfred J. Gorand, Safety Coordina tor Sun Oil Company Philadelphia, Pennsylvania John V. Grimaldi, Ph.D., Consul tant, Health, Safety and Plant Protection General Electric Company New York, N. Y. Joseph Guelich, Safety Manager General Chemical Division Allied Chemical Corporation Morristown, New Jersey Arthur B. Guise, Manager Systems Engineering Fire Protection Products Division The Ansul Company Marinette, Wisconsin W. G. Hudson Manager, Pilot Plant Engineering Research and Development De partment M. W. Kellogg Company New Market, New Jersey D. J. Kilian, M.D., Medical Director Texas Division, Industrial Medi cine Department Dow Chemical Company Freeport, Texas Alan L. Kling, Director of Loss Pre vention Olin Mathiescn Chemical Corpo ration New York, N. Y. David M. Liston, Jr., Senior Infor mation Scientist Information Systems Research Group Battelle Memorial Institute Columbus, Ohio Elliott MacDermod, Senior Engi neer Bechtel Corp. Gaithersburg, Maryland Mrs. Eleanor Mort, R.N., B.A., M.N., Industrial Nurse Hooker Chemical Corporation Niagara Plant Niagara Falls, New York Jeremiah J. O'Driscoll, Divisional Safety Engineer Explosives Division, Atlas Chem ical Industries Wilmington, Delaware ETC 03028 Safety and Accident Prevention in Chemical Operations 1 Why Safety? H. H. Fawcett The prime purpose of business is to make money. To achieve this basic objective, needed goods and services are offered to customers at prices the customers can afford to pay, while the business still realizes a profit. Unless it is sufficiently profitable, the business is unsafe in the economic sense (and often in the personal injury sense as well), for profits are the usual method of financing research, development, new facilities, and new employment opportunities, as well as the health, safety, and fire protection programs. Furthermore, profitable businesses provide the support for the desirable noneconomic institu tions of our society, including schools, churches, government, and the arts. In operating a business profitably, a careful balance must be main tained to insure that four groups are properly serviced, namely, the owners (investors or shareholders), the customers, the employees, and the suppliers. Any imbalance in the relations with any group can ad versely affect the business health. The chemical and related industries occupy a key position in the economic life of the nation. The wide variety of chemical compositions and their finished forms, ranging the periodic chart from hydrogen to transuranic, is available in literally hundreds of thousands of mixtures and compounds. This variety constitutes a major supply house from which the chemical industry and all other industries can easily obtain new and better substances, or improved properties in older, more familiar products. Whole new industries have grown and continue to 1 ETC 03030 2 Safety and Accident Prevention in Chemical Operation* grow from laboratory experiments, properly developed and backed with the required capital investment. The chemical industry supplies a wide spectrum of products, which find their way into a wide range of human activity. Even life itself may be considered in terms of a series of chemical reactions--certainly chemicals, in the form of air we breathe, water and other beverages we drink, and food we eat, are essential to sustain and promote life. Since the chemical industry plays a vital role in our economic struc ture (even though much of this support is not obvious in the finished consumer product), the profitable performance of the chemical indus try becomes of vital concern far beyond the industry itself, since the supply as well as the price of chemicals is involved. A chemical plant that suddenly becomes a pile of twisted rubble or a crater in the ground cannot produce on schedule. Any factor that is an unnecessary cost, or economic loss to the chemical industry, must be borne in higher costs, and hence higher prices, paid by the customers in many other industries. The full cost of accidents is never completely covered by insurance, and never absorbed directly into operating expenses--ulti mately this cost raises the selling price and is passed on to consumers. For that reason, and many others, chemical safety can be an economic aid to a far wider field than chemical industry (Fig. 1.1). As used in this book, safety will be defined as a positive, organized activity or program based on knowledge of the reaction between man and his working environment, which aids business enterprise by mini mizing human, economic, and sociological losses caused by injuries, health impairment, fires, explosions, and other occupational accidents. It should be noted that this definition is both positive and dynamic, and does not depict safety as a passive obstructional activity that prevents constructive and profitable operations, but as an activity that aids them. A second objective of business, which may be considered an adjunct to profitability, is efficiency. In the chemical industry, many operating and supervisory positions are both specialized and complicated, hence, requiring a high degree of training and experience to achieve the maximum production with safety. If an accident of any type occurs, in which a highly trained employee is injured, the equipment damaged, or the product rendered scrap or substandard, another employee must be trained and repairs made, but frequently at a price in operating efficiency. In the technical areas, specific formulations and scientific know-how of a chemist or technician may be vital to the efficient functioning of the enterprise, and serious losses may occur if he is incapacitated by injury or disease. ETC 03032 4 Safety and Accident Prevention in Chemical Operations A third factor, closely related to economics and efficiency, is the human aspect. An ethical business, whether large or small, must have a proper consideration and respect for its employees, or it will soon have high labor turnover, a bad injury experience (and hence excessive compensation and medical costs), and poor morale. If an organized union exists in the plant, it will become increasingly vocal in its de mands for better conditions and job security, as well as higher wages. Business is not expected to be a benevolent fraternity, but it is not successful if run in the spirit of the "bull-of-the-woods" foremanship widely publicized a generation ago. Employees work best when they are led (not driven) by superiors in whom they have respect and trust, and who treat them with the dignity and understanding which is, after all, only a reflection of a human being. Regardless of the size of our income or the title of our job, each of us is responsive to proper treat ment, and reflect it in the zeal, loyalty, and quality of our work. Closely related to the human aspect is the public relations consid eration. A company image, like company integrity or company sta bility, is the hallmark of a successful business. The public, which extends far beyond the neighbors who live on the opposite side of the plant property line to the residents of the county, the state, and the nation, eventually form an opinion as to whether the company is a "good place to work" or a "place to avoid." If frequent accidents result in ambulance calls to the plant, if fires and explosions light up the night sky, if the news media, barred from the plant during an emergency, flash radio, television, and newspaper reports that are inaccurate and misleading, the public relations will suffer, regardless of the subsequent favorable facts that might emerge. The public, unfortunately, quickly forgets publicity regarding safety awards (per haps because it expects a business to run its affairs without injuries), but will note in all detail reports of accidents, injuries, fires, explosions, misplaced radioactive sources, tank cars that overflow or leak, or clouds of smoke, fumes, or dusts. Favorable public relations cannot be bought--it must be earned--and a safe operation, properly managed over the years, will greatly assist in earning it. Another major reason for safety activity is in the legal area. An amazing number of laws, codes, edicts, and regulations have been enacted by all levels of government, from the town or city through the county, state, and federal. Some may have specific requirements in clear numerical terms, such as the regulation of the Federal Aviation Agency regarding a certain-wattage lamp in a special red globe atop a water tower or smokestack located a certain distance from an air port runway. Others are less obvious, as the parts per million of Why Safety? 5 various substances permitted in an effluent discharging into a river or a bay (usually a state or local law). Many companies have legal consultants who can cite appropriate laws and the penalties for noncompliance. Directly affecting chemical industry are the state workmen's com pensation laws and the Walsh-Healy Public Contract Act. Workmen's compensation laws have been enacted since 1911 in all fifty states, Puerto Rico, and the District of Columbia. In addition, there exists the Federal Employees' System and the Longshoremen's and Harbor Workers' Systems. These laws differ widely in their con tent and in methods of operation. The recent studies published from the Research Program of the Institute of Industrial Relations, Uni versity of California, have aired both the differences and the inade quacy of the various laws in achieving their original objectives. The present confusion that an injured employee must face when seeking economic recovery from work injuries is a strong argument for accident prevention, though it is seldom mentioned.1,2 The Walsh-Healy Public Contract Act, Health and Safety Standards (41 CFR 50-204) are intended to improve the safety of the industrial environment for plants that have government contracts in amounts over $10,000. These physical control measures, which range from specification of the size of stair treads to the concentration of dusts, vapors, and gases permitted in the air, may be helpful in improving the safety of the physical facilities, but they are only one relatively small step forward, since they neither specify nor encourage any higher safety standards of performance by the employee, and they reward neither employer nor employee for superior or even perfect safety achievement. It is hoped that from the present discussions about these standards will evolve a better program of achieving the stated objective--namely, injury prevention--with more attention directed to the human and less to the physical aspects than reflected by the current regulations. The chemical industry, as reflected by the injury rates reported in Fig. 1.2 by the National Safety Council, is one of the safer industrial groups, and its frequency and severity rates are much more favorable than the average for all industry.3 When we consider the potential hazards in the manufacture of thousands of substances from high ex plosives and rocket propellants to newly synthesized esoteric com pounds whose properties are unknown even to the research chemist who created them, the safety record is outstanding.4 This relatively favorable safety experience did not just happen. As shown in Table 1.1, during forty years the frequency rate in the chem ical industry for all disabling injuries was reduced from 24 to slightly ETC 03034 ETC 03035 Why Safety? 7 TABLE 1.1. Chemical Industry Injury Rates Year 1923 1924 1925 1926 1927 .Vo. of Units 13 30 65 108 143 1928 1929 1930 1931 1932 162 172 211 238 266 1933 1934 1935 1936 1937 245 254 282 305 323 1938 1939 1940 1941 1942 307 417 419 434 475 1943 1944 1945 1946 1947 575 551 567 598 563 1948 1949 1950 1951 1952 569 545 520 573 659 1953 1954 1955 1956 1957 851 900 953 1000 1005 1958 1959 1960 1961 1962 1024 1025 1073 973 974 1963 1056 Fatal .61 .33 .31 .25 .19 Injury Rates Frequency Perm. Temporary All Disab. Partial Total Injuries .55 1.30 .69 .72 .61 23.39 24.50 19.91 17.29 16.38 24.55 26.13 20.91 18.26 17.18 Severity 4780 3070 2710 2280 1900 .23 .64 .18 .68 .17 .88 .20 .72 .23 .65 18.78 16.64 14.45 11.73 9.65 19.65 17.50 15.50 12.65 10.53 2080 1720 1940 1840 1920 .18 .64 .21 .66 .09 .68 .11 .57 .13 .61 9.64 9.43 8.76 9.55 9.49 10.46 10.30 9.53 10.23 10.23 1670 1810 1030 1180 1290 .13 .51 .13 .56 .33 .57 .12 .63 .15 .48 7.29 6.79 8.25, 8.73 9.27 7.93 7.48 9.15 9.48 9.90 1230 1260 2530 1300 1290 .12 .47 .08 .52 .10 .57 .07 .53 .09 .44 9.48 9.64 9.41 9.49 8.33 10.07 10.24 10.08 10.09 8.86 1120 910 1060 860 920 .09 .46 .05 .48 .08 .37 .09 .32 .04 .41 6.96 5.19 5.37 5.07 4.65 7.51 5.72 5.82 5.48 5.10 900 600 760 850 550 .09 .33 .05 .31 .05 .31 .04 .27 .05 .33 4.11 3.76 2.85 3.07 3.17 4.53 4.12 3.77 3.38 3.55 810 570 604 462 536 .06 .26 .05 .22 .06 .25 .03 .26 .06 .24 3.24 3.05 3.40 2.97 3.01 3.56 3.32 3.71 3.26 3.31 552 495 538 392 532 .03 .25 3.04 3.32 341 Average Time Charges (Days) Per Case Perm. Temp. AH Partial Total Injs. 1425 544 821 644 834 14 195 15 117 15 129 17 125 17 111 635 15 106 548 15 98 777 15 125 635 17 146 538 17 182 647 17 159 572 18 176 469 19 108 667 17 115 591 16 126 543 20 155 616 19 169 697 19 276 650 18 137 469 17 131 562 17 112 454 18 89 482 21 105 489 18 85 441 19 104 462 19 119 433 23 106 446 24 131 654 24 155 456 22 108 465 25 179 582 24 138 445 26 163 450 25 137 367 28 151 428 28 155 387 29 149 384 30 145 421 27 120 309 28 161 273 27 103 ii i i; j' i ii i ETC 03036 8 Safety and Accident Prevention in Chemical Operations over 3; at the same time the severity rate was reduced from nearly 4800 to about 550. It is interesting to note that the number of units (plants, laboratories, and companies) reporting increased from 13 to nearly 1000--a reflection of the growing awareness and interest of the role of injury control in efficient operations. A sincere attempt to share ex periences voluntarily, reflecting both favorable and unfavorable opera tion, has given the chemical industry an advantage over many indus tries where the knowledge is simply filed away and kept as classified data.5 This book reflects the spirit of sharing information about accident prevention. We hope this book will serve as a seed crystal to encourage even greater cooperation designed to achieve greater control of acci dents.6' 7 REFERENCES 1. E. F. Cheit, Injury and Recovery in the Course of Employment, Wiley, New York, 1961. 2. E. F. Cheit and M. S. Gordon (Eds.), Occupational Disability and Public Policy, Wiley, New York, 1963. 3. Accident Facts, annual publication, Statistics Department, National Safety Council, 425 N. Michigan Ave., Chicago, 111. 4. "Annual Fire Losses" (including analysis of chemical and allied industry ex perience), published annually in Quarterly of the National Fire Protection Association, 60 Batterymarch St., Boston Mass. 5. B. N. Seear, Safety and the Nation, Proceedings of the National Industrial Safety Conference 1963, Royal Society for the Prevention of Accidents, London, United Kingdom, 1963, pp. 42-53. 6. J. M. Bray, "Industrial Accident Prevention--The Incentive," Safety News, Melbourne, Vic., Australia, July-August 1963, Vol. 34, No. 4, pp. 26-29. 7. Safety and its Significance at Board Level. Cartwright, W. F. Proceedings of the National Industrial Safety Conference 1963, Royal Society for the Preven tion of Accidents, London, United Kingdom, May 1963, pp. 15-27. Who Makes Safety? H. H. Fawcett In addition to being a financial and legal problem, as noted in Chap ter 1, safety (including health and fire prevention) is a very personal problem, and herein lies the all-too-often overlooked secret to accident prevention. Injuries occur to a person, and, regardless of the agency producing the injury (chemical, electrical, mechanical, radiological, or bacteriological), the method by which the agency acted, or the sequence of events, the one common denominator in all injury mathematics is one person--a human being--Homo sapiens. To control injuries, then, we must resist the temptation to write a manual or set of safety rules, issue a statement signed by a corporate official or works manager supporting the safety effort, and then com placently and passively sit back to await the day that injuries stop so the payroll department can mail "lack of work" notices to the medical staff, and plant engineering can convert the dispensary or plant clinic into more productive facilities. Accident prevention is not that simple. If it were, injuries would have largely disappeared from the industrial scene years ago, for many companies, both large and small, have ap proached the problem with the viewpoint that they have established rules, and hence, have solved the problem of accidents for all times. One fundamental fact has been largely overlooked. The very person with the most to lose by injuries--a man--is the weak link in the chain of the safety movement. The above paragraph should be construed in no way as casting doubt on the importance for safety to start at the top of the organization ETC 03038 10 Safety and Accident Prevention in Chemical Operations structure. Unless the chief executive officer, whatever his title, is con vinced that injuries, fires, explosions, and impairment to health of em ployees and the public are not only undesirable but are subversive to the financial health of the company, and hence justify positive aggres sive measures to control or eliminate these losses (which are never completely covered by insurance, no matter how comprehensive the insurance coverage might seem), it is futile to propose or promote acci dent prevention at the lower echelons of management. Furthermore, the chief executive officer must let it be known that he expects the same attention given to control of accidents that he expects in control of sales, budgets, scrap, overtime, absenteeism, and expense accounts; and that he will hold lower management responsible and accountable for adequate control of injuries, fires, explosions, and impairment of health. He expects the accident prevention activities to have more than lip-service or to be more than a gesture. A clear statement must be made, such as the Basic Rule of Responsibility of the United States Navy: "Safety is a command function. Responsibility for the safety of personnel is vested in the commanding officer. Because these safety precautions apply only to usual conditions, commanding officers or others in authority may find it necessary to issue special precautions to their commands to cover local conditions and unusual circumstances. In addition to the posting of appropriate precautions, careful instruc tion and indoctrination of all personnel are necessary to insure effec tive compliance with these precautions." It is usually agreed that a safety policy should exist that offers clear-cut guidance for all members of a company, that expresses for mally the company safety position and its safety program, and that specifies responsibility in accident prevention throughout the company. The concept of organized cooperative safety, currently understood in the United States as organized control and prevention activity, began in 1912, when the National Safety Council was formed at a meeting in Milwaukee. The chemical section of the council was formed in 1916. The Safety Committee of the Manufacturing Chemists' Association held its first meeting in 1925. Individual chemical companies had long before instituted very effective and highly specialized approaches to safety. When the black powder mills were built on the banks of the Brandywine River in 1802, both workers and owners lived near the operations with their families, hence insuring a direct interest in safety for purely personal reasons. However, the fact is that the full impact of the safety movement has yet to be felt--in fact, it may be decades before the concept of accident prevention becomes both an industrial and a household reality. We may never fully achieve the ideal stated Who Makes Safety? 11 by Professor Albert Einstein, while addressing an audience at the California Institute of Technology in 1938: Concern for man himself and his fate must always form the chief interest of all technical endeavor. Never forget this in the midst of your diagrams and equations. This does not suggest that we should be unrealistic in filling our obligations to society, and in achieving economic advantage for our selves and our employers. It does, however, present a moral and ethical guide, without which both the economy, and ultimately our society, will destroy itself, both collectively and individually. As suggested above, policies, edicts, rules, and procedures regarding safety will not prevent injuries by themselves. They must be the blue print or pipeline that carries the vital thoughts to a man. We believe that man--as an individual--is the weak link, in spite of the obvious fact that it is man who has the most to lose by injuries. We have con cluded: 1. Man, as a group or as a type, does not exist, except statistically. He exists only as a single person, one human wholly unique, different, and peculiar. His background, environment, education, drives, am bitions, and outlook establish his individual nature. He is not con stant for more than a few seconds at a time, for he is continually changing his actions, his thoughts, his desires, and his objectives. His biology, as well as his emotions, range far wider than even he realizes. Sweeping generalizations about `'man" will usually fall short when applied to a single person, for he will usually differ considerably from the norm or average. Statistics are useful tools or measuring devices, but the basis of the statistic must never be overlooked. 2. Man is not truly concerned about safety, per se. In the native preconditioned states, man cares little or nothing about the plant safety record or whether it wins an award for safety. He is not always pri marily concerned about living forever or about self-preservation--two ideas frequently advanced as why man should be naturally interested in safety. There is adequate documentation of the fact that some injuries, both on and off the job, doubtlessly are motivated, inspired, or at least closely related to mental pressures that overwhelmed the person for the immediate moment. Each man, regardless of his social or economic station in life, has an Achilles heel, which is his personal mental breaking point, as the Communists have demonstrated with their "brain-washing" techniques, and as a study of suicides will sug gest. Unless the accumulated pressures of life have some vent--and ETC 03040 12 Safety and Accident Prevention in Chemical Operation* the relief may be as simple as talking to a friend, either real or imagi nary (as in The Listener by Taylor Caldwell)--man may be driven to highly irrational conduct which may be misinterpreted as an "acci dent." Doubtlessly the brain fails or "blacks out" at critical moments in industries, and elsewhere mental lapses or other forms of preoccupa tion may explain accidents which "should never have happened because he knew better." 3. Man is vitally concerned with his own self-interests, whatever they may be. The frank question, "What's in it for me?" cannot be ignored or glossed over lightly. Financial reward is only one of many interests, and in appealing to a man in terms of safety, it will be found he, in turn, will accept or reject the safety message in terms of how he relates it to his own objectives and goals (either expressed or subconscious).1 If man thinks something affects him, even indirectly, he will be interested; if he believes he can "profit" by the message he will read or listen; but, if he is convinced that the story is of vital personal concern to his economic welfare, his health, his happiness, his family, or to his ability to achieve his short-range objectives, he will sit at your feet and absorb every word. Note the words thinks, be lieves, and convinced in the previous sentence. These three words rep resent crude measures of the degree of safety acceptance. If we are to achieve accident control, it must be by inspiring or diffusing into every man on the payroll--from the chief executive officer to the humble but vitally important night watchman, the undisputed fact that safety is vital to his personal interests, and that it will return him more in benefits than he invests in time, money, and thought. Safety is a blue-chip investment for an individual as well as for a company. 4. Safety must become a philosophy of life for each person, and must ultimately precondition each action, even in the subconscious state. As a popular slogan goes, "Knowing is not enough." Safety is not an esoteric subject, brewed up by do-gooders in unrealistic batches;* and spread like an unwelcomed plague to unconvinced man. Rather, it is the distilled essence of the lessons learned from thousands of deaths, from millions of injuries, and from billions of manhours of exposure.2 If, as Abraham Lincoln once said, it is disgraceful to fall over the same log twice, it is even more disgraceful to permit accidents to recur simply because we have not instilled the potion into the eyes at the right instant to permit man to see properly. Puck said, "What fools these mortals be," but mortal man can act wisely as well as foolishly, if he is given both the knowledge and motivation he needs. Man, the only product of creation who can think creatively and mod ulate to conform to his moral and social orientation, must now be Who Makes Safety? 13 encouraged to actually follow safety rules because he believes in them, and respect standard operating procedures because he knows they were written for his best interests. He must become his brother's keeper in matters of safety, and sincerely believe, "I'm for safety because it is good for me." The me is used in the personal sense, but also implies the wide meaning of me, inasmuch as a man's contribution to his employer, and hence to society, is also a vital part of his self-interest. Perhaps by another generation, we will have achieved that infusion into the minds and hearts of our employees--from top to bottom in the organization, and eventually achieve the goal of "Profitable Production Without Accidents." Then, safety, while not first, will have achieved its proper recognition as a dynamic force for progress, both for the individual, his employer, and society. REFERENCES 1. Prime III: Safety for the Supervisor, programmed instruction course spe cifically designed for supervisors, American Management Association, 135 West 50th St., New York, N .Y. 2. "The Fundamentals of Accident Prevention," Bull. No. 247, Safety in Industry, Bureau of Labor Standards, U.S. Dept, of Labor, Washington, D. C. I' i i ! i ETC 03042 Organized Labor's Interest in Safety Elwood D. Swisher "The conditions were unquestionably bad. In 1906, the year of the `Pittsburgh Survey,' there were 526 industrial fatalities in Allegheny County, Pennsylvania. A trainman had one chance in 127 of death by accident in any given year. There was also plenty of outraged pub lic opinion.'' I quote briefly from Chrystal Eastman, Secretary of the New York Commission, on employers liability and causes of industrial accidents. We can set up a good argument for the other side of this picture. It is still true that at the time of the enactment of the first compensation law in 1911 in New Jersey, one-fifth of the litigation at the state court was concerned with liability for damages as a result of industrial in juries. Today countless hours are spent before State Industrial Commissions or Workmen's Compensation Hearings on behalf of injured workers or the widows of those who died as a result of accidents occurring on the job. These hearings are further complicated by the increasing number of occupational diseases arising out of the increased number of toxic materials being used by industry today, and the worker is hampered because many states have failed to keep pace and update their lists of occupational diseases. The first principle of any union is the general welfare of its mem14 ETC 03043 Organized Labor'* Interest in Safety IS bers. A paragraph from the Preamble of the Oil, Chemical and Atomic Workers International Union Constitution states: It shall be the object of this Union to establish and maintain collective bar gaining for the benefit of the workers within its jurisdiction and to conduct a neverceasing effort to secure just compensation for the Workers, reasonable hours of toil, and working conditions conducive to safety, good health and full enjoyment of life. In this fast moving age, concern over safe working conditions is just as acute, if not more so, than at the turn of the century. At this point, tribute should be given to the many, many companies, who with a sense of deep consciousness, carry on well-rounded safety programs, both on the job and off the job. It is to their credit that we have fewer injuries and deaths than we would have otherwise. On the other hand, we still have too many companies who are callous in their concern for the safety of their workers. Generally these latter interests are in the forefront at the state legislature fighting any improvement in their state safety laws or codes, and opposing improvements in workmen's compensation. They are the ones who help take the public's mind off good safe practices by stressing the fact of payments to injured workers under workmen's compensation. They are even opposed to acceptance of the American Standards Association safety recommendations, which are recognized as a minimum only, to be included in a state safety law or code. It is for these reasons that unions are finding it ever necessary to continue to strive for improved health and safety programs. A survey in 1956 by the State of California titled "Think of the Dependents" starts by saying: You cannot measure the results of work injuries and deaths in dollars and cents only. You cannot measure the results in loss of production only, either. All the statistics in the world are of little consolation to a child who has lost his father, or a wife, who has lost her husband. California workers who died from on the job injuries in 1956, left 1781 de pendents as follows: 966 Children, 651 Widows, and 164 other dependents. Of California workers who died from on the job injuries in 1956, nine out of ten had dependents, eight out of ten had wives, five out of ten had children under eighteen years old. Of the 651 widows, 382 had children, 259 had two or more children, 131 had three or more children and 59 had four or more children. You might ask, "What steps are the unions taking to promote safety?" ETC 03044 16 Safety and Accident Prevention in Chemical Operations The AFL-CIO Standing Committee on Occupational Safety and Health has conducted a series of 120-hour courses at their head quarters in Washington, D. C. for international union leadership. They have also conducted courses at an area level to get a broader partici pation of local union leadership to improve safety education. International unions and state and local central bodies are con tinuously holding summer schools devoted entirely to on-the-job and off-the-job safety. The AFL-CIO Standing Committee continues to put out pamphlets urging international unions and local unions to step up their activities in safety programs. This is augmented by international as well as local union participa tion in the Labor Conference of the National Safety Council.1 The efforts of the Labor Conference of the National Safety Council can best be summed up in the safety policy and program recommended for adoption by international and local union organizations. Only the Resolve itself is quoted: THEREFORE BE IT RESOLVED, that, each International Union establish a Safety Department with full time personnel. It is further recommended that the Safety Department be an independent department within the structure of each International Union subordinate to no other department, but rather a direct responsibility of a designated International Officer of each International Union. that, each International who has not already done so, establish a policy of requiring a Safety Committee as a mandatory committee for each and every Local Union under their affiliation with provision for same in their respective constitutions. that, all International Unions be urged to negotiate Safety and Occupa tional Health clauses in their contracts and seek to implement such clauses through joint labor-management committees. that, each International Union urge their affiliated Local Unions to take out membership in the Labor Division of the National Safety Council. that, each International Union establish a library of Safety films, pamph lets and posters as part of their Occupational Health and Safety Depart ment and provide for the education of its members through the media of Region conferences, Summer Schools and any other means at their disposal. RECOMMENDATIONS FOR LOCAL UNION SAFETY AND OCCUPATIONAL HEALTH COMMITTEES. 1. that, each Local Union select a committee to suit their own needs; depend ing on plant size. 2. In the case of joint labor-management committees, equal representation from both labor and management, with the union members to be selected by their local unions. Organised Labor's Interest in Safety 17 3. that, safety Committee members be allowed to participate in plant safety inspections along with management. 4. that, they shall have the right to investigate plant accidents and make recommendations on any and all existing hazards. 5. that, the International Unions' Safety and Occupational Health personnel shall have the right of entry into plants for the purpose of investigation of existing hazards. 6. that, the committee be able to study all accidents and health records and recommendations of state factory inspectors. 7. that, Local Union Safety and Occupational Health Committees conduct an intensive educational program amongst their membership utilizing the media of press and the facilities of their respective International Union Safety Departments. 8. Because of the inadequacy of State and Federal Safety and Occupational Health Laws, that all future contracts contain safety clauses that require that American Standards Association Safety Codes be used as minimum requirements for Safety and Occupational Health. One of the biggest problems in a good safety program is obtaining the worker's sense of responsibility to obtain the habit of good safety rather than the habit of poor safety. This, often times, becomes a most arduous task because of the difference in principle practiced by various companies in their safety programs. All too often we hear workers say, "Our company's motto is safety first, so long as it doesn't interfere with production." This expression becomes understandable when you find a group of workers representing various companies gathered together in a safety school during open discussion. Expressions, such as the above, become meaningful and under standable as the reasons come to light. Simply, it boils down to this: Company A and others who fall into this category, have acceptable and well balanced safety programs and a qualified staff of safety engineers. However, the safety engineer has only an advisory capacity. If a worker or workers complain that a job is unsafe and the safety engineer shares the workers' opinion he can only recommend that the job be discontinued until corrected, but the production supervisor makes the final decision and says, "production must go on, the job will be corrected on another shift." This then starts the doubt in the worker's mind. On the other hand, Company B and other companies who fall in this category, have an entirely different approach. There may be no difference in the safety program or the quality of the safety engineering staff; however, when a worker complains of an unsafe working condition and the safety engineer is in agreement, he has the authority under this system to shut down the job immediately and ETC 03046 18 Safety and Accident Prevention in Chemical Operations effectuate remedial action. This gives the worker a lift and a greater degree of confidence. We can see from the above the frustration of instructors conducting safety schools in industrial unions such as the Oil, Chemical and Atomic Workers International Union. There are other irksome inci dents that contribute to poor safety habits. There is the overzealous foreman (who probably never developed safety habits) who jumps in with a flurry to demonstrate to a worker how he possibly could speed up his job. This is impressive, especially to a new worker who does not stop to think that the foreman is not going to perform this job 8 hr a day, and the worker later comes up with an injury or at worst, his widow's grief. Then we have the same type of foreman, who without safety goggles, mask, or other protective clothing, where called for, jumps into a dusty, toxic or otherwise dangerous area, and for a few brief moments sets the world on fire in a demonstration to the worker or workers on how the job should be handled. The foreman knows he is not going to be working in and around this dust for the full eight hours, day in and day out. In the atomic energy field we have the same type of foreman, who wipes up his fingers full of alpha contaminated dust and eats it off his fingers in order to prove to the workers that the area in which they are working is not dangerously radioactive and, therefore, they shouldn't be concerned if the monitoring of the area has become haphazard. We wonder what this individual would do if he were made to do this 8 hr a day, 40 hr a week, and 50 weeks out of the year. But we would agree that his attitude would change. It is difficult to understand such individuals as foremen, and there fore supposedly leaders of men. We can only assume that they are bucking for higher jobs or have developed such illusions of grandeur that they think they are paying for the operation of the plant out of their own pockets. We could go on and on and on with experiences such as above, and yet these are just examples of what is being practiced day in and day out throughout the jurisdiction of this international union. One growing habit that is beginning to give nightmares to safety conscious people as it becomes more widespread is the use of poisonous solvents and other toxic liquids in plants. It is true they come into the plant in bulk form, properly labeled as to ingredients that are dangerously poisonous. But then they are dipped out or tapped out in unmarked containers and carried to that part of the operation where Organized Labor' Interest in Safety 19 they are to be used. What happens when left unattended and workers not familiar with that particular job assignment come upon the scene with dirty and greasy hands looking for a solution to wash in? The frequency and severity rate of injuries in the chemical and allied industries can and must be improved. That which, at present, is a fair to good rate, can with cooperation of all parties concerned become an excellent rate. This can become a reality by the industry and the union both accepting their full responsibility and recognizing that it is a mutual problem and not one sided. In spite of the sagacious eighteenth-century thinking that still prevails in some sections of the chemical and allied industry in this country, one fact remains--unions are here to stay--and the welfare and safety of their members are paramount in their thinking and their actions. To prove how effective a joint labor-management safety program can be, let's look at some of the experiences of the Pacific Coast Association of Pulp and Paper Manufacturers, the United Papermaker and Paperworkers International Union, and the International Brotherhood of Pulp, Sulphite and Paper Mill Workers working jointly in an industry classified as hazardous by definition of state compensation laws. For the full year of 1963, their frequency rate was 4.77, as compared to the survey of the Bureau of Labor Standards for the first 9 months of 1963 showing a frequency rate of 10.0. This joint labor-management program became effective in 1945 at which time the frequency rate was 38.99--a drop of 88% over the last 18 years! It is also interesting to note that there were no fatalities for the years of 1962 and 1963 and no total permanent disability cases for the year 1963. The Pacific Coast Association of Pulp and Paper Manufacturers through their joint safety program figure that 22,763 disabling injuries were prevented during the year of 1963. They arrive at this theoretical figure on the basis of 1000 disabling injuries for 32 million manhours worked in 1945 as compared to 240 disabling injuries for close to 60 million manhours worked in 1963. What has become a reality in one industry through joint labormanagement efforts can also become a reality in the chemical and allied industry if we accept modern day thinking where safety is concerned. There is no valid reason why labor and management cannot unite in discharging their common responsibilities for safety and health : j ; |- , ; ; ! t I J j ] i j ' ETC 03048 ETC 03049 4 Chemical Hazards and Worker Safety: Relationship to the Interests of Governmental Labor Officials Stanley F. Spence All industry has changed during the past few decades, but the chemical ' industry has changed more than most. ' In New Jersey we have a close-up view of the galloping advance in the chemical industry. Latest official data show that the chemical industry ranks first in that state in value added by manufacture; and : by the same index New Jersey is the leading state in the country. An; nual sales of chemicals in the state are estimated at $3.5 billion a j year--about one-tenth of all United States chemical sales in 1963. i Today accumulative value added by chemical manufacture in New Jersey exceeds $1.7 billion, nearly 60% higher than any other industry ; in the state. I Some industries start with a number of raw and semi-finished matej rials to make a single product, like the automobile.Others take a sin gle raw material like petroleum and make a number of endproducts j from it. But the basic raw material of the chemical industry is the j molecule. The tremendous scope thus provided enables the industry to i build the many thousands of distinct chemical entities of which more | than 10 thousand are commercially available. 1 This industry has one of the highest capital investments per em| ployee, and it must place great dependence upon the ability and the i ; 21 ETC 03050 22 Safety and Accident Prevention in Chemical Operations character of the employee. This chapter will cover the principal el ements of the safety and loss-prevention problem and the control pro cedures which apply thereto in the chemical manufacturing industry itself, and then proceed on a logical route through the safety prob lems attending the conveyance of the chemical products to the user, and, lastly, the subject of the safe handling of chemical products by the customers of the chemical manufacturing industry. Each of these areas of consideration has its own unique problems in chemical safety, even though the producer's sulfuric acid, as an example, is the same sulfuric acid in the tank truck of the motor carrier as it is in the customer's storage tank. The principal problem in chemical safety in the hands of the carrier or the ultimate user is one of insuring that the managements of these entities, and through them their employees, fully understand and follow those procedures which accident-free handling and storage demand. The title page of every Chemical Safety Data published by the Manufacturing Chemists' Association bears this statement: Chemicals in any form can be safety stored, handled or used if the physical, chemical and hazardous properties are fully understood and the necessary precautions, including the use of proper safeguards and personal protective equipment, are observed. Thus, it can be seen that the basic method of attacking the chemical safety problem in each of these three areas to be discussed--manufac turing, transportation, and use--contains the same principal elements: education and communication. Perhaps the most important reason the chemical industry has pro gressed so far in safety is that it had to. It naturally has more com plex safety problems than do most other industries. Hazards are not as naturally recognizable to the worker as are the hazards of a machine shop, for example. The new worker must be carefully educated in the characteristics of the materials with which he is working, and he must be given diligent training and follow-up by his supervisor. Since the materials he controls are usually in closed systems he must fully understand the changes going on in the process, and he must be able to interpret the messages provided by his instruments. He must always be influenced by the realization that any infraction of safe operating procedure on his part may produce an accident having in jurious consequence not only to him, but also to his fellow workers. It is this constant awareness on the part of the employer and the employee alike that has produced for the chemical industry an enviable safety performance. The record of the chemical industry in work Chemical Hazards and Worker Safety 23 injuries is illuminating, and a few of the salient facts are worth citing at this point. The National Safety Council reports that in 1963 the chemical industry experienced a frequency of 3.32 disabling injuries per million manhours work, as against 6.12 for all industries. The chemical industry frequency was 45.7% lower. The authority cites the chemical industry severity as 341 days lost or charged per million manhours worked, against 682 for all industries. The chemical in dustry severity was 50% lower than the all-industry rate. Now, what has produced this kind of safety performance? It was mentioned before that it resulted from an awareness on the part of employer and employee. But this awareness has its basis in a philosophy of conduct. This philosophy, in a nut shell, is this: The employer should provide a safe working environment, instructions on the hazards involved, and the safe way of doing the job. He should make available to employ ees those special protective devices or items of apparel required by injury exposures unique to their jobs, and should encourage their use by the employees. He should provide adequate supervision. It is the employee's responsibility to fully understand the instructions ap plying to the safe conduct of his work and to carry them out without deviation. Because the safety efforts in the chemical industry are diligently oriented to the avoidance of what might be called "chemical type" accidents, a relatively small percentage of this category are experi enced. The American Cyanamid Company's accident history might be of interest in this respect. Analysis of the January 1, 1959 to January 1, 1963 disabling injuries divulged the fact that only 8.9% were of the chemical type. In common with all other industries the 1 greatest proportion occurred in the classifications: falls, caught-between, and struck against or struck by. The lost-time charges against the accidents in the four-year period were also significant: only 20.8% of the total lost days resulted from injuries of the chemical type. The foregoing facts were cited to demonstrate that special effort has been expended in the direction of eliminating accidents arising out of chemical manufacturing operations since such accidents obviously can tend to be of a particularly serious and extensive nature. They can involve fires, explosions, and exposure to toxic and corrosive chem icals. They can be of the multiple-injury type, for the unsafe act of any individual can cause an accident hurting others and causing ex tensive damage, as mentioned before. All this does not mean, how ever, that we can permit giving the light touch to accident sources outside of chemicals. Our problem in controlling the usual run of industrial accidents is about the same as that of anyone else. ETC 03052 24 Safety and Occident Prevention in Chemical Operations The procedure followed at Cyanamid in producing a safe operating or research unit is not unlike that used by other responsible chemical manufacturing concerns, and perhaps a sketch will be of interest. The design for built-in safety starts in the laboratory or "glassware" stage and continues through to the manning and operation of the production facility. Briefly it is as follows: 1. The primary responsibility for obtaining necessary process informa tion, including all safety aspects, lies with laboratory and pilot plant group leaders and their technical people. This responsibility is an integral part of their jobs and cannot be delegated elsewhere. The responsibility begins as soon as work is started on the process, whether it be on laboratory, prepilot, or pilot plant scale. 2. When transferring a product from pilot plant to a production unit is contemplated, review of process data is started with production, engineering, and safety people as early as possible before transfer. A detailed check list is used to insure that no areas are overlooked. This check list includes as primary items: Product description Chemistry of process Characteristics of raw materials Process flow sheets Equipment and instrumentation Chemical, equipment, and health hazards Operating procedures, including emergency procedures for mal functions Analysis and process controls Final product characteristics: Stability, toxicity, flammability, and other essential data It can be seen from the above list and generally from a considera tion of this overall procedure, that it is quite impossible to sep arate the "safety" from the "operation." 3. The plant design must incorporate the company's safety standards for methods and equipments, and all governmental laws and or dinances applying. As the design develops, frequent consultation is held between representatives of engineering, operations, and safety, to insure that the projected unit will be safely operable and safely maintainable. 4. The unit is continually checked during construction to make sure that the safety, fire protection, and operating features agreed upon are properly installed. FTr. 03053 Chemical Hazard and Worker Safety 25 5. The cadre composed of operating, technical, maintenance, and safety personnel who are to man the plant are thoroughly schooled in the process through direct instruction, review of the flow sheets, in spection of the physical plant as it develops, and operation of similar equipment on other operating locations of the company. 6. Before acceptance of the plant from the contractor, a final survey is made for safe operability and maintainability, and the necessary corrections are made. 7. The unit is staffed, personnel conducted through necessary training programs, and all procedures established for safety and loss-preven tion as an operating unit. Probably it has been observed during the course of this chapter that I have emphasized and re-emphasized the dependence that must be placed upon the individual. He should be selected for his chemical industry job with a view to his basic capability to handle that job. He should be properly trained. He should be instructed in such a way that he will understand not only what he should do, and why he should do it in the prescribed way, but also what will happen if he does not follow the given procedure. We are, at this point, directly at the heart of safety in operation--the human being. His own safety and often the safety of others depends upon this individual. Undoubt edly you have heard many times that the philosophy of safety is chang ing, that in the older days of the profession all of the emphasis was on the engineering or physical part of the problem, that now the en gineering aspect no longer exists as a principal angle of attack, and that the "human element" is now being recognized as the primary objective. A veteran of 30 years in this profession can tell you that such observations are completely wrong, because the human being always has been the primary consideration in accident control. It will always be so. Anything that is done in the way of physical revision is done as a secondary defense. Machine guards, handrails, floor opening protec tion, mechanical nonrepeat devices on presses, and so on, are installed with the foreknowledge that our human being, trained though he might be, is still subject to all of the frailties which befall humans. He oc casionally is forgetful, is ill, is worried, and is preoccupied. WThen he is in such a vulnerable condition, whether it be for just a moment or for a longer period, we must do our best to keep him from accident by "pulling the teeth" of the physical hazard. And so it should be emphasized that as long as there has been an industrial safety effort, men competent enough to call themselves Safety Engineers have eval- 26 Safety and Accident Prevention in Chemical Operation* uated each problem in the light of its own requirements and have planned their corrective actions on the basis of an appropriate balance between the engineering and the humanities. One of the most important elements in the conduct of industrial safety is the investigation by supervision of significant accidents, and the instigation of prompt corrective action. Usually such accidents in the chemical industry, with their resultant injuries or damage, are found to have been caused by a combination of physical and human faults, and the preventive measures which are taken of course contem plate this same combination. To illustrate the point, there is quoted below from Case Histories of Accidents in the Chemical Industry (a publication of Manufacturing Chemists Association) Case History No. 477: Description: Employees were attempting to install a new gasket in the line leading from the top of a titanium reducer. Apparently they neglected to vent inert gas pressure from equipment before removing bolts from flange. When flange was loosened, the twelve pound pressure in the equipment blew lower chlorides of titanium out to the air where they fired spontaneously and burned two employees on arms, chests, legs. Their safety glasses prevented eye injuries. Cause: Failure to vent reactor pressure; inadequate protective clothing. Preventive measures: In addition to proper venting of pressure, flange will be loosened on side away from body before all bolts are removed. Employees opening a reactor where lower chlorides might be present will wear asbestos hood, long coat and gloves. Occasionally reference has been made to the Manufacturing Chem ists' Association and a brief explanation of what it is, and how it func tions in the area of chemical safety and fire protection might be help ful. It is a nonprofit membership corporation (New York), was founded in 1872, and is the oldest chemical trade association in the Western Hemisphere. The Association includes about 200 member companies in the United States and Canada, representing more than 90% of the productive capacity of the industry. One of the active committees of MCA is the Safety and Fire Pro tection Committee. It is composed of the heads of Safety and Fire Protection of member companies, and of diversified chemical man ufacturing interests. The committee acts as a clearing house for the exchange of information on safety and fire protection within the in dustry, and for the carriers and users of chemicals. It also extends its efforts in the direction of safety education for schools and colleges, through its publications. The Safety and Fire Protection Committee also has conducted safety workshops in various parts of the United States and Canada. Out of the many billions of manhours of chemical operating expe rience of the member companies of MCA and the pooling of their knowledge in accident prevention, a number of informative works have been produced and published. 1. Chemical Safety Data Sheets: These are devoted to a full descrip tion of the known characteristics and properties of each subject chemical. Chemical subjects for Safety Data Sheet publication are selected on the basis of hazard and broadness of use in industry. In addition to an account of the properties of the given chemical, they contain all of the principal information on safety which the transporter or the user might need. Among the areas dealt with are: properties, hazards, engineering control of hazards, employee's safety, fire fighting, handling and storage, tank and equipment clean ing and repairs, waste disposal, medical management, and first aid. 2. Safety Guides: These cover safety procedures intended to be help ful to the manufacturer and user of chemicals. They are designed in such a way as to promote management stimulation and action, and at the same time to provide practical guidance to the individual who is directly concerned with the execution of the subject. Ex amples are: Health Factors in Safe Handling of Chemicals, Entering Tanks and Other Enclosed Spaces, and Disposal of Hazardous Waste. 3. Accident Case Histories: Newly available is a publication entitled: Case Histories of Accidents in the Chemical Industry. This is a cross-indexed volume of significant chemical industry accidents, including fires and explosions, reported by member firms of MCA during the past several years. Each case write-up is concisely pre sented, and is segmented according to description, cause, and pre ventive measures. 4. Guide for Safety in the Chemical Laboratory: This manual, pre pared through the cooperative effort of member companies, is oriented toward the observance of safe techniques, procedures, and design of the large or small chemical laboratory. It has found its way to the reference book shelves of industrial laboratories, high schools, and libraries around the world. 5. Color-Sound Film: Safety in the Chemical Laboratory: This film is directed primarily to the level of the university chemistry under graduate, but loses none of its educational value in use by industrial laboratories or among university post-graduate workers. 03056 etc 28 Safety and Accident Preeention in Chemical Operations There are many other activities and publications of the Manufac turing Chemists' Association which directly or indirectly serve the interest of safety to the public, to industry, and to transportation, and which undoubtedly come within the purview of your concern. To name a few, there are the subjects of air and water pollution abatement, chemical packaging, traffic and tank vehicles, education activities, medical, labels, and precautionary information. The last may be of particular interest since it is directed toward the important effort of conveying essential information on identification, hazard, and precautions, to all who may in any way come into contact with chemical containers, be it in processing, transportation, storage, or use. The scope and limitations of the precautionary labeling effort are well defined in the "Introduction" to the Manufacturing Chemists' Association Manual L-l: Guide to Precautionary Labeling of Haz ardous Chemicals. It is quoted in part: Many products present no hazard in normal handling and storage. For these products, no precautionary statements are necessary on the label. The development of new chemical products, and the introduction of chemical processes into ever-widening fields, has accentuated the need for furnishing appropriate information in those cases where there are hazards requiring special precautions. Precautionary information should, so far as is practicable, reach every person using, handling, or storing hazardous substances. The most practical means of disseminating this information appears to be by precautionary labels, affixed to containers of hazardous substances, bear ing appropriate precautionary statements expressed as simply and briefly as possible. Such label information, however, cannot take the place of the edu cation of personnel regarding product hazards and the use of safety clothing and equipment. This education is, and must remain, the direct responsibility of their employers. We are now bridging over into the area of the transporter and the user of chemicals. In the transportation phase, particularly, there is encountered the problem of chemical exposures to persons who know nothing about chemicals, their characteristics, hazards, or safety meas ures which should be taken under given circumstances. These persons are largely composed of the carrier's employees, truck operators, rail road operating personnel, in-transit warehouse employees, and the general public who may be exposed at the time of chemical vehicle ac cident or in some other manner. The chemical industry recognizes a moral responsibility to do its best to insure that this segment of the population will not be harmed by those of its products which are hazardous. Just as our chemical industry workers are instructed in the hazards and the safe handling of our products, so should the transportation employees be instructed. This does not mean, of course, that all railroad operating per sonnel should be given a course in chemical safety, but it does mean this: railroad employees and supervisors who may encounter an accident exposing them to flammable or harmful chemicals, should receive basic instructions, and drivers of motor tank transports should be similarly instructed. The shipper can help them much in this regard. The industry does its best to furnish to its carriers full information on the unique properties of, and safe procedures relative to, the products whose characteristics require special knowledge. This may not always be on an individual product basis, for o-enerally it might best be communicated on the basis of principal classifica tions, somew'hat as follows: Flammability--low vapor pressure (example, acetone) Flammability--high vapor pressure (example, LPG) Chemical Reactivity Radioactivity Corrosivity It is the carriers' responsibility to see that their personnel know and observe the precautions and safety procedures communicated to them. In the shipping of corrosive cargoes such as acid and caustic, in tank trucks, we find that we must give special attention to the operators of contract and common carrier trucks. While these drivers are not our employees, we do have a moral responsibility to see that they are familiar with the hazardous properties of the products, that they fully understand their equipment and how to make safe deliveries, and that they have and use the necessary per sonal protective equipment. This requires constant surveillance. On more than one occasion the management of a Cyanamid plant has sent a cargo tank driver back home with his truck because he failed to observe necessary safety precautions or use prescribed personal protective equipment. This can hurt, if the plant desperately needs the delivery, but if it must be done as a last resort, then it must be done. It is the only way to protect the uncooperative outside driver. In shipping hazardous ladings by truck, owned or hired, we normally affix a special tag to the outlet connection. This tag does not conflict in any way with ICC regulations. It provides the name of the product and gives precautionary instructions. We are all vitally concerned with the subject of the transporta tion of extra-hazardous materials, because of the catastrophic ac cidents which can, and have been, produced. Planning against injuries and losses arising out of such occurrences is a broader and a more detailed problem than is the safety education of a truck driver or a railroad man in the limited interests of his own personal safety. The large-scale transportation accidents such as the Roseburg, Oregon explosion of August 7, 1959 (involving an improperly parked truck ETC 03058 30 Safety and Accident Prevention in Chemical Operation* containing 2 tons of dynamite and 4% tons of a blasting agent), and the Norwich, Connecticut explosion in the spring of 1962 (involving a truck carrying over 38 thousand pounds of peroxides plus 10 drums of red label flammable liquids) impress upon us that further preventive measures must be taken in the interest of public safety. In the plan ning of such measures, thought should be given to the following con siderations: 1. Extra-hazardous materials in transportation should be routed to avoid densely populated areas. 2. Explicit and conspicuous markings should be on the exterior of the truck to define the hazard. 3. Safety regulations covering highway vehicle transportation of hazardous chemicals should apply to intra-state transportation to the full extent it applies to inter-state transportation. Another important aspect of safety in the transportation of hazard ous materials is the emergency action which should be taken in the event of accident. Procedures should be established to cover emer gency situations arising out of transportation accidents, where the ladings involved are of a high degree of hazard in themselves, such as class A poisons; where release of the ladings to the surrounding area may be of such high concentration as to have a serious effect upon the health of persons; or where explosives or unusually reactive chemicals are concerned. Some of these procedures may be informal, but still very effective; some may require considerable detail. Under any circumstances, they should be devised to produce these results: 1. To protect the public. 2. To reduce the damage to property. 3. To limit the effect of the immediate incident by guarding against its extension or the occurrence of secondary accidents. 4. To provide competent coordination at the site. 5. To provide to the press, radio, and television, factual data on the occurrence, avoiding speculation and imagination. 6. To provide immediate notification to the shipper and to the authorities having jurisdiction. It is the responsibility of the shipper to formulate the emergency procedures, and to acquaint all who are concerned with them regarding their responsibilities. It is the responsibility of the carrier to immediately notify the shipper and the authority having jurisdiction, in order that the emer gency procedures can be set in motion. An example of very effective Chemical Hazards and Worker Safety 31 and informal emergency procedures is presented by the chlorine industry. The excellent and swift assistance by participants in this mutual aid program--manufacturers of chlorine and users alike-- has served the public and industry well. An example of a detailed, though uncomplicated, transportation emergency procedure is provided by the bulk hydrocyanic acid industry, which brings into play the coordinated action of competent emergency crews, plant management, and local authorities. In this chapter the highlights of safety in the manufacture of chemicals and in their transportation have been discussed. We come now to the user. Every purchaser of chemical products should ob serve the same precaution before he purchases them as do most re sponsible chemical manufacturers when they buy chemicals from the outside. Yes--most chemical manufacturers are, themselves, purchasers of chemical raw materials and intermediates from other concerns. The procedure may be simple, as in a small unit, or it may be detailed (though we hope not complicated) in the case of a large user of many different chemicals. Under any circumstances, the pro cedure would require that, before a chemical is purchased in quantity: 1. There would be obtained from the supplier full knowledge of the properties and characteristics of the product, and the manu facturer's recommendations on safety in storage, handling, and use. 2. Where necessary, additional data, would be obtained from other authoritative sources, such as the MCA Chemical Safety Data Sheets. 3. Those responsible for insuring the safety of operations--generally production, technical, and safety--would satisfy themselves that the product can be stored and used safely under their circum stances, and only then would they give approval to its purchase. 4. Any special handling and storage facilities and equipment re quired by the nature of the product would be installed. 5. All personnel concerned would be fully educated in the proce dures and equipment required for the safe storage, handling, and use of the product. It is distressing to chemical safety men that so many users of chemicals do not take the trouble to learn the simple essentials cover ing the properties of the materials as far as stability, flammability, and other hazard characteristics are concerned. The proper use of chemicals requires more than a knowledge of what they will do in the course of producing a new end product, or how they will behave in performing a given end function. It requires an acquisition and ETC 03060 32 Safety and Accident Prevention in Chemical Operations application of all knowledge of the chemical's behavior in the cir. cuinstances under which it is to be stored, repackaged, and mixed in a given formulation, or used as a reactant in a consequent chemical process. Recently an urban manufacturer of electronic parts exemplified this lack of knowledge. He used nitric acid and muriatic acid in a part of the process. The tanks were in a subterranean cell under the building, the fill lines extending from fittings in the outside sidewalk down underneath the building, and finally connecting into the tanks A tank truck of nitric acid was delivered to the plant and the driver as was proper, checked at the reception office to obtain instructions for making his connections. The customer's authorized representative went below, checked the outage on the nitric acid tank, then came up to the street and told the truck driver exactly where to make his connection. He made the connection to the designated fitting, and started the delivery of nitric acid to the underground storage facility. In the meantime, as was customary, a sample of the nitric acid was taken for the customer's assay. As the acid was being `'blown" to the underground tank the customer's representative chatted with the cargo tank driver. After a short time he went below to "see how things were going." But he came up to the street much faster than he went down, for he was pursued by billowing clouds of various-colored fumes. He had instructed the driver to make the connection to the wrong fitting, and the nitric acid, instead of going into the nitric acid tank, had been flowing into the muriatic acid tanks! The street and immediate neighborhood became filled with acidic fumes and mists. When assistance was offered to the manager of the plant by a chemi cal safety engineer employed by a local firm, neither the plant man ager nor his chief chemist could explain what kind of tank facilities or connections were in the underground storage cell! Tremendous damage can be done through ignorance of proper storage and hand ling of ordinary chemicals. This chapter has covered the accident situation in chemical manu facturing, transportation, and usage. Now, what can governmental labor officials do about all this? I submit a few observations and suggestions: 1. Field consultation: It would be well to train consultants rep resenting the state Departments of Labor to study and evaluate man agement's ability to conduct its operations safely. This ability is re flected by attitude; by the systems and procedures management has Chemical Hazards and Worker Safety 33 established (and follows) in the interest of safety; by the complete ness of operating instructions and the adherence to them by operating personnel; by the safety inspection and preventive maintenance program followed; by the method used in training personnel; by plant cleanliness and layout; and by the safety record itself. The con sultant might then guide management in strengthening the weak spots divulged as a result of the appraisal. 2. Labor officials might find it advantageous to make a careful survey of chemical industry personnel to find out who the top specialists are in given subjects. These are the individuals who might be called upon for unofficial expert counsel in given situations. This is a "digging" job, but the industry safety supervisors should be able to help find out who these people are. 3. Review existing governmental codes to make sure they are realistic, practical, and adequate, and revise them as necessary. In dustry's assistance can be counted upon. 4. Fashion government codes as performance codes, rather than cutand-dried standards and specifications. This is the way such codes or standards must be fashioned even in our own privately owned multiplant companies, since we have many different situations in as many different plants. Consider, then, how much greater the prob lem becomes in a state, or in the nation! As a simple example, Cyanamid's basic safety requirement for tank car access platforms is that "provision shall be made for giving the employee safe access to the dome of the car, protecting him while he is performing his operations there, and returning him safely to his starting point." Our stairway standard supports this in part by providing guide lines for stairway pitch, tread, and riser limits, and other details. In other words, the performance is what counts; how it is produced should not be of important concern to the regulatory body. 5. The history of industrial injury incidence has shown that the smaller firms have the highest injury frequencies. This undoubtedly results from the fact that being small, such firms do not have the staff assistance which large companies often have. Thus, they lack safety, medical, and other important counsel. The chemical industry and the governmental labor officials should make a special effort to reach these smaller firms and to aid them in safety guidance, through their trade associations. 6. It is suggested that governmental labor officials enlist the full participation of industry specialists in the development of safety codes. ETC 03063 5 Safety Aspects of Site Selection, Plant Layout, and Unit Plot Planning D. M. Liston 1 5.1. INTRODUCTION In this chapter, we are concerned with the problems of relative physical locations of facilities. There is the problem of locating the plant relative to its surroundings and the problem of locating com ponents of the plant relative to each other. If we consider these problems, starting with the most general aspects and working toward specific details, we will pass through four recognized phases: location, site selection, plant layout, and unit plot planning. First, let us consider location. Given one proposed chemical plant and one world, the problem is where to locate said plant on said world. This is what we refer to as the location study. Obviously, the major considerations in this phase are economic ones. Thoughts about safety have little to contribute here. Before the threat of atomic war, we might say there were no safety considerations in this phase. Today we might deliberate at some length on steering clear of possible atomic blast or fallout. However, such deliberations will not be subject matter for this chapter. Of course, we cannot simply forget such factors as high wind velocities, earthquakes, snow loads, and frequency of electrical storms. But, as far as location of the plant is concerned, these factors, too, become submerged in the economics. This is because safety factors against these hazards can be designed into the plant at a given cost. 35 | ETC 03064 36 Safety and Accident Prevention in Chemical Operations For these reasons, this chapter will commence with the second phase, site selection. The location study may have told us to locate our plant on the east coast of the United States in the vicinity of Atlantic City, or in the northern Midwest where efficient transporta tion by water as well as rail is available. Now it is time for site selection--the selection of a specific plot of ground on which to build. The concern is still one of location of a whole plant relative to its surroundings. The third step toward detail is plant layout. We are beyond study ing surroundings and can concentrate on the plant itself. The blocks to shuffle around here are functional operating units of the plant. We will be setting up the relative locations of things like process units, boiler plants, water treating facilities, maintenance shops, administra tive facilities, etc. Finally, there is unit plot planning. Our playthings now become individual pieces of equipment like pumps, exchangers, drums, columns, pipes, etc. The problem is the proper location of these things within a given operating unit. In these latter three phases, what can we do to enhance safety? This is the content of this chapter. 5.2. THE HAZARDS AND THE LINES OF DEFENSE In site selection, plant layout, and unit plot planning, it is possible to make allowances for only certain types of hazards. To facilitate discussion of these hazards, let us break them down into first degree hazards and second degree hazards. First degree hazards are those which provide the potential for trouble. Under normal conditions, these hazards do not cause damage to either persons or property, but they set the stage for accidents that can cause injury, fires, or explosions. Typical of first degree hazards are: 1. The presence of flammable or combustible materials 2. The presence of heat 3. The existence of ignition sources 4. The presence of oxygen 5. The presence of compressed materials 6. The presence of toxic materials 7. The possibility of human error 8. The possibility of mechanical failure 9. The movement (normal or emergency) of people and equipment through the plant 10. Reduced visibility from vapor clouds, etc. Site Selection, Plant Layout, and Unit Plot Planning 37 When first degree hazards get out of hand, the result can be second degree hazards which are capable of directly inflicting damage to life, limb, and property. These second degree hazards are: 1. Fire 2. Explosion 3. Release of free toxic materials 4. Stumbling 5. Falling 6. Collision In combating all of these hazards, we draw three lines of defense. The first line of defense consists of trying to deal with first degree hazards in such a fashion as to prevent the occurrence of second degree hazards. Success here depends mostly on careful engineering of the equipment we use. However, there are things to watch for dur ing plant layout and unit plot planning to assist this first line of defense. For example: 1. Locating ignition sources upwind (based on prevailing wind direc tion) from points of possible release of flammable materials. 2. Providing adequate accessways for the movement of equipment and people. Despite all such efforts, there are occasions when second degree hazards, such as fires, do occur. Now the second line of defense comes into play. In the event of a second degree hazard, how can we minimize the extent of damage to life, limb, and property? Here, again, there are steps we can take in selecting the site and arranging the plant to help limit such damage. Examples of these are: 1. Separating the most hazardous areas from the areas most often occupied by people. 2. Strategically locating fire fighting equipment. But some damage will result from these hazards. People do get hurt in modern industrial plants no matter how carefully we plan against accidents. The third line of defense is to provide efficient first aid and hospital facilities to care for those who do get hurt. The essence of this last line of defense is the rapid repair of damages we have not been able to prevent. The specific safety problems in Sections 5.1, 5.5, and 5.6, are all ap plications of these three lines of defense against first and second degree hazards. ETC 03066 38 Safety and Accident Pretention in Chemical Operation 5.3. THE TOOLS AND TECHNIQUES OF DEFENSE Now let us consider the tools and techniques that are available to us to help implement these lines of defense. Nature provides some of these tools and others must be supplied by man. Let us take the natural ones first. Topography is one factor which we can use in planning for safety Just as liquids flow downhill, so will many of the flammable or toxic gasses which may be released in an operating plant. Proper utiliza tion of this feature can make it work for us as a safety tool in dispos ing of these hazardous gases. Sources of large volumes of water are exceedingly valuable when it becomes necessary to fight fires. Adequate water supply can spell the difference between success and failure. Another important natural element is the direction of the prevailing wind. The local weather bureau in almost any area can supply a wind rose which will tell the percent of the time the wind blows from the direction of each point on the compass. Prevailing wind will help in preventing flammables from drifting toward ignition sources. It will also help prevent vapor clouds or toxic gases from drifting through highly populated areas or across roads. Lest it should ap pear, later on, that we are overrating the value of this tool, let us emphasize that utilizing prevailing wind is a matter of playing the odds. Obviously the wind does not always blow in the prevailing direction, and everything in the plant cannot be either upwind or downwind as we seem to suggest. However, it is always best to be on the right side of the odds as often as physically possible. Going beyond nature, the intelligence of man supplies some of the elements to enhance safety. Separation by distance is one such ele ment. We can use distance to separate one hazard from another (such as a furnace from a relief valve which may discharge to the atmosphere). We can also use distance to separate hazards from people (such as high pressure vessels from a control house). A similar tool is separation by physical barrier. A typical example here is the confinement of liquid spills by walls, such as the dikes around storage tanks. Two tools which work hand-in-hand are the concentration of hazards and the identification of hazards. Consider the location of pressure storage vessels (spheres and spheroids). It is best to isolate this type of vessel into one particular area of the plant. And the fact that hazards are thus concentrated, facilitates the demarkation Site Selection, Plant Layout, and Unit Plot Planning 39 ' of the area as being a particularly hazardous area. This helps in two ways. First, it becomes much more practical to keep people out of these hazardous areas except those who have specific duties there. Second, those people who must work in or pass through these areas can be made fully aware of the hazardous conditions which prevail. Hazards that are dispersed throughout the plant become all the more dangerous by their inconspicuousness. We must recognize that along with these advantages comes the possibility that a fire or explosion on one vessel may result in a larger total loss through the involve ment of adjacent vessels. But the consensus of judgment is that the reduced likelihood of trouble with concentrated hazards w'hich are properly looked after does result in a safer installation. The final tool is the ability to design and build physical facilities with which to combat hazards. Fire water systems, safety showers, and first aid stations are all examples of applying this tool. These are the tools we have. We must apply them as we select sites, lay out plants, and plot plan individual operating units. In this problem of application, we have found two techniques to be most helpful. Enlisting the services of a consulting Safety Committee is extremely valuable. The members of the Safety Committee provide a strong bias toward a high level of safety. This helps balance the bias of the project manager who will normally lean quite heavily toward minimum costs. Actually, most good designers have an understanding of safety problems, and the function of the Safety Committee becomes one of reviewing and recommending arrangements to enhance the level of i safety. It will be wise to include a representative of the operations side of the organization as a member of the Safety Committee. He will represent the people who must safely operate the plant after the proj ect people have finished with it and moved along to the next project. As a typical requirement, the Safety Committee should conduct a thorough review of the proceedings at these times: 1. Before the final selection of a building site. 2. When a rough, block-type layout of the plant is available--one j that shows relative locations of operating units and administrative j and service facilities. This layout should also indicate the major : features of the surrounding community. 3. Before finalizing the plant layout when major pipe alleys, roadways, tank dikes, and similar physical features may be inspected. , 4. Early in the plot planning of units before any considerable amount of detailed engineering is under way. ETC 03068 40 Safety and Accident Prevention in Chemical Operations 5. In the final stages of design when it is possible to settle the exact locations of safety showers, hose cart stations, fire hydrants, etc. Strongly supporting the efforts of the Safety Committee is the tech nique of scale modeling. Particularly during the plot planning of units the scale model has much to contribute. The ability to see three dimen sions at once adds much to the speed and effectiveness of searching out and solving safety problems. In the early plot planning, we can make use of a model made up from simple rectangular and cylindrical blocks to represent the location and general size and shape of equipment. Placing these blocks on a crosssectioned baseboard allows us to quickly observe the distances involved. For this purpose, a scale of one-tenth inch to the foot or smaller will suffice. Figure 5.1 shows an example of this type of scale model. Reviews of the final design stages will require models of much more detail. Usually built to a scale of or % of an inch to the foot, these models show piping, valves, instruments, platforms, ladders, and all such details of the actual plant. Figure 5.2 shows a detailed model of the same plant that appears in Fig. 5.1. The progression from preliminary model to detailed model is quite well portrayed in these two photographs. FIG. 5.1. A preliminary plot-planning model. Site Selection, Plant Layout, and Unit Plot Planning 41 FIG. 3.2. A detailed engineering model. 1 Timing! Here is the big problem with models: models must be availj able soon enough for reviews, and the resulting changes to occur before much engineering is done that may be wasted. The greater the waste, the harder it is to justify the changes, be they for purposes of safety or whatever. Many companies, and contractors too, are adopt ing new design methods to accommodate scale models. Moving di rectly from detailed flow charts to models, completes the model before any appreciable engineering occurs on the drafting board. This method, of course, completely solves the timing problem. It does, however, require the services of people with combined designer-model building capabilities. 5.4. SAFETY PROBLEMS IN SITE SELECTION We have been speaking in generalities up to this point. The dis cussion has covered the general principles, tools, and techniques to ! apply in achieving a good level of safety. Now, let us take the three areas of this chapter, one at a time, and discuss the specific problems involved. ETC 03070 42 Safety and Accident Prevention in Chemical Operations The first problem is site selection. Remember that the plant to be built may actually be hazardous to the community in which it will be placed. Toxic gases may drift out of the plant into residential areas or into other areas containing a concentration of people. Flammable gases may drift out of the plant to ignition sources such as incinerators or other industrial plants. Fog from cooling towers may drift across high-speed highways or roads with high-traffic density. There are ways to combat these problems. Separation by distance is one. This can be accomplished by selecting an isolated site. If other considerations make this solution impractical, we may have to rely on the prevailing wind. Unfortunately, the wind does not always blow in the prevailing direction. Placing the plant downwind from the community simply improves odds against trouble occurring from the above hazards. The possibility of collapse of high structures is another potential hazard to the community. In many cities, building codes require that tall structures or vessels be located a certain distance within property lines. This is to prevent such structures from falling on pedestrians, motorists, or neighboring facilities. The effective area of the site may thus be significantly reduced. Do not forget to check on similar local restrictions which may apply to the site under con sideration. The plant will have waste streams of which to dispose. We should be sure that the intended means of disposal will not foul the drinking water for the community. Toxic effect on marine life can be a serious problem especially where people depend on fishing for a livelihood. Here again, be aware of local, state, or federal regulations. Try to avoid routing sewers, which may contain explosive mixtures, across public or private property. Be careful about the main point of entry to and egress from the plant. The sudden surge of traffic at starting or quitting time, in and out of the plant, may cause a serious highway hazard if not properly located or dispersed. High-speed highways adjacent to the plant present the danger of vehicles leaving the road and crashing into the plant. Now turn about for a few moments. It is also entirely possible that the community may present some definite hazards to the plant and to the people who run it. Or if not presenting actual hazards the com munity may lack some of the facilities that would enhance the safety of the plant. Neighboring plants may emit toxic gases or flammable gases which could drift into the plant to sicken employees or ignite Site Selection, Plant Layout, and Unit Plot Planning 43 due to sparks or hot surfaces. In such cases, it would be better for the plant to be located upwind or again, separated by distance if such is feasible. What can the community offer in the way of fire fighting assistance? There may come a time when such assistance could mean the difference between just a fire or a real disaster. In a similar vein, we may ask what can the community offer in the way of first aid and hospital facilities? The balance of life or death for injured persons may hinge on the existence of good medical facilities. These latter two instances are examples where separation of the plant from a community by distance can be a disadvantage in safety terms. This serves well to illustrate that no pat formula insures maxi mum safety in site selection. The problem is simply to try to obtain the most favorable balance of forces for any specific situation. An adequate source of water will enhance the ability to fight major fires. An adequate source can best be assured by having a stream or lake adjacent to the plant so that fire water does not have to be pumped from the ground. Have a look at the local city water system as a possible source or supplemental source of fire water. Topography is also a factor to consider. Surely everyone involved in designing the plant will agree that a nice flat and level site is the thing to have. For safety, we would like to avoid low areas within the site which can form pools of toxic or flammable vapors or liquids. Relative to the surrounding area, it would be better for the site to be on high ground rather than in a basin. Remember to check each proposed site for existing rights-of-way for pipelines, roads, railroads, and power lines. We must assess the exist ing or potential hazards to the plant which may develop as a result of such rights-of-way. 5.5. SAFETY PROBLEMS OF PLANT LAYOUT Now, we move along to the layout of the plant itself. The center of attention here always seems to be the processing units--the real backbone of the plant--so we will discuss them first. The processing units are probably the most hazardous areas in the plant. Here we purposely bring together in close proximity many of the first degree hazards. We find toxic or flammable materials, high temperatures, high pressures, and ignition sources. These areas are full of mechanical equipment, all of which is subject to failure. Things can happen fast in the process unit, enhancing the possibility for human ETC 03072 44 Safety and Accident Prevention in Chemical Operation failure. Perhaps the only redeeming factor is that normally there are few people in the process unit. Processing units should be removed from the boundaries of the plant and should be consolidated rather than scattered. This lat ter point will improve their identification as hazardous areas and help reduce the amount of transient traffic passing through. Watch for the major ignition sources in the plant and the major concentrations of people. The processing units should be downwind from both of these since the release of flammable or toxic materials is a possibility. It is well to maintain a considerable separation of the process areas from the major tankage areas. These two are mutually hazardous to each other. While we have said that process areas should be consolidated, we must be careful the area is not too consolidated. Some separation between units is necessary because here again they are mutually haz ardous to each other. This is particularly true where the units are not integrated process-wise. In such a case, one unit may be in full opera tion while its neighbor is shut down for major maintenance, present ing an increased potential for trouble. Ignition sources, heavy ac tivity, movement of machinery, and a concentration of people in a hazardous area are all signposts of which to beware. To date, in the chemical industry, the spacing of process units, one from the other, remains a matter of good judgment for the most part. The major factors which come to bear on these judgments are: 1. Operating temperatures 2. Operating pressures 3. Types of materials present in the units 4. Quantities of materials present in the units 5. Types of structures in the units 6. Relative values (investment) of the units 7. Space required for fire fighting or other emergency operations A good written source of material to assist in these judgments ap pears in a book on safety in petroleum and related industries by George Armistead, Jr.1 Armistead's recommended minimum desirable distances, while applying specifically to petroleum refineries, will be found analogous to many similar situations in chemical plants. An other applicable reference in the handling of explosives is the American Table of Distances in the Ordnance Safety Manual.2 The integration of processes is a subject still wanting adequate treat ment with regard to requirements for separating facilities by distance. Site Selection, Plant Layout, and Unit Plot Planning 45 We critically need some careful consideration of the effect on physical separation of facilities by these aspects of integration: 1. Process integration (elimination of intermediate tankage, etc.) 2. Mechanical integration (combined or multipurpose items of equip ment) 3. Integrated or interacting control systems Every plant, of course, will need some administrative facilities. Safety considerations dictate that the main offices should be located on the periphery of the plant and as isolated as possible from the hazardous components of the plant. There are several reasons for this. First, salesmen, suppliers, and others who must conduct business with the plant personnel may do so, for the most part, without having to enter the plant proper. It is well to keep such visitors out of the plant whenever possible. They are not acquainted with the nature and lo cations of the hazards in the plant. Their normal habits may make them prone to inadvertent smoking in hazardous areas without think ing. Second, isolated office buildings will permit smoking in the offices without endangering the plant. This also permits a very clear demarkation between the areas where smoking is permitted and those where it is not. Third, the offices will house probably the largest concentration of people in the whole plant. Separation of these people from the hazards improves the odds in favor of safety. Fortunately, these motives for peripheral location of the offices are compatible with most of the other considerations in plant layout. There is one factor, however, that may be an opposing force on this point. Certain people including operating foremen and maintenance supervision must split their time between their offices and duties in the plant. They, of course, would like their offices adjacent to their in-plant duties. An ideal solution to this problem is not easy. Care ful consideration of their needs, and provisions for efficient transporta tion may coax them into the main offices. If they insist on in-plant offices, do not forget the safety considerations we discussed during the plant layout. Laboratories will normally be situated adjacent to the other ad ministrative facilities from a functional standpoint. Fortunately, the laboratory is compatible with these facilities safety-wise with two glaring exceptions. Smoking is one. There are small quantities of flammables in laboratories which may be inadvertently released into the building. Toxics, too, may be present. For these reasons, a TC 03074 46 Safety and Accident Prevention in Chemical Operations direct connection between the laboratory building and the other ad ministrative buildings may be inadvisable. Boiler plants are major ignition sources normally requiring an up wind location. Maintenance shops, too, represent a major ignition source as well as a concentration of personnel. Thus, the shops, too should be upwind and separated by distance as much as practical. Warehouses will normally be adjacent to the shops and both will want to be accessible by railroad spurs. Good plant layout will avoid routing railroad spurs through the plant, thus avoiding the concomitant hazards. Thus, peripheral location of these items is desirable.3 Similar considerations prevail for tank car and tank truck loading and unloading facilities. Traffic to these areas must not pass through the plant. Spills of toxics or flammables may occur at loading racks suggesting a downwind location as desirable. Peripheral location, also, seems best, but care should be taken not to locate tank car loading racks too close to the main line of the railroad. Locomotives may be ignition sources, and during possible derailments, could cause extensive damage to loading facilities. Regardless of these considerations, some railroad spurs will probably have to be routed into the interior of the plant. Ignition and derailment hazards must be accounted for with regard to these spurs. Waste water treating facilities may turn out to be the ultimate point of collection of toxics or flammables spilled anywhere in the plant and thus a downwind, as well as remote location, is indicated. Cooling towers have the similar characteristic of collecting toxics or flammables which may leak into the water side of coolers in the operating units. This, in itself, would indicate a downwind loca tion, a decision reinforced by the problem with fog. Cooling tower fog can block visibility on roadways, units, and in elevated structures frequently traveled by operating personnel. Thus, cooling towers should be downwind from roadways, units, and elevated structures. Elevated flares or burning pots at grade present a contrary problem. As sources of ignition, we would tend to locate them upwind. But there is another consideration. Severe operating upsets can cause flares or burning pots to belch out considerable quantities of flam mables which may fall, burning or not, on people or facilities. This, of course, would call for a downwind location. The only solution here is a location at the side (relative to the prevailing winds) of the facilities in question. We will call this a sidewind location. A side wind location is a useful compromise in cases where combinations of location problems in plant layout prevent the ideal upwind or down- Site Selection, Plant Layout, and Unit Plot Planning 47 wind location of any single facility. Separation by distance is also very advisable in the case of flares or burning pots. Storage vessels, such as tanks, spheres, and spheroids, are items to be handled with caution. Each such vessel is a tremendous storehouse of energy or of toxic materials, as the case may be. Obviously, it is wise to keep people, operating units, and tankage as far apart as pos sible. These vessels are capable of releasing tremendous spills of toxics or flammables and, therefore, by all means should occupy a down wind location. We have already mentioned that tankage should be relegated to its own private area in the plant to enhance the identifica tion as a hazardous area and minimize all extraneous traffic through the area. Three problems are inherent in the location and allocation of space for tankage: 1. Separation of tanks from each other 2. Separation of tanks from other facilities 3. Area required to provide adequate dikes Two major hazards with tanks have great effect on the above three problems. First is the possible rupture of a tank shell releasing the entire contents in a very short time. Second is the boil-over tendency of some viscous stocks when tanks containing a water layer are heated above the boiling point of the water. As in the case of processing units, little has been compiled for the chemical industry in the way of actual dimensional recommendations for the three problems above. But here again, Armistead's book1 contains recommendations which will he helpful guides. Plant layout includes the problem of adequate roadways which are very important to safety. Each process unit should be completely surrounded by roadways. Every tank should be accessible on at least one side, preferably two opposite sides, from a roadway. Try for a layout which will make every point in the plant accessible by road from two directions. Along this same line of thought, it is good to have an alternate main entrance to the plant to be used when the normal entrance is blocked by traffic or road maintenance. This may be very important in emergencies. The roads which are heavily traveled should be arranged to minimize the chances of damage to hazardous equipment from vehicles leaving the road. The layout should also attempt to minimize the road crossings by ground-level pipe alleys. The major transfer pipe alleys also come under surveillance at this point. One very influential factor in pipe alley layout is the need for looped piping arrangements in certain services. A looped system is ETC 03076 48 Safety and Accident Prevention in Chemical Operations one so arranged and valved that a failure at any point in the system can Joe isolated by closing valves, thus maintaining service to the rest of the system. To accomplish this, the layout must supply these serv ices to the critical points in the plant from at least two directions. To enhance safety, especially during emergencies, the piping for these services should be looped: 1. Fire water 2. Steam for power or heat Consider also the locations of the sources of these services. The boiler plants and pumping stations should occupy positions as well protected as possible from damage by fires or explosions occurring on other facili ties in the plant. Try to minimize the number of road crossings. Pay particular attention where alleys cross above roadways. Overhead clearance must allow easy passage of heavy equipment such as cranes with minimum danger of collision. And, finally, pipe alleys must not pass through diked areas. A fire in a diked area can rupture pipes, adding to the fuel for the fire or interrupting the supply of important services like steam. Also, pipes passing through dikes present potential leaks in the dikes. Avoid a layout which requires using trenches for pipe alleys. Trenches transport flammables or toxics (liquid or vapor) from one area to another. Electrical power, though carried in wires rather than pipes, is an other service to treat in a fashion similar to the water and steam sys tems discussed above. It is most desirable to keep electrical power lines below ground inside the plant. If economics will not permit this, take care to prevent electrical power lines from falling on critical facilities. And, turning about, locate guy wires and elevated structures so they cannot fall across the power lines. The plant may also involve docks for the loading or unloading of water-going vessels. The basic hazards here are similar to those of the other loading facilities, except that the quantities of materials in volved compare more to a storage tank than to a tank truck or tank car. For docks, an isolated, downwind location is certainly desirable. It is time now to look carefully at the locations for safety facilities. Particularly, the site for the first aid station is a problem for plant layout. The first aid station must be remote enough from the haz ardous areas to remain unscathed in times of emergency. And yet, it is from these hazardous areas that most people will come who urgently need first aid. So it cannot be too remote. The time required to reach the first aid station may someday mean life or death to an injured Site Selection, Plant Layout, and Unit Plot Planning 49 person. Obviously, a compromise is the answer in this case. A similar compromise will be needed in the case of the fire station. We should take a preliminary look at the general pattern of loca tions for safety showers, hose carts, and fire hydrants. However, the exact locations for these will carry over into the plot planning phase. One final note on topography before we leave the subject, plant lay out. It is, of course, not always possible to acquire the smooth, flat site that is so desirable. We may, in the final analysis, be stuck with a hilly or sloping site on which to lay out the plant. Several precau tions will be in order. Sources of flammables, liquid or vapor, should not be uphill from points of ignition. Sources of toxics or flammable liquid should not be uphill from concentrations of people. The site may be subject to flooding. In this case, it is wise to locate boiler houses, electrical sub-stations, and pumping stations on high ground. Continued operation of these services becomes most imperative during emergency situations, such as will surely exist during periods of flood ing. Tanks, too, are vulnerable to flooding. An empty tank will float on surprisingly little water. This can rupture lines connected to the tanks, perhaps resulting in very large spills, to further aggravate the emergency. We may even want to consider including a system of barriers to prevent the flow of liquids or the spread of fires from one area of the plant to another. 5.6. SAFETY PROBLEMS IN UNIT PLOT PLANNING Proceeding into the final area of this chapter, we face the safety problems which arise in the plot planning of the process units. This involves the physical locations of individual pieces of equipment rela tive to each other within the battery limits of each processing unit. It is not easy to develop a plot plan which will minimize the construction and operating costs, and at the same time provide an adequate level of safety. In general, the more compact the unit, the lower will be the cost of piping, pumping, and real estate. On the other hand, safety considerations would dictate that the unit be well spread out for the separation of hazards and the provision of adequate space for fire fighting or other emergency operations. A compromise is necessary. Fortunately, safety has a couple of allies which help to justify a more open plot plan with plenty of elbow room. Overcrowding will be very detrimental to the efficiency of the construction as well as the maintenance of the unit, adding to the initial and continuing costs. ETC 03078 50 Safety and Accident Prevention in Chemical Operation* Experience, over the years, in trying to balance these various factors has led to a method of plot planning pretty well accepted by many people in the processing industries. The key element in this method is ' a long, straight, ``in-line" arrangement of most of the towers, drums, exchangers, pumps, and the main pipe alley of the unit. Figure 5.3 will assist in discussing the "in-line" arrangement. This is a cross-section showing the main features involved. Starting from the left side of Fig. 5.3, notice the main features are: 1. A roadway 2. A gantry-way, which is an area adjacent to the roadway along which travels a gantry crane on rails for handling the channels and tube bundles of the heat exchangers 3. Cooling water headers beneath the gantry-way 4. A line of fractionating towers, heat exchangers, accumulators, re flux drums, etc. It is usual for the grade below this line of equip ment to be depressed about eight inches 5. The main pipe alley of the unit. If the unit includes fan-type air coolers, these can be mounted very nicely atop the pipe alley 6. A row of pumps 7. A roadway In addition to serving well the operating and maintenance require ments of the unit, the "in-line" arrangement makes notable contribu tions to safety: 1. The two roadways flanking the "in-line" arrangement provide ex cellent access to bbth sides of a considerable portion of the proc essing equipment in the unit; ideal for fire fighting or other emer gencies. The same two roadways plus the gantry-way serve as fire breaks, separating the "in-line" equipment from the other blocks of equipment in the unit. 2. The gantry crane is specifically designed for its job. Thus, it pro vides safe handling of the heavy exchanger components. 3. The area required for the gantry-way provides space for the tube bundles from exchangers to be worked on at the unit or stored until picked up and taken to the shops. All of this is possible while maintaining full traffic right-of-way on the roadway next to the gantry-way. In some of the smaller units, the gantry crane itself may be difficult to justify. Even so, the provision of some open area between the roadway and the line of equipment will help serve these purposes. Site Selection, Plant Layout, and Unit Plot Planning 52 i cross section o f the " in -lin e" arrangement o f processing equipm ent. < O S i ETC 03080 52 Safety and Accident Prevention in Chemical Operations 4. The indicated location of the cooling water headers makes prac tically the entire cooling water system accessible for repairs with out digging around and under the equipment. 5. The gantry-way provides an open area beside every fractionating tower. Tray segments and other tower internals may be lowered into this area or, in many cases, directly onto a truck bed for transportation to a working area. This minimizes chances of drop ping these parts on the other equipment or on the men who may be working on the equipment. 6. The depressed area below the tower, drum, and exchanger line-up will retain spills of flammables or toxics from spreading into other areas until the sewers carry the material away. Firewalls 8 in. high crossing the depressed area from side to side break it up into segments. This prevents the spreading of spills along the length of the depressed area. Rather than the depressed area, some people prefer the use of low firewalls all the way around this line-up of equipment. The theory here is that the walls will prevent the spread of spills into as well as out of the area beneath the equip ment. On the other hand, these walls may present somewhat more of a tripping hazard than the depressed area. Maintenance people seem to prefer the depressed area to the walls. 7. The strategic location of the pipe alley permits a clean and efficient piping layout. It virtually eliminates any runs of pipe with low overhead clearance or just above grade. Operating and mainte nance personnel will find very few head-bumpers or tripping haz ards in this type of arrangement. With this arrangement, there is no need for pipe trenches which are good carriers of hazardous liquids or vapors. 8. Notice that the row of pumps is immediately adjacent to a road way and is completely free of overhead obstructions. This will permit the removal of pumps or drivers for maintenance, even while the unit is operating, with minimum chance for damage to any other equipment. Furthermore, the pumps may be safely handled by almost anything from a fork-lift truck to a large crane, whichever may be handy at the moment. 9. Fan-type air coolers are perplexing items in plot planning. Lo cated at grade, air coolers require considerable space, and are haz ardous to personnel. This is especially true in configurations which place the fans below the tube banks. Placing the air coolers above the pipe alleys relieves both of these situations without add ing noticeably to the cost of structural support. 10. The arrangement provides clear areas for walking traffic along the ETC 03081 Site Selection, Plant Layout, and Unit Plot Planning 53 length of the rows of equipment. The openness enables people to retreat rapidly from fires, explosions, or spills of toxic materials which may occur. It also allows rapid access to safety showers, fire hydrants, or monitors. With the "in-line" equipment serving as the backbone of the unit plot plan, the other components of the unit (control house, compres sors, reactors, knockout drums, surge drums, flash drums, furnaces, etc.) may be located along either side of the in-line grouping. This approach will usually result in a plot plan with battery limit dimensions approxi mating a square. The "in-line" principle is also applicable in the case of integrated process units (integrated both process-wise and physically). In one specific instance, such a plot plan developed into a series of parallel, side-by-side, "in-line" groupings. The other components of the units occupied an area adjacent to these groupings extending along the ends of the lines of equipment. Separating these two basic areas was the "master" pipe alley for the entire process area. And, of course, branching from the master pipe alley were the individual pipe alleys for each "in-line" grouping. Figure 5.4 illustrates this concept graph ically. COOLING TOWERS BOILER PLANT FURNACES REACTORS SURGE DRUMS COMPRESSORS ETC. PREVAILING WIND -SO X z- FIG. 5.4. An example of applying the "in-line" arrangement to integrated proc essing units. ETC 03082 54 Safety and Accident Prevention in Chemictd Operation* We shall turn now to discussing those components of the unit which are not part of the "in-line" group. The control house, the nerve center of the unit, will be our first topic. Operating considerations, by themselves, would probably put the control house in the center of the unit area. This would certainly make for the shortest routine tours of the operating check points. However, the glaring hazards thus created usually persuade us to locate the control house on the perim eter of the unit area. This will facilitate escape in the event of disaster. The control house should have doors to permit this escape in a direction away from the unit. The strategic placement of the control house for the best view of the total unit will also help. In units handling toxics, the control house should occupy an upwind loca tion. Finally, keep the control house well separated from high-tem perature or high-pressure vessels, or from vessels normally containing considerable amounts of flammable or toxic liquids. Furnaces present two basic problems. As obvious ignition sources, they should be upwind from the rest of the unit. This, however, may cause a problem with flue gas drifting through elevated platforms on towers or other structures. In some cases, the best solution may be to compromise on a sidewind location. Make every effort to maintain at least a fifty-foot separation between the furnaces and other blocks of hazardous equipment. Compressors may act violently, and, as such, should be respected with a reasonable separation from other hazardous equipment. They are also prone to leak gas, and, therefore, call for a downwind location. (Modern practice seldom puts compressors or pumps into houses be cause of this tendency toward leakage. In the few cases where weather protection is a must, it is best to stick to a pavilion-type building, having a roof but no sides.) For reactors, the main consideration is to provide ample space and gear for safe handling of internals and the catalysts which may be involved. Sometimes we find reactors running hot enough to be dealt with as ignition sources. Occasionally, piping configurations outside the unit, causing pockets in the blowdown lines, will make it necessary to locate a blowdown drum at the unit. In such cases, the location of the blowdown drum must permit the piping from the relief valves to the drum to be as short and as straight as possible without any pockets ahead of the drum. Minimum pressure drop is essential. Electrical power must enter the processing unit below ground. Try to arrange the point of entry so that there need not be any electrical manholes within the battery limits of the unit. Site Selection, Plant Layout, and Unit Plot Planning 55 If the unit will have an emergency dump valve or a snuffing steam manifold, these should be close to the control house and well removed from the most likely locations for fires or other hazards. Fire hydrants or monitors must be close enough to the hazardous spots to be effective and yet not so close as to be inaccessible in emer gencies. Watch for obstructions which might prevent the stream of water from reaching the critical points. See that there is a pathway for a quick retreat if necessary. Similar strategic locations are needed for hose carts, safety showers, etc. Where it is absolutely necessary to bring railroad spurs into a unit area, try to provide adequate clearances for possible derailments. Also avoid locating equipment opposite the end of the spur in case railroad cars may overshoot, tearing out the bumper and colliding with the equipment. Before finalizing the plot plan, give a good hard look at the possi bilities of adding equipment in the future. A unit, beautifully ar ranged when built, can be completely fouled up by squeezing in addi tional equipment where inadequate space exists. Using the "in-line" arrangement, we usually find enough room in the pump row for some additional pumps and perhaps one or two additional drums. But consider carefully where to install future exchangers, towers, furnaces, reactors, etc. There may be cases where it will be necessary to house a part or the whole of a processing unit indoors. Requirements for very precise temperature control or for constant operator attention are examples which might bring about such a necessity. In dealing with indoor facilities, two of the tools discussed in Section 5.3 become ineffective. There will, of course, be no prevailing wind to consider indoors. Sepa ration by distance will most likely cause too great a financial burden because of the size of the buildings required. Even if this were not true, the effectiveness of distance is reduced indoors because released toxic or flammable vapors will be contained in the building and not dispersed as they would be outdoors. However, we can still make good use of some of the other tools. For indoor installations, we will lean most heavily, perhaps, on sepa ration by physical barrier. If ignition sources and sources of flammables both must be indoors, it will be well to allocate them to separate compartments of the building. The walls separating the two must have the absolute minimum of doors or other openings which would permit vapors or liquids reaching the sources of ignition. Facili ties especially prone to fires, explosions, or the release of toxics (such ETC 03084 56 Safety and Accident Prevention in Chemical Operationt as high-temperature, high-pressure, or large-volume containers) should be isolated from areas most often occupied by people, like the control center. Walls for this purpose must also have a minimum number of openings. But in addition, these walls should be designed for strength and fire resistance. Compartments subject to explosion may have one or more intentionally weak walls to help direct explosive forces in a direction away from people or other facilities. A building of multiple floors or of varying floor levels will have a "topography" all its own. Sources of flammable or toxic liquids should not be "uphill" from ignition sources or from people. Where vapors are involved, the location of people and ignition sources will depend on whether the vapors are heavier or lighter than air. As before, the concentration of hazards will be helpful in the demarkation of particularly hazardous areas. And, in addition, con centration of hazards will improve the practicability of providing special facilities for safety. Examples of such facilities are: 1. High-capacity ventilating systems to help keep air-vapor or airdust mixtures below the explosive limits 2. High-capacity drainage systems for very quick removal of spilled liquids 3. Remotely operated handling devices 4. Automatic fire fighting devices such as water sprays, steam blanket ing, and foam or inert gas systems Despite these possibilities, when indoors, we must definitely limit the ultimate size of the possible combined effect of several hazardous pieces of equipment concentrated in one area or compartment because of the inherent proximity to people or other facilities. As compared to outdoor facilities, the paths of retreat from housed facilities will be severely limited at best. It is difficult to overstress the need for a carefully planned system of platforms, ladders, stairs, walkways, doors, and escape chutes. Permanent platforms should provide for access to all operating points in the unit which are not accessible from grade. From all oper ating platforms (with the possible exception of tower platforms) there should be two means of descent to help prevent trapping operating personnel during emergencies. Insofar as possible, all ladders, stair ways, or slidepoles leading down from elevated platforms should land at grade at points which are least likely to be subject to fires or toxic spills. Also, these landing points should be close to pathways afford ing good retreat from the unit. Site Selection, Plant Layout, and Unit Plot Planning 57 The platforms at manholes on towers should provide enough work ing space for the safe handling of tower internals. The direction in which the manholes swing open should be away from the ladder leading down from the platform. Poorly placed valve stems can be headbumpers, shin-splitters, and tripping hazards especially to personnel in a hurry. Steam-trap discharges which are aimed across walkways, as well as uninsulated hot pipes may cause serious burns to the skin. Hot piping, where it passes within reach of operating people in their routine duties, must be insulated or otherwise protected. Summary This discussion has been oriented around the planning of new plants. The same problems, of course, apply to existing plants. While existing plants cannot be made over immediately to solve the safety problems built into them, the changes and revamps which occur over the years should follow a master plan which progresses toward a satisfactory level of safety. The ideas we have discussed here will help in develop ing such a master plan. Sections 5.4, 5.5, and 5.6 have dealt most specifically with plants designed for the continuous processing of fluids. Nevertheless, many of the ideas in these three sections, plus the material in Sections 5.2 and 5.3 will find application in plants or units involving batch-type operations or the handling of solid materials. 5.7. SUMMARIZING CHECK LIST The discussions in Sections 5.4, 5.5, and 5.6 are summarized in a check list to make them more useable. This check list appears in Table 5.1. ETC 03086 58 Safety and Accident Prevention in Chemical Operations TABLE 5.1. Check List of Safety Aspects, Site Selection, Plant Layout, and Plot Planning Block or Unit of Facilities under Consideration Site Selection Entire Chemical Plant Community surrounding the chem ical plant Plant Layout Processing Units Safety Aspects 1 1. Downwind from populated areas 2. Downwind from outside ignition sources 3. Downwind from major highways 4. Avoid stream and air pollution problems--check the legal restric tions 5. Traffic problems at main entrance 6. Isolated site--separation by dis tance from populated areas, igni tion sources, or highways 7. Topography of the site--flatter the better 8. Sources of toxics or flammables not uphill from populated areas or out side ignition sources 9. Rights-of-way across the site 1. Sources of flammables or toxics downwind from the plant 2. Ignition sources upwind from the plant 3. Sources of flammable or toxics not uphill from the plant 4. Proximity of fire stations to the plant 5. Proximity of hospitals or first-aid stations to the plant 6. Proximity of water sources to the plant 1. Separation from the boundaries of the plant 2. Consolidated--not scattered 3. Downwind from ignition sources 4. Downwind from concentrations of people 5. Separation from tankage1 6. Separation from each other1'2-- effect of integration 7. Not uphill from ignition sources or concentrations of people ETC 03087 Site Selection, Plant Layout, and Unit Plot Planning 59 TABLE 5.1 (Continued). Check List of Safety Aspects, Site Selection, Plant Layout, and Plot Planning Block or Unit oj Facilities under Consideration Administrative bldgs. Boiler plants Maintenance shops Loading and unloading facilities for tank cars and trucks Waste-water treating facilities Water-cooling towers Flares or burning pots Storage tanks Safety Aspects 1. Peripheral location 2. Separation from hazardous areas 3. Upwind from sources of flamma- bles or toxics 1. Upwind from sources of flammables 2. Separation from hazardous areas 3. High ground if site is subject to flooding 1. Upwind from sources of flammables 2. Peripheral location because of rail road spurs and truck traffic 1. Peripheral location because of rail road spurs and truck traffic 2. Downwind from ignition sources 3. Separation from main line of rail road 4. Not uphill from ignition sources 1. Downwind from ignition sources 2. Peripheral location 3. Downwind from concentrations of people 1. Downwind from ignition sources 2. Downwind from concentrations of people 3. Downwind from roadways, operat ing units, and elevated structures 1. Sidewind from ignition sources, operating units, or tankage 2. Downwind from concentrations of people 3. Separation from people and haz ardous areas 1. Separation of tanks from each other1 2. Separation of tanks from other facilities1 3. Size and arrangement of dikes1 TC 03088 ETC 03089 ETC 03090 62 Safety and Accident Prevention in Chemical Operations TABLE 5.1 (Continued). Check List of Safety Aspects, Site Selection Plant Layout, and Plot Planning Block or Unit of Facilities under Consideration Railroad spurs Indoor facilities Elevated platforms Piping Safety Aspects 1. Clearance for derailments 2. No equipment opposite the end of the spur 1. See Section 5.6 1. Permanent platforms for all oper ating points 2. Two routes for descent 3. Landings at grade in safe locations 1. Watch for head bumpers, shin splitters, and tripping hazards 2. Personnel protection from hot lines 3. Safe steam trap discharges It is important to keep these items in proper perspective. Remem ber that these are factors related to safety only. They will not be compatible in every instance with the other factors which come to bear on site selection, plant layout, and plot planning. Compromises may be necessary. And, finally, do not accept this as the final, all inclusive, check list complete for all time. By applying the general principles discussed in Sections 5.2 and 5.3 of this chapter, we may make additions. REFERENCES 1. G. Armistead, Jr., Safety in Petroleum Refining and Related Industries, 2nd ed., Simmons, New York, 1959, pp. 69-82. 2. Ordnance Safety Manual, ORD 7-224, with Supplements 1-6, U.S. Government Printing Office, Washington, D. C., 1951. 3. D. V. Gagliardi and N. R. Pratt, "Guidelines to Follow When Designing for Plant Safety," Plant Engineering, 17, pp. 108-111 (June, 1963). Services and Facilities David T. Smith The title "Services and Facilities" might be construed as all those functions which support chemical, manufacturing, and laboratory work, such as purchasing, engineering design, and training. For our purpose we will consider only those physical facilities and services directly used by personnel such as electricity, water, air, service gases, steam, heating, refrigeration, sanitary and process sewage, waste dis posal, locker and shower facilities, eating facilities, traffic, parking and control of platforms, stairs, ladders, elevators, and over-pressure relief. These items may be not only of tremendous importance in their direct contribution to safety of the employee, but failure to install, maintain, and use them properly may cause injury. It is not our prov ince to tell how to design and operate these functions that support the manufacturing and laboratory work, but comments may be of value on key safety points that experience has shown need close attention. ELECTRIC LIGHTING AND POWER Each plant or laboratory should adopt definite rules and procedures for electrical installations and work. All installations should be in complete accordance with the National Electrical Code.1 It is good economy usually, as well as safety, to install all lighting, power wiring, and equipment in chemical operations according to re quirements for Class I, Group D, Division II, Hazardous Locations. This protects against the temporary presence of explosive mixtures 63 ETC 03092 64 Safety and Accident Prevention in Chemical Operations from leaks or spills of flammable liquids or gases. Regardless of the flammability of operations when installed, changes in process to use flammable materials always seem to occur, sometimes without anyone realizing the electrical installation is unsuitable. The Class I, Group D, Division II requirements include vapor-proof lighting fixtures, totally enclosed motors, oil immersed or properly enclosed switches, and complete absence of open sparking devices (see National Electrical Code for details). It is generally more economical to prevent explosive atmospheres in rooms than it is to try to provide the special explosion-proof electrical equipment necessary for such conditions. Personnel should never be allowed to work in an explosive atmosphere. Where the creation of such atmospheres cannot be avoided through control of flammable liquids, gases, and dusts, the space involved should be limited and segregated by hoods or special ventilation. All electrical equipment exposed should conform to the requirements for Class I, Group D, Di vision I, Hazardous Locations, or whatever class and group the specific situation falls in. Electrical equipment on open, outdoor structures more than 20 feet above ground usually are considered to be free from exposure to more than temporary, local explosive mixtures near leaks. Even single phase, 110-volt fractional horsepower portable tools now come supplied with 3-wire circuits to provide a positive ground to the case. We recommend installing all light and appliance wiring and equipment the same way. This will be required some day; why not go ahead and be safe now? All building steel and outdoor structures, all tanks, drums, pipelines, open-end hose, tank cars, trucks, and chemical equipment handling or using flammable liquids or gases, or in areas where handled, should be grounded to dissipate static electricity according to the National Electrical Code. Flexible grounds should be installed to large water pipes or driven grounds, and never to electrical conduit, branch sprin kler lines, gas, steam, or process piping. These grounds should be properly maintained and the electrical resistance to ground measured periodically. Grounding conductors to give lightning protection are of much larger capacity. The voltage, name and number of equipment controlled should be clearly marked on all switch boxes, compensators, and starters. Pins and chains should be required on all butterfly switches. Extension cords should all be 3-wire, and limited to 25 ft in length. Only flashlights approved by Underwriters Laboratories for Class I, Group D, locations should be permitted in the plant. Unapproved Service! and Facilities 65 flashlights have a tendency to find their way into hazardous locations from nonhazardous locations. The present type hearing aids are capable of producing a spark of sufficient energy to ignite flammable vapors. The switch of a hearing aid should not be operated where there is a spill or leak which might result in an explosive mixture. Ordinary telephones make a high energy spark whenever dialed or rung. Explosion proof telephones are available. Radio paging system receivers may also present a problem. Owing to the rapid development of new equipment and the lack of demand by purchasers, there is little Underwriters Laboratory ap proved electrical instrumentation available. Much of it can furnish an ignition source if faults develop. However, with care in selection and installation, it is not difficult usually to avoid ignition sources from normal operation of the electrical instruments. Sometimes, in struments can be enclosed and continuously purged by a very low flow of clean air through a small air line. Often the instrument can be located outside the danger zone. Electrical work should be done only by qualified electricians or other specially authorized personnel. Before starting work on electrical circuits or equipment, voltage tests should be made to make certain that the circuits are not ener gized. All voltage tests on systems at 2300 v or higher should be made by means of a potential transformer and voltmeter. An ap proved voltage tester may be used on circuits at 550 or lower volt ages. Following major maintenance or construction wmrk on electrical circuits they should be tested for grounds by an approved method be fore the circuits are energized. Work on energized electrical circuits and equipment, at any volt age, is not only unnecessary in most cases, it is a result of poor plan ning and false pride in being able to "get awray with it." No "hot work" should be permitted if it is reasonably possible to arrange for a shut down, and w'here it is permitted, only by written exception in each case, signed by top members of management. All portable electrical equipment should be inspected and tested periodically for electrical faults. Equipment exposed to severe condi tions such as extension cords and portable drills in operating buildings and shops should be inspected monthly. Laboratory equipment under moderate exposure should be inspected semiannually, and other equip ment which receives light usage such as office machines should be given annual inspections. Each piece of equipment should be identified 1 [ i r [' I I. jr f 4 66 Safety and Accident Prevention in Chemical Operations by an affixed number and records kept or shown on the equipment to prevent overlooking inspection dates. t The fuse capacity of every circuit should be determined and marked at the fuse holder. Only authorized personnel should be permitted to replace or change fuses, and periodic checks should be made to see ' that proper size fuses are actually in place. Avoid using metal rules, metal tapes, metal hard hats, or other metal objects near energized electrical equipment where there is the possibility of an exposed electrical conductor. Seeing depends not only on lighting intensity as measured in foot- candles, but on difference in color, in light value contrast, and in re flectivity of surfaces. Accenting hazard points, controls, and other TABLE 6.1. General Recommended Values of Illumination (Illuminating Engineering Society) Footcandles Most Difficult Seeing Tasks Finest precision work involving finest detail, poor contrasts, over long periods of time. Examples: extra fine assembly, precision grading, extra fine finishing Very Difficult Seeing Tasks Precision work involving fine detail, fair contrasts, long periods of time. Examples: fine assembly, high-speed work, fine finishing. Difficult and Critical Seeing Tasks Prolonged work involving fine detail, moderate contrasts, long periods of time. Examples: ordinary bench work and assembly, machine shop work, finishing of medium-to-fine parts, office work. Ordinary Seeing Tasks Involving moderately fine detail, normal contrasts, inter mittent periods of time. Examples: automatic machine operation, rough grinding, switchboards, continuous processes, conference and file rooms, packing and shipping. Casual Seeing Tasks Examples: stairways, reception rooms, wash rooms and other service areas, active storage. 200 to 1000* 100 50 30 10 * Obtained with a combination of general lighting plus specialized supplementary lighting. Care should be taken to keep within the recommended general brightness ratios (Table 6.2) and to avoid glare conditions when light' colored materials are involved. l ETC 03095 Services and Facilities 67 TABLE 6.2. Recommended Permissible Brightness Ratios of Areas oi appreciable Size within Range of Vision Permissible Brightness Ratios* ireas Involved Plant Areas Office Areas between tasks and immediate surroundings Between tasks and more remote surfaces Between luminative surfaces and surface areas adjacent to them \nvwhere within worker's environment 5 to 1 20 to 1 40 to 1 SO to 1 3 to 1 10 to 1 20 to 1 40 to 1 The ratio of brightness of task to brightness of surrounding varies as to whether the task is darker or lighter surface. key points with contrasting color is an important aid to better seeing. Reducing or removing glare is necessary, as is eliminating too great a contrast in the light intensity of the field of sight. If the general illumination is high, we cannot see into an exceptionally dark area. .Similarly, in an area of low illumination, a very bright spot such as an unshielded light tends to blind us. However, contrast within the limits shown in the table helps us to see quickly. 6.2. WATER Hot water is used by many plants for washing down floors and equipment. Do not connect steam and water lines directly to make hot water for this purpose except through an adequately designed and maintained water-steam mixer that will shut off completely when the cold water supply is interrupted. The maximum possible hot water temperature should he known and posted, as well as all lines identified by name at the mixer and at all outlets. Water hotter than 135:F 'nming in contact with the skin usually results in at least first degree burns. Never make hot water for bathing or washing by direct mixing of -team and water--always use a water heater involving heat exchange, 'vhich will give accurately controlled water of predetermined tempera ture. Water at shower heads or wash basins must not be hotter than 135 F. regardless of the operation of shower mixing valves under the control of the user. 68 Safety and Accident Prevention in Chemical Operation* Hot water heaters should not only have a pressure relief valve for over pressure but also a fusible plug for over temperature relief. In many plants water which is not of drinking water purity is used for cooling or other process use. It is important that all water out lets in such cases be identified as to type of water, and precautionary rules should be posted to warn employees to drink, wash, and bathe only from potable water. Safety showers should be installed where handling corrosive or toxic materials. Even where employees wear flame-retardant treated cloth ing, safety showers may be of great value in extinguishing fire on employee's clothing when handling flammable liquids. It is important that a large volume, low velocity discharge from directly overhead be used, so that the employee will be drenched completely and con tinuously. A satisfactory minimum flow is 50 gpm. The high velocityspray from the ordinary domestic type shower head is unsuitable. Water to outside showers may be heated by chasing the water line with a low temperature electric "ground heating" cable having a maximum temperature of 80F. The valves of all safety showers should be at the same height and same relative position to the shower head. They should operate in the same direction and exactly alike. An employee needing a safety shower may be groping for it, unable to see. The shower station should be identified by bright, contrasting color paint and a special colored light. Frequent, scheduled testing of the shower is essential. Training and retraining in the location and use of the safety shower is important. Safety of water supply is important both from the standpoint of securing a supply that is adequate in purity for the use required, and from the standpoint of prevention of contamination of the source of supply. There appears to be no problem in direct connection with municipal or other public sources for sanitary and drinking use. Extreme care must be taken with certain types of flush toilets to prevent sewage contamination to water supplies in case of loss of water supply pres sure. Anti-siphon devices are required. Any connections made to water supplies or systems for process supply water or process cooling water must be made in such a manner that there can be no back flow of possibly contaminated water to the munic ipal or public source, or to the plant system that is used for drinking, bathing, or washing purposes. We should not rely on check valves. There must be a positive mechanism to prevent siphoning back of water in case of loss of pressure in the supply line. An effective arrangement Services and Facilities 69 is to have the municipal supply empty by free fall into a tank from which we take water to a pump inlet for process purposes. The tank is supplied with an overflow outlet beneath the inlet from the munic ipal supply.2 It is important to check that all installations are in conformance with local and state plumbing and building codes. Permits issued only after official inspections are required in many cases both for original installations, alterations, and periodically thereafter. 6.3. AIR Air is generally compressed and piped to various locations for process use, instrumentation, and for breathing by humans using air masks. Separate systems should be provided for each of these three uses. Air for human consumption must be free of contaminants such as carbon monoxide, oil vapors, flakes of rust, or other foreign materials. The ordinary oil lubricated air compressor cannot be relied on to deliver air of this quality during continued operation. Special air compressors designed for producing breathing-quality air are required. After producing air of breathing quality, it must be kept pure. The only way to insure this is to have no interconnections for process or in strument usage. Check valves have been known to fail. Cylinder air for human consumption may be purchased in many areas, but should be clearly marked and guaranteed as being "Breath ing Air." When using piped air systems for air masks, filters and traps should be installed near the outlets to intercept and remove foreign particles and liquids, such as condensed moisture. Piping down stream from the filters should be nonferrous, preferably copper, brass, or "Delrin." It is not necessary to add or remove moisture from breathing air as the body can tolerate extremely wide variations in humidity without dis comfort or harm. All breathing air outlets should be plainly identified and personnel trained never to use an unidentified outlet. Emergency breathing apparatus should always be of the self-con tained type, either the air cylinder or "Chemox" type. Canister-tvpe masks which filter out harmful gases cannot be depended on in emer gencies because of the possibility of their being used where the per centage of harmful gas is of greater concentration than they can handle, or the possibility of an oxygen deficiency. The canister mask if used should be limited to scheduled outdoor use where there is a known maximum concentration to be encountered, where plant supplied breathing air is not available, and where the exposing gas is readily noticeable in low concentrations such as sulfur dioxide and ammonia Cylinders of oxygen should not be used for emergency breathing be-i cause of the additional fire hazard they present. See Chapter 23, Res piratory Hazards and Protection. Ventilation Satisfactory indoor general ventilation requires air to be of com fortable temperature and humidity and free from harmful or dis agreeable contaminants. Humidity alone is not a major factor, humans can exist in comfort in air of widely varying percentages of humidity if the temperature is adjusted accordingly. Natural ventilation through windows and roof ventilators may suffice if adequate to prevent overheating in the summer. However careful checks should be made to assure that concentration of air contaminants does not build up above maximum allowable limits in the winter when the building is closed up. Forced ventilation systems require individual design. Exhausted air must be replaced by fresh, clean air. Exhaust collection at the points of liberation of contaminants is generally more satisfactory than fre quent changing of the entire room air. Balancing of exhaust flows is often tricky, and field tests are necessary after installation. It docs no good to exhaust contaminated air and discharge it where it will be drawn in again with the fresh air intake. Locate exhaust outlets where effluent cannot enter the fresh air intakes. 6.4. SERVICE GASES Nitrogen, carbon dioxide, and other inerting gases are sometimes referred to as "service gases" rather than process gases. Usually in stalled with schedule 40 piping for use at 150 psi or less, the principal safety problem has been one of identification. Fatalities have occurred when inerting gases have been mistakenly used for air during w7ork in side tanks or confined spaces. While color coding is helpful, all outlets and valves of service gases (as v7ell as all other materials) should be identified by having the name of the material affixed. Pressure-sensitive tapes, metal and plastic tags, or painted signs are all suitable. 6.5. STEAM Only low7 pressure steam, 15 psi or less, is suitable for most room heating equipment. Identification of steam lines by pressure is im- ETC 03099 Services and Facilities 71 portant if there are steam services of more than one pressure. Dis charge of steam traps, blow downs, and such should always be carried to points where unpredicted discharges will not expose personnel. An outside stone-filled dry well can be used for a small steam trap con densate discharge. If steam condensate discharges into a sewer line, provision must be made to prevent buildup of pressure in case of trap malfunction and escaping steam. Severe burns can result from persons contacting unprotected lines or radiators. All lines, fittings, and radiators less than seven feet above the floor should be insulated or guarded if located where personnel may contact them. 6.6. WASTE DISPOSAL Air pollution, a subject of growing concern to the public, demands that we do not liberate gases in harmful concentrations to the air, aH that we limit to an absolute minimum the emission of visible smokes and vapors. Each case is an individual engineering problem, involving consideration of absorbers, adsorbers, and scrubbers for gases, cyclones, electrostatic precipitators, or other equipment for solids. Revisions in process to eliminate the cause of the emission can sometimes be ac complished. Open burning grounds for solid and liquid wastes are permissible now in only a minority of locations, and they will undoubtedly be re stricted further in the future. Liquid and solids incinerators are now available which will handle nearly all wastes. Heavy oils and tars can be diluted in many cases with light oils to permit incineration under conditions that create a minimum of smoke. Large volume solid wastes containing a high percentage of paper, rags, and wood can be success fully burned with a minimum of smoke by the use of the "teepee" type incinerator. Some wastes may have to be buried instead of burned because of toxicity. Radioactive wastes and contaminated equipment can be dis posed of through firms contracting for that service. The disposal of liquids containing chemical wastes to public sewers or streams requires that we have sufficient neutralization and treatment to insure that they are harmless in the concentration present in the carrier stream when they leave our property. Skimmers and traps must be used to remove any oils or other nonwater soluble materials. Settling basins can be effective in removing entrained solids. Transportation of wastes by underground piping systems may pre sent the problem of explosive mixtures in the air space in the pipe if flammable volatile materials are handled. We must prevent all volatile ETC 03100 72 Safety and Occident Prevention in Chemical Operations flammable waste materials from entering closed underground sewer lines. There should also be enough openings for clean-out and main tenance in the sewer pipe. Sometimes it is necessary to install open ditches for waste liquid sewers with adequate fire stops. The open ditch, lined with or constructed of material resistant to the chemical exposure, has the added advantage of accessibility for clean-out and ease of inspection. Properly treated, laminated, wood-box ditches have proved very successful. Dilution with sufficient quantities of water before entering the waste stream disposal system helps with most waste disposal problems. Waste material discarded on the premises as trash presents a chal lenge not only to appearance but to safety and quality of production. The overall effectiveness of management of a chemical plant or labora tory can usually be accurately judged by the housekeeping observed. We are a nation of litterers, because we are inherently lazy. To prevent employees from discarding waste paper, gloves, gaskets, and a hundred other miscellaneous objects on our ground, walks, and even in out of the way corners of buildings, we must make it easy for them to dispose of waste materials quickly and with a minimum of physical effort. This means we must provide commodious, attractive trash col lection containers at strategically placed locations, frequently spaced. We must have an efficient system for keeping them collected and emp tied. Separate containers for metals and for glass are usually justified. Each should be so labeled and their use enforced. Each employee should be required to keep his own work location clean. If an employee knows he has to clean up he is much more careful not to create a housekeeping problem. The example set by supervision usually determines the overall effec tiveness. If the supervisor or foreman ignores an item of discarded trash, or contributes one, then his area will be trashy. The housekeep ing efficiency of an employee is usually a little less than that of his boss, seldom any higher. Efficient methods of collection and return of unused maintenance and repair materials can not only prevent poor housekeeping but result in major savings. "Tote" boxes for collection and return of unused materials are useful. 6.7. PLATFORMS, STAIRS, AND LADDERS Falls constitute a surprisingly large percentage of serious injuries in the chemical industry considering that the human race has been walk ing and climbing as long as it has. The condition of access routes such Services and Facilities 73 as platforms, stairs, and ladders accounts for many injuries; their mis use accounts for more. Walking Tips Look where you are stepping. Walk only on recognized pathways unless required to walk elsewhere. Do not step on railroad rails or other possibly slippery surfaces un necessarily. Do not step into puddles, on wet spots, or on oily spots. Climb and descend stairs one step at a time, with one hand on or near rail. Never use stairs with both hands occupied in carrying ob jects. Run only in case of extreme emergency. Platforms Platforms forty-eight inches or higher from the ground should have guard rails at waist height. Where material is being moved from such a platform the rail may be removed temporarily if the edge is clearly marked with a broad yellow stripe and all persons warned of the fall ing hazard. Toe boards should be installed on platforms where height and traffic present a hazard of objects falling off the platform on persons. On platforms under forty-eight inches in height, the guard rail may be omitted, but if there is any likelihood of the edge not being clearly observed, stripe painting of the edge is desirable. Stairs cut into the edges of a platform should always be guarded by rails, and hand rails are always desirable even when the steps are exterior to the platform. The importance of adequate illumination on platforms cannot be overemphasized. It is difficult to predict when some person will cross or use a platform. Ramps Ramps should have non-slip surface, and not have a gradient of more than one inch rise per ten inches of horizontal run. They are preferable to stairs for movement of groups of people at one time. They should be provided with hand rails as if stairs. When used for vehicles they must also have curbs. ETC 03102 74 Safety and Accident Prevention in Chemical Operations Stairs a. All stairs should meet the requirement of the Building Exits Code (N.F.P.A. No. 101, A.S.A. Code A-9.1). b. Maintenance of stairs requires periodic scheduled inspections covering at least these points: Are they kept free from tripping hazards? Are hand rails provided and free of rough or sharp points? Are the nosings excessively rounded, worn, slippery? Are there cracks, loose treads, or other repair work indicated? How nonskid is the tread surface? It is kept dry, clear of snow and ice? Is the landing adequate in size, and arranged so that there is no change in level as one passes through a door? Ladders Ladders are a second choice to stairs. Permanently installed lad ders should be of steel, not wood. Cage guards should be installed on all fixed ladders which extend more than 20 ft above the ground, and should when installed, start at the 7-ft level. Straight ladder runs over 30 ft should be broken with platforms every 20 ft or less. Fixed ladders providing access to roofs and other places where in stalled at a wall should have the rungs a minimum of 8 in. from the wall. Where the ladder reaches the access level, the side rails should be carried 42 in. above. This permits the climber to hold firmly while changing from the ladder to the level or vice versa. Such point of entry should always be protected by a chain or gravity swinging bar gate to protect a person from falling from the elevated surface. Avoid the installation of ship's ladders in buildings. They present a fascinating temptation to employees to be used as a stair, descend ing facing away from the ladder, and to some the allure of a sliding chute. Use either standard stairs or ladders; nothing in between. All portable ladders, either straight or step, should be purchased in accordance with A.S.A. Standard A 14.1. "Heavy-duty" ladders give an extra margin of safety. Stepladders should have a metal tie rod beneath each step. All portable straight ladders should be equipped with nonskid feet, and with permanently affixed tie ropes 9 ft in length, spliced to the second rung from the top. Extension ladders should be equipped with box-type enclosed dogs to prevent fingers from being crushed. Services and Facilities 75 When using ladders, all portable straight ladders either single or extension should be held until tied or clamped at the top. Use of extra long ladders by personnel who are not specially trained in their use should be avoided. A good rule of thumb limit is 16 ft for a straight single ladder, 30 ft for a straight extension ladder and 12 ft for a stepladder. The proper positioning of a portable straight ladder is to have the base one-fourth of the height from the wall or support plane. Never overreach from the ladder, straight or step-type. Never stand on the top step of a stepladder, always work with the knees against the top for support. The safety platform type is preferable from this viewpoint. Only one man should work from a single ladder at a time. Face the ladder, keep both hands free, and take only one step at a time when ascending or descending a ladder. Use belt fastening or lifting line for movement of tools and materials. Do not cover the surface of a wood ladder with paint or plastic. This prevents inspection of the surface of the wood for cracks or flaws. Wood ladders should be treated with linseed oil, or shellac and spar varnish. The user of a portable ladder should inspect it each time before use, but in addition there should be a regular periodic inspection of all ladders. Each ladder should be marked with an identifying number and the date of inspection. 6.8. ELEVATORS A.S.A. Code A17.1 covers the requirements for installation of elevators, hoists, dumb waiters, and escalators and should also be used as a guide for inspection and maintenance. All elevators should have mechanically and electrically inter locked car gates and hoistway gates. Safety dogs to check free fall are required. Biparting type doors should be equipped with safety astragals to prevent crushing of a hand caught during closing. Monthly testing and inspection of interlocks by qualified personnel should be carried out, and records should be kept. 6.9. EXITS AND AISLES It is important that exits of buildings be adequate to accommodate all the employees in case of fire or other emergency. The Building Exits Code (N.F.P.A. No. 101) covers requirements of construction. ETC 03104 76 Safety and Accident Prevention in Chemical Operations In general every building must have at least two means of escape from each floor. Where quick egress from hazardous operation is vital, quick opening emergency doors and chutes should be provided Each employee should see that exits are not obstructed. Each employee should be able to reach his work area and carry out his duties without being exposed to bumping, tripping, or slippery hazards. This requires clean, adequately maintained floor surfaces freedom from protruding objects, and 7 ft of head room. Where ob structions are necessary, they should be padded if possible, and marked with yellow paint. Minimum aisle widths for one-way foot traffic should be 3 ft, for two-way foot traffic, 5 ft. Greater width is preferable. Plastic tape 3 in. wide or paint stripes should be used at blind corners to designate center lines of halls and aisles, and personnel instructed to "keep to the right." 6.10. TESTING AND INSPECTION PROCEDURES FOR UNFIRED PRESSURE VESSELS AND RELIEF DEVICES A program should be established for inspecting and testing un fired pressure vessels on a periodic schedule. The same applies to safety valves and rupture discs on all pressure vessels. The A.S.M.E. Code for unfired vessels furnishes an overall guide. See Chapter 11, Pressure Vessels. 6.11. BATHING, WASHING AND CLOTHES CHANGING All employees must be encouraged to adhere to high standards of personal bodily cleanliness for health reasons in both chemical manu facturing, laboratory, and sales work. In many operations, this justifies mandatory daily showering and changing to clean work clothes, and mandatory washing of the face and hands before smoking, drinking, or eating. If exposed to chemicals, the hands should also be washed thoroughly before touching the more sensitive parts of the body such as the pubic region. Providing separate lockers for street and work clothing is often advisable. The opinion of a qualified in dustrial physician should be sought in establishing adequate health control measures. See Chapter 16, Effects of Toxic Agents. To reduce slipping hazards in shower rooms, perforated rubber mats may be used if cleaned and dried regularly. A nonabsorbent floor surface with roughened surface is generally much more desirable. Services and Facilities 77 Grab rails installed at waist height on the walls at the showers have been found helpful to prevent slips and falls. The round group wash basin of nonabsorbent cement is excellent from the standpoint of service and ease of maintenance. Liquid or powdered soap recommended by the industrial physician is preferable to bar soap. Soap scraps frequently remain on the floor as slipping hazards. As mentioned in the section on water service, all water to showers and wash basins must be delivered to the outlet at a temperature not in excess of 135F. Water hotter than this will burn. Showers should be fitted with a dial-type mixing valve which requires the user to go through the cold water phase before reaching the hot water. Direct mixing of steam and water to make hot water for use on the body is forbidden. Hot water must be manufactured by use of a water heater involving heat transfer. Adequate ventilation, control of humidity, and efficient janitor service are a must for expecting cooperation from employees in main taining the needed cleanliness in shower, lockers, and toilet facilities. In spite of advertising to the contrary, foot baths of various liquid antiseptic solutions present little assistance in controlling or preventing athlete's foot, a fungus disease. Complete drying of the feet after bathing, keeping them dry, and use of antiseptic powders recom mended by a capable industrial physician are far more effective measures. Lockers with sloping tops discourage employees from leaving articles on top. Periodic inspections in the presence of the occupant insures good housekeeping and cleanliness in lockers. 6.12. EATING FACILITIES Humans love to eat, not only at meal times but between meals. This has been attributed to hunger, boredom, frustration, sociability, desire for recognition, and many other reasons. Regardless of cause, we must recognize that employees will eat frequently whether we like it or not, so we must make provision for that fact. Provide refrigeration for safe storage of perishable foods that the employees bring to work. The household refrigerator, if of suf ficient size and frequently cleaned, is satisfactory. Both the re frigerator and lunch-box storage facilities should be convenient and free from the likelihood of chemical contamination. This means they should be away from places where chemicals are handled. I ) i 1 s ETC 03106 78 Safety and Accident Prevention in Chemical Operations Provide a clean, well-lighted location for eating, drinking, and smok ing away from chemical operating or laboratory work. In most cases it is necessary to prohibit the carrying of food or chewing materials in work areas. We must require (and provide convenient facilities for) washing the face and hands before handling or consuming foods, gum, ciga rettes, chewing tobacco, or other materials that will enter the mouth. 6.13. TRAFFIC AND PARKING We are a nation on wheels. Outside the plant or laboratory, we ride. Inside we may walk, but not far. This means parking lots for employees' cars close to their place of work, and adequate walking facilities from the parking location to the job. Snow and ice removal from the parking lot and walks is usually a management responsibility. For buses, loading and unloading facilities should be located for off-the-street access. Parking lots with guide lines will require about 9 by 26 ft parking space per car plus drive width of from 16 to 30 ft, depending on the parking angle. Without guide lines or personal control, more space will be required. Employees tend to stagger their arrival time over a much longer period than their exit, so employees simultaneously backing out of parking spaces into the drives often have minor collisions. To avoid this some employers have found that having employees back into the parking space so that they can drive out facing the drive is very ef fective. In some arrangements, a drive-through system can be used. Concrete or wood parking guides to insure uniform and minimum space per car appear effective, though other plants get adequate con trol with painted lines alone plus training. Fixed parking guides are an obstruction during snow removal. Separate pathways to provide employee protection while traversing the parking lot appear to be diminishing in use. Since these are not provided in the usual commerical lot, people seem to be able to get along safely without them. Whether separate walkways should be provided inside the plant or the employees requested to use plant roadways for walking depends of course on the adequacy of the road surface and lighting, its width, the traffic level, and speed. If roads are used for walking, it is generally better to paint walkway boundaries on them and give the pedestrian the right of way inside the walk lines than to depend on ETC 03108 Hazards of Commercial Chemical Reactions George T. Austin Commercial chemical production of useful products results from the conversion of one substance into another. Some conversion reactions are simple and subject to very little hazard, but some are most com plex and hard to control or understand. When the exact chemical nature of the reactants and products is known, it would appear that it should be possible, by applying known laws of chemistry, to assess the hazards of commercial production of the substance. In practice, this has not proved to be true. The exact paths taken by substances in changing from one substance to another are often devious. The alternate and sometimes dangerous paths which the substances may take under only slight variations in temperature, pressure, or composi tion, and the kinetics of the various steps are rarely known and frequently most difficult to foresee. The effects of temperature on chemical reactions are the most fre quent cause of surprises, so it is well to consider the known facts con cerning their relation to reaction rate. One of the oldest known rulesof-thumb of chemical work is the observed fact that reaction rate approximately doubles with every 10C rise in temperature. This is a surprisingly good approximation for a wide variety of types of reac tions and can be used in estimating when no other data are available. One implicit assumption in this statement is that the temperature of the reaction mix is uniform. This is rarely true in commercial 80 ETC 03109 Hazards of Commercial Chemical Reactions 81 reactors, so reaction rates may vary considerably within a unit, particularly if a considerable radial temperature gradient exists. The Arrhenius equation is more exact than the rule of thumb and expresses the effect of temperature on the reaction rate in the form: _JL k = ke RT (1) where k = rate constant for the reaction A = a constant E = energy of activation for the reaction R = gas constant T = absolute temperature e = natural base for logarithms A reaction whose rate changes with temperature in accordance with equation (1) is generally thought of as a normal reaction. Figure 7.1 (a) shows this type of behavior graphically. Also Fig. 7.1 shows several other types of rate change with temperature curves frequently observed in practice. It is interesting to note that if k doubles for a 10C rise, this corresponds to an energy of activation of approxi mately 13,000 cal/mole. It is evident from Fig. 7.1, that many other types of reaction speed changes occur besides the simple Arrhenius (logarithmic) one. Walas2 has tabulated the reasons for the existence of the types shown in Fig. 7.1 as follows: a. Normal behavior; rapid increase in rate with increased temperature. b. The behavior of certain heterogeneous reactions dominated by resistance to diffusion between phases, a slow increase in rate with increased temperature. c. Typical of explosions, where the rapid rise takes place at the igni tion point. d. Catalytic reactions controlled by the rate of adsorption (in which the amount of adsorption decreases at elevated temperatures) and enzyme reactions where high temperatures destroy the enzyme. e. Some reactions, combustion of carbon for example, complicated by side reactions which become significant as the temperature is in creased. /. Diminishing rate with increased temperature, for example, the reaction between oxygen and nitric oxide, where the equilibrium conversion is favored by lower temperatures and the rate appears to depend on the displacement from equilibrium. Only Fig. 7.1 I ETC 03110 82 Safety and Accident Pretention in Chemical Operations FIG. 7.1. Effect of temperature on reaction rate.1 (a) is a simple reaction; all the others result from complex reactions or are controlled by exterior physical rate processes. Before a chemical reaction can occur, there must be a collision (or collisions) between the reacting molecules. It is a rare case indeed that follows precisely the path indicated by the usual chemical stoichio metric equations, which merely show the weight and energy relation ships between the reactants and the products. When a collision occurs, a reaction will occur only if the participants possess sufficient energy to penetrate each others electron fields to such a degree that rearrange ment occurs. The amount of energy required to cause a chemical change to occur as the result of a collision is called the activation en ergy. The rate of a chemical reaction depends upon the number of collisions occurring per unit of time and the fraction which possesses sufficient energy to make the collisions effective. The larger the energy of activation, the slower the reaction at a given temperature, for only a few pairs of colliding molecules will have sufficient energy to react. Conversely, fast reactions will have low activation energies. Consider the case of two molecules A and B which react to form two other molecules C and D. When A collides with B, there is a period in which they are essentially a unit, commonly called an ac tivated complex. If the energy content of the AB pair is low, they then simply fly apart again. If energy is large, there may be ex changes of energy and matter between A and B, resulting, on their separation, in the emergence of C and D, rather than the original sub- Hazards of Commercial Chemical Reactions 83 FIG. 7.2. Potential energy change for a reaction. stances. A potential energy diagram for this system is shown in Fig. 7.2. The horizontal axis shows the percent of the total reaction which has occurred (0 = none, 100 = all finished). The distance E shows the amount of energy which must be acquired by A and B before they can react to form C and D. Since C and D have a lower potential energy than A and B, the reaction is exothermic, A + B --* C + D + Heat. The effect of a catalyst on a reaction is to make the activation energy much less. End products are the same, but reaction is faster at a given temperature because the number of successful collisions is in creased since the energy required for success is lower. Reaction rate theory is complicated in the extreme because, in general, several choices of the ultimate product may be open to the activated complex. The reader interested in pursuing this in greater detail is referred to standard works on kinetics.1' -3 Commercial reactions must be examined carefully for possible side reactions, and the kinetics of these side reactions should also be ob served, if possible. The existence of reactions of the types shown in c and e of Fig. 7.1 are the usual cause of difficulty. Hazards associated with flammability, toxicity, or instability of the primary product are usually discovered in the laboratory. Those which arrive in the form of unexpected explosions are not. The fact that laboratory scale tests have been completed without incident is no guarantee of freedom from hazard in the pilot plant or the pro duction plant. Difficulties arise in the plant because impure chemicals replace pure ones, radial temperature gradients lead to maximum temperatures well above the averages indicated by thermometers, processing times are often much longer, by-products accumulate and ETC 03112 84 Safety and Accident Prevention in Chemical Operations may have catalytic effects, pressures are often higher, and the use of metals instead of glass apparatus may exert profound effects on the course of the reaction. Safe practices require that tests be run on the reactants at conditions substantially worse than the averages ex pected. Laboratory screening tests have been suggested4-5 and add greatly to the safety of pilot plant work. A particularly difficult kind of reaction to control occurs in the manufacture of certain types of explosives. Partial decomposition of the compound being formed occurs at hot spots in the reactor and the products of the decomposition are catalysts for the decomposition. This, of course, leads to a hotter hot spot, a faster reaction, and a runaway reaction which, if explosion does not occur, is commonly called a "fume off." Properly speaking, a better term for this type of runaway is an autocatalytic reaction. Control requires elimination of "hot spots," removal of the source of catalysis or destruction of the catalytic agent as rapidly as it is formed. Runaway reactions which are sufficiently slow have been controlled by dumping the charge into large quantities of water, rapid dilution, limiting of the quantity of reactable material in process, and by providing large doors and good hiding places for operators with ur gent business elsewhere. With the advent of more rapidly responsive sensors for mechanical agents, it has become possible6 to suppress explosions which have already begun by the use of explosion sup pressors. These devices act with great rapidity on quick rise of tem perature or pressure and suppress the explosion by any of several techniques such as venting, isolation, automatic shutdown, and sudden quenching. The fundamental physical and chemical qualities governing chemical reaction velocities are currently not well understood. Each reaction must be studied in the laboratory to obtain kinetic data; this data must then be used to estimate the constants for plant size reac tors. Concentration of reactants, pressure, temperature, and the pres ence of reaction promoting or inhibiting substances are the fundamental variables involved in determining reaction rates. It is rarely possible to carry out enough experiments to determine the effect of all the variables under all conditions which may be en countered, for such experiments are expensive. Rate constants for all the reactions, side reactions, and by-reactions may all be determined without ever determining the actual mechanism by which the reac tion occurs.7 The mechanism of a reaction is the exact series of steps by which the reaction takes place. Such exact mechanisms are known for only a few reactions and the experimental determinations of them Hazards of Commercial Chemical Reactions 85 are most difficult. Most design engineers feel that a satisfactory rate equation is one that may be used with confidence to design commercial scale equipment for carrying out the reaction.8 It should always be remembered that in speaking thus of a "reaction," the principal reac tion is usually meant and this may be insufficient knowledge from a safety standpoint, since another reaction may become predominant at slightly changed conditions. Design kinetic equations are uni versally empirical. Where rate is controlled principally by concentrations, we have the so-called homogeneous reactions and these are classified by the "order" of the reaction. The reaction rate, r, of a constant volume homogene ous reaction can be expressed by: r = kcCaACbB (2) where r = reaction rate, moles/hr-volume kc = reaction rate constant, concentration units Ca, Cb = concentration of A and B moles/volume a,b = constants The order of the equation is a + b, the number of molecules which combine in the actual rate-determining step--not the molecular pro portions shown in the usual equation as frequently erroneously used. All reaction orders are empirical, and the methods for obtaining them are summarized by Corrigan.8 An approach is being made to predict ing reaction rates from absolute physical properties of systems, but this approach is many years away from commercial usefulness. Com puter use is sharply reducing the number of laboratory experiments which must be performed before reliable kinetic data are possible. Rate equations, once determined with a fair degree of accuracy by laboratory observation can be applied, along with proper other equa tions, to the design of optimum reactors, but there are complicat ing factors which may obscure kinetic effects as limiting factors in reactor design. Stevens10 lists the following limiting factors which must be carefully considered, in addition to the validity of all the mathematical assumptions made: longitudinal diffusion, radial gra dient, wall effects, impurity accumulation, and catalyst life. There are others. Reactions used industrially have been classified by Shreve11 into 26 categories, or unit processes, which offer a systematic approach to the study of chemical reactions. These have been expanded and studied in detail in several major works concerned with industrial chemical reactions.12' 13'14 Using a somewhat less comprehensive list TC 03114 86 Safety and Accident Prevention in Chemical Operationt than Shreve's, we shall briefly consider each of these types of unit processes, looking for some typical hazards characteristic of the reac tion. 1. Combustion. Solid, liquid, and gaseous fuels oxidized for the creation of heat represent such common reactions that they are rarely considered to be chemical. Normal combustion reactions are fast, but controllable. The ranges over which controls are possible are known for many substances in both air and oxygen. Tables of explosive and flammability limits are available in the literature12 and should be ob served with great care when setting up furnaces. Rates are usually held under control by regulating temperature, availability of oxidiz ing substances, or availability of fuel. Under most conditions, igni tion of mixtures is necessary, but reactive substances, for example oxygen + tung oil, may ignite spontaneously. 2. Oxidation. Oxidation differs from combustion only in the fact that the decomposition reaction is stopped enroute to C02 and H20. A combustion hazard always exists if sufficient oxidant and fuel are present. Oxidation reactions are all highly exothermic. Equilibrium is nearly always in favor of the complete reaction and steps must be taken to limit the extent of the oxidation to prevent loss of product. Marek, in Groggins (op. cit.), lists 10 types of oxidative reactions which represent the principal types encountered industrially. Vigor ous oxidizing agents are frequently used, and the following should be used with extreme caution: salts of permanganic acid, hypochlorous acid and salts, sodium chlorite and chlorine dioxide, all chlorates, all peroxides, nitric acid and nitrogen tetroxide, and ozone. Safety is usually represented by low concentrations of oxidizing agents, low concentrations of fuel, low temperatures, or better yet--all three. 3. Neutralization. Aside from thermal effects resulting from the too rapid addition of reactants, these reactions are relatively free from hazard. 4. Electrolysis. Reaction hazards are almost nonexistent. The usual hazards present where large amperages are used, poisoning hazards from the use of cyanides,15 possible explosion hazards due to the pres ence of combustible gases and products in high oxidation states (persalts, etc.) are present, but not reaction problems. 5. Double decomposition. These reactions are usually of the equilib rium type with small driving forces and relatively low heats of reaction. Hazards are low. 6. Calcination. As endothermic reactions, there are readily con trollable and rarely troublesome. Hazards of Commercial Chemical Reactions 87 7. Nitration. All nitration reactions are potentially hazardous, not only because of the frequently explosive nature of the end products, but also because most nitrating agents are also strong oxidizing agents. This dual nature of nitrating agents makes many by- and co-products possible and some of these reactions are rapid and uncontrollable. Both the nitration reaction itself and the oxidation reactions are highly exothermic.16 Temperature control must be exceptionally good if runaway reactions or explosions are to be avoided. Maximum temperatures permissible during nitrations can be estimated from temperature sensitivities of the final products, which may be found in Kirk and Othmer, Groggins, Davis,17 and others. It must be re membered that sensitivity to temperature is increased by the presence of impurities, particularly oxides of nitrogen in liquid phase nitrations, for these act as catalysts for the further oxidation. Rapid, autocatalytic decompositions sometimes occur without explosion. These are known as "fume offs" and may be quite violent. Heat evolved is rapid and end products include N2, nitrogen oxides, and free carbon. The heat of nitration of benzene is 761 Btu/lb, but the heat of reac tion in commercial apparatus is greater (895 Btu/lb), for the water formed in the reaction causes a large heat of dilution and the heat capacity of the mixed acid used in nitrating is not large. Temperature control of liquid phase nitrations is, therefore, both vital and difficult. Continuous processes for nitration are most attractive because they limit the amount of material in process and hence greatly reduce the explosion potential. Vapor phase nitrations also offer the competition between oxidation and nitration and are usually controlled by carefully regulating the concentration of a critical reactant and careful design of the heat exchange apparatus. 8. Esterification. Both organic and inorganic esterification reac tions are generally slow. Catalysts are usually necessary to force reaction completion. Hazards are usually small except when the esterifying material is a powerfully reacting material (esters of nitric or perchloric acid, for example) or one of the reacting materials or products is unstable. 9. Reduction. Hazards of the reaction are negligible and difficulties are associated almost solely with handling reactive reducing agents. 10. Animation by Ammonolysis. The animating agent is usually ammonia. Reactions, which are frequently second order, usually ap pear to be first order because of the necessity of using a large excess of ammonia. Gas phase reactions are usually run under pressure. Most common reactions are exothermic, but not strongly so. 88 Safety and Accident Prevention in Chemical Operations 11. Halogenation. Chlorine, fluorine, bromine, and iodine represent the industrially important halogens, and in that order of importance Chlorine derivatives are most important because of their much lower cost. All heats of reaction are highly exothermic, with fluorine being extremely high. Chain reactions occur in both liquid and gaseous addition and substitution reactions, making detonations possible over considerable concentration ranges. Corrosion effects are extraordi narily difficult to solve in halogen systems. Chlorination: Addition and substitution reactions are common with a wide variety of chlorinating agents and systems: chlorine gas hydrochloric acid, sodium hypochlorite, phosgene, thionyl chloride (SOClo), sulfuryl chloride (S02C12), phosphorus chlorides. Liquid and gas phase chlorinations are common and the extremely diverse paths which these reactions run make prediction without experimenta tion impossible. All reactions are potentially hazardous. Fluorination: Fluorine is the most reactive element and its reac tions are, therefore, the most difficult to control. Direct reaction with hydrocarbons are violent and frequently explosive. Unwanted C--C bond cleavage is frequent. The new bonds formed between fluorine and other substances are so strong and the heats of reaction liberated are so great that extreme precautions are necessary to keep the reaction under control. Gas phase reactions are usually controlled by dilution with an inert gas. Extreme care is essential. Bromination and Iodination: Essentially the same remarks under chlorination apply, but all reaction conditions are far less critical. 12. Sulfonation. Most commercial sulfonations use sulfuric acid as the sulfonating agent. The reactions require strong concentra tions to give good driving forces and usually high temperatures. Reactions are mildly exothermic, but usually relatively easy to control. 13. Hydrolysis. Hydrolysis means decomposition with water, but only a few reactions (usually inorganic) use water alone and unaided to effect hydrolysis. The inorganic reactions--lime slaking and sul furic and phosphoric acid formation--have problems not common to the usual organic reactions. While the inorganic hydrolyses have con trol problems, they are all concerned with heat removal and con tacting and none is sufficiently unique to warrant discussion. Organic hydrolyses are run in both liquid and vapor phases and utilize the following reagents:' (1) water alone, (2) acidic solutions, (3) alkaline solutions, (4) alkali fusion (usually anhydrous), and (5) enzymes. Most such reactions are comparatively slow and only slightly exothermic. The most important problem is how to speed ETC 03117 Hazards of Commercial Chemical Reactions 89 up the reaction. High temperatures and/or pressures sometimes help. 14. Hydrogenation and Hydrogenolysis. The use of high pressure hydrogen in a plant is always hazardous, but, aside from this problem, hydrogenation is not excessively troublesome. Hydrogenation is usually exothermic and the reactions frequently require the use of a catalyst in order to proceed at a reasonable rate. Since the heat re leased by the reaction is on the surface of the catalyst, local catalyst temperatures may be extremely high--perhaps enough to cause sinter ing. When such high temperatures are allowed to occur, cracking and various side reactions may occur which cause waste of reactants. Many hydrogenation reactions are operated at high pressure, but conditions of uncontrollability are rare. 15. Alkylation. Carbon alkylations are generally mildly exothermic reactions which proceed slowly, even under high pressures and tem peratures and in the presence of a catalyst. Competing reactions such as polymerization, isomerization, hydrogen transfer, and destructive alkylation occur when catalytically alkylating isoparaffins and aro matics with olefins. Thermal alkylations require high temperatures and pressures, but are less generally used than catalytic alkylations. Hazards exist from the use of powerful corrosives (HF, dimethyl sul fate, and so on) as alkylating or catalytic agents, but the reactions themselves are very trouble free. 16. Condensation. The energy of activation for polymerized sub stances lies between 15,000 and 30,000 cal/mole, which is close to the requirement for the corresponding monomers. Condensations are equilibrium reactions and the split-off condensation product (usually water) must be removed in order for the reaction to proceed to high molecular weight. As molecular weights become high and the reaction mass becomes quite viscous, agitation and heat removal become ex tremely difficult and burning can occur, since these reactions are exo thermic. All condensations are step-wise and are generally easy to manage. 17. Polymerization. Polymerization differs from condensation since as the materials combine, nothing is split off. The intermediates are usually short-lived active radicals or ions and the step-wise process is rarely observable. The polymer chain is generally formed in a single reaction and in a fraction of a second. Chain reactions proceed quickly following slow initiation by some readily decomposible sub stance such as tertiarybutylhydroperoxide or benzoyl peroxide. The reaction proceeds by (1) activation, (2) chain propagation, (3) termi nation, and (4) chain transfer. Heat effects can be sudden, uncontrol VU-*. 90 Safety and Accident Prevention in Chemical Operations lable, and catastrophic, and control suffers as the viscosity 0f +>. reacting mixture becomes high. 18. Diazotization and Coupling. These reactions proceed favo ki only at ice temperatures and are universally handled safely by opera ^ ing at 0C or below in the presence of an excess of melting ice 19. Fermentation. Aside from relief of the gases formed and th possibility of explosions, there are few difficulties with such reactions 20. Pyrolysis (or Cracking). Coal, petroleum, wood, and miscel laneous natural waxes and oils are converted by processing under high temperatures and pressures. The object is generally the formation of smaller molecules, but heavier molecules are inevitably formed in small yield.18 The reactions are endothermic and generally reasonably easy to regulate providing that attention is paid to careful control of temperature and the elimination of hot spots on the catalyst. The "fluid catalyst" system, which makes use of a very large weight of catalyst per unit weight of material being processed has made tem perature control of this reaction less difficult than most reactions. 21. Aromatization and Isomerization. The end results of these two processes are dramatically different, but the hazard problems are similar. Pressures, temperatures, and the presence of hydrogen offer conventional problems. The reactivity of the catalysts used must be regulated by careful temperature control, and this problem is similar to those discussed under several other unit processes since the heat gen eration is logarithmic in temperature and its dissipation is linear in the temperature differences between reactants and cooling water. This effect is discussed in detail in Chapter 8. REFERENCES 1. A. A. Frost and R. G. Pearson, Kinetics and Mechanism, 2nd ed., Wiley, New York, 1961. 2. S. M. Walas, Reaction Kinetics for Chemical Engineers, McGraw-Hill, New York, 1959. 3. S. L. Friess and A. Weissberger, Rates and Mechanisms of Reactions, Interscience, New York, 1953. 4. R. H. Albisser and L. H. Silver, "Safety Evaluation of New Processes," Ind. Eng. Chem., 52, No. 11, 77a (1960). 5. J. C. Rapean, D. L. Pearson, and H. Sello, "A Test for Hazardous Chemical Decomposition." Ind. Eng. Chem., 51, No. 2, 77a (1959). 6. C. B. Hammond, "Explosion Suppression: New Safety Tool," Chem. Eng., 68, No. 26, 85 (1961). 7. J. N. Smith, Chemical Engineering Kinetics, McGraw-Hill, New York, 1957. 8. W. F. Stevens, "Chemical Engineering Kinetics," Ind. Eng. Chem., 50, No. 4, 591 (1958). ETC 03119 Hazards of Commercial Chemical Reactions 91 9. T. E. Corrigan, "Introduction to Reaction Kinetics," Chem. Eng., 61, No. 7, 230 (1954); "Kinetics of Homogeneous Reactions, No. I," 61, No. 8, 208 (1954); "Kinetics of Homogeneous Reactions, No. II," 61, No. 9, 210 (1954); "Kinetics of Homogeneous Reactions, No. Ill," 61, No. 10,210 (1954). 10. W. F. Stevens, op. cit. 11. R. N. Shreve, The Chemical Process Industries, 2nd ed., McGraw-Hill, New York, 1956. 12. R. E. Kirk and D. F. Othmer, Encyclopedia oj Chemical Technology, Inter science, New York, 1950. 13. J. A. Kent, Riegel's Industrial Chemistry, Reinhold, New York, 1962. 14. P. H. Groggins, Unit Processes in Organic Synthesis, 5th ed., McGraw-Hill, New York, 1958. 15. C. L. Mantell, Electrochemical Engineering, 4th ed., McGraw-Hill, New York, 1960. 16. P. H. Groggins, op. cit. 17. T. L. Davis, Chemistry oj Powder and Explosives, Wiley, New York, 1943. 18. W. L. Nelson, Petroleum Refinery Engineering, 4th ed., McGraw-Hill, New York, 1958. ETC 03120 8 Hazards of Commercial Chemical Operation George T. Austin . The physical operations utilized in the manufacture of chemicals into the so-called unit operations may be divided up in a variety of ways. The number of unit operations involved in commercial chemical work will vary somewhere between 6 and 100 depending upon the person making the subdivisions. We shall not attempt to examine all of the current unit operations of significant importance in the field of chem ical manufacture, but shall instead limit ourselves to the ones which occur repeatedly in common use. These will be discussed under the following subdivisions: (1) heat transfer and reactors, (2) size reduc tion, (3) mixing, (4) materials handling, (5) mass transfer, (6) simul taneous heat and materials transfer--humidification, (7) simultaneous heat and materials transfer--drying, (8) simultaneous heat and mate rials transfer--evaporation and crystallization, (9) momentum trans fer--pumps, compressors, and agitators, and (10) momentum transfer --phase separations based on fluid mechanics. It is customary to think of hazards which exist within chemical manufacturing operations as being functions of the physical properties of the materials being handled or the condition of the immediate en vironment. Thus, toxicity, corrosivity, fire and explosion hazards, falls, and other miscellaneous health and safety features are consid ered to be the operative risks of a chemical process. While this is true to a degree, it is also true that there are certain hazards funda- 92 ETC 03121 Hazards of Commercial Chemical Operation 93 mentally connected with the unit operations which make them a good jumping-off place for planning for safety. This is particularly true during the process design stage. It is far simpler and cheaper to con sider safety features during the design stage than to attempt to in corporate them as an afterthought after the plant or unit has been completed. Success in producing a safe design depends upon an inquisitive and alert attitude toward safety.1 The existence of haz ards has been adequately pointed out in prior chapters and should be used along with the wealth of experience gained over past years in considering the role of unit operations in the safety picture. It is not enough to consider the conditions of normal operation, but it is vitally important to examine abnormal operation, startup, shutdown, and other possible conditions that may offer difficulty, such as storms, extreme cold, and interaction with surrounding units. A substantial number of federal, state, and local ordinances must be complied with in selecting equipment of all types. Although old, the section on safety in the Chemical Engineers' Handbook2 is excel lent since it shows the extremely wide range of available reference materials on individual hazards and gives a very good list of sources from which helpful material may be obtained. This is also true of several of the preceding chapters in this book. Designers have too frequently assumed that reactions would always work in the desired way and have made little or no provision for de viations from the normal course when such provision could have been incorporated into the original design at very low cost. An astonishing number of chemical reaction accidents can be blamed on elementary design inaccuracies--at least, they seem elementary in the illumination of hindsight.3 Much trouble could be saved if, during design, the concept commonly used in the atomic energy field of the Severest Credible Incident were adopted. Under this concept, the engineer considers the results of the malfunction of each item in a particular operating system and then the possible results of combined malfunc tion. This is an excellent method of arriving at a sensible estimate of the worst that can conceivably happen. It is usually possible to plan for something less than the severest possible combination of factors, but it is well to understand most clearly the scope that this might possess. Instrument failure must be planned for and arrange ments made to always fail safe or to be backed up with limit controls. An operation may be said to "fail safe" if, upon any type of failure of its control system, the unit is automatically shut down, its tem perature reduced, the flow of reagent stopped, or some other acts per formed which make it impossible for the unit to attain an unsafe status. 94 Safety and Accident Prevention in Chemical Operation Fire, and the emergencies which it may occasion, and the difficult problems associated with either elementary start-up, or emergency or regular shut-down require careful prior planning. Storage areas require particular attention when designed for new materials because provision must be made to prevent, contain, or con trol fires and explosions conceivable with the material. A frequent error encountered here is an attempt to save money by omitting dikes sprinklers, emergency pumpouts, and similar devices. Their use is infrequent but their importance in limiting the intensity of a disaster is very large indeed. Dikes offer an inexpensive method of preventing the spread of fire and a second chance to pump away combustibles during a major fire. Foam may also be applied within dike areas to aid in reducing the exposure of nearby tanks. Pumping away material from a burning tank can greatly reduce the severity of a fire impossible to extinguish, and it can salvage much valuable material. Emergency pump-out devices, portable and fixed in place, are excellent invest ments. Weather can cause such difficulties as venting explosive vapors from tanks and overflow of materials by rapid increase in temperature, so drains and vents must be studied with some care.4 Two articles bv Jennett5'6 are particularly' valuable. 8.1. HEAT TRANSFER Heat transfer is the most widely used single operation in the con version of chemicals. Equipment has been standardized to a large extent over a long period of time. Commercial heat-transfer apparatus operates from temperatures of approximately 455F below zero to very high temperatures w'hich rarely exceed 4000F because of the difficulty of containment. There is no particular hazard associated with the heat-transfer act itself, although it is, of course, essential to keep streams which might react catastrophically with each other from coming in contact under conditions of w'hole or partial failure. These require very special considerations in such cases as heat transfer in volving liquid metals and cooling waters for nitrators to be used with explosives. The accumulation of materials which reduce the rate of heat trans fer across a boundary is very common in heat-transfer work, and this accumulation usually means a slow reduction in the effectiveness of heat transfer equipment w'ith age. In the case of very rapid heat transfer, such as occurs in furnaces, this reduction may lead to the rapid increase of temperature at a spot or spots and the ultimate sof tening and destruction of these hot spots by pressure within the heat Hazards of Commercial Chemical Operation 95 transfer apparatus. In the case of jackets or exterior or interior pipes and coils for chemical reators it may mean inability to run at the desired batch size, but it may also mean inability to control reaction. Some method of constantly checking to assure that effective heat exchange surface has not been reduced below a safe figure must be made. Fortunately, the provision of inlet and outlet thermometers and pressure gages is usually sufficient to enable determination of the condition of the heat transfer surface. Within furnaces, it has be come customary to install instruments to detect the existence of dangerous conditions, and these may also actuate visible or audible alarms. Other types of instruments automatically shut off fuel sup plies, close fire doors, alert the fire prevention system, or start auxil iary ventilating systems/ Generally speaking, the idea of heat exchange is to control or balance a reactive process, and in the case of a reactor it is always necessary for stable operation that the heat removal exactly balance the heat of reaction. Since, in general, the rate of heat production of exothermic reactions is exponential with temperature rise.(see previous chapter), while the ability to remove heat varies linearly with the difference in temperature between the materials being reacted and the cooling water in the jacket, a sharply critical condition exists in reactors which is not generally appreciated. Much trouble arises when an attempt is made to move from small to larger scale equipment. Since volume (and hence the amount of material involved in reacting) goes up as the cube of the dimension of an apparatus while the area through which heat can be conveyed away goes up as the square of the dimen sion of an apparatus, it becomes increasingly necessary to provide some type of extended surface (such as cooling coils) as reactors become larger and larger. Secondary difficulties come into play because of the fact that unless agitation is very good, the material being handled is not very viscous, and the temperature drop across the cooling surface is not large, there may exist a substantial radial temperature gradient within a reactor itself. If this radial temperature gradient should be as much as 10C, the reaction rate at the center of the reactor would be approximately twice as great as that at the walls. Since it is customary to install thermometers at fixed spots within the reactor where they indicate approximately the temperature of the materials about them, the radial temperature gradient may well not be observed, and the tem perature indicated may be far away from the average temperature existing. This may create a situation fraught with great danger. When a reaction is sufficiently exothermic to make possible an ad 96 Safety and Accident Prevention in Chemical Operations iabatic temperature rise of around 200C if all the reagent present should react without loss of heat to the surroundings, special consid erations must be given to design of the reactor. Reactors designed to control such reactions show extraordinary sensitivity to very small changes in water jacket or reaction temperatures, and they are not controllable unless the temperature at which they run is only a few degrees above surrounding temperature.3 The design of such sensitive reactors, which because of their sensitivity to a particular parameter are referred to as parametrically sensitive reactors, is discussed in detail by Amundson and his students.8'10 The following example is taken from Boynton, Nichols, and Spurlin.8 Consider a simple exother mic reaction of the Arrhenius type (see previous chapter) whose rate doubles for a 10C rise in temperature. Operation is to be at about 120C which corresponds to an activation energy E of about 23,000 cal/mole. The rate of heat production then will be dQ A -Jft Te=ke (1> If this reaction is operated in a jacketed cooled kettle, the rate of heat transfer out is given by dQ B(T - T0) de (2) where Q = heat of reaction, cal/mole Q' = heat transferred, cal/mole 6 = time, sec A = a constant E = activation energy, cal/mole R = gas constant cal/mole K T = temperature of reacting mixture K B -- hA = constant including heat transfer coefficient k and Area for heat transfer, cal/sec--K--mole T0 = wall temperature--K Figure 8.1 shows plots of equations 1 and 2 for the system in question. If the jacket temperature is 116C and the heat-transfer coefficient is such that line A represents the rate loss from the kettle to the jacket, the line will intersect the reaction heat curve at 123 and 143C. The intersection at 123C is stable because the temperature will tend to return to this point if displaced slightly above or below it. The 143C intersection, however, is unstable. A slight drop in tem perature would cause the contents to drop to 123C, and the slightest ETC 03125 Hazards of Commercial Chemical Operation 97 rise would cause the temperature to go up until the reagents were exhausted or explosion or volatilization brought the reaction to a halt. Thus operation at a 7C temperature differential represents stable operation. As the jacket temperature is increased, the heat-loss line moves in a direction parallel with the original heat-loss line unless the jacket temperature change is sufficiently large to result in a change in the heat-transfer coefficient, which is rarely true. The line becomes tangent to the heat production curve at a 130C, a At of 14C. This is the maximum stable temperature of operation possible for the re action mixture and vessel described. The maximum safe At is, there fore, 14C with no factor of safety. By increasing the heat-transfer surface, operation at higher tem peratures can be brought about as shown by the third line (Cl of Fig. 8.1. Here jacket temperature is 134C and the point of tangency is 148CC; again, the maximum At for stable operation is 14C. This result is a general one for a reaction which doubles in rate for a 10C rise in temperature. For the general case, equations 1 and 2 may be differentiated and equated to demonstrate that the maximum stable temperature differential (T -- T0)criticai is: (T - T0)critical = RT2/E (3) Since reaction rates rather than activation energies are often available, another similarly derived relationship is also useful: 2 T2 (T - r0)cnt = -- = 2(In 2)Td = LiTd (4) Td is the temperature increase required to double the reaction rate. Since reactions requiring as much as 20C to double are rare and operation near the critical point leaves no factor of safety, an unknown exothermic reaction should never be operated even experimentally at rates demanding a At of more than about 10C for heat removal unless rapid and effective means for added cooling or quenching the reaction are available. Among the methods that may be used for controlling the exothermic reactions are the following: (1) Use dilute solutions or suspensions. (2) Feed one component slowly enough so that the rate of heat increase can never approach a dangerous value. (3) The addition of around 10% of volatile solvent will usually control tem perature if means for refluxing are available. (4) Operation with a large At may be possible if the time available for reaction is long enough. Controls responsive to catch incipient runaway reaction ETC 03 126 98 Safety and Accident Prevention in Chemical Operations FIG. 8.1. Rates of heat production (curve) and heat loss (straight lines). should be a part of any unit operating in this fashion. (5) Design coil reactors to remove the heat of reaction using small At. Another source of difficulty occurs when an attempt is made to store hot materials in bulk. Powders placed in containers at very reasonable temperatures may absorb oxygen from the air, and they may rise in temperature because of the inability of the generated heat to be carried away. The author recalls a particular case in which storage of finely powdered zinc stearate in boxes 18 in. x 18 in. x 2 ft resulted in melting of the inner contents over a period of two days. 8.2. SIZE REDUCTION Most of the difficulties occurring in size reduction occur from the dangerous combination of combustible materials, an oxidizing agent, and a spark. Wherever possible, attempts should be made to eliminate one or more of these vectors in order to minimize the possibility of explosion. It is desirable to provide some means of removing stray iron immediately ahead of the grinding machinery, magnetic separa tion and/or screening usually being most effective. It is also essential to ground the system with great care in order to prevent the accumula tion of static electricity, and these ground connections should be of extremely low resistance. Whenever a combustible is being ground in the presence of air it is wise to avoid rigid confinement and to provide safety reliefs to eliminate the possibility of danger from ex plosive pressure build-up. Hazards of Commercial Chemical Operation 99 Where hazardous substances must be ground, it is possible to reduce the hazard by reducing the concentration of oxidizing agents in the grinding atmosphere. Stern11 reports that a sulfur grinding unit has operated for years without fires using cooled flue-gas atmospheres containing half or less of the normal oxygen content of air. Explosive mixtures of air and dust are similar to air-vapor mixtures that are explosive in that there are minimum and maximum concentrations which form the explosive limits. It should be remembered that within a grinding and classifying system, it is quite possible to be on both sides of the explosive limit wdthin a single unit. Safety codes for the prevention of dust explosion have been issued by the United States Department of Labor and the National Fire Protection Association. Explosion-proof lights and nonsparking fan and mill surfaces are among useful materials which reduce the hazards of grinding. The common hazards associated with rotating machinery are found around grinders. 8.3. MIXING Commercial mixing operations include mixing of all possible combinations of gas, liquid, and solid. Mixing gas with gas. Normally there is little difficulty in bringing about the intimate mixing of two gases, even with very simple mixing devices. The only hazards that need be considered in mixtures of this sort are the usual onesconcerning explosive mixtures. Gas-solid mixtures. Commercial applications of this type are largely limited to solid fuel burners, and in this case there are not unusual or peculiar hazards. Where gases and solids mix intimately to accomplish chemical reaction, as for example in fluid bed processing, the extremely high heat capacity of the solid compared with the gas w'hich suspends it usually makes temperature control relatively simple. In conveying solids with gases, great care must be taken to see that all units are adequately grounded in order to prevent accumulation of static electrical potential. Gas-liquid mixing. Where liquid is agitated with a gas solely for the purpose of mixing, it has been observed12 that the explosion tem perature of the air-vapor mixture produced in such agitators is within 1F of the Pensky-Martens flash point and that in large agitators it is not affected by the rate of blowing. When the materials involved in an air-gas mixture are capable of forming an explosive mixture, due care must be exerted to eliminate possible sources of ignition. Ground ing is particularly vital, and it should be remembered that it is nec- , j j ` j : j j j j j J J f | * ETC 03128 100 Safety and Accident Prevention in Chemical Operation* essary to have not only a high-voltage static charge but also a certain minimum current density and the presence of an explosive mixture ' order to bring about an explosion. Particular attention should be paid to the possibility of forming combustible foams where gases are being blown through liquids. In addition to being hazardous the pres ence of foams can prove to be major irritants, for foams have gotten out of hand and completely buried plants. There are a variety of foam-controlling agents available which have greatly reduced the nuisance of ordinary foams. Liquid-liquid mixing. Where liquids are of low viscosity, some type of high-speed mixer is generally used. Aside from the hazards of possible combustion and the common hazards concerned with rotating machinery, there are no special hazards. It is usually unsound to op erate side-entering propellers in large tanks with the propeller only partially submerged because of the possibilities of bent shafts and destroyed motors, but this difficulty will usually show itself as an extreme nuisance long before it becomes a hazard. Where liquids of extremely heavy viscosity are to be mixed in heavy-duty kneaders or rolls, it is extremely important that extraneous solids be excluded in order to avoid possible damage to man and machine. Where ex plosive materials are being handled it is desirable to provide weak walls, barricades, and some type of snuffing device. Liquid-solid mixing. Low-viscosity mixes are generally done with high-speed propellers or turbines. Light slurries are frequently mixed using air-lift agitators, and here again the remarks made under gasliquid contactors apply. No special hazards exist peculiar to these machines, and the problems of processing are concerned primarily with material properties. Solid-solid mixing. Devices used for this type of work are generally quite simple but all must be regarded as potentially hazardous when a combustible material is present with air, because there is a very strong tendency to build up static charges unless extreme care is taken in grounding. In some types of ribbon mixers involving close clear ance, it is necessary to take the usual precautions for the elimination of possible tramp iron or similar spark-causing substances. 8.4. MATERIALS HANDLING This section will be restricted to techniques involved in moving solids, since techniques involving pumps and blowers are covered else where. An almost endless variety of devices are utilized for the in- Hazards of Commercial Chemical Operation 101 termittent and continuous movement of solids within a plant. The most important from the standpoint of tonnage handled are the var ious types of conveyors, cranes, and bucket elevators. Most of the hazards connected with the use of these devices arise from the pos sibility of injury from contacting moving machinery, and these hazards are not special or characteristic of the chemical industry. Particular attention should be paid to the loading and unloading section of all types of conveyors since it is usually at these points that trouble de velops. Bucket elevators, in particular, have difficulty with jamming of materials between the buckets and the side of the boot. Chutes can be most troublesome, due to the accumulation of materials on the sides, and it may frequently prove to be very difficult indeed to ac complish regular discharge of material from them. If the chute is too steep, it gives the same effect as dumping material and may result in dusting or damage to fragile material or to a hazard from the move ment of toxic materials in dust form. If the incline is too flat, material cannot be made to slide over it. 8.5. MASS TRANSFER Most mass-transfer problems such as gas absorbtion and solvent extraction show no unique problems that characterize this group, al though fire hazards are quite common. Columns operating at high temperatures, particularly those which use some steam in processing should be designed with great care to prevent the possible accidental injection of liquid w'ater into the tower. One of the most spectacular accidents which the author ever witnessed came about from the injec tion of a few gallons of wmter into the bottom of a fractionating tower distilling hot tar. The ensuing rain of bubble caps, which covered almost ten acres, testified to the vigor of the flash evaporation that took place within the tow'er. Towers should, in general, be equipped not only with pressure, but also with vacuum-relieving devices. Connec tions made to tanks which are designed for wash-out during periods of nonoperation can prove to be disastrous if opened at inopportune times. A lead-lined still 6 ft in diameter by 10 ft high which had not been properly equipped with a vacuum valve w'as reduced to a mass of crumpled wreckage when a spray of cold water was injected into it by opening the wrong valve. The still wras full of steam, w'hich con densed at once, forming a high vacuum inside. This permitted at mospheric pressure to crush the still. ETC 03130 102 Safety and Accident Prevention in Chemical Operations 8.6. SIMULTANEOUS HEAT AND MASS TRANSFER I--HUMIDIFICATION Humidification in itself is generally a most innocuous operation The blower and exhaust systems, however, may constitute a fire hazard in themselves, and the ducts may introduce hazards contributing to the spread of fires. Ducts should not pierce fire walls, floors, or make connections between hazardous areas. Where it is essential that this be done, provision must be made for automatic shut-off in case of fire or explosion. Fume scrubbers designed to reduce the amount of combustible or objectionably odored material released into the atmosphere may ac cumulate large quantities of dangerous combustibles at points within their systems unless they are specifically designed to hold up a min imum of combustible liquid or solid. 8.7. SIMULTANEOUS HEAT AND MASS TRANSFER II--DRYING Drying equipment comes in a wide variety of types which differ sharply in the hazards of their operations. Those which possess moving parts are subject to the usual difficulties found around moving ma chinery. Where the material being dried may become dusty, release a combustible substance, or is simply combustible, it is advisable to provide some type of emergency overrange protection to insure that overheating of the dryer does not result in a fire or explosion. Sprin kler systems are ideal, but they are rarely used. The design of con tinuous dryers should be carefully examined to eliminate the pos sibility of the deposition of combustibles on electric heaters or the undue accumulation of dusts at points within the apparatus itself. Spray dryers are subject to the same possibilities of dust explosions that one might find handling any other combustible material in an atmosphere containing oxygen. Flash dryers should be treated in the same fashion as grinding equipment, and their ducts should be provided with explosion vents if there is a possibility of an explosive mixture being formed. Hazards can frequently be greatly reduced by using flue gases rather than straight air as the drying medium. Drum dryers should have their feed scavanged for large-size particles which might be thrown out from between the rolls with violence, damaging operator and rolls. Hazard* of Commercial Chemical Operation 103 8.8. SIMULTANEOUS HEAT AND MASS TRANSFER III--EVAPORATION AND CRYSTALLIZATION Because most evaporation is conducted within a closed system, there is rarely a major difficulty with this type of equipment. It is desirable that the bodies be equipped with pressure and vacuum relief valves and with provision to protect the equipment in case of fire or accident within the unit area. Like heat exchangers, evaporators can become fouled, thus greatly reducing the heat transfer ability. Scale accu mulations are particularly troublesome when the scale is soft, and hence they are a very poor conductor of heat. Scales should be re moved at regular intervals by means of standard commercial devices. Crystallizers are generally simple agitated tanks or vessels designed to form crystals of carefully controlled size from saturated or slightly supersaturated solutions. These units possess almost no hazard other than those associated with the materials being handled. It is sometimes desirable to provide protective equipment such as shear-pins to prevent strain on motors or gears in case of an interruption or freeze-up. 8.9. MOMENTUM TRANSFER-PUMPS, COMPRESSORS, AND AGITATORS Pumps and compressors are among the most thoroughly standard ized, widely used, and trouble-free devices found within the plant. Most difficulties with new pumps and blowers arise from corrosion, cavitation, water hammer, or misuse. It is commonly said by plant installers that if a pump can get through the first hour of operation that it may expect a reasonable life. This simply confirms the fact that almost all difficulties with pumps occur during their start-up. J. R. Caddell,13 has an excellent discussion concerning the operation and maintenance of fluid-flow equipment which is particularly valuable in its description of the hazards of starting centrifugal pumps. J. E. Troyan,14'15'16 has provided an excellent comprehensive report on what we should actually do to prepare for a plant start-up including training operators, preparing manuals, and debugging. Pumps and connecting valves, installed where normal working pres sures are reasonable, fail because of ram effects caused by sudden shutting of valves. This is commonly known as "water hammer." If water is flowing in a pipe and it is suddenly stopped, its kinetic energy j ' j j j j j j | J ETC 03132 104 Safety and Accident Prevention in Chemical Operation is suddenly released, The head h (in ft of water) thus suddenly de. veloped is: (5) where c = velocity of pressure wave disturbance up the pipe ft/sec V = reduction in velocity ft/sec g = gravitational constant ft/sec2 c, the velocity of wave propagation, may be estimated by Jonkowsky's formula: c = 4660/Vl + KB (6) where K = ratio of elastic modulus of water to pipe shell material (0.01 for steel) B = ratio of pipe diameter to pipe thickness These equations are both rather approximate, since they assume in stantaneous closing, but the results are conservative. Water-hammer effects can be large and destructive, particularly to concrete or similar fragile pipe and to large cast-iron pumps. Preven tion includes providing air cushions within the system or by making it impossible to close valves fast. If a pump operates in such a fashion that areas within the stream of fluid around the impeller fall to pressures below the vapor pressure of the fluid being pumped, cavities form in the flowing fluid. When these cavities move into an area of higher pressure, they collapse very suddenly. When the bubbles collapse, fluids meet at high velocity and pressures at the point of collapse become quite high. If the point of collapse occurs on the surface of the metal, it may be stressed beyond its elastic limit and the impeller and the casing may be quickly eroded and destroyed. Cavitation is best avoided by providing ample netpositive suction head to the pump in question. Much of the difficulty that occurs in the installation of pumps arises from the lack of understanding of the basic differences between positive displacement and centrifugal pumps. Centrifugal pumps utilize the least electrical current when their outlet valves are completely closed, and they utilize the most electrical current when the outlet valve is open and there is no pipe attached to them. Positive displacement pumps, on the other hand, utilize their maximum electrical energy when they have their outlet valves shut off, and they utilize the least current when their outlet valves are wide open. Centrifugal pumps frequently have their motors destroyed by attempts to test them on a job without Hazards of Commercial Chemical Operation 10S connecting the outlet pipe, or by running water through a pump de signed for a less dense material. When starting a centrifugal pump, the fluid to be pumped should be free from dirt, abrasive material, and any foreign objects. While it is not always necessary that the fluid being pumped be entirely free of solid, it is always desirable that large objects be excluded unless the pump has been especially designed for this pur pose. A strainer of adequate capacity and efficiency in the suction line is desirable. Damage to the pump will result if it is not filled at the time of starting or if the net positive suction head is less than a minimum. It is usually wise to check for strains placed on the pump by installed piping. If mis-alignment is appreciable it will often be detectable by the fact that the pump shaft cannot be moved by hand power. Piping stresses lead to rapid wear of the seals on the pump and, if sufficiently large, may cause rubbing of the impeller or case cracking. Care must be taken to see that piping is so installed that thermal expansion (or contraction) does not set up intolerable stresses. Pump and primemover bearings should be checked thoroughly for proper lubrication. Suction and discharge pressure gages should be installed with each pump, as this will permit an immediate check on the operating condi tions of the pump. When starting a centrifugal pump, it is desirable to close the dis charge valve to reduce the load on the driver, and this valve should not be opened until the motor has come up to speed. If this valve is then left closed for any substantial length of time, the work done on the small volume of liquid contained within the casing may result in its boiling, and trouble may arise from this volatilization (such as loss of prime or destruction of the packing). Packing glands on pumps must be kept so adjusted that there is a continuous drippage from them. This drippage serves as a lubricant and coolant between the packing and shaft. After a shutdown, the centrifugal pump should not be started again until the discharge valve is shut off and the shaft rota tion stopped, otherwise the pump motor may burn up while coming up to speed. Care in selecting packing is necessary and is usually done by trial. Much of the personal hazard in use of pumps arises from the require ment that there be a certain amount of leakage around the shaft pack ing or shaft seal. It is generally possible, by selection of one of the various sealing methods, to have a leakage to the outside which is tolerable, but this may not be so in the case of some toxic, corrosive, or reactive substances. The use of mechanical seals can frequently reduce or entirely stop the losses around packing glands, but median- 106 Safety and Accident Prevention in Chemical Operations ical seals must be installed and maintained with more than the usual care. Starting up reciprocating or other types of positive displacement pumps requires as much care in seeing that the valves are open as is required in seeing that the valves are closed in the case of centrifugals Most difficulties with reciprocating pumps arise from lack of attention to their automatic lubricators. Do not exceed the speeds recommended by the manufacturers and watch carefully for vibration in pipe sup ports which may lead to failures in the pipelines. It is now possible to move significant quantities of solids in pipelines and this operation has become increasingly popular. The maximum al lowable particle diameter of the solid to be handled should not exceed one half of the smallest canal dimension of the pump, and the maximum permissible size of the particle to prevent blockage of the lines must be such that the particle diameter is not greater than 1/3 that of the pipe. Stability of operation of this type of unit is most important, and start up and shutdown can be most troublesome. Data on designing and operating this type of unit have been presented in the literature.17'ls'19 8.10. MOMENTUM TRANSFER--PHASE SEPARATIONS BASED ON FLUID MECHANICS Filtration, centrifugation, screening, elutriation, jigging, classifica tion, and sedimentation all show only the difficulties which we would expect due the handling of difficult materials. Care must be taken to avoid fires, or excessive exposure of personnel to toxic materials. Cen trifuges require heavy supports of highest quality. Care should be taken in the installation of pressure filters to assure that personnel are not liable to be sprayed with injurious or offensive materials, but the precautions are no more elaborate than those taken in the installa tion of virtually all types of pressure equipment. REFERENCES 1. R. P. King, "Safety Aspects of Chemical Engineering Design," Mutech Chem. Eng. J., No. 3. 39 (Spring 1961). 2. J. H. Perry, Chemical Engineers' Handbook, 3rd ed., McGraw-Hill, New York, 1950. 3. H. Popper, "Last Year's Major Explosions Prod This Year's Safety Push," Chem. Eng., 70, No. 1, 91 (1963). 4. J. H. Johnson, "Fundamental Requirements for Safe Arrangement of Drains and Vents," Pet. Refiner, 26, 91 (1947). 5. E. Jennett, "Design Considerations for Pressure-Relieving Systems," Chem. Eng., 70, No. 14, 125 (1963). Hazard of Commercial Chemical Operation 107 6. E. Jennett, "Components of Pressure-Relieving Systems, Part II," Chem. Eng., 70, No. 17, 151 (1963). 7. D. M. Considine, Process Instruments and Controls Handbook, McGraw-Hill, New York, 1957. 8. D. E. Boynton, W. B. Nichols, and H. M. Spurlin, "How to Tame Dangerous Chemical Reactions," Ind. Eng. Chem., 51, No. 4, 489-94 (1959). 9. 0. Bilous and M. R. Amundson, "Chemical Reactor Stability and Sensitivity," A.I.Ch.E.J., 1, No. 4,513 (1955). 10. 0. Bilous and M. R. Amundson, "Chemical Reactor Stability and Sensitivity II, Effect of Parameters on Sensitivity of Empty Tubular Reactors," A. I. Ch. E.J., 2, No. 1, 117 (1956). 11. A. B. Stern, "A Guide to Crushing and Grinding Practice," Chem. Eng., 69, No. 25, 129 (1962). 12. C. M. Klaerner, "Formation of Static Electric Charges on Agitating Petroleum Products with Air," Ind. Eng. Chem., 39, 92 (1947). 13. J. R. Caddell, "Fluid Flow in Practice," Chapman and Hall, London, 1956. 14. J. E. Troyan, "How to Prepare for Plant Start-ups in the Chemical Industries," Chem. Eng., 67, No. 18, 107 (1960). 15. J. E. Troyan, "Trouble-Shooting New Processes, Hints lor Plant Start-up: Part I," Chem. Eng., 67, No. 23, 223 (1960). 16. J. E. Troyan, "Pumps, Compressors, and Agitators, Hints for Plant Start-up, Part III," Chem. Eng., 68, No. 9, 91 (1961). 17. E. Condolios and E. E. Chapus, "Transporting Solid Materials in Pipelines," Chem. Eng., 70, No. 13, 93 (1963). 18. E. Condolios and E. E. Chapus, "Designing Solids Pipelines," Chem. Eng. 70, No. 14, 131 (1963). 19. E. Condolios and E. E. Chapus, "Operating Solids Pipelines," Chem. Eng., 70, No. 15, 145 (1963). Process Design W. G. Hudson 9.1. INTRODUCTION In a direct sense, the process designer is the architect of the process plant. Like the architect, he must produce a set of drawings and specifications that will serve as the basis for the detailed engineering design of the final entity. His ultimate goal is to develop a processing scheme that will most economically produce the desired products in a safe fashion. The fulfillment of the following requirements serves as his standard of safety: 1. The process must operate safely at design conditions. 2. Suitable provisions must be made to cope with unsafe deviations from design conditions. 3. Safe start-up and shut-down procedures must be established. Although these requirements may seem rather elementary in concept, compliance with them is mandatory. Failure to provide sufficient cooling surface at critical points or to make inadequate allowance for inert-gas purging would be examples of disastrous designs in which these requirements were not satisfied. In assuring that the requirements of safety are fulfilled, the designer must evaluate the hazards involved. Commonly confronting the process designer are four groups: 1. Fire hazards, either inherent in the process or from external sources 2. Sources of excessive overpressure, explosion hazards 108 ETC 03137 Process Design 109 3. Hazards resulting from abnormally high or low temperatures 4. Hazards created by toxic or highly corrosive materials The following sections will trace out the technique of safe process design, the methods of controlling the process variables to ensure the safety of the design, and the evolution of safety in new-process devel opment. 9.2. THE TECHNIQUE OF SAFE PROCESS DESIGN The Flow Sheet The key to safe process design is the preparation of a complete, de tailed flow sheet. This development starts with the basic process calculations and then determines that each step of the process meets the safety requirements. Potential hazards must be evaluated and re moved, or else suitable provisions must be made to restrict them. The problem is complicated, somewhat, by the fact that most proc esses are so highly integrated that each step in the process affects the operation of other steps. It is desirable, therefore, to divide the process into sections, and to analyze each section not only for its internal safe operation but for its effect on the safety of other sections. Convenient subdivisions can be made by dividing the process into reaction, separa tion, materials handling, and storage sections. REACTION SECTIONS Reaction sections must be considered first because they determine the dynamics of the whole process. Such sections may be quite simple, involving only a stirred batch tank, or they may be as sophisticated as a cat-cracker; yet, they can all be systematically analyzed for safe operation by breaking them up into feed, reactor, and outlet sub sections, or systems. THE FEED SYSTEM Examine the effect on the reaction of an abrupt change of flow of each of the reactants. Combustion reactions, for example, may pass through either upper or lower explosive limits because of such a rate change. The necessity of providing appropriate warning devices, spare pumps or compressors, and automatic start-up of such pumps or com pressors may be evaluated on the basis of safety. ETC 03138 110 Safety and Occident Prevention in Chemical Operations In a similar fashion, ascertain the consequences of failure of tem perature control in the feed system. Such a failure may lead to dis astrously high, or low, temperatures in the reactor causing either dangerous overheating, or loss of reaction and accumulation of mate rials in an unsafe composition range. For batch systems, make certain that reactants will be added in the correct order. The familiar procedure of adding sulfuric acid to water is an example of where order of addition is important. Start-up and shut-down procedures must be worked out quite care fully. The order in which feeds are cut in or out, and the attendant control of their temperature and pressure under transient conditions must be established. Facilities may be required for purging the system of air prior to start-up, and of flammable or noxious materials at shut down. All equipment and instrumentation should fail safely. In extreme cases, emergency power or instrument-air supplies may be required. Safe materials of construction must be specified in detail. THE REACTOR SYSTEM Ascertain that the reaction is chemically safe. The reaction must be in a stable area of composition, pressure, and temperature. Evaluate the effect of changes in these on the stability. In particular, consider the possibility of undesirable side reactions occurring. These may produce noxious or explosive materials or lead to dangerous fouling or plugging. Certain reactions, such as combus tion or halogenation, may proceed at explosive rates. Explosive limits for combustibles in air are published by the National Fire Protection Association.1 Other systems may require literature search or explosive limits tests. Where corrosive conditions prevail, safe materials of con struction must be specified.2 The chemical ground-rules having been established, the mechanical safety features of the reactor can be defined. Here are some salient features to be considered. What are the effects of poor distribution of reactants on the safety of the reactor? In simple flow reactions, poor distribution may lead to hot spots, resulting in equipment failure or to undesirable side reactions. In stirred reactors, poor agitation may lead to similar ends, and acci dental stoppage of agitation may be disastrous. As a special case of poor distribution, consider the possibilities of plugging due to sedimentation. Safety valve outlets and connections for control devices must be so located and designed as to prevent Process Design 111 plugging. Continuous purging of such outlets may be required. Pock ets where materials can accumulate are, in general, to be avoided. Specifications for pressure relief devices must provide for the worst predictable possibilities. In the most hazardous cases, special shield ing and isolation of the reactor may be required. Provisions must be made for maintaining the temperature of the reactor within safe limits. Heat transfer surface is often required, and its arrangements and the provisions for supplying it with cooling or heating media are of grave concern in most reactor design problems. Poor distribution of heat-transfer surface in the reactor can lead to inordinate local temperatures, causing hazardous side reactions or direct equipment failures. The possibilities of fouling the surface, both on the reaction and medium side, must be considered in the same vein. The adequacy of supply and control of medium to the heat-transfer surface must be critically reviewed insofar as it affects safety. Ade quate provisions, similar to those discussed under the feed system, must be made, to guard against failure of the supply and, in event of failure, to insure an orderly shut down of the reactor. The proper selection of the heat-transfer medium is of importance. Direct firing may lead to "hot-spots." High temperature heat-transfer fluids may be overheated, causing fouling or plugging, or they may freeze up in colder portions of the circuit. Hazardous conditions re sulting from leakage between reactor and medium side of the exchange surface should be evaluated as a basis for the mechanical specifications for the surface. The whole manipulation of the heat-transfer system during start-up and shut-down must be developed. Special provisions for heating or cooling the circulating medium may be required, in particular, for emergency shutdowns. The freeboard requirement in liquid-phase reactors must be specified. Expansion of liquids with temperature, the extent of foaming, height of swirl caused by agitation, and the effect of liquid carry-over on the safety of downstream equipment, must all be considered. THE OUTLET SYSTEM In concluding the safety analysis of the reaction section, consider the products withdrawal system. All the undesirable events so far noted culminate here, and they are in position to effect the rest of the process downstream. Consequently, it is here that monitoring devices to warn of impending danger are quite commonly located. From the previous evaluation of the feed and reactor systems, the degree to which 112 Safety and Accident Prevention in Chemical Operations composition, pressure, and temperature may be effected at the reactor effluent can be determined and used as a basis for the selection and specification of such devices. Equipment to transfer materials to the next section, an adequately sized intermediate storage, and provisions for emergency blow-down tanks and flare systems must, likewise be carefully designed. Separation Sections Safety Significance. Operations involving the physical separation of constituents are of special safety significance insofar as their effect on other plant sections is concerned. The production of off-specification material could result in, for example, unsafe conditions in other por tions of the plant or unsafe finished materials. Separation processes to be considered here will include crushing and grinding, size separa tion, distillation, absorption, extraction, filtration, and drying. Crushing and Grinding, and Size Separation. These operations can produce copious quantities of dust so that the possibility of dust ex plosion must be considered.3 Facilities to prevent the discharge of dust into the atmosphere may be required. In some instances the safe per formance of other operations may hinge on the reliability of the size separation equipment. Excessive fines may cause reactions to proceed at unsafe rates, and oversize material may result in plugging of equip ment. Distillation. Control of product composition may be of special sig nificance. If a recycle stream is being produced, hazardous material may be built up in the recycle either through poor design or operation. Unwanted materials may be inadvertently left in outgoing products by malfunctioning of the unit. In either case suitable detection and warning devices must be specified. Possibilities of coking or polymerization in reboilers may constitute a special hazard. Vacuum distillations of flammable materials may be hazardous in that air insemination may lead to the formation of ex plosive mixtures. Absorption. Where noxious materials are being absorbed prior to the discharge of a gas into the atmosphere, special care is required in monitoring the composition of the gaseous effluent. Extraction. Extraction systems may contain large volumes of flam mable liquids. The codes of the National Fire Protection Association1 are recommended as a basis for safe design. Where liquid-filled sys- ETC 03141 Process Design 113 terns are contemplated, allowance must be made for the thermal expansion of the liquid. Filtration. Filtering operations can present special safety problems where they involve the removal of harmful constituents from a food product or a product to be used in conjunction with food. Monitoring devices and testing procedures must be provided that will satisfy the particular requirements of the Federal Food and Drug Administration. Drying. Drying operations may cause similar dust hazards to those mentioned under Size Separation. Safe drying conditions for heatsensitive materials must be evolved. Control of humidity may be im portant in the prevention of undue caking. Explosion and fire hazards are attendant to the removal of flammable solvents.* Materials Handling The same principles apply, of course, both to the intersectional mate rials handling and to internal materials handling within the plant sec tions. As previously noted, the capacity of materials-handling equip ment may be determined by safety demands for temporary overloads. The selection and detailed specification of the equipment must also be made with safety considerations in mind. PIPING Drainage. Drainage valves should be provided at the low points of the system and all piping should slope downward, toward them. Valving. The specification of safe-valving arrangements is required. Double block valves should be used for the dependable shut-off of haz ardous materials. By-passes must be provided around control valves where possibilities of emergency operation are evident. Check-valves are to be provided to prevent inadvertent backing-up of flows into feed systems, of corrosive materials into corrodable equipment, or of flam mable or noxious materials into unsafe areas. Valving required for isolation of equipment during shutdown, or for start-up conditions, must be specified. Corrosion and Erosion. Ordinary corrosion data are useless where erosion is coincident. Tests under simulated conditions may be re quired in order to define material specifications. Relief Valves. For liquids that have a high coefficient of expansion, such as light hydrocarbons, pressure relief valves must be provided 114 Safety and Accident Prevention in Chemical Operations between block valves. Relief valves must also be provided on the dis charge of all positive acting pumps and compressors. SOLIDS HANDLING Mechanical Conveyors. Various types such as belt, flight, and screwconveyor are examples of mechanical conveyors. Common hazards to be controlled are dust explosions and the escape and dissemination of noxious or flammable dusts. Pneumatic Conveyors. The following two items must also be consid ered in designing pneumatic systems: (1) If the material handled is readily flammable, inert gas must be used as the pneumatic fluid. Pres sure systems are preferred over vacuum systems because they obviate the possibility of air infiltration. (2) Where poisonous or noxious ma terials are being transported, special attention must be given to recov ery of fines from the exit air. A complete recycle of the carrier gas may be desirable. Storage Sections SIZING The previously noted effects of process upsets must be considered in sizing the storage capacity. These effects are particularly important in the sizing of intermediate or recycle storage. In cases where unsafe finished products may be produced, adequate "off-spec" storage must be provided. The total quantity of storage having been determined, the next problem is to arrange for its convenient and safe disposition. SOLIDS STORAGE Types of Storage. Solid materials may enter or leave the plant in bags, drums, or by bulk carrier. They may be stored in their own con tainers, in hoppers or silos, or in bulk piles, either indoors or outdoors. Recycle or intermediate storage is usually provided by hoppers, silos, or bulk piles. Safety Considerations. Flammability of the material must be estab lished to determine the safe size and spacing of storage units and the design bases for the electric and fire-protection systems. The possi bility of spontaneous combustion,3 either in bulk piles or piles of bags may limit the safe depth of storage. Temperature measurements of ETC 03143 Process Design 115 such piles may be required. Susceptibility to dust explosions will determine grounding equipment required. Wind-borne dusts from outside storage piles may be eye or lung irri tants. Absorption of atmospheric moisture may cause swelling of the materials or lead to the formation of corrosive liquids or gases. The swelling of grain in silos and the reaction of water with A1C13 to yield HC1 are familiar examples. Oxides of nitrogen (silo-filler's disease) may result from silaging fresh fodder. Purge systems using CCL, N2, or other inert gas may be required for flammables storage bins.3 Bins and silos should be equipped with level indicating devices to warn of over-filling or near-emptiness. LIQUID STORAGE General Requirements. Liquids are generally received or shipped in drums, carboys, tank cars or trucks, or by pipeline. They may be stored in their shipping containers or in tanks. Intermediate storage is usually in tanks. Hazards. In evaluating the hazards involved, the following points may be considered. 1. The National Fire Protection Association publishes lists of the flash points of common liquids and classifies their fire hazard according to the flash point.1 The safe sizing of storage units, the spacing of such units, and the grounding, electrical, and fire protection systems required' are determined on the basis of this classification. Highly flammable liquids may require inert purging of vapor spaces. 2. The vapor pressure of the liquid at storage temperature will set the design basis for pressure vessels, pumps, and piping. Where vapor pressures are subatmospheric, adequate vents must be provided, or the containers must be designed for vacuum service. . 3. Special caution must be taken in the storage of very corrosive or poisonous liquids. The possibility of accidental spillage and the accidental discharge of toxic vapors are two principal hazards. 4. As in solid storage, the indication of levels in all storage tanks is a "must." GAS STORAGE General Methods of Storage. Gases may be received or shipped, in liquid or gas phase, in shipping cylinders, tank cars or trucks, or by pipeline. Storage may be in the shipping containers, in pressure storage 116 Safety and Accident Prevention in Chemical Operations vessels, or in gas holders. Intermediate or recycle streams are usually stored in pressure vessels or gas holders. Liquefied Gases. The standards of the NFPA should be followed when designing handling and storage facilities for liquefied petroleum gases. Gaseous Storage. Gases present the usual hazards of flammability and explosivity associated with combustible liquids. Unlike liquids, however, gas storage tanks cannot be effectively- diked. Consequently, leakage can disseminate to a distant source of ignition and the result ing fire flash back to the storage vessel. Gas-holders must be protected from sub-atmospheric pressures that could lead to their collapse. Liquid-sealed holders should be provided with high-level warning devices. Sealing liquids must be chosen that will not freeze in winter, or provisions must be made for heating the liquid. Detailed information for the safe storage and handling of gas cylinders is given in the Matheson Gas Data Book-` and in publications of the Compressed Gas Association. Where noxious gases are being stored under pressure, the discharge from relief valves must be con ducted to a safe place. Flow Sheet Review The foregoing analysis has been designed to aid the process engineer in development of a safe flow sheet. This flow sheet should now be carefully rechecked by making an imaginary start-up of the plant, byrunning it "on paper" at design conditions, by checking it out for operation under emergencies, and by- shutting it down safely. Docu ment all pertinent safety data such as flash-points, explosive limits, and toxicities6 to assure proper design of the electrical and fire protec tion systems and provisions for personnel safety. The safe design of the plant rests on the accuracy and completeness of the data furnished by the process designer. Batch or Continuous Processing In the selection of processing schemes, the designer is quite often in a quandary- as to whether to proceed via the batch or continuous route. Considerations of size of plant and relative complexity are of impor tance in making this selection. Economics can be brought into play, and finally, the relative safety of the two modes of operation can be compared. The following analysis is intended to guide the designer in making this latter comparison. CONTINUOUS PROCESSING 1. At a given production rate, smaller quantities of materials are held-up in the processing system. Where flammables are involved the fire hazard is proportionately reduced. 2. Hazardous intermediate products may be consumed as fast as they are produced, thus minimizing their hazard.4 3. Since there is no variation of process conditions with time, automatic control is more readily applicable. Chances of operator-error are thereby minimized. 4. Process equipment is not as subject to cyclical fluctuations in pres sure and temperature. BATCH PROCESSES 1. Where hazardous operations are involved, units may be isolated from one another. Spread of fire or explosion can be easily mini mized by dividing the process into small, isolated parallel units. 2. Where product purity is of safety significance, batch processing may be advantageous. This presumes, of course, that careful analytical control of the product quality is made on each batch. Reaction Conditions In discussing the reaction section, no special consideration was given to the type of reaction being performed. In the following discussion, reactions will be classified according to their thermal behavior, such as endothermic or exothermic. Either of these types may be operated in one of three ways: - 1. Isothermally, that is, by either adding or removing that amount of heat required to maintain the reaction at constant temperature. 2. Adiabatically, where no heat is transferred through the reactor walls, and the adiabatic temperature change determines the final reaction temperature. 3. Nonisothermally, nonadiabatically, where some heat transfer is provided in the reactor but the temperature does not remain constant throughout the reaction. ! i j i j ETC 03146 118 Safety and Accident Prevention in Chemical Operations ENDOTHERMIC REACTIONS Isothermal Case. Batch reactors may be run isothermally by con tinuously varying the heat supply. Fluid-bed systems offer the best means of maintaining uniform temperature conditions in continuous gas phase reactors. Liquid-phase reactions may be run either at the boiling point of the constituents or of a common solvent. The prin cipal dangers associated with isothermal operation are that a failure of heat supply can result in unreacted materials being carried in unsafe amounts into the next process section, and that poor temperature con trol can result in undesirable side reactions. Adiabatic Case. Here, the heat of reaction must be supplied by the heat content of the incoming reactants. Poor temperature control of the reactants will lead to the same undesirable conditions as noted for the isothermal case. Nonisothermal, Nonadiabatic Case. Fired tube reactors are ex amples of this case. The usual hazards resulting from coking and un desirable side reactions are prevalent. Good control of firing, over the length of the tube, is important not only in these respects, but to avoid the attainment of dangerously high metal temperatures. Pro visions must be made to keep temperatures at a safe level if the feed system should fail. EXOTHERMIC REACTIONS Importance of Temperature Control. Boynton, Nichols, and Spurlin7 present an analysis of the requirements for the temperature control of highly exothermic reactions for which a 200 C adiabatic temperature rise is possible. Their general conclusion is that, in order to prevent reaction run-away, a maximum of 10C should be maintained between the reactor and the cooling surface. Safe designs may be provided by insuring that sufficient cooling surface is available to prevent addi tional temperature rise, and by the use of auxiliary cooling in the form of refluxing liquid or additional cooling surface controlled by reliable instrumentation. A rise of 10C above the set-point requires twice the original cooling effect to bring the reaction back under control. Isothermal Case. The methods of operation listed under Endo thermic Reactions are applicable here, excepting that heat is now being removed. Loss of cooling effect may result in a run-away reaction. Process Design 119 Adiabatic Case. Since the heat of reaction is removed by the prod ucts, the peak temperature achieved is dependent on the temperature of the incoming feed materials. Diluents may be added to the reac tants to increase the heat capacity of the incoming feed stream. The close control of diluent addition and feed temperature is essential in maintaining the maximum temperature within safe limits. Provisions for additional diluent or auxiliary cooling of reactants may be required to prevent run-aways. Nonisothermal, Nonadiabatic Case. Where diluents cannot be used, a cooling surface must be provided to what would otherwise be an adiabatic reactor. Here, both cooling surface and/or reactant tem perature control must be designed to prevent excessive temperatures or run-away conditions. 9.3. SAFE CONTROL OF THE PROCESS VARIABLES Definition and Scope Control will be defined, for present purposes, as the total concept by which the process variables are contained within design limits. The concept includes instrumentation, equipment design, and safety devices. Rather than attempt to describe all of these in any detail, attention will be focused on the application of instrumentation to process sys tems and to the constructional details required for the safe containment of the process. Control of Temperature in Thermal Systems A thermal system is defined as consisting of the instrumentation, heat-transfer surface and medium, and the pumps and piping required for the addition or removal of heat. Figures 9.1 through 9.4 are illus trative of typical systems to be described below. Table 9.1 defines the nomenclature used in the figures. Direct-Fired Kettle. Figure 9.1 illustrates the control system for a direct-fired batch kettle. Owing to the large heat capacity of the kettle, temperature control is achieved . by controlling the flue-gas temperature with a two-position controller. A stirrer is provided to equalize temperatures in the kettle to improve heat transfer and to minimize local overheating. Provisions are made for automatic shut off of the fuel supply in event of flame failure. The pilot-light by-pass ETC 03148 etc 03149 H >ui ITR Process Design 121 FIG. 9.2. Direct-fired process heater. ET<= 03150 122 Safety and Accident Prevention in Chemical Operations valve can be interlocked so that it is closed during normal operation Steam smothering is provided where the process fluids are flammable Direct-Fired Process Heater. Similar safety features are incorpo rated in the continuous process heater shown in Fig. 9.2. Here, tem perature control is achieved by maintaining a constant flue-gas tem perature with a proportional-plus-reset controller. The outlet process temperature is continuously recorded and, should it rise to a dangerous level, a warning device is actuated. The fuel gas valve closes on in strument air failure. Steam-Heated Tubular Reactor. In Fig. 9.3 a fluid-filled bulb sensor is used to obtain an average process outlet temperature. The FIG. 9.3. Steam-heated vertical tube reactor. Process Design 123 controller is of the proportional plus reset type, so that load changes can be accommodated. Note that a steam trap is provided ahead of the control valve to remove line condensate. An air-vent trap is pro vided to purge noncondensables from the steam chest. Strainers are used ahead of all traps. Boiling Liquid-Cooled Tubular Reactor. Figure 9.4 illustrates a method for controlling the temperature of exothermic catalytic re actions. The boiling water provides for rapid heat removal and, by using small diameter tubes, high local catalyst temperatures can be avoided. In designing such a system attention must be given to the following points: 1. The heat-transfer surface provided must be sufficient to allow opera tion with a maximum of 10C temperature difference between water and reaction for cases as noted in the section on the Reactor System. In other cases this differential must be small enough to preclude the possibility of film boiling on the water side. 2. The catalyst level should be somewhat lower than the water level to allow for surges. 3. Water feed-pump capacity must be sufficient to take care of possible surges in the heat output of the reaction. 4. An upper limit switch may be required on the temperature controller which will cause interruption of the flow of reactants to the reactor. 5. Likewise, a low-water switch, which will cause shut-down of reactant flows, may be required as a part of the water-level controller. EFFECT OF TEMPERATURE ON EQUIPMENT DESIGN Low Temperature Construction. Materials of construction for low temperature work must have good impact strength at working tempera ture. Most common materials are suitable for use at temperatures down to -- 20F. For colder temperatures aluminum, copper and nickel, or austenitic stainless steels are required. Fluorocarbon plastics such as Teflon and Kel-F are recommended for use down to -- 400F by the manufacturers. Insulation for low temperatures must be sealed against the influx of atmospheric moisture. The elimination of water from the processing system is, of course, essential. High Temperature Construction. Metallic materials for high tem perature are chosen on the basis of creep-strength. Stresses normally used are those at which creep is limited to 1% in either 10,000 or ETC 03152 ETc 03153 F IG . 9.4. B oiling liquid cooled tubular reactor. Process Design 125 100,000 hr. Corrosion rates are markedly accelerated at high tem peratures. However, much more severe corrosion may occur in parts of the system where condensation of corrosive agents can occur. Re sistance to atmospheric oxidation8 and hydrogen attack9 should be investigated where applicable. High temperature vessels may be internally insulated to reduce the temperature on the metal shell. Certain precautions must be taken in designing such vessels. 1. A common practice is to line the vessel with low conductivity in sulation and to protect this with a further inner-lining of brickwork. Owing to the porous nature of such insulation the pressure drop through the vessel must be held to a minimum to prevent passage of hot gas up through the insulation. Where pressure drop is unavoidable, baffles may be inserted in the insulation or a pre stressed brick lining10'11 may be used. 2. Where condensation of corrosive process fluids can occur at the temperature of the metal shell, or where shell corrosion is otherwise imminent, the shell must be built of a suitable alloy or protected by a corrosion-resistant nonmetallie liner. 3. Provisions may be made for cooling the external shell, either con tinuously or upon demand. 4. The temperature of the shell should be under constant surveillance. Where cooling is used, the rise in temperature of the cooling medium can be monitored. 5. Rapid pressure or temperature changes should be avoided. SAFETY DEVICES Except for instrumentation specifically designed to detect and allevi ate over-temperature conditions, the use of fusible. plugs constitutes the only positive means of reducing the stress in pressure parts when they are subjected to higher than design temperatures. Rossheim et al.12 point out the relatively small control that the designer has over the temperature that his equipment may experience in operation. This is particularly true in the case of internally-insulated vessels. Pressure Containment Pressure Vessels and Piping. The Code for Pressure Piping13 covers the safe mechanical design of piping. The American Society of Me chanical Engineers Boiler and Pressure Vessel Code14 gives rules and ETC 03154 126 Safety and Accident Prevention in Chemical Operation* design stresses for the safe design of vessels for use up to 3000 psig Perry15 covers the general design procedure for high-pressure equip ment. Under any circumstances, the rules applicable within a par ticular state must be complied with. All the above codes and rules set a safe standard insofar as struc tural safety is concerned but they do not, necessarily, guarantee the pressure tightness of the design. Where hazardous materials are con tained under pressure, special attention must be directed to the assur ance of pressure tightness and to the monitoring of leaks. Vacuum systems containing flammables must be so designed that the possible influx of air does not allow the attainment of concentrations within the explosive limits. X-ray and magnaflux inspection of welded joints provide reasonable assurance that pressure integrity will be obtained. The main source of leakage, however, occurs at mechanical joints. Stationary Mechanical Joints. These include threaded and flanged connections. The selection of thread sealant and gasketing must be made on the basis of reliability in containing the pressure, resistance to corrosive media, and thermal stability. Thermal stability should include not only stability at processing temperature but also at tem peratures likely to occur in event of fire. Moving Seals. Moving seals may be required to contain pressure at points of entry of either rotary or reciprocating parts. Rotary joints occur at valve stems, centrifugal-pump shafts, and agitator shafts. Reciprocating joints occur at control-valve stems and at the shafts of reciprocating pumps and compressors. Valve-stem seals are usually of packed construction, packing being selected on a basis similar to gaskets. Where absolute tightness is required metal or plastic diaphragms or bellows may be used ("pack less" construction). Rotary seals on pumps or agitator shafts may consist of packed stuffing boxes or mechanical seals.16 Where loss of material from the system would constitute a serious safety hazard, two mechanical seals may be arranged back-to-back and the inter vening space pressured to somewhat above system pressure with an inert sealing fluid. A "canned" motor may also be used under these conditions. Lubricated stuffing boxes are applicable to control-valve stems and reciprocating pump and compressor rods. Nonlubricated packings are available for use with oxygen. Diaphragms or bellows can be used for the absolute sealing of control-valve stems. Inert-gas purged "distance-pieces" can be provided on the atmos pheric side of compressor stuffing boxes to prevent the possibility of air sucking into the cylinder during the suction stroke. A similar dis tance piece vented to a safe place can be used to trap off the leakage of noxious gases. SAFETY DEVICES Signalling and warning devices can be actuated by the pressure sensors. Over-pressure relief is ordinarily provided by spring-loaded relief valves or rupture discs. Both these devices are available in a wide variety of materials of construction. Relief valves are available for use at 750 psig at 900F to 45,000 psig at 100F. The range for rupture discs depends on the applicability of the disc material, but the ranges generally available are from up to 1000 psig at 1000F to 55,000 psig at 100F. Rules for the sizing and location of pressure relieving devices are given by the ASME Pressure Vessel Code, the National Fire Protection Association,1 and governmental agencies. In general, the set pressure must coincide with the design pressure of the vessel. Relief valves are selected for use on clean fluids and where automatic closure of the relief port is desired subsequent to discharge. Where rupture discs are used under fluctuating pressure or very corrosive conditions one of the arrangements shown in Fig. 9.5 is recommended. If used under vacuum conditions a vacuum support should be used under the disc. Needless to say, passageways to relieving devices must not become obstructed. Discharge piping must be sized to carry the effluent to a safe place and with minimum pressure drop. Blow-down tanks may be provided for liquid discharges, and gases can be exhausted to stacks or flares. Discharge piping must be anchored to resist shock effects. Analytical Procedures for Control of Composition The desirability of accurately monitoring the composition of process streams is of obvious safety significance. Controllability of the process can, thereby, be enhanced, and the approach of unsafe ranges of com position detected sufficiently early for corrective measures to be ap plied. The analytical procedures to be used must be specified by optimizing the requirements for accuracy, frequency, and time required ETC 03156 128 Safety and Accident Prevention in Chemical Operations PRESSURE GAGE TO ATMOSPHERE TO ATMOSPHERE FROM PRESSURE SOURCE A.-USING RELIEF VALVE RUPTURE OISC COMBINATION RUPTURE DISC ASSEMBLIES B.- USING TWO RUPTURE DISCS IN SERIES T FROM PRESSURE SOURCE FIG. 9.5. Use of rupture discs under corrosive or fluctuating pressure conditions. for analysis. Instrumentation, where applicable, is to be recommended over laboratory-type procedures. SAMPLING Where process instrumentation is being used, it is necessary that its sensing element either be located in the process stream or that a sample stream be withdrawn from the system and run through the instrument. In the first case it is necessary that the element not be located in stag nant areas. If solids are present, means must be provided to prevent their accumulation on the sensor or to allow for their frequent removal. Corrosion of the element may cause loss of calibration. Where sam pling is employed it is important that the sample be representative of the process contents. Provisions must be made to prevent the accumulation of materials on the wall of the sample piping. Since only small sample flows are ordinarily required, it is well to minimize the length of sample lines and, thereby, reduce time lag. Process Design 129 SAFETY APPLICATIONS Although some analytical instruments offer no continuous control feature, they can all be arranged to operate warning or emergency shut-down devices. In addition to monitoring process streams, such instruments can be used to warn of the presence of toxic or objection able materials in the plant atmosphere and in the discharge from stacks or sewers. Mercury-vapor detectors and explosive-limits meters are common examples of the former, and SO2 detectors and pH meters are common examples of the latter. 9.4. SAFETY AS A PART OF PROCESS DEVELOPMENT Evaluation of Hazards The evaluation of potential hazards must begin in the earliest stages of process development. The ensuing program must include provisions for the complete solution of all problems that may affect the safe operation of the projected process. Where not available in the litera ture, data relative to flash-points, explosive-limits, toxicity, and corro sion must, of course, be obtained experimentally. An alertness in detecting unexpected safety problems, and a high degree of ingenuity in solving or averting them, is a prime requirement for the successful completion of many development programs. Pilot Plants The piloting of a new process often begins with a small bench-scale unit in which the feasibility of a doubtful procedure can be demon strated. Here we obtain the first indications of any unusual safety problems. Corrosion rates, under process conditions, are experienced for the first time; the safe limits of operation can be roughly deter mined; and indications of plugging and fouling are discernable. The data are generally crude at this point and offer only indications of trends, but all further development along safe lines depends on the skill with which the unit is operated and the data are interpreted. Larger pilot plants are built to obtain more precise engineering data and to secure reliable information on the product. Integrated pilot plants, which include all of the proposed process steps, may be built to demonstrate the whole process on a suitably large scale. The accumu lation of data, suitable to the development of a safe flow sheet as under 130 Safely and Accident Prevention in Chemical Operations Section 9.2. may serve as one of the prime motivations for this latter program. Methods of controlling hazardous reactions, the safe han dling and storage of materials, prevention of the accumulation of hazardous materials, and the production of a safe product must all be developed to a satisfactory degree. Scale-Up Piloting is not generally required for unit-operations equipment. Where experimental data are required, such as for filtration or sizereduction equipment, manufacturers tests, with scale-up on the basis of physical laws, will usually suffice.17 Chemical reactors are scaled up by applying the principles of chem ical kinetics to empirical data.1*'19 The process designer must assure himself of the accuracy with which the process variables have been controlled and the degree to which adiabatic (or other) conditions have been maintained. In a similar vein Stevens20 points out the limi tations in the application of kinetics resulting from longitudinal diffu sion and radial gradients in the pilot-plant reactor, and the effects of wall surface and impurity accumulations. REFERENCES 1. The National Fire Codes, Vol. I, Flammable Liquids and Gases, National Fire Protection Association, Boston, 1963. 2. H. P. Godard, "Corrosion Prevention Starts with Design," Ind. Eng. Chem., 49, 79A (1957). 3. The National Fire Codes, Vol. II, Combustible Solids, Dusts, Chemicals and Explosives, National Fire Protection Association, Boston. 1963. 4. Staff Report, "Safety in Chemical Plant Design," Ind. Chemist, 36, 280 (1960). 5. Matheson Gas Data Book, Matheson Company, East Rutherford, N. J., 1961. 6. Patty, Industrial Hygiene & Toxicology, Two Volumes, Second Edition, Inter science, John Wiley & Sons, N. Y., 1963. 7. D. E. Boynton, W. G. Nichols, and H. M. Spurlin, "How to Tame Dangerous Chemical Reactions," Ind. Eng. Chem., 51, 489 (1959). 8. T. Lyman, Metals Handbook, The American Society for Metals, Cleveland, 1961.' 9. R. T. Effinger, M. L. Renquist, A. Wachter. and J. G. Wilson, "Hydrogen Attack of Steel in Refinery Equipment," Pet. Refiner, 30, 130 (1951). 10. G. D. Galletly and E. G. Chilton. "Design of Prestressed Cylinders with Non- metallic Linings," Ind. Eng. Chem., 50, 65A, (No. 8) (1958). 11. J. A. King, "Prestressed Brick: Cure for Lining Woes," Chem. Eng., 66, No. 10, p. 194 (May 18, 1959). 12. D. B. Rossheim, G. P. Eschenbrenner, J. J. Murphy, and R. S. Eagle, "Pres sure Vessel Overtemperature Hazards," ASME Paper Number 59-A-319, The American Society of Mechanical Engineers, New York, 1959. Process Design 131 13. The Code for Pressure Piping, The American Society of Mechanical Engineers, New York, 1959. 14. ASME Boiler and Pressure Vessel Code, The American Society of Mechanical Engineers, New York, 1962. 15. J. H. Perry, Chemical Engineers Handbook, 4th ed., McGraw-Hill, New York, 1963. 16. Dynamic Sealing, Theory and Practice, VI, Face Seals, Koppers Co., Inc., Metal Products Division, Baltimore. N.D. 17. L. Michel, R. D. Beattie, and T. H. Goodgame, "Census of Equipment Scale- up Practice," Chem. Eng. Progr., 50, 332 (1954). 18. E. L. Clark, "How to Scale up Pilot Plant Data and Equipment," Chem. Eng., 65, 129 (October 6, 1958). 19. R. Fleming, Scale-up in Practice, Reinhold, New York, 1958. 20. W. F. Stevens, "Kinetics in Scale-up," Ind. Eng. Chem., 50, 591 (1958). ETC 03160 10 Instrumentation for Safe Operation Donald Richmond Automatic control of chemical processing equipment has made it possible for a chemical operator to assume the responsibility of addi tional units of operation. This is because controllers are performing tasks which were formerly handled by men. This simple concept of greater productivity applies to batch as well as to continuous opera tion. This chapter presents some of the safety considerations which are engineered into process design, where safety engineering begins. While this chapter covers only a few of the most common safety de vices generally associated with instrumentation, it illustrates the type of thinking which is required of designers in order to maintain a high degree of safety in present day plants. For the purposes of this discussion the term instrumentation means the use and application of industrial instruments of measurements and control. This definition includes indicators, recorders, controllers, and transmitters for measurements such as temperature, pressure, flow, liquid level, and analysis. Instrumentation also embraces the fields of data reduction, alarms, and interlocks. At the present time 5% of the capital investment in large chemical plants may be in instrumentation. The rate of growth of instrumenta tion cost in one plant over the past 5 yr has been approximately four times as fast as the plant average. The total invested capital per employee in this company has increased approximately fourfold in the 132 ETC 03161 Instrumentation for Safe Operation 133 past 10 yr. In a large oil refinery the investment per employee may be as high as $200,000. These statistics provide clues as to the long range effect of the increasing demands of greater productivity upon instrumentation. Process design engineers are just becoming generally aware of the safety concepts of instrumentation, including some of its inherent dangers. Actually, safety and instrumentation go hand in hand because good engineering includes safety in its design. The types of manu facturing equipment which we will find in the plants of tomorrow will dictate special safety requirements in engineering. The hazards that we find associated with special products and special materials which have to be handled, will generally dictate a certain amount of safety instrumentation. Efficient control implies safety. Everyone is inter ested in safety from the standpoint of protection of personnel and equipment. The operating department, however, has an extra interest in safety because of the desire to prevent production losses such as spills. The maintenance department likewise has a special interest in safety because of the desire to easily maintain the operating facilities. For example, instead of installing a control valve near a hazardous area where a man might easily injure himself, it might be better to locate the valve at a safe location where the maintenance crew can easily repair it. A few of the common safety devices which are com monly used in chemical plants will be discussed. Self-acting Pressure Regulators Two basic types of pressure regulators are shown in Fig. 10.1. One is the type with the integral downstream pressure tap, and the other has the external downstream pressure tap. The first valve is a single-seated valve which normally is used either with small flows and small valve sizes or on those applications involving small pres sure drops. The other valve is double seated generally because of large flows or large pressure drops. Usually double seating begins at the iy2 in. size. In both cases, however, the action of the spring is opposed to the pressure that is placed upon the diaphragm. The pur pose of the regulator is to reduce a fluid pressure to a smaller value. Rupture of the diaphragm is the commonest cause of failure in these self-acting regulators. Should the diaphragm fail for any reason, the action of the spring in both valves will be to return the valve to the wide open position. Because of its design, therefore, pressure regulators fail in the unsafe position, such as open. Upon such a failure full upstream-line pressure will exist on the downstream side of the valve. 134 Safety and Accident Prevention in Chemical Operationt Pressure regulators always fail open Safety or relief valves are often required when using pressure regulators FIG. 10.1. This brings up the first rule about pressure regulators--they always fail in the unsafe position. Because of this inherent weakness, it is customary to find pressure relieving devices or safety discs installed downstream of self-acting pressure regulators to safeguard equipment from over pressure. Self-acting Temperature Regulators In Fig. 10.2 the diaphragm motor is replaced by a bellows motor in which the vapor of a fluid in a temperature sensitive bulb exerts its pres sure. The bulb contains a liquid such as ether or alcohol. The tem perature sensitive bulb is located in a tank or vessel which is to be temperature controlled. The heating medium for the vessel passes through the automatic valve as the fluid pressure inside of the bulb in creases because of an increased temperature. The pressure in the bel lows motor will gradually close off the valve. This action reduces the rate of heat input to the system and in that way the temperature is regulated. As in the case of the pressure regulator a failure of the thermal system will cause the valve to fail in the wide open position be cause of the action of the spring. These regulators with valve plugs on top of the valve seats are used on heating service. This points up the similar rule--all self-acting temperature regulators on heating service fail in the open position which is the unsafe position. For cooling service the same instrument is used by reversing the .tk Instrumentation for Safe Operation 135 action of the valve. The plug is on the underneath side of the seat instead of the top side. A failure of the thermal system will cause the spring to close the valve, in which case the coolant is shut off. There fore, self-acting temperature regulators for cooling service fail in the unsafe position. Because of the inherent weakness of self-acting tem perature regulators some external temperature switch is required in order to protect vessels from overheating. There are self-acting tem perature regulators on the market which feature "fail-safe" design. This is because the fluid chosen for the bulb operates in the vacuum range. This is unsatisfactory because of the limited available power for the movement of the valve stem. One other disadvantage of the self-acting temperature regulator is that the temperature is not con trolled very closely. Temperature regulators Heating service Fail open Cooling service Fail closed etc 03164 136 Safety and Accident Prevention in Chemical Operations Temperature and pressure controllers fail open or closed Closed-tube systems never fail safe. Relieving devices or temperature switches often required. FIG. 10.3. The Pneumatic Controller The need for closer control of temperature usually justifies the instal lation of an instrument such as in Fig. 10.3. This is a temperature controller wherein the internal bourdon tube is connected to a tem perature-sensitive bulb, and becomes a pressure controller when the in ternal bourdon tube is connected directly to a pressure vessel or pipeline. In this particular instrument the sensitivity, proportional band or throttling range (these terms are synonymous), can be easily adjusted to suit the process. Furthermore, the action of the controller can be easily changed so as to use normally open or normally closed diaphragm motor valves as shown in the sketch. Many believe this arrangement constitutes a fail-safe system because the control valve can be chosen to fail open or closed, but it is not. The control valve fails safe only in the event of an air supply failure. However, a failure of the thermal element will result in the pointer falling to the lower end of the temperature scale. This makes the instrument think the temperature is too low, so the action of the controller will then be to cause the valve to open wide regardless of the action of the valve. Therefore, the normal closed-tube temperature systems likewise never fail safe. However, it is now possible to buy completely fail-safe Instrumentation for Safe Operation 137 temperature controllers at an additional cost. A piece of invar inside of the thermal bulb causes the fluid pressure to drop on a rise in tem perature, which is the reverse action of the conventional system just described. Under this condition, when the tube system fails the pointer moves up-scale. In this way the instrument thinks the system being controlled is too hot and the control valve will be automatically closed. This particular controller is advantageous on small process vessels which are easily overheated; that is, small in relation to the rate of heat input. The Potentiometer Controller A temperature controller of the electric potentiometer or wheatstone bridge type in Fig. 10.4 is more commonly used in process control. They are generally considered the safest because on a failure of the primary element the pen moves up scale. Upon an electrical failure the pen stops moving. If the pen happens to be above the control point at the time of electrical failure, the controller fails safe. If the pen is below the control point at the time of electrical failure, the controller fails in the unsafe position. This is especially true on those control lers with automatic reset. Again, the engineer has the choice of using a normally open or normally closed valve depending upon which is the Electrical temperature controllers sometimes fail safe On failure of primary element Pen goes upscale FIG. 10.4. ETC 03166 ETC 03167 Instrumentation for Safe Operation 139 Level indicator with alarm r Float type ____dh. I Micro 1 switch Figure 10.6 illustrates another version of a float operated level gage. This type of level gage is accurate and quite dependable. For this reason, it is generally advisable to attach the level switch alarm to it. Bubbler-Type Level Gages The lower part of Fig. 10.6 shows the bubbler-type level gage. The back pressure in the dip pipe which motivates the U tube manometer for liquid level measurement can also be used for actuating an ordinary pressure switch. A contactor manometer shown in the lower half of Fig. 10.6 is used to indicate liquid level and to provide switch action. ETC 03168 140 Safety and Accident Prevention in Chemical Operations Level controller with alarm Level transmitter i Pressure switch must be connected to the pneumatic measurement, not the controller. FIG. 10.7. Tungsten probes are adjusted down into the mercury. The motion of the mercury will either close or open the electrical circuit which will actuate other devices as required. The mercury U tube contactor ma nometer, while inexpensive, cannot be made explosion proof. Displacer Type Level Controllers Another type of level alarm is usually associated with level con trollers. This type of level controller, shown in Fig. 10.7, is the dis placer type. A metal weight is suspended in a liquid in which the level is to be controlled. The instrument measures the change in weight of the displacer as the liquid level changes. The output pressure of such a level controller is 3 to 15 psi, which is the standard pneumatic signal range. Regardless of how the level is measured, it is important to recognize that the pressure switch should be connected to the transmit ter signal as shown in Fig. 10.7. Sometimes engineers have been known to connect the pressure switch to the output of the controller on a simple level control with adjustable proportional band only. The disadvantage of this method is that switch action will occur when the process requires very high or very low flows through the control valve. This results in false alarms. The advantage of the system as shown FTC 03169 Instrumentation for Safe Operation 141 in Fig. 10.7 is that the pressure switch is actuated only as a result of a liquid level change and not because the control valve became closed or wide open. If the pressure switch for high and/or low level alarm is connected to the transmitter signal to the controller there will never be false alarms. Therefore, the rule associated with level controllers is always locate the pressure switch on the transmitted measurement signal and not on the control valve pressure. Alarms on Recording Controllers Figure 10.8 is a picture of any controller scale. The shaded portion represents the normal control band and the heavy black marks indicate the low and high alarm. If the controller can be depended upon to hold the measurement within the limits of the shaded portion, then alarm contacts would serve a useful purpose if their settings were made just outside the normal control band. This method is generally accepted in practice among the industry today, because it usually provides adequate advance warning of system failure. Alarms on Multipoint Recorders Figure 10.9 illustrates a conventional multiple point recorder. These are most widely used for temperature measurements where the thermo couple or resistance bulb becomes the primary element. It is possible to have selected temperature alarms even on a multiple point recorder. The circuit consists of a terminal board, selector switch, print switch, Alarm contacts for round chart instruments Control point 0 |1 | l j20 i | l 1 Low alarm --^ 41 0 '4} 60 80 MM i 1 Indicating ^High alarm pointer 100 i| - / Normal control band FIG. 10.8. ETC 03170 ETC 03171 Instrumentation for Safe Operation 143 Applications of solenoid valves FIG. 10.10. 3 way solenoid valves FIG. 10.11. 144 Safety and Accident Prevention in Chemical Operationt Solenoid Valves Some applications of solenoid valves are shown in Fig. 10.10. It is assumed that on air failure the control valve is to be held in the last position before the air failure. A two-way solenoid valve connected to a pressure switch in the air line will accomplish this purpose. Figure 10.11 illustrates the use of three-way solenoid valves. Of course, three-way solenoid valves can easily be made into a two-way solenoid valve merely by plugging off the third port. In this partic ular application the control valve can either be vented upon failure, or by using a pressure regulator the control valve can be moved to any preset position between wide open and fully closed merely by set ting the pressure regulator at the desired pressure. Solenoid valves can be actuated by other process controls, master shutdown devices, and other devices, upon loss of agitation, pump failures, or even fire alarms. 10.1. ANNUNCIATORS When an instrument engineer considers alarms for shutdown de vices he usually thinks of three basic design premises: 1. All the critical points of operation should be protected by alarms and/or shutdown devices. 2. The device should fail safe. 3. Field testing should be simple. An annunciator is a device which calls the operator's attention to the fact that something has gone wrong. This is usually accomplished by an audible and visual alarm. Horn and Light Annunciator The simplest and most elementary annunciator system is the one that is shown in Fig. 10.12. An alarm contact such as a pressure switch, temperature switch, or contact inside an instrument (any contact that signifies an unsafe condition or act) will close, and upon closing a light will go on and the horn will sound. The disadvantages of such a sys tem as this are quite obvious. A contact which is normally open will eventually become corroded or dirty and probably cannot be depended upon to function when it should. It is impossible to turn off the horn in the event the alarm is sounded. The horn will not stop blowing ETC 03173 ETC 03174 146 Safety and Accident Prevention in Chemical Operations Annunciator with Manual "Stop Horn" Button and Automatic Reset Figure 10.14 illustrates how to overcome this disadvantage by using a relay and a push button. Again the alarm contact which closes up will actuate the horn and light in the same manner; however, after the operator acknowledges the alarm, all he must do is manually push the normally open momentary contact push button and the relay does the rest. The advantage of this system is that when the unsafe con dition has been corrected the alarm system automatically returns to the original condition so that the horn will sound on the next occasion. The operator does not have to remember to turn the alarm back on. Annunciator with a Flasher for the Light Figure 10.15 shows a further improvement, in that we now have a flasher to signify which is the new alarm to come in, instead of the light just burning steady bright when there is an alarm condition existing. When the operator desires to silence the horn when a new alarm comes in, he merely pushes the push button as in the former case. The relay not only de-energizes the horn, but it also causes the light bulb to burn in the steady bright condition. This is called the pending or the ac knowledged position. This is a distinct advantage when there are several lights on a board in a concentrated area. The disadvantages are still the same however, namely, that this alarm is good only for Manual silencing of horn with automatic reset FIG. 10.14. iwbi Instrumentation for Safe Operation 147 Automatic reset with flasher Normally open or closed contacts FIG. 10.16. ETC 03176 148 Safety and Accident Prevention in Chemical Operations normally open contacts, and the use of the horn is still limited to one alarm. Annunciators which can be Actuated by either Normally Open or Normally Closed Field Contacts Figure 10.16 shows the use of the normally open or normally closed actuating contacts. Another relay is required to do this job. The advantage of using normally closed actuating contacts lies in con tinuous monitoring of the contacts, connecting wires, and alarm relays. A failure of any part of this circuit will result in an alarm, and at least a false alarm is better than no alarm at all. The action of the re mainder of the alarm system is identical to Fig. 10.15. In the ac knowledged position the light burns steady bright, and the horn is off. When the unsafe condition has been corrected the relays all return to their normal position ready for the next alarm. The chief disadvantage of this system is the high initial cost (between $300 and $400) and high maintenance cost. For several units space requirements for the elec trical gear present a major problem in plant design. Maintenance of faulty contacts is also costly. The Unitized Annunciator The annunciator which is shown in Fig. 10.17 overcomes all the disadvantages presented thus far. It is called a unitized annunciator and is manufactured by several reputable manufacturers. The "A" and "B" relays are contained in one hermetically sealed can in an atmosphere of nitrogen. The relay cans are plugged into a conventional radio socket. Under normal operating conditions both relays are energized. Since the normally closed actuating contacts are recom mended, the contact, connecting wire, and the relays are completely monitored. This is a completely fail-safe annunciator. It features a stop horn and acknowledge push button, same as before, and also a test push button so that the operator may test the alarm. The circuits preferred generally are circuits in which both light bulbs are connected in parallel. This means that there is an installed spare bulb. The plug-in relay can with the two lights mounted on it is located behind a translucent white plastic nameplate with black letters engraved upon it. Several such units are arranged in rows in cabinets. When the alarm comes in, the lights will be flashing while the horn sounds. The operator can read the engraving at a considerable distance. This permits location of the annunciator on top of the panel board rather Instrumentation for Safe Operation 149 The unitized annunciator Ri Ci no flasher is used FIG. 10.17. Lights than in the panel board which consumes valuable board space. The cost of each plug-in relay and flasher is around $38 to $40 each. One horn now serves a whole cabinet. Additional relays are connected to the six bus bars shown by merely plugging them into spare sockets of the prewired cabinet. One may easily purchase 100 or 200 such units ETC 03178 150 Safety and Accident Prevention in Chemical Operations all in one cabinet and still use only one horn and only one flasher. The installed cost per point is reduced from $300 or $400 down to about $5o per point. The use of hermetically sealed relays and flashers is the answer to the corrosion problems that are found in the chemical plants. The advantages of the unitized annunciator are: low initial cost and low maintenance cost. Over a period of two years, one plant has experi enced only around six relay failures in several hundred units. The re lays are hermetically sealed in nitrogen which eliminates oxidation, corrosion, and accumulation of dirt on the contacts. Identity of trouble is quick and accurate. It consumes no more than 70 milliamps of cur rent. The use of the horn is unlimited. It is versatile. Over 100 cir cuits are available in this universal circuit shown in Fig. 10.17. An other circuit arrangement that is available is a momentary "lock-in" feature which is used with momentary type alarms. Auxiliary contacts are available. The name plates are back lighted but turret lenses or bulls-eye lights are available with the basic universal plug in relay. The flasher and test button are optional features. To change circuit arrangements it becomes necessary only to change jumper wires. It is possible to add counters to this system so as to count or totalize the number of times each alarm relay is actuated. For an additional cost another device may be installed which tells the first alarm to go off in a given series. The choice of dim lights or low lights for the normal position also is optional. 10.2. INTERLOCKS High-Level Interlocks Interlocks are really controls for safe operation. In the event of a serious process upset the interlock does something about it in addition to warning the operator of danger. Figure 10.18 shows an interlock for high level. A float switch on top of a tank can be easily interlocked with a pump which pumps the material into the tank in order to pre vent spills or overflows of that tank. The way in which it is accom plished is shown in the lower section of Fig. 10.15. Notice that the control voltage is limited to 110 v. Since most motor voltages are 440 v, three phase, it is merely necessary to install a small 4 to 1 step-down transformer inside the magnetic starter box in order to obtain the 110 v required for the system. The normally closed contact of the level controller or level switch is connected in series with the stop circuit of the magnetic starter. Instrumentation for Safe Operation 151 Some common interlocks 440V 30 /--------------- '---------------\ Prevention of Operating Errors Figure 10.19 shows one versatile method of preventing operating errors. Let us assume that this process calls for the sulfonation of an organic material in three batch sulfonators. Oleum is measured out in a weigh tank for each batch. In operation the valves are lined up to the proper sulfonator. Full cooling is applied to the sulfonator. The temperature is controlled either manually or automatically by the rate of oleum addition until the oleum weigh tank is empty. It is not un usual to make an operating error by leaving a valve open on another 152 Safety and Accident Prevention in Chemical Operatiom Prevention of operating errors Reactors FIG. 10.19. sulfonator. In many cases such an error is hazardous as well as costly in wasting valuable chemicals. To prevent this kind of error, it is necessary first to mount a lever switch on each of the three cocks. On each switch will be mounted three mercury bottles. In practice there will be the same number of bottles mounted on the shaft on each lever switch as there are cocks which are included in the interlock system. These 4-amp bottles are arranged as shown in the electrical drawing, and the bottles are all shown when the cocks are in the closed position. Assuming it is desired to sulfonate #1 sulfonator the cock to it is opened and when it is open, current will automatically flow through the first circuit through the solenoid valve. However, if any one of the other cocks are opened, the flow of current to the solenoid valve will be interrupted. This causes the oleum flow to be shut off by vent Instrumentation for Safe Operation 153 ing the diaphragm motor of the normally closed control valve. This technique is being used at the present time with very good results with negligible maintenance. Agitation Failure Another common interlock is known as agitation failure protection. It is designed to prevent accidents which can occur in many chemical reactions when agitation ceases. Since the agitator shaft or the gears can break off, a measure of the current flow to the motor can be used to detect loss of agitation. A current sensitive relay or current switch is connected in series with one wire which is connected to the motor. On large motors a current step down transformer is inserted here and the relay is connected to the secondary of the transformer. The switch is set when the liquid level is about y:i of normal. At higher levels, more than enough current will keep the relay energized. A drop in current below the set point will de-energize the relay. A typical wiring diagram is shown in Fig. 10.20 using a three-way solenoid valve in the control air line to the diaphragm motor valve. Upon loss of agitation the current switch de-energizes the solenoid valve which in turn vents the diaphragm of a normally closed control valve. This shuts off the flow of chemicals to the reactor to prevent an explosion. The switch action can also be used to actuate an annunciator system and perform other jobs as required by safety considerations. Miscellaneous Interlocks Other interlocks include temperature and temperature differential, pressure and pressure differential, liquid level, flow, pH, conductivity, density, and analyzers. All of these interlocks or contacts can be made to shut down pumps, blowers, vacuum jets, or other parts of processes. Interlocks can be used to shut off steam, natural gas, cooling water, or fluid flow or to vent vessels. In summarizing, remember to use normally closed actuating con tacts whenever practicable. Of course this cannot be done in the case of multipoint temperature recorders because of the cyclical nature of a multipoint instrument. Select valves which fail safe, employ nor mally energized circuits, provide for easy start up; use timers if neces sary, protect all the critical points of operation. Do not over instru ment processes. Avoid high-control voltages in alarm systems and do not mix up voltages as this practice may cause electrical difficulties. Avoid temporary wiring and exposed terminal boards. Limit the use 154 Safety and Accident Prevention in Chemical Operations Agitation failure of plant air on alarms; never use sprinkler air. Avoid bypasses when ever possible or practicable. Do not locate control valves in dangerous areas, and do not forget to put drains in the low sections of piping in order that the entire line may be properly drained when parts of the piping or control valves must be taken down. |i ETC 03183 Design and Inspection of Pressure Vessels DEVELOPMENT OF THE BOILER AND PRESSURE VESSEL CODES1 2 The need for a boiler and pressure-vessel code was demonstrated during the latter part of the nineteenth century and the first decade of the twentieth century when some 10,000 boiler explosions killed an equal number of people and seriously injured 15,000 others. Massachusetts issued the first rules for the construction and instal lation of boilers in 1907 following disastrous explosions in 1905 and 1906. Other states and cities followed the example of Massachusetts and enacted laws or ordinances for the construction, installation, and inspection of steam boilers with resulting chaos. The lack of uni formity in requirements of the different states did not allow a manu facturer to build stock boilers that would be acceptable in other states, second-hand boilers could not be shipped across state lines, and a qualified boiler inspector in one state was not recognized in others. The American Society of Mechanical Engineers was requested to formulate standard specifications for the construction of steam boilers and pressure vessels, and in 1911 a committee, later known as the Boiler Code Committee, was formed. The first ASME Boiler Code was issued in 1914. Since that time 155 ETc 03184 156 Safety and Accident Prevention in Chemical Operations and through 1962 the Boiler Code has been revised 16 times. The first edition of the Unfired Pressure Vessel Code was issued in 1925 and has also been revised 16 times through 1962. The petroleum refining industry has long been a user of large highpressure, high-temperature pressure vessels, and was particularly interested in welded construction for containing flammable liquids and gases. In 1934 a joint ASME-API (American Petroleum Institute) committee issued the first edition of the API-ASME Code for Unfired Pressure Vessels for Petroleum Liquids and Gases. This code was re garded as less conservative than the ASME code as it used a factor of safety of 4 rather than that of 5. There were 5 editions of the code by 1951. The API-ASME Code was discontinued in 1956 in favor of the ASME Unfired Pressure Vessel Code which was being adopted as a legal requirement by an increasing number of states, cities, and provinces. The code gives no definition of a pressure vessel. A pressure ves sel is usually considered to be a closed container of a fluid under pressure used to perform some process function such as a storage tank, heat exchanger, evaporator, or reactor. Code jurisdiction over piping external to the vessel terminates at the first circumferential seam or joint for welding end connections; the face of the first flange for bolted connections; and at the first threaded joint in that type of connection. Paragraph U-l of the Unfired Pressure Vessel Code lists the excep tions from code jurisdiction, however the "Synopsis of the Boiler and Pressure Vessel Rules and Regulations" and the local authority hav ing jurisdiction should be consulted for further details as to require ments and exemptions which may vary widely from place to place. A non-code pressure vessel may be defined as a vessel not meet ing the minimum construction requirements of the code for design, fabrication, inspection, and certification. It could not be stamped with the code symbol and could not be installed in a jurisdiction that had adopted the ASME Code unless some special ruling was in effect. 11.2. THE ASME BOILER AND PRESSURE VESSEL CODE AND THE NATIONAL BOARD OF BOILER AND PRESSURE VESSEL INSPECTORS Those in the chemical industry associated with the procurement and operation of pressure vessels should have a thorough understanding Design and Inspection of Pressure Vessels 157 of the functions and relationship of the ASME Boiler Code Commit tee and the National Board of Boiler and Pressure Vessel Inspectors. For that reason, excerpts from the ASME Code Foreword and the NBBPVI Code of Practice are reproduced here, as being the least known or most frequently overlooked or misunderstood functions of the two organizations. Excerpts from the ASME Code Foreword3 The Boiler and Pressure Vessel Committee's function is to establish rules of safety governing the design, the fabrication, and the inspection during construction of boilers and unfired pressure vessels, and to in terpret these rules when questions arise regarding their intent. In formulating the rules, the committee considers the needs of users, man ufacturers, and inspectors of pressure vessels. The objective of the rules is to afford reasonably certain protection of life and property and to provide a margin for deterioration in service so as to give a reason ably long, safe period of usefulness. Advancements in design and material and the evidence of experience have been recognized. The Boiler and Pressure Vessel Committee meets regularly to con sider requests for interpretations and revisions of the rules. Inquiries must be in writing and must give full particulars in order to receive consideration. Interpretations of general interest are published in Mechanical Engineering as "Code Cases," and inquirers are advised of the action taken. Code revisions approved by the committee are published in Mechanical Engineering as proposed addenda to the code to invite comments from all interested persons. After final approval by the committee and adoption by the ASME Council, they are printed in the addenda supplements to the code. Code cases (interpretations) may be used in the construction of vessels to be stamped with the ASME Code symbol beginning with the date of their approval by the ASME Council. Manufacturers and users of pressure vessels are cautioned against making use of revisions and cases that are less restrictive than former requirements without having assurance that they have been accepted by the proper authorities in the jurisdiction where the vessel is to be installed. After code revisions are approved by council they may be used beginning with the date of issuance shown on the pink-sheet addenda. Revisions become mandatory as minimum requirements 6 months j ; j I ETC 03186 158 Safety and Accident Prevention in Chemical Operations after such date of issuance, except for boilers or pressure vessels con tracted for prior to the end of the 6-month period. The National Board of Boiler and Pressure Vessel Inspectors is composed of chief inspectors of states and municipalities in the United States and of provinces in the Dominion of Canada that have adopted the Boiler and Pressure Vessel Code. This board, since its organiza tion in 1919, has functioned to uniformly administer and enforce the rules of the Boiler and Pressure Vessel Code. The cooperation of that organization with the Boiler and Pressure Vessel Committee has been extremely helpful. Its function is clearly recognized and, as a result, inquiries received which bear on the administration or ap plication of the rules are referred directly to the National Board. Such handling of this type of inquiry not only simplifies the work of the Boiler and Pressure Vessel Committee, but action on the problem for the inquirer is thereby expedited. Where an inquiry is not clearly an interpretation of the rules, or a problem of application or administra tion, it may be considered both by the Boiler and Pressure Vessel Committee and the National Board. It should be pointed out that the state or municipality where the Boiler and Pressure Vessel Code has been made effective has definite jurisdiction over any particular installation. Inquiries dealing with problems of local character should be directed to the proper authority of such state or municipality. Such authority may, if there is any question or doubt as to the proper interpretation, refer the question to the Boiler and Pressure Vessel Committee. The specifications for materials given in Section II of the code are identical with or similar to those of the American Society for Testing Materials as indicated, except in those cases where that organization has no corresponding specification. Excerpts from NBBPVI Code of Practice4 Protection of life and property is the first duty of any government. Many governmental subdivisions in the United States and Canada, recognizing this duty, have adopted mandatory laws requiring that the design, fabrication, and inspection of boilers and unfired pressure ves sels comply with the rules of The American Society of Mechanical Engineers' (ASME) Boiler and Pressure Vessel Code as administered by The National Board of Boiler and Pressure Vessel Inspectors (Na tional Board). The development of rules and codes and the construction of safe tion, is a 3-pronged endeavor: 1. Voluntary co-operation of the ASME Boiler and Pressure Vessel Committee which writes the rules; 2. Boiler and pressure-vessel manufacturers who comply with the rules; and 3. The National Board which issues commissions to inspectors who diligently enforce the rules. Boilers and unfired pressure vessels which meet these requirements in every respect proudly bear the symbols of approval in the form of the ASME and National Board stamps. For a manufacturer to become a fabricator of code vessels he must first apply for the official symbol of the ASME and authorization for its use for a specified period. Form letters for this purpose are included in the Codes as is an illustration of the Certificate of Au thorization. After obtaining the authorization, the manufacturer must make arrangements for shop inspections, either with an in surance company or w'ith the local authority. The ASME Boiler and Pressure Vessel Committee--a voluntary group of engineers organized in 1911--is composed of designers, manu facturers, users, and insurance and inspection authorities, all of whom are interested in developing and maintaining a safety code for boilers and unfired pressure vessels. The National Board of Boiler and Pressure Vessel Inspectors is a voluntary organization of officials who are charged with the enforce ment of boiler and pressure-vessel inspection regulations of any political subdivision of the United States and Canada that has adopted one or more sections of the ASME Boiler and Pressure Vessel Code. The National Board was organized in 1919 for the purpose of pro moting greater safety to life and property by securing concerted ac tion among the states, cities, and provinces; and uniform inspection | practices and consistency in the construction, installation, and inspec- ! tion of safe boilers and pressure vessels. National Board inspectors' ! commissions have been issued to over 2000 men who have met and i maintained the board's high standards of qualification. ! In order to retain the confidence necessary to maintain the integrity j of the codes and the inspection authorities, complete co-operation must j be exercised by all concerned. Any deviation from the codes wouldj tend to discredit them as a safety measure. j ETC 03188 160 Safety and Accident Prevention in Chemical Operations "5 ^ '-5 '-S X TA B LE 11.1. Status of ASME Sections I and V III in the United States ill =1 m iiffii ill 111!fit* I ZZZZZZZZooosuc-: *-5 ^ *** *# *-3 Z iJ * Design and Inspection of Pressure Vessels 161 11.3. SECTIONS OF THE ASME BOILER AND PRESSURE VESSEL CODE Section I Power Boilers Section II Material Specifications Section III Boilers of Locomotives (discontinued) Now Nuclear Vessels Section IV Low Pressure Heating Boilers Section V Miniature Boilers (discontinued) Section VI Rules of Inspection (discontinued) Section VII Suggested Rules for Care of Power Boilers Section VIII Unfired Pressure Vessels Section IX Welding Qualifications 11.4. STATUS OF THE ASME CODE IN THE UNITED STATES AND CANADA5 While much effort has been expended to obtain uniformity in Boiler and Pressure Vessel Laws and Regulations, there still exist wide dif ferences in practice. A chemical industry contemplating construc tion of a plant in another state may obtain information concerning that state's rules and regulations in the Synopsis of Boiler and Pressure Vessel Laws, Rules, and Regulations, published by the National Bu- TABLE 11.2. Status of ASME Code Sections I and VIII in Canada Alberta British Columbia Labrador Manitoba New Brunswick Newfoundland Northwest Territories Nova Scotia Ontario Prince Edward Island Quebec Saskatchewan Yukon Territories Section / VIII LL LL LL AL LL LL LL LL LL LL LL ETC 03190 ETC 03191 Design and Inspection of Pressure Vessels 163 reau of Casualty Underwriters. Tables 21.1, 11.2, and 11.3 are based on the synopsis which gives additional information concerning: Department having jurisdiction and address Date of law Rules of construction and stamping Objects subject to rules Objects subject to field inspection Inspection required Insurance company requirements Certificate of inspection State inspection fees 11.5. BOILER AND PRESSURE VESSEL REQUIREMENTS IN FOREIGN COUNTRIES6 Many chemical industries have or may contemplate foreign manu facturing facilities. Table 11.4 lists the legal standing and administra tion of pressure-vessel codes in various countries. 11.6. THE PRESSURE-VESSEL DESIGNER The ASME Unfired Pressure Vessel Code is not a design manual and does not contain rules to cover all details of design and construc tion. The code covers only the minimum requirements for design, fabrication, and inspection of unfired pressure vessels. Whether these minimum requirements are suitable for a vessel's service conditions or whether more exacting criteria is indicated is the responsibility of the pressure-vessel designer. The importance of design and the views of some pressure vessel designers are contained in references 7 and 8. The design of the many shapes, sizes, and types of pressure vessels used in chemical plants requires the skills of an experienced engi neer specializing in this field. Vessel design requires a thorough knowledge of the code requirements, the properties of the fluid being contained, the properties of suitable materials of construction, and the problems involved in the fabrication of these materials. Design fac tors may be so varied that the engineer can only rely on his engi neering judgment and his experience with similar problems to produce a safe economical design that will last the intended life of the equip ment. Due to space limitations, no attempt will be made here to discuss or interpret the requirements of the pressure-vessel code in detail. T A B LE 11.4. Legal Standing and Administration of Pressure-Vessel Codes in Various Countries ETC 03194 o O > c O a-t =5 1- &s e ba.. Q J5 H J S S > a5 -%a 'Ea> =^> E-I S3 > e. 8 J> *jS s * s ^ 4 4J -O i 3r. &- SD > & | 1a -w . * S' -s j> | I -I * *IIo- .e8s c1s* *5s ^s .B1fi N. 1U , . i .H .1^ -gaS' S2te rZn a h aa BrVf --u O -o .1 'eMs u, *o5 So g 3 23 ^ 8" Q. E a W 55 I2 ^ Q 33 5 ? ? 3A &Cfl. -isa S j S = J55 *5 rs G a .2 -- fe si " 3 -- c ' feC I 1 ! 11 f . 3 d &. I b 3 5 cc3 cS bfi 5^ pj n ^-j3 m t0s "W s gSC -O -42=3*v 2 2 cs j- *v ai wc/3 Z Q "S T3 9 ~ o' * , ! j iSa 9 HP#S a (S 2 fe 5 03 3 iS il|'H " ins a -- s -- 'll9 I ! S3 a. a. Q|hP * > S -3 D a> S | g e -O iMs CL O> <S0 .-;. fc 4 ^ > a a alSfiN5 S| c< J^3 .3 Isi U J ea < H 1 o ETC 03195 registered, and ETC 03196 168 Safety and Accident Prevention in Chemical Operations > S<<o _Ja> 04p55 rCJ> 14u "SZ 3 s< TABLE 11.4 (Continued). Legal Standing and Administration of Pressure-Vessel Codes in Various Countries S I 4 -1 1111 S2 g <3 -2 I- s c -s cO SCO .- Z .5 .1 | -a = ' 1 -S -J 1 1.1 J 3 _ 1C-6c3!Bm1,.,1sVS..I*-s;oSrag.'5 u Pn ^ .S J3 rt 3 -- ~ *O5 '1^j3- -o5q3 3 1 -3 & b <3 ^ c| ^ O5 -- o? is&I| ify 1 S a Z5 gs >*- E ^ -- "5 b5 >gs *$og 5 ..e2 "aS a-5s o35 ^C-* s_, J1 t-^5 o.e- o. o.r z a _ 0055 >- > *3 eog |g =" *| 1 I it 2 < 1a 1< ^& s 13 I J11 s 2S co . j5 800 c =2 *c3.t2> l -cz3j .2^2 *z< -? c js .-* 6 i 5 32fc. C3 2 "j 3 ~ .3 3 acu) --r i 6 E. fe -S J ETC 03198 authority (e.g. Lloyd's) for vessels manu factured outside New Zealand ETC 03199 =a5 .a2 _o mg -= I 3 .1 S g T5 > 5 1 scE Design and Inspection of Pressure Vessels 171 3> a E 11 -~"=5 - ^ *; o"S SS, . *o o .J>5- 2-vo 2 f>oe.".2 B>Cg-. t3 &.a.J< S J 23 e S aSSE.Js^PSc E -sill S. E I f J S 8 .5 i _a -aaa: *?os ----x, c fe o .S > 5 f^t? 2 ^ _ Sw. aaj -Vg < "j S < a> i 1 o fe Z <2 5 O O S iS Z bS, Z M= <o =1 * g s s 1 l"l'l.l tc o < a & -s >i JliJl mil ^_o**33 32aJa T.dS23 M a. E CC 3 a. > CO O `S 2*2cS? i"l?aa'. *pS K^ "B < *i c m a. ->c> -gS * . * m .-2g e J s?s iag>-i2 fco =E5 2 j"Sga < "j-*2 & ^c3 aass g2 C s" *5 >!> * t_3 a^a - MC <r -sSgM.ra't1'5to*^2 oo 5 -M 2o p 5= ETC 03200 ETC 03201 German rules has been prepared but is not yet in force vessels Mechanical Engineers Code ETC 03202 ETC 03203 ETC 03204 176 Safety and Accident Prevention in Chemical Operationt Figure 11.1 illustrates the various features of pressure-vessel construc tion referenced to the applicable code paragraphs. The table of refer ences is arranged by subject for those whose interest may require more detailed information. 11.7. BASIS FOR DESIGN Pressure and Temperature The design pressure is customarily set at 15 psi or 10%, whichever is the greater, over the operating pressure for vessels without cyclic swings. For the latter the design pressure is usually 5 to 10% above the highest pressure anticipated. The design temperature is usually 50F above the maximum temperature that will not result in a de crease of the code-allowable stress which would cause an increase in thickness. For example, a carbon steel vessel operating at 350F should have a design temperature of 650F, not 400F, as the allowable stress is the same for either temperature. If the vessel is code stamped at the lower temperature, and at some future date it is desirable to raise the operat ing temperature, complications arise in having the code stamp changed to the desired increased temperature. For the same reason the vessel should be stamped with the maximum allowable working pres sure based on the nominal thicknesses of the parts rather than the design pressure used to calculate the minimum thicknesses. Minimum Plate Thickness The plate thickness of large-diameter low-pressure vessels is often based on arbitrary plate thicknesses rather than on calculated thick ness based on design pressure. This results in a calculated maxi mum allowable working pressure that may be much greater than the design pressure. The reason for using the heavier plate is that largediameter thin-plate shells are difficult to handle in the shop without spiders or rings to hold the shell sections cylindrical. The purchaser benefits by paying for and obtaining a heavy tank rather than paying for jigs, fixtures, or structural rings. The thicker plate also allows for better fit up. The API-ASME Code specifies that the plate thickness should not be less than (D-100)/1000, where D is the nominal diameter in inches. The minimum plate thickness specified for welded construction by Design and Inspection of Pressure Vessels 177 many organizations is %6 or % in. The code minimum for riveted construction is %6 and %2 in. for brazing or welding of carbon steel. External Pressure or Vacuum Many process vessels operate under external pressure or vacuum or may be accidentally subjected to these conditions. The code specifies that a code vessel occasionally subject to an external pressure of 15 psi or less need not meet the code requirements for construction for external pressure. Consideration should be given to many conse quences before taking advantage of this waiver, such as personnel hazard in event the tank collapsed, cost of replacing vessel, property damage, and hazards, due to release of contents, and value of lost con tents. If at all possible, the use of a vacuum breaker or a seal leg is much cheaper than designing for vacuum. Designing for external pressure is a trial and error affair that has resulted in many unnecessarily expensive vessels. Many times the plate thickness required for internal pressure has been used and stiffener rings added as necessary, when it would have been more economical to increase the shell thickness and eliminate some or all of the stiffeners. Unless the designer has reliable fabrication costs it would be worthwhile to submit several alternates to a fabrication shop for pricing. Selection of Material The selection of construction materials is in most instances a matter of experience. The material that has proved satisfactory in the past under similar conditions is likely to be used again, unless there is a very good reason for changing. When experience is lacking, a number of factors must be considered. Stress Limitations. The material's allowable stress should not re quire excessive thicknesses for the design pressure and temperature: Temperature Limitations. Some materials such as copper and alu minum, and their alloys, and cast iron have specific limitations on temperature (400-450F). Materials Resistance to Corrosion by Process Fluid. The resistance to corrosion that may be expected of a construction material used in a process vessel may be approximated by field tests conducted under identical conditions as those of the vessel's operation. The actual operating corrosion rate and the simulated operating corrosion rate 178 Safety and Accident Prevention in Chemical Operations obtained by laboratory test are often at great variance because of the many unforeseen operational factors. An excellent reference for cor rosion rates is Corrosion Data Survey,s It furnishes information at least as reliable as that obtained by laboratory testing. For new proc esses and with no previous experience under similar conditions, the services of an experienced corrosion consultant would be desirable. Permissible Contamination of Process Fluid by Corrosion Products. While high purity requirements may limit the selection of material it does not necessarily mean that the most expensive material is the best. Where pressure and temperature conditions permit, cladding, glass, rubber, lead, gunnite, or plastic linings may be used rather than expensive alloys. Relative Fabricated Cost of Vessel for Various Materials Considered. It is often desirable and profitable to request alternate proposals from fabricators such as stainless steel versus aluminum and clad material versus solid alloy. Clad material does not always effect the savings anticipated on thicknesses % in. and less. Although the cost of the clad material may be less than that of the solid alloy the cost of fabri cation may be approximately the same for either, with the overall cost remaining about the same. Design of Equipment for Periodic Replacement Rather than for Plant Life. For other than large, complicated vessels difficult to remove, it may be economically feasible to design equipment using less ex pensive metals and replace the vessel after a few years than design the vessel for a 10- or 15-year plant life using an expensive or super alloy. A cost comparison of a vessel fabricated of carbon steel will range to about l1/^ for a low-alloy steel, to around 4 for stainless, and to 10 or more for the more expensive alloys presently in use. In the past a corrosion allowance wras customarily employed in the design of carbon steel vessels. This was usually an arbitrary value added to the calculated minimum thickness, and it was applied in discriminately to all vessels in a unit process regardless of the vessel's importance. Present day techniques in determining corrosion rates by inserting corrosion racks in vessels and pipe lines should result in more realistic corrosion allowances for similar process conditions.10 As the corrosion rates can be predicted more accurately, so may the vessel's operating life expectancy. In specifying material for code-construction vessels either the ASME SA number3 should be used or the complete ASTM A number11 including the year and any suffix such as ASTM-A987-49T. The Design and Inspection of Pressure Vessels 179 ASTM may reissue the specification with a new year and without the tentative (T) with the result that the shop inspector may reject the material as not conforming to ASME requirements. ASME and ASTM Specifications include grades for plate, pipe, tub ing, forgings, and castings with similar chemical and physical proper ties to allow for compatibility or matching of materials. Loadings other than Pressure The vessel and its supports must be designed to accommodate load ings resulting from: weight of vessel and contents weight of internals-trays, baffles, coils, etc. weight of externals-equipment, agitators, exchangers, drums, etc. weight of externals-structures, ladders, platforms, piping weight of externals-dead and live loads weight of insulation and fireproofing wind and earthquake loads In addition to the foregoing, investigations may be necessary as to the effect of reactions due to supporting lugs, ring stiffeners, piping, and thermal gradients that may cause excessive localized stresses. Estimating weights can be tedious and time consuming unless the vessel designer has manufacturers catalogue and reference material, records or tabulated data from previous jobs, and assorted handbooks. The weights of structural shapes may be obtained from Steel Con struction. Lukens Steel Company catalogues Spun Heads or Clad Steel Heads furnish volumes and weights of different types of heads. The weights of flanges, fittings, piping, or valves, can be obtained from any of the suppliers catalogues such as Ladish, Tube Turns, Mid west, Crane, or Taylor. The weights of trays, agitators, exchangers, drums, or other equipment should be obtained from the manufacturer unless the designer has sufficient experience to make an educated guess as to probable weights. For estimating the weight of caged ladders and platforms, 25 lb lineal ft and 50 lb sq ft are fair averages for the weight of steel. Plat forms should be designed for a live load of 100 lb/sq ft if a walkway only, 150 lb/sq ft if a working platform, or 150% of the weight of any equipment the platform may support during turnarounds. The minimum wind load should not be less than that specified by the AISC or 20 lb/sq ft on the vertical projection of the finished structure. 180 Safety and Accident Prevention in Chemical Operations Lacking any local legal requirements the recommended wind pressure may be obtained from the American Standard Building Code ASA A58.1, or if the maximum sustained gust velocity is known it may be determined by an empirical formula developed by the United States Weather Bureau.16 The design of the vessel should be such as to be self-supporting under the combined conditions of wind with vessel full, operating, or during erection. The combination of erection weight and wind is usually the governing condition. In addition to designing the vessel so that the stresses are within those permitted by the code, it is desirable that the deflection of the tower be checked as excessive deflection may upset operation of the top trays, and it is also disconcerting for workmen. Many areas require that consideration be given to earthquake hazard in design. The seismic probability in various localities of the United States has been outlined by the United States Coast and Geodetic Survey (see Fig. 11.2) according to the amount of damage caused by earthquakes in that locality. The areas are designated Zone 0-no damage, to Zone 3-major damage. The seismic coefficients used in design range from 0.02 to 0.20 depending upon the zone and the vibration period of the structure. Data and detailed design procedure for vertical vessels subject to applied forces, vibration, earthquake, and their supports and founda tions may be found in references 12 through 19. To prevent localized stresses due to lugs, brackets, and supports for platforms, equipment, and piping, circumferential rings are often used to distribute the load. These rings may cause excessive sec ondary stresses in the shell immediately adjacent to the ring unless the rings are properly proportioned. The design of these rings and resulting shell stresses are discussed in references 20 and 21. Until recently the effect of piping reactions, moments at vessel nozzles, and the magnitude of the resulting secondary stresses at the shell openings had no satisfactory solution in general usage. The designer usually applied a heavy reinforcing pad around the nozzle with a number of gussets to distribute the.loading around as large an area of the shell or head as he deemed practical. Satisfactory methods have been developed within the past few years for computing the stresses in cylindrical and spherical shells resulting from pipe loads.22'23'24'25 Reference 26 presents the data and formulas of 22 through 25 in readily useable form. This reference26 also gives basic formula for thermal stress calculations at nozzles not readily available in standard texts. F IG . 11.2. Seismic map (U.S. Coast and Geodetic Survey). ETC 03210 182 Safety and Accident Prevention in Chemical Operation* Vessels are insulated for any or all of three reasons, which are to conserve heat, to prevent temperature variation affecting the process and personnel protection, 150F max. The diameter over the insula tion should be used in determining the area on which the wind acts and the weight of the insulation should be used in weight calcula tions. The supports, skirts, saddles, legs, and lugs, of vessels containing flammable fluids are customarily fireproofed with 2 to 4 in. of gunnite or 1 to 2 courses of brick. Vessels over about 4 ft in diameter will be fireproofed both inside and outside of the skirt. As the skirt and base plate usually support the fireproofing and give the vessel greater stability under wind conditions, the weights are included in the cal culations. The effects of wrind pressure and earthquake are seldom figured in ili design as acting simultaneously. Each is figured separately, and the worse condition governs the design. Computation sheets such as those illustrated may be of use but too much dependence should not be placed on them, especially where widely different conditions exist in the design of vessels for a plant. The computation sheets illustrated were prepared for us in the design of vessels in one plant where pressures and temperatures were rela tively low and not cyclic. Earthquake was not a factor and the mini mum thickness specified by the client was 14 in. Unless the form sheets are used judiciously the tendency is to plug in values in the formulas and grind out the answers without due consideration of all the factors that may be involved. Supports The design of supports for other than small tanks, either horizontal or vertical, may be quite complex due to secondary stresses, moments, and shears caused by support attachments. Vertical vessels may be supported by legs, lugs, or brackets, either with or without a ring girder, or a skirt may be used. Large, heavy vessels supported by legs or lugs should have the support reactions at the shell carefully investigated. Methods for analyzing the reactions are given in reference 27. Skirt attachment has been accomplished in a number of ways, but the consensus seems to be to have the skirt and shell outside diameter the same, wdth the skirt butted to head knuckle and welded. This arrangement should not be used for other than el lipsoidal or spherical heads; for flanged and dished heads, the skirt should be fitted to the outside diameter of the bottom head flange and ETC 03211 S K E TC H O U T LIN E OF E Q U IP M E N T SHO W ING P R IN C IP A L D IM E N S IO N S , NOZZLES & SIZES, ETC. Design and Inspection of Pressure Vessels 183 Name of Company Vessel Equip. or Tank_______________ .. No. No. _Req'd J. 0. No Sheet No. Date Comp. By Mat'l, Contents. Operating Pressure___ Vacuum or Ext. Press_ Shell .C.A --------Sp. Gr -psig @F -psig @----------------------F Jacket Mat'l C.A Contents Sp. Gr Operating Pressurepsig @F Vacuum@F Heater coils or lances Mat'l____________________________ C.A_____________________________ Contents_________________________ Sp. Gr_ Type-------------------------------------------- DiaSpacingSq. ft Operating Pressurepsig @F Material. Type. Trays --...... C.A No. Caps. .SizeSpacing. Special conditions FIG. 11.3. Process specifications--vessels and tanks. ETC 03213 Name of CompanySubject-- COMPUTATION SHEET Equip. . No____ J. O. NoSheet No.Date______ Comp. By_ _of_ _C'k'd By_ Shell Diameter(OD)(ID) T.L.-T.LCorr. Allow. = c = Mat'l ASME SAGrType or QualY.S. = If jacketed, jacket design press. = _______________ _psi @F Ext. press, due to full or partial vacuum =_______ _psi @----------------- F Design External Pressure (sum of above) = P -- . _psi @F Min. Des. Temp. -- greater of (max. operating temp. X 1.10) or (max. operating temp. + 50) t = nom. req'd th'k without corr. allow. (I + c) = nom. req'd th'k including corr. allow. Do = outside dia. P = ext. design press. Pa = allowable external press. L = design length of vessel section (See UG-28 and 29) Use chart (Fig. _) Appendix V Check for Pa (or MAPa) with given D0 = t or (< + c) =_____________ L =_______ D--o or ----D---0--t (t + c) L B (from Chart) Pda or M,,A,PDa = --Bt or --B(1--t +--c)- Do L'o *-*0 Check for L with given P = t Do B-^ tl . and Do L - Do = X (from Chart) . with variable l L = DoX tc Stiffening Rings E = mod. of elast. for max. temp, under ext. press, conditions = ------ I = mom. of inertia of ring S I, = req'd mom. of inertia As = cross-sect, area of ring. A and B = Chart factors--Appendix V Do = -Do2 Dff = 14 -Do3 = L A, L t+f PDo B= PD A i 1 w = . _A, = . FIG. 11.5. Pressure. vessels--external pressure--shells. 185 ETC 03214 ETC 03215 Design and Inspection of Pressure Vessels 187 COMPUTATION SHEET J. 0. No_________________ Name of Company Sheet Noof________________________________ Date_____________________ Subject-------------------------------------------------------------- Comp. By______ C'k'd By. Estimated Weights Estimated Corrected Top head Shell Manholes Nozzles Tray support rings Bottom head Sump shell Sump head Weight A Skirt Base plate Weight B Weight C 1. Insulation 2. Fireproofing 3. Ladders and Platforms 4. Trays 5. Liquid on trays 6. Liquid holdup: shell = head 7. Total liquid: shell = heads = 8. Others: piping, reboilers, etc. FIG. 11.7. Pressure vessels--estimated weights. COMPUTATION SHEET Name of Company-------------------------------------------Scbject________________________________________ J. O. No____________________ Sheet No----------------- of------------ . Date___________________________ Comp. By----------C'k'd By_____ _ 'S 5^ 5S EQ ^ g "" e-i II II II II II II II II II Operating Weight @ Base (H ) II II II II II II II II II II Test Weight on Skirt (F) ii ii ii ii n ii ii ag -- co ^ oo Operating & Text Weight @ But. T.L. {E ) Shipping Weight (D ) II ti 11 11 ii II ^ *-i ^ 5 188 ll ll ll n; as o II II II ^CO 00 FIG. 11.8. Weight summary. etc 32i8 -C, 190 Safety and Accident Prevention in Chemical Operationj Name of Company. Subject_____________ COMPUTATION SHEET ------------------------------------------------------------- J. 0. No._ Sheet No.Date_____ Comp. By. C'k'd By Lc @ Base Line = C= 500 500 ai = ,335Ci = .33.ru- Wt. "D" = _____ M @ Base Line = N = No. of anchor bolts Dia. Bolt Circle = Db = AM TM XDb Wt. D Cw iV ----- lbs. -ft. lbs. Tb = Tn -- Cw 4 __IS_ = B 15000 Bolt size (*) =Aa = T = 15000.4 ,, = 15000z____ = 4H = Ax = 1.5* = 1 .ox =__________ S = =4H - 1.5* TS _ x Ma = 8 _ 8 a = 4] M 3333 (F - 1.5*) =4 3333z. t, .4 a 2(Cl - /,) 15 -- (a + ai) t. a 21 FIG. 11.10. Pressure vessels--base ring. 4/(6 + 100 Lt2 Additional Stress in Head used as Stiffener St = 1.25Sa -- Sh (saddles at head) rO Ring Compression in Shell over Saddles--Wear Plates -----------------< --' (t = t, + t,,p) t(b + 100 - 2 Design of Ring Stiffeners ,, KtQ , KtQ? < &v na nZ 2 c Design of Saddles F = KSQ acting .33r below shell S .66S,, Nomenclature Q = load on one saddle (lb) L = tangent length of vessel (ft) .4 = distance from saddle to T.L. (ft) H = depth of head (ft) R = radius of shell (ft) r = radius of shell (in.) t = thickness of shell (in.) (h = thickness of head (in.) b = width of saddle (in.) F = force across bottom of saddle (lb) S1S2S3 = calc, stresses psi KiKtKi = constants S,, = allowable stress psi S,, = yield stress psi Sh = head stress due to int. press, psi E = mod. of elasticity psi Z = section modulus in.3 n = no. of stiff, each saddle a = cross, sect, area each stiff, sq in. 6 = contact angle of saddle with shell On ' thickness of wear plate (in.) ETC 03220 120 0.23 ( A /L -- 0.193) 1500.23 ( A / L = 0,193) 1.171 -- -- 0.700 ___ 0.790___________-- -- ______________________ 0.073 0.0577 0,0353 0.203 0.204 0 ,2 2 8 0 ,2 0 0 ETC 03221 * See F ig . 11.12, w hich plots K i against A / L , fo r values o f A 'i corresponding to values o f A / L n o t listed in table. Design and Inspection of Pressure Vessels 193 F IG . 11.11. Location and type o f support for horizontal pressure vessels on tw o supports. isifc 194 Safety and Accident Prevention in Chemical Operations H/L = 0.10 H/L = 0.05 H/L =0 Values of when R = H H/L = 0 H/L = 0.051 fOvtC H/L = 0.10 fOp,..- - ,dded fillet welded. The effects of securing heads by various methods are discussed in references 28, 29, and 30. Large, horizontal tanks frequently have been supported on three or more saddle supports. This is a hand-down from riveted construc- Ratio -jjFIG. 11.13. Plot of circumferential bending-moment constant X3. ETC 03223 Design and Inspection of Pressure Vessels FIG. 11.14. Leg supports for vertical vessels. tion when it was usual practice to provide a saddle adjacent to each riveted girth seam in an effort to prevent leakage at the riveted seam. Preferred practice today is not more than two supports. The saddles are designed and located so as to utilize the strength of the heads to maintain roundness of the shell, or stiffening rings may be employed. Tanks over 10 ft in diameter and 50 ft long are supported in this manner. See references 31, 32, 33, and 34, Tables 11.5 and 11.6, and Figs. 11.11, 11.12, and 11.13. ETC 03224 196 Safety and Accident Prevention in Chemical Operations igi Heads Pressure-vessel heads may be any of the following which are listed < in order of increasing thickness for a given pressure, diameter, and i material. (The approximate shell thickness t = .06 in./ft diam/ioo psi for an allowable stress of 10,000 psi. 1. Hemispherical 2. Ellipsoidal 3. Conical 4. Torispherical (F and D) 5. Flat (t = y2 shell thickness-approx.) (t = shell thickness-approx.) (t = shell thickness/cos of half apex angle) (t = 1.77 shell thickness-approx.) no simple relationship Hemispherical heads have the best stress distribution of any of the head types, with less material required to contain a given volume. Relatively few fabricators have the forming equipment necessary for producing these heads, and therefore they are not as commonly used as are ellipsoidal heads and flanged and dished heads. Ellipsoidal heads having a major to minor axis ratio of 2 to 1 have a better stress distribution than torispherical, and for pressures over 150 to 175 psi and for diameters over about 5 ft they are usually more economical than the F and D head. Ellipsoidal heads are usually sized by their inside diameter rather than by their outside diameter as are F and D heads. Conical heads are usually formed by pressing, not by rolling or spinning, and they are expensive to fabricate. They are used for di gesters, rendering tanks, or where it is desirable to drain off solids or heavy viscous materials. A truncated conical head is commonly used as a transition piece connecting two different diameters of a vessel. Conical heads without a transition knuckle are permitted by the code under certain conditions, but they should be used only for low-pres sure, low-temperature conditions. The Lukens Steel Company catalogue, Lukens Spun Heads lists 3 types of flanged and dished heads: 1. Flanged and dished heads-Standard 2. Flanged and dished heads-ASME 3. Flanged and shallow dished heads Standard flanged and dished heads have a dished crown radius equal to, or less than, the outside diameter of the head skirt or straight flange, but the transition knuckle between the crown and the skirt has a ETC 03225 Design and Inspection of Pressure Vessels 197 radius of only 3 times the metal thickness. About 30 years ago the code refused further acceptance of heads having these knuckle propor tions following the discovery of many cracked heads, and after several disastrous explosions that were traced to cracks that had developed at the knuckle as a result of the stress intensification at the short radius. These heads are used for atmospheric tanks and should not be used for pressure vessels. The ASME flanged and dished heads have a dished radius equal to or less than the outside diameter of the head skirt or straight flange, and a knuckle radius not less than 6% of the outside diameter of the head skirt but not less than 3 times the metal thickness. The latter provision increases the knuckle radius for thicker heads. When flanged and dished heads are used ASME F and D heads should be specified. Flanged and shallow dished heads have a dished crown radius greater than twice the head diameter, and they more nearly approach a flat or flanged only head. The use of welded flat heads, except for small, low-pressure closures, are seldom justified as, in addition to the extreme thicknesses required, severe discontinuity stresses are introduced in the cylindrical shell. A more satisfactory closure is obtained by a pipe cap or a code head. Bolted on blind flanges are used as manhole or access openings but above 24 in. in diameter, and for high pressures and temperatures it is often possible to save money and effect easier handling by using a formed head attached to a pipe flange. Illustrative of this is that a 6 ft diameter vessel carrying 350 psi required a flat head 12 in. thick weighing 13,800 lb, whereas a 2 to 1 ellipsoidal head ~/s in. thick weighing 1700 lb could have been used (the equivalent of the bolting portions of the closure not included for either type head). Literature on the stresses occurring in pressure vessel heads is ex tensive. Some references are 30 and 35 to 37. 11.8. FABRICATION Pressure vessels may be fabricated by bolting, riveting, forging, casting, brazing, welding, or a combination of any of these. Other than for flanges, bolting has never been used extensively for pressure-vessel construction, although for years the box header for one make of watertube boiler had been bolted to the steam and water drum. Riveted construction is almost a thing of the past, and it is doubtful if more than a handful of shops in the country today still have equip ment for bull riveting a boiler or pressure vessel. Forgings, other than forged fittings, may be used for high-pressure 198 Safety and Accident Prevention in Chemical Operations drums where the ratio of thickness to diameter is high, and it would be difficult to form a cylindrical shell by rolling or pressing. The code has no provision for forging by hammer welding, although this method was used for years in the fabrication of large paper-mill digestors. Castings may be used for unusual shapes. Cast iron has definite pressure-temperature limitations established by the code. Cast steel has no such limitations. Brazing has been used extensively for produc tion of small air tanks for service station use. The code limits the temperature to 406F and the thickness to 1 in. maximum. Many nonferrous materials are brazed. With the exception of a few special cases, practically all industrial pressure vessels are of welded construction. Welding processes are many and consist essentially of brazing, forge welding, gas welding thermit welding, arc welding, induction welding, resistance welding, and flow welding. Pressure-vessel welding is usually either arc weld ing or gas welding and may be manual or automatic. Gas welding may be air-acetylene, oxygen-acetylene, or oxygen-hydrogen. Arc welding covers a wider range as follows: Carbon Electrode Shielded-carbon arc Inert-gas carbon arc Unshielded-carbon arc Unshielded twin-carbon arc Metal Electrode Consumable electrode Nonconsumable electrode (tungsten) Shielded electrode (coated) Submerged arc Inert-gas metal arc atomic hydrogen impregnated tape The most common arc-welding processes used in pressure-vessel fabrication are shielded or coated electric, submerged arc, and inertgas metallic arc. For details of these and other processes consult refer ences 38, 39, and 40. For fabricating pressure vessels by welding or brazing the code requires that the manufacturer qualify the welding or brazing pro cedure to be employed and the welding or brazing operator that will use that procedure in the fabrication of the vessel. Section 9, "Welding Qualifications," of the ASME Boiler and Pres sure Vessel Code details the requirements for qualification of procedure and operators. Although a procedure or procedures may have been qualified for certain welding positions, materials, and filler rod, it may be necessary to requalify if any changes are made. Unless there Design and Inspection of Pressure Vessels 199 is a very good reason the designer should not specify any welding de tails, groove dimensions, or filler metal, that will require the fabricator to change from his qualified procedure and necessitate a new procedure and operator qualification. Qualifying a welding procedure and weld ing operators is expensive. 11.9. INSPECTION AND TEST While the code has requirements for forming, fit-up, and tolerances it is well for the purchaser to have his own inspector in the shop to supplement the code inspector. The code inspector is only concerned that the code requirements are met, and not with location, orientation, and projection of nozzles, installation of internals and other attach ments, cleanliness, or finish. What the code inspector sees he will no doubt report, but vessels have been shipped with certain idiosyn crasies such as a column shipped to the field with all 5 manhole davits, including the hinge, welded only to their respective coverplates. Tol erances that are generally available are shown in Fig. 11.15. Closer tolerances may be specified and obtained but usually at additional cost. For critical service it is often desirable to have more stringent requirements for testing than those presently required by the code, such as ultrasonic testing (now covered by a Code Interpretation Case for plate only), magnetic particle testing, fluid penetrant examination, and helium leak testing. Much time and effort may be saved by ex tracting procedures and acceptability standards from MIL-STD-271 which covers these test methods in detail.41 Similarly, MIL-C-19874 is a convenient reference for cleanliness requirements.42 11.10. CERTIFICATION Upon completion of fabrication and testing of the vessel it is stamped as required by the code in the presence of the code inspector who will also sign the proper ASME form: 1. U-l Mfg. Data Report covering shop and/or field assembly inspec tion, 2. U-1A for single chamber shop fabricated vessel, 3. U-2 partial data report for a part fabricated by one manufacturer for another manufacturer, 4. U-3 data report for vessels that owing to small size are not shop inspected and are certified by the manufacturer and stamped UM. ETC 03229 Design and Inspection of Pressure Vessels 201 202 Safety and Accident Prevention in Chemical Operations The purchaser usually specifies the required number of copies to be finished of: 1. Data forms, 2. Rubbings or facsimiles (photographs are better) of the stamping on the vessel, 3. Stress relief or heat treatments, time-temperature recordings, 4. Pressure recordings, 5. Mill test certificates, 6. Other records pertinent to the vessels fabrication. Similar documents are furnished to the state or other jurisdiction where the vessel will be installed. Future possible difficulties in re locating in another state may be avoided if National Board inspection has been specified and documents sent to their headquarters. 11.11. INSTALLATION When a new vessel has been installed with its necessary piping and appurtenances, such as relief valve, vents, drains, gage glass, and controls, local requirements may require state or local inspection prior to putting equipment in service, or inspection may be made by an insurance inspector in lieu of the state inspection. If the installation is satisfactory a certificate of inspection is issued that is valid for 1 year or 2 years depending on the jurisdiction. Prior to the expiration of the certificate arrangements must be made for removing the vessel from service to permit internal inspection. It is extremely important that the user of pressure vessels have a thorough knowledge of the local laws concerning the installation and operation of pressure-vessel equipment, otherwise he may experience considerable inconvenience and expense. If through ignorance (or contempt) of requirements, equipment is installed and operated with out authorization, the user may be subject to penalties which include shutting down the equipment. This could mean a plant shut down depending on the nature of the installation. After some costly experience a nice degree of cooperation usually exists between the user and the inspection agency whether it be an insurance company, a municipal agency, or a state agency. The inspector is kept informed as to new equipment installation with inspection and certification a matter of routine. Subsequent inspec tions are made without disrupting the plant's operation by notifying the inspector when scheduled downtime occurs, and inspection may Design and Inspection of Pressure Vessels Z03 be made then rather than to wait for the inspection certificate to expire which would require a shut down when it may be least convenient. 11.12. SECOND-HAND EQUIPMENT No statistics are available as to the money wasted on the purchase of second-hand boilers, pressure vessels, heat exchangers, and refrig eration vessels, that are rejected as being non-code or otherwise un acceptable for operation after reinstallation at a new location. Any user contemplating the purchase of second-hand equipment should have the equipment inspected by an authorized code inspector and obtain a written report that the equipment meets the requirements of the jurisdiction where it is to be reinstalled. The report should also furnish sufficient information concerning the condition of the equipment for the user's decision in purchasing. The code inspector will report conditions and make recommendations for repairs, but will not make a recommendation that purchase be made, his function is inspecting, not appraisal. Arrangements for inspection of second-hand equipment can usually be made with the user's insurance company or through his insurance agent. The cost is a per diem charge for the in spector's services plus expenses. 11.13. REPAIRS Nonmandatory Appendix X of the Unfired Pressure Vessel Code covers recommended practices for inspection, repair, and allowable pressure for vessels in service. Further information concerning inspec tion and repair is given in the National Board Inspection Code4 which will guide a code inspector in code jurisdictions. The recommended procedure is for a competent pressure vessel designer to prescribe the nature and extent of repairs to be undertaken together with correct welding procedures, heat treatment, and non destructive testing, that may be required depending on the original construction of the vessel and its present or future intended service. The proposed repair should then be discussed in detail with a code authorized inspector, regardless of whether or not the vessel is under any code jurisdiction. If the vessel is not insured or not under any legal jurisdiction the services of a code inspector may be obtained as outlined in Section 11.12. After the inspector has approved the proposed repair, the work should be done by a reputable fabricator, preferably one listed as authorized under the National Board.4 After witnessing the satisfactory completion of the repair and testing the inspector will 204 Safety and Accident Prevention in Chemical Operations sign the manufacturers Record of Welded Repair to be furnished the governmental unit having jurisdiction. This may appear as an unduly rigorous approach to a seemingly simple problem, but consider, an unauthorized repair in a code jurisdic tion may result in an immediate condemnation of the vessel when the inspector learns of it. At best the inspector will demand removing the vessel from service immediately in order that he may inspect the repair and judge its acceptability. This requires an equipment and possibly a plant shut down. Should the worst happen and a failure causing loss of life occur with resultant public hearings it would be exceedingly difficult to justify the repair. 11.14. HIGH PRESSURE VESSELS Owing to the somewhat ambiguous wording of Paragraph lb of the Unfired Pressure Vessel Code an erroneous conclusion has frequently been drawn that because no specific rules were laid down for vessels carrying over 3000 psi, that such vessels were exempt from any and all code requirements. A proposed revision appearing in Mechanical En gineering, April, 1962 reads as follows: UXFIRED PRESSURE VESSELS, 1959 Paragraph U-l(b), revise to read: The rules of this section of the Code have been formulated on the basis of design principles and construction practices applicable to vessels de signed for pressures not exceeding 3000 psi. For pressures above 3000 psi, deviations from and additions to these rules usually are necessary to meet the requirements of design principles and construction practices for these higher pressures. Only in the event that after having applied these additional design principles and construction practices the vessel still complies with all of the requirements of the Code may it be stamped with the Code symbol. The design of a high-pressure vessel is, as it should be, usually done by an organization or individual with long experience in this highly specialized field. Pressure, temperature, nature of process, and whether hydrogen embrittlement must be considered will influence the material selection and may determine which of the various theories is to be used in computing thicknesses. The theories that may be considered in high-pressure vessel design are: Maximum principal stresses theory (Lame) Maximum strain theory (Clavarino or ICC) Maximum strain energy theory Maximum shear theory Design and Inspection of Pressure Vessels 205 The maximum principal stress theory (Lame) is ordinarily used for pressures around 3000 to 5000 psi and the maximum strain energy theory for higher pressures. The vessel may be made of two half shells hot formed and welded together, a turned and bored forging, or a number of concentric, thin shells making a composite heavy wall. The heads may be formed hemispherical, ellipsoidal, or flanged. In order that material thicknesses may be reduced, it is desirable that the inner material of the shell be in compression, which is ac complished by prestressing. This is done in multilayer construction by each successive shell compressing its inner shell. Solid shells are prestressed by overstraining hydrostatically. Extensive literature is available on the design of high-pressure ves sels. See references 43 through 51. REFERENCES 1. History oj The Boiler Code, American Society of Mechanical Engineers, New York, 1955. 2. The ASME Pressure Vessel Code--A Joint Effort for Safe Construction, E. 0. Bergman, C. F. Braun Co., Los Angeles, 1954. 3. The ASME Boiler & Pressure Vessel Code, 1962 Edition, "Section I. Power Boilers." "Section II. Material Specifications," "Section VIII. Unfired Pressure Vessels," "Section IX. Welding Qualifications," "Code Case Interpretations," American Society of Mechanical Engineers, New York. 4. Code of Practice for the Boiler and Pressure Vessel Industry, 1961; National Board Inspection Code, 1956; Rules for Repairs of Power Boilers and Vnfired Pressure Vessels, 1956; National Board Requirements for Inspections and Stamping, and List of Manufacturers Authorized under the National Board, 1963; National Board of Boiler and Pressure Vessel Inspectors, Columbus, Ohio. 5. Synopsis of Boiler and Pressure Vessel Laws, Rules, and Regulations, 1960; National Bureau of Casualty Underwriters, New York. 6. J. F. Lancaster, "A Comparison of United States, European, and British Com monwealth Codes for the Construction of Welded Boilers and Pressure Vessels," ASME Paper 61-SA-40 (1961) Engineer, 211, 5479, pp. 122-125 (January 27, 1961). 7. Walter Samans, "Importance of Design to Tanks and Pressure Vessels," Weld ing Journal, 29, p. 7 (January, 1950). 8. J. J. Murphy, C. R. Soderberg, Jr., D. B. Rossheim, "Considerations Affecting Future Pressure Vessel Codes," ASME Paper 56-MET-4 (1956); Similar article in API Proceedings, v35, Sect. 3, pp. 258-279 (1955); Discussion in Welding Research Council Bulletin Series, v27, pp. 10-31 (May, 1956). 9. Corrosion Data Survey (1954), G. A. Nelson, Shell Development Corp., Emoryville, California. 10. H. H. Uhlig, Corrosion Handbook 1948, pp. 1052-1058, John Wiley and Sons, New York. aagaaMtoiii.' nwmm 206 Safety and Accident Prevention in Chemical Operation* 11. Material Specifications Part I-Ferrous Metals, 1961; Material Specifications Part 11-Non-Ferrous Metals, 1961; American Society for Testing Materials Philadelphia. 12. S. M. Jorgensen, "Pressure Vessel Design Calculation," Pet. Ref., 24, pp. 10d113 (October 1945). 13. E. 0. Bergman, "The Design of Vertical Pressure Vessels Subject to External Forces," ASME Paper 54-A-104 (1954), paper not otherwise published. 14. Raymond C. Baird, "Aerodynamic Vibration of Tall Cylindrical Columns," ASME Paper 58-PET-4 (1958), paper not otherwise published. 15. C. E. Freese, "Vibration of Vertical Pressure Vessels," ASME Paper 58-PET13 (1958); ASME Trans., J. Eng. for Industry, 81, Ser. B, No. 1, pp. 77-86 i February 1959). 16. V. O. Marshall, "The Design of Foundations for Stacks and Towers," Pet. Ref., 22, 8, p. 251 (August, 1943). 17. Minimum Design Loads in Buildings and Other Structures, ASA-A58-1, American Standards Association, New York (1955). 18. Uniform Building Code, Pacific Coast Building Official Conference, Los Angeles, California (1952). 19. Lateral Forces of Earthquake and Wind, Am. Soc. of Civil Engrs., Proc. v77, Separate n. 66 (Apr. 1951) 38 pp. ASCE Vol. 117, 1952. Disc, in Am. Soc. of Civil Engrs., Proc. v78, Separate n. D-66 (May 1952) 26 pp. 20. Raymond J. Roask, Formulas for Stress and Strain, 3rd ed., Chapters 8 and 12, McGraw-Hill, New York (1954). 21. F. W. Catudal and R. W. Schneider, "Stresses in a Pressure Vessel with Cir cumferential Ring Stiffeners," Welding Journal, 36, 12, p. 550S-552S (Dec., 1957). 22. P. P. Bijlaard, "Computation of Stresses from Local Loads in Spherical Pres sure Vessels or Pressure Vessel Heads," Welding Research Council Bulletin, Series No. 34 (March 1957). 23. P. P. Bijlaard, "Stresses in a Spherical Vessel from Radial Loads Acting on a Pipe," pp. 1-130; "Stresses in a Spherical Vessel from External Moments Act ing on a Pipe," pp. 31-62; "Influence of a Reinforcing Pad on the Stresses in a Spherical Vessel under Local Loading," pp. 63-73; Welding Research Council Bulletin, Series No. 49 (April, 1959). 24. P. P. Bijlaard, "Stresses in Spherical Vessels from Local Loads Transferred by a Pipe;" "Additional Data on Stresses in Cylindrical Shells under Local Load ing;" Welding Research Council Bulletin, Ser. 50 (May, 1959) pp. 10-50. 25. E. O. Waters, "Theoretical Stresses near a Circular Opening in a Flat Plate Reinforced with Cylindrical Outlet," Welding Research Council Bulletin, Ser. 51 (June, 1959); also J. Eng. for Power, 81, Ser. A (April, 1959), pp. 189-200; D. W. Hardenbergh, "Stresses in Contoured Openings of Pressure Vessels," Welding Research Council Bulletin, Ser. 51 (June, 1959), pp. 13-24; C. E. Taylor, N. C. Lind, and J. W. Schweiker, "A Three-dimensional Photoelastic Study of Stresses around Reinforced Outlets in Pressure Vessels," Welding Research Council Bulletin, Ser. 51 (June, 1959), pp. 26-40; F. S. G. Williams and E. P. Auler, "Unreinforced Openings in a Pressure Vessel," Welding Research Council Bulletin, Ser. 51 (June, 1959), pp. 42-46. 26. Tentative Structural Design Basis for Reactor Pressure Vessels and Directly Associated Components, U. S. Dept, of Commerce, Office of Technical Services PB 151987 (December, 1958). ETC 03235 Design and Inspection of Pressure Vessels 207 ; 27. F. E. Woloscewich, "Supports for Vertical Pressure Vessels, Part I," Pet. Ref., i 30, 7 (July, 1951), pp. 137-140; "Part II," 30, 8 (August, 1951), pp. 101-108; "Part III," 30, 10 (October, 1951), pp. 143-145; "Part IV," 30, 12 (December, 1951), pp. 151-153. 28. X. A. Weil and J. J. Murphy, "Design and Analysis of Welded Pressure Vessel Skirt Supports," ASME 58-A-153 (1958), J. Eng. for Industry, 82, Ser. B, 1 (February, 1960). pp. 1-14. 29. J. T. McKean and G. P. Eschenbrenner, "Thermal Analysis and Design of Intermediate Heads of Pressure Vessels," ASME 58-PET-32 (1958), not other wise published. 30. R. G. Sturm and H. L. Obrien et ah, "Stresses in Head to Shell Junction of Pressure Vessels," Welding Journal, 29 (June, 1950), pp. 285-292. 31. Herman Schorer, "Design of Large Pipe Lines," ASCE Trans., 97, pp. 101-119; Discussion (paper no. 1829) 1933, pp. 120-191. 32. A. C. Barton, "Design of Ring Girders for Horizontal Tanks," Pet. Ref., 33, 6 (June, 1944), pp. 207-218. 33. O. L. Garretson and Harry R. Ziegler, "Design of Concrete Piers for Horizontal Storage Tanks," Pet. Ref., 33, 6 (June, 1944). pp. 207-218. ( 34. L. P. Zick, "Stresses in Large Horizontal Cylindrical Pressure Vessels on Two Saddle Supports." Weld. Jour., 30, 9 (September, 1951). pp. 435S-445C. i 35. "Report on the Design of Pressure Vessel Heads," Welding Research Supple ment (January, 1953); Welding Journal, 32, 1, pp. 31S-41S; Appendix (Janu ary, 1953), pp. 41S-52S. 36. G. W. Watts and H. A. Lang, "The Stresses in a Pressure Vessel with a Flat Head Closure." ASME Transactions, 74, 6, pp. 1083-1090; discussion (August, 1952), pp. 1090-1091. 37. G. D. Galletlv, "Torispherical Shells--A Caution to Designers," ASME Trans actions, J. Eng. for Industry. 81, Ser. B, 1 (February, 1959), pp. 51-62; G. D. Galletly, ASME 59-A-163, 1959, Welding Research Council, Bulletin Series No. 54 (October. 1959) p. 9. 38. Welding Handbook, Section II, American Welding Society (1953). ! 39. R. D. Stout and W. D. Doty, Weldability of Steels, American Welding Society (1953). 40. O. H. Henry and G. E. Claussen, Welding Metallurgy, 2nd ed. revised by G. E. Linnert (1949). 41. Xon-destructive Test Requirements for Metals, MIL-STD-271, Bureau of Ships. 42. Cleaning Requirements for Nuclear Primary Cooling, Equipment MIL-C19874, Bureau of Ships. 43. S. J. Jorgensen, "Overstrain and Bursting Strength of Thick Walled Cylinders," ! ASME 57-PET-4 (1957), Pet. Ref., 37, 2 (Feb., 1958), pp. 163-169. 44. S. M. Jorgensen, "Overstrain Tests on Thick Walled Cylinders," ASME 59 PET-1 (1959), J. Eng. for Industry, 82 (Series B) No. 2 (May, 1959), pp. 103121. 45. S. M. Jorgensen, "Reduce Thickness by Overstrain," Pet. Refiner, 37, 2 (February, 1958), p. 163. 46. R. W. Schneider, "Chart Compares Vessel Design Theories," Chem. Eng., 63, 1 (January, 1956). p. 218. 47. R. R. Maccary and R. F. Fry, "Design of Thick Wall Pressure Vessel Shells," Chem. Eng., 56, 8 (August, 1949), pp. 124-127. ETC 03236 ETC 03237 12 Safety Education and Training M. A. Gimbel 12.1. TRAINING OF PERSONNEL (Management, Supervision, Worker) Education may be said to deal primarily with broadening knowl edge and understanding, while training deals primarily with the de velopment of skill in performance. Both are needed to develop safe work techniques and practices. One of the problems in industry is establishing suitable communica tion. Information must pass from top management through the super visor to the man on the job. In reverse, word from the worker must reach to top management. After management recognizes the need for accident prevention, and takes steps to get willing cooperation from all men under its direction, it is prepared for a training program. Undoubtedly motivation is a factor in directing and controlling activities of people. Employees will work hard and will have regard for quality, for courtesy, and for safety if they have reason to think they will benefit from so doing. Since production, which includes safety, quality, scheduling, ef ficiency, and employee relations, is implemented largely through ef forts of foremen and other supervisors it is essential that they receive training to increase the all-around productivity of their departments. After foremen and supervisors are properly trained it is their responsi bility to see that their subordinates are trained and motivated in the pride of achievement, safe practices, and good workmanship. 209 210 Safety and Accident Prevention in Chemical Operations Employee Training Procedures Some form of systematic training of employees is necessary in order to have work done efficiently and safely. This is a definite re quirement even though employees are carefully selected, have aptitude, and have experience for the jobs assigned. Training may be given by the foreman or supervisor responsible for the job. Management in large plants is finding it desirable to have training specialists for the general training and to set up a procedure so that training can be done by the best qualified persons in the plant. The specialist prepares the training manuals and other details for conducting the program and supervises the activity in the individual departments. In chemical plants as well as general manufacturing companies, two methods are followed. VESTIBULE INSTRUCTION This is a plan to teach specialized, general, or advanced techniques peculiar to the industry before the employee actually starts work. Thus it precedes "on-the-job training." Accident prevention is in cluded in all instructions, particularly when new or unusual hazards are characteristic of the job. On-The-Job Training Job training acquaints the employee with a new job or teaches him additional skills. Usually the department supervisor or some one designated by him takes the time to train whenever it is required. This applies to new operations, new employees, and changes in meth ods and equipment. A changed job is considered a new one and some breaking-in is required. A good instructor is friendly, sincere, patient, has a thorough work ing knowledge of the job to be taught, and knows the principles of teaching. He should have the ability to break down the job into its component steps, use an outline for each assignment, and follow a step-by-step analysis of the job. Job Instructor Training During World War II the government realized the need of improved training in industry and sponsored the Job Instruction Training Safety Education and Training 211 courses known as J.I.T. The same basic principles are appropriate today. HOW TO GET READY To instruct a new worker or an experienced one on a new job: Have a Plan How much skill you expect him to have, and how soon. Analyze the Job List principal steps. Pick out the key points. Have Everything Ready The right tools, equipment, and materials. Have the TForA: Place Properly Arranged Just as the worker will be expected to keep it. Step 1--Prepare: HOW TO INSTRUCT Put him at ease. Find out what he already knows about the job. Get him interested and anxious to learn the job. Step 2---Present: Tell, show, illustrate, and question carefully and patiently. Stress key points (knack, important, and special points). Instruct clearly and completely, taking up one point at a time--but no more than he can master. Check, question, and repeat. Step 3--Perform: Test him by having him perform the job. Have him Tell and Show you; have him explain key points. Ask questions beginning with Why, How, Who, What, When, or Where. Observe performance and correct errors. Repeat instructions if necessary. Step 4--Follow Up: Put him on his own. Check frequently to be sure he follows instructions. Encourage questions. Get him to look for key points as he progresses. Taper off extra coaching and close follow-up until he is qualified to work with normal supervision. If the worker hasn't learned, the instructor hasn't taught. Breaking Down a Job into Its Component Parts It is generally accepted that 80% of most jobs are very simple operations and can be done by the average person with a minimum of 212 Safety and Accident Prevention in Chemical Operations training. The remainder, or 20%, represents the skills or tricks of the trade resulting from training and experience. These important steps must be emphasized and made clear in the training procedure. A job break-down sheet is invaluable in analyzing a job as well as in instructional work. A simple job break-down sheet shown below for training new men can be made quickly for almost any job. The proper procedure of diluting acid will serve as an example. Job Breakdown Sheet for Training Man on New Job Part or Material Operation Sulfuric Acid Diluting Acid with Water Important Steps in Operation Key Points--Knacks--Hazards, Feel, Timing, Special Information Step 1 Add 100 gal of water to tank. Step 2 Start agitator. Step 3 Open the valve on the 1 in. 98% acid line and run it into the measur ing tank until 10 gal are in the tank. Step 4 Transfer acid from measuring tank to the water in the receiving tank. Step 5 Make specific gravity test. Step 6 Run mix into holding tank. Use dip stick to measure water depth before adding acid. Make certain agitator is operating. Wear safety protection such as acid goggles, rubber gloves, and apron. Use face shield when checking con tents of tank. Add acid to the water in the receiving tank slowly and keep the agitator operating. Always add the acid to water slowly. Never add water to acid because of reaction heat gener ated and danger of splashes. Use Baume scale. Make certain that there is room in holding tank and discharge valve is closed. On-The-Job Training On-the-job training is the best method of presenting a full, clear, and actual picture of the work to be performed. It is here that previous ETC 03241 Safety Education and Training 213 instruction is tested by demonstrating its application on the job itself. When the employee performs the work, using the training he has re ceived, he combines the abstract and the concrete phases and completes the picture of the why, how, who, what, when, or where. group training Small discussion groups are sometimes used to impart information. These give the participants a feeling of belonging. The discussion leader prepares the outline, presents it to the group, and directs the discussion toward the goal he has in mind. If a problem is to be considered he should present it at the beginning of the discussion and have pertinent questions prepared. He should not dominate the discussion but direct it. Meetings and Instructional Presentations There are many useful methods to be included in a training program so that the work is done the right way, which means the safe way also. Important among these methods are meetings and discussions. Prepa rations for leading the discussion or following the program must be made in advance. The meeting place should be adequate in space, with sufficient ven tilation, comfortable seats, good illumination, and a blackboard or charts. Start the meeting promptly and keep it moving toward the goal. Do not try to cover too many subjects in one session. Keep dis cussion going and have all participate. Keep the meetings short. Instructional Aids Sensory aids may be grouped under these classifications: Motion pictures Slides Photographs Posters Opaque projectors Textbooks Take-home material Models Charts and diagrams Flannel boards Audible examples with pictures Display boards Damaged equipment The job itself MOTION PICTURES Motion pictures are a major tool for instructional purposes. The sound track added to the film presents the explanation well and en- ETC 03242 - .-to 214 Safety and Accident Prevention in Chemical Operations courages discussion after the film. The teaching information reaches the mind of the trainee by means of the auditory route as well as the visual. SLIDES Slides are a convenient method for packaging a collection of material to assist in clarifying the course of instruction. Photographs and posters may be used in the same manner. CHARTS AND DIAGRAMS Charts and diagrams assist in maintaining interest as well as clari fying pictorially certain facets of the information presented. MODELS Models may be working miniatures made to scale. They may be designed to provide motion as when machines are under discussion. Plant layout in model form to illustrate movement of product and production requirements are used to stimulate discussion as well as to explain the problem and presentation. FLANNEL BOARD Flannel boards allow for advance preparation and save more time than the blackboard presentation. A better job of presenting the facts in a clear and concise fashion is achieved by flannel boards. DISPLAY BOARDS Display boards showing the right and wrong way, damaged material, waste prevention, and ways to improve production have a place in the instructor's book. AUDIBLE EXAMPLES Audible examples taken from actual experience show the advantages of certain ways compared to the disadvantages of others. TEXTBOOKS AND RULE BOOKS Textbooks and rule books dealing with the subjects are invaluable. The trainee should be given an opportunity to review the subject at ETC 03243 Safety Education and Training 215 home if possible and then have a reference for future application. These are handy reference books for instructors and supervisors when they wish to spell out a safe and proper procedure to be followed. 12.2. TRAINING AND EDUCATION IS NEVER COMPLETED After the initial training or break-in period is completed there is a definite need of follow-up--to keep alive the need of good practices. In promoting safety meetings as part of the program for production --and safety cannot be disassociated from production--we can sum marize the procedures and things to keep in mind. For example: 1. The purpose is to make the employee understand why he must work SAFELY. He benefits. 2. Exchange ideas and arrive at a logical conclusion. 3. Develop personal contact with men. 4. The foreman should deal with specific hazards in his department. 5. The foreman should lead the meeting. 6. He should be prepared, and his subject should be appropriate to the occasion. 7. If subjects are interesting, employees will want to talk and par ticipate. 8. Present a problem or experience, and let the employees carry on, but arrive at a conclusion. 9. Guide the discussion and avoid a gripe session. 10. Focus attention on a specific accident, problem, or new and better method. 11. Do not try to cover too much at one session. Establish at least monthly meetings on definite days. 12. The foreman or leader must be sincere. 13. Praise employees when a good job is done. 14. Provide safety equipment and explain its use and the need for using it. 15. It may be well to give advance notice of subjects. 16. A panel with question and answer session helps to change routine. 17. At a contest to decide the best stunt to promote safety, 70% of all replies indicated the best stunt is to have supervisors meet with the men to discuss the problem. 18. Be careful about leaning on undependable slogans and labeled thinking, such as "Safety First." 19. Safety is not first. We must have training, education, explanation, engineering, and enforcement. We must put our hearts, minds, and souls in our work and then we will have safety. 216 Safety and Accident Prevention in Chemical Operation* No attempt has been made in this chapter to deal with other useful motivating methods, such as contests, slogans, dramatics, suggestion systems, bulletin boards, and specialized training. 12.3. STANDARD OPERATING PROCEDURES Chemical Operation Process and Flow Sheets Provision of the right physical facilities is not all that is necessary for the safe operation of a plant. Just as important are the practices of persons operating it and the information and procedures which they must be given to follow. In general, the research organization develops the formula for the product and studies the prospects for customer use and demand. The effectiveness of the product and the means of producing it are then reviewed. During the research period notes are made of the mixtures, quantities, availability, reactions, and hazards. After it has been decided to consider making the product, the details for production are given to the pilot plant. Here small batches are made under the direction of the men who will decide on what equipment to use, the place of manufacture, the methods of controlling temperatures, pres sures, and gases, the general procedures to follow, and standard meth ods necessary to control quality, hazards, waste, and time. During this period process sheets and flow charts are prepared. They specify the best, safest methods and are written as definite instructions which must be followed in the manufacturing department. During the pilot plant period many problems are resolved, the yield is determined, costs are prepared, hazards are listed, and precautions are indicated. The engineer assigned to the job makes plans for the space and equipment required and accompanies the project to the manufacturing department, so that he can assist in the training program and assist the foreman and operators to achieve normal production. He also makes whatever changes and improvements are required, and he is the con tact man with production, pilot plant, engineering, development, and research. Process Sheets and Flow Charts Process sheets are available to operators. They include safety precautions required and, when hazardous chemicals are involved, symptoms of exposure and immediate first aid treatment to be given. Suitable fire extinguishment equipment is also specified where flamma ble material is used. ETC 03245 A sample safety sheet, which may accompany the process sheets when new chemicals are introduced in the manufacture, follows. This sheet tells the operator what to look for and what action to take if things go wrong. 12.4. PERCHLOROETHYLENE (PCE) (TETRACHLOROETHYLENE) SAFETY SHEET Properties Colorless, nonflammable liquid with an ether-like odor, and a density of 13.4 lb/gal at 25C. It is completely soluble in alcohol and ether and miscible with all common solvents and oils, but the solubility in water is only 0.01%. Boiling point = 121C at 760 mm Melting point = --23C Safety This solvent can be handled safely if proper precautions are observed con stantly. Prolonged, excessive, or repeated exposures to PCE in any form are hazardous. Perchloroethvlene is not corrosive or dangerously reactive, but it is toxic on inhalation, on prolonged or repeated contact with the skin or mucous mem brane, or when ingested by mouth. The liquid can cause eye injuries also. The maximum allowable concentration in air is 100 ppm for an 8 hr working day. Exposures to vapor concentrations greater than 200 ppm cause irrita tion, lachrymation, and burning of eyes, irritation of nose and throat, and may cause vomiting. Perchloroethylene is less volatile than water, but the vapors are almost 6 times heavier than air. Good ventilation in the working area is required, particularly at floor level. PCE should not be stored in pits, basements, or unventilated areas. Perchloroethylene is nonflammable and nonexplosive, and it will not sup port combustion. However, if the vapor is exposed to high temperatures (open flames or electric heaters) it may be decomposed to toxic substances. Spillage Spills should be mopped up and the rags used placed in closed containers or dried outdoors in a safe place. If clothing is wet with PCE it should be removed immediately and not used again until free of solvent odor. A shower should be taken, washing all affected areas thoroughly with warm water and soap. Prompt medical attention should follow. To protect the eyes, approved chemical goggles or face shield must be worn when handling PCE. If liquid PCE should contact the eyes, wash immedi ately with copious amounts of water for at least 15 min. Medical attention should be obtained after this. Suitable respiratory equipment approved by the U.S. Bureau of Mines should be available for use in an emergency. If an excessive amount of ETC 03246 218 Safety and Accident Prevention in Chemical Operation* vapors are inhaled there will be irritation of the eyes, nose, and throat, fullness in the head, and mental confusion. Prompt removal from the contami. nated area is necessary. If breathing has stopped, artificial respiration should be started immediately, and a physician called at once. Oxygen should be administered by oxygen inhalation apparatus when available. Numerous trade associations and other organizations provide safety service and information. The most useful of these in the scope of chemical safety are cited in Appendix I. Depending on the product to be made, the instruction or process sheets may include references, specifications, flow diagrams, equipment required, yield expected, hazards, precautions, reactions expected, method of sampling, heats and cooling required, disposal of residue and waste, use of by-products, health hazards, protective equipment required, running time, costs and action to take in emergencies such as power failure, water failure, fire control, and extreme reactions. It is important that standard operating procedures be kept up-todate and that the operators follow them very carefully. No changes are permitted without first obtaining proper authorization. Start-Up--Shut-Down Routine The start-up operations and the shut-down (normal) and (emer gency) are extremely important. In chemical manufacture we cannot just pull a switch and stop the work. We must consider the operation cycle at the time, the danger of explosion, set-up of material, how to clean out the equipment, what must be added in material, cooling or heating, and the dangers of various reactions. Plans should be made in advance for a normal or an emergency shut-down and these should be made as part of the regular operating sheets. Closing down operations in a continuous chemical plant might take hours and starting up preparations often take days. Considera tion is given to the possibility of releasing fumes and causing damage to areas outside of the plant. 13 Personal Behavior--Rules and Regulations M. A. Gimbel 13.1. RULE BOOKS--SAFETY MANUALS Whenever we read a book of rules and regulations we know that accidents have occurred which prompted the writing of the rules. The use of safety manuals is general in industry. Plants usually write their own and include information which is applicable to their opera tions. Workers, however, are not inclined to read material which ordinarily has no immediate appeal to them. A recent trend is to use cartoon style and comic book techniques for eye appeal. Some books are written for special crafts or operations while others are more general. Passing out rule books to new employees is not sufficient. The books must be interesting, have informational value, and serve as an educa tional device and reference book. Supervisors must be familiar with the contents and use the books in training, in discussion periods, and in safety meetings. The problem is to keep the contents of the book always fresh in the minds of the employee. The distribution of pocket-size safe-practice cards at regular inter vals, to be followed up and discussed at a meeting serves as a quick but impressive reminder. Some companies prefer to use books showing pictures of a hazard and having a few words of explanation indicating what not to do as well as what to do. Most of the large chemical companies have prepared their own 219 ETC 03248 220 Safety and Accident Prevention in Chemical Operations safety books, and some of these are equivalent to a textbook for safe operation. They are available in most instances on request. Subjects usually covered include: The policy of the company regarding accident prevention Reporting accidents Emergency first aid Information for laboratory workers Handling chemicals Unloading chemicals from drums, trucks, and cars Housekeeping Safety equipment available Waste disposal Use of tools Fork truck operation Eye protection Fire prevention Smoking regulations Welding rules Use of fire extinguishers and fire alarm .Sprinkler systems Flammable liquids Health hazards Inspection of equipment Shutting down processing equipment Safety organization Specific instructions General safety information 13.2. SPECIAL SAFETY INSTRUCTIONS FOR SUPERVISORS Usually safety instructions to employees are not sufficiently detailed to include special information which supervisors should have. To com pensate for this a supervisor's book is prepared in loose leaf form and information and instructions are added as needed. Subjects for this special book may include information on: Mandatory eye protection Standard goggles in use at the plant Precautions with flammable liquids Use of available fire extinguishers Grounding portable electric tools Personal Behavior--Rules and Regulations 221 Bonding and grounding vessels--static electricity Welding and burning permits Men working alone Use of hose clamps and hose connections Hazards of toxic solvents Standard paint colors for pipes (if used) Flame arrestors--maintenance Use of freight elevators List of maximum allowable concentrations and explosive limits of various chemicals Rules for men working in tanks, tank cars, kettles, or other confined spaces Rules for operation of fork trucks and other power equipment Respirators and gas masks--purpose of use and kinds available Safety contest rules Table of hazardous substances Pressure relief valves--uses, kinds, and maintenance Lock out of electrical switches before working on equipment Mandatory head protection with hard hats Disaster and plant emergency plan The Manufacturing Chemists' Association2 Safety Guides and Chem ical Safety Data Sheets are written primarily for issuance to super visory personnel to fit the above pattern. The National Safety Coun cil3 and other organizations also furnish suitable material. (See Ap pendix B.) 13.3. SAFETY STANDARDS It is necessary that safety standards be established to cover such subjects as guarding, machine controls, employee behavior, truck opera tions, lighting, ventilation, housekeeping, fire prevention, rules of op eration, preparation of process instructions, and many others. It is management's responsibility to state clearly the safety standards so that there can be no misunderstanding or cause for confusion. The safety standards must fit into the general operating pattern of the plant, must be short and to the point, and must make sense to the supervisors and employees. Safety is a part of business and must be given the same attention as other problems in plant operation. There can be no procrastination in the plans and no neutral zone. 222 Safety and Accident Prevention in Chemical Operations To integrate safety into the operation,-management should: 1. Establish definite written plant safety standards. 2. Clearly outline each employee's and supervisor's responsibility. Hold supervisor responsible for the safety of those working for him. 3. Plan safety into each job and process and provide suitable facilities. 4. Supervise according to safe methods with no deviation. 5. Make frequent inspections in all departments of conditions and prac tices. 6. Have a sincerity of purpose and insist on safe performance through the supervisors to the men on the job. Men expect positive leader ship in safety problems. Guelich1 describes a number of chemical accident situations and dis cusses the problems of supervision. Smoking Privileges Smoking privileges are a serious problem in the plant. In recent years the rules have been modified in order to avoid loss of time and to accommodate the employees. In chemical plants it is essential that we establish the rules, allow time for smoking, but be firm about enforcement. It is best to write down or post notices in places where smoking is permitted, and inform employees that it is prohibited in all other locations. This obviates the need of many NO SMOKING signs throughout the plant. Visitors and contractors must be prop erly informed of the smoking rules and required to conform. PERMITTED AREAS Usually in chemical plants smoking is permitted only in the office areas, locker or change rooms, eating rooms, and special areas estab lished for the purpose. This fact should be posted in conspicuous locations. PROHIBITED AREAS No smoking is permitted on the roads or outside of buildings. A notice to this effect is usually posted at the entrance. Under no cir cumstances would smoking be permitted in areas involving polishing, dusts, flammables, material storage, waste material, gases, paints, sol vents, manholes, tunnels, gasoline, or any fire hazard areas. In some plants carrying on unusual operations it is advisable to ETC 03251 Personal Behavior--Rules and Regulations 223 extend the No Smoking rule to include the surrender of matches and automatic lighters from the person at the entering area. Powder, chemical, and petroleum plants would fall within this category. More willing cooperation will be obtained if the reason for the rules is explained. Where smoking is permitted suitable disposal units for butts should be provided. In areas where matches and lighters are not allowed, stationary electric lighters may be installed for the men. Men Working Alone In many instances we have an operation where one man only can be efficiently employed particularly after the regular work hours and at weekends. The work he is expected to do must be carefully studied and hazardous operations eliminated or minimized. Usually arrange ments are made with the lone worker to telephone the guard office every hour at a specified time to report everything satisfactory. In addition to this the guard or watchman is instructed to check the man on his regular tour. If the man working alone fails to report on schedule, the guard will attempt to reach him or, if necessary, go to the place where the man is working to investigate. Whenever possible it is desirable to use the buddy system where men look after each other. This system has paid off in many instances. Prompt Reporting of Occupational Injuries or Illnesses It is necessary that all industrial injuries be reported at once. In this way prompt treatment affords a quicker recovery and reduces danger of infection. A record of the case is made, steps are taken if a correction is necessary to avoid future injuries, and department heads are informed of what is happening in their departments. Reports for workmen's compensation can be initiated at once when disabling in juries occur. Plant Dispensaries and Physicians The plant physician is in an excellent position to diagnose and treat cases that are peculiar to the chemical industry, more especially so in occupational diseases due to exposure to chemicals. Large chemical companies usually develop methods of treatment for possible exposure to new and other hazardous chemicals. They also 224 Safety and Accident Prevention in Chemical Operationt keep a supply of medicines and equipment needed for special treat ment. Their medical departments are closer to the work and better prepared for prompt attention. Therefore, it is advantageous to the employee to go to the plant dispensary promptly for minor ailments and injuries. He may be directed to a specialist if the case warrants it. (See Chapters 12 and 13.) Should We Penalise the Worker for Infractions? Many persons who have had repeated accidents are below average in learning ability, intelligence, and hard work. There is some indica tion of a relation between accidents and low scores on intelligence tests. On the other hand, we find also many accidents occur in work involv ing men of higher learning and experience. Normally these injuries are explained by statements: I just didn't think--I know better--I was pressed for time--I took a short cut. Should we penalize the victim of an injury for his failure, or has he suffered enough? The reaction of other employees as well as the injured might be adverse in some instances if the case is improperly handled. The time for a penalty is not after the accident but when in fractions of safe practices occur, particularly when willful. Sound judgment must be used in the administration and treatment, and decisions must be consistent. Usually this subject is discussed by management with supervisors and union representatives, if any, who in turn carry the message down the line. The rules and penalty provisions should be in writing, well publicized, and apply to everyone without exception. WARNING NOTICES For the first violation the employee may receive a written warning, for the second violation a written warning which indicates the penalty for a third offense, and both should be signed by the person being warned and filed with his record. The third offense carries with it suspension, discharge, or other drastic action such as transfer or demotion. This is the accepted practice for all infractions of good work prac tice, and safety is merely a part of normal performance such as suit able production, punctuality on job, safety, and good conduct while ETC 03253 Personal Behavior--Rules and Regulations 225 at. work. The fact that an employee signs a notice of this kind im presses him with the sincerity of management, and he has no excuse that he was not informed about his actions. Those cases where warnings apply include: 1. Failure to wear eye protection, masks, protective clothing, or hard hats when required. 2. Unauthorized removal of guards from equipment. 3. Hitching a ride on materials handling equipment. 4. Unauthorized use of machines or other equipment. 5. Failure to report promptly for first-aid treatment after any injury. 6. General failure to follow rules listed in the safety manual. The exceptions to the above warning routine where immediate dis missal is warranted are for stealing, fighting, intoxication, smoking in certain areas, and other serious offenses. Correction of Unsafe Acts The causes of all accidents can be divided into two categories: unsafe physical condition and unsafe personal acts. Investigation of accidents invariably reveals several underlying conditions which finally resulted in the accident. We must keep in mind that a large proportion of accidents do not result in personal injury or damage of some kind. How often has a load been dropped from a crane hoist without damage or injury merely because nobody was near the load at the time or the material did not break. How many explosions occur when nobody happens to be in the vicinity? Heinrich4 stated that only 15% of accidents are due solely to un safe conditions and thus unsafe acts figure in 85% of all cases. Human error lies behind many unsafe conditions such as inadequate guarding, improper design and construction, poor maintenance, or poor illumination or ventilation. UNSAFE ACTS OF PERSONS Some injuries or accidents occur because of the behavior of the individual. Included under this heading are: The personal factor, the mental or bodily characteristic which per mitted or occasioned the unsafe act 226 Safety and Accident Prevention in Chemical Operations Correction of unsafe acts or behavior and of the underlying causes lies squarely in the hands of first-line supervision. The supervisor may choose counseling, retraining, discipline, or a combination of these methods but he cannot allow unsafe acts to continue. The em ployee who persists in such behavior patterns is statistically certain to injure himself or someone else. Deal Through Lines of Organization In dealing with departmental problems it is necessary to work through the supervisor, because he is the one who is responsible for production and for his employees and equipment. It is always best to go through regular organizational channels in order to get willing cooperation. The extent to which management and supervision believe in the need of safe operations and the sincerity and consideration given the problems has a direct bearing on the success of the plan and determines the attitude of the entire organization. Never has there been a safety device or a safety program that some human being could not disrupt or impair. The total working atmos phere must be considered for man controls his environment. Every thing which makes it warm, friendly, pleasant, and secure contributes to safety and the cooperation to prevent accidents. ETC 03256 ETC 03257 impact of Occupational Medicine on Safety 229 fears of "empire building" and their inability to exercise proper con trols in a field completely foreign to them may overshadow their realization of the potential of a good program (see Table 14.1). The full or part time industrial physician may fail to realize that preven tion of industrial injuries is as much a part of preventive medicine as prevention of industrial diseases through proper environmental controls. In this chapter will be discussed ways that the industrial physician and other members of his department can contribute to the field of safety. 14.1. RELATIONSHIP BETWEEN THE SAFETY ENGINEER AND THE INDUSTRIAL PHYSICIAN Far too often there exists a lack of understanding and communica tion between the safety engineer and the industrial physician. Each feels that the other does not have a true understanding of his problems. The occupational physician may feel that the safety engineer is far more interested in numbers as a record rather than the actual injury to the individual. On the other hand, the safety engineer may feel that the treating physician does not appreciate that the maintenance of a good safety record is one of the most dynamic forces in motivat ing employees to work safely and to prevent accidents and injuries. A resolution of these differences is essential before a plant can have a truly progressive safety program. It should be apparent to the industrial physician that the safety engineer is a front-line ambassador of good will for his services in the plant. On the other hand the safety engineer should realize that medicine is an inexact science where experience, training, and attitude give rise to honest differences of opinion as to the choice of treatment and the injured employee's ability to work. To exploit these honest differences is one of the surest ways of destroying good working rela tionships between the medical and safety departments. Setting aside a portion of time each month for better communications would do wonders at improving this relationship and developing understanding of common problems. 14.2. TREATMENT OF OCCUPATIONAL ILLNESSES AND INJURIES Treatment facilities and the people who staff them have an im portant bearing upon the safety record of any particular plant. It is usually within the walls of these facilities where the most accurate 230 Safety and Accident Prevention in Chemical Operations history and accountability for an accident are really obtained. It has been the experience of every occupational physician of obtaining an accurate history while treating the patient then later seeing this history distorted by various participants in the safety appraisal of trying to determine the responsibility of the accident. Again the communication between the occupational physician and the safetyengineer is vitally important if the true causes and preventive aspects of industrial injuries are to be uncovered. Convenient medical facilities and an enlightened attitude by man agement is necessary to keep minor injuries from becoming com plicated and turning into major disabilities. Many times a small bum has become infected and resulted in a lost-time accident due to the employee's delay in seeking medical treatment because of fear of con demnation from his fellow employees or his supervisor. For this reason, using minor injuries as an index of safety performance within a department is an unwise procedure. It may lead to a reluctance on the part of the -worker to report his injury. Departmental indexes of safety performance should be based on the severity of the injury and the potential serious injury rather than numbers of minor injuries reported to the industrial medical clinic. Physicians have long been disturbed by the emphasis that is given to the lost-time injury of a man who loses a small fragment of bone from the tip of his finger in a relatively minor incident, and the lack of attention to an incident such as an explosion blowing a propelled piece of metal past an individual and only scratching him. In this instance a few millimeters position in space by chance was the difference be tween life and death, but because it was not recorded as a "lost timer" it was soon forgotten and seldom reviewed. Medical personnel can be a valuable adjunct to the total safety effort by being alert and understanding the need for safety protection and safety vigilance. This must be done skillfully in a nonpreaching, noncondemning manner that will teach a lesson rather than alienate the feelings of the worker. For example, it is ridiculous for an in dustrial nurse to tell a man with a broken toe that he should have been wearing safety shoes. Nobody is more painfully aware of this fact than the man with the broken toe. Comments of this nature only serve to make the individual defensive and consequently unreceptive to good safety counseling. If that same nurse would devote this same energy at recognizing the lack of foot protection at a time when the man's foot was not injured, far more would be accomplished. Medical personnel represents a powerful voice of authority when it comes to advice regarding safety. The employee recognizes that medical staff Impact of Occupational Medicine on Safety 231 members have had first-hand experience with injuries resulting from lack of safety protection. Chemical Exposure One of the "gray areas" which many times creates problems is in accurately determining whether loss of time from the job is due to a chemical exposure- or to a superimposed personal illness. A good example is when a man has been working around benzene, does not give a history of any unusual exposure, but becomes nauseated and has to be off the job for a few days. Another example is an in dividual who inhales a minimal amount of an irritating gas such as chlorine or sulfur dioxide and develops an upper respiratory infec tion which necessitates loss of time. In both instances the occupa tional physician is hard pressed to make an accurate decision because of the lack of real objective evidence upon which he can base his judgment. Invariably, too much time elapses before the environment can be monitored to determine the concentration of the material to which he was exposed. Within the past few years a' number of useful tests have been de veloped which take many of these situations out of the area of specula tion and give the physician real objective laboratory evidence to help in this situation. Figure 14.1 is such an example and is called the forced expirogram.* This is a timed vital-capacity measurement and shows the sequence of events from a chlorine exposure and demon strates objective evidence of the physiological response of the human body to this particular irritating gas. Chlorine produces a temporary spasm for constriction of the air passages in the lungs and consequently restricts the rate at which the individual can exhale the air from his lungs. It can be seen in Fig. 14.1 that there is not only a reduction in total amount of air expired but also a slowing down of the rate that it can be expired. This and other objective tests such as the use of serum trans aminases after exposure to many organic chemicals provides the phy sician with valuable evidence to judge the true nature of a person's disability. Pre-Employment Examinations Uncovering physical defects that may play a role in the future safety performance of a prospective employee is one of the main ob- * Collins Yitalometer expirogram record, Warren E. Collins, Inc., 555 Huntington Ave., Boston, Mass. ETC 03260 232 Safety and Accident Prevention in Chemical Operations FIG. 14.1. Expirogram record. jectives of the preemployment physical examination. However, only a small percentage of applicants who are examined in a good pre employment. examination are found to be perfect specimens. Most people have one or more minor defects. They are overweight, have visual defects, some difficulty of hearing, allergy, or an unstable blood Impact of Occupational Medicine on Safely 233 pressure. At the time of the examination these may not be judged serious, but because they are potential problems the new employee's supervisor should be informed. Frequently there is a lack of communication between the medical department and the new employee's supervisor regarding these minor defects so numerous companies have found it advantageous to devise a profile system to let the supervisor know what some of these signifi cant defects are. For example, a prospective employee might be almost blind without his glasses and pass the pre-employment testing with flying colors because his vision was examined while he was wearing his glasses. He might then report to the job without his glasses and be a serious safety hazard unless this communication between the medical department and supervision was operating. Within the Dow Chemical Company a profile system is used which was developed by Dr. Harold Gordon* and patterned after the armed forces PUHLES system. This system is called the PESREP profile system which is an abbreviation for the following categories: physique, extremities, skin, respiratory, eyes, and psyche. The physician grades each cate gory from one to five depending upon the severity of the physical defeet and a copy of this profile is then sent to the personnel office and to the prospective employees' supervisor. This establishes the communication link that is so important and yet does not break down any of the confidential medical information that should be maintained as only those defects that directly affect work performance are included. There is a great trend in industry to slice up the prospective employee into various jigsaw pieces and test each piece independently. The various pieces may be a security check, check of his social status, personnel interview, physical examination, temperament testing, I. Q. testing, mechanical aptitude testing, lie detector test, plus many future tests which will beguile the imagination and probably divide the person into smaller jigsaw pieces. Each of these things are important but it is distressing to see how infrequently the man is evaluated as a whole unit instead of in various pieces. Dr. W. Donald Ross, an as sociate professor of psychiatry at the University of Cincinnati, brings out in his book Practical Psychiatry For Industrial Physicians3 that lumbar X-ray results when evaluated with psychological testing are far more meaningful than when evaluated alone. Industry should spend more time putting the pieces back together and interrelating the results. * Harold Gordon, M.D., Medical Director, Midland Division, Dow Chemical Co., Midland, Mich. 1 ' < j : j 1 i ! j ; j j j ; 1 ! j : . ETC 03262 234 Safety and Accident Prevention in Chemical Operations Periodic Physical Examination Program There is scarcely a segment of the chemical industry where the em ployees do not come in contact with toxic or injury-producing terials that are often insidious in their disease-producing ability. the time these occupational diseases give rise to definite symptona that are noticeable to the workman, it may too late to do an effective job of reversing the disease process. For this reason periodic physj. cal examinations are a necessity in some areas. The safety engineer can be of invaluable assistance to the occupa. tional physician by making him aware of the job demands and chem ical exposures encountered in various areas. Many times the results of these periodic examinations must be evaluated statistically to de termine the exact reason for the employee's disability. For example if a physician had examined a group of twenty paint sprayers and found evidence of chronic lung disease in one, he will be hard pressed to draw a conclusion definitely establishing the respiratory exposure to the disability since this condition might be due to something totally unrelated to plant exposure. On the other hand, if he found ten people with respiratory abnormalities, there could be no denial that the job in question would be incriminated unless proven otherwise. This is one of the soul-searching problems in interpreting the re sults of periodic physical examinations as this enters the field of statistical significance, opinion, and frequently, disagreement. EDUCATIONAL One real problem that faces any safety program is the lack of in teresting material relative to safety that is available for presentations. This is an area where the occupational physician can be of great benefit since nobody has seen more of the sadness and heartbreak from poor safety practices then the physician himself. Because of these facts he is regarded as an authority and his words fall upon receptive ears. It would be ideal if the physician could devote a great deal of his time giving talks in the plant, but unfortunately other demands of his medical practice have priority over personal ap pearances. Some physicians have solved this problem by presenting material by slides and tape recordings4 and Fig. 14.2 illustrates a sample slide along with the written commentary that may be used in such instances. Another area where the medical department can make a valuable Impact of Occupational Medicine on Safety 235 FIG. 14.2. Photograph of an eye (35 mm color transparency). A representative case of a chemical burn to the eye over 20 years ago with no impairment of vision blit with permanent loss of mam- of the eyelashes on the lower lid. contribution lies in the field of advanced first aid training since the chemical industry has unique problems relative to first aid that are not covered in the standard first aid courses. Ideally a physician should train a selected group as teachers to instruct all of the plant personnel. Again the liberal use of slides and tape recordings made by the physi cian can be of great benefit. REHABILITATION One of the most positive and humane benefits that occupational medicine can contribute to the total safety effort lies in the field of rehabilitation and proper placement of disabled employees. Whether their disability is from an occupational or a personal illness, the end result in most instances is the same--a lack of productivity to the company involved and economic loss to the worker. In rehabili tating an employee back to a job, the cardinal principle to remember is that "you benefit neither the employee nor the company unless you can place him on a job where he is productive and earning his pay." Creating a job just as an excuse to pay a man invariably leads to a disgruntled employee because of the subtle but powerful and emo tional condemnation by those employees around him. We must remember that all workmen have certain basic- emotional needs on the job. They need to feel accepted by co-workers and must maintain an inner feeling of security by earning their salt rather than being a char ity case. Unless a man feels productive an improper job transfer is only a temporary solution at best. ETC 03264 236 Safety and Accident Prevention in Chemical Operations The safety engineer as well as the industrial physician should worM with the personnel department in effecting proper job transfers. Thd fundamental role of the industrial physician in this sphere is evaluate the mental and physical abilities and outline those work restrictions which are necessary in order to avoid future disability] Because of the time pressures of his medical practice he usually does j not have an intimate knowledge of each job requirement. On the* other hand the safety engineer is in an enviable position of knowing! more about job requirements and potential job transfers than anyi other single person in the plant because of his field work and working \ relationships with supervisors. Unfortunately, most safety engineers! do not consider this within the scope of their activities. A workable program of rehabilitation and proper job assignment is often impossible because of existing labor contracts, seniority rights economic losses to the individual by changing to a job of lesser skill or lower classification, and to plain old lack of human motivation and doing nothing until an accident happens. The latter reason is an old story to the safety man and should point out the necessity for con tinuing pressure to break down these obstacles. The field of rehabilitation and proper job placement is frequently frustrating and unrewarding but like so many other problems with human beings, the difficult ones are the truly important ones. In Table 14.2 we see a suggested systematized approach to rehabilitation and proper job placement. TABLE 14.2. Rehabilitation Steps Involved Personnel Involved 1. Recognition of problem VUrfcer, supervision, medical, safety, and labor relations 2. Attempt to transfer with existing Worker, personnel, safety, and labor physical defects relations 3. More intensive appraisal of worker to determine his best points as well as disability Worker, medical, and clinical psychol ogist 4. Referral to special group for place ment Worker, handicap committee super vision, medical, safety, labor rela tions, and psychologist 5. Retraining Worker, occupational therapist, and safetv ETC 03265 Impact of Occupational Medicine on Safety 237 Psychological Counseling Mental illness is the number one problem of our society at this time. Statistically, one out of every ten individuals in the United States will be hospitalized sometime during their lifetime for treatment of mental illness. This leaves little doubt as to the impact of this prob lem on the field of safety. In this field there are a great many un known and erroneous concepts concerning the emotionally ill and their relationship to the safety program. The chronic alcoholic who is generally thought to be a serious threat to the safety record is, in most instances, a careful worker because of his fear that an accident will lead to the discovery of his alcoholism and subsequent discipli nary action. Absenteeism is the real problem associated with alco holism. Another general concept concerns the acutely disturbed individual who has outward manifestations of emotional turmoil. His fellow employees are fearful that he might "blow up the plant," but sur prisingly enough he is rarely associated with a serious occupational injury during this disturbed period of time. Perhaps the most overlooked but most significant hazard is the man whose outward appearance is one of serenity, but who is harboring profound psychological problems which may manifest themselves in an occupational injury (Fig. 14.3). In a situation such as this it is frequently found that the injury and the subsequent disability play a very definite role in solving that particular man's problems. Many people fail to appreciate the role that the work situation plays in individuals with emotional breakdowns. Dr. H. Levinson, director of the Industrial Medical Health section of the Menninger Foundation, stresses that the majority of the industrial accidents occur in people who have these underlying emotional problems.5 Mental illness, which is not clearly black or white, is difficult to accept in many instances. Much more research is needed in this particular field as it applies to safety, but recognition that these factors do play a role in accidents and dissemination of this knowl edge by the safety engineer may contribute to improvement in the safety record. ACCIDENT PRONE The phrase "accident prone" is a sad and tired quotation conceived many years ago by individuals who felt they could establish certain 238 Safety and Accident Prevention in Chemical Operations FIG. 14.3. Emotional anxieties. criterion from past behavior and accurately predict accidents in the future. Unfortunately, a careful statistical approach by those who actually deal and treat accident cases fails to bear out these predic tions. Psychiatrists and psychoanalysts who represent the highest degree of training in understanding the human mind almost always refuse to "go out on a limb" and predict definite future behavior in their patients. Realizing this, it becomes somewhat absurd to com pile a few figures on numbers of minor injuries of an individual, stir it in the pot with some brief psychological testing, season it with some crystal ball gazing, and come up with a resultant diagnosis and stigma of "accident prone" on a workman. An unpublished experience of the author involved an examination of the "accident prone" concept in a chemical plant with more than 8000 employees. The ten "thickest" medical charts (or those in dividuals who had reported the most injuries) were pulled and ex amined on the preconceived notion that these certainly must be the accident prone individuals because of the frequency of their medical visits. Their cases were reviewed by a physician, a clinical psy chologist, and the individual's supervisor. A determination was made Impact of Occupational Medicine on Safety 239 of the emotional stability of each case and the supervisor was asked his opinion as to the risk of serious injury in each case. The results were just the opposite of what would be expected. All of these individuals with frequent medical department visits were good, solid citizens with stable personalities. They were good workers. They were very consciously following the plant safety rules of reporting every injury to the letter. How unfortunate it w'ould be to label these individuals "accident prone" as a rewrard for strictly adhering to company rules. It has been the author's experience that most in dividuals who have disabling injuries are relative strangers to the medical department. This experience certainly does not fit with the concept that most people in management have regarding the accident prone individual.6 REFERENCES 1. Donald Hunter, M.D., The Diseases oj Occupation, Little, Brown, Boston, 1962. 2. R. T. Johnston, M.D., and S. E. Miller, M.D., Occupational Diseases and Indus trial Medicine, Saunders, Philadelphia and London, 1960. 3. W. Donald Ross, M.D., Practical Psychiatry jor Industrial Physicians, Thomas, Springfield, 111., 1956. 4. "Chemical Burns to the Eyes," "Chemical Burns to the Skin," "Prevention of Low Back Pain," 35 mm slide-tape presentations narrated by D. J. Kilian, M.D., of the Dow Chemical Co. Reproductions available from Medical Graphic Arts, Box 34, Lake Jackson, Tex. 5. H. Levinson, M.D.. "Illogical Logic of Accident Prevention," Menninger Foun dation. Transactions of the National Safety Council; Vol. 21, Printing and Publishing Industry, pp. 9-13 (1956). 6. R. C. Behan and A. H. Hirschfeld, The Accident Process, JAMA, Vol. 186, No. 4 (October 26, 1963),.pp. 300-306. ADDITIONAL REFERENCES C. Caplan, Principles oj Preventive Psychiatry, Basic Books, New York, 1964. R. B. O'Connor, "The Challenge of Industrial Medicine," Journal oj Occupa tional Medicine, Vol. 6, No. 5 (May, 1964), pp. 209-213. Man, Medicine, and Work--Historic Events in Occupational Medicine, Public Health Service Publication, Division of Occupational Health, U. S. Public Health Service, Department of Health, Education, and Welfare, Washington, D.C. The Hidden Hazards, 16 mm sound motion picture, produced by the U.S. Public Health Service, available from Audiovisual Department, Communicable Dis ease Center, U. S. Public Health Service, Atlanta, Ga. AMA Council on Occupational Health, "Scope, Objectives and Functions of an Occupational Medical Program," JAMA, 74, 533, 1960. W. T. Donan, Jr., "The Medicine Audit: A Tool in Appraising Occupational Health Programs," Journal oj Occupational Medicine, Vol. 6, No. 5 (May, 1964), pp. 221-226. ETC 03268 15 The Role of The Nurse in Chemical Plant Safety :*! Eleanor Mort, R.N. Occupational health has been defined as "the application of public health principles, and medical, nursing, and engineering practice for the purpose of conserving, promoting and restoring the health and effectiveness of workers through their place of employment."1 Safety programs are directed primarily toward the first of these aims--the conservation of health, while the health service personnel are chiefly concerned with promoting and restoring health. However, the health and safety personnel alone can only implement the kind of program management wants. They must have the cooperation of production supervisors and foremen, and through them the active participation of all employees in order to maintain a truly effective occupational health program. The number and variety of personnel making up the occupational health team varies with the size of the industry. Some organizations have a large full-time staff of doctors, nurses, and safety and indus trial hygiene specialists. In many places, however, there may be two or more full-time nurses and a number of full-time safety personnel; but the medical direction is provided by a doctor who has a private practice and spends only an hour or two a day at the plant. Relatively few of the nurses working in industry today have had any formal train ing in occupational health. This is also true of a great many part-time physicians. They both very often learn this different phase of their 240 ETC 03269 The Role of The Nurse in Chemical Plant Safety 241 FIG. 15.1. The anatomy of chemical equipment should be as familiar to the plant nurse as the anatomy of her patients. Courtesy Rohm & Haas Co. profession while working together to solve the problems and cope with the situations which arise. This is not the usual doctor-nurse relation ship. Caring for ill people in a hospital, the doctor gives orders and the nurse carries them out. In the industrial environment, however, since the nurse has much more opportunity to become acquainted with the plant, the people in it, and the work hazards involved, the parttime physician must depend on her to a considerable degree for both information and communication. Since they are essentially dealing with healthy people, they establish a "collaborative relationship"2 wherein they continuously work together to further the objectives of a good occupational program. The industrial nurse who works without direct medical supervision a great deal of the time must be ever alert to the danger of assuming functions which either legally or by professional training belong to the physician. It is essential that she have specific procedures and orders written by the plant physician covering all the more common occupa tional and nonoccupational conditions with which she may be con- 242 Safety and Accident Prevention in Chemical Operations fronted. The nurse in a chemical plant has a special responsibility ^ insure that the procedure book contains an accurate and up-to-date description of all chemicals made or used in the plant including inter mediate substances formed at various stages, and also possible by. products, with the circumstances under which they may occur--such as the possible formation and evolution of hydrogen sulfide from hy drolysis or acidification of sulfides or sulfhydrates; or phosgene from trichloroethylene on contact with heat or flame. The building or loca tion in which each substance may be encountered should be noted. The signs and symptoms of both acute and chronic toxicity should be listed, along with modes of entry into the body. Engineering methods of control such as special ventilation or enclosure of process should be included, as well as safety precautions to be observed, as for instance all rubber clothing when working with hydrofluoric acid.3 \\ FIG. 15.2. Industrial nurse participates in fire fighting practice session at the plant fire grounds. Courtesy Rohm & Haas Co. ETC 03271 The Role of The Nurse in Chemical Plant Safety 243 In addition to engineering and safety controls, medical restrictions should be enumerated. Asthmatics and people with other respiratory diseases should not work where they might be exposed to chlorine or other respiratory irritants. A small amount of chlorine in the air which might make the average person cough for a few minutes could irritate an asthmatic so severely that he would require medical treat ment. Specific instructions by the plant physician for the first-aid treatment of the corrosive, irritating, or toxic effects of each chemical substance should also be included. Nowhere is the knowledge and application of prompt first aid more important than in a chemical plant. In the event of a chemical eye burn or body burn, whatever can possibly be done to lessen the severity of the burn must be done immediately. Nothing that anyone can do later can reverse the tissue damage which has already occurred if swift, thorough flushing with copious amounts of water has not been carried out. The beneficial effects of cold water on chemical burns, following the initial flushing, have been equally as dramatic as the spectacular results achieved with the cold water treatment of thermal burns--the effectiveness of which is in direct ratio to the speed with which the hypothermia is accom plished and the length of time it is adequately maintained. Compiling a complete and accurate chart such as Table 15.1 requires the cooperative efforts of not only the medical and safety sections, but research and production personnel as well. Valuable information concerning the practical everyday problems of handling a specific substance can be learned by talking with the man who does just that for 8 hr a day. The completed data form a ready source of reference, and they are particularly valuable in the indoctrination of new people in both the medical and safety departments. For a doctor or nurse relieving for vacations or illness it is indispensable both for refreshing their knowledge and for bringing them up-to-date on any new chem icals or procedures. Every contingency cannot be covered by a standing order. Most work forces consist of a cross section of the population and anything can happen to them that can happen to people anywhere. A nurse never makes a medical diagnosis, but since the occupational health nurse usually sees the ill or injured person before he is seen by a doctor, she must be capable of making a competent nursing diagnosis. If every person who came to the plant hospital were sent to a doctor, a great many manhours of work would be wasted--and there would be no need for a nurse. In order to make a skillful nursing diagnosis the nurse must con stantly use her eyes, her ears, and all her trained powers of observation. ETC 03272 ETC 03273 The Role of The Nurse in Chemical Plant Safety 245 Even what may seem to be a simple request for an aspirin or something for an upset stomach can never be granted casually. Enough informa tion must always be obtained to accurately evaluate the seriousness of the complaint. The response to just a few questions may indicate that the present distress was probably caused by overindulgence and lack of sleep. On the other hand, suggestions of a more deeply rooted disturbance may gradually emerge. A comprehensive history, plus a detailed report of all symptoms, and a record of all vital signs observed bv the nurse can be of considerable value, both to the doctor in diag nosing the condition and also to the safety personnel in the case of a work-connected disability. In the modern-day chemical plant new materials are constantly being introduced. The full toxic effects on the human body of many of these substances are sometimes not known. Keen observation by the occupational health nurse combined with ac curate recording could be of considerable significance in epidemiological studies. In order to sustain an effective safety program directed toward the conservation of the health of the workers it is important that they first be physically capable of doing the required work. This neces sitates a comprehensive health evaluation plan which should include preplacement, return to work, and periodic examinations for those exposed to toxic materials. There are also a number of other occasions when a health evaluation is desirable such as when transferring from one job to another or at retirement. The physician is responsible for the health evaluation program. Realistic, well-defined policies must be worked out with management concerning such things as the kind of examinations to be made and where, when, and how often; when the nurse may return a worker to his job after being absent due to illness or injury; and when he should be seen by the plant physician. Once agreed upon, all policies should be written down. Written policies concerning the health-evaluation program can also be of great value in enlisting union cooperation in protecting the health of members. The nurse plays an important part in the health evaluation program. She frequently takes the preliminary health history and performs cer tain screening tests such as vision and hearing. She usually schedules the periodic examinations, and talks with the employee returning to work. Each of these health interviews affords her an excellent oppor tunity to add any pertinent information to his health record, establish rapport with the employee, convey to him her sincere interest in his health and welfare, and to either initiate or continue a health-education program with special emphasis on how to work safely 'with chemicals. If there can be said to be any one outstanding principle governing the ETC 03274 FIG. 15.3. Industrial nurse checks blood pressure of employee. Blood pressure measurements have been used in studies of chemical exposure, as well as more routine index of health. Courtesy Genera! Electric Co. Research Laboratory. safe handling of chemicals it is cleanliness. This includes everything from good personal hygiene to careful work habits and good house keeping. The importance of a thorough shower everyday and fre quent changes of work clothes, including underclothing, cannot be stressed too often or too strongly. Some chemicals, if not removed from the skin or clothes by thorough cleansing, can be very irritating to the skin; while others may be absorbed into the body. Nothing affords greater protection from both chemicals and harmful organisms than a clean, healthy, unbroken skin surface. Everyone working with chemicals must be impressed with the urgent need for proper skin cleansing and covering of any break in its con tinuity. According to a pamphlet published by the United States De partment of Health, Education, and Welfare, and the United States Department of Labor, "Dermatitis is the most common occupational disease that attacks the working man. But if every workman could be brought to realize how important a healthy skin is to his well-being, there would be far fewer cases of skin disease. ... In such heavily ETC 03275 The Role of The Nurse in Chemical Plant Safety 247 industrialized states as New York, Ohio, and Illinois two-thirds of all compensated occupational diseases are skin diseases."4 Chemicals can be handled safely if they are handled properly. Lack of clean liness and careless work habits are dangerous and should not be tol erated in a chemical plant. The more knowledge the nurse in the chemical plant has concerning the various substances used and made, the processes involved, the work environment, and the engineering, safety, and medical controls necessary for the safe handling of each, the more effective she can be both in promoting the health of the workers, and also in aiding the safety department in their efforts to conserve health. Familiarity with the effects of a certain chemical and the prompt instigation of pre scribed first aid can appreciably lessen the severity of an injury. A thorough acquaintance vfith toxic symptoms will help in the recognition o: LEFT vmaskJ FIG. 15.4. Industrial nurse and safety engineer check the oxygen administra tion equipment installed in plant ambulance, which provides oxygen for two patients. Such equipment must be thoroughly understood by the nurse as well as by other emergency control personnel. Courtesy General Electric Co. Research Laboratorv. ETC 03276 248 Safety and Accident Prevention in Chemical Operations of any early signs of trouble. In many instances this is the first indica. i tion the safety department has that there has been a break in the established safe-working procedure for a certain process, and the dif ficulty can be corrected before a more serious situation develops. In her day-to-day contacts with the worker, as she talks with him about his job, the occupational health nurse can better ascertain how well an employee understands and is conscientiously applying safe-working procedures if she is well informed concerning the hazards and problems involved, and the various engineering and safety measures used to control them.5'67 Formal first-aid classes are sometimes difficult to schedule in 3 busy plant, but a large number of the workers in all departments throughout the plant trained in proper first aid can be extremely valu- K \' FIG. 15.5. Industrial nurse gives on-the-job instructions in the use of rescue kit designed to aid in rescue of man from a reaction kettle. Courtesy Rohm. & Haas Co. ETC 03277 The Role of The Nurse in Chemical Plant Safety 249 able. It is well known that first aid training makes people infinitely more safety minded. Furthermore, when accidents happen, partic ularly involving chemicals, swift appropriate measures carried out by the people in the immediate area can appreciably lessen the severity of the injury--and even save lives.8 The tremendously rapid development and use of new chemical com pounds in our modern environment presents a continuously greater challenge to the occupational health teams in today's chemical plants. As a member of the team, the nurse plays a vital role in helping to develop and maintain a program which is realistic in its recognition of the many production problems in this highly competitive industry; and yet is effectual in providing the means for "conserving, promoting, and restoring the health and effectiveness of workers."1 The opportu nity to participate in the exciting development and production of fas cinating new materials and products makes nursing in a chemical plant one of the most stimulating in the whole field of occupational health. REFERENCES 1. M. L. Brown, Occupational Health Nursing, Springer, New York, 1956. 2. M. L. Brown, "The Occupational Health Nurse's Need for Medical Direction," American Association of Industrial Nurse's Journal (August 1962). 3. M. L. Brown, "Safeguarding Human Worth through Medico-Administrative Skills," reprinted from Industrial Medicine and Surgery, 31:6, 254-255 (June 1962). 4. Occupational Skin Diseases, Division of Occupational Health, Public Health Service, U. S. Department of Health, Education and Welfare and U. S. Departi ment of Labor, U. S. Government Printing Office, Washington, D. C. ' 5. A. J. Fleming, C. A. D'Alonzo, and J. A. Zapp, Modern Occupational Medicine, : Lea and Febiger, Philadelphia, 1960. ! 6. "Industrial Nursing in the United States," an interview with Mary Louise Brown, R.N., reprinted from Industrial Medicine and Surgery, 33:1, 28-33 , (January 1964). i 7. R. T. Johnstone and S. W. Miller, Occupational Diseases and Industrial Medii ' cine, Saunders, Philadelphia, 1960. : 8. H. J. Magnuson, Anticipating Safety and Health Needs, U. S. Department of I Health, Education and Welfare, Public Health Service, from Public Health \ Reports, 75:1 (January 1960). 9. Chemical Safety Data Sheets: Properties and Essential Information for Safe Handling and Use, Manufacturing Chemists' Association, Inc., Washington, DC. ETC 03278 16 Effects of Toxic Agents John H. Foulger, Ph.D., M.D. The concept "safety" cannot be defined in a positive way, but only as the absence of its converse, "unsafety." Safety cannot be measured except as the risk, that is, the probability of injury, immediate or fore seeable. Safety has the same connotation regardless of the field of human activity under study. The means of achieving it and the results of failure of achievement, of course, will vary with the possible source of "unsafety." This book is concerned with problems of the chemical industry. A major source of risk of injury lies in the chemicals used or made. The places in which risk may exist include all those in which a worker might come into contact with chemicals--the research laboratory, the con trol laboratory, the pilot plant, the major manufacturing plant in all areas into which chemicals can enter. We emphasize laboratories as a site of risk of injury because in many years of industrial work, in visits of inspection to many chemical installations of widely differing programs and goals, we have, in gen eral, found far less attention paid to safe practices in laboratories.than in main production areas. Yet the laboratory is the place of birth of all new chemicals and the laboratory worker is the first to be exposed to any injury of which the new material might be capable. In thinking back over our own chemical training in high school, undergraduate and graduate schools, we cannot remember ever receiv ing any warning about health hazards from chemicals or any instruc tion on safe procedures. In the many hundreds of original articles in 250 ETC 03279 Effects of Toxic Agents 251 English, French, or German, which we have read in all fields of chem istry, we cannot remember any specific warning except as to flam mability or explosiveness. Programs of safety in the manufacture of chemicals are relatively newr. In this country many date only from the beginning of World War II. Yet the possibility of serious harm from chemicals was made known to the world by the newspaper reports of the first German "gas attacks" on the French and British armies in May, 1916. These ac counts and similar reports of subsequent attacks, often exaggerated for propaganda, concerned chemicals affecting the lungs and the skin --chlorine, phosgene, and "mustard." These were the only known ef ficient "war gases." The horrendous newspaper tales still persist in public memory so that even today people are more concerned over incidents in which chlorine is accidentally released or could be released from cylinders or tank cars than in possibly greater hazards from other chemicals. This general disregard of the health hazard from any but the "war gases" existed even as late as the beginning of World War II. All major nations engaged in the first great conflict conducted active research to find new chemicals with which to incapacitate the enemy or to deny him access to important terrain. Accidental exposure of military and civilian personnel to chemicals other than war gases gave much valuable information. But this was "classified" and never ap peared in literature accessible to the public. The United States Navy, from bitter experience with fires in gun turrets, knew of the dangers of gases and fumes generated from cordite burning in confined spaces and by research traced the hazard to nitro gen oxides from nitrocellulose. But this information was not readily available to physicians treating victims of the Cleveland Clinic fire in 1932. In that fire many patients, doctors, and nurses died after breathing oxides of nitrogen evolved from burning X-ray films (made with a nitrocellulose base) or a mixture of these oxides with carbon monoxide. Even today many chemists do not realize the hazards of a carelessly operated nitration reaction, and many raise their eyebrows when told that hydrogen sulfide, that valuable simple reagent used even in high school laboratories in inorganic analysis, shares with carbon monoxide the record as the greatest chemical killer of all time. Was this disregard of safety due to ignorance or to familiarity which "breeds contempt?" Was it thought that the relatively small quan tities of individual chemicals used or stored in the laboratory reduced any risk to a negligible level? Why was it considered that only "war" 252 Safety and Accident Prevention in Chemical Operations gases were hazardous and the "peace" gases not worthy of considera tion? Chemicals can injure in microgram quantities. A man can be killed by a shot from a 25-caliber pistol as easily as from a burst of a 16-in. shell. This indifference to safety in chemical laboratories is diminishing. Perhaps this is because we are now waging war on insect pests and the chemists making new insecticides may suspect that a chemical which will kill an aphid or a red spider or a mosquito might not have a very salutary effect upon a chemist. This chapter will indicate, with suitable examples, some of the risks inherent in chemicals if they are used carelessly and describe situations in which risk arises and outline general methods for its reduction. This is not a chapter on toxicology. Safety in the use and making of chemicals is not assured by perusal of manuals on toxicology or detailed knowledge of ultimate medical effects of '`unsafety." Luckily, safety can be attained by a much easier route, for existing texts on toxicology deal mostly with adverse effects of chemicals on laboratory animals, which are not necessarily the same as the effects on humans. They can consider only a small fraction of the many thousands of chemicals available and can seldom predict the possible physiological action of those yet "unborn." We would emphasize that the function of a safety program is "pre vention." No amount of knowledge, even if obtainable, on the ultimate disease pattern which might be produced by a chemical will necessarily insure safety in its use. The view so often expressed that it is difficult for a small company to insure safety because it cannot afford expensive toxicological studies is based on a fallacy. Currently hundreds and thousands of chemicals are made and used. All the toxicological lab oratories in the world working around the clock on each day of each year could not accumulate more than a miniscule of knowledge on the toxicology of one per cent of them. And how is safety to be estab lished while this minute amount of knowledge is being gathered? As a group the chemical manufacturers of the United States have paucity of detailed knowledge of toxicology. Physical State a Factor in Exposure Safety can be assured only by a carefully planned program which considers all conceivable ways in which the tools to be used, manual, mechanical or chemical, might offer health hazards, plus those factors ETC 03281 Effects o/ Toxic Agents 253 in the work terrain which could accentuate the hazard or spread it to other parts of the work area or even beyond plant limits. When the tools are chemicals this matter of terrain may be as im portant as that of the potential hazard at the point of their original use or production. A carpenter's hammer is not expected, of its own accord, to drive nails into a plank or to crush the finger of the carpenter. An auto mobile is not expected, when standing on a level with the engine dead, to dart suddenly across the road into a traffic lane. But the user or maker of a chemical must expect it to move in all directions unless human agency is used to confine it. Gases and vapors diffuse every where. Dusts are spread by the slightest breeze. Liquids, uncontained, flow to lower levels or seep through the walls of inadequate contain ers. Solids may exert a vapor pressure and solids may diffuse through other solids. This tendency of chemicals to move spontaneously unless adequately confined makes it inevitable that they may come into contact with or even enter the bodies of workers close to them. If the topography of the plant area allows, they may reach out to those not expected to be exposed or even to people living beyond the confines of the plant. Most of the chemicals in use today or being newly made are strange to nature. The human body may not know how to handle them or may not be able to deal safely with the quantities to which it is exposed. The entry of foreign chemicals into the body may interfere with nor mal body functions, and so set up an opportunity for traumatic injury by mechanical tools, or it may lead to any degree of impairment of health, even to death. Chemicals may come into contact with the skin, the outer covering of the eyes, the linings of the nose, mouth, throat, and the respiratory tract (bronchi, bronchioles, and the air sacs of the lungs), and the whole length of the digestive tract. If presented in adequate concentration, the contacting material may act at the point of contact, or it may be absorbed into the blood stream and be distributed throughout the body. Some of the invading chemical may be destroyed by the body defenses. Some may be changed to derivatives which may be less harmful or more harmful. Some may be excreted through the kidneys and have a local action on the ex cretory tubules or the urinary bladder. Sometimes a particular organ may take a chemical out of the blood stream and store it, only to liberate it at a later date under stress of disease. The possibility of contact of a chemical with any part of the body 254 Safety and Accident Prevention in Chemical Operation* depends upon the physical properties of the chemical and the efficiency with which preventive measures offset these properties. The possibility of injury at the point of contact depends upon the fundamental chemistry of the contacting substance vis-a-vis the chem. istry of the body tissue on which it alights. All injury by chemicals wherever it occurs, conforms to known laws of chemical reaction. The possibility of entry of a chemical into the blood stream depends upon its solubility characteristics and the biochemistry of the surface with which it makes contact and of the tissues between this surface and the blood or lymph vessels involved in the circulation of fluids throughout the body. The possibility of injury after invasion of the blood stream depends upon the specific chemical powers of the invader and the chemistry of organs or tissues to which it is transferred from the blood. All these possibilities, other than that of the initial contact, can be summed up in a definition of toxicology as "the study of the condi tions under which and the mechanisms by which a chemical, natural or synthetic, may, by virtue of chemical action, disturb function or struc ture of living tissues or organs and so impair health." It is of the essence of a safety program in establishments where chemicals are used or made that initial contact with the human body be prevented or reduced to a minimum and that duration of any un avoidable contact be terminated as promptly as possible. A detailed knowledge of toxicology is not needed unless there has been failure of prevention. Chemicals may appear in work areas as solids, of various particle sizes down to the micronic dimensions of fumes; as liquids, en masse or dispersed as mists or aerosols; and as vapors or as gases. Solids, as large particles and at room temperature, present a physical rather than a chemical hazard. They may have sharp edges which cut or they may be ejected from machinery as missiles. The outstand ing exceptions are the solid forms of the alkali metals, potassium and sodium and their hydroxides. By contact with moisture always pres ent on the skin or the mucous membranes of the eyes and nose, these materials may cause severe injury by production of heat of reaction and concentrated alkalinity. Solids finely divided as dusts and especially micronized dusts and fumes may be inhaled and pass down deep into the respiratory tract. Silicosis and berylliosis, the two most serious industrial lung diseases, result from breathing dust. Liquids en masse confine their attention to the skin and the outer covering of the eye. As mists and aerosols they may enter the respir- KTC 03283 Effects of Toxic Agents 255 atory tract. When ejected at high velocity, as may occur with hy draulic fluids, liquids can penetrate deep into the skin or the eye and cause severe injury by mechanical and chemical means. Vapors and gases may have action upon the skin or eyes, but their usual route of hazard is the respiratory tract. Liquids, vapors, and gases may penetrate the skin and reach the blood stream. One notable exception is carbon monoxide. Each of these states of matter requires its own consideration in a safety program aimed at prevention of contact of chemicals with any part of the human body in concentrations or total quantity capable of causing either immediate or delayed injury. Chemicals and the Skin Experience over many years shows that at least two-thirds of all industrial injuries due to chemicals are skin injuries. Dermatitis, whether of the simple contact type or due to allergy, while usually not of serious import, is unpleasant, uncosmetic, and may lead to much lost work time. If allergic, it may even make it advisable to change employment. Despite the relatively mild nature of most cases of chemical dermati tis, in toto the result may be as great a loss of work time as that due to the common cold and a much greater disturbance of employee rela tions. At first thought this might seem to be an absurd situation. Men do not work naked. Is not the skin easy to protect? Actually the most difficult problem of prevention of injury by chem icals arises when the chemicals used can act on or be absorbed by the skin. It is difficult, not so much because of lack of mechanical means of protecting the skin, as because of discomfort caused by some of these means and resistance to others. Clothing will reduce contact with chemicals. The face and eyes can be protected by suitable masks or goggles. Many tasks can be carried out efficiently by wearing suitable gloves, many can not. But chemicals can penetrate clothing or can be collected in clothing and form a reservoir from which they can diffuse toward and eventually reach the skin. In so doing not only do they contaminate the outer clothing but also the underclothing. The entrapment of chemicals, in particular hydrocarbon or chlorinated hydrocarbon solvents, between clothing and skin can cause severe burns. Clothing impermeable to chemicals is also impermeable, in the re verse direction, by chemicals, in particular water, produced by the body. No man can work in completely impermeable clothing for 256 Safety and Accident Prevention in Chemical Operationt more than about 20 min. Beyond this time he will suffer circulatory collapse. Even if we solve the problem of protection of the major part of the body with clothing, we still face the problem of shoes. Leather has been the traditional material for shoes,. Substitutes for leather must have one property which makes leather so suitable for foot covering They must absorb or allow the outward passage of moisture. Nobody can long withstand failure of the removal of perspiration from the feet Maceration of the skin, infection, and ultimately severe injury would follow any use of impermeable material for shoes. But leather can absorb many harmful materials, and leather shoes can build up and pass to the feet a dangerous reservoir of harm. Contaminated cloth ing, other than shoes, can usually be cleaned. But shoes cannot be decontaminated without risk of destruction. And they are too expen sive to be thrown away when contaminated. While it might seem that total prevention of contact of chemicals with the skin is not possible, it is possible to reduce to a minimum the risk of harm from that contact. The method is simple. A program of daily showers, with change to clean underwear and clean outer protective clothing, reduces the tirhe of contact of chemicals with the body and the possibility of absorption through the skin. This program requires adequate shower facilities as well as means for laun dering discarded contaminated clothing. This daily routine must be supplemented by more immediate action when there is spillage of strong acids which can destroy clothing, or of materials such as aliphatic and aromatic nitro- or amino-com pounds, or some chlorhydrins which can very rapidly penetrate the skin, or of solvents which, when trapped between skin and clothing, can cause burns. Protection against chemicals which rapidly penetrate the skin can now be afforded by impenetrable clothing ventilated by a continuous flow of cooled air. For many years much use has been made of "barrier" creams to prevent direct contact of chemicals especially with hands and arms. They are undoubtedly useful in many situations, but we have always had strong reservations against their unrestricted use. A barrier cream could actually become a reservoir of harmful substance from which some could reach and enter the skin. To be fully protective the cream must either be completely impermeable to the materials against which protection is desired, or it must render them inactive by strong adsorp tion or chemical reaction. There is, of course, a quantitative limit to the amount of contaminating chemical which a film of barrier cream can successfully repel. Further, the principle source of entry of mate Effects of Toxic Agents 257 rials through the skin is from massage which forces them into hair follicles. No worker can refrain from handling tools or performing motions with the hands which, in fact, lead to massage of barrier cream plus any harmful chemical which it carries into the skin. A barrier cream, used without careful consideration of all circumstances of its use, may actually increase the risk of injury. When barrier creams are used, workers often tend to think that their protection is assured. The cream, plus harmful materials it has trapped, is kept on the hands while eating, and it is allowed to stay on the skin beyond work hours. Quite often economy-minded men have allowed the cream to stay on their hands so that, at home, they can do dirty jobs such as cleaning cars or oiling and greasing mechanical tools. Thus they have not only prolonged their own possible exposure to harmful chemicals, but they have risked transferring contamina tion to their families and anything in their homes which they have touched. Even if barrier creams are used, a daily program of showers and clean clothing is still an essential part of a safety program. The only certain means of preventing either direct or remote (after absorption) injury by chemicals which come into contact with the skin is the use of plenty of water aided by soap. We emphasize plenty of water. The mere dipping of the hands for a second or two in a bowl of water or holding them under a stream from a faucet for an equally brief time is not adequate. This fact has a scientific explanation. With the exception of resinous materials, most chemicals can be removed from the skin by flowing water used in adequate quantity. Textbook figures on solubility in water apply only to small volumes, 100 ml or 1 1, and for these they express a saturation concentration. A forceful and continuous flow of gallons of water is quite a different matter. Many chemicals dissolve in water with the evolution of great heat. If only a small volume of water is used to clean the skin, the heat of solution may be sufficient to cause a severe burn. But a large volume of water will absorb this heat by virtue of water's own high specific heat. The chemical means of neutralizing or destroying chemicals on the skin should never be used. In addition to the dangers of heat of chem ical reaction, there is the possibility of injury' by the reagent used. We cannot successfully "baek-titrate" a strong acid by an alkali without risk of injury by the alkali or a strong alkali by an acid without risk of injury by excess acid. A chemical reagent which will destroy the contaminating material may also destroy the skin. 258 Safety and Accident Prevention in Chemical Operationt In rare cases it is best to remove the harmful material from the skin in two stages, first using a solvent and then following with soap and water and a final flushing with copious water. The initial cleansing with the solvent should be done quickly, and the water and soap stage reached as soon as possible. Many solvents useful in the initial cleans ing may facilitate absorption through the skin, and if the contaminated area is large, sufficient material may be so absorbed in a short time to cause serious illness. A solvent alone should never be relied upon. Protective gloves are frequently worn when chemicals are handled. Like other protective clothing, unless selected with due regard to their ability to resist the particular chemicals used, gloves may in crease the hazard. Rubber gloves are protective against many acids and alkalies but not against other materials. Carbon disulfide and aliphatic and aromatic amines and nitro-compounds can either rapidly penetrate rubber, natural or artificial, or can be absorbed by it and eventually diffuse through the glove to the skin. The best protective gloves are those which are cheap enough to be discarded when contaminated or which can be thoroughly de contaminated. Immediately after use they should be washed thoroughly, inside and out, and placed in an uncontaminated con tainer. The careless habit of leaving gloves on dirty equipment, such as the top of a filter press, makes their use a harmful and deceptive gesture toward safety. For a majority of chemicals, contact with the skin for a few minutes or even a few hours of the work day will be harmless if the daily routine of cleansing is employed. Others, if not promptly removed, may cause mild burns or reddening of the skin, and others may cause severe burns. But there are some compounds which without warning can react with chemical components of the skin to produce "allergens." Repeated contact for 5 to 10 days may be necessary or, in a few cases such as formaldehyde, a single severe burn might suffice. No ab normal reaction may be noted during this period of "sensitization." Then without any apparent warning, further skin contact with even a very small quantity of the chemical may lead to a violent skin reaction and even to general sickness. Some dermatologists have held the theory that workers, initially made sensitive to chemicals such as tetryl, can be "hardened" by repeated contact. But this is not the case with many sensitizing materials, and too often it is necessary to remove workers from all possible contact with the material which has rendered them sensitive. Chemical allergy can be a serious affliction. Treatment is often difficult. But prevention is simple--soap and plenty of water. Effects of Toxic Agents 259 Chemicals and the Eyes The eyes are as vulnerable as other exposed parts of the body to chemicals in the work atmosphere. Gases, vapors, mists, and aerosols may come into contact with the cornea, the outer covering of the eye, and if irritant or corrosive may cause severe harm. But the greatest source of injury is liquid splashed into the eye, or solid particles of alkali metals or their hydroxides flying into the eye. Actually there are very few chemicals which, except under very unusual circumstances, cause severe, permanent eye injuries. The most hazardous are strong acids and particularly strong alkalies. Sodium-hydroxide solutions are probably the major source of blindness in industry. Dimethyl sulfate is also a very dangerous material for the eyes. As with the contact of chemicals with the skin, contact with the eyes can be successfully handled by washing the eye with flowing water. The washing should last at least 15 min. The stream of water used should not be forceful lest mechanical injury be caused. It should be emphasized that "copious" water should be used. Mere use, once or twice, of the "eye-cup" is not adequate. Currently a number of very practical eye fountains for industrial use are available, and these should be installed wherever risk of eye contamination exists. As with the problems of chemicals and the skin, prevention is better than treatment. Safety glasses should be worn in any area in which chemicals are handled or stored. Suitable visors for special laboratory operations are available. Safety shields of laminated glass, tempered glass, or plastic should be placed between laboratory workers and any apparatus in which a reaction is carried out to diminish the risk of injury from explosion. Chemicals and the Respiratory Tract It is a fundamental fact of life that at each inspiration air is drawn through the nose and mouth and into the tree-like structure called the respiratory tract. This consists of the windpipe (the trachea), bronchi, bronchioles and the final air sacs (the alveoli). The bronchi and the smaller branching bronchioles spread like the branches and twigs of a tree and ultimately end in the leaves--the alveoli. In many ways the alveoli take on the part played by the leaves of a tree in the physical aspects of respiration. But respiration in the tree is from leaf to trunk, whereas in the human respiratory "tree" 260 Safety and Accident Prevention in Chemical Operations it is from the trunk (trachea and main bronchi) to the leaves (alveoli). Any harmful material dispersed in the air breathed will obviously be drawn into at least part of the respiratory tract. It will come into contact at least with the lining of the nose (and perhaps the mouth) and the trachea. Its destination beyond the trachea depends upon its physical and chemical properties. Of the usual routes of entry of chemicals into the body--through the skin, the respiratory tract, and the digestive tract--entry via the respiratory tract is potentially the most hazardous. While, for the average man, the total area of skin is not more than 2 sq m, the area of lung tissue exposed, at each inspiration, to chemical contaminants of the atmosphere may be of the order of 80 to 100 sq m. Whereas the skin is permeated with difficulty by most chemicals other than gases, the walls of the air sacs are permeated with ease by most ma terials and those chemicals which pass through the walls enter the blood stream and are distributed throughout the whole body. At each inspiration about 500 cc of air reaches deep into the lungs. The volume may be increased by deep breathing during physical ex ertion and the frequency, per minute, with which the lung walls are exposed to this volume may also increase with physical labor. The lining of the airway, the trachea and bronchi, is protected by two mechanisms. The surface in contact with the air is covered by a layer of mucus which traps particles and droplets entering the tract. Beneath this mucous layer innumerable cilia sweep mucus and the material it collects upward toward the mouth. By reflex action un usual quantities of mucus are coughed up and expectorated or swal lowed. It is fairly well established that particles or droplets of 5 to 10 microns diameter are dealt with by this mucus trap. Those of 3 to 5 microns are deposited on the walls of bronchi and bronchioles. Parti cles of 1 to 3 microns diameter are deposited directly on the walls of the alveoli. As particle size further decreases, deposition occurs less readily, and the contaminating material may be removed by simple exhalation. Small particles from % o to 1 micron do not easily settle out, but since they are subject to Brownian motion, they may come into contact with and be deposited on the walls of the airway and the alveoli. Changes in the velocity and direction of air flow in the respiratory tract, and especially the turbulence produced at the numerous points of division of larger into smaller bronchi, may lead to impaction of Effects of Toxic Agents 261 even larger particles on the lining walls. In the smaller bronchi the velocity of air flow is greatly reduced, and large particles aspirated to this point may be deposited by gravity alone. The depth to which gases, vapors, and mists may be drawn into the lungs depends to a great extent upon their solubility and ability to irritate. A highly irritant gas, such as ammonia, will react with the moist tissues into which it first comes into contact and produce such a reaction that the exposed worker will rapidly leave the contaminated area. If he is trapped and cannot leave, he may suffer acute laryngospasm and suffocate. Gases of moderate solubility may cause some irritation of the upper respiratory tract and so give warning of their presence even in low concentration. But in high concentration they may be drawn deep into the lungs in one or two breaths and have serious effects. An example is chlorine. The most dangerous gases of all are those of low solubility and ir ritancy, such as phosgene and nitrogen oxides. They may be absorbed without immediate appreciable effect, but six or more hours later chemical pneumonia or pulmonary edema develops. Recent interest in aerosols for medication has disclosed the fact that materials of even slight irritancy, inpinging on the linings of the nose or trachea, may lead to reflex constriction of the smaller air pas sages and a condition similar to asthma. The term solubility which we have used here refers to solubility in water, but when applied to dust particles or vapors of organic solvents it may not have such a simple connotation. The respiratory tract is lined with living cells of complex chemical structure and architecture. Each cell has an outer bounding membrane composed, in its simplest form, of a "sandwich" of lipid material between two layers of protein. Passage through this membrane depends on many factors including solubility in the water of hydration of the protein and in the lipid layer of the membrane. An increase in the ratio of lipid to water solubility generally facilitates entry through the cell wall. Inert gases, in general, easily pass directly to the alveoli and into the blood stream. The rate of absorption into the blood depends upon solubility in the blood plasma and the volume of blood flowing through the lungs in unit time. This latter factor will increase with physical activity. If these gases are taken up by any organs or tissues, ab sorption will go on until these tissues and the blood are saturated. No more gas can then be absorbed. The process is reversed on removal to fresh, uncontaminated air. Gas in the venous blood flowing to the lungs is exhaled through the 262 Safety and Accident Prevention in Chemical Operations walls of the alveoli and, with depletion of saturation of the blood gas taken up by the tissues is released into the blood stream. The complete removal of gas from the body may take many hours if it is very soluble in any body tissue. Vapors of solvents, if they are not destroyed in the body, behave in general like inert gases. An interesting example of slow elimination is given in the writings of the renowned French physiologist, Claude Bernard. He conducted his research on many types of animals, includ ing sheep. To increase his meager research funds, the carcasses of the sheep, after operation, were sold in the local meat market. This pro cedure was quite profitable for a time and then, suddenly nobody would buy the sheep. What wras the reason? Bernard had changed the an esthetic used in his work from chloroform to ether. Very little chloro form was needed to anesthetize the sheep and that little rapidly left the body. But considerable quantities of ether were required, and the ether persisted in the fatty tissues and gave the meat of the sheep an objectionable odor and taste. The problem of solubility also enters into the ultimate fate and ac tion on the body of inorganic dusts. Materials, such as silica, con sidered by the chemist as highly insoluble, should, logically, not be passed easily through the alveolar walls. But here another body mechanism comes into play. The complex cellular structure of the wall contains "wandering" cells which act as scavengers and engorge foreign particles. These cells are able to pass through the walls of blood capillaries and lymphatics draining the lungs. They flow to the lymph nodes around the bronchi and here, by an action not yet explained, the silica, if it be of the correct type, can cause damage. The resulting disease, silicosis, is one of the most serious in industry. It is possible that materials such as silica are more soluble in the com plex aqueous medium, cytoplasm, than in pure water. It is also pos sible that adsorption on the protein of enzyme systems might lead to chemical reactions which produce damaging silica complexes. The problem of silicosis should warn against too complacent accept ance of "test-tube" insolubility as a basis for the assumption that a particular solid, as dust, provides no risk if inhaled. It does not matter whether we are dealing with the problem of in halation of an inert gas, such as helium, or argon, or of the vapor of a solvent of low chemical reactivity with the chemicals of living tissue, we must never forget the possibility of reduction of the oxygen con tent of the inhaled air to a point at which normal respiration is diffi cult. This is at about 16% by volume. While at this figure of 167c oxygen, serious injury would not be caused by breathing an inert gas, Effect$ of Toxic Agents 263 many workers might suffer from headache and dizziness and from changes in the circulation which might render them prone to injury if they are using tools or operating moving equipment. Theoretically, prevention of inhalation of chemicals contaminating the air we breathe should be relatively simple. The mouth and nose, through which air first enters the body, offer only a few square centi meters of orifice. These could be covered by a suitable mask allowing the passage of air but not of dust, or a mask attached to a canister which adsorbs dusts or vapors. This method of protection is indeed available and useful but only under very restricted conditions. A filter mask which is capable of holding back small particles of dust necessarily offers some resistance to the passage of air and therefore may hinder the normal, unconscious act of breathing. The mask will be uncomfortable, especially on hot, humid days, and the filter mate rial will eventually become saturated. A mask with a chemical can ister will rarely hold back air concentrations of more than 2% by volume of a vapor or gas, and it will do this only for some 20 min. Such a canister mask is also uncomfortable to the wearer. It is never safe in an emergency when the concentration of the contaminant of the air is unknown, and it is never safe when the oxygen content of the air is below 16% by volume. This simplest form of prevention of inhalation of harmful chemicals should be used only for very short-term activities in laboratories, when the possible concentration of the material against which protection is desired is known to be low, and it is certain that the filter material or contents of the canister will, in fact, hold back the harmful chemical. In emergencies or for protection against concentrations above 2% by volume and for periods longer than about 20 min, that is under conditions in which canister masks are not adequate, personal protec tion is afforded by air-line respirators or by a self-contained breathing apparatus supplying compressed air or oxygen. Like the simpler canister mask, such apparatus must be used with care. It must be kept clean and in proper working order at all times. Whenever air is supplied, either directly to an airline from a compressor, or as pre compressed air from a tank, this air must be free from contamination. A worker, who is calling for protection against, say, hydrogen sulfide, is scarcely helped by a supply of nitrogen to his airline respirator or by compressed air containing finely dispersed oil or carbon monoxide from the compressor. This purely local protection of the points of entry of harmful sub stances into the respiratory, tract is neither practical nor efficient for the hourly and daily demands of the laboratory or the manufacturing 264 Safety and Accident Prevention in Chemical Operations plant. The only satisfactory way to assure protection of workers 13 by ventilation. In recent years state and federal laws and regulations, following on years of voluntary action by the chemical manufacturing industry have required precautionary labeling of containers of hazardous mate rials entering the home or industrial plants. Whenever a chemical of fers the risk of injury by inhalation, the container label must carry the phrase "use with adequate ventilation" or "use only with adequate ventilation." The word "adequate" is difficult to define. Since ven tilation is required to control all physical forms in which contaminants appear in the atmosphere, we would suggest as a definition, "Adequate ventilation is such ventilation immediately around the worker that dusts do not settle on his unprotected skin of a type or in an amount which can cause harm and that at his mouth and nose level there are neither adequate concentrations nor total quantities of gases, vapors, mists, or dusts to cause injury when inhaled or swallowed." We would consider anything short of this to be inadequate ventilation. This definition would appear to require knowledge of the minimal concentration or total quantity which could be harmful--knowledge which, as we have already explained is not available for more than a very few materials and is not available when a new chemical is first prepared in the laboratory. Further, since in both laboratory and plant the worker's exposed skin area, nose, and mouth are not fixed in space, the definition demands a system of ventilation operative at any point in laboratory or plant at which that exposed skin and that nose and throat may be located at any time during the daily work. In the early days of protection by ventilation it was thought that the desired end could be reached by dilution. Volumes of fresh air were poured into the workroom in the hope of reducing the overall con centration of atmospheric contaminants to a level incapable of causing harm. This procedure was expensive, inefficient, and in the case of materials which might dust, it could actually induce a hazard which otherwise would not exist. The modern method is to ventilate at the source of possible origin of any physical form of a harmful material and to ventilate by suction so that it could not approach the skin, the nose, or the mouth of the worker. Localized suction is applicable to any scale of operations in laboratory or plant. It requires less overall energy than the crude system of dilution and need be operated only at any particular site during the period of actual possible exposure. In manufacturing plants, hoods and negative pressure can be in stalled over reaction kettles, filter presses, drying and flaking apparatus. ETC 03293 Effects of Toxic Agents 265 and packaging equipment. In the laboratory this form of ventilation has been traditional in the chemical hood. Whether in plant or laboratory, ventilation by removal at the source of origin of air contaminants is efficient only if the equipment used is kept in good operating condition and is used with intelligence. Since this phrase "used with intelligence" may seem unnecessary to some, we would illustrate it by observations on the use of the chem ical hood. The first acquaintance of any future chemist with the chemical hood or "fume cupboard" was probably made in high school. And some of the bad habits which later might plague him were also probably ac quired there. The hood has always been a structure with a movable front sash and at its back there was a duct carrying a fan. It was used to store apparatus such as the old "Kipp" generator for produc tion of hydrogen sulfide or for carrying out reactions in which this gas or other reactive gases were used. This storage function of the hood was necessary because the Kipp generator usually leaked and hydrogen sulfide was undesirable because of its odor of "rotten eggs" in the general laboratory area. This habit of using chemical hoods as storage places has extended beyond the original purpose as storage for equipment continuously subject to leakage. In too many laboratories the hood is now the re pository of reagents and equipment not currently in use which would "clutter-up" the laboratory bench. The modern chemical hood usually has a baffle plate toward its rear with a clearance of an inch or so at the bottom or sides through which the fan, when operating, sucks air. As more and more reagent bottles and unused apparatus are placed in the hood for storage, two events occur. First, the movement of air back to the outlet duct is prevented, because much of the space between the bottom of the baffle plate and the floor of the hood is virtually closed by stored material. Second, the air drawn into the hood, that is, air which should be carrying con taminants away from the chemist working in the laboratory, is bounced off the bottles and other stored objects, and the turbulence resulting may actually force air out into the laboratory. There are other common errors in the use of hoods which we would consider "unintelligent." Most hoods will not operate efficiently if the front sash is raised more than 4 to 6 in. A hood with the sash raised half-way or completely is very poor protection. Again, the turbulence caused by obstacles in front of the baffle plate can also be caused by the body of a chemist standing close to the front of the hood or by bulky apparatus erected just outside the front. 266 Safety and Accident Prevention in Chemical Operations Finally, if the hood is quite properly used to store equipment from which gases or vapors might leak, the habit of the economy minded to turn off the fan at the end of the work day, may have very vm' fortunate consequences for the unwary who might later open the hood to set up apparatus or remove equipment. In outlining the content of a sound safety program, we stated that it should consider '"those factors in the work terrain which could ac centuate the hazard or spread it to other parts of the work area or even beyond plant limits." It is unfortunate if, in installing ventilation to protect one group of men, another group is placed in jeopardy. Air taken from, say, a laboratory and carrying contaminating chemicals must be vented somewhere. Is the output stack of the ventilating system of adequate height and properly situated in relation to other buildings so that there is no risk of entry of its exhaust into neighbor ing buildings? Is the stack of sufficient height that, under conditions of high humidity and low wind velocity, harmful gases or vapors will not fall to the ground between buildings? Under this heading of work "terrain" we would also include the more limited area of the laboratory or work room itself. Often the ventilating apparatus has been installed when very few obstacles, including the bodies of workers, were in the path of air flow. Changes in the placement of equipment, addition of permanent machinery or apparatus, and occupation of the work room by more people than originally intended or relocation of their work positions in relation to the air flow, could have the same general disturbing effect as we have described when discussing the "intelligent" use of a chemical hood. Finally, cleanliness of equipment, of containers of reagents, and of even the walls of the laboratory or production area may be a factor in deciding success or failure of an apparently adequate program of protection. Chemicals and the Digestive Tract Risk of injury by swallowing chemicals is not usually considered important in industry. Yet it does exist and may actually be signifi cant. In the laboratory careless use of pipettes is an obvious source of injury to the mouth. If the material pipetted has a high-vapor ten sion, vapor may be inhaled. In the more modern, more efficient laboratories, of course, pipetting is now mechanical. In. heavily dusted areas the larger particles of dust drawn into nose and mouth will be desposited there and, if they have no warn Effects of Toxic Agents 267 ing local action, will be swallowed. Aerosols containing large droplets may also lead to swallowing. In industry a serious risk of swallowing harmful substances exists if workers are allowed to eat lunches or snacks during the "coffee hour" without first thoroughly washing hands and face, or if they are allowed to take food, chewing gum, or chewing tobacco into con taminated work areas. This is a practice very difficult to control. To produce serious injury by swallowing, greater concentrations or total amounts of chemicals are usually needed than are required to injure by inhalation. Many chemicals are not easily absorbed through the walls of the digestive tract- unless they first injure those walls. Those which are absorbed into the blood stream pass through the liver in which important detoxifying mechanisms operate. The digestive disturbances and loss of appetite, which are so often early symptoms in developing chemical poisoning, are not usually due to direct action on the operations of the digestive tract itself but rather to effects on the total body functions by chemicals which have entered the body by any route. Again, prevention of injury depends upon control of movement of harmful materials into the work area and meticulous cleanliness of the worker. Water and soap again are potent tools for prevention. Examples of Inadequate Protection We have outlined major sources of risk of injury by chemicals in the laboratory and the manufacturing plant. We have also de scribed in general terms simple means of reducing that risk. Unfortu nately there are many sceptics in this field of safety with chemicals. To help convince them we cite a few examples of what follows failure to apply simple means of protection. These examples relate to the points in our general discussion. Dermatitis, the most frequent form of industrial injury due to chemicals, can be prevented by cleanliness of clothing and person. Inadequate cleaning of clothing may perpetuate it. Three workers were showered by a mixture of dilute hydrochloric acid and aromatic chlorine compounds when a still broke. They removed their outer clothes and were said to have cleaned them. But all suffered chemical derma titis for 3 weeks. Their dermatitis disappeared promptly when all clothing worn at the time of the accident was very thoroughly cleaned and left to hang in fresh air to dry. A worker handling a rubber anti-oxidant became sensitized and was appar ently removed from all possible contact with the offending material. His 268 Safety and Accident Prevention in Chemical Operation$ dermatitis did not disappear. He was still wearing garters, the "elastic" f which was contaminated. When these were discarded, he recovered. Clothing contaminated by chemicals should not be worn at home. It should be thoroughly cleaned either on the plant or by cleaners ex perienced in handling such materials. The wife of an operator in a small dynamite plant complained to the plant manager that she and her children frequently suffered from severe headaches The operator had "purloined" a discarded glove from the plant. The glove was of a type rejected by the plant because the palms were coated with rubber. The rubber had absorbed nitroglycerin. This chemical rapidly passes through the skin. The children played with the glove and the wife often han dled it in her daily house cleaning. Beryllium dust is the source of a very serious lung disease--berylliosis Workers in plants handling beryllium are now well protected. But in one plant, at least, this protection was spoiled by shortsightedness. A worker was allowed to take home his contaminated work clothes. His wife laundered them and in doing so breathed sufficient beryllium dust to produce lung injury. Gloves made of rubber or rubberized materials may not be good protection against liquids which can penetrate them. The rubberized gloves mentioned above were discarded in the safety pro gram of the dynamite plant because nitroglycerin will penetrate rubber. An outbreak of painful dermatitis of the fingers among "doffers" in a plant making viscose rayon was found to be due to penetration of rubber gloves, used as protection against the acid-spinning bath, by carbon disulfide liberated from the regenerating viscose. The outbreak was halted by careful selection of the gloves after tests for permeability by carbon disulfide and the wearing of a light cotton glove beneath the rubber. Barrier creams are useful when used with care under proper cir cumstances. Sometimes they can unexpectedly make matters worse. An epidemic of dermatitis broke out in a plant making a synthetic fabric by impregnating cotton cloth with a plastic. The solvent was methyl ethyl ketone, which was recovered and re-used. The plant safety department ad vised use of a barrier cream but the condition of the workers using it became worse. A research chemist at the plant solved the mystery. Under the con ditions of use, methyl ethyl ketone was partly converted to diacetyl. This compound, in contact with the skin, apparently polymerized to form a quinone which combined with proteins of the skin to produce the allergen which caused the dermatitis. This chemical process was facilitated by the alkalinity of the barrier cream. Diacetyl had apparently built up in the recirculated solvent to a significant concentration. Careful fractionation of the solvent before re-use eliminated the trouble. Frequent washing of the hands with soap and plenty of water may remove a hazard caused by absorption of chemicals through the skin. Effects of Toxic Agents 269 In a military arsenal a group of women was engaged in weighing plaques of a propellant composed of nitrocotton impregnated writh a high concentra tion of nitroglycerin. After weighing, they sewed the plaques together. The girls would work for a few days and then quit, complaining of severe head aches. The rapid labor turnover was threatening the work program. The difficulty was overcome in a very short time when the girls were required to wash their hands thoroughly at the end of each work hour. When washing to remove contaminating chemicals, plenty of water should be used. When part of the function of water is to remove heat of reaction, flowing water from a hose or a shower is essential. A plant using titanium tetrachloride was amply provided with showers at every point at which workers might be splashed with this irritant mate rial. The workers were equipped, in some operations, with complete rubber protective clothing. They were also thoroughly indoctrinated in safety prac tices, including the use of water to remove any of the chloride which splashed on their clothing or bodies. A young, inexperienced worker was accidentally sprayed with a large volume of titanium tetrachloride. He panicked and, in stead of using the shower close at hand, rushed to a large vat of water and jumped in. Titanium tetrachloride reacts with water with evolution of great heat. The still water of the vat boiled and the worker was severely injured. Flowing water from the shower would have taken up the heat of reaction and carried it away from the man's body. An operator in a small chemical plant carelessly handled a drum of oleum. A defective bung fell out, and oleum poured down the man's leg and into his calf-high "cowboy" boots. Fellow workers at once turned a hose on him but he fought them off. Before they finally overpowered him, his right ankle and foot were severely burned and corroded by the acid. He had seen steam generated when spilled acid was diluted with water, and he did not know enough about the hazards from oleum to realize the usefulness of plenty of water. Sometimes it is best to precede the use of water in cleansing con taminated clothes or skin by the proper use of a solvent. This must then be removed by soap and water. Tetraethyl lead is a highly dangerous compound. It very rapidly pene trates the skin. All workers who may come into contact with more than minute quantities of this compound, during its manufacture or at blending plants, are thoroughly indoctrinated into procedures for handling spillage. The chemical is transported in tank cars and at blending plants it is trans ferred to storage tanks. At the point of transfer, workers are protected by proper clothing and two showers are provided, one delivering kerosene, the other water. In unloading a tank car the men work in pairs. The pipe from the tank car to the storage tank ruptured during such an unloading, and a worker was literally bathed in tetraethyl lead. He at once stepped under the kerosene shower and, assisted by his buddy, flushed the chemical from his clothes and body. He then stepped under the water shower and was thor oughly bathed with soap and plenty of water. This man, accidentally exposed 270 Safety and Accident Prevention in Chemical Operation* to a large volume of one of the most dangerous chemicals known, was not injured to the least degree by this accident. In contrast to this skilled handling of a potentially serious accident consider the following: A gang of laborers was employed in digging a drainage ditch in a plant man ufacturing tetraethyl lead. The foreman failed to note that an old drain ran parallel to the new one and that this old drain carried water contaminated with tetraethyl lead. Water from the old ditch seeped into the new. The feet of the laborers were not properly protected. Some acquired tetraethyl lead poisoning. Copious flowing water is as valuable in cleansing the eyes of chem icals splashed into them as it is in cleaning the skin. Prompt washing of the eyes with flowing water for at least 15 min can, in most cases prevent more than temporary eye irritation. A driver whose car radiator was beginning to freeze drove into a filling station and asked for a methyl alcohol anti-freeze. An inexperienced attendant unscrewed the radiator cap and without waiting poured in methyl alcohol. There was a violent eruption and the hot mixture of radiator water and alcohol hit the face and eyes of the attendant. His eyes were immediately flushed with water, and he was sent for medical attention. The outer surface of the eyes rapidly became cloudy and were described as looking like "the white of a boiled egg." But, thanks to immediate removal of the contamina tion, damage was restricted to the outer layer of the cornea and within three weeks this subsided and the eye was restored to normal. Canister masks may be very useful under limited conditions. But care must be taken that, even for these conditions, the canister is ade quate to hold back the harmful vapors or gases against which protec tion is needed. In a paper-making factory plans were made to kill slime in vats by use of a compound of diethyl mercury. It was planned to add this to the contents of a vat and mix by using air from a compressed air line. Diethyl mercury is quite volatile and the agitation with air produced a harmful concentration of the vapor in the work area. The safety department of this plant had been informed, after careful inquiry from supposedly re sponsible sources, that an all-purpose canister mask would afford protection. . It did not, and two serious cases of poisoning resulted. Apparently the advising "authority" was not aware that a canister which would absorb va pors of metallic mercury will not hold back vapors of alkyl mercury com pounds. Serious and often fatal accidents occur when the oxygen of the atmos phere of the work area is reduced below the concentration needed for normal respiration. This situation occurs in all major conflagrations, ETC 03299 Effects of Toxic Agents 271 and can occur if high concentration of inert gases are liberated, pro duced or used where men work. In past years public utility companies supplying electricity to large cities have had bitter experience in this problem. The transformers in large build ings "ere often in closets in sub-sub-basements. These transformers occationally overheated and power supply to the building failed. A service man was sent out and failed to return. When assistance was sent, the first man was found collapsed or dead at the foot of the transformer. In such cases the transformer fluid was an oil which, when overheated, absorbed all the limited supply of oxygen in the restricted volume of the closet. The service man walked directly into an atmosphere of nitrogen. During a visit to the physiology laboratory of a famous university, the laboratory director volunteered to demonstrate effects of breathing oxygenhelium mixtures. After adjusting leads to various recording devices, he donned a face mask attached to a battery of gas tanks. At his signal an assistant turned a valve. He took one or two breaths, became blue in the face, and his heart beat became rapid. The mask was promptly removed and he quickly recovered. Someone, without warning his fellows, had re placed the tank containing oxygen and helium with a tank of pure helium. Some of the recently developed saturated poiyfluorinated aliphatic hydro carbons are chemically and physiologically very inert. They are used as refrigerants, as jrropellants for aerosol bombs, and as solvents. High con centrations of these materials, as gases or solvent vapors, accidentally lib erated have had the same effect on exposed workers as would high concen trations of inert gases, and by the same mechanism--reduction in available oxygen. Cleanliness of work areas and of equipment handled in the course of the daily work may be a very important item in a program of safety with chemicals, especially if the materials involved can be absorbed through the skin. In some older chemical manufacturing plants, often for very specific reasons, parts of the work rooms may be constructed of wood or covered with wood. Wood, like leather, can absorb many materials deposited on it and in time these wooden structures become a veritable reservoir from which, if volatile, vapors can be emitted. Some years ago, during a study of methods of protection of workers against inhalation and skin absorption of nitroglycerin in the manufacture of dyna mite, surveys were made of atmospheric concentrations of the chemical in work houses under varying conditions of ventilation. The walls of these houses, for safety reasons, were of wood. Settling of dust containing nitro glycerin resulted in absorption of this chemical into the wood. During the work hours ventilation systems were adequate to maintain a safe atmospheric concentration of nitroglycerin vapor. But after the day's work was ended and the ventilating system shut off, vapors from the walls built up at mospheric concentrations beyond those considered physiologically safe. Spraying the walls with water would temporarily lower the vapor con- 272 Safety and Accident Prevention in Chemical Operations eentration, but once the walls were dry, with ventilation still shut down th process of evaporation from the walls started again. 'e The base beta-naphthylamine is very easily absorbed through the shin It also can be a dusty material and can exert a significant vapor pressure Beta-naphthylamine is not toxic, in the usual sense of the word. It has no action on most organs of the body. But, after absorption, it is concentrated in the urine and is absorbed by the walls of the urinary bladder. It is then converted into a hydroxy beta-naphthylamine which is a potent carcinogen During a study of this compound, many pounds of it were used in a biochem" ical laboratory. As the study progressed methods of determination of beta- naphthylamine in the urine were attempted, using fluorescence as an indi cator. Workers in this and other laboratories provided urine specimens which were usually placed temporarily on the biochemical laboratorv bench We were much alarmed when all were found to give strong fluorescence, indi cating excretion of considerable quantities of the naphthylamine. Some of the contributors of the specimens had worked with the chemical or with animals which had been fed the chemical. But others, so far as we could discover, had never been exposed to it. Yet their urine specimens, after standing in this laboratory, were positive for beta-naphthylamine. When the routine was changed and no urine specimens were allowed to enter the bio chemical laboratory, none showed fluorescence. Apparently during the months of work with the amine this laboratory, especially the walls and ceiling, had become contaminated. A very thorough cleansing removed the contamination. If the problem under study, cancer of the bladder caused by beta-naphthylamine, had not been of such a serious nature, it is doubtful whether the possibility of contamination of a whole laboratory would ever have been given serious thought. One of the rare effects of poisoning by trinitrotoluol is damage to the bone marrow. It appears to occur only in a few specially sensitive individuals, but in these it can follow absorption of much smaller quantities of the chemical than are usually considered harmful. Bone marrow damage was found in a worker in an explosives plant who, apparently, never was engaged in any plant operations which would involve TNT. He was the driver of a small locomo tive on a light railway used to cany boxes of the chemical from the packag ing area to the magazine or to the railhead. But he did occasionally help in loading these boxes on to the cars drawn by his locomotive. Chemical tests showed that the outside of these boxes was contaminated with TNT. When a ventilating system is installed to prevent atmospheric con tamination in one area, it is wise to study carefully the position of the output stack of the system lest protection of one group is obtained at the expense of another. We have described a number of examples of misplaced enthusiasm in an article, "Use Only with Adequate Ven tilation" published in Air Engineering (Vol. 4, No. 6, pages 23-30, June, 1962). In these days of air-conditioned laboratories, great care must be taken that the mechanisms for removal of atmospheric con tamination due to chemicals--the chemical hood or temporary exhaust ETC 03301 Effects of Toxic Agents 273 systems--do not result in recirculation of chemicals via the air-condi tioning system. In these days of public concern over pollution of the atmosphere, everyone responsible for operating either a laboratory or a plant bears the burden of assuring that no harmful quantities of his chemical tools or harmful products or wastes can reach beyond the bounds of property under his immediate control. Even though his site of operations might be far from a residential area, and none but a few persons might ever be expected to approach areas around this site, conditions could sometimes arise to produce unforeseen risks. An experimental nitration operation was being carried out in a small labora tory adjacent to a wooded area. For some unexplained reason the chemist de cided to vent the nitrogen oxides produced by his reaction through a duct which passed through the roof of the hut and was then carried vertically downward parallel to the outer wall and opened a few inches above the ground. All went well for some time. Then came days of high humidity, mist, and small wind movement and that movement was directly toward the woods. Nitrogen oxides accumulated in high concentrations and lay close to the ground in the woods. Luckily, at that time, there were no wanderers in those woods, otherwise a serious situation might have arisen. A small plant whose operation required the use of high concentrations of an alkali cyanide solution, carefully programmed the removal of cyanidecontaminated wastes from the operating area. The wastes were collected in a catch basin away from the plant and situated on the edge of a wooded gully. This small reservoir and attached pumping equipment was inspected daily. On a humid, misty day, with no wind movement, a worker inspecting the reservoir and pumping apparatus near it became dizzy and almost collapsed. Apparently hydrocyanic acid gas, which is always liberated in small quanti ties from cyanide solutions by the carbon dioxide of the air, which forms a stronger acid than HCN, had become concentrated in the mist to a degree capable of causing respiratory disturbance. Whenever gases or waste solutions capable of evolving gases are discharged from a plant or may, by accident, escape from equipment anywhere on the plant, atmospheric conditions may lead to hazardous situations. In the old "chamber process" for making sulfuric acid, sulfur dioxide from burning sulfur or pyrites was mixed with nitrogen oxides generated from sodium nitrate. The mixture of oxides with water vapor was pumped suc cessively into a series of chambers. A leak occurred in a pipe line carrying the crude oxide solution at a time when the external temperature was well below zero. The solution rapidly froze and formed a small deposit below the point of the leak. When the spring thaw' came, a craftsman was sent out to inspect the pipe line and repair leaks. He worked above the previously solid, but now thawing, mixture of oxides long enough to inhale nitrogen 274 Safety and Accident Prevention in Chemical Operations oxides in a lethal quantity. This same hazard of evolution of nitrogen oxides from frozen reaction mixtures was experienced in the manufacture of TNT during World War II in plants located where winter temperatures were verv low. TM EXPOSURES OF NONOPERATING PERSONNEL Safety from injury by chemicals is a "freedom" and, like all free doms, can only be assured by "eternal vigilance." It is not sufficient that a laboratory or a manufacturing plant establish on paper a pro gram of operations which will protect workers. It must continually strive to educate those workers and search for the best means of re ducing risks. Many chemical companies and research centers have well-established safety programs, and a major item in them is the monthly, or some times even weekly, safety seminar. But who attends these meetings? Are they not, usually, confined to those who are actively concerned with the making or using of chemicals? Are clerical personnel also instructed in the hazards which chemicals may afford? Are guards or those who clean laboratories at night so instructed? The chemical manufacturing industry of this country has built up a magnificent record of on-the-job safety and is continually improving it. But when, a few years ago, a comparison was made of the fre quency of lost-time injuries incurred on the job to the frequency, among the same workers, of injuries sustained away from the job, it was found that the ratio of off-the-job to on-the-job injuries was 5 to 15. Safety education had apparently been focused on risks while at work and not on risks in general. With rapidly increasing frequency the products of chemical labo ratories and plants are being used in and around the home. A recent federal law has required labeling of containers of hazardous chemicals "intended or suitable for household use." But anyone who has been concerned with safety in the handling of chemicals knows that labeling may be ineffective for, too often, the chemical which has caused trouble has been removed from a properly labeled container and placed in one not labeled. The "purloining" of chemicals from laboratories or plants for home use is not infrequent and most often includes transfer of materials from labeled to unlabeled containers. Some years ago an accident occurred on the West Coast which pointed up the danger of this practice. Two young men, workers in a chemical plant, took a large quantity of carbon tetrachloride from a drum. They went out side the town to a pit over which they could drive their car so that they could work on the transmission. Thev used the carbon tetrachloride to ETC 03303 Effects of Toxic Agents 275 degrease the differential gear. They were found dead under the car. The drum from which they had taken the solvent was adequately labeled. The plant in which they worked conducted a good safety program, including fre quent safety seminars. In fact, shortly before the accident, the subject of a safety talk had been carbon tetrachloride. But the two young victims of carbon tetrachloride were not at the safety meeting because they were office workers. Some Chemical "Criminals" While this chapter is not intended as a thesis on toxicology, we think that emphasis on a small group of chemicals, appearing frequently in the laboratory, the plant, and the home, and which in our opinion war rant the title of chemical `'criminals," might round out our plea for continued caution. The four chemicals are hydrogen sulfide, nitrogen oxides, benzol, and carbon tetrachloride. We have chosen these four for a number of reasons. First, they are frequently encountered in laboratories at all stages of chemical education as well as in chemical research. Second, they are such familiar items that they are treated with indifference and are used carelessly. Last, they have without doubt killed or injured more people in peace time than any other compounds, with the exception of carbon monoxide, which has been a prime chemical killer since the days of the charcoal burners and the first forgers of metals. Hydrogen sulfide is the first gaseous chemical reagent which the student meets in his study of inorganic analysis. For his analytical work it is supplied to him either from the historic Kipp generator, or, in modern times, from tanks in which it is compressed to a liquid. Both generator and tanks are apt to be stored in the chemical hood. The Kipp almost invariably leaks. The tanks can leak if not care fully tended. Traditionally, the one property of hydrogen sulfide well known to students is that it has the odor of rotten eggs. In such eggs the gas is produced by decomposition of organic sulfur compounds in the egg yolk. But, also traditionally, it is never explained to the student that this odor is perceptible only when the gas is present in low, unpleasant but harmless concentrations. Dangerous concentrations of hydrogen sulfide paralyze the olfactory nerves. This property is the cause of many accidents, some near misses, too many fatal. I fear this gas more than any other chemical, because of personal experiences and experiences of my friends. Some years ago, while a chemistry student in the University of London, a fellow student and I went to the chemical hood intending to start a gravi 276 Safety and Accident Prevention in Chemical Operations metric analysis working under the hood. My friend reached the hood first The ventilating fan was not operating. He raised the front sash and put fijg head into the hood. He at once staggered back and collapsed. I dragged him to an open window. He was conscious but unable to speak or move for several minutes. When he recovered, he did not know what had happened The usual Kipp generator was stored in the hood and, as usual, it leaked and filled the hood with a dangerous gas concentration. Some years later my wife, as a pre-medical student, suffered a similar "near-miss." After class hours she decided to complete a Kjeldahl analysis for protein nitrogen. She planned to use the chemical hood since dangerous nitrogen oxides would be liberated. She opened the hood, but remembered nothing more until she found herself at the exit from the laboratory, struggling to get to her feet. She does not know how she reached the exit. It was Saturday and no other person was present. The odor of hydrogen sulfide was noticed in the basement of a famous toxicology laboratory near to a room in which tanks of the chemical were stored, for use in a program of lead analysis. When the storage room was approached, with proper precautions, a janitor was found unconscious at the entrance. Inside the room the laboratory manager was dead, near a leaking gas tank. Hydrogen sulfide is a frequent cause of deaths of workers on sewage repair. Usually they are multiple deaths. The companion of the first man to collapse goes in to rescue him. Ignorant of the properties of the gas, he fails to provide himself with the only respiratory" protec tion adequate for the situation--a self-contained breathing apparatus delivering compressed air or oxygen. Sometimes man after man at tempts the task of rescue and becomes a victim. A person not adequately equipped should never try to rescue a worker felled by hydrogen sulfide. He may merely provide another fatality for, by almost instantaneous action, the gas paralyses its victims so that they can neither help themselves nor call for help. Nitrogen oxides are liberated whenever organic matter is heated with nitric acid. Nitration reactions are common in student laboratory work in both analytical and organic chemistry. They are equally common in research laboratories and in chemical manufacturing. Nitrogen oxides are sometimes obvious as "brown fumes," but not always, and the degree of brownness is not related to the extent of the harm caused if they" are breathed. The oxides may not give any warning, by irritating the eyes or throat, but within 6 or more hours severe lung injury" may develop. We have already mentioned the fire at the Cleveland Clinic in which many patients, doctors, and nurses were killed by breathing these gases. A faulty heating apparatus started a fire in a basement in which X-ray films were stored. The films contained a nitro-cellulose base. Effects of Toxic Agents 277 Benzol is a useful solvent and was formerly a common constituent of metal polishes, plastic woods, and rubber cements. It is probably found in most laboratories and is not usually regarded with suspicion. High concentrations of benzol vapors are anesthetic, but a single heavy exposure, even if it leads to loss of consciousness, will seldom cause lasting harm. The great danger with benzol lies in damage to the bone marrow which follows frequent breathing of low concentrations of the vapor. The disease produced is similar to leukemia and, like leukemia, is sel dom curable. Carbon tetrachloride is the last of our "criminals." It is a very useful solvent especially for removing grease from fine electrical equip ment. Its careless use has caused much illness and many deaths. We have already cited the case of the two young office workers who used carbon tetrachloride to degrease the gearing of their car. Here is another case: Toward the end of the fighting in Korea a large airplane carrying troops from Japan landed at a West Coast airport. The plane was badly needed so a crew was rushed to clean it, inside and out. The men working inside were given buckets of carbon tetrachloride, with a little water floating on the top, and were set to cleaning with swabs and mops. No ventilation was pro vided. Two of the men were overcome and died within a few hours. Another hazard is added to that of the vapor if carbon tetrachloride is used in the vicinity of naked flames or very hot metal. A rather unusual situa tion invoked this hazard. The glassblower's shop in a large research center was supplied with oxygen piped in from tanks outside the shop. Whenever oxygen is used, great care must be taken to avoid grease on any part of the tank, valves, or pipes from the tank. The safety department decided to degrease the oxygen pipeline to the glassblower's shop and did so, using carbon tetrachloride. When the glassblower used the oxygen supply after the de greasing, he and his assistants were made very sick by phosgene produced in the flame of his torch. Nobody had thought to thoroughly purge the oxygen line of carbon tetrachloride vapor. Summary Chemical accidents hurt people. Careful, intelligent handling of chemicals will prevent accidents. Proper ventilation and protection of workers by clothing or individual breathing equipment will prevent chemicals liberated accidentally from coming into contact with the body of workers or from their breathing gases, vapors, mists, or dusts. If, in spite of such protection, chemicals do settle on exposed skin, immediate removal with the use of plenty of water will call a halt 278 Safety and Accident Prevention in Chemical Operations to direct injury of the skin or to absorption through the skin with possible general illness. More than two-thirds of chemical injuries in industry are injuries of the skin. Water is the best "antidote" for a majority of industrial chemical injuries. 17 Toxicity Vs. Hazard H. H. Fawcett "How toxic--how hazardous?" These two related thoughts are fre quently combined into one compound question, yet in their practical aspects they may require entirely different answers. This discussion will point out some of the factors which must be considered in evalua tion of the true hazard of a substance suspected of being toxic. The word toxic has been loosely applied to many different effects, when actually it should be related to general, systematic effects of a substance in living animals or humans. Almost every substance will produce injurious effects in a living body to some degree (even "safe" substances like salt, baking soda, and sugar can produce serious illness when taken in excess). The key questions are: how much is needed to produce a toxic effect, and, of equal importance, how likely is this amount of material to enter the body where it can actually produce this effect? Substances differ widely in their relative toxicity, in their ability to enter the body, and in the effects they produce. Toxicity, for this discussion, is defined as too much of a substance for the body to tolerate without injury. Toxicity is not a specific physical constant determined by standardized devices, such as used to determine specific gravity or melting point. Not a property of the substance itself, toxicity defines the degree to which the substance affects living cells. Figure 17.1 represents attempts to explain this concept. However, living cells do not lend themselves to absolute standardiza tion. The University of Texas recently observed wide variations 279 ETC 03308 280 Safety and Accident Prevention in Chemical Operations even in "uniform" white rats bred and selected for experimental jn vestigations--one rat drank 15 times more alcohol than another, atuj another traveled 6 miles while his less active brother was moving 150 ft. If rats bred and carefully selected for uniformity are such non conformists, consider how much more humans differ from each other and from the standard curve. The problem of individual variation has been demonstrated many times in the field of toxicology, as well as in other phases of life. The time-honored expression, "One man's meat is another man's poison" aptly sums up man's experience in this respect. Just as there is no "standard animal," there is no "standard man"--animals and humans are subject to wide varia tions. Toxicity cannot be measured at all until a definite recognized change has occurred in an animal or in a human. These changes mav be very small and easily overlooked; such changes as impaired judg ment and delayed reaction time may be involved at levels too low for the production of body damage. Animals may react in a much different way than humans. Mules, for example, do not develop silicosis even when working beside miners who develop the disease. Crystalline penicillin G is essentially non toxic in animals, with the exception of guinea pigs. Guinea pigs are peculiarly sensitive to penicillin (and to certain other antibiotics) and doses as small as 7000 units/kg may produce serious effects and finally death within a few days. Doses as high as 9,800,000 units, or 5.93 g/kg were tolerated in mice, while humans can tolerate tre mendous doses (even daily doses as high as 86,000,000 units for a 28-day period), except for those who are allergic and then even small doses produce severe, and occasionally fatal shock. Animals may survive a relatively large or acute dose but die from smaller doses over a longer period; the rodenticide warfarin (3-a-acetonyl-benzyl)4 hydroxycoumarin is an example of such a substance. To illustrate how much information we need to complete the evalua tion of a potential hazard (not merely citing toxicity alone), we should ask fundamental questions: 17.1. WHAT EXACTLY IS THE CHEMICAL COMPOSITION OF THE SUBSTANCE AS ACTUALLY USED? It is futile to attempt any evaluation of hazard without specific and definite information on composition. To say a solvent mixture "con tains mineral spirits" is to present completely inadequate information, since mineral spirits vary widely in composition, and also the per- Toxicity Fs. Hazard 281 centage of mineral spirits in the mixture may be very small or quite high. Other constituents in the mixture may be far more hazardous, such as benzene or carbon tetrachloride. If a proprietary-brand solvent or mixture is involved, the maker will usually reveal the complete formula on a confidential basis to a responsible person for the user, if given assurance that the information will not be used against his best interests or passed on to anyone else. If the supplier will not cooperate, two alternatives are always suggested: (1) analyze the substance yourself; (2) locate a more cooperative supplier. Usually the supplier will cooperate if he realizes his business depends on cooperation, and this approach is usually faster, more accurate, and more economical for all concerned than analysis. With the new techniques, such as chromatography and infra red spectrographv, however, analyses are much easier to obtain than previously, and nothing should deter us from obtaining the complete analysis if we are suspicious a hazard may be involved. 17.2. WHAT ABOUT TOXICITY IN ANIMALS? Once we have learned what is involved chemically, we can turn to the literature in the hope that our substance has been investigated and published. At this point extreme care must be exercised, since toxicity values are by no means absolute; they can be considered only as yardsticks of activity. Spector1 lists five conditions that influence the toxicity of any given compound. dose. Generally the larger the dose, the more rapid the action. rate of absorption. The faster the rate of absorption, the quicker the action of the drug. route of administration. Toxicity is greatest by the route that carries the toxic substance to the bloodstream most rapidly. In decreasing order of speed, routes for most substances are: intravenous (into a vein) inhalation (breathing) intraperitoneal (into the abdominal cavity) intramuscular (into a muscle) subcutaneous (under the skin) oral (by mouth) cutaneous (on the skin) site of injection. With subcutaneous injections, toxicity may be affected by the density of the subcutaneous tissue. In intravenous 282 Safety and Accident Prevention in Chemical Operations administration, the rate of injection, or the amount of toxic material injected per minute, will considerably influence the value of the toxic dose. other influences. Disease, environmental temperature, habit and tolerance, idiosyncrasy, diet, season of the year--all may affect toxicity The toxicity of chemicals will also vary with the species of animals used and sometimes with different strains of the same species. Within the same strain, the toxicity may differ with age, weight, sex, and the general conditions of the animals. The time to produce death or the period of time for which fatalities are counted, may also be a factor. There are several units in which the toxicity dose is expressed. The most frequently used are: LD or lethal dose (the amount which kills an animal), the MLD or minimum lethal dose (the smallest of several doses which kills one of a group of test animals), LD50 0r lethal dose for 50% (the amount which kills 50% of a group of test animals, usually 10 or more), and LD100 or lethal dose for 100% (the amount which kills 100% of a group of test animals, usually 10 or more). Sometimes D is replaced by C in the above symbols and the word "concentration" used instead of dose, as LC = lethal concentration, when referring to vapor concentration in air. The usual form in which lethal doses of solids and liquids are expressed is in milligrams of substance per kilogram of body weight of the animal, or abbreviated as mg/kg or g/kilo. Since a 150-lb adult weighs about 70 kilograms, it might be expected that animal data could be translated into human data by multiplying the mg/kg dose by 70. This practice is filled with pitfalls, and it should be used as a "degree of magnitude" rough calculation. For reasons already mentioned, plus the important fact that there is no laboratory animal (except possibly the higher apes) which reacts like man, extreme care should be used in applying animal data to humans. 17.3. WHAT ABOUT HUMAN EXPOSURES? The real value and ultimate test of toxicity data, of course, is what actually happens to humans. -Here we see even clearer that toxicity is not a simple matter. Some substances highly toxic to young children (up to age 4 years) are relatively nontoxic to adults, because no adult would eat or drink them except by the highly unusual accident or a suicide measure. Two common materials which cause serious poisonings in children are kerosene and aspirin. By chewing on cribs, -windowsills, and toys ETC 03312 284 Safety and Accident Prevention in Chemical Operations painted with lead-containing paint, children may be poisoned with lead. A highly unusual case, reported a few years ago, developed from a teen-age boy chewing on a lead "sinker" which he used in fishing. Medications, especially aspirin and sleeping pills, are often eaten by young toddlers, occasionally with fatal results. The recent establishment of over 500 poison-control centers in the United States and Canada to advise the physician on an emergency basis the comp0. sition and recommended treatment in poisoning cases may help to make the public more aware of accidental poisoning cases, and hence to prevent accidents involving drugs and other chemicals. Another practical problem encountered in evaluation of hazards is that much necessary data can only be obtained by experience. For example, some substances such as the isocyanates have a very low level of true toxicity, but in extremely small concentrations in air they can cause bronchial irritation from sensitization. The irritating aspects of materials are not shown by animals. A mixture of diphenyl and diphenyl ether is a widely used heat-transfer agent, having a very low toxicity rating, but when accidentally sprayed in a man's face it causes serious, almost fatal, respiratory effects due to irritation. Hydrogen sulfide is an example of a gas which in higher concentrations soon paralyzes the nose so the odor cannot be used as even a rough estimate of concentration for this highly dangerous substance. Irri tation varies with people--some people frankly say they like the odor of pyridine and of mercaptan while others are irritated, annoyed, and affected by the same concentration. Boric acid is an example of a chemical which has been used in the treatment of burns for many decades, but whose toxicity has been recently recognized as too high to justify its use in this application.2 Beyond the gross dosage problems, as reflected in poisonings, there is the practical day-to-day exposures encountered in industry. This is the real practical test of toxicity--what does the substance, either alone or in combination with other substances, do when breathed or absorbed in other ways at rates which will probably vary over wide limits during the day, for several hours a day for a certain period of time. To furnish a guide to the control of such exposures, Professor Warren Cook tabulated and published in 1945 recommendations of maximum concentrations permissible for many common substances. Since 1947, the American Conference of Governmental Industrial Hygienists has sponsored a committee which publishes an annual revision to the threshold limit values, formerly referred to as MAC or maximum acceptable concentration values. Nearly 300 substances are currently listed by the committee.3 This list is not an official * Toxicity Vs. Hazard 285 "standard," but many states have adopted it as the working limits for their labor or health codes, and it has been referred to in the WalshHealy Health and Safety Act, which applies to federal contractors. Before using this list, however, it is wise to carefully read the preamble, in order to understand exactly what the list is as well as what it is not. These values are not a measure of relative hazard. The early values were established largely on the basis of safe level to prevent damage from chronic exposures. As more data became available based on actual experience, many values were lowered to reflect irritation and other transitory or acute changes. Recently, sub acute levels have been introduced to reflect comfort levels. In addition to the threshold limit values, when evaluating hazards, we must con sider the vapor pressure of the material which will determine the potential of attaining the MAC under given conditions of use, as well as other important factors which can relate to actual conditions of use. Another source of information which is often helpful in evaluating the hazards of a substance is the manufacturer--a person who is truly interested in seeing that the substance is used without adverse effects. Both in published data sheets and in answers to specific inquiry by telephone or mail, the manufacturer will give practical recommenda tions as to the precautions he believes necessary. The more specific the inquiry, the more helpful will be the reply. Regardless of the quantity (a few grams may represent more hazard than a million gallons) the fundamentals are the same, and the manufacturer will usually supply the information if requested. Another guide to safety information is open literature. Much is available for those who seek it. A two-part article in Industrial and Engineering Chemistry, points out several excellent sources of safety information not widely used.* The Manufacturing Chemists' Associa tion5 and the National Safety Council6 both publish detailed infor mation on many chemicals--information which helps in evaluating potential hazards. Hygienic Guides, published by the American In dustrial Hygiene Association, now cover nearly 100 substances in considerable detail.7 A reference librarian frequently can suggest many sources of specific information either in permanent volumes or in periodicals. 17.4. WHAT CLASS OF TOXICITY INCLUDES THE SUBSTANCE? Ultimately we must decide on the degree of hazard presented by a substance. Classification of hazards goes far beyond toxicity, as 286 Safety and Accident Prevention in Chemical Operations illustrated by the excellent work of a National Fire Protection Association Committee chaired by James J. Duggan, which classified and labeled substances, especially larger amounts in barrels or storage tanks, for emergency control purposes. The N.F.P.A. Standard 704 M which resulted from this work, includes toxicity (hazard to life)' flammability (fire hazard), explosion hazard (probability of explosion)' and chemical reactivity (possible reactions with other nearby sub stances, if spilled or ruptured), which, combined with other essential emergency would be most valuable to emergency personnel.8 Hodge and Sterner tabulate toxicity into six classes:9 TABLE 17.1. Toxicity Classes Toxicity Rating i 2 3 4 0 6 Common Used Term LD$o Single Oral Extremely toxic Highly toxic Moderately toxic Slightly toxic Practically nontoxic Relatively harmless 1 mg/'kg or less 1-50 mg/'kg 50-500 mg/kg 0.5-5 g/kg 5-15 g/kg 15 g/kg and more Inhalation 4 hr Vapor Exposure Mortality 216-4/6 Rats < 10 ppm 10-100 LD 1,0 Skin Rabbits 5 mg/kg or less 5-43 mg/kg 100-1000 44-340 mg/kg 1000-10,000 0.35-2.81 g/kg 10,000-100,000 2.82-22.59 g/kg Probable Lethal Doee for.Van A taste, 1 gran 1 teaspoon, 4 cc 1 ounce, 30 gm 1 pint, 250 g 1 quart >100,000 22.6 g kg or more >1 quart Another interesting and useful tabulation is the relative eye damage produced by 60 chemicals, classified into ten ratings.10 17.5. HOW LIKELY AM I TO RECEIVE A HARMFUL CONCENTRATION? The old cliche of the sea states, "Not all the waters of the seven seas can sink a boat until it gets inside the boat." Toxicity is much the same. A chemical in a bottle, in a tank, or in a boat is harmless as long as it is fully contained. In evaluating the hazard, therefore, the basic consideration should be based on how much of the substance will be in the air, or where it will be so it may be eaten, or absorbed through the skin or the eyes. Once this is established, we can add the toxicity data, expressed as dose, or irritation, or maximum allowable concentration, or threshold limit value, and find some measure for the actual hazard. ETC 03315 Toxicity Vs. Hazard 287 About ten years ago, a relatively new chlorinated hydrocarbon was introduced on the market, and widely promoted as a substitute for other solvents such as carbon tetrachloride. The new substance had many characteristics and properties of carbon tetrachloride--its vapor pressure, cleaning ability, and drying without residue were similar to carbon tetrachloride. Extensive animal exposure has established a firm basis for assigning this substance a threshold limit value of 500 parts per million in contrast to 10 parts per million for carbon tetra chloride. This limit has since been lowered to 350 parts per million-- still a very wide margin over carbon tetrachloride. Although we agree this solvent is much safer than carbon tetrachloride, and we continue to recommend it for many applications, we must point out that at least three fatalities have resulted from its use. Such solvent fatalities usually involve a careless use in a confined unventilated space, while working alone. For example, a technician was believed to have been working at the bottom of the outer shell of a vacuum furnace, 38 in. in diameter by 49 in. deep, cleaning oil and grease from the interior surfaces with steel wool and rags saturated with the solvent. The tank was located in an open room and had one 15-in. and three 6-in. diameter ports 28 in. from the bottom. The solvent was being used from an open coffee can, and approximately a quart had been used when the technician was found dead, about 50 min after the super visor had last checked the work. Such cases do not indicate the solvent is not relatively safe--it simply underscores again that any solvent must be used with respect. Use of any solvent in a confined space without adequate ventilation, especially by a man working alone or with only nominal, occasional supervision, is extremely unwise. In this connection, an advertisement used by some distributors that a solvent is "20 times safer than carbon tetrachloride" is highly mis leading, and represents a use of threshold limit values in an entirely different manner than intended. 17.6. WHAT IS OUR EMOTIONAL APPROACH TO THE SUBSTANCE? A few substances have come to be associated with high hazard in the public mind. If we consider "poisons" as synonymous with "haz ards," we probably think of cyanide, lead, silica, arsenic, and carbon monoxide. Snake venom, curare, benzene, and carbon tetrachloride might be included on second thought. The strange enigma of beryllium and beryllium compounds and the surprising reluctance of intelligent persons to accept the facts about the substances, indicate that publish- 288 Safety and Accident Prevention in Chemical Operations ing data alone does not insure that everyone will be informed or will believe. Some of the older tonnage chemicals, such as aniline, nitro benzene, and hydrogen sulfide, have not yet been widely recognized as hazardous, and there are many substances about which we know so little that it is impossible to even guess how safe or how hazardous they are in the intended applications. Recently, a university reported the death of three students who were working with several bicycloheptadiene derivatives, previously not considered hazardous. Animal in vestigations are underway to elucidate the hazard.11 Extreme fear and anxiety about hazards may actually create acci dent situations, just as may apathy and ignorance. Personnel may be so fearful that they will become nervous and supersensitive--perhaps even allergic. The reverse condition, lack of adequate and proper respect for a hazard, may also contribute to accidents by encouraging carelessness and lack of protective measures. Exactly how to pre sent the degree of hazard to personnel in their specific use of the toxic or corrosive material, so they will actually react 'with respect and confidence but not fear, is one of the challenges of supervision. In addition, the emotional state of the man, his emotional stability and adequate adjustment to his job, his boss, his company, and his home life, all may be far more important in evaluating actual on-the-job hazards than toxicity data alone. In all cases, it must be the man, not the chemical, which is the center of our attention. Another factor which may minimize the hazard of a substance is irritation ability. If a gas or vapor affects the upper respiratory tract sufficiently to cause sneezing, coughing, or extreme discomfort to the eyes or throat, the normal reaction is one of escape or repulsion, which tends to decrease the exposure. On the other hand, if the substance is not sufficiently irritating or objectionable, the practical danger is much greater, since the warning will be less or inadequate. Summary All chemicals, per se, are toxic (common usage meaning the ability of excessive amounts to produce damage to life). Toxicity refers to the effect on living cells (usually animals or humans). Toxicity data must be carefully screened and examined before ex trapolating into human experience. Chemicals, even "extremely toxic," may or may not be hazardous, depending on their use. Until they reach and produce effects inside the body, toxic substances are not harmful. ETC 03317 Toxicity Vs. Hazard 289 Our procedure should be to properly evaluate the hazard presented under the conditions of use, and then take precautionary measures to insure safety as needed by the circumstances and conditions developed. REFERENCES 1. Spector, Handbook o/ Toxicology, Vol. I, Acute Toxicities, W. B. Saunders Co., 1956. 2. JAMA, 186 (December 28, 1963), p. 1167. 3. Threshold Limit Values for 1064, available from American Conference of Gov ernment Industrial Hygienists, 1014 Broadway. Cincinnati, Ohio. 4. H. H. Fawcett, "Who Knows What About Chemical Safety," Ind. and Eng. Chem., Part I, Vol. 52, No. 6 (June, 1960), pp. 85A-88A; Part II. Vol. 52, No. 8 (August, 1960). pp. 75A to 76A. See Appendix. 5. Publications of Manufacturing Chemists' Asso., 1825 Conn. Are., N.W., "Wash ington. D. C. 6. Publications of National Safety Council, 425 N. Michigan Ave., Chicago, 111. 7. Publications of American Industrial Hygiene Association, 14125 Prevost, Detroit, Michigan. 8. NFPA No. 704M--1964, "Identification of the Fire Hazards of Materials," Vol. 8, National Fire Codes, 1964-1965. Also available as pamphlet for $0.50 from National Fire Protection Association, 60 Battervmarch St., Boston, Mass. See also Appendix I. 9. H. C. Hodge and J. H. Sterner, "Tabulation of Toxicity Classes," American Industrial Hygiene Association Quarterly, Vol. 10, No. 4, page 93, Dec. 1949. 10. R. S. McLaughlin, "Chemical Burns of the Human Cornea," American Journal of Ophthalmology, Vol. 29, No. 11, pp. 1355-1362, Nov. 1946; C. P. Carpenter and H. F. Smyth, Jr., "Chemical Burns of the Rabbit Cornea," Vol. 29, No. 11, pp. 1363-1372, Nov. 1946; see also W. M. Grant, Toxicology of the Eye, Charles C Thomas, Springfield, 111., 1962. 11. S. Winstein, Communications to the Editor, Bicycloheptadiene Dibromides, Journal oj the American Chemical Society, Vol. 83, pp. 1516-1517, March 20, 1961. !i 18 Safe Experimentation H. H. Fawcett 1 Before developing the subject of safe experimentation, an explanation of the terms safe and experimentation, especially when these two are used together, is in order. One definition of safe is "free from or not liable to danger of any kind." For our purposes, danger may be expanded to mean (1) phys ical hazards, such as flying glass, electrical shock, pressure, and vacuum; (2) chemical hazards, such as skin corrosion, dermatitis, and poisoning from fumes (inhalation), ingestion (eating), and skin ab sorption; and (3) fire and explosion hazards, such as undesired ignition of flammable gases, liquids or solids, or unexpected evolution of pres sure-producing gases. With these thoughts in mind, to use safe as an adjective modifying experimentation, which is "an act or operation designed to discover some unknown truth, principle, or effect," implies that we are able to prevent all dangerous situations which might arise in research. We concede that we probably will never be able to foresee all the boobytraps which may arise in scientific work, before we can completely understand what motivates a man to unsafe acts resulting in accidents. However, just as we can change the velocity of a reaction by modified conditions or by a catalyst, so can we decrease the dangers in experi mentation by the catalysis of safety. To illustrate how we might apply safety knowledge to research, let us imagine we are interested in the reaction: X + Y-*Z. 290 ETC 03319 Safe Experimentation 291 To make our example realistic, let us assume X is a gas at room temperature and atmospheric pressure; that Y is a liquid at room tem perature; and that our product, Z, is believed a solid by analogy of its assumed molecular structure. We have never reacted X, the gas, with F, the liquid, and can find nothing in the literature concerning the reaction. .The problem then is to prepare a set-up in which the reaction may be studied without injury to personnel. Since we have assumed that the two reactants are known chemicals, some of the physical and chemical properties should be available from the maker or supplier. We should not neglect to request safety data as well. In the case of X, the gas, we might inquire: 1. Is it flammable with air; if so, within what range? 2. If flammable, what is the auto-ignition point? 3. If nonflammable, does it undergo decomposition into flammable or toxic products? 4. What is the vapor density compared to air? 5. What are the hazards of inhaling the gas? 6. What parts of the body are affected by inhalation? 7. What respiratory protection is required, such as a chemical car tridge respirator, canister-type mask, or self-contained air or oxy gen breathing apparatus? 8. What first-aid treatments (both on the spot and by the physician or nurse) are recommended? 9. Can the gas be detected by odor, and, if so, at what concentration? 10. What analytical or instrumentation method is available for deter mining injurious concentrations of the gas in air? 11. WThat is the maximum allowable concentration for continual 8-hr exposure to the gas in air? From a practical standpoint, it will usually suffice at the research stage to know the answers to the first eight items given above, questions nine through eleven are usually important only when pilot plant or experimental scale plant operations are reached. With the answers to the first eight questions, we can decide how elaborate our care in handling should be, our care in transferring, and our care in reacting the gas, X. If it develops that the gas is relatively unreactive, such as nitrogen, the inert gases, sulfur hexafluoride, car bon dioxide, or the simple fluorocarbons, we need relatively little ventilation, shielding, protection against fires or explosions, and rela tively simple specific medical procedures. However, if a gas such as hydrogen cyanide, fluorine, chlorine, diazomethane, hydrogen sulfide, 292 Safety and Accident Prevention in Chemical Operation hydrogen selenide, or arsine is involved, extreme care must be taken. All these gases are severe health hazards, and most are flammable or explosive under some conditions. Hence, it is imperative that the gas be handled at all times in an environment where ventilation will be adequate to remove escaping gas and to dilute it promptly below the levels which are toxic or flammable. Medical control should also be established. First-aid measures for on-the-scene and clinical treatment by the physician or nurse should be considered before actual work is begun. The question of periodic physical checks should be explored. Frequently, in this connection, the investigator, or some other inter ested party, can assist the medical personnel by calling attention to the problem and by reviewing the known and unknown aspects of its effects upon humans, to the extent such knowledge is available. Turning now to our other raw material, Y, the liquid, an attempt should be made to assemble as much of its safety data as are avail able. Several important items are: 1. Purity, such as nature and amount of impurities; 2. Flash point and fire point, so relative degree of fire hazard can be established; 3. Boiling point at atmospheric pressure and stability of the liquid toward heating and distillating; 4. Freezing point; 5. Stability on storage, including possible effects of heat, light, water, and metals, by formation of dangerous by-products, such as per oxides in ethers, and on spontaneous heating as in drying oils; 6. Vapor pressure at room temperature and elevated temperatures; 7. Flammable range of the vapors in air; 8. Auto-ignition point of the vapors; 9. Vapor density, which determines ease of ventilating; 10. Effects of inhalation of the vapors, in both acute and chronic ex posures ; 11. Effect of both liquid and vapor exposures on skin and eyes; 12. Effect of ingestion (accidental intake). Although all these items are important in the final control, it is doubtful whether they will all be readily available for the liquid under question. An active search should be continued, however, even to the extent of experiments to determine the effect of the liquid and its vapor on laboratory animals if the human exposures to the liquid or its vapor are to continue for long periods. l-iii: With the available data on reactant, Y, we can plan the degree of safe handling needed. If the liquid is relatively free of serious fire ETC 03321 Safe Experimentation 293 and health hazards, such as the higher alcohols, higher esters, and higher ketones, the normal care with which a conscientious experi menter treats all materials should suffice. If, however, serious health or fire hazards are present, as with ether, lower alcohols, lower aldehydes, ketones, nitro compounds, and many aromatic compounds, the handling procedures should include protection of personnel from excessive exposures to either vapor or liquid. This, of course, includes the necessity for closed-system work insofar as possible, as well as personal protective equipment such as gloves, goggles, face mask, apron, and respiratory protection. As experience is gained, the procedures should be changed to further increase safety as the necessity arises. For example, adequate protection may have been taken against fire and explosions, but experience may show that sufficient vapor is being released to the laboratory air to make personnel develop headaches, occasional dizziness, and upset stomach. Obviously, the set-up should be reviewed with the objective of decreasing the air-borne exposure in this case. The actual experimental work is now begun, with the degree of care suggested by the study of Ar and Y and their probable interaction. Obviously, if the search for data on X and Y has yielded only par tially complete information, additional precautions should be included to safeguard against unknown hazards. At first, only small amounts of X and Y should be brought into contact, such as gram or sub-gram quantities, and the results observed carefully. Changes in temperature, in color, in viscosity, or in phys ical state should be noted. By varying concentrations, time, tempera ture, and pressure, the optimum conditions for the reaction can be established. Safe limits can now be imposed to insure that the reaction will not exceed the specified conditions. When the product, Z, is first isolated, the usual elementary analysis will at least suggest possible structures. We know that certain groups in a molecule create explosive tendencies. Among these "plosophores" are: --ONOo nitrate --NH--NO2 primary nitramine --N--NO2 secondary nitramine R--N02 aliphatic nitro Ar--NO> aromatic nitro Organic salts of the following types: ETC 03322 294 Safety and Accident Prevention in Chemical Operationi Less powerful, but often more sensitive compounds contain these groups: --N3 azide --NO nitroso --N=N--diazo --N=N--S--N=N--diazosulfide --0--0--perioxide =N--X halamines --C=C--acetylides The presence of one or more of these in the molecule should serve as a warning of relative instability. Another safety evaluation is to consider the oxygen balamce, if the molecule has combined oxygen within it. The closer the molecule approaches self-satisfaction by oxidation, the more powerful the explosive. As an example, three nitro groups on an aromatic ring, such as exists in tetryl, TNT, and picric acid, provide a source of readily available oxygen for the rapid burning or explosion of the molecule. It is difficult to establish definitely when exhaustive (and admittedly expensive) investigations should be undertaken to develop the safety data on a new compound. Much depends on the amount of compound available, the forecast for production, and on the end use. If this compound, Z, is an intermediate which some company will use to produce a new end product and the processes are well-engineered, the minimum of such information will usually suffice. On the other hand, if the new compound, Z, is destined for wide use by the public, such as a food, cosmetic, economic poison, or container, extensive studies should be made to establish quantitatively such data as: 1. Impact sensitivity. 2. Stability on storage. 3. Melting point. 4. Acute and chronic dosage by various routes, such as injection into the blood stream, injection into the stomach, skin contact, eye con tact, and dust inhalation. 5. Maximum allowable concentrations or threshold limit values for continuous 8-hr exposures. 6. Fire hazard, both from ease of ignition and from rate of burning. 7. Injurious vapors or gases from burning. 8. First-aid and clinical treatment for exposures. L'sually, a review of these items will be made during the transition from laboratory to pilot plant scale and at least some of this data should be available before plant personnel is involved. From this data should evolve a warning label which will serve to define the outstand ing hazards of the compound and which should be displayed on every Safe Experimentation 295 bottle, drum, or tankcar of the product which leaves the plant. The Manufacturing Chemists' Association has formulated definite rules for warning labels and increasing emphasis is being put on this warning procedure by federal, state and local laws.1 In addition, the Interstate Commerce Commission, Bureau of Explosives, must classify the com pound before it can be accepted for express shipment and the proper warning label must be attached to all shipments.2 The producer must supply the data for this classification. We have briefly discussed the role of "safety data" in research. The more that is known of a compound, including its effects on humans, before it leaves the laboratory or pilot plant, the more complete will be the insurance against unwanted experiences. If we remember that chemicals, like humans, have characteristics which may be either blessings or curses, depending on how they are controlled, tve shall have progressed toward safe experimentation. references 1. Guide to Precautionary Labeling of Hazardous Chemicals, Publication L-l, 6th ed., 1961, Manufacturing Ch^nists' Association, Inc., Washington, D. C. 2. T. C. George, Interstate Commerce Regulations for Transportation of Explo sives and Other Dangerous Articles by Land and Water in Rail Freight Service and by Motor Vehicle (Highway) and Water (Including Specifications for Shipping Containers), Tariff No. 15, 1963, Bureau of Explosives, Association of American Railroads, New York, New York. 19 Testing Reactions and Materials for Safety J. S. Snyder The chemical industry's property damage and business interruption losses in recent years have been high. The National Fire Protection Association, which makes an annual study of all large fire losses, classi fies a large fire as a loss which exceeds $250,000. The N.F.P.A. re ports that in 1961 the chemical industry had eighteen large fires, that killed fourteen persons, injured 314, and cost almost $8,500,000. In 1962, only four chemical industry fires (there were several others) exceeded both the loss of life and property damage of all eighteen in 1961. Each involved an explosion. The estimated property damage and business interruption costs for two of these four explosions were greater than $8,000,000 each. We experienced the worst "large loss" fire experience in 1963 with 488 such fires resulting in over $350,000,000 in damage. A real problem exists, and if the present trend continues, the prob lem will become even more acute. The small, isolated pot-and-kettle installation is a thing of the past. Today industry is installing com plex, automated processes. The reactions usually are fast because of the nature of the reactants, high temperatures, high pressures, and active catalysts. To complicate matters even more, many of the reactants and products are extremely toxic. An intelligent appraisal of the new risks must be made, and presented to management with recommendations for minimizing the probabilities of serious incidents. 296 ETC 03325 Testing Reactions and Materials for Safety 297 Chemists usually admit that in most organic reactions where com pound A and compound B react to form compound C, 3 or 4 tran sitory compounds may be involved during the reaction. Not only the product is obtained, but varying amounts of other unwanted com pounds as well. If the reaction is run every time exactly as the chem ist describes, there will be routine operations, but. how close to or howfar from an unstable situation the reaction may be, usually is not known. Ideally the parameters of safe operations for every step should be known, and procedures and equipment should be designed so that the limits will not be exceeded. Knowledge as to what constitutes a potentially unstable condition, and why some compounds and mixtures behave in an undesired fashion, is relatively meager. Hence, the key to any determined effort to test for stability is the interest and backing of research management who must know it is important to find out how safe a reaction is as well as what is the yield. Most research chemists have not been trained or oriented in this direction. No chemist would consider undertaking a new synthesis without a literature search; a good research chemist makes frequent use of the library. Unfortunately, the amount of safety information published in the chemical journals is very meager. Even standard textbooks on organic chemistry used in universities discuss dangerous reactions in a very routine manner. Hence, it is not difficult to understand why so many research chemists are not safety oriented. Perhaps another rea son is that the consequences are minimal when instability is suddenly encountered in the laboratory. A reaction which could result in an explosion in a plant operation may merely cause one of the ground joints of the laboratory flask to be pushed apart or broken by materials frothing out over the bench. The chemist just does not equate the effect of the rapid gas evolution on a loosely connected glass sys tem to the effect on tight steel equipment, containing large volumes, without the pressure-relieving capacity to take care of such a sudden surge. Occasionally the feeling is expressed that it is an insult to profes sional ethics among chemists to -warn that while a procedure described in the paper was being developed, variations in conditions resulted in misadventure, characterized by loss of reaction product to the ceiling or bench, or where flying glassware caused injuries. The research chemist is best qualified to recognize a potentially hazardous compound or reaction. No scale-up of laboratory to pilot plant or of pilot plant to factory should be permitted without adequate consideration being given to the stability of the compounds and reaction involved. 298 Safety and Accident Prevention in Chemical Operations To undertake such a study, the following steps are suggestedFirst, although little may be located in the classical literature an ever-increasing body of safety literature can be helpful. Some research work has been done, and papers have been written on stability 0{ materials. Second, there are ways to confirm or allay some suspicions with simple tests. The Manufacturing Chemists' Association, in their Chemical Safety Data Sheets,1 and the National Safety Council Chemical Section Data Sheets,2 contain some stability data on a limited number of common materials. The 1962 revision of National Safety Council Data Sheet 486, Chemical Safety References, gives an indication of the data avail able on a fairly large number of compounds. Volume One of Case Histories of Accidents in the Chemical Industry, issued by the Manu facturing Chemists' Association, contains an indexed compilation of nearly 600 accidents, and many of these illustrate the causes and re sults of unexpected instability. The Committee on Chemicals and Ex plosives of the National Fire Protection Association, Subcommittee on Hazardous Chemical Reactions, has published a directory to several hundred reactions which cause unwanted results if not controlled.3 Two of the many National Board of Fire Underwriters Research Re ports are especially interesting, namely, "Nitroparaffins and Their Hazards," and "Fire and Explosion Hazards of Organic Peroxides."4 The United States Bureau of Mines Explosives Research Laboratory has contributed much to the chemical stability literature.5 Much of the Bureau's research has been on explosives and includes several im portant tests for evaluating explosives. These same tests can also be used for evaluating nonexplosives. (See Chapter 29.) One source of information frequently overlooked is the manufac turer. When confronted with a compound of suspicious configuration, it is possible the maker has literature on stability or his research staff has unpublished data he will furnish on request. The Department of Defense has authorized considerable research on test methods for propellants, and these tests have application to commercial problems. One publication that contains information on both common and exotic materials is The Handling and Storage of Liquid Propellants A search through this literature and others cited at the end of the chapter, will assist the chemist in the art of recognition, which is the heart of the matter, even though it may not yield the specific react ants he plans to use. Certain types of compounds, mixtures, and re actions should always be suspected. Many may be familiar because they are difficult to handle, but the reactivity noted in the laboratory ETC 03327 Testing Reactions and Materials for Safety 299 is amplified many fold in the closed pilot plant and factory equipment. An explosion is a sudden release of pressure regardless of the source. For instance, a bursting steam boiler is truly an explosion even though steam is not an explosive. An explosive is any substance that can produce in thousandths or even millionths of a second, high-pressure gas capable of destroying the surroundings. A detonation is the process in which an explosive undergoes chemical decomposition or oxidation--reduction, primarily within a high-pressure zone or shock wave that travels at greater than sonic velocity through the unreacted material. In other words, a true detonation is capable of almost instantaneous self-propagation once the reaction or decomposition is initiated.6'7 The reactive chemicals to be considered are not explosives even though they may be capable of self-reaction. As compared to ex plosives they react very slowly and seldom produce shock waves of any significance. Usually the reaction can be controlled after initiating it, by cutting off feed rates, or by lowering temperatures or pressures. With an explosive, this is impossible. Steele and Duggan, in their paper "Safe Handling of Reactive Chem icals,"6 characterize a reactive chemical as a material which will vig orously polymerize, decompose, condense, or otherwise react with itself in the pure state, or in the presence of a catalytic amount of some other material, or which will react violently with water. Classes of com pounds which react with themselves include those containing a vinyl linkage, such as vinyl chloride, acrylates, and styrenes. Some of these require only high temperatures to catalyze polymerization. Others polymerize in the presence of light, peroxides, caustics, and strong acids. Most of the monomers have to be inhibited chemically or at least refrigerated to prevent polymerization. Another group involves the carbonyl radical contained in materials such as butyraldehyde and acetvldehyde. These can condense with extreme vigor in the presence of bases and sometimes strong acids. Certain conjugated unsaturated compounds, such as butadiene, acro lein, and acrylonitrile can polymerize violently in the presence of suit able catalysts or when heated. Epoxy compounds are also self react ants. Ethylene oxide is the smallest and most reactive member of this group, and is capable of violent decomposition. Strong oxidizers such as chlorine dioxide, chlorates, perchlorates, permanganates, peroxides, and chromic acid are all capable of uncon trolled reactions. Compounds of this type are capable of the instability which causes many chemical-plant and laboratory explosions.B- 10 It is essential that the chemist determine the parameters of safety both for 300 Safety and Accident Prevention in Chemical Operations these compounds and for any reaction system that contains these com pounds. The chemist should deliberately determine at what tem perature the reaction accelerates dangerously, which common com pounds can inadvertently or by design catalyze the reaction, and at what concentrations and temperatures this becomes difficult to control Compounds that are reactive with water are included in this study because the results of this mixing can be violent and destructive Among compounds requiring extreme care in this respect are sodium metal, aluminum alkyls, chlorosulfonic acid, phosphorous trichloride and calcium carbide, as well as the concentrated mineral acids, includ ing sulfuric and nitric acid and their mixtures. Acetylene and acetylenic compounds are notoriously unstable. Metal acetylides are sensitive to heat, shock, and abrasion, and some can be classed as explosives. Nitrogen-containing compounds fall into a class by themselves, and they can be very confusing. Nitrogen gas is quite inert, and it is usually added to a reaction mixture to minimize the possibility of an explosion. Gaseous ammonia, although it will form a flammable mix ture in air, is not usually considered an unstable compound. The am monium ion, hovrever, increases the sensitivity and reactivity of some compounds. For example, compare the stability of ammonium nitrate with sodium nitrate. Amines are not reactive in the above context. Trimethylamine is a prime example, although it makes up for its apparent innocence with an obnoxious odor. However, the fact that nitrogen is present in the compound does require a certain amount of caution, because when it comes into contact with strong oxidizers, vigorous and even explosive exotherms are experienced. In contact with mercury, explosive fulmi nates are formed and reactions with hydrochloric acid will produce diazo compounds with distinct thermal instabilities. Hydrazine, which is just two amine radicals with a nitrogen--nitrogen bond, is an ex tremely reactive compound and a propellant. Its vapors are shock sensitive and can explode with extreme violence. The commercial diazo compounds with the --N=N-- linkage are not generally shock sensitive, usually because the molecule is quite large, but practically all will decompose exothermically and even explosively on heating, and they are sensitized by a variety of compounds. All the hydrazines and hydrazones are reactive and can form explosive com pounds, but unless intimate knowledge of the chemistry involved is applied, predictions are risky. For example, hexamethylene tetramine is used in making explosives, but it is not particularly sensitive by itself although it contains a high nitrogen percentage. Testing Reactions and Materials for Safety 301 N=N bonded compounds are not explosives, but if another nitrogen -+ + is added to form an azide, N--N= or N=N=N, the molecule becomes sensitive. The azides are thermally unstable, and all explode when heated. Most are shock sensitive even at room temperature. The oximes C=NOH are reactive but not really sensitive com pounds, and neither are the nitriles with the C=N (cyanide) linkage. The carbon--nitrogen bond is much more stable than the nitrogen- nitrogen bond. The isocyanates --N=C=0 are not sensitive. The nitrogen--oxygen bond is an interesting linkage. Nitro com pounds with the --0--N=0 linkage are usually strong oxidizers and can be thermally unstable at relatively low temperatures. Compounds with more than one nitro group form our common explosives; the more nitro groups the more sensitive the compound. But if the molecule is small enough even one nitro group can be enough to make the compound shock sensitive. For example, a few years ago, two tank cars contain ing nitromethane exploded. This substance was manufactured for many years and shipped in tank-car quantities, until one day the right conditions occurred and the contents detonated. There are other mate rials in the same category that may not yet be identified as such. Nitroethane has not exhibited the sensitivity of nitromethane. How ever, by test we have determined that if as little as hJc by weight of n-butylamine is added to nitroethane, the mixture is as shock sensitive as some explosives. The ability to sensitize relatively stable compounds is not easily pre dicted. Not enough is known about the chemistry involved to be accurate. By sensitization is meant not only the increase in shock or friction sensitivity, but the ability of one material to catalytically de crease the thermal stability of a compound or mixture, either by low ering the decomposition temperature or by causing a rapid oxidation. Naturally this includes compounds which are reactive, and, therefore, capable of being affected more easily and by a surprisingly wide variety of materials. Some of the references contain lists of incompatible compounds, such as the Department of Commerce Research Report, "Explosives, Propellants and Pyrotechnic Safety Covering Laboratory, Pilot Plant and Production Operations."11 Some of the hazardous mixtures include ammonia with chlorine, mercury, or calcium hypochlorite; chlorine with acetylene, petroleum gases and finely divided metals, cyanides, and concentrated formaldehyde, and hydrazine and ferric oxide. An unusual highly exothermic reaction with relatively common materials may be of interest. The contents of a receiver tank con- 302 Safety and Accident Prevention in Chemical Operations taining a chloroform-methanol mixture were being transferred to a drum that had originally contained tetrahydrofuran. The operator filling the drum heard a hissing noise and warned nearby workers to leave the building. While the building was being evacuated the drum exploded causing relatively minor building damage. A few windows were broken, a door was blown off its hinges, but no injuries resulted. Investigation revealed that sodium hydroxide was being used as a stabilizer for tetrahydrofuran and probably some caustic remained in the drum. Laboratory studies proved that when chloroform is added to methanolic sodium hydroxide, a vigorous reaction occurs. When 1 g of sodium hydroxide was added to a mixture of 1 ml of methanol and 1 ml of chloroform, an exothermic reaction took place which, after 5 min, became vigorous enough to bubble out of a 6-in. test tube. Aqueous sodium hydroxide also reacted in methanol-chloroform mixtures in the same way. Chloroform-tetrahydrofuran-sodium hydroxide mixtures did not react, thereby indicating that tetrahydro furan was not responsible for the incident. It should be noted that methanol plays the role of solubilizer by increasing the contact between base and chloroform. Other solvents which dissolve sodium hydroxide and are miscible with chloroform can be substituted as the solubilizer. The reaction products may be different, but the net effect will be the same. Potassium hydroxide and other alkalies may replace sodium hydroxide as a reactant in the solubilizer-chloroform mixture. As a supplement to the recognition of reactive chemicals, the chemist should be alerted to certain types of reactions which utilize these chemicals. All nitrations should be viewed critically. Many, if not most, of these reactions display thermal instability at certain temperatures and pressures especially if there is an excess of nitric acid. In many of the mixtures tested an excess of nitric acid will also cause the mixture to be shock sensitive. Oxidation-reduction reactions using peroxides, chlorine, per acids, or per salts are notorious for explosions because of thermal instability or shock sensitivity. Included in this group would be the WolffKishner reductions employing hydrazo compounds and even metal hydride or pure hydrogen reactions. Condensations such as Friedel-Crafts, Claisen, and Cannizzaro types; polymerizations; Reppe chemistry reactions utilizing acetylenic compounds; and Grignards are examples. There are many more re actions and compounds which fit into these categories. ETC 03331 Testing Reactions and Materials for Safety 303 Simple tests can be run that are adequate for continuing laboratory work. There are more elaborate tests which should be used if the work is carried further into pilot plant or factory size equipment, or if the first test reveals a dangerous condition.12 The initial testing for thermal stability is based on the fact that practically all hazardous reactions involve rapid exotherms and that the rates of all reactions increase with temperature. Experts have determined that even for the majority of explosives, initiation is ther mal in origin. With very little experience this test is remarkably reproducible, and it will reveal exotherms in oxidation and poly merization reactions involving reactants of low volatility. Hundreds of determinations may have been made without incident, but we should still insist on a rapid pre-test to safeguard the tester. This pre-test involves dropping a small quantity, less than one-tenth of a gram, on a hot plate at above 300C. If a sound is heard like a pop, bang, snap, or crackle, the barricading is brought into the scene. If the sample decomposes, chars quietly, or sizzles first because of the evap oration of liquids, the test is continued. It is absolutely essential that the compound or mixture decompose for this pre-test to be valid. The simple thermal stability test makes use of a standard meltingpoint apparatus, as illustrated in Fig. 19.1.13 The heating coil in the FIG. 19.1. Thermal stability test apparatus. 304 Safety and Accident Prevention in Chemical Operationt silicone oil-filled cyclic bath is regulated by a variable transformer The material to be tested, about 1 g of active ingredient, is added to a 15-ml pvrex, tapered bottom, centrifuge tube. A fine wire thermo couple with a melting-point tube as a corrosion shield is inserted to a point near the bottom of the sample. The centrifuge tube and a second thermocouple are inserted through a cork into the melting-point appa ratus. The thermocouples should be at the same level. The test is run in a hood with the hood door closed. The variable transformer and the temperature indicator are located outside the hood. The stirrer is turned on and heat is applied. The rate of heating is kept at 10 to 15F/min. The oil temperature is not permitted to exceed the sample temperature by more than 25F, preferably not more than 15F. If it does, the rate of heating is slowed. For every 25F increase in the temperature of the sample, the time, sample and oil temperatures, and transformer settings are recorded. Any change in the state of the sample is also recorded, as any evolution of gas, charring, melting, boiling, or fuming. Particular note is paid to any rise in sample temperature above or approaching the oil temperature. If this occurs, readings are taken more rapidly. If the sample temperature even equals the oil tempera ture, the result of the test is considered to be positive. If an exotherm TABLE 19.1. Temperature Readings--Thermal Stability Test Reaction 1 3 Ml. Open-Tube Test Time From Start. Min. 0 2 4 5 7 8 9 10 13 15 17 18 isi/2 19 19% Temperature. C. Sample Oil 29 38 52 66 79 93 102 107 121 135 149 163 171 204.5 215.5 29 54 71 79 90.5 102 107 113 126.5 139.5 151.5 163 16S 188 193 Tran,former Setting 60 60 60 60 60 60 60 60 70 70 SO 90 100 110 Off Comments Slight gassing Gassing Gassing Gassing rapidly Gassing rapidly Gassing rapidly Gassing rapidly Gassing rapidly Testing Reactions and Materials for Safety 305 is not shown, heating is continued until the sample temperature reaches 600F or until the sample is completely decomposed. Table 19.1 is an example of one of the first tests. The exotherm experienced when this reaction got out of hand in large-scale equip ment caused no injuries but considerable building damage. This explosion was the impetus that led to the development of the test. Note that the entire test took only 20 min to run. Slow bubbling was observed at 102C. This bubbling increases with temperature and becomes quite vigorous. Note that at a bath temperature of 163C the sample temperature equals the bath temperature and then begins to exceed it as the exotherm proceeds more and more rapidly. Inci dentally, more precise tests that will be described, definitely showed that the exotherm begins at 90 to 95C. Figure 19.2 shows the last 5 min of the test graphically. Remember that this is a relatively crude test whose sole purpose is to uncover an exotherm and not to define precisely where it begins. FIG. 19.2. Temperature curves--thermal stability test. 306 Safety and Accident Prevention in Chemical Operations FIG. 19.3. Still buried 4 ft into the ground by uncontrolled reaction. FIG. 19.4. Still after removal. Testing Reactions and Materials for Safety 307 The bubbling observed was a good indication, but not all exothermic reactions give off gases in the early stages. Whenever the sample temperature exceeds the bath temperature it is a sure indication that the reaction is exothermic, and in large-scale equipment this can be serious. To repeat, this test is most suitable for oxidation and poly merization reactions involving compounds of low volatility. Volatile compounds give erroneous results here but if the volatile is an inert solvent, not one of the reactants, the results can be meaningful to an experienced observer. Where two phases are involved agitation should be provided by bubbling nitrogen through the mixture, and it may also be desirable to use larger quantities here. If an aging period is required to achieve a hazardous condition, such as in peroxide formation, this test will not discover the reaction. Finally, since this test merely determines exotherms, we can expect to find a number of exotherms at very high temperatures which do not constitute a particular hazard. An experienced chemist, who knows the process involved and the meaning of this test, should be able to interpret the test results satisfactorily. The reaction discussed previously was an oxidation by sulfuric acid. The mixture normally was heated to 90C, held for % hr and then cooled. The reaction vessel was a 500-gal glass-lined reactor, rated at 90 lb and insulated. This time it was decided to heat it to 90C and let it cool by itself. Unfortunately, the vessel maintained excel lent adiabatic conditions. The slow and easily controllable exotherm at 95C became uncontrollable with this result. The still buried 4 ft into the ground is shown in Fig. 19.3. It penetrated an acid brick-covered concrete floor. The still after re moval is shown in Fig. 19.4. Note that it was not badly distorted. This was not a detonation, and there was not any fire after the explosion. The hole in the roof about 20 ft directly above the vessel is shown in Fig. 19.5. The head of the still embedded in concrete 250 ft away is in Fig. 19.6. It reached a height estimated at 170 ft. An indication appeared at 102C showing there was some bubbling occurring, some slight exotherm. At 163C it was confirmed in the test. Even if it is assumed there was no bubbling at 102C, merely the reaction at 163C, this should be enough indication that at some lower temperature, possibly 60 to 70C lower, an exotherm can occur, and if this reaction is to be carried out in anything larger than a small laboratory flask a more precise indication should be obtained of where the exotherm begins and how rapidly it progresses. The next test employs a Dewar flask, and it must be run in a barricaded area. A diagrammatic sketch of the flask is shown in imt/iuwii. i-EV'cLtiPMENT LiBfiARV P. 0. BOX Ml mtqn mee i, Louisiana ETC 03336 ETC 03337 To controller Vibrator Temperature, 309 310 Safety and Accident Prevention in Chemical Operations off. If nothing happens in 5 min heat is reapplied. The procedure is repeated to 300C. Let us return to the previous example and the Dewar flask de termination in Fig. 19.8. Curve A show's the calculated time-tempera ture curve for a 500-gal jacketed and insulated reactor with only static air in the jacket. Curves B, C, and D show' the curves for 125 ml of the reaction mixture in a 200 ml Dewar flask. Note how sharply the temperature affects the occurrence of an exotherm. Curve E show's the Dewar flask curve for 125 ml of the reaction medium with the active ingredient removed. Curve F shows the rate of increase in temperature of 100 ml of reaction mixture at 160C Rupture disc assembly ;( FIG. 19.9. Pressure tube test apparatus. ETC 03339 Testing Reactions and Materials for Safety 311 in an uninsulated 250 ml round bottom flask. This rate is about lC/min as compared to about 40C/min for Curve A, a factory re actor. A 10-ml sample in a test tube at 160C will drop in tempera ture. Incidentally, even though it could be demonstrated that the exotherm begins very slowly at 95C, calculations indicate that with a 500-gal volume in this reactor and with full cooling water on, the reaction still could be controlled in the range of 130 to 140C. With the Dewar flask test a combination of a rapid exotherm and substantial gas evo lution is a sure indication that in factory equipment there would be an explosion. Other tests are used in thermal stability studies. The pressuretube test in Fig. 19.9 was developed by the Bureau of Mines.12 The stainless-steel tube can be insulated as shown here or immersed in a heated oil bath. The heating-rate technique can be employed by observing the jacket versus sample temperatures, or the tube can be heated to a given temperature and the temperature increase observed over a 5 to 15 min period. This is a good precision method where noncondensable gases are produced. It would not detect polymer ization, and it can be rather difficult to interpret the data received. This bomb must be barricaded. The improved thermal stability bomb in Fig. 19.10 developed by Dr. G. A. Mead of the Air Reduction Company is fully described in the publication Liquid Propellant Test Methods, Recommended by the Joint Army-Navy-Air Force Panel on Liquid Propellant Test Methods.1* This small bomb is immersed in a bismuth-lead alloy bath. An air vibrator agitates both the bath and the sample bomb. This is an excellent and precise tool. Exotherms on the order of 2 and 5F can be detected. This entire apparatus must be barricaded, but it is possible to enclose it safely in an isolated laboratory. Another interesting approach was developed by Dr. Joseph J. Martin when he was searching for the cause of the devastating 1953 explosion in a plant at Tonawanda, New York.15 Tertiary butyl peracetate was the compound involved. It would not detonate when heated to dryness and would not detonate when subjected to the shock from .an ex ploding blasting cap. Dr. Martin discovered that if he inserted a 50-watt coil in the liquid and turned it on, the rapid heating of the sample caused it to detonate every time. Perhaps this phenomenon is due to compression of bubbles or to the localized high temperature which initiated the decomposition. The latter is very plausible because hot spots created 312 Safety and Accident Prevention in Chemical Operations SCALE* ABOUT TWICE ACTUAL SIZE THERMAL STABILITY BOMB SCHEMATIC DIAGRAM FIG. 19.10. Thermal stability bomb. when the heat could not be dissipated rapidly enough to the surround ing liquid does cause decomposition, and presents a yield problem in factory equipment even with relatively stable materials. The thermal stability tests are recommended because they are re producible. Many modifications of closed vessel tests are being used with success. Particularly valuable are the y2 or 1-liter bombs used where the problem of high volatility is encountered. The importance of thermal stability determinations cannot be over emphasized. If the various mixtures which can be reasonably expected are tested, the great majority of the possible exotherms will be revealed. Where factory or pilot plant operations are contemplated, the more exact Dewar flask and closed vessel tests should be run on the most suspicious mixtures. If instability is observed at a relatively low temperature and if there is a possibility of mechanical instability-- this means if a nitration is involved or peroxides, or diazo compounds --compounds and reactions where mechanical instability has been known, determinations should be made. There are organizations that will do this work, using apparatus such as the following: In Fig. 19.11, an impact tester employs a fixed weight dropping at varying heights on a small amount of liquid in a precisely designed ETC 03341 Testing Reactions and Materials for Safety 313 sample cup. The impact sensitivity is determined by observing a stainless-steel diaphragm. A hole in the diaphragm caused by a piston in contact with the diaphragm is positive. The mechanism of explosion of liquids in the drop-weight test is reported to be thermal ignition by compression of a bubble, followed by a normal deflagration process. A full description of this apparatus can be found in the previously mentioned Liquid Propellant Test Methods,u This tester will determine the ease of ignition through mechanical impact but not whether the ignition once initiated can be propagated. A further description of the meaning of this test and the next one (Fig. 19.12) can be found in the article "Evaluating the Explosive Character of Chemicals," by R. Van Dolah.12 The drop-weight tester requires that it be operated remotely but no real barricading is necessary. The card-gap test shown in this figure requires a true explosion-resistant test cubicle and an isolated location in order to avoid the consequences of the shock wave and the noise. This is truly a rigorous test for any compound or mixture, and it will FIG. 19.11. Drop-weight tester. ETC 03342 314 Safety and Accident Prevention in Chemical Operations !! FIG. 19.12. Card-gap test apparatus for shock sensitivity. determine whether ignition can be propagated to full detonation. We noted previously that nitroethane which by itself was not sensitive to shock when tested by card gap, was sensitive when 5% by weight of butylamine was added. It is probably true there is only a remote chance of encountering an initiator comparable to the 50 g of tetryl used in close proximity to the sample in this test. This test was run at room temperature with a small quantity of sensitizer. A process de velopment chemist in the laboratory, or an operator's error can result in having a mixture at 50C containing more sensitizer. Such a mixture could detonate from a much smaller shock, perhaps even dropping a flask on the floor. Knowing that the mixture is shock sensitive is essential in order to prevent these accidents. In Fig. 19.13, the plate with the hole is similar to the hole produced ETC 03343 ETC 03344 316 Safety and Accident Prevention in Chemical Operationt or shock sensitivity has been discovered, the reaction may stil] he run safely. In many cases an inert diluent or a desensitizing agent' added. For example, suppose an exotherm begins slowly at 100C ^ reaction in benzene is run without any problem. Since the benzene boils at 80C, all the benzene must be vaporized before a higher tem perature is reached. This could be a sufficiently good safety factor for a small scale supervised run with careful control of the reaction temperature, the quantity of reactants, the addition rates, and so on Inert solvents also act as good desensitizing agents for shock sensitive systems. For instance, the shock sensitivity of nitromethane shows up very dramatically when tested in the card-gap apparatus. When 15% by weight of benzene is added to nitromethane, the mixture will not be shock sensitive by this test. In conclusion: The tendency toward employing highly reactive com pounds and mixtures must be recognized and dealt with. The chemist's normal sources of information do not give proper attention to the possibility of instability, but there are other sources that could be of help. The chemist should take the half hour necessary to use the melting point apparatus and from this simple screening test, determine if other tests should be run. The chemist is the one who has to prepare some of these potentially hazardous mixtures in order to run the test. He should start on a very small scale, in a hood, and keep himself pro tected at all times. Management should decide whether to run the other tests or have them run elsewhere. A final and most important word of caution on testing--there is no guarantee that an explosion will not occur. The art of testing is very new. Enough is not known of the various mechanisms involved in explosions to devise sufficient tests. The right contaminant or sensitizer or the right amount at the right temperature or the right pressure may not have been tested. But if testing is done intelligently reasonable assurances are obtained that the rumbling noise is just thunder or a jet plane. REFERENCES 1. Manufacturing Chemists' Association, Inc., 1825 Connecticut Avenue. X.W., Washington, D. C. 2. National Safety Council, 425 N. Michigan Avenue. Chicago, Illinois. 3. Manual oj Hazardous Chemical Reactions, National Fire Protection Associa tion, 60 Batterymarch Street, Boston, Mass., 1964. 4. National Board of Fire Underwriters, 85 John Street, New York, New York. Testing Reactions and Materials for Safety 317 5. Publications Distribution Section, U. S. Bureau of Mines, 4800 Forbes Street, Pittsburgh. Pa. 6. The Handling and Storage of Liquid Propellants, Office of the Director of Defense Research and Engineering, U. S. Dept, of Defense, U. S. Government Printing Office, Washington, D. C. (January, 1963). 7. D. M. Tenenbaum, Testing with Storables, A. R. S. Paper 1263-60, American Institute of Aeronautics and Astronautics, 1290 Avenue of the Americas, New York, New York. 8. A. B. Steele and J. J. Duggan, "Safe Handling of Reactive Chemicals,'1 Chemical Engineering, Vol. 66, No. 8 (April 20, 1959), pp. 157-168. 9. M. A. Cook, The Science of High Explosives, ACS Monograph No. 139, Rein hold, New York (1958). 10. F. P. Bowden and A. D. Yoffe, Initiation and Growth of Explosion in Liquids and Solids, Cambridge University Press (1952). 11. Explosives, Propellants and Pyrotechnic Safety Covering Laboratory, Pilot Plant, and Production Operations, U. S. Dept, of Commerce, Office of Tech nical Services, AD 272424, U. S. Government Printing Office, Washington, D. C. 12. R. W. Van Dolah, "Evaluating the Explosive Character of Chemicals,'' Ind. Eng. Chem., Vol. 53, No. 7 (July, 1961), pp. 59A-62A. 13. R. H. Albisser and L. H. Silver, "Safety Evaluation of New Processes," Ind. Eng. Chem., Vol. 52, No. 11 (November, 1960), p. 77A. 14. Liquid Propellant Test Methods, Recommended by the Joint Army-Navy-Air Force Panel on Liquid Propellant Test Methods, the Liquid Propellant In formation Agency, Johns Hopkins, Silver Spring, Maryland. 15. Joseph J. Martin, "Tert-Butyl Peracetate--An Explosive Compound," Ind. Eng. Chem., Vol. 52, No. 4 (April, 1960), p. 65A. ADDITIONAL REFERENCES P. Nawiasky, F. Ebersole, and J. Werner, "Explosive Reaction of Diazonium Compounds with Sulfides of Sodium," Chem. Eng. News, Vol. 23, No. 14 (July 25, 1945), p. 1247. Case Histories of Accidents in the Chemical Industry, Vol. 1, 1962, Manufacturing Chemists' Association, Inc. National Board of Fire Underwriters Research Report No. 12, Nitroparaffins and their Hazards; National Board of Fire Underwriters Research Report, No. 11, Fire and Explosion Hazards of Organic Peroxides. J. M. Kuchta, G. H. Martindill, M. G. Zabetakis, and G. H. Damon, Flam mability and Detonability Studies of Hydrogen Peroxide Systems Containing Organic Substances, Bureau of Mines Report of Investigations 5877. C. S. Robinson, Explosions, Their Anatomy and Destructiveness, McGraw-Hill Book Co., N. Y., London, 1944, 88 pages. "Processing Under Extreme Conditions," Ind. Eng. Chem., Vol. 48 (May, 1956), p. 826. M. L. Bowser, F. C. Gibson. Pulse-Forming Circuitry for Explosives Research, Bureau of Mines Report of Investigations 5985. A. M. E. Siemens, "The Hazards of Organic Peroxides," British Plastics, Vol. 35 (July, 1962), p. 357-360. E7c 03347 20 Shock Sensitivity and Its Evaluation Robert W. Van Dolah, Ph.D. Shock sensitivity or ease of initiation of detonation is another mani festation of chemical instability. In contrast to the relatively slow chemical changes that characterize the usual decomposition or oxida tion reactions, exceedingly rapid chemical reactions may be initiated by shock waves in potentially explosive systems. The discussion that follows is limited to means of evaluating the tendency of materials to exhibit this type of instability. The terms "detonation" and "explosion" are frequently misused or interchanged. "Detonation" is often applied to very violent explo sions accompanied by loud noise or shock waves or to explosions causing very severe damage. Strictly speaking, the term "detonation" should be limited to processes in which an exothermic reaction takes place in a high-pressure wave that advances with supersonic velocity through the unreacted material; in contrast, flames or deflagration waves travel at less than sound velocity. Moreover, except during the buildup or decay of a detonation, the velocity of propagation ordinarily is constant and is defined by the physical (fluid-thermo dynamic) variables of the system. The steady-state characteristic of a fully developed detonation provides a convenient means of recogniz ing this type of reaction, although the picture may be a little confused by the fact that two types of detonation exist. Normal detonation is characterized by high-wave velocities, ranging from 2000 to 3000 m/sec in gases and from about 3000 to 8000 m/sec in liquids and solids. Abnormal, or low-order detonation is frequently observed in liquids 319 ETC 03348 320 Safety and Accident Prevention in Chemical Operationt and has been occasionally reported in solid systems. In these reactions the velocity of the wave is only slightly supersonic with respect to the material undergoing decomposition, being of the order of 2000 m/sec Detonations are extremely damaging because of the accompanying high pressures. Even in gaseous systems, the reflected pressure, sensed by end-on collision with a wall, can be 40 to 200 times the original pres sure, compared to 6 to 8 times in a typical deflagration. The detona tion pressure developed by an explosive system is closely related to the density of the system. Thus, the detonation pressures of condensedphase materials are exceedingly high. Liquid and solid explosives give detonation pressures that may exceed 300,000 atm in a high-velocity detonation and reach as much as 5000 to 20,000 atm in a low-velocity detonation. Consequently, an appreciation of the tendency for chem ical systems to undergo these extremely violent reactions and of the corresponding initiation mechanisms is very important if disastrous incidents are to be avoided. Gaseous systems are detonable over limits of composition that are somewhat narrower than the corresponding limits of flammability. A deflagration, or ordinary combustion, frequently undergoes transition to detonation, especially in a gaseous system confined in piping. This process can conveniently be pictured as follows: The pressure waves from the deflagration continuously catch up with those developed at an earlier stage until a shock wave forms. The shock increases in strength until it is capable of initiating reaction, but only after an induction period. Finally the reaction is completed immediately be hind the shock wave which is thus supported by a constant input of energy that maintains a constant velocity. In condensed-phase sys tems, a detonation may be initiated by an identical situation if the materials are particularly sensitive to initiation or are very energetic. Primary explosives are placed in a separate class from other explosives because of their extreme tendency to go from deflagration to detona tion. Some liquids can go from deflagration to detonation when con fined, but the process is much more complex than that of solid sys tems. Sensitivity to initiation of any decomposition reaction is too often interpreted as detonability, whereas frequently the event observed is a deflagration. With solid or liquid mixtures, the most widely used test is a drop-weight test in which the sample is hit by a hammer or falling weight, sometimes through an intermediate plunger or pin. In the more sophisticated versions, a constant weight dropped from varying heights serves to compare the sensitivity of various systems, larger weight-height products indicating greater stability. Ordinarily, this FTc 03 34 9 jHtasSiiu *7' Shock Sensitivity and Its Evaluation 321 procedure does not lead to detonation except with very sensitive mate rials such as primary explosives. Generally, the result is an ignition, and little information is developed as to the potential consequences of this ignition. However, the limitations of this test should not preclude its use. It can and should be applied to any solid or liquid for which the estimated heats of formation and reaction (in the absence of air) suggest the possibility of an explosive reaction. The test is easy to carry out in the laboratory. A steel block, a few crystals or a drop of liquid, and a carpenter's hammer are all that is needed. A loud bang or even a pop, indicative of initiation, should warn the man at the bench that the substance warrants some care in handling. Like most sensitivity tests, the hammer or drop-weight test is very much affected by extraneous factors. This is particularly true of solids and liquids, where the presence of inert diluents or solvents, especially water, can act as an effective heat sink and modify the test results sig nificantly. The presence of bubbles may also have a marked effect on the sensitivity of liquids.1 Sometimes impurities can act as sensitizers. Grit increases the sensitivity of solid explosives, and nitromethane is sensitized by amines.2 Another limitation of the drop-weight test is that it does not characterize the energy released by the explosive reac tion of a given substance which may vary widely for compounds that show equal sensitivities. Thus nitroglycerin and lead azide are rather comparable in sensitivity as evaluated by the drop-weight test, but the heat of detonation of nitroglycerin is about seven times that of lead azide (1500 vs 220 cal/g).3 The sensitivity of condensed-phase materials to initiation of highvelocity detonation is most frequently determined by means of a cardgap test, first developed almost simultaneously in Great Britain and the United States. This test has undergone a number of modifications and is now applied in several "standard" versions. Essentially, the sample is subjected to a shock wave derived from a specific high ex plosive charge and attenuated by passage through an intermediate bar rier or gap. Originally, this barrier consisted of paper cards or wax, but now it is most commonly formed by stacks of plastic discs. Per foration of a steel witness plate placed above the sample indicates that a high-velocity detonation was initiated. In the most common version of the card-gap test, the sample is contained in a cup formed by a 3-in.-long section of 1-in., Schedule 40, extruded, black steel pipe, both ends of which are faced in a lathe; the bottom is closed by a thin diaphragm of polyethylene or Teflon.4 If the material to be evaluated reacts with ordinary steel, the pipe may be coated with Teflon enamel or replaced with a cylinder of aluminum, ETC 03350 322 Safety and Accident Prevention in Chemical Operations plastic, or glass. However, as these latter modifications may influence the test results, data obtained, for instance, in aluminum pipe should not be compared directly with those obtained in a steel pipe. The test is normally conducted at ordinary temperature and pressure, but when desired, elevated temperatures may be obtained by wrapping a simple inexpensive electrical heating tape around the sample cup. The booster (or donor) charge ordinarily used is a 50-g, cylindrical tetryl pellet approximately 1 in. x 1% in. in diameter, pressed to a density of 1.57 0.3 g/cm3. Although tetryl is not usually considered as unduly sensitive, it should be handled with great care. In addition, as it is quite toxic, precautions should be taken to avoid excessive contact with hands or other parts of the body. Tetryl is sometimes difficult to obtain; in this case it can be replaced by pentolite (50-50 pentaerythritol tetranitrate-trinitrotoluene). variable gap is built up from 1.625-in. diameter discs punched from .010-in.-thick cellulose acetate sheet. For gap thicknesses greater than 0.5 or 1 in., it is convenient to substitute a single thick disc or cylinder of polymethyl methacrylate (Lucite or Plexiglas) for an equivalent thickness of cellulose acetate discs. The witness plate or target is a cold-rolled, mild steel plate, 4 x 4 x % in. thick, placed directly above the sample cup (Fig. 20.1) and supported at a standoff distance of y16 to Ys in., usually by means of a tightly fitting cardboard collar on the cup. The sample cup, card gap, and donor charge are aligned on a common axis. A paper mailing tube may be used for this purpose with some additional spacers to center the acceptor and donor. A No. 8 commercial electric blasting cap, or a more powerful cap known as an Engineer Corps Special, is used to initiate the donor. These blasting caps are hazardous, and every possible precaution should be taken to avoid premature initiation; special emphasis should be placed on gentle handling and protection from electrostatic charges that may ac cumulate on personnel conducting the test. This test, which may involve 100 to 130 g of explosive partly confined in a fragment-producing container, requires that substantial protection for personnel be provided to shield against blast or fragments. This protection can consist of a reinforced concrete enclosure, all-steel cham ber, or some more elaborate structure. It is important to realize that fragments of the test set-up may travel a considerable distance; any open-faced barricade should be located in an area where no one will come within range of projected fragments. If reinforced concrete is used, an additional lining of boiler plate backed with wood is recom mended to protect the concrete against damage from fragments. An other point to be considered is that a positive result (explosion or ETC 03351 Shock Sensitivity and Its Evaluation 323 Witness plate (4" x 4" x ") detonation) can be accompanied by considerable noise which may lead to complaints from occupants of adjacent areas. Only personnel who have been fully instructed in the safe handling of explosives should attempt to conduct the card-gap test. A stand ard operating procedure should be followed to prepare and fill the sample cups, align the donor, insert the blasting cap, and place the charge in the bearing chamber. Some positive means must be provided to control the firing circuit. A locked safety box is normally used, and the person who places the detonator in its final position and connects the leg wires of the blasting cap to the firing line should be the sole possessor of the key. A siren, horn, or buzzer should sound a warning before the shot is fired. It is good practice to check the continuity of 324 Safety and Accident Prevention in Chemical Operations the firing circuit with a galvanometer of a type designed specifically for this purpose and available from explosives suppliers. When the test is positive, the resulting detonation may produce toxic fumes If it is negative (no detonation), unexploded material that can neverthe less be explosive or toxic may be scattered in the enclosure; serious accidents have resulted from accidental initiation of undetonated mate rials in bombproofs. Therefore, the area must be decontaminated; the means selected for this purpose depend heavily on the nature of the substances being tested. Following the shot, the witness plate is examined to determine the nature of the result. A clean hole in the plate indicates a high-velocity or normal detonation, although a very hard plate may be broken by such a reaction. If the plate is completely undamaged, it may be as sumed that there was no initiation of detonation. A dome or some other distortion of the witness plate indicates an intermediate reaction. In general, a bulge or rip in the plate is evidence of a low-velocity or incompletely developed detonation. The significance of such results is discussed later, but as the test is usually run, a low-velocity or in complete detonation is considered to be a negative result. The usual experimental design seeks to define the gap thickness at which there is a 50% probability of a high-velocity detonation. This 507c point may be conveniently determined witn a minimum number of shots, using the Bruceton up-and-down technique.5 The result is expressed either as the number of standard .01-in. cards or as the equivalent thickness in inches. Some typical card-gap data are given in Table 20.1. Other versions of the card-gap test have been developed to meet special needs. Frequently in research programs, suspect materials are available only in small quantities. For such cases, the Naval Ordnance Laboratory has developed a small-scale card-gap test6 in which the donor is a 1.4-in.-long, 0.2-in.-diameter RDX column loaded in a 1-in.-diameter brass cylinder. The sample is loaded into a similar brass cylinder; the gap material is Lucite or Plexiglas. The result of the test is determined by the depth of dent in a steel witness plate.7 Also, the Naval Ordnance Laboratory uses a larger-scale card-gap test to evaluate propellant materials. A 5%-in.-long acceptor is con tained in a 1.437-in.-id, 1.87o-in.-od, cold-rolled steel tube; the donor is a 2-in. by 2-in. tetryl or pentolite charge. Cellulose acetate cards or Lucite cylinders are employed as before in the gap.s A 6 x 6 x %-in. mild steel plate is again used to determine the result of the test. In yet another version, the Bureau of Mines employs charges long enough to allow insertion of pressure-sensitive or ionization-sensitive probes. Used in conjunction with counterchronographs or oscillo- Shock Sensitivity and Its Evaluation 325 TABLE 20.1. Typical Card-Gap Results Nitromethane Nitromethane-ethylene diamine (90/10) Nitroethane Nitrobenzene-nitric acid (30/70) NG-EGDN (steel cup)3 NG-EGDN (aluminum cup)3 Dinitrotoluene (solid) Dinitrotoluene (liquid) NH4C104 (200 mesh) NH4N03 (200 mesh)* NH4N03 (200 mesh) Density, g/cm3 1.13 -- 1.05 -- 1.6 1.6 1.27 -- 1.39 1.20 .41 Gap value, inches 0.27 2.3 < -0 > 5.0 L4 1.2 .90 2< .0 1.23 < -0 1.46 1 Low-velocity detonations have been obtained at gaps as great as 110 in. 2 Liquid dinitrotoluene has a critical diameter of many inches. 3 Mixture of 50% nitroglycerin--50% ethylene glycol dinitrate. * Ammonium nitrate at this density has a critical diameter well over 1 in. scopes and simple electronic circuits, these probes make it possible to measure wave velocities. This test arrangement (Fig. 20.2) has proved effective as a means of distinguishing low-velocity detonations from unstable (accelerating or decaying) detonations which all affect the witness plate in the same way when shorter test charges are used. Steady low-velocity detonations destroy the entire length of the pipe, produce a dome or other substantial damage in the witness plate, and yield wave velocities of approximately 2000 m/sec. With a decaying detonation, only the bottom portion of pipe next to the gap is destroyed and wave velocities, measured by pressure-sensitive probes, are in the sonic range. An accelerating detonation should reach normal velocityin the long charge and should cause a hole in the plate. Low-velocity or low-order detonations are extremely- important in assessing the potential hazards of explosive systems. However, it is only very recently that any comprehensive understanding of their nature has been achieved. Earlier investigators reported propagation velocities equal to, or slightly above, the velocity of sound, but because of the difficult experimental and theoretical problems posed by these reactions, they were little studied. It is now known that such detona tions are associated with the breakup, or cavitation, of liquids caused by an interplay of shock and rarefaction waves, some of which are de rived from the walls of the container.9 The very anomalous results for nitroglycerin shown in Table 20.1 can be attributed to the relative 326 Safety and Accident Prevention in Chemical Operations ease of initiation of low-velocity detonation in the two kinds of metal containers. The threshold of the shock amplitude necessary to initiate such detonations is exceedingly low. For example, nitroglycerin has been initiated to undergo low-order detonation in the 1-in.-diameter card-gap test with a gap of 110 in. of Lucite. In fact, this type of rrc 0:13 > a Shock Sensitivity and Its Evaluation 327 detonation has been initiated in nitroglycerin by a donor weighing as little as 1 g, across a barrier of about 5 in. of brass, known to be a more effective shock attenuator than Lucite. In addition to the error in evaluation that low-velocity detonations can introduce into the card-gap test if only a witness plate is used as criterion, further misinterpretation may result if the critical diameter for detonation of the material tested is greater than the actual diam eter of the acceptor. This critical diameter may be defined as the minimum charge diameter which will allow steady-state propagation of a detonation. It is related to the rate of chemical reaction, or energy release, and to the rate of energy loss through expansion of the products and associated rarefaction waves. Critical diameters may be as little as a millimeter or less in the case of nitroglycerin and nitric acidnitrobenzene solutions, and as much as 15 in. or more for fertilizer-grade ammonium nitrate.10 For solid materials they are strongly dependent on particle size and density as illustrated by the data on ammonium nitrate in Table 20.1. Thus, if prilled ammonium nitrate is ground and sifted into a container to form a very low-density charge it can detonate reliably at ordinary temperatures for diameters as small as 1 in. Similarly prilled nitrate, heated above 140C, can be initiated across about 1.5 in. of plastic to yield a stable detonation in a 1-in.-diameter charge, as the critical diameter decreases with increasing temperature for both solids and liquids. This behavior is very frequently useful when dealing with insensitive systems. In some cases, materials that have large critical diameters can be evaluated as smaller diameter acceptors if the test is performed in very heavy-walled containers. This technique is frequently applied to solid explosive materials. It has limitations when applied to liquids because low-velocity detona tions seem to develop most readily, and from the weakest shocks, in heavy-walled containers. Finally, materials that have large critical diameters may still be tested by using powerful donors and short charges. The reaction is sufficiently overdriven to result in some threshold pressure at the far end of the sample even though the detona tion is decaying. This approach has been used to study the sensitiza tion of ammonium nitrate by organic materials.11 There is a rather widespread tendency to deprecate the results ob tained with explosive-driven shocks. It is frequently argued that in actual practice no explosives are present to provide similar shocks. However, quick-acting solenoids, gear pumps, cavitating impellers, and "water hammer" in liquid-filled lines can readily result in shocks of comparable amplitude that can initiate deflagration, as well as low- or 328 Safety and Accident Prevention in Chemical Operations high-order detonation, or can at least produce incipient reactions lead ing to one of these catastrophic reactions. In the case of solids, impact friction, or electric sparks may initiate a deflagration reaction which' in the more sensitive systems, may undergo a transition to detonation before the pressure resulting from the deflagration is dissipated. The maximum possible pressure on a system is frequently, but mistakenly thought to be only the hydrostatic pressure. However, when a reaction is very rapid and energetic, the pressure is determined by the inertial mass of the reacting material or of its confinement. In the case of a pile of solid material, this pressure is related to the acceleration im parted to the material as follows: P = pha where P is the density, h is the height of the pile, and a is the accelera tion. In the case of a liquid in a pipe, the maximum pressure may similarly be determined by the inertial mass of the liquid to be accel erated, or by the dynamic strength of the pipe. For example, Schedule 80 seamless-steel tubing requires a pressure of about 10,000 psi to burst under dynamic loading. In conclusion, when evaluating the potential hazards of a system, it is not enough to consider only those incidents that are likely to occur and to seek reassurance by assuming the absence of strong initiating shocks. On the contrary, it is essential to assess the true explosive potential of the system and to assume that the conditions for the in itiation of a reaction leading to a catastrophic explosion may be real ized if suitable precautions are not taken. The card-gap test provides a useful technique for making such assessments. However, it should not be regarded as the only one--other experimental and analytical methods are available for evaluating energy potential, the tendency to decompose under thermal shock, the decomposition temperature, and other important factors. These should not be neglected in de termining the stability of materials that may be hazardous under conditions of manufacture, storage, or use. REFERENCES 1.. F. P. Bowden and A. D. Yoffe, Initiation and Growth of Explosion in Liquids and Solids, Cambridge University Press, Cambridge, England, 1952. 2. R, W. Van Dolah, J. A. Herickes, J. Ribovich, and G- H. Damon, "ShockSensitivitv Studies of Nitromethane Systems," Compt. rend. 3le Cong. Inter nal. Chim. Ind., Liege, Belgium, 2, 210-215 (September, 1958). 3. M. A. Cook, The Science of High Explosives, Reinhold, Xew York, 1958, Chap. 12. etc 03357 Respiratory Hazards and Protection 421 parachutes, life lines, and other devices which permit no compromise if human life is to be considered worth preserving. Training is a highly important aspect of respiratory protection, and it is the one phase of the respiratory protective program where the greatest improvement is needed if we are to derive maximum efficiency from existing equipment. Putting on a mask or apparatus for a few minutes once or twice a year is not adequate training. The United 422 Safety and Accident Prevention in Chemical Operations States Bureau of Mines Health and Safety Activities, through its district and subdistrict offices, conducts training courses in first aid, and also in the use of various emergency breathing apparatus. These courses can be modified to meet special needs on request. Addresses of offices which offer these courses may be obtained by contacting the Assistant Director, Health and Safety, United States Bureau of Mines, Department of the Interior, Washington, 25, D. C. This service of the Bureau is available to the mineral and allied industries, as well as to governmental agencies. The Bureau has mine-rescue equipment at each of its District and Subdistrict Health and Safety field offices. During training, breathing apparatus should be worn for relatively long periods, in dark and confined spaces, climbing hills or stairs, duplicating all manual labor expected, and in smoke-filled atmospheres while performing work by hand-carried or other portable lights. Smoke generators are commercially available which will quickly fill a room, a basement, a tunnel, or small building with a smoke that is FIG. 23.25. On-the-job training using simulated smoke from smoke bomb de velops confidence and experience in use of breathing apparatus. Training and retraining are vital to insure proper use in emergency. Respiratory Hazards and Protection 423 realistic but relatively harmless, and it can be ventilated out without damage or residue.22 Smoke bombs, which contain hexachlorethane, zinc oxide, calcium silicate, and potassium nitrate, are usually not injurious if used outside. However, in confined spaces they can be lethal. Forty-six fatal ex posures are on record; one was a 35-year-old fireman who attempted to extinguish the smoke bomb with a fire extinguisher. The bomb had been ignited at the bottom of a depression a few feet below ground level and surrounded by buildings on three sides. The zinc chloride smoke, which is extremely caustic to the mucous membranes, caused acute interstitial fibrosis resulting in death 18 days later. The "buddy" system and team drill should be practiced as in a real emergency. The use of life lines should be a part of this training whenever possible, and it should be a standard part of any under ground, tank, or smoky operation. Signals are used to communicate by mine rescue teams to the team members who are outside by pre arranged pulls on the hand lines. In the simple form, a code based on the word OATH in which 0 means OK, signal by one pull; A means advance or feed in more line, signal by two pulls; T means take up line, signal by three pulls; H means help, send aid, signal by four pulls. Stand-by men should already be masked and ready for entry in case the team in the mine or confined space calls for help. This same philosophy, of having stand-by personnel ready to go, should be encouraged in any emergency use of respiratory protective equipment. As mentioned previously, voice amplifiers and two-way radios may greatly aid in the communication problem, but any electrical device used in an atmosphere which may contain flammable gases or vapors, should have a "permissible" rating by the Bureau of Mines or the Underwriters' Laboratory for the gases or vapors expected. The need for proper physical examinations and medical control for persons wearing emergency breathing equipment is obvious, but it has been neglected in some instances in the past. A regular program of physical check-ups with particular attention to the respiratory and circulatory system, as well as the general mental and physical con dition, probably would have prevented some cases where inhalation of smoke combined with physical exertion, without or with respiratory protection, has produced serious illness. Stable pulse rates before, during, and after exercise, good general physical condition, moderate weight, good eyesight, and, where mouthpiece breathing is involved, proper teeth alinement, are all considered vital requisites to pre training by the Bureau of Mines instructors. A practice of not per mitting persons to return unprotected or alone to smoke, fumes, vapors, 424 Safety and Accident Prevention in Chemical Operations or gases after they have been seriously affected or overcome and revived, would help prevent more serious inhalation effects. Such restraining action may require physical force to implement in practice since a "patient" who is.partially recovered from fume or smoke inhalation may display highly irregular behavior. One recommenda tion is that persons sufficiently exposed to fumes, gases, smoke, and/or carbon monoxide to require treatment should not return to active duty in less than 4 to 6 hr, while those who have been rendered semi conscious or unconscious should rest 24 to 48 hr. Since chronic carbon monoxide poisoning is considered by some medical authorities to be a fact, and since carbon monoxide is not released by the blood as quickly as previously believed, the implications for fire fighting should be obvious. Conclusion The field of respiratory protection is dynamic--there is need for wider application of existing knowledge, proper use of existing equip ment, as well as research and engineering, to produce even better and more adequate devices, training aids, and basic and applied informa tion. It should be stressed that properly designed and carefully maintained breathing equipment, if used with full appreciation of its limitations, by healthy persons, properly and adequately trained, could eliminate most fume, gas, vapor, and smoke disabilities in the future. The ideal breathing apparatus for all applications has yet to be de veloped, and may never be developed until there is sufficient demand for it, backed by the willingness of the user to pay the cost, and this demand transmitted to developers and engineers who are both technically competent and have a zeal to improve the quality of breathing in man's complex life.26 Of all our human needs, none is more vital than the next breath. REFERENCES Air Pollution: 1. A Study oj Pollution--Air, a staff report to the Committee on Public Works, United States Senate, September, 1963, available from the Superintendent of Documents, United States Government Printing Office. Washington, D. C. 2. S. M. Farber and R. H. L. Wilson, The Air Ife Breathe, C. C Thomas. Springfield, Illinois, 1961. 3. L. Herber, Our Synthetic Environment, Knopf. New York, 1962. 3a. J. R. Goldsmith, International Agreement on Criteria for Air Quality, Arch, of Environ. Health. Vol. 9, No. 1, pp. 3-5 (July, 1964). Respiratory Hazards and Protection 425 4. Air Pollutiton, Section 1, Reference List of Publications, Technical Report A63-1, The Robert A. Taft Sanitary Engineering Center, Cincinnati, Ohio, Public Health Service, U. S. Department of H.E.W.. 1963. 5. Air Pollution Bibliography, Vol. I (1957), Vol. II (1959), The Library of Con gress, Science and Technology Division, Bibliography Section, Compiled for the Public Health Service, U. S. Department of H.E.W., Washington, D. C. (Index for both volumes in Vol. II). 6. Air Pollution Manual, Part I, Evaluation, American Industrial Hygiene Asso ciation, Detroit, Michigan, 1960. 7. Air Pollution Control Process Flow Sheets. American Conference of Govern mental Industrial Hygienists, Cincinnati, Ohio, 1961. 8. Air Sampling Instruments Manual, 2nd Edition, American Conference of Gov ernmental Industrial Hygienists, Cincinnati, Ohio, 1962. 9. M. B. Jacobs, The Chemical Analysis oj Air Pollutants, Interscience Pub lishers. New York. 1960. 9a. M. B. Jacobs. The Analytical Chemistry oj Industrial Poisons, Hazards, and Solvents, 2nd Edition, Interscience Publishers, 1949, p. 409. Threshold Limit Values: 10. Threshold Limit Values (revised and published annually), American Con ference of Governmental Industrial Hygienists, Cincinnati, Ohio. Documenta tion oj Threshold Limit Values, available from same address. See Appendix. Dusts, Mists, Gases, Smokes: 11. Dusts, Fumes, and Mists in Industry, Data Sheet 531, National Safety Council, Chicago, Illinois (National Safety News A?, No. 6. pages 89-105, June, 1963). 12. Fire Gases Research Report, 1952, National Fire Protection Association, Boston, Massachusetts. 13. The Pneumoconioses, Diagnosis, Evaluation, and Management, Council on Occupational Health. American Medical Association, Archives oj Environ mental Health, Vol. 7, No. 2, pages 130-171, August, 1963. 14. T. A. Rich, Characteristics oj Air-Borne Particles, paper No. 57-SA-56, Ameri can Society of Mechanical Engineers, New York. 15. Detection and Analysis oj Contamination, Manual ADM-30, Publications Dept., Millipore Filter Corp., Bedford, Mass., November, 1962. 16. Combustible Dust Hazards in the Plastics Industry, Committee on Fire Pre vention, The Society of the Plastics Industry, Inc., New York, 1963. 17. Fire Hazards oj the Plastics Manufacturing and Fabricating Industries, N.B.F.U. Research Report No. 1, Number M 65, The National Board of Fire Underwriters, New York. 18. Report oj Important Dust Explosions, 1957, National Fire Protection Asso ciation, Boston. Respiratory Protection: 19. Respiratory Protective Devices Manual. ACGIH and AIHA, 1963, available from Braun-Brumfield, Inc., Ann Arbor. Michigan. 20. S. J. Pearce, Bureau oj Mines Approval System for Respiratory Protective Devices, Bureau of Mines I.C. 7792, June, 1957. U. S. Bureau of Mines, Pitts burgh, Pa.; see also by same author. Bureau of Mines I.C. 7885, October 1958, with supplements to I.C. 7885, July 15, 1963 and January 1, 1964, which lists 426 Safety and Accident Prevention in Chemical Operations and describes all respiratory protective devices which have been approved by the Bureau of Mines to January 1, 1964, with address of manufacturers. 21. R. A. Fulton, F. F. Smith, and R. L. Busbey, Respiratory Devices for Protec tion Against Certain Pesticides, ARS-33-76, September, 1962 and Supplement 1, March 15, 1963, Entomology Research Division, Agricultural Research Serv ice, U. S. Department of Agriculture, Washington, D. C. 22. H. H. Fawcett, Living in the Air We Breathe, Transactions of Chemical Sec tion, National Safety Congress, 1957, National Safety Council, Chicago Illinois. 23. P. A. Breysse, "Code of Safe Practices for SCUBA Diving," Journal of the Amencan Society of Safety Engineers, Vol. IX, No. 7, pp. 15-18 (July, 1964). 24. National Safety Council, Accident Prevention Manual for Industrial Opera tions, 1964, 5th Ed., Chicago, Chapter 36, pp. 36-20, 36-39, and Data Sheet D-444, Respiratory Protective Equipment. 25. H. H. Fawcett, Speech Transmission through Respiratory Protective Devices, American Industrial Hygiene Association Journal Vol. 22, No. 3, pp. 170-174 (June, 1961). 26. American Standards Association, Safety Code for Head, Eye and Respiratory Protection, Z2.1-1959, New York. Photo credits in this chapter all courtesy General Electric Research Laboratory unless otherwise indicated in caption. ETC 03455 24 Eye Safety in Chemical Processing Joseph Guelich If we wear glasses there is a good chance that they are safety glasses with hardened lenses. If we have a small child who wears glasses, they may be safety glasses. If we have children in chemistry labo ratories in high school or college, the schools may have a rule that the students must wear safety glasses. If we wear glasses and engage in such activities as squash racquets, the chances are that we have equipped ourselves with safety glasses. These are all indications that today there is a clearly discernible trend toward universal eye protec tion, off the job and on. Of course, a complete eye protection program in chemical processing neither begins nor ends with a safety-glasses program. We have, you might say, four lines of defense: preventing the accident, preventing the injury, guarding the person, and minimiz ing the injury. 24.1. PREVENTING THE ACCIDENT One of the most familiar examples of preventing the accident is something learned in high school chemistry, to the effect that sulfuric acid should be added to water and not vice versa. There are many examples. One user of caustic soda found that he was having trouble making up caustic solutions by adding solid caustic to water. Despite repeated admonitions, the operators would add the solid caustic too fast and the heat of solution w:ould cause the vessel to spit and boil over. They found an acceptable solution by replacing purchases of 427 ETC 03456 Shock Sensitivity and Its Evaluation 329 4. Trade names are used in this paper for identification only, and endorsement by the Bureau of Mines is not implied. 5. \V. J. Dixon and F. J. Massey, Jr., Introduction to Statistical Analysis, 2nd ed., McGraw-Hill, New York, 1957, Chap. 19. . 6. J. N. Ayres, "Standardization of the Small-Scale Gap Test Used to Measure the Sensitivity of Explosives," NAVWEPS Rept. 7342, U. S. Naval Ordnance Laboratory, White Oak, Md., Jan. 16, 1961. 7. Warren M. Slie and R. H. F. St'resau, "Small-Scale Dent Test for Confined Charges," NAVORD Rept. 2422, Naval Ordnance Laboratory, White Oak, Md., April 23, 1952. 8. A. B. Amster, E. C. Noonan, and G. J. Bryan, "Solid Propellant Detonability," ARS J., 30, 960-964 (October, 1960). D. Price and I. Jaffe, "Large-Scale Gap Test: Interpretation of Results for Propellants," ARS J31, 595-599 (May, 1961). 9. R. W. Van Dolah, R. W. Watson, F. C. Gibson, C. M. Mason, and J. Ribovich, "Low-Velocity Detonation in Liquid Explosives," International Conference on Sensitivity and Hazards of Explosives, London, Oct. 1-3, 1963. 10. H. H. Fassnacht and C. H. Winning, "Detonation Characteristics of Prilled Ammonium Nitrate," International Conference on Sensitivity and Hazards of Explosives, London, Oct. 1-3, 1963. 11. W. G. Sykes, S. Meyers, J. R. Parks, and S. S. Chandler, "The Effect of Low Concentrations of Organic Materials on the Properties of Ammonium Nitrate," 48th Nat. Mtg. AIChE, Denver, Colo., Aug. 26-29, 1962. 21 Safe Handling of Flammable Materials William S. Wood 21.1. INTRODUCTION Flammable liquids and gases are extremely important to our modem way of life and constitute a major volume of present-day commerce. Billions of gallons of highly flammable motor fuel are manufactured and marketed to the motoring public annually with a high degree of safety. On the other hand many fires with accompanying injury and death result from improper storage and use of flammables, especially in and around the home or small business. The difference lies in appreciation of the hazards of the materials and the application of safe procedures. i ] Flammable materials are utilized in a high proportion of processes in the chemical and petrochemical industries. Benzene, olefins, and ethers are indispensable raw materials in organic syntheses. They also may be used as the vehicles in which reactions occur or as solvents to effect separations. Cleaning operations utilize large amounts of flammable liquids, and the fuels used to supply process heat may be volatile hydrocarbons. Flammability is one of the hazardous properties that must be evaluated and dealt with in order to utilize these valuable materials with a minimum of injury and loss. It is important that the user learn to evaluate the physical and chemical properties that will be pertinent to the environment and the application of each material. 330 ETC 03359 Safe Handling of Flammable Materials 331 21.2. THE COMBUSTION OF FLAMMABLES Although combustion is one of the oldest known chemical reac tions, its mechanisms are imperfectly understood and erroneous con cepts are held by many who work with flammable materials or fight fires in wdiich flammables are involved. This discussion is an attempt to guide in the recognition of valid hazard criteria, in the selection of safe environmental conditions, and in the emergency action needed when an accidental release occurs. The Anatomy of Fire Minimum requirements for a flame or the propagation of a flame front are often represented in terms of the "Fire Triangle." Fuel, oxygen, and heat are shown as the three sides in Fig. 21.1. In relation to flammable liquids and gases the three requirements are more ac curately described as shown in Fig. 21.2. 1. Gas or vapor within certain limits of concentration. 2. Air containing a minimum concentration of oxygen. 3. An ignition source of minimum temperature and energy. A fire results when all three sides of the triangle are in place. However, any two of the above requisites can co-exist without a fire as long as the third is not added. Since an oxygen-bearing atmosphere surrounds nearly all normal activities, the problem usually consists in keeping flammables separated from all possible ignition sources. FIG. 21.1. The fire triangle (complete). 332 Safety and Accident Prevention in Chemical Operations The Fuel If even a small flame is passed over a pan of methanol, ignition occurs promptly in the vapor above the surface. The same flame over glacial acetic acid or naphthalene at ambient temperature would not ignite either material. If, however, the acetic acid is heated only slightly, enough vapor will be generated to permit ignition and, with further heating, the naphthalene also could be burned. Liquids and solids do not burn as such. They give off vapors and gases which mix with air and can be ignited when a combustible mixture is at tained. Obviously volatility is a primary factor in determining the condi tions under which an ignitable mixture can occur. Classical expres sions of volatility such as vapor pressure and boiling point, while definitive, do not of themselves relate directly to flammability. The flash-point determination is an empirical but highly satisfactory method of determining the minimum temperature at which an ignitable mixture exists above the surface of a liquid. The American Society for Testing and Materials has standardized a number of methods for determining flash point. The tag closed tester (ASTM D56)1 is used for testing liquids with flash point below 175F. The Pensky-Martens Closed Tester (ASTM D93)2 is used for materials (mostly fuel oils) with flash points 150 to 230F. The Cleveland Open Tester (ASTM D92)3 is used for high-flash mate rials. SSfet - Safe Handling of Flammable Materials 333 On the basis of volatility expressed as flash point and boiling point, ]\tFPA 30, 1963 defines flammable and combustible liquids as follows:4 Class IA Flash point below 73F Boiling point below 100F Class IB Flash point below 73F Boiling point 100=F or above Class IC Flash point 73 to 99F Class II Flash point 100 to 130F Class III Flash point 140 to 199F Examples: Pentane Ether Benzol Ethanol Amyl Acetate Acetic Acid Decalin Aniline Naphthalene Caution is recommended in relying too heavily on flash point as the major criterion of flammability. Liquids atomized into a fog or mist can be readily ignited far below the flash point of the material. Froths can likewise be flammable. Combustibles absorbed in porous materials such as insulation can ignite under surprisingly mild tem perature conditions. Reid vapor pressure (ASTM D323)5 is a specification measurement of volatility applied to gasoline and jet fuels. Its units are pounds per square inch gage at 100F. While originally intended as a per formance specification, it is a useful indication of volatility in storage and handling. The fact that a "safe" material has been heated in processing above its flash point and thus become readily ignitable may be overlooked by the casual operator. Also a small amount of volatile material in a relatively high boiling mixture will drastically lower the flash point and render the whole volume dangerous. Finely divided dusts of combustible solids can constitute a severe fire hazard. Sulfur, carbon, polymers, and many other solids form explosive suspensions in air. Sometimes a minor explosion or other disturbance disperses dust that has accumulated on flat surfaces for long periods of time. The result may be a severe explosion (see NFPA 654-63, "Prevention of Dust Explosions in the Plastics Industry").6 The Atmosphere Most situations involving flammable-material safety occur in the presence of normal air (20 to 217c oxygen). Atmospheres are some times enriched by increasing the oxygen content, possibly to 1007c ETC 03362 334 Safety and Accident Prevention in Chemical Operationt oxygen. Ignition is more easily accomplished and combustion is much more rapid in pure ogyxen or in oxygen-enriched air. Air deficient in oxygen can occur naturally from decay or fermen tation of organic material. Dilution with inert gas such as nitrogen or carbon dioxide may be intentional in order to inhibit combustion For each flammable material there is a concentration of oxygen below which a flame will not be propagated. For many substances the minimum oxygen content required to support combustion is approxi mately that required to sustain life in the human being (approxi mately 12%). Other oxidizing agents such as chlorine, fluorine, nitrogen oxides and hydrogen peroxides, while unusual in most industries, could be en countered in the chemical plant as well as on the launching pad Many such oxidizers are much more vigorous than oxygen and require special safety precautions. 21.3. IGNITION OF FLAMMABLE MIXTURES The autogenous ignition temperature is the temperature at which a small amount of a substance will spontaneously ignite in a given at mosphere and burn without further heat input. It is likewise a use ful guide to the maximum safe temperature of any surface in contact with vapor mixtures above the flammable liquid. The ignition temperature may be determined by a number of dif ferent procedures, and widely differing results may be obtained on the same material by different methods. One useful procedure is ASTM D286-58T, which is applicable to many flammable and com bustible liquids. Ignition temperatures of many compounds as de termined by the above and similar methods are listed in NFPA 325.' Kindling temperature is a term applied to solids to express the temperature to which a portion must be raised to initiate flame. Many factors such as size, shape, and purity affect the value for a given material. Spontaneous ignition of dry phosphorus or of drying oils is well known to the chemical industry. Recent additions to this category are the aluminum alkyls, certain boranes, and some silanes. Alumi num trimethyl ignites immediately upon exposure to air and this property has been utilized by injecting the alkyl into jet engines to re-ignite the fuel after a flame-out. Aluminum triethyl usually flames instantly upon exposure to air at rather low ambient temperature, while aluminum triisobutyl only fumes copiously and does not ignite unless the temperature is about 100F. ETc 03363 Safe Handling of Flammable Material 335 Hypergolic ignition of such mixtures as hydrazine-hydrogen per oxide are becoming commonplace in space vehicle systems. The characteristics of each such system should be determined prior to any plant design or operation. Flammable mixtures may be formed and exist harmlessly so long as no source of ignition is present within the system. The combustion process must be initiated by the introduction of a finite amount of energy. Ignition sources include hot surfaces, hot filaments, flames, hot gases, electric sparks, and adiabatic compression of the mixture itself. Hot electrical filaments such as heaters and broken electric lamps are effective igniters if a minimum energy of about 2 millijoules is available. Van Dolah et als showed that the temperature required to ignite a large volume of flammable substance decreases writh in crease in wire diameter. Husa and Runes9 showed that large metal surfaces must be con siderably hotter than the accepted ignition temperatures in order to initiate a flame. Absence of confinement and attendant convection currents possibly account for the higher temperatures. Electrical sparks are w'ell known as ignition sources particularly in gasoline engines or oil burners where they function in a "friendly" situation. However, high-tension sparks are not very likely to occur in the plant environment unless such an ignition system is faulty. Studies have showm10 that a spark with minimum energy of about 0.2 millijoules can ignite a flammable mixture near the stoichiometric proportions in air. Break sparks occur when open relays or switches are operated or a commutator is exposed. Adequate energy is present in most such systems to ignite a flammable mixture. Obviously a w'elder's arc would be a most effective igniting device. Friction sparks of a steel tool striking a stone or sparks from a grinding w'heel have been proven rather ineffective ignition sources. While nonferrous tools made of beryllium-copper have long been con sidered necessary to avoid spark ignition of hazardous atmospheres, experience has shown that few if any fires have been caused by the, use of steel tools. The American Petroleum Institute no longer in sists that nonferrous tools be used in the presence of flammable hydro carbons. Nonsparking tools are still used extensively in the chemical industry, and may have advantage particularly in the case of impact tools used in digging. Pumping of relatively clean organic materials can cause a static accumulation to be concentrated on the liquid surface in the receiving 336 Safety and Accident Prevention in Chemical Operations tank. Klinkenberg et al.11 demonstrated that high-velocity pumnin of jet fuel resulted in explosions in the vapor space above the liquid A dangerous static charge exists when the liquid contains enough impurity to allow the collection of charges but not enough contain! nation to make the liquid sufficiently conductive that the charge can bleed off rapidly. Many common liquids are sufficiently low in con ductivity that this dangerous situation obtains. Slow pumping and subsurface discharge aid in controlling the static buildup. Additives to "contaminate" the product and hasten static bleed-off have been offered but are not widely used. Floating-roof tanks of inerted tanks are commonly used to eliminate the vapor-air space above sensitive materials. The United States Bureau of Mines has recently studied this problem extensively under a contract with the American Petro leum Institute. Acetylene welding (and oxy-acetyiene cutting operations! are among the most common sources of ignition. Not only the flame itself but the white-hot metal shower may reach and ignite flammables. Plasma jets, lasers, and masers, while still largely experimental, may soon become sufficiently commonplace to be credited with being igni tion sources. Fuel and Oxygen It has been stated that only gases and vapors are capable of enter ing into the combustion while liquids must be vaporized and mixed with air before they can burn. The stoichiometric mixture represent ing the ideal composition for combustion is calculated after writing the chemical equation for burning pentane in air. C5H12 + 8 02 + 30 N, 5 C02 + 6 H20 + 30 N, 1 mole pentane vapor + 38 moles air --* 5 moles C02 + 6 moles H20 + 30 moles N2. Thus, 2.6 volume % of pentane vapor in 97.4% of air provides the theoretical fuel-oxygen balance for combustion. Flammable Limits If the concentration of vapor is reduced below the stoichiometric mixture it is termed "lean," and a concentration can be reached at which a flame will not propagate. At such a low concentration there is sufficient distance between fuel molecules for the intervening air to quench the flame front. The lowest concentration of vapor at which ETC 03365 Safe Handling of Flammable Materials 337 a flame can be propagated is called the lower flammable limit (or lower explosive limit). For pentane this is 1.5% of vapor in air as experimentally determined. If on the other hand the vapor concentration is increased above stoichiometric, the mixture can become so "rich" that there is insuf ficient oxygen to support combustion. The highest concentration of vapor in which a flame can be propagated is the upper flammable limit (upper explosive limit) 7.8% for pentane. The concentrations between the two values for a given material constitute the "flam mable range." Coward and Jones12 published the most comprehensive list of these data available. Figure 21.3 illustrates the relationship in another way. In an adiabatic closed system the temperature (and pressure) will increase when a flammable mixture is ignited. The temperature (or pressure) rise will be maximum at or near the stoichiometric, and it will be FIG. 21.3. Energy vs mixture for pentane. 338 Safety and Accident Prevention in Chemical Operations Flash' point Equilibrium temp, at upper flam limit FIG. 21.4. Relationship of partial pressure, flammable limits and flash point. less at both higher and lower concentrations. The temperature rise would become zero at the lower flammable limit and at the upper flam mable limit. It has been shown experimentally that the flammable range be Ehi comes wider with increasing temperature,13 doubtless because of in creasing molecular activity or enthalpy of the mixtures. Figure 21.4 illustrates how the UFL concentration increases slightly with tem perature, and the LFL line descends as temperature increases. These coordinates can also be used to plot the vapor pressure of the substance with increasing temperature. The intersection of the vapor-pressure line with the lower flammable limit line at .4 is where air above a liquid contains just enough of the vapor to allow a flame to propagate. The temperature at .4 can be experimentally determined as the flash point. ETC 03367 Safe Handling of Flammable Materials 339 While not usually designated or susceptible to experimental determi nation the temperature at intersection B is of interest and can be es timated rather easily. Below this temperature a mixture cannot possibly be too rich to burn. In other words, between these two temperatures, A and B, a tank having air above the liquid would al ways have a flammable zone. At temperatures above B the mixture will be nonflammable if vapor-liquid equilibrium actually exists, but may be flammable if equilibrium is not achieved or if air is drawn into the tank. (A more extensive treatment of flammable limits and ignition temperatures is presented by G. W. Jones in a chapter he wrote in Patty, Industrial Hygiene and Toxicology, Vol. I, Second Edition, pp. 511-546, Interscience, New York, 1958.) 21.4. ATMOSPHERES OTHER THAN AIR--EFFECT ON FLAMMABLE LIMITS Enrichment of air with oxygen increases the value of the upper flammable limit, but it does not appreciably affect the lower flammable limit. Flammable limits in pure oxygen have been determined for many common materials (Fig. 21.5). Dilution of the air with nitrogen, carbon dioxide, or other inert gas 10 20 30 40 50 60 70 80 90 100 110 Per cent oxygen in supporting atmosphere (oxygen and nitrogen) FIG. 21.5. Limits of flammability of hexane in oxygen--nitrogen atmospheres. 340 Safety and Accident Prevention in Chemical Operations serves to decrease the upper flammable limit. If sufficient diluent ' added, no flammable zone exists, since insufficient oxygen is present to support combustion. Flash Point and Fire Point Flash point is the minimum liquid temperature at which a flame can be propagated across the surface of the liquid when a standard ignition source is applied. The liquid does not continue to bum at the flash point but, if the liquid is further heated, a temperature win be reached at which the liquid flashes and continues to burn. This is the fire point, and it will be 30 to 50F higher than the flash point Fire point is sometimes confused with ignition temperature but there is no direct relationship between the two. Detection of Flammable Vapors and Gases Accurate, reliable detection of flammables in the air is vital to the prevention of fire or explosion. Simple, inexpensive instruments are readily available but judgment and experience are needed for proper interpretation of tests.14 The "hot wire" type of meter is the oldest and most commonly used. The wiring diagram of a battery-powered portable unit is shown in Fig. 21.6. The sample passes over the heated test coil (but not the heated reference coil). Combustibles burn on the incandescent wire and raise its temperature, therefore its resistance, and the imbalance of the Wheatstone bridge is read on the meter. The usual instrument is calibrated to read the percentage of the lower flammable limit of a calibration substance such as hexane. A more sensitive device operating on the same principle has an additional range reading 1000 ppm full scale. In a vapor concentration less than LEL the needle will be on the scale. In a vapor concentration between the LEL and the UEL the needle will remain off scale above 100%. At concentrations above the UEL the needle will swing rapidly off scale and then drop back to zero. Atmospheres deficient in oxygen result in unreliable low read ings. These vagaries emphasize the need for skill in manipulation and interpretation. Such tests usually precede evaluation for "hot" work and issuance of a permit. Similar instruments are designed for continuous sampling and may be set to sound an alarm at any desired percentage of LEL. One to sixteen points may be sampled by a single device. ETC 03369 Safe Handling of Flammable Materials 341 FIG. 21.6. Simplified wiring diagram--hot wire flammable gas detection instru ment. Other principles used to detect the presence of flammables are: thermal conductivity, diffusion rate, specific gravity, and infrared spectrum. While such instruments are relatively new they are find ing acceptance for solving special problems. 21.5. CODES, REGULATIONS, AND INFORMATION Federal, state, and local government agencies have sought to pro tect the public by enacting laws and issuing regulations setting forth minimum requirements for shipping and storage of flammables. Federal and state labeling laws require warnings on packages of hazardous material but do not apply to those handled in bulk. How ever, laws or regulations, no matter how well written or enforced, can not achieve an adequate level of industrial safety. Informed and in- IM s. 342 Safety and Accident Prevention in Chemical Operations terested management with the aid of a competent safety staff can institute and enforce an effective program. A basic knowledge of factors relating to flammability and kindred phenomena is essential to an effective fire prevention program. Vol untary adherence to recognized cooperative standards has proven ef fective in reducing loss from accidents involving flammables. The National Fire Protection Association, by utilizing the services of hundreds of experts on its committees, has published dozens of codes covering all facets of this subject. Similar information is pub lished by the National Board of Fire Underwriters, Factory Mutuals American Standards Association, Underwriters' Laboratories, and many other organizations. Much of the research and testing of flammable materials has been carried out by the United States Bureau of Mines and published in its reports. The National Academy of Sciences in its Fire Research Abstracts15 publishes information on new studies and data. Shipment of flammable liquids is regulated by the Interstate Com merce Commission as set forth in Tariff No. 15 by T. C. George.111 Approved containers and tank vehicles are listed and placard re quirements are spelled out. Local jurisdictions such as the Port of New York Authority regulate the movement of flammables as well as corrosive and explosive materials through tunnels, over bridges, over turnpikes, and through towns. Shippers should make sure the proper route is chosen to avoid delays. Municipal and suburban volunteer fire fighters are concerned over the burgeoning truck transportation of chemicals. Too often the fire service called to a truck accident, spill, or fire must act with little or no information as to contents and properties. Enlightened chemical manufacturers are beginning to teach and train these men to enable them to avoid exposures and work more effectively. The Chem-Card program developed by the Manufacturing Chemists' Association is a step in this direction. Prevention of Ignition Whenever a flammable liquid or gas is being transferred from one vessel to another, the two should be electrically bonded in order to equalize electrostatic potential and prevent a static spark. Perma nently affixed or temporary bonding lines may be provided to establish the metal-to-metal connection. Clamps or clips must be applied care fully to be sure that paint, scale, and corrosion are penetrated and ETC 03371 Safe Handling of Flammable Materials 343 contact is made with bare metal. Pumps, mixers, process vessels, tanks, and drum racks should be adequately grounded to drain off stray electrical currents. Pipe systems are unreliable as conductors unless all joints are welded, soldered, or jumpered. NFPA 70,17 the National Electrical Code requires that all electrical equipment and wiring conform to Class I, Group D requirements where flammable gases or vapors may be present at any time. See Chapter 6. Explosion-proof equipment is designed with physically strong cases and vents so that an internal explosion would not rupture the case and the flame would be effectively quenched in the vents. Wiring in hazardous areas is enclosed in conduit, and seals prevent passage of gas or vapor into operating cases. The Underwriters' Laboratory publishes periodic lists of electrical equipment tested and approved for hazardous exposures. Certain relaxation is permitted where the flammable is in a closed system and vapors would be released only in extraordinary circum stances. Even in this Division 2 area, sparking devices are prohibited except in approved enclosures. Intrinsically safe electrical equipment has been suggested for certain uses,18 particularly for instruments. These have not been approved by the codes but as their development expands, code consideration is inevitable. Purged or inerted instru ments and cases offer economies when justified by an adequate engi neering study. Equipment in which flammables are to be utilized must be located with careful consideration for geographical relationship to ignition sources and possible vapor pockets. Vapors of nearly all flammable liquids are appreciably heavier than air (methanol, the outstanding exception). In still air, vapor tends to hug the ground and can travel considerable distances on the level or downhill, reach an ignition source, and flash back to the origin as a sheet of flame. Collection of vapors in a low place has been illustrated dramatically by the ac cidental breaking of an electric light bulb in a service-station lubrica tion pit. Dikes built around- tanks to prevent spread of a liquid spill can retain a blanket of flammable (or toxic) vapor. The Flammable Liquid Code, NFPA 30,19 specifies the minimum distances for tanks of various sizes from property lines, roadways, and other tanks. Minimum vent diameters are specified to prevent over pressure under the worst fire exposure conditions. Floating roof tanks, widely used in the petroleum industry, have the advantage of eliminating vapor space above the fluid--important when vaporliquid equilibrium results in flammable mixtures at ambient tem 344 Safety and Accident Prevention in Chemical Operations peratures. Tanks having free space above the liquid should be fitted with conservation vents and flame arrestors to prevent ignition of the vapor mixture. Emergency Action While flammables are often handled in closed systems, spills can and do occur. Open dumping of drums and similar hazardous practices are still a part of chemical manufacturing. Vapors released from such planned or unplanned operations can spread for considerable distances and blanket large areas with unseen flammable vapors. Operating error, process abnormality, equipment failure, or faulty maintenance are some of the causes of the release or spill of substantial quantities of flammable materials. Whether such a release results in a disastrous fire or explosion depends upon many factors, few of which can be controlled once the emergency exists. Location of the release, temperature conditions, wind direction and velocity, slope of the ground, proximity of furnaces or welding operations, as well as properties of the material released, influence the probability of igni tion. Fires involving flammable materials take a heavy toll of both lives and property, are often quite spectacular, are frequently difficult to approach and extinguish, and too often lead to financial collapse of the owners. There are three steps to follow in case of an emergency release of flammable liquid or vapor: (1) immediately shut down all flames and sparking equipment in the area, particularly downhill and to leeward, (2) shut off the source as quickly as possible, and (3) vacate personnel from the affected area. Supplementary steps are: (4) get meters and technicians to monitor the area, (5) call the fire department for stand-by coverage, (6) mobilize guards or police to barricade the area and reroute all traffic. When tests show that little vapor remains undispersed, repairs may be made and fires relighted. Fighting Flammable Liquid Fires While fire fighting is covered in Chapter 28 it is well to consider a few points concerning flammable liquid fires and their extinguish ment. It is important to keep equipment, especially supporting struc tures and tanks, cooled by water streams if extinguishment is likely to be time consuming. Carbon dioxide and dry chemical extinguishers are effective on nearly all flammable liquid fires of limited scope. Steam may be used ETC 03373 Safe Handling of Flammable Materials 34S on smaller fires and water fog on some larger ones. Foam, either chemical or mechanical type, is the workhorse for larger flammable liquid fires. Polar compounds such as alcohols, ketones, and ethers require a special foam compound which must be applied with utmost skill and care. Horizontal tanks, whether stationary or mobile, present an un usual hazard when they are involved in a fire. When these tanks rupture, because of inadequate relief of internal pressure, the failure almost invariably occurs at the ends. Fire fighters who value their lives will approach such vessels for cooling and extinguishment from the sides, not the ends. Summary Recognizing the ever present danger with flammable materials, anyone involved with their handling should: Know the hazardous properties of the flammable material involved in the operation. Store and transfer safely in a closed system if possible. Avoid (or control) ignition sources in areas containing flammables. Plan and rehearse emergency action. In case of vapor release prevent ignition if possible. Evacuate and monitor the area. Remember the fire triangle. Air is usually present. Keep flammables from contacting an ignition source. REFERENCES 1. Standard Method of Test for Flash Point by Tag Closed Cup Tester, ASTM D 56-61, American Society for Testing and Materials, 1916 Race Street, Phila delphia, Pa. 2. Standard Method of Test for Flash Point by Pensky-Martens Closed Tester, ASTM D 93-62, American Society for Testing Materials, Philadelphia, Pa. 3. Standard Method of Test for Flash and Fire Points by Cleveland Open Cup, ASTM D 92-57, American Society for Testing and Materials, Philadelphia, Pa. 4. Flammable and Combustible Liquids Code, NFPA No. 30-1963, National Fire Protection Association, 60 Batterymarch Street, Boston, Mass. 5. Standard Method of Test for Vapor Pressure of Petroleum Products (Reid Method), ASTM D 323-58, American Society for Testing and Materials, Phila delphia, Pa. 6. Standard for the Prevention of Dust Explosions in the Plastics Industry, NFPA No. 654-1963, National Fire Protection Association, Boston, Mass. 7. Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids, NFPA No. 325-1960, National Fire Protection Association, Boston, Mass. 346 Safety and Accident Prevention in Chemical Operations 8. R. W. Van Dolah, M. G. Zabetakis, D. S. Burgess, and G. S. Scott, Review of Fire and Explosion Hazards of Flight Vehicle Combustibles, Bureau of Mines Information Circular 8137 (1963), p. 7. 9. H. W. Husa and E. Runes, "How Hazardous are Hot Metal Surfaces?" Oil and Gas Journal, 61, 45 (November 11, 1963), pp. 180-182. 10. Van Dolah, Zabetakis, Burgess, and Scott, op. cit., p. 5. 11. A. Klinkenberg and J. L. van der Minne, Electrostatics in the Petroleum In. dustry, Elsevier (1958). 12. H. F. Coward and G. W. Jones, Limits of Flammability of Gases and Vapors Bureau of Mines Bulletin 503, 1952. 13. Van Dolah, Zabetakis, Burgess, and Scott, op. cit., p. 13. 14. R. L. Swift, "Detection of Hazardous Atmospheres," NFPA Quarterly, 57(2) (October, 1963), pp. 168-176. 15. Fire Research Abstracts and Reviews, published at intervals by National Acad emy of Sciences, National Research Council, 2101 Constitution Avenue, Wash ington, D. C. 16. T. C. George, Tariff No. 15 (1963) Interstate Commerce Commission Regula tions for the Transportation oj Explosives and Other Dangerous Articles in Rail Freight Service and by Motor Vehicle (Highway) and Water, Bureau of Explosives, Association of American Railroads, New York. 17. National Electrical Code, NFPA No. 70-1962, pp. 314-375, National Fire Pro tection Association, Boston, Mass. 18. D. H. Barlow, "Intrinsic Safety, Its Growing Status in Europe," Control Engi neering, 10 (March, 1963) pp. 85-88. 19. Flammable and Combustible Liquids Code, NFPA No. 30-1963, p. 19 and 22, National Fire Protection Association, Boston, Mass. ETC 03375 Radiation--Controllable Energy H. H. Fawcett Radiation is the process of emission, transmission, and absorption of energy. Radiation is of several types. Some radiation, such as radio waves and television waves, as well as visible light rays, are part of our daily life, and are called nonionizing radiation. Other types, such as X-rays and gamma rays, are not obvious to us under normal circumstances and are called ionizing radiation, because of their ability to react with matter to release electrons. The wide area covered by the electromagnetic spectrum is noted in Table 22.1. The properties and physiological effects of radio frequency and microwave radiations have been well summarized elsewhere.1'2'3'4 Light, including ultraviolet and infrared, is well documented.5'67 Laser beams have recently introduced unique problems because of coherent monochromatic nature of the light emitted.8,9-10,11 The purpose of this chapter is to survey briefly the shorter wave lengths and particles, usually referred to as ionizing radiation, and to supply references for a more complete study. Ionizing radiation has been in the environment since the formation of the earth,12 but man has only recently learned of its potential for beneficial use. See Table 22.2. Centuries ago we learned to control and reap benefits from fire. More recently, we have learned to control ionizing radiation and to benefit from its availability and use. From a practical viewpoint, radiation is used only if the unique properties present methods for ETC 03376 348 Safety and Accident Prevention in Chemical Operations TABLE 22.1. The Electromagnetic Spectrum* Type of Wave Wavelength Radio, Standard AM and international bands Shortwave, Television channels, 2-13, and FM Ultrashortwave and TV channels 14r-83 Microwave (radar) Infrared Far Intermediate Near Visible light Red Orange Yellow Green Blue Violet Ultraviolet Near Middle Extreme X-rays Superficial Therapy Diagnostic Therapeutic Gamma rays Cosmic rays 500/t to 10/t 10/x to 1.3/i 1.3/i to 7700 A 7700 A to 6300 A 6300 A to 5900 A 5900 A to 5500 A 5500 A to 4900 A 4900 A to 4500 A 4500 A to 3900 A 3900 A to 3000 A 3000 A to 2000 A 2000 A to 100 A 5 A to 0.9 A 0.9 A to 0.1 A 0.1 A to 0.3 A 100 km to 10 meters 10 meters to 1 meter 1 meter to 10 cm 10 cm to 0.5 mm 0.5 mm to 7700 ang- stroms (A) 7700 A to 3900 A 3900 A to 100 A 100 A to 0.1 A 1 A to 0.001 A 0.1 A to 0.0001 A * Band separation is not clearcut and overlap occurs. Source: Journal oj the American Medical Association, Vol. 187, No. 11, page 846, March 14, 1964. "The Biological Effects of Laser Radiation," by M. S. Litwin and D. H. Glew. more efficient or more refined techniques. Understanding and ap preciation of its benefits for many uses,13 mundane (as in locating leaks in underground piping) to exotic (as in nuclear power sources to supply energy to space vehicles) will doubtlessly encourage wider interests and applications. Atomic power from nuclear reactors is already economically attractive; power from thermonuclear fusion has been demonstrated publicly.14 Radiation--Controllable Energy 349 YABLE 22.2. Body Tissue Dose Rates Due to External and Internal Irradiation from Natural Sources of Radiation in "Normal Regions"* Dose rates in mrem/year Source of Irradiation Gonad Haversian canal Bone marrow External irradiation Cosmic rays (including neutrons) Terrestrial radiation (including air) Internal irradiation: K-to Ra226 and decay products (35% equilibrium) Ra228 and decay products (equi librium) Pb210 and decay products! (50% equilibrium) Cu Rn22 (absorbed into bloodstream) Total 50 50 20 0.5 0.8 0.3 0.7 3 125 50 50 15 5.4 8.6 3.6 1.6 3 137 50 50 15 0.6 1.0 0.4 1.6 3 122 * UN (1962). fPb210 in excess of that expected from Ra226 and decay products in 35% equilibrium. Source: Environmental Radioactivity, by M. Eisenbud, McGraw-Hill Book Co., New York, page 170. For definition of units of radiation, see Section 22.2, pages 354-356. 22.1. RADIATION SOURCES Ionizing radiation sources may be broadly classed as nuclear sources and electronic (or machine) sources. Principal Forms of Ionizing Radiation. All are particles of matter with the exception of X-rays and gamma rays, which are electromag netic waves. The deuteron consists of a proton and a neutron; the alpha particle, of two protons and two neutrons. Some of the mass of the constituents of deuterons and alpha particles are transformed into the energy' which binds them together. 350 Safety and Accident Prevention in Chemical Operations This table lists the Principal Sources of Ionizing Radiation.1' Nuclear Sources nuclear reactor gaseous-fission products spent-fuel rods liquid-reactor fuel fission products (solutions or separated, such as Cs 137 and Sr 90) natural radiation sources (such as Ra, Th, U) man-made radioactive isotopes (such as Co 60) Electronic Sources high-voitagetransformer impulse generator (capacitron) Van de Graaff generator resonant transformer linear accelerator betatron cyclotron bevatron other particle accelerators Table 22.3 summarizes the properties of principal forms of radiation TABLE 22.3. Properties of Radiation Ionizing Radiation Electron Symbol 0 Mass 1 Charge - Proton Neutron 1,836 0 1,839 + O Deuteron o 3,671 + Alpha particle X-ray or gamma ray % ------------ -- 7,296 0 ++ 0 Source: Scientific American, 201, p. 76 (1959) Properties of Radioactive Sources The most widely used sources of radiation are radioactive isotopes. Isotopes are forms of elements which have identical chemical proper ties, but because of the different number of neutrons in their nucleus, they have different atomic weight. Many isotopes are not . radio active. Eighty of the 103 known elements have at least 1 stable isotope; some have as many as nine. A total of 280 stable isotopes has been discovered. Sixty-six naturally occurring radioactive iso topes (or species) have been identified.16 Over a thousand known TABLE 22.4. Available Radioisotopes Listed According to Half-Life Half-Life * Radioisotopes** ' 24.2 s Silver-110 30 s Rhodium-106 (Ru106) 72 s Indium-114 2.6 m Barium-137m (Cs13T) 17.5 m Praseodymium-144 12.47 h Potassium-42 12.5 h Iodine-130 12.82 h Copper-64 13.6 h Palladium-109 14.2 h Gallium-72 15.05 h Sodium-24 19.0 h Iridium-194 19.2 h Praseodymium-142 24.0 h Mercurv-197m2 24.0 h Tungsten-187 26.8 h Arsenic-76 35.55 h Bromine-82 38.7 h Arsenic-77 40.3 h Lanthanum-140 46.8 h 21l6S43..45hh Samarium-153 Cadmium-115 Yttrium-90 64.8 h Gold-198 65 h Mercury-197 66 h Antimony-122 67 h Molybdenum-99 75.4 h Gold-199 88.9 h Rhenium-186 1 4.53 d Calcium-47 5.00 d Bismuth-210 5.27 d Xenon-133 7.5 d Silver-111 [ 8.05 d Iodine-131 11.06 d Neodymium-147 4^ 12.0 d 12.8 d Barium-131 Barium-140 13.7 d Praseodymium-143 14.3 d Phosphorus-32 16 d Osmium-191 18.68 d Rubidium-86 27.8 d Chromium-51 32.5 d Cerium-141 34.3 d Argon-37 35 d Niobium-95 39.7 d Ruthenium-103 Radiation 0,7 0,7 EC,0 ,0+,7 IT,7 0,7 0,7 0,7 EC,0 ,0+,7 &Y fry 0,7 0.7 0,7 EC,IT,7 0,7 0,7 0,7 0,7 0,7 0,7 0,7 0 0,7 EC,7 0,7 0,7 0.7 EC,0,7 0,7 0 0.7 0.7 0.7 0,7 EC,7 0,7 0 0 0,7 0,7 EC,7 0,7 EC 0,7 0,7 Half-Life* Radioisotopes* 43 d 44.3 d 44.6 d 45.4 d 50 d 50.5 d 57.4 d 59.1 d 60.9 d 64 d 65 d 71.3 d . 74.2 d 75.8 d 84.2 d 89 d 115.1 d 119 d 119.9 d 129 d 165.1 d 246.4 d 249 d 285 d 371 y 1.3 y 2.07 y 2.5 y 2.78 y 2.94 y 3.57 y 5.24 y 10.27 y 10.7 y 12.46 y 12.7 y 16 y 28 y 30 y 125 y 5.57 x 103 y 2.12 x 105 y 3.08 x 106 y 1.56 x 107 y Cadmium-115m Iron-59 Hafnium-181 Mercury-203 Indium-114m Strontium-89 Iodine-125 Yttrium-91 Antimony-124 Strontium-85 Zirconium-95 Cobalt-58 Iridium-192 Tungsten-185 Scandium-46 Sulfur-35 Tantalum-182 Tin-113 Selenium-75 Thulium-170 Calcium-45 Zinc-65 Silver-110m Cerium-144 Ruthenium-106 Cadmium-109 Cesium-134 Promethium-147 Antimony-125 Iron-55 Thallium-204 Cobalt-60 Krypton-85 Barium-133 Hydrogen-3 Europium-152 Europium-154 Strontium-90 Cesium-137 Nickel-63 Carbon-14 Technetium-99 Chlorine-36 Iodine-129 Radiation 0,r 0,7 0,7 0,7 IT,7 0 7 0,7 0,7 7 0,7 ec^-,7 0 ECj3,7 0,7 0 0,7 EC,7 EC,7 0,7 0 EC,0+7 IT,0,7 0,7 0 EC,7 0,7 0,7 0 EC EC,0 0,7 0,7 EC,7 0 EC,0,7 0,7 0 0 0 0 0 0 0,7 * s, second; m. minute; h, hour; d, day; y, year. ** The radioisotope in parenthesis is the one under which the listed radioisotope is cataloged. DECAY ALLOWANCE Decay Allowance for isotopes with halflives of less than 15 days is shown by brackets in half-life column. Allowance calculated from 8 a.m. on day of shipment. 1-- 2-- 3-- 4-- One Half-Life One Day Two Days Four Days Suppliers of radioisotopes include: Oak Ridge National Laboratory, Isotopes Division. P. O. Box X. Oak Ridge, Tennessee. General Electric Co., Vallecitos Atomic Laboratory, P. O. Box 840, Pleasanton, California. nsntfir i,i enV 352 Safely and Accident Prevention in Chemical Operations radioactive iosotopes (also called radionuclides) have been produced artificially. Of these, nearly one hundred radioactive isotopes are commercially available from several sources in the United States and Canada. Radioactive isotopes (or radionuclides) tend to become stable as they give off radiation, much as a mechanical clock tends to "run down" as the energy in the spring is expended. The time required in radioactive materials for half of the atoms to emit their radiation is called the half-life. Each radioactive isotope has its own unique half-life, which may be from a fraction of a second to billions of years (Fig. 22.1). During this decay, radioactive isotopes emit one or more forms of energy. These include: 1. Alpha particles (mass number 4, charge plus 2), which are helium nuclei evolved from decay of elements of high atomic number, such as thorium, radium, polonium, and plutonium. As decay occurs, the parent alpha-emitting element acquires an atomic number of two less and a mass number of four less than the parent. Because of their relatively large mass, alpha particles have relatively little penetra tion power. As a practical matter, paper will stop alpha particles, and even the most energetic alphas are attenuated or dissipated by less than 3 in. of air or 0.002 cm of aluminum. Alpha emitters are not without potential hazard, however. While they pose little hazard from an external radiation standpoint, they do present serious prob lems as internal radiation sources, and this, together with the long ETC 03381 Radiation--Controllable Energy 353 half-life and intrinsic toxicity of the metals themselves, make it mandatory to prevent the possible entrance into the body by inges tion, inhalation, or other routes. 2. Beta rays (or particles) are electrons. They are the only nega tively charged ionized particles of direct interest in the study of radia tion effects. Since their mass is very small, they can penetrate deeper than alpha particles can penetrate. The electron acts an an ionizing particle when liberated from the atom, either by particulate or elec tromagnetic- radiation. The energy of the electron determines the amount of secondary ionization, which greatly contributes to the total ionization or damage occurring in any cell. Ionizing particles have almost two-thirds of their energy carried away and distributed throughout the environment by these secondary electrons. The relative energy of the electron has a significant effect on the shielding required to protect personnel who may be in the area. Glass, plastic, and aluminum are often used for shielding of betas or electrons, but glass and many plastics discolor and become brittle in high-radiation fields. With low-energy electrons, iron, copper, con crete, or concrete blocks are used as shields. The beams of high-energy radiation, such as fast electrons from accelerating machines, have found application including the modification of polymers to improve physical properties, such as tensile strength, food preservation, drug sterilization, and other uses. Typical electron accelerators include the Van de Graaffs, producing electrons of 1 to 6 mev (million electron volts, or mev, is a measure of the energy of a particle or wave); reso nant transformers producing 1 to 3.5 mev electrons; betatrons pro ducing 6 to 30 mev electrons; and linear accelerators yielding 3 to 25 or higher mev electrons. Both low-voltage electrons, also called cathode rays, and high-energy electrons, may be emitted by a heated filament (cathode) in a vacuum tube. 3. Gamma (and X-) rays are electromagnetic radiations analogous to light but of shorter wavelength. They differ from each other fundamentally only in their frequency (wavelength) and in their source. X-rays are frequently called Roentgen rays in honor of their discoverer, Professor W. Roentgen. Both X-rays (usually supplied by a machine employing a tube, such as the Coolidge tube) and gamma rays (usually from a radioactive isotope or radionuclide, such as Cobalt 60) may be used for clinical radiotherapy in humans, for radiography in the inspection of welds or flaws in pipes, vessels, and other metallic forms, or for many other uses since it is the charac teristic of the ray which gives it utility. In deciding whether to use a machine-produced or radioactive source-produced ray, such factors 354 Safety and Occident Prevention in Chemical Operations as convenience, cost, ease of control, absoluteness of control, and precision of manipulation are often considered. Neutrons are not emitted directly from radioactive isotopes, but they are essential to the production of most radioactive isotopes. One theory considers them the fundamental building blocks of all elements. Neutrons are electrically neutral, have very high penetrat ing power, and exhibit no electric interactions. Nuclear reactors are the most practical peacetime source of neutrons. By their ability to convert or transmute other elements by entering their nucleus (a process known as neutron capture), neutrons produce most of the man-made radioactive isotopes (or radionuclides) from stable atoms introduced into the reactor. The flux inside one reactor has been estimated to be a mixture of: Thermal neutrons Neutrons (>0.1 mev) Neutrons (>0.5 mev) Fast neutrons (> 1 mev) Gamma-photons (av. 1 mev) 1.1 X 1012/cm2 sec 1.4 X 1011 6.7 X 1010 4.2 X 1010 ~5 X 1011 The General Electric Test Reactor has peak flux as follows: core position 3 X 1014 nv thermal, and 6 X 1014 nv fast pool position 1 X 1014 nv thermal, and 3 X 1013 nv fast 22.2. UNITS OF RADIATION For radiation sources, the fundamental unit of activity is the curie, named for Madame Curie. The curie is that amount of any radio active material in which 3.700 X 1010 nuclear disintegrations occur per second. The millicurie (me) is one-thousandth curie; the kilocurie (kc) is one thousand curies. Many experiments or operations are per formed using less than a millicurie of a radioactive isotope. Sources of one to several kilocuries are used routinely for medical therapy, while food sterilization may require several hundred kilocuries. Stronger sources require the most meticulous care to prevent excessive exposures. Preplanning of a facility, careful selection and use of equip ment, standardized procedures, and adequate education and training of personnel are important aspects of a radiation program, especially where large sources are involved. The effect of radiation exposure depends upon the quantity of radia tion, the type and amount of interaction of the radiation with matter, Radiation--Controllable Energy 355 and on biological differences. A unit, the roentgen, has been estab lished which defines the ionization effect in air by X-rays or gamma rays. It is defined as the quantity of X- or gamma radiation such that the associated corpuscular emission per cubic centimeter or 0.001293 g of air produces, in air, ions carrying one electrostatic unit (esu) quan tity of electricity of either sign. One roentgen or X- or gamma radia tion will result with the absorption of about 87 ergs of energy per gram of air. (The associated corpuscular emission referred to in the defini tion are electrons produced by the interaction of X- or gamma rays with air. All ion pairs produced are considered if we wish to account for the entire amount of energy.) Because it is defined in terms of air and refers to X- or gamma radiation, the roentgen must be con verted to more useful units to be practical. For X-rays used in radia tion therapy and for soft tissue, 1 roentgen yields an energy transfer of about 97 ergs/g of soft tissue. The energy per gram for other types of radiation and for other materials will differ significantly. Since it is the actual energy transferred to and reaction with tissue or materials which produce effects, the "rad" was developed as a unit of absorbed dose. The rad represents the absorption of 100 ergs of nuclear (or ionizing) radiation per gram of the absorbing material or tissue. It is a valid unit of radiation dose for any type or energy of radiation and for any material with which the radiation interacts. Equally absorbed doses produced by different types or different en ergies of radiation produce different biological effects. The quality of the radiation, the intensity or rate of delivery, and continuous versus fractionated administration have been identified as important vari ables. These differences have led to the concept of relative biological effectiveness, or RBE, in which various ratios have been established for the relative effectiveness of various types of radiation. These include: Radiation X-rays, gamma rays, electrons, beta rays, and nuclear weapon neutrons Fast neutrons and protons up to 10 mev Thermal neutrons Heavy recoil nuclei Naturailv occurring alpha particles (from Ra, Po, Th, U) RBE or rads rems 11 1 10 . 1 4 to 5 1 20 1 10 to 20 By incorporating these RBE ratios into the previous definition of a rad, the "rem" has been evolved as an indication of the extent of the 356 Safety and Accident Prevention in Chemical Operations biological injury (of a specific type) which results from absorption of nuclear radiation, and is calculated by the formula: dose in rems = RBE X dose in rads The rem is a dose unit of biological effect, whereas the rad is a unit of absorbed energy dose, and the roentgen (for X- and gamma rays) is a unit of ex-posure or total dose. Another term, linear energy trans fer (or LET) is the energy released by the radiation per unit length of the absorbing tissue. Measuring Radiation Since radiation can not be observed with the normal physical senses measurement is a prime prerequisite of radiation control.17'ls-19 awareness of why radiation must be measured is essential for safe use. Important reasons for radiation measurements and records include: 1. To maintain a cumulative record of exposure to radiation of every individual exposed. (This has become increasingly important, both legally, and^because of the interest in cradle-to-senior citizen docu mentation of the medical aspects of each individual.) 2. To measure over a short period the exposure of individuals carrying out specific operations during which the radiation level is abnor mally high. For example, if a source is manually moved or physically transferred from a shielded storage location to a work station, or a radioactive isotope solution is removed from its shipping container and checked for identity and activity, a certain exposure is practically unpreventable, but it can usually be kept within recognized limits as repairable by the body. Measurements are essential to control such exposures. 3. To survey the flux or radiation level in all parts of the facility to detect areas of unnecessarily high radiation levels. For example, a bottle or drum of radioactive waste solution may have been tem porarily stored with other chemicals under circumstances in viola tion of standard operations and procedures. Prompt discovery of this error by survey aids in restoring proper control. 4. To locate radioactive contamination on the benches, floors, and other surfaces, or, when necessary, in the air. Spills will occasionally occur, even in the meticulous operations, and unless careful surveys and clean-up (often referred to as decontamination) are instituted promptly and effectively, radiation can spread and eventually result in unnecessary exposure to a wide area and involve other personnel. Radiation--Controllable Energy 357 5, To monitor contamination on hands, feet, hair, skin, or clothing of personnel who are working with or have contact with radioactive materials. (In large operations where this is a part of normal daily routine, special instrumentation may be available for self monitoring of feet, hands, and body, located in a locker or wash room area; in smaller operations, a readily available survey meter may suffice. For removal of radioactive material from the skin, special cleaners are available which combine chelating agents with surface-active detergents. Shower, facilities or other methods of thorough washing of the whole body, including the hair, should be readily available for emergency decontamination and medical control of chemicals and radioactive materials, even if showers are not used routinely.) 6. To establish legal protection for the employers and employees, in compliance with local, state, and federal codes and other laws con trolling radiation. Radiation surveys and services are not glamorous occupations. However, they do require the same type of intelligence, patience, time, initiative, and a degree of dedication, as other accident prevention work. The seriousness, the moral and legal responsibility of the posi tion, and the accountability must be fully appreciated if the job is to be done properly on the required routine basis. Radiation Instrumentation Film Badges. Photographic film of the proper type when processed will respond to radiation much as it does to visible light, and this fundamental fact is the basis for the film badge dosimetry--the device of choice by many individuals for measuring and subsequent record ing of accumulated radiation exposure. Low cost, convenient size, capability for integrating doses over relatively long periods of time, and the permanent nature of the record are advantages which are possessed uniquely by film badges. Film badges detect from a mini mum of about 10 mr to hundreds of roentgens of exposure from lowenergy X-rays and beta rays to very high-energy gamma and neutron radiation. Film badges will not detect radiation from alpha particles, since alphas are stopped by the paper necessary to shield film from exposure to light. Film badges consist of small sheets of sensitive photographic or X-ray type film supported by a plastic or metal frame holder. The holder may contain small discs or pieces of metals of different density, 358 Safety and Accident Prevention in Chemical Operations positioned in front of the film to intercept part of the impinging ra diation. Aluminum, copper, silver, cadmium, and lead are frequentl used to aid in discriminating different energy levels and types of ra diation. Normally the badge in its holder is worn on the lapel or shirt pocket, and it is used as an indication of total body exposure. Where fingers and hands may have more direct exposure, as in the use of X-ray diffraction equipment, smaller film badges may be worn on the fingers to measure hand and finger exposures. If the forearm and hands are likely to receive exposures, a film badge may be worn on the wrist or lower arm to indicate exposures to such local areas. Where exposure to neutrons may be encountered, an additional sensi tive film is placed behind the beta-gamma film. Since cadmium has a high cross section for the absorption of slow neutrons, only fast neutrons penetrate the cadmium shield, producing recoil protons which leave tracks in the film, w'hile thermal neutrons leave proton tracks in the areas of the film where no cadmium shields the neutrons. Slow neutrons, faster than thermal but slower than 0.5 mev, will not leave tracks. On the developed films, the tracks are counted using a micro scope. Badges are usually worn for a week or 10 days and are returned to the service supplier for processing and reporting of results. Since a few days normally lapse between returning the badges and receipt of the exposure report, emergency processing and reporting service should be available on a 24-hr basis, so any badge may be immediately processed when received, and the results telephoned or telegraphed to aid in determining whether an unusual exposure has actually occurred. This is important both clinically and legally, since high exposures must be immediately reported to medical and regulatory agencies. In ad dition to regular reports listing all badges used during the period, sep arate reports for each individual may also be obtained, showing totals for the previous period, for the past quarter year (or thirteen weeks), and for the total accumulated exposure for the individual since the in ception of the badge service.20 Although badges do not give immediate information and are not self-reading, they represent an excellent ra diation control device, if they are supplied, processed, and reported by a reputable service. Quality of control in processing and reporting is of extreme importance to insure accuracy of results and records. A new approach to analysis of minute concentrations of uranium uses tracks from fission particles in solid state media.21 See Fig. 22.2. Ionization Chambers. Ionization of air or other gases by radiation provides a method of measurement based on the movement of electrons i ETC 03387 Radiation--Controllable Energy 359 I FIG. 22.2. "Fossil" particle tracks produced in minerals by uranium atoms which underwent natural fission. Courtesy General Electric Research Laboratory. from one part of the wall to an electrically charged plate or post. Since a single alpha particle from radium, for example, produces 137,000 positive ions and an equal number of electrons when it is completely absorbed in air, the consequent electric current can be measured with the aid of an amplifier. The ions formed in a gas (ions of nitrogen and oxygen molecules in the case of air) are usually exceedingly reactive; they often undergo chemical change during the time required to collect them at an electrode. The total electric charge, however, is not thereby altered. For this and numerous other reasons the ionization method of detection has proved remarkably trustworthy. Ionization chambers are widely employed to count energetic particles and to determine their individual energies. If the instrument is properly designed, with thin walls and high sensitivity, beta rays as well as X-rays and gamma rays may be measured. The ionization effect is used for personnel monitoring in small, pocket ionization chambers, which are devices about the size and shape of a fountain pen. When charging the device initially with an aux iliary charger to a known potential, such as 150 v, the change in the capacitor due to discharge by ionization may be noted by reading the residual charge on a reader device. Another type, not unlike the other in external appearance, is a combined electrostatic ionization chamber and a fiber electroscope. The quartz hair-like fiber is charged with an external battery to read scale zero. As the radiation produces ionization, partial discharge occurs, and the fiber moves across the scale. Its location may be immediately observed by viewing the scale 360 Safety and Accident Prevention in Chemical Operations through the lens built into one end and observing the shadow against a light. Both types discharge as the dose accumulates, and they may be read as frequently as desired. One style, designed for civil defense application, may be used also to indicate rate of exposure by exposing the device for a specified number of minutes, and then interpreting the dose per unit time as a rate (such as roentgens per hour). One disadvantage to the pocket ionization chambers is their rela tively high sensitivity to shock, -which may be inaccurately interpreted as radiation exposure, if the device is accidently dropped. For this reason, pocket ionization chambers are often worn in pairs. For higher levels of radiation, other types of dosimeters are available. Phosphate glass dosimeters measure doses in the range of 10 to 600 r, which is a critical range for determining probable survival of any in dividual exposed to high levels of radiation. (Single doses in the range of 25 to 100 rems over the whole body will produce nothing other than blood changes; doses of 100 to 200 rems will result in a certain amount of illness, but will rarely be fatal; for doses between 200 and 1000 rems the probability of survival is good at the lower end of the range but poor at the upper end.) The special glass contains traces of silver and other metals as activator and, after exposure to radiation, it be comes fluorescent under ultraviolet light.22 Another type, the chem ical dosimeter, utilizes the principle of the color change produced when an acid, such as hydrochloric, is liberated from chloroform or other chlorinated hydrocarbons, in the presence of an organic dye indicator such as methyl red or methyl orange. Indicators of this type may be dissolved in wax or a paraffin, and they are used to study penetration of the radiation by observing the color changes at various depths. The Fricke dosimeter, developed by Hugo Fricke, is based on another chemical reaction, the oxidation of ferrous sulfate dissolved in sulfuric acid, to give an accurate measure of absorbed energy. The principle of ionization, when incorporated into the appropriate electronic circuitry, is used as a dose-rate meter. Available in a wide range of types and incorporating several scales to accommodate various intensities, from less than 1 mr/h to 5 r/h and with a movable shield in some models to permit discrimination between beta and gamma radiation, ionization dose-rate meters are widely used for survey pur poses. Geiger-Mueller Counter. The Geiger-Mueller counter is a count-rate meter, in which a thin-walled tube reacts with radiation to produce electronic pulses w'hich are amplified so they can be displayed on a Radiation--Controllable Energy 361 pjeter and heard on a speaker or earphones. It employs high voltages break down the gas, once a passing particle has supplied an initial requirement of ions. Such a device yields a burst of current strong enough to be observed without amplification. Depending on the type and how the tube is housed and shielded, the Geiger counter can be very specific in pinpointing local radiation areas on contaminated floors 0r benches, or contaminated clothing or skin, especially if a sensitive end-window detector tube is used. Useful for counting large numbers of ionizing particles, the Geiger counter cannot determine their ener gies. Some Geiger-counter scales are calibrated in counts or pulses per minute, while others read milliroentgens per hour. Scintillation Counters. Another method of detection rests on the emis sion of light by excited molecules. When an atom is excited, it must lose its excitation energy and return to its lowest energy state by emitting one or several photons. Since few atoms exist in isolation, the excitation energy is usually dissipated by collisions with other atoms or molecules and diverted to forms of energy such as heat. Although few molecules emit light when irradiated, special substances are avail able in which the excitation energy is not degraded, but they emit light under irradiation. Inorganic phosphors, such as zinc sulfide, and organic substances (usually aromatic polycyclic compounds), serve as scintillating media, and the light is picked up by a sensitive photo cell and amplifier that converts the burst of light into an electrical signal. Alpha Detection and Measurement. Where alpha sources are used, an alpha-detecting instrument is required for check and control. Except for the scintillation counter, the instruments described previously will not perform this service. The typical alpha-detecting instruments have a very thin plastic-covered window which permits the alpha particles to enter the field of a relatively large probe, and the resulting pulse is translated directly into the circuitry, or, by ionization of a gas such as propane (in the gas proportional counter type), it produces second ary effects which then are amplified and indicated on a meter. Such meters read in counts per minute over a wide range, by choice of several scale multipliers, and must be calibrated for the particular alpha en ergy to be surveyed. 22.3. BIOLOGICAL EFFECTS OF RADIATION The biological effects of radiation have been widely publicized in connection with nuclear weapons to the extent that it is difficult to 362 Safety and Accident Prevention in Chemical Operations japproach the subject in the proper scientific manner, because of the high emotional content of much that has been written. The recent i attempts to place radiation into its proper perspective will require j an induction period before knowledge replaces fear in the minds of many. We live in a world in which radiation exists, and it is impossible to avoid some exposure.23 See Fig. 22.3. It is also true that the body can, within certain limits, repair the damage from radiation, whatever its source. At what point excessive or over-exposure to radiation is harmful to individuals depends on many factors. It is known that the different types of ionizing radiation differ greatly in their ability to penetrate the skin and body and in their relative effectiveness, a concept which is expressed in the RBE or relative biological effectiveness previously discussed. The effects of ionization may be direct (localized within the cells directly affected, as a skin exposure), or indirect (since the action on one organ or group of cells, such as the bone marrow, may be trans mitted to other cells remote from the bone by the blood). Effects may be immediate or delayed, depending on intensity, type, and other fac tors characteristic of the radiation involved. The effects may be re versible (repairable by the body through normal repair and replacement processes) or irreversible. i : Certain body cells have been found to be more sensitive to radiation than others.24 In decreasing order of sensitivity to radiation, some of these may be listed: 1. Lymphocytes, or white blood cells formed by the tissues of the spleen and lymph nodes. Because of their sensitivity, complete blood counts at frequent intervals following a suspected exposure to a large area of the body may reflect any serious damage and outline the recovery cycle which may be occurring. Reliable and accurate pre-exposure counts are essential for comparison pur poses, since only by comparisons are such blood counts meaningful. 2. Granulocytes, or white blood cells formed in bone marrow. These are needed in proper ratio to combat bacterial infection. 3. Basal cells, which originate complex and specialized cells of the gonads, bone marrow, skin, and the alimentary canal. 4. Alveolar cells of the lungs, which are essential in oxygen-carbon dioxide exchange of the body. 5. Bile duct cells. 6. Cells of the tubules of the kidneys. 7. Endothelial cells, which line the closed cavities of the body, such as the heart and the blood vessels. ETC 03391 ETC 03392 364 Safety and Accident Prevention in Chemical Operations 8. Connective tissue cells, which are structural cells of the tissue supporting the organs and other specialized tissues of the body 9. Muscle cells. 10. Bone cells. 11. Nerve cells. The relatively short life span which require blood cells to continually-? reproduce may explain the reason for their radiosensitivity. The life J spans for typical blood cells are: Cells Erythrocytes Granulocytes Lymphocytes Platelets Source Bone marrow Bone marrow Lymphatic tissue Bone marrow Life span 17 weeks 3 days 8 to 24 hours 3 to 6 days In considering internal radiation, in which various radioactive mate rials, either naturally occurring or man made, may be inhaled, ingested, or otherwise gain entry into the body, it is interesting to note that cer tain radionuclides or isotopes tend to concentrate in a few vital organs, especially the lungs, kidneys, liver, and bone. This property, coupled with the known biological half life and the excretionary rate (at which the material is known to be eliminated from the body), makes it possible to use monitoring of exhaled breath, urine, and other body wastes as an indication of body burden or total amount of the substance actually in the body. In addition, whole body counters of great sen sitivity have been used to measure the total radiation emitted from the whole body because of internally deposited radioactive materials. Some isotopes known to concentrate in certain body organs include:16 Lungs Kidneys Liver Nickel 63 Chromium 51 Manganese 56 Radon 222 Manganese 56 Nickel 59 Pi Polonium 210 Germanium 71 Cobalt 60 Uranium 238 Arsenic 76 Copper 64 Li Plutonium 239 Rhodium 105 Silver 105 Ruthenium 106 Cadmium 109 Rhodium 106 Silver 109, 111 Technetium 127 Tellurium 129 Iridium 190, 192 Gold 198 Uranium 238 ETC 03393 Radiation--Controllable Energy 365 Bone Beryllium 7 Carbon 14 Fluorine 18 Phosphorus 32 Calcium 45 Vanadium 48 Zinc 65 Gallium 72 Strontium 89 and 90 Yttrium 90 and 91 Niobium 95 Molybdenum 99 Tin 113 Barium 140 Lanthanum 140 Praseodymium 143 and 144 Cerium 144 Bone (cont.) Promethium 147 Samarium 151 Europium 154 Holmium 166 Thulium 170 Lutecium 177 Tungsten 185 Lead 203 Radium 226 Uranium 233 Thorium 234 Plutonium 239 Americium 241 Curium 242 Control of Exposures to Radiation Regardless of the source (nuclear or electronic) or type of ionizing radiation, a few fundamental control measures are appropriate. No unnecessary exposure should be permitted, and the risk of exposure should always be balanced against the importance of the results to be obtained. Every operation or activity involving ionizing radiation should be preplanned, and, if possible, rehearsed with a "dry run" to insure that the desired operation can be accomplished in the minimum amount of time with the least practical exposure. This should not be understood to mean that all exposures should be avoided at all times, but, rather that exposures should be controlled and measured, so they can be kept within the limits which have been established. Obviously, amounts of activity (in the case of nuclear sources) or voltages and times of exposures (in the case of X-ray and other electronic sources) should be kept at a workable minimum. From a practical view, most exposures are controlled by the application of three principles: time, distance, and shielding. Time. Radiation dose is directly related to the time of exposure--this elementary fact is one of the keys to radiation control. For this rea son, every individual action or activity in the radiation field or area should be preplanned so no delays or other complications require un necessarily long exposure. The formula: Exposure dose = rate X time 366 Safety and Accident Prevention in Chemical Operations is fundamental, since time is the easiest factor which an indivi(j controls for himself. Stop-watches, clocks, or calendars thus bee important instruments in the radiation control program, and the ' i portance of time should not be minimized. All other factors equal"! the same total dose is less likely to cause biological damage the Iona '1 the period of time over which it is accumulated. Distance. Next to time, distance is probably the fundamental concept J in radiation control. Radiation follows the same Inverse Square law i as does light, namely, the intensity decreases as the inverse square^ of the distance from the source. A radiation flux or level of unit at a unit distance will be only % unity at twice the distance sii\Cfi 1/22 = 1/4. To illustrate further: if a source has an intensity of 100 mr/hr at 1 ft distance, the corresponding intensity for other distances up to 10 ft may be tabulated: Intensity in mr/hr 100 mr/h 25 mr/h 4 mr/h 1 mr/h distance 1 ft 2 ft 5 ft 10 ft ratio 1 1/4 1/25 1/100 In practice, distance may be used to advantage by remote-handling aids, such as tongs, long-handled wrenches, cranes, and remotely op erated mechanical hands. Viewing aids, such as mirro-s, telescopes, closed-circuit television, and windows made of lealded glass installed so they may be filled with water solutions of heavy-metal salts, permit visibility from a distance without unnecessary complications. Shielding or Filters. Any matter or mass placed between a radiation source or beam and the point of exposure will screen or decrease the exposure to at least some extent. As noted previously, even air pro duces some shielding effect. Whether or not shielding of a particular type is adequate for a given situation depends on specific considera J { tions. The man who, half seriously, planned to construct a fallout shelter from cream puffs so he could eat his way out as the outside radiation level decreased due to the decay of the fallout radiation may have had originality and imagination but little scientific information. If fallout were all alpha activity (which, of course, it is not), if the eating rate matched the decay rate of the alpha, and if the sheltered did not breathe or eat any of the alpha-contaminated air, water, or food, the cream-puff shield might be adequate, just as paper or thin ETC 03395 Radiation^-Controllable Energy 367 aluminum shelters would be. Unfortunately, beta and gamma rays of the energy levels associated with fallout would not be attenuated or stopped to any significant extent by the mass or density of cream puffs. Each type of radiation is most effectively controlled by a particular shielding material. The type and energy must be considered in choos ing the kind and type of shield required to cut levels of radiation down to acceptable limits. Shielding may be constructed of several different materials. Lead and the other heavy metals are excellent shields for radiation, but their cost is high. Concrete mixed with iron ore or heavy mineral aggregate (to increase the density) is effective but expensive and bulky. Poured walls or precast concrete made with iron ore or heavy aggregates in walls and ceilings or solid concrete blocks laid into wall form are the most common shielding materials. The concrete thickness estimated to reduce radiation levels to estab lish limits for personnel near a one-million-volt electron beam generator is 2.5 ft, and, for a generator of 2 million volts, 4 ft. These numbers are estimates, and exact thickness wall depend upon the voltage and kilowattage of the electron-beam generator, size of room, room geom etry, and occupancy of adjacent areas. An alternate scheme is to construct two Walls of timber and planking, filling the space between with poured sand as a barrier. Such a barrier is easily erected and dismantled, and the materials of construction may be reclaimed. How ever, the lower density of the sand as a barrier requires that its thick ness be about 70% greater than the equivalent concrete shielding, thus requiring a greater overall floor area. The suggested floor plan used for facility planning purposes for a 1-mev electron beam unit is shown in Fig. 22.4. A frequently used approach is to locate a machine or source in a pit or depression underground, so that the earth acts as a natural shield on the sides and bottom. Deep pools of water are also used as shielding material if the material is not adversely affected by water. In this connection, it has been reported that the radiation exposure to person nel aboard an atomic-powered submarine when submerged is less than that to a person on land near the same area, because of the shielding of the cosmic and other background radiation by the water. Limits of Exposure Any attempt to outline exposure limits must be predicated with the statement that exposure to radiation should be kept at the lowest 368 Safety and Accident Prevention in Chemical Operations Water cooler on shelf Lead hatch cover 1 mev. head -3Y- 63s* Subterranean pit FIG. 22.4. Plan for installation of a 1-mev electron beam generator. Note use of pit to facilitate shielding. Courtesy X-Ray Department, Gen eral Electric Co. ETC 033 9 7 Radiation--Controllable Energy 369 levels which are practical to achieve necessary results, always balanc ing the benefits to be gained from the exposure with the potential hazards, and recognizing the established limits. As in many other phases of life, the risk and gain should be weighed to achieve an un derstanding for the necessity for the risk. External Dose Limits. The permissible limits for external radiation exposure are: Site of exposure Whole body, head, and trunk, blood-forming organs, gon ads, lens of the eyes, and other organs Skin of the whole body Hands and forearms, feet and ankles Dose for 13 consecutive weeks in rems 3 10 25 * N is the age in years, greater than 18. Accumulated dose 5 (N-18) rems' 30 rems/yr 75 rems/yr Internal Dose. Since the main route of entry of radioactive materials normally is by breathing, the control is to limit the average rates at which materials are breathed. For drinking water and foodstuffs, the permissible concentrations are also recognized. For further information on this subject, the reader is referred to Handbook No. 69, Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure, published by the National Bureau of Standards, United States Depart ment of Commerce, Washington, D.C. Permissible Limits for Nonoccupational Exposure. For external ra diation exposure, the maximum permissible dose for nonoccupational exposure to the whole body, head and trunk, active blood-forming organs, gonads, or lens of the eye should not exceed 0.5 rem in any year. For internal exposure limits, refer to the Handbook No. 69 referred to above. Summary The material presented in this chapter is intended to serve as a beginning, however inadequate, to an understanding of radiation as a controllable hazard. Perhaps more than any other field of sci entific knowledge, even in the scientific community itself, radiation 370 Safety and Accident Prevention in Chemical Operations is inadequately understood and even feared. The plea of Madame Curie is still unanswered in the popular mind: Nothing in life is to be feared; It is only to be understood. The references attached furnish a key to this understanding, and the reader is urged to consult them in detail.25-26 REFERENCES 1. Medical Physics, The Year Book Publishers, Chicago, 111., 1944, pp. 1145_nR4 2. W. W. Mumford, Proc. of the I.RE., Vol. 49, pp. 427^447; Some Technical Aspects of Microwave Radiation Hazards (February, 1961). 3. M. F. Payton, Proceedings of the Fourth Annual Tri-Service Conference on the Biological Effects of Microwave Radiation, Vol. 1, Plenum Press, New York, 1961. 4. G. H. Mickey, "Electromagnetism and Its Effect on the Organism," New York State Journal of Medicine, 63 (July 18, 1963), pp. 1935-1942. 5. Koller, L., Ultraviolet Radiation, Wiley, New York, 1952. 6. P. W. Kruse, L. D. McGlauchlin, and R. B. McQuistan, Elements of Infrared Technology c Generation, Transmission, and Detection, Wiley, New York, 1962 7. S. Duke-Elder, System of Ophthalmology, 7, pp. 759-763, C. V. Mosby Co St. Louis, Mo., 1962. 8. M. Brotherton, Masers and Lasers: How They Work, What They Do, McGraw-Hill, New York (March, 1964). 9. H. E. Tebrock, W. N. Young, and W. Machle, "Laser-Medical and Industrial Hygiene Controls," Journal of Occupational Medicine, 5 (December, 1963) pp. 564-567. 10. M. S. Litwin, and D. H. Glew, "The Biological Effects of Laser Radiation," JAMA 187, 11 (March 14, 1964), pp. 842-847. 11. "Laser Seen as a Potentially Useful Tool, but Scientists Hear Warnings of Hazards," JAMA 188 (June 15, 1964), p. 35. 12. M. Eisenbud, Environmental Radioactivity, McGraw-Hill, New York, 1963. 13. W. W. Schultz, and R. S. Rocklin, Radioisotopes in Industry, Reinhold Pilot Book, New York, 1959. 14. Research Laboratory Bulletin, Special Issue on Nuclear Fusion, GP-0288A, Research Laboratory, General Electric Co., Schenectady, New York (Summer, 1964). 15. A. Charlesby, Atomic Radiation and Polymers, Typical Radiation Sources and Their Intensity, 1960, p. 53. 16. D. T. Goldman, Chart of the Nuclides, APH 66F, Educational Relations, De partment MWH, General Electric Co., Schenectady, New York (December, 1962). 17. W. J. Price, Nuclear Radiation Detection, McGraw-Hill, New York, 1962. 18. Hanson Blatz, Radiation Hygiene Handbook, McGraw-Hill, New York, 1962. 19. D. C. Fleckenstein, Radiation and Radiation Protection, Z-3531, General Electric Co., Schenectady, New York, 1962. Radiation--Controllable Energy 371 20. Question, periodic publication on radiation control, R. S. Landauer Jr. and Co., Matteson, Illinois. 21. R. L. Fleischer, P. B. Price, and R. M. Walker, "Track Registration in Vari ous Solid-State Nuclear Track Detectors, The Physical Review, 133, 5A, A1443-A1449 (March 2, 1964). 22. S. J- Maisky, B. Roswit, C. G. Amato, H. M. Jones, B. Reid, and H. Patterson, "Measurement of Radiation Dosage," JAMA 187, 11, 839-841 (March 14, 1964). . 23. Pinhead and Planets, Courtesy Atomic Power Equipment Department, Gen eral Electric Co., San Jose, California. 24. Atomic Radiation, Prepared by R.C.A. Service Co., Camden, N. J., 1959, pp. 53-59. 25. Nuclear Terms, a Brief Glossary, U. S. A. E. C., Oak Ridge, Tennessee, 1964. 26. D. F. Janes, "Ionizing Radiation--The Safety Engineer's Most Technical Chal lenge," Jour, of the Amer. Soc. of Safety Engineers, LX, 7, 9-14 (July, 1964). Biological Effects of Radiation Biological Effects of Radiation, 11, Proceedings of the International Conference on the Peaceful Uses of Atomic Energy, Geneva, 1955. Published 1956 by United Nations Publications, Sales No. 1956 IX.I, 11, New York. Biological Effects of Radiation, 22, Proceedings of the Second United Nations In ternational Conference on the Peaceful Uses of Atomic Energy, Geneva, 1958. Published 1958 by United Nations, Geneva, Sales No. 58 IX.2, 22. H. L. Andrews, Radiation Biophysics, Prentice-Hall, Englewood Cliffs, NJ., 1961. A. Hollaender, Radiation Protection and Recovery, by Pergamon Press, New York, 1960. Ethel Browning, Harmful Effects of Ionising Radiations, 1959, Elsevier Publish ing Co., New York, 1959. R. J. C. Harris, The Initial Effects of Ionizing Radiations on Cells, Academic Press, New York, 1961. S. Glasstone, The Effects of Nuclear Weapons, prepared by the U. S. Department of Defense, published by the U. S. Atomic Energy Commission April, 1962. U. S. Government Printing Office, Washington, D. C. Nuclear bomb effects computer insert is sold separately. L. A. Elson, Radiation and Radiomimetic Chemicals: Comparative Physiological Effects, Cancer Monograph Series, Butterworth, Washington, D. C., 1963. Isotopes Special Sources of Information on Isotopes in Industry, Agriculture, Medicine, and Research (a bibliography), T.I.D. 4563 (3rd Rev.), (January, 1962), U. S. Atomic Energy Commission, Division of Isotopes Development, Washington, D.C. Radioisotopes, a reprint with revisions from Atomic Energy Facts, Item No. 220, U. S. Atomic Energy Commission, Division of Isotopes Development, Washing ton, D. C. Radioisotopes in Science and Industry, A Special Report of the U. S. Atomic Energy Commission, U. S. Government Printing Office, Washington, D. C. (January, 1960). liiSsr,,-- 372 Safety and Accident Prevention in Chemical Operations "A" is for Atom, 16 mm sound color movie, 15 minutes, produced in 1953 by q eral Electric Co., Schenectady, N. Y., available on loan from Division of Publ ' Information, U. S. Atomic Energy Commission, Washington, D. C. Ic M. A. Rothman, The Short-Lived Radioactive Isotopes, reprinted from Fa Prints, 29, 1, Foote Mineral Co., 18 West Chelten Ave., Philadelphia Pa. 195^ Laws and Standards Federal Law 10CFR20, Title 10, Atomic Energy, Chapter 1, AEC, Part 20, a,vajj able from Division of Licensing and Regulation, LL S. Atomic Energy Comtnis sion, Washington, D. C. State, city, county, town, and other local regulations, laws, and codes should be consulted. National Committee on Radiation Protection and Measurement: the handbooks containing these recommendations are published by the National Bureau of Standards, U. S. Department of Commerce, Washington, D. C. Twenty one handbooks on specific phases of radiation protection are currently available from U. S. Government Printing Office, Washington, D. C. American Nuclear Standards are available from American Standards Association 10 E. 40th St., New York, New York. National Safety Council Sources of Information on Nuclear Energy, Data Sheet 446, X-Rays In Industry, Data Sheet 475, Ionizing Radiation. See also Chapter 42, pp. 42-41 to 42-51, Ionizing Radiation, Accident Prevention Manual for Industrial Operations, 5th ed., 1964, National Safety Council, 425 N. Michigan Ave., Chicago, 111. Periodicals The International Journal of Applied Radiation and Isotopes, a monthly publica tion, Pergamon Press, New York. Health Physics, Official Journal of the Health Physics Society, published bi monthly by Pergamon Press, New York. Atomics, bi-monthly publication, Technical Publishing Co., 308 East James St., Barrington, Illinois.. Nucleonics, monthly publication, McGraw-Hill, New York. American Journal of Roentgenology, Radium Therapy, and Nuclear Medicine, monthly publication, Charles C Thomas, 301 E. Lawrence Ave., Springfield, 111. Organic Substances with Radiation A. H. Samuel, "Radiation Chemistry," Industrial Research, 6, 3, 42-47 (March, 1964). A. Charlesby, Atomic Radiation and Polymers, Vol. I in International Series of Monographs on Radiation Effects in Materials, Pergamon Press, New York, 1960. R. O. Bolt and J. G. Carroll, Radiation Effects on Organic Materials, Academic Press, New York, 1963. F. A. Bovey, The Effects of Ionizing Radiation on Natural and Synthetic High Polymers, Interscience Publishers, New York, 1958. ETC 03401 23 Respiratory Hazards and Protection H. H. Fawcett Pure air, essential for breathing by humans as well as for the health of plants and animals, is a relatively rare commodity. No American or Canadian standard exists for breathing air. Yet, without this gaseous mixture, which is normally colorless, odorless, tasteless, and so ubiquitous it is taken for granted, life, as we know it on this earth, would cease in minutes. Since the average adult breathes about 16,000 quarts of air each day, air purity is a vital matter. Many impurities in the air are the result of natural forces, such as moisture from rain or dust from the winds on dry soil, while others are caused by the activity of man, from his breathing, his industry, or his misadventure. When impurities are in low concentrations, we say the air is "clean," but when the variations, either alone or in combination, exceed human tolerance, we say the air is "polluted" or "impure." No simple yardstick exists to aid in measuring with precision the exact point when air ceases to be "clean," and each situation must be judged independently before valid conclusions may be drawn as to the relative safety or hazard of an environment.1'2- 3'30 For routine industrial purposes, with which we are concerned, a guide is available in the Threshold Limit Values published after an nual revision by the American Conference of Governmental Industrial Hygienists (see Appendix).10 This guide lists several hundred sub stances, elements, compounds, and mixtures which have been studied in sufficient detail to suggest threshold limit values of time-weighted average concentrations in air for repeated normal work exposures. It 373 ETC 03402 374 Safety and Accident Prevention in Chemical Operations is strongly recommended that anyone who consults this guide carefully read the introduction, which plainly states what the values are and are not intended to denote. To relate these values to a given en vironment requires analyses and interpretation by a person with specific knowledge and training. "Community air pollution,'' as defined by the Interdepartmental Committee on Community Air Pollution of the United States Govern ment, "is the presence in the ambient atmosphere of substances put there by the activities of man in concentrations sufficient to interfere directly or indirectly with his comfort, safety or health, or with the full use and enjoyment of his property. In general it does not refer to the atmospheric pollution incident to employment in areas where wmrkers are employed, nor is it concerned with airborne agents of communicable disease, nor with overt or covert acts of war." Increasing emphasis has been placed on the role of impurities in even low concentrations when breathed for long periods of time. Federal, state, and local agencies are active in the study of this problem, and much legislation has been proposed and enacted; some of it is even enforced. For a more complete description of the general air-pollution problem, which is beyond the scope of this chapter, the reader is referred to cited references and to the air-purity control agencies active in local areas.4-9 Another guide, Maximal Acceptable Concentration, has been fur nished by the American Standards Association in the standards which that group issues for toxic substances in the air. This term is based on the premise that levels exist to which a person may be exposed without known ill effects or discomfort. These concentrations in themselves do not represent a scale of relative toxicity, but they do represent the concentration in air below which it is unlikely that ill effects will occur, except to hypersusceptible individuals. Knowing the permissible allowable concentration of a substance is only part of the problem. The physical state, effects of temperature, volatility, flammability, explosibility--these and other factors must be considered. A highly toxic liquid of low volatility may be less dangerous than one of lesser toxicity but highly volatile. A substance that is toxic by absorption must be handled differently than one that is toxic only by inhalation or ingestion. Some substances are syner gistic in that their toxicity is increased many fold in combination. Odor is no criteria of toxicity as some pleasant-smelling substances (such as hydrogen cyanide) may be quite deadly, whereas other disagreeable odors such as pyridine may be comparatively innocuous irritants. With hydrogen sulfide and with several other gases, the sense ET(- 03403 Respiratory Hazards and Protection 375 0f smell is quickly deadened, and hence the nose is not a reliable indicator of concentration. 23.1. DETECTION Substances such as acrolein, ammonia, bromine, chlorine, fluorine, formaldehyde, hydrogen chloride, hydrogen fluoride, ozone, and sulfur dioxide are easily detected by their irritating odor. It may be dan gerous to include fluorine and hydrogen fluoride in this category because of their quick corrosive effect on respiratory tissues. Many others can be detected by their characteristic odors, but arsine, hydrogen cyanide, nitric oxide, phosphine, and stibine may be present in con centrations above the permissible limits of exposure by the time their odor can be detected. Carbon monoxide is odorless, and for practical consideration, so is hydrogen sulfide. Even in permissible concentrations, which produce no irritation of the eyes or systemic discomfort, the olfactory nerves are paralyzed and the sense of smell lost within minutes, so the characteristic odor of rotten eggs no longer is recognized. In sudden high concentrations of H2S, the odor is not detected at all, so the sense of smell is not dependable for the detection and recognition of it. Both of these gases can be detected by chemical means and by instru mentation. In the past, and even in modern installations, canaries and Japanese waltzing mice have been used as a positive means of detection and warning. They cannot fail to respond to lethal concen trations of CO or H2S. Their use as detecting agents in mines is well known but their practical use to protect man has been questioned.98 Certain gases may be difficult to detect by any known means within the required range. Phosphine (PH3), for instance, has an odor threshold well above its Threshold Limit Value of 0.3 ppm, and the lower limit of detection of instrumentation is its TLV. An excellent manual of air sampling equipment is available.8 23.2. PROTECTION To prevent or reduce dangerous exposure to toxic materials, they should be confined insofar as possible, and releases should be vented outside buildings and away from work areas and other populated areas. Exhaust ventilation should be provided to remove emissions, and/or personal protective clothing and equipment can be worn. In dealing with such gases as the phosphine mentioned above, where the toxicity is so high, and the detection and warning so difficult, con- 376 Safety and Accident Prevention in Chemical Operations finement is very important. If it is necessary to work with such a highly toxic gas inside, the building air probably should be changed every two minutes, with auxiliary equipment to double this air change in case of emergency--especially if the gas is also as flammable and explosive as is phosphine. In addition, suitable respiratory equip, ment should be worn, or at least it should be readily available so it may be donned in seconds. Time wasted while seeking a breathing apparatus, removing it from the box, inserting a canister (if required) and making certain it is properly working, may easily mean the dif ference between emergency control and disaster; and every effort should be made to be certain the breathing apparatus is of the cor rect type, that the wearer is properly trained, and can have the device in actual operation in as few seconds as possible. Half-hour or hour breathing apparatus in boxes requiring time and gymnastic activities of a superman to put on, and a high degree of training to insure they are properly working, have only limited value in operations where immediate control is needed. The apparatus should be of the size, type, and simplicity commensurate with practical and realistic needs. A more complete discussion on the limitations of various breathing devices is found later in this chapter. To determine whether or not a hazard exists in an environment, a survey may be made, samples taken and analyzed, and the results correlated with the clinical observations of the persons exposed. It must always be remembered, as has been pointed out, that the at mosphere could be purple with pink dots, and yet no injuries may occur as evidenced by the only true criteria, namely, the humans in volved. If a hazard is judged to exist, however, appropriate measures, such as process modifications, substitution of materials, revised work practices, changes in shift schedules, better ventilation, or other controls may be recommended. The use of respiratory protective devices, such as respirators, filter masks, or similar devices, for a long-term solution to a respiratory problem, has seldom been satis factory. Before reviewing respiratory hazards and protection, a brief listing of the classes of airborne substances may be useful: Aerosols Based on their physiological effects, aerosols may be classed: 1. Nuisance and Inert. Nonfibrosis-producing and nontoxic, but may be harmful in high concentrations examples: calcium carbonate, magnesium carbonate, and gypsum ETC 03405 Inert Pulmonary Reactions. Produce nonspecific pulmonary reactions examples: silicates, carbon, and aluminum 3. minimal Pulmonary Fibrosis-Producing examples: barium compounds, tin, and iron oxides 4. Extensive Pulmonary Fibrosis-Producing examples: silica and asbestos Chemical Irritants. Produce inflammation or ulceration examples: acids, fluorides, chromates, and chromic acid Toxic Systemic Poisons. Produce pathological reactions examples: a. lead, manganese, antimony, arsenic (not considered significantly more toxic than lead) b. arsenates, organic phosphates, cadmium, radio isotopes, and beryllium (considered significantly more toxic than lead) 7. Allergic Manifestations. Produce allergic reactions examples: pollens, and dust of certain exotic woods 8. Fever-Producing Reactions. Action unknown or allergic examples: metal fumes, hemp, cotton, jute, bagasse Aerosols (also called dispersoids or particulate contaminants) are substances present in the air as minute particles (dusts), as fumes (metal fumes), or as mists (chromic acid mists). In grouping these, it is recognized that they may be physically filtered, screened, or ab sorbed from the air with properly designed filters.11 Aerosols may range in size from 150 microns to 0.001 micron in size (1 micron equals 39.37 millionth of an inch, or 1 X 10~4 cm). In considering the health hazards of dusts, it must be remembered that many dusts are also fire and explosion hazards.18'1718 Pneumoconioses is a group of lung conditions which result from the inhalation of certain dusts or mists. Silicosis is one of the most common types of pneumoconiosis, and it is caused by the inhalation of "free" or uncombined silica, such as quartz, opal, flint, and cristobalite. Many other dusts may produce other types of lung involve ment, such as carbon, iron, and barium (the last of which is also toxic). Other dusts cause chemical irritation, such as acids, alkaline sub stances, fluorides, and chromates. Allergic reactions may be caused by nuisance dusts such as pollens, some synthetic resins, certain plas tics, felt, fur, gums, spices, tobacco, paper, rubber, exotic woods, starch, flour, and wool.13 In referring to respirators for exposure to dusts classified above, the United States Bureau of Mines groups these as pneumoconiosis-producing and nuisance dusts.- ETC 03406 378 Safety and Accident Prevention in Chemical Operations Another classification refers to "toxic dusts." The Bureau uses lead as the reference, and says that listed dusts, for this purpose, are not significantly more toxic than lead, feeling that a difference between 0.1 and 0.2 milligram per cubic meter as a toxic concentration is not significant. Among dusts more toxic than lead are chromates, organic mercury compounds, yellow' phosphorus, picric acid, selenium, tellurium, and calcium arsenate. Respirators approved for all the above mentioned dusts (both toxic dusts and pneumoconiosis-producing and nuisance dusts) are called "dust" respirators. "Fumes" include aerosols formed by the condensation of vapors from heated metals. Melting, cutting, and w'elding of zinc, lead, cad mium, and other metals produce such fumes. "Mists" and "sprays" include liquid droplets formed when liquids are carried into the air or are formed by a reaction with the moisture in the air. An interesting example is that 0.3 ppm sulfur dioxide with water in the presence of sunlight may form as many as 20,000 particles per cubic centimeter of sulfuric acid mist. The availability of filters with pore sizes from 10 millimicrons (ap proximately the size of the polio virus) to 5 microns (the size of com mon contaminants in liquids) has greatly improved and speeded up analyses of aerosols such as acid mists, metal fumes, smokes, and radioactive particles.15 In recent years, study and measurements of even smaller particles in air than previously observed, known as condensation nuclei, have contributed to our knowledge of the nature and number of particles in air. Particles on w'hich water will condense are called condensa tion nuclei; under natural conditions only the larger particles are so affected. When the air is sufficiently supersaturated, however, apparently any particle will serve as a condensation center. Particles from such diverse substances as platinum, silver, stearic acid, glycerin, and lubricating oil will form droplets at a sufficiently high super saturation of water vapor. Practical methods are now available to measure or count the number of aerosol particles in free air. Wider use of such techniques will doubtlessly throw much light on many air pollution problems, as well as lead to further improvements in our knowledge of aerosols, and hence respiratory hazards and protection.1* Respirators and masks intended specifically to furnish protection against pesticides, w'hich are found by tests to give adequate protec tion against dusts, mists, and low-vapor concentrations of certain pesticides, are listed by the United States Department of Agriculture.21 It should be noted the service of the United States Department of ETC 03407 r Respiratory Hazards and Protection 379 Agriculture differs significantly from the service offered by the United States Bureau of Mines. The two services are not parallel or even analogous. Gases and Vapors In this class may be included most of the air contaminants which are not classified as aerosols. Irritant gases or vapors are those which produce inflammation of tissue, such as the skin, the eyes, and the respiratory tract membranes. They are divided into two general groups: 1. Action is limited to irritation (such as hydrogen chloride). 2. Action'extends to systemic effects (such as the oxides of nitrogen). Some of these gases and vapors have pronounced odors, but the nose cannot be depended upon as a reliable method of estimating concentrations, or in forcing persons to escape. Lacrimators or tear gases are ordinarily harmless to life in the concentrations usually obtained when used in open air. However, chloracetophenone, one of the tear gases used by the military and law-enforcement agencies, fired in shells or grenades, has caused two fatalities. In one case, a forty-year-old man locked himself in a room and successfully re sisted all attempts to eject him. The police were called and they injected tear gas to drive him from his stronghold, but they were not able to enter for an hour and a half; during this time the man was exposed to the chemical fumes. He was found unconscious, and taken to the hospital where he died two days later from the inflammation of the air passages. In another instance, a twenty-eight-year-old male barricaded him self in a bedroom of his house after refusing to leave as requested by law officers. A tear-gas grenade was tossed into the bedroom through a transom, and the man forcefully removed at a time estimated be tween 10 min and a half-hour. He expired in the hospital less than 18 hr later. It has been estimated that 0.82 ounce of tear gas per 1000 cu ft of air is a lethal concentration for a 10-min exposure. Prompt entrance by trained rescue personnel wearing respiratory protection, approved for this type and level of exposure, should be considered whenever such gases are deployed in confined space. Brombenzyl cyanide, which has an odor like sour fruit, is also used as a lacrimator. Lung irritants, such as chlorine, phosgene, and chlorpicrin, have had military application. Vesicants (skin irritants) such as mustard gas, lewisite, and the nitrogen mustards are also respiratory 380 Safety and Accident Prevention in Chemical Operations irritants. Sternutators (sneeze gas) such as diphenyl chlorarsin and adamsite (diphenylamine chlorarsin) produce effects designed to de stroy morale, and they are not used for their lethal action. Nerve gases, which inactivate the cholinesterase, and cause acetylcholine accumulation in the central and peripheral nervous system, produce spasm and vision disturbances in very low concentrations, and more serious effects involving the respiratory system in higher concentra tions. Asphyxiants are substances which deprive the body tissues of oxygen, causing hypoxia or oxygen starvation. Two modes of action are known: 1. Simple Asphyxiants (such as nitrogen, hydrogen, helium, and methane) dilute or replace the partial pressure of oxygen in air. 2. Chemical Asphyxiants such as carbon monoxide, aromatic nitro compounds, and aromatic amino compounds (such as aniline, nitro benzene, and chemically related molecules), hydrogen cyanide, hydrogen sulfide, acetonitrile, and other substances which combine with the hemoglobin of the blood or otherwise interfere with the oxygen-carbon dioxide exchange. Carbon monoxide has 210 times the affinity of oxygen for the blood. The rapid action of the above substances, once they have entered the blood, pleads for extreme respect. The above discussion in no way minimizes the respect due the simple asphyxiants, for the insidious nature of their action is little appre ciated. Nitrogen and other simple asphyxiants give almost no warn ing between the time breathing air is replaced with the asphyxiant and unconsciousness overtakes the breather. Under proper medical super vision, pure nitrogen may be breathed for several seconds, and this technique has been used clinically by Himwich and others. A loss of mental facilities begins within a few seconds, and unconscious ness may occur shortly after with no warning. The brain is the first organ of the body to be seriously affected by oxygen want, and the subject "blacks out" quickly. Mention is made of this little-appreci ated phenomenon, not only because asphyxiants can be released in a room or tank with inadequate warning from the action of a fixed carbon-dioxide fire-extinguishing or inerting system, from a large spill of a liquefied gas (such as liquid nitrogen, liquid hydrogen, or liquid helium), from a leaking gas system, from an inert-gas generator (entrance into a tank car or other confined space which has been in erted with gases for refrigeration or to replace oxygen in the air), or from leaking cylinders. Respiratory Hazards and Protection 381 Even more insiduous but no less serious is the occasional use of a plant compressed-air supply for respiratory purposes without recog nizing the hazard. If a cross connection is made which would permit an asphyxiant, toxic, inert, or flammable gas at a higher pressure to enter the compressed-air system at any point in the system, the results can be fatal. Two separate incidents have occurred within the past decade where nitrogen gas had been deliberately introduced into an air supply to maintain pressure for pneumatic instruments, and in both cases men, who were not aware of this change in operations, were overcome and expired before help could arrive. The importance of a separate system for breathing air cannot be overemphasized. It may also be noted that the United States Bureau of Mines approval for airsupplied breathing equipment stipulates that the quality of the breathing air is the responsibility of the user. A separate air supply, supplied by a compressor which cannot evolve carbon monoxide, carbon dioxide, oil mist, moisture, or other impurities, or compressed air from which the impurities have actually been removed, or from cylinders of tested known purity, should be used for air-supplied respirators, hoods, suits, and self-contained breathing apparatus which uses compressed air. The supply system should include pressure relief valves, filters, regulators, and absorbents as recommended by the manufacturer of the respiratory protective equipment and the United States Bureau of Mines. This problem has become increasingly important with the rapid growth of interest in self-contained underwater breathing apparatus (SCUBA) as well as air-supplied, self-contained, and hose-line breathing equipment.23 An interesting incident, which illustrates that even "plant air" can create difficulty when not attached to breathing apparatus, occurred in a radio parts firm. Fourteen of 200 women employees were taken to hospitals when an odor, apparently of overheated oil, filtered from machines powered by compressed air, because of an overheated air compressor. The plant air lines apparently distributed these fumes to all parts of the plant. It is especially fortunate no one was wearing any breathing equipment attached to such a system. Anaesthetics Anaesthetics are gases and vapors which act primarily to induce the symptoms of anaesthesia when inhaled in sufficient quantities. They include the classic anaesthetics diethyl ether and chloroform but they also include most halogenated hydrocarbons, such as methyl 382 Safety and Accident Prevention in Chemical Operations chloroform (1,1,1-trichloroethane), trichloroethylene, ethylene oxj^ nitrous oxide (laughing gas), and many other organic compounds As well as having physiological effects, these materials alone in combination may produce decomposition products in a fire or whe they are otherwise subjected to elevated temperatures. Even rela tively harmless substances such as nonflammable refrigerants with low toxicity will evolve irritating decomposition products if heated above their decomposition temperatures. This has occurred where fluorocarbons were used as cleaning solvents for metal parts. After cleaning, the parts were heated over a flame to dry and to remove excess solvent. Several persons were hospitalized with pulmonary congestion. A similar problem can occur with trichloroethylene Trichloroethylene vapor degreasers, when properly installed, maintained, and operated, are usually safe, but the failure or misuse of these degreasers has created serious problems, including both fire and toxicity hazards. Trichloroethylene is not completely nonflammable Mass hysteria and unconsciousness because of the little-appreciated anaesthetic action of the trichloroethylene can occur in seconds; in one incident, seventy-two persons were overcome, and in another twenty-six persons. Fortunately, all recovered after removal to fresh air and oxygen inhalation. The hazards of carbon tetrachloride mix tures in fire fighting, and of carbon tetrachloride in other applications, have been documented. It is hoped that in a few years, the vaporiz ing-liquid type extinguisher will be found only in historical collec tions and that alternate cleaning solvents will have replaced it for "bucket cleaning." Substances Producing Other Effects This class includes several substances whose action differs from previously mentioned substances. Included in this group are mercury vapor, white phosphorus, tetraethyl lead, tetramethyl lead, nickel carbonyl, arsine, phosphine, the boron hydrides, including diborane and pentaborane, hydrogen sulfide, and military "nerve gases." The initial action of these gases and vapors is primarily on the nervous system with respiratory arrest following. Arsine is the only gas which dissolves red blood cells. If the above classification appears complicated, it should be noted that air contaminants seldom occur alone, and that even less is known about the combined action or synergistic effects of two or more substances, especially if they are classified in different groups. Even if the particles dispersed in air are nontoxic by themselves, they may Respiratory hazard Respiratory Hazards and Protection 383 00 S.C.B A = Self-contained breathing apparatus Outline for the selection of respiratory protective devices based on Bureau of Mines I.C.7600 Rev. 2 /2 6 /6 3 Howard Fawcett 384 Safety and Accident Prevention in Chemical Operations act as carriers of condensable toxic vapors. Formaldehyde for example, can have its toxicity increased five-fold by the presence of an inert aerosol. Hence, it is suggested that respiratory protection can become highly complicated, and that the practical application of respirators, gas masks, and self-contained breathing apparatus (each with its limitations), even by persons thoroughly trained in their use (who may or may not actually use them properly), is not a simple problem. Inadequately trained persons in an emergency situation the nature of which is not fully known at the time, are in especially vulnerable positions, regardless of the availability of quality equip ment. Types and Applications of Respiratory Protective Devices AIR-PURIFYING RESPIRATORS The fundamental limitations of any air-purifying respiratory device are that the air must be within the limits for which the respirator was designed (for example, the oxygen content must be over 16%), that the unit will protect only against the specific substance or combina tions in certain concentrations for which it was designed (for example, aerosol filter-type respirators will afford no protection against gases and vapors), and that the canister or filter must be maintained in proper working condition attached to a properly maintained facepiece which fits snugly enough to exclude leakage of contaminated air. Aerosol filter-type respirators require frequent changing in filters when breathing resistance becomes uncomfortably high when worn in areas containing excessive dust, mists, or fumes. Chemical cartridge respirators will safely protect only against the specific gases and vapors in nonemergency situations where no more than 0.1% concen trations are encountered. Extremely toxic materials, such as acrolein, acrylonitrile, aniline, dimethylaniline, arsine, bromine, carbon di sulfide, dimethylsulfate, hydrogen cyanide, hydrogen fluoride, hydro gen selenide, hydrogen sulfide, iodine, methyl bromide, methyl chloride, nickel carbonyl, iron carbonyl, nitrobenzene, nitroglycerine, nitromethane, the oxides of nitrogen (nitric oxide and nitrogen diox ide), ozone, phosgene, phosphine, phosphorous trichloride, stibine, sulfur chloride, diborane, pentaborane, and other substances are too toxic even in very low concentrations to rely on a simple cartridgetype respirator. Chemical cartridge respirators should not be used against gases which are odorless, or whose odor threshold is high, since odor is the Respiratory Hazards and Protection 385 FIG. 23.2. One respiratory facepiece may be used with several different filters for a variety of exposures, underscoring the need for selection of the properly designed filter for each particular exposure. only warning of failure of the canister, facepiece leakage, or of con centrations which are above the design limits of the respirator. Methyl chloride is an example of a gas whose warning properties are inadequate for practical warning purposes. Substances which are highly irritating to the eyes, such as sulfur dioxide and ammonia, require eye protection (such as gas-tight goggles, an air-supplied hood, or a mask with a full facepiece). Several lacrimatory (tear-produc ing) substances, such as benzyl chloride, are in the same classification, and a respirator alone is clearly inadequate. Carbon monoxide can not be stopped by a chemical cartridge, except of the type used in the canister of the Type N universal gas mask and the miner's self rescuer, both of which contain Hopcalite. This mixture of oxides of manganese, copper, cobalt, and silver catalyzes the oxidation of car bon monoxide to carbon dioxide, provided it is properly activated, dry, and the carbon monoxide concentration is not excessive. These qualifications have been the cause of much misunderstanding in the past. 386 Safety and Accident Prevention in Chemical Operations Ammonia cartridge respirators will safely protect against ammonia vapors up to 1000 ppm, while eye irritation from ammonia begiQa about 70 ppm. Mercury cartridge respirators are effective against concentrations of mercury vapor normally encountered at ambient temperatures and pressures, but service life is proportionally re. duced where higher concentrations of mercury from elevated tem peratures and pressures are present. Specially designed vacuum cleaners for use in cleaning mercury spills (ordinary vacuum cleaners in this service create more hazard than they correct), and highly portable mercury vapor survey instruments have aided greatly in reducing this hazard. No Bureau of Mines approval schedule has been established for chemical cartridges to protect against other than organic vapors. Combination cartridges have the limitation of a shorter service life when used with one particular type hazard than the equivalent specific single purpose cartridges would have for the same hazard. Many respirators use a "half-mask" or oro-nasal (mouth and nose) facepiece, while gas masks use both half-masks and full facepieces. Only full facepieces on gas masks are approved by the United States Bureau of Mines, since it has been found difficult to achieve a tight fit with a half-mask. Recently, the self-rescue or "pocket" respirator, FIG. 23.3. The variety of respirators, designed for a wide range of exposures (from toxic airborne particulate to heat), mandates careful selection and control. ETC 03415 ETc 03416 388 Safety and Accident Prevention in Chemical Operations tridges for twelve different applications will fit the basic holder and mouthpiece. Industrial canister-type gas masks, with canisters designed for specific substances or specific combinations, have the same limitations in general as chemical cartridge respirators, except that they are ef fective in concentrations of any specific gas or vapor, or members of the group of gases or vapors for which they are designed, of not more than 2% concentration in air or a 2% total concentration for a mixture of gases or vapors for which the canister is designed. The industrialtype ammonia canister is approved for 3% ammonia. Depending on the size of the canister and the service for which it was designed, the service time varies. Protection against a combina tion of various gases and vapors, such as acid gases, organic vapors and ammonia can all be obtained in one canister, but the service life of such a combination is shorter in the combined canister when used with one substance, than is the life of an equivalent canister designed for the specific substance alone. The only warning that a canister or cartridge is "exhuasted" or spent is sensory detection of vapor or gas passing through the canister or cartridge. For carbon monoxide, which is odorless, canisters have a timer or window indicator. It is obvious that the "self-rescuer" type does not even have this warning aspect, since the nostrils are closed off. In other words, unless we have a complete knowledge of the actual concentrations which are experienced, there is a false security in using canister-type or cartridge-type gas masks and respi rators which have caused many users to question the place of such devices. Persons who need corrective lenses in order to work properly when wearing respiratory protection, especially full facepieces, may be interested in three methods of incorporating lenses inside a facepiece. One method consists of wire frames which fit around the circumference of the facepiece sight lenses and hold a 50 mm round lens. A second method suspends wire-frame goggles with short bows between holders molded into the facepiece. A third method consists of a center post built inside the mask, on which can be attached 40 mm rimless glasses. Such arrangements seldom encourage perfect alinement of the pre scription lenses to the viewer's eyes, but, with adjustment, a sufficiently accurate fitting can be achieved for most persons to wear for reason ably long periods. Contact lenses offer a possible solution to this problem, but the hazards of contact lenses in increasing or aggravat ing a chemical burn to the eye, especially if the lenses are not im mediately removed before irrigation with water, must be recognized. ETC 03418 390 Safety and Accident Prevention in Chemical Operations of the canister, its construction, and its limitations, varies with the individual manufacturer, who should be consulted for details. jn general, the Type N universal gas mask may be used for protection against smoke and gases which do not exceed 2% by volume total where adequate concentration of oxygen is present. Usually 16% oxygen is cited as the practical minimum for the use of the Type jj mask, but life is not actually in danger until somewhat lower concen trations are reached, depending on what the other gases present are the activity of the wearer, the altitude, and other factors. If the mask has a timer, wrhich is used to count the number of inhalations and in dicate total use of the canister, the canister should be discarded at least as soon as the pointer on the timer has completed one revolu tion, if not sooner. One authority recommends that Type N universal canisters be weighed immediately on receipt from the manufacturer and that they be discarded as soon as they gain 45 g for the normal size canister. The 45-g limit was imposed since it represents the limit of the dessicant layers to keep the Hopcalite layer dry. All manufacturers build an "indicating window" into at least one model of the Type N universal canister to indicate remaining protec tion against carbon monoxide. The indicator is the color change from blue (dry) to pink (wet) of a piece of specially treated paper, which warns of the excess moisture which prevents the Hopcalite from prop erly operating; hence, if the indicator shows pink the canister will no longer furnish protection against carbon monoxide. In addition, a one-way inhalation valve has been added to the canister top to prevent moisture or water from entering the canister from above. The maximum shelf-life of the Type N universal canister, once the canister has been attached to the facepiece, is one year, if stored with the bottom seal in place, even though the mask has not been used. If stored with both top and bottom seals unopened, as received, the shelf-life is considered by some to be three, and by others, five years. The manufacturer should be consulted and his recommendations followed, including whether the canisters should be stored vertically or on the side. There is a growing conviction among safety and medical personnel in large laboratories, especially where a wide variety of substances may be encountered in unknown concentrations, that self-contained breathing apparatus should replace all canister-type masks--whether industrial or universal Type N. The writer agrees that no canistertype masks should be used for emergency control where the concen trations and identity are in doubt. From a practical viewpoint, this includes nearly all chemical spills and fires. ETC 03419 fffl r ETC 03420 392 Safety and Accident Prevention in Chemical Operations has stockpiled a mask designated as CD V-800 organizational mask for use by Civil Defense personnel. The canister on this chin-style mask is the same as used on the United States Army Assault Mask This mask is reported to give "excellent protection" again CW (chem ical warfare) and BW (biological warfare) agents, as well as against the inhalation of radiological particles, or CBR (chemical, biological and radiological). Designed to be used in conjunction with a detec tion kit (which will detect and distinguish between the nerve gases and the mustard gases), the V-800 mask is designed specifically f0r war gases (including nerve gases) and will not protect against carbon monoxide, ammonia, and other industrial gases. The Army Chemical Corps has designed and developed a new mask, the M-17, for troops It is designed to give complete protection against the inhalation of war gases, biological warfare agents, and airborne radioactive particles, IT! FIG. 23.7. Military masks were not designed for fire fighting or industrial gases. Ijf.5 In addition, long storage may result in damage to rubber and metal, as shown here. Thousands of such masks are surplus and obsolete, and their use by unin formed persons constitutes a threat to life. ETC 03421 Respiratory Hazards and Protection 393 FIG. 23.8. Two misuses of a gas mask: (a) wrong type and (b) improperly worn. Such masks were never intended for fire fighting or industrial gases. but, of course, it does not actually protect against direct radiation effects. The M-17 mask does not have the protruding canister used in previous army masks, since it uses a new light-weight pliable gasaerosol filter material. Pads of this material are enclosed within cavities molded into the rubber facepiece of the mask. Lower breath ing resistance, superior vision, better speech transmission, and greater comfort are claimed. It should be emphasized that no gas mask should be used for purposes for which it was not designed. After both World Wars, several instances were reported where "surplus" army masks were used for protection against gases for which they were not designed, with serious consequences. It is vital that gas masks are not misused. AIK-SUPPLIED RESPIRATORS Since the simplest solution to respiratory problems is to supply clean air to the breather, the use of an air supply from some remote source where the air is not contaminated is both simple and logical. 394 Safety and Accident Prevention in Chemical Operations For many applications, air-supplied equipment has real advantages but this equipment, like all other, has definite limitations. The aim.! plest type is the Type B hose mask, which is a facepiece to which is attached a large-diameter (1-in. Inside Diameter) hose without a blower. The hose must extend to a respirable air source. This mask depends on the breathing action of the wrearer to move the air. For this reason, a maximum length of 75 ft of hose has been established for the hose mask without blower. Howrever, such a unit should not be used in atmospheres immediately harmful to life, or from which the wearer can not escape without the device. Low-pressure blowers, operated either by hand or by power (power blowers do not have Bureau of Mines approval at present), are used to supply Type A hose masks up to 300 ft. All hoses must originate at the blower. A respirable source of air must be assured, and a safety man with a full understanding of his duty must be present at the blower at all times. A sturdy harness must be provided to which a life line may be secured. Fouling of the hose must be avoided since this may cut off the air supply. The exit route must be the same as the entrance route. Hose masks can be used safely only if the above pre cautions and limitations are observed. Air-supplied Type C respirators are divided into two classes: the continuous-flow type and demand- or pressure-demand-flow' type. The continuous-flow type is usually used with a powered compressor or blower, while the demand-flow type is usually supplied with breathing air from large cylinders. The use of such equipment in atmospheres immediately hazardous to life is not recommended, since failure of the air supply or fouling of the hose would be serious, and further, it is vital to have respirable air of unquestioned purity. It is recom mended that a separate air system be used exclusively for breathing air. Depending on the pressure available and the diameter of the hose, there is a limit to the length of hose which is practical for the continuous-flow type. Wherever possible, such systems should be piped as closely as possible to the outlet so possibility of fouling the hose and cutting off the air supply will be minimized. Exit from areas where air-supplied respirators are used must, of course, be the same as the entrance route. If an air compressor or air from a cylinder is used, sufficient pressure relief and regulators must be available to protect the wearer against pressure in excess of that prescribed for the equipment. If a plant air compressor must be used for breathing air, it should be equipped with a temperature cut-off or carbon monoxide alarm, and a conspic uous sign placed at the compressor site to indicate it is used for breath ing air. ETC 03423 ETC 03424 ETC 03425 Respiratory Hazards and Protection 397 FIG. 23.11. Air-supplied hood for heavy-duty sandblasting. face, and respiratory protection. Depending on the particular fabric, plastic, or composition used in its construction, this suit permits ex tended work inside tanks, reaction vessels, and other confined space which still contains a hazardous-to-life atmosphere. Properly used, together with safeguards to insure that the wearer's air supply and life line are always in proper position and working order, this suit has increased the safety and decreased operating costs in maintenance work inside vessels containing materials which are corrosive or are ETC 03427 ETC 03428 400 Safety and Accident Prevention in Chemical Operations V (a) (b) (0 FIG. 23.14. M-S-A Cool Flow System Employing Vortex Tube for Cooling and Ventilation, (a) Vortex tube mounted on rear of protective suit. (b) Suit showing small internal tubes for distribution of air. (c) Vortex tube supplying cool breathing air to helmet-vest combination. Many other combinations are possible. Photo courtesy Mine Safety Appliances Co. missile fueling operations and in handling highly reactive chemicals such as fluorine. One such suit system employs a back pack which uses liquid air to supply both breathing air and air for cooling (Fig. 23.15). Regardless of the type "respirator" used, a definite program of edu cation and control is necessary to insure that the device is actually worn properly, properly maintained, and that it is effective in achieving what is expected. After the Canadian Chalk River atomic reactor incident, respirators were used to prevent inhalation of radioactive contaminants. This program was successful only after a respirator officer was appointed to control their use and maintenance. Regular urine samples were analyzed to indicate the degree of effectiveness of the program, and an improved respirator, which was proven more effective, was made available for use. Before considering self-contained breathing apparatus, a brief dis cussion of emergency situations which require the use of such equip ment may be useful. For emergency situations, where entry is essential for the conserva tion of life and property, there are neither fixed guides nor sufficiently accurate and foolproof instrumentation. In situations that may exist in firefighting, in the escape of vapors or gases, or where an oxygen deficiency may develop, the prudent approach is to assume conditions ETC 03429 ETC 03430 402 Safety and Accident Prevention in Chemical Operations are serious, and to use respiratory and other protection which will most adequately meet expected conditions. A preliminary appraisal of the situation must be made, and an arbitrary decision made at once by the qualified authority (usually the fire chief, the ranking police officer, the safety engineer, or the medical officer), to: 1. Retreat or approach. 2. Specify the objectives (personnel versus property). 3. Specify the procedures. 4. Order the use of required personnel and equipment. Records of the fire services contain many instances where emergency personnel made an unnecessary sacrifice of their own lives under condi tions where little or nothing would have been achieved by approaching the emergency scene. To cite a few specific instances, ten firemen died from injuries received as they approached an outdoor aluminum storage tank, which erupted with such force that three were killed by fragmentation, and seven by fumes and skin burns from the chlorinated hydrocarbon mixture. A chemical reaction of the Friedel-Crafts type had occurred between the aluminum tank and the stored solvents, which built up excessive pressure. No fire whatsoever was involved, and ten lives were sacrificed without any advantage. In a more recent case, four firemen died in an explosion while fire fighting in a tractor-trailer truck during unloading of a cargo of organic peroxides, even though the identity and the hazard of the cargo was known. Another instance occurred when a train derailment caused a tank car of propylene, which was intact, to be weakened by the impingement of a small fire from another tank car which was leak ing. The hazard was known, and all personnel were warned, but nineteen hours after the derailment, the work crews believed the hazard was over, and were at work moving and repairing the damage. Without warning, the propylene tank car exploded, soaring through the air several hundred feet. Numerous members of the work crew and fire services were killed and injured, because of the general dis regard for the danger warning such an extended time after the derail ment. Virtually all the fire personnel and emergency equipment in Texas City, Texas were destroyed and over six hundred lives were lost, when two ships containing a fertilizer grade of ammonium nitrate exploded. Conservation of human life, including that of the emergency person nel, must always take precedence over the conservation of property. Fire services and police are not alone in the disregard for their own safety. Safety engineers, physicians, nurses, and management person ETC 03431 Respiratory Hazards and Protection 403 nel have encountered serious personal injury where, in the excitement and their concern for personnel and property, they ignored their own needs for protective equipment. A graduate chemical engineer, who was superintendent of a phosgene-production unit gambled that he could enter a building in which an operating error had been made, to control the emergency which threatened the loss of several tons of phosgene. Either his respiratory protection was inadequate or not properly worn, for he was so seriously exposed that, although he brought the emergency under control, he died from phosgene poisoning a short while later. The supervisor of health and safety in a chemical plant died in an attempt to aid several other persons overcome with hydrogen sulfide, which had formed from an emergency in which sodium sulfhydrate contacted acid in a drain. Other analogous instances could be cited. The point is that such situations are especially pernicious, since the increased breathing be cause of the excitement, coupled with violent physical exercise, tends to drive gases and vapors deeper into the lungs and to accelerate the action of the substance. If a rescuer can remain calm, however, and breathe very shallow7 so that only tidal air is being moved, a much higher probability of survival can be expected. This skill has been observed in experienced nitration operators who learned to control their breathing so carefully that they wrere considered "immune" to oxides of nitrogen in concentrations which caused serious, and some times fatal, lung damage to their less-wise associates. Objectives to be achieved in the emergency action must be carefully stated and fully understood by all involved before a decision is made to advance. If the prime objective is search and rescue of persons w7ho may be trapped or otherwise unable to escape, it should be ex ecuted with all dispatch, and a systematic search plan ordered to conserve vital time and to reduce possible duplication of effort. If there are other objectives, such as the opening or closing of valves, switches, pumps, or controls, extreme care must be exercised to insure that the full consequences of such operations are known. To operate an ordinary domestic electric switch or motor starter in an explosive atmosphere, as in a spill of a flammable liquid or a leak of flammable gas, may supply the ignition source that will result in disaster. Any equipment w7hich must be w7orn or carried in an emergency op eration will, by its weight or bulk, hamper or reduce efficiency. Against this hard fact must be balanced the benefit, both in safety and in efficiency, of having the proper equipment at the time and place it is needed. Rubber coats, boots, and hard hats have been accepted by the fire services and other emergency personnel. Records of many large 404 Safety and Accident Prevention in Chemical Operations and small fires prove that fire gases, especially when accompanied by heat, are often more lethal than fire itself. Anyone doubting this; statement should read a detailed narration of the Cocoanut Grove Nightclub Fire in 1942, and study the research report on fire gases published by the National Fire Protection Association.12 In general, three conditions, which produce environments immedi ately dangerous to life, require the proper use of adequate respiratory protection for even a short entry. These include: 1. Oxygen deficiency, in which the oxygen in air is reduced to less than 16%. 2. Toxic gases and vapors, such as hydrogen sulfide, chlorine, phos gene, and the oxides of nitrogen, in which serious effects may result from breathing less than 100 ppm for less than a minute. 3. Toxic gases and particulates, such as produced in fires involving ordinary combustibles, wood, paper, textiles, and plastics, as well as in the fumes from welding or other high-temperature metal operations. A brief discussion of each with a specific example will be given: Oxygen Deficiency If a tank is not ventilated after purging, or rusting occurs in a closed vessel, the oxygen concentration in the air will drop. Although light work is possible for several minutes when the oxygen concentration in air is less than 16%, a person breathing such low-oxygen air exhibits symptoms ranging from in creased volume of breathing to unconsciousness and death. This condition is far more common than generally realized, in tanks, pits, caves, mines, wells, underground pipes, the holds of ships, and in burning buildings. It is the cause of suffocation by infants where blankets and plastic bags exclude air: it continues to take a toll of young lives where doors have not been removed or rendered inoperable on discarded refrigerators, ice chests, and deep freezers, used as hideaways during unsupervised plat' by children. An example of a condition which may lead to oxygen deficiency is given in the following case history: A motor transport company carries a variety of chemicals. It was neces sary to clean the tanks whenever a change of chemical cargo was contem plated. A tank had contained sodium sulfide. After filling the tank with water and draining, an employee entered the tank to check for cleanliness. All the access ports of the tank were uncovered, but no air movers or forced ventilation was used. In a few minutes, a eo-worker noticed the employee unconscious in the tank, made the rescue, and successfully applied artificial respiration. The cause of the accident was exposure to irrespirable gases, which were judged either oxygen deficient or to contain hydrogen sulfide from yife- Respiratory Hazards and Protection 405 the action of the water on the sodium sulfide. Respiratory protection was not being used. In oxygen deficient environments, only two types of respiratory protective devices are recommended: the self-contained breathing apparatus, and the hose mask with blower. Of the two, the self-contained breathing apparatus permits much greater freedom of movement. The hose mask with blower requires an operator or attendant for the blower, restricts the wearer to 300 ft of hose, and requires exit by the same route as the entrance. Toxic Gases The second major circumstance immediately hazardous to life is the release of toxic gas or vapor. Such incidents may occur with little or no warning, and immediate steps must be taken, as noted pre viously, to identify both the nature of the emergency and what action is indicated. Three major sources of such gases and vapors may be listed: 1. Permanently installed equipment and processes, such as storage tanks, process piping, and reaction vessels. 2. Mobile equipment, such as cans, drums, cylinders, tank trucks, tank cars, barges, and tanker ships. 3. Chemical reactions out-of-control. A tank car had been filled with chlorine 24 hrs previously, and was awaiting pick-up on a rail siding. A crack developed in the metal shell of the tank, permitting the 30 tons of liquid chlorine to leak on the roadbed within an hour. Police and fire personnel responded promptly, and, wearing self-contained breathing apparatus, aided in evacuation of eighty-nine homes down wind from the leaking car. Several persons were hospitalized for observation, and treated for chlorine inhalation. All recovered without residual effects. It should be noted this is the first spontaneous fracture in a railroad tank car containing chloiine, although rail shipments of chlorine have been made since 1909. Another incident involved evacuation of approximately 13,000 per sons in four towns when about 350 tons of anhydrous ammonia escaped between midnight and 2.30 a.m. following rupture of a 4-in. discharge hose above a dock where a river barge was being unloaded, and the operator failed to immediately stop the transfer. An operator was adding muriatic (hydrochloric) acid to a reaction vessel. Noting a back flow into the charging tub, he investigated, receiving a high concentration of hydrogen sulfide gas directly in his face. Becoming light-headed and dizzy, he closed the valve to the charging tub, and headed for a stairway to the second-floor control 406 Safety and Accident Prevention in Chemical Operations room. Half-way up the steps, he collapsed and fell. Fortunately, his foot caught between the stair treads, which prevented his falling backward down the remaining steps. Regaining consciousness, he pulled himself to his feet and proceeded up the stairs, where help was obtained. Treated at the dispensary, he returned to w'ork without further ill effects. The cause of the accident was because of the level of the solution in the kettle being greater than the height of solution in the tub, permitting a surge of hydrogen sulfide-saturated solution into the tub when the valve was opened to add the acid. Among the preventative measures, and revised operating instructions, was the request to furnish a 5-min self-contained breathing apparatus to be worn like a canteen during this part of the operating cycle, ready for instantaneous use in an emergency. This recommendation would put breathing apparatus in the same class with eye protection, head protection, and safety shoes as devices to be actually worn on the job--not to be frantically sought out in an emergency. Toxic Gases and Particulates Whenever a fire burns in ordinary combustibles, or in situations where the combustion process is less efficient than stoichiometry would suggest, toxic gases plus particulates are evolved. As suggested by the Fire Gases Research Report previously cited, it is impossible to predict in advance what may be encountered in a fire, especially when objects of composition unknown to the firemen are involved, ventilation is not possible. As a case in point, which also illustrates wasted manpower because of the improper use of respiratory' protection, the following is cite g t. P The fire was located in a drying-storage room of steel construction, ing 8 ft by 50 ft by 30 ft, closed by an asbestos curtain at one end. 0f was no possibility of ventilating. The room was located on the sixth a factory, and contained a large quantify of "wood flour" (pulverize dust) contained in 100-lb bags, used in casting ornaments. Fire was by an electric motor in the rear portion of the room. The fire had sm ^ for some time, and this room was heavily loaded with smoke, carbon oxide, and carbon dioxide. The alarm was sounded when heat fina .' j up sufficiently to activate a sprinkler head, which transmitted an - ^ alarm. Since very little smoke was visible external to the drying 1-0 nUickl> first firemen went in without any respiratory protection. They "er.e %ve.irine overcome. Members of the rescue company followed closely behmc ^ ^ universal Type N canister gas masks. These masks functioned ''e n wa? sixth floor outside the drying room, but inside, one of the five me ,, and overcome. The other four heeded the warning sign of "overbreat > ' oVfr- retreated to fresh air before being overcome. In all, thirty firemen w fr us tty fai the Use T the The 2-hr Piom Piece t ETC 03435 3 mm Ufa Respiratory Hazards and Protection 407 come in this multiple-alarm fire, multiple only because all men from the first companies were overcome and adequate respiratory protection was not ordered in the beginning. Fortunately, all recovered. The incident cited should not be interpreted that the canister-type gas mask has no application. Unfortunately, these masks have been used often under conditions for which they were not designed. The term "universal service" is very misleading. Before entering any area with any mask, some reasonable assurance should be obtained that the concentrations of oxygen, toxic gases, vapors, and particulates are within the limits of the respiratory protective device to be used. If any doubt exists, a self-contained breathing apparatus should be used--not a canister-type gas mask. Even with self-contained breathing apparatus certain substances, such as hydrogen cyanide, phenol, aniline, nitrobenzene, and ethylene imine, may be absorbed through the intact skin in sufficient amounts to be toxic. For such exposures a complete protective suit of impervious clothing, plus res piratory protection, is mandatory. Such suits are now commercially available, designed specifically for various hazardous exposures. (Note comments on such suits under air-supplied respirators.) Self-Contained Breathing Apparatus Self-contained breathing apparatus is designed to supply complete respiratory protection in any concentration of toxic gases or in an oxygen-deficient atmosphere. However, as previously noted, certain gases and vapors will also cause systemic poisoning by skin absorp tion, and these require the use of complete skin protection of an im pervious type in addition to respiratory' protection. The early self-contained rebreathing apparatus, which was imported from Europe, had serious deficiencies. Loss of life was reported by users in this country; nineteen accidents were reported involving twenty-six fatalities between 1911 and 1940, because of equipment failure and partly because of improper use of the equipment. Where life lines and standby rescue squads were employed, as recommended, the apparatus was generally satisfactory in the hands of well-trained users. The first self-contained breathing apparatus to be approved by the United States Bureau of Mines was the 2-hr rebreathing type. The oxygen rebreathing apparatus is relatively heavy (39 lb for the 2-hr type), and it is bulky. The models in general use today require mouth breathing with a nose clip to seal the nose, but a full facepiece for these devices has been approved. The United States Bureau ETC 03436 ETC 03437 Respiratory Hazards and Protection 409 generating oxygen breathing apparatus. No formal schedule of ini tial or follow-up training has been established by the Bureau of Mines for this type apparatus, but it has been often observed that the re training was not adequate to insure the safety of a wearer in an emergency. Breathing apparatus of the air and oxygen-demand type is avail able in half-hour, quarter-hour, 10 min, and 7l/2 min rating. Since the ETC 03438 II !) 410 Safety and Occident Prevention in Chemical Operations Bureau of Mines has no approval schedule for any self-contained ap paratus designed for less than a half-hour service, only the half-hour demand (air or oxygen) devices are approved. Although the schedule of work for the Bureau's half-hour rating is exhausting, the fact re mains that large men under extreme stress and exercise have ex hausted an expected half-hour (40 to 43 cu ft) cylinder in significantly less than a half-hour. Other wearers, under less exertion, may obtain up to 45-min service from a similar quantity of air or oxygen. Differing only in whether it is supplied with compressed air or oxy gen, the demand apparatus weighs nearly 30 lb for the half-hour type with a cylinder worn on the back. It is relatively awkward to put into service, and it restricts motion in confined or congested spaces. IVith practice, it may be put on and placed into operation from a mounted backboard in less than 20 sec, but pre-use checks, as recommended by the manufacturers and the Bureau of Mines, should never be neglected. Approximately a minute is required to put the device in full service from a carrying case. The back position of the cylinder makes it difficult to crawl under equipment. Climbing in and out of small openings, such as manholes and areas where obstructions, pipes, and conduits are present, requires special caution. Operation of a motor vehicle is awkward when wearing a cylinder on the back. The demand devices with shorter life overcome some of these objections since the cylinder or cylinders may be worn in front or in a side pack or knapsack. Since they may be worn for extended periods "ready to use," they can be put into instant service for escape or emergency control. The purity of the air or oxygen with which the cylinder has been charged should always be questioned whenever a cylinder is filled or refilled, since other gases, such as pure nitrogen, acetylene, carbon dioxide, and mixtures of gases other than air have been found in "breathing-air" cylinders. Errors in compressed air used for breath ing may be rapidly fatal, and every newly filled cylinder should be checked to insure that it actually contains "breathing air," regardless of the general reputation of the source of supply. Unless the user has his own compressor producing air of an unquestioned purity, no cylinder should be used for breathing purposes until the contents have been checked for purity. Several relatively simple instruments are available for oxygen analysis, for carbon monoxide, and for carbon dioxide analysis. Any high-pressure cylinder may leak, and frequent inspection is I ! necessary to insure that the air or oxygen is actually available for use ETC 03439 ETC 03440 ETC 03441 Respiratory Hazards and Protection 413 manufacturer. . It will not help, as some sources suggest, to enrich the oxygen partial pressure (or percent) of the breathing air. Where synthetic air (made by mixing nitrogen gas and oxygen gas from cylin ders of each) is used, it should always be checked to insure that correct percentages of the gases have actually been obtained. If demand-type apparatus is worn in environments where pressure above 1 atm is present (as in caissons or tunnels under pressure), the service time is reduced as the pressure increases. This is also true of the underwater use of the regular demand-type apparatus; a special modification of this equipment is available for use underwater. Pecul iar effects have been reported when demand and closed-circuit oxygen breathing apparatus were worn under pressure. The use of oxygen in atmospheres above 2 atm absolute pressure, except under clinically controlled conditions, should be avoided, since oxygen produces a toxic effect of convulsions in some people under such conditions. A new technique, knowm as high-pressure oxygenation, or HPO, is being de veloped experimentally and clinically to aid in critical diseases and ailments by saturating the blood with oxygen. For periods up to 12 hr at normal atmosphere pressures, however, oxygen may be used without ill effects by healthy persons. A person in questionable physical con dition should not wear any emergency breathing apparatus unless a physician has approved his use of it as not being contraindicated. Persons who do not have such specific approval should stay away from contaminated air and from water. Highly important in the under water use of breathing apparatus is the necessary continuous breathing during the ascent--at no time should the swimmer hold his breath, and he should ascend no faster than the air bubbles ascend.23 When the supply of air or oxygen has been depleted, the supply in the normal demand-type apparatus cuts off abruptly, and the facepiece must be removed immediately or asphyxia can occur. In re cently engineered devices, warning bells or physical restriction to breathing have been built into the device to indicate the approach of the end of the air or oxygen supply. The seal around the facepiece must be absolutely gas tight in a toxic atmosphere, since in certain demand-type apparatus the facepiece is under slightly negative pressure momentarily during the beginning of the inspiration phase of the breathing cycle. A recent revision in some equipment eliminates the' negative pressure phase of the cycle. Certain demand masks have supplementary attachments with a sep arate regulator and facepiece carried with the main mask for admin istering resuscitation to an overcome person on the spot while still in the toxic atmosphere, where removal to fresh air is not immediately 414 Safety and Accident Prevention in Chemical Operations possible. Another mask has a built-in battery-powered light, which frees the hands from carrying lanterns frequently necessary in erner gencies. In actual use, demand-breathing apparatus of the approved types have certain limitations and disadvantages. 1. Time is required to remove the apparatus from the carrying cae and to put it into service (this may be reduced drastically by wall mounting of the unit so that the wearer can back into the harness attach it, and have the unit in operation in less time). ' 2. The weight and bulk of these devices make movement difficult in confined spaces, and in areas where obstructions, such as pipes wires, and beams are present. 3. Cylinders are difficult to refill "on the job." The need exists for adequate reserves of spare-filled cylinders, or large tanks or com pressors of air, or oxygen for refining used cylinders if large scale use of the equipment is necessary. 4. If oxygen is used, extreme care must be observed to prevent contact with grease, oil, and other combustibles. 5. Pure oxygen inhalation may have complications. Air should never be replaced with oxygen, either in a breathing apparatus, in a ventilation technique, or for any other purpose, without full consideration of the increased potential hazards from spontaneous fire when the oxygen concentration is increased above the 21% in air. Oxygen-enriched air is no substitute for adequate flow rates of air. Cylinders that have been used for air should never be used for oxygen. A flammable vapor-oxygen mixture requires only about onethousandth the spark energy to ignite it as does a corresponding flam mable vapor-air mixture. The resulting fire or explosion is many times more violent. Failure to appreciate these facts and to apply the neces sary precautions have caused many serious injuries. For this reason, it is as important to actually analyze a suspected atmosphere for el evated oxygen concentration as for oxygen deficiency. Obviously flam mable vapors and toxic gases should be checked also. Oxygen an alyzers of the direct reading type are available, and are sufficiently accurate for practical control purposes. Such analysis for oxygen (which will reflect inert gases) should be combined with a check for flammable vapors and gases, and a check for whatever toxic gas or gases is suspected. The second type self-contained breathing apparatus is the oxygen generating breathing apparatus. Now available in two models, one approved for 1 hr and one approved for a half-hour, both devices ETC 03444 ETC 03445 Respiratory Hazards and Protection 417 may expand to a volume which requires occasional "dumping or deliberate release of surplus oxygen to maintain comfort. The self-generating apparatus requires care in starting, especially in subfreezing temperatures. For this reason, it is considered good practice that both the apparatus and the canisters be stored inside a heated building, or in a heated truck cab or automobile, and that the apparatus be thoroughly started above freezing temperatures. Once started completely, the heat generated internally makes it possible to wear the mask in below zero temperatures. Unless the starting is complete, the wearer may be aware of insufficient oxygen and an excess of carbon dioxide during the first few minutes, by a feeling of light headedness and overbreathing, coupled with difficulty in coordination. If such a condition is noted, he should immediately seek fresh air, deflate the breathing bags, and restart the apparatus, until the breath ing rate and the generating rate balance. In the one-hr apparatus, care must be exercised to insert the canister in the correct orientation, and to avoid injury from the torn metal from the top seal. The canister must be brought securely into place after it has been punctured by the sharp point designed into the ap paratus for that purpose. The facepiece should not be put on until the canister is completely seated. A fresh (unopened) canister should always be used. Once opened, a canister will continue to evolve oxygen even after removal from the canister holder. In view of the relatively high cost of these canisters, the temptation to re-use it is great, but re-use even for training must be avoided, and canisters must be promptly destroyed according to instructions on the canister, to protect the safety of the next wearer of the mask. The timer on both models of self-generating apparatus is completely independent of the breathing, unlike the timer on the universal Type N canister gas mask which measures breathing. The timer must be manually set into operation, and it will ring a warning bell when the time has expired, a sign that the canister is approaching the end of its cycle. The disposal of the self-contained oxygen-generating canis ters must be performed exactly according to instructions on the canister. Oil, grease, gasoline, other flammable or combustible liquids or solids must be kept from the canister mouth to prevent an ignition or ex plosion. In a fire, oxygen-generating canisters will explode. Only clean water in large quantities should be used to destroy a canister. The canister must be promptly destroyed to insure that it will not be re-used or accidentally contact combustibles or flammables. For reasons noted under demand-type breathing apparatus, the selfcontained oxygen generating breathing apparatus should not be worn ETC 03446 418 Safety and Accident Prevention in Chemical Operations under pressures greater than two atmospheres absolute. Although the oxygen generating masks have significant advantages, certain dis advantages are recognized. 1. Frequent training is necessary, since these masks are really an extension of the human breathing system, not an auxiliary piece of equipment. Mechanically simple, they are psychologically more complex. 2. Longer time is required to put these masks into full operation, since the canisters are stored separately and must be inserted into the devices, and the starting ritual must be properly and thoroughly followed for absolute assurance. The starting problem has been simplified on the half-hour model only, by the addition of a small self-starting cartridge, which is an oxygen candle permitting im mediate oxygen generation for the first few minutes breathing, while the main canister begins to generate. 3. These devices must be started in uncontaminated areas unless the self-starting feature mentioned above is used. If caught in an area which is contaminated (without the self-starter), the wearer should retreat to fresh air before starting the mask. The apparatus and canisters should be stored and completely started at above-freezing temperatures. 4. Adequate inventory of canisters, similar to adequate inventory of filled cylinders for the demand type, must be maintained. Used canisters must be carefully disposed of exactly according to instruc tions on the label. 5. Canisters are a one-use device. No attempt should be made to re use canisters even after a short use, since there is no way to "turn them off," and no way to measure how much oxygen is remaining in a canister. Wearers have collapsed on the floor while wearing a mask with a used canister during practice sessions. Speech Transmission Inserting any material or membrane between Speaker and listener affects the quality of the voice signal received, and the facepiece of a respiratory protective device is no exception. Measurements have shown that the standard speaking diaphragms cut down greatly on the ability to communicate effectively.25 Recently small batterypowered amplifiers with microphone inside and the speaker outside the facepiece, have become available, and further developments in ETC 03448 420 Safety and Accident Prevention in Chemical Operations Maintenance, Training, and Medical Aspects The maintenance of the respirator, mask, hood, suit, or apparatus in first-class condition is extremely important. An emergency permits no time to attempt repairs or maintenance. Metal parts of apparatus wear, tarnish, or corrode; screws, nuts, and bolts loosen; rubber parts slowly `"age" and eventually crack. Facepieces will take a "set" during storage, and they will eventually reach a point where they can be adjusted properly only with difficulty, if at all. Cylinders, regu lators, and valves on demand-type apparatus must be checked fre quently for leaks and cracks in welds, joints, and connections. Canisters on industrial or universal Type N or chemical cartridge respirators must be replaced whether or not they have been used. Canisters from self-generating oxygen breathing apparatus must be disposed of properly and promptly as noted above. Washing the facepiece wdth an antiseptic solution or soap, rinsing in clear water, and drying will insure sanitation and cleanliness, as well as prolonging the useful life of facepieces. Proper storage conditions and frequent checking for deterioration are so important that respiratory protective equipment should be on the same schedule with fire extinguishers, FIG. 23.23. Respirators and masks in poor condition must be destroyed and not used. 428 Safety and Accident Prevention in Chemical Operation! FIG. 24.1. Full protection is needed during transfers. solid caustic with liquid caustic. While there is a hazard from heat of dilution of 73 or 50% liquid caustic, the hazard is not anywhere near so great as the heat of solution produced by suddenly dumping large quantities of solid caustic into water. In preventing accidents which involve the eyes in chemical process ing, one fairly good rule of thumb is that the chemicals you cannot see are usually the safest. An example would be in filling containers. If the fill pipe ends at a point above the top of the container, the liquid is available to the eyes--that is, it can splash or bounce or in other ways be diverted from the container to the face. On the other hand, if the fill pipe extends into the container there is considerably less chance that the chemical running out of the pipe can reach the face (Fig. 24.1). Prevention of eye accidents in chemical processing does not stop at chemicals themselves. Let us take the simple example of a pipe rack. Where are we going to put it? If it is in the middle of the yard and open at both ends, pipes sticking past the end of the rack present eye hazards to passers-by and to anyone who is getting pipe from the rack. You can automatically reduce this exposure by 50% by the simple expedient of locating one end of the rack against a building or fence. This hazard can be eliminated to passers-by by completely enclosing the rack, so that the exposure is limited to those who actually enter the enclosure for the purpose of obtaining pipe. We can see that any consideration of new processes or even reviews of present processes can profitably include the query, ``What are the I In' potential eye hazards and how can they be reduced or eliminated?" ETC 03457 Eye Safety in Chemical Processing 429 24.2. PREVENTING THE INJURY When we consider the prevention of injury to the eyes we must assume that the accident has occurred or will occur, and that our endeavour is to keep injurious chemicals out of the faces of our employees. In most instances this consists of imposing a barrier between the accident potential and the individual. A familiar example would be the window in a laboratory hood. Indeed, right here we might discuss the hood window, as it is one of the most abused objects in chemical processing. We have all seen hood windows that for all practical purposes were inoperative. Perhaps they were badly etched from months and years of HF determinations. Maybe the glass was old and opaque. Maybe services to the hood, such as nitrogen, were introduced from outside the hood through lines that entered at mid hood levels (Fig. 24.2). All of these things preclude the proper func tion of the hood window', which is to protect the person and confine the fumes except when an operation is actually being performed in the hood. If a study were made of what this work consists of we w'ould probably find that in an 8-hr day not more than half an hour is spent by the chemist in standing with his hands in the hood. But if 430 Safety and Accident Prevention in Chemical Operations the conditions we have just reviewed are present the hood window will remain open the other 7% hr. Lately there is a new trend in hood design which protects the eyes and indeed all of the body except the forearms during the time the chemist is actually working in the hood. This design consists of transparent panels which slide horizontally on an overhead trolley and overlap in front of the hood (Fig. 24.3). The chemist is able to thrust his arms around the edges of the panels, which are not secured at the bottom, and do his work much as he would in a glove or dry box. Remembering that we are talking about preventing the injury, which means imposing a barrier, this barrier can very often be simply part of the process equipment itself. Consider a gage glass on a tank. Let us assume that for some reason this is a gage glass which cannot be guarded, which is fragile, and which is installed at eye level. This clearly constitutes a hazard to the eyes. Now where are we going to put this glass on the tank relative to the area? Usually we would imagine that the gage glass would go at a spot most available to the operator who needs it, which would mean at the point of heaviest travel, such as an aisle. If the glass is put in this position it constitutes a potential hazard not only to the operator but to everybody that passes the tank. If -we put the gage glass on the opposite side of the tank it is harder for the operator to read it, but it constitutes practically no hazard to anyone but the operator. FIG. 24.3. Horizontal panels for hoods can provide eye and face protection even while working in hoods. ETC 03459 5r 1 Eye Safety in Chemical Processing 431 In investigation reports on eye injuries in chemical processing, perhaps one of the commonest phrases is a variation of, "He turned the wrench and acid squirted out." The chemical industry has learned that this type of accident, which we call a line-breaking accident, is very nearly 100% preventable, because we can impose barriers. A barrier can be as simple as an old vinyl raincoat. The bolts are loosened on the flange a quarter turn or so and then work is con tinued with a raincoat or rubber sheet between the worker and the wrench and the flange. If the product in the line squirts out it is going to be deflected by the barrier. Another barrier can be as primitive as a bucket of water. How many of us realize that something as simple as a plug cock, taken off a process line, can still constitute an eye hazard. If we examine drawings of plug cocks or many other different types of valves, we will notice that in the closed position in a line considerable product is contained within the valve. If the line is drained and the plug cock removed, the product goes right along with it. If the valve is sub sequently opened, as for example in the act of working on it in the machine shop, the product can squirt out. One simple method of preventing this type of accident is by insisting that the valve be in an open position before it is removed from the line, and that it be immersed in a bucket of water and opened and closed several times before further work is done upon it. 24.3. GUARDING THE PERSON The next line of defense in eye protection to some degree resembles the second, that of imposing a barrier. In guarding a person we provide a barrier on the person himself. This consists of something in front of his eyes such as safety glasses, mono-goggles, face shields, or masks. The eye-protection program of the Allied Chemical Com pany works very well, and it could be easily adopted by almost anyone interested in preventing eye injuries in the chemical processing industry. The program is based on one simple rule, which calls for the wearing of safety glasses by everyone all the time. These safety glasses are conventional frames without side shields and are piano for those people not requiring prescriptions. For people wearing pre scription glasses we provide prescription safety glasses. All these glasses are provided at no cost, and we have no limitations on the number of glasses per person per year. We think there are some very definite advantages to this program, 432 Safety and Accident Prevention in Chemical Operations even though we accept the fact that safety glasses provide only about 90% protection as compared to cup goggles or face shields. We also use face shields and cup goggles, and they will be discussed later. We think that safety glasses when worn all the time dispense with two serious objections to cup-goggle programs. No workman can be ex pected to wear cup goggles, mono-goggles, or face shields eight hours a day. In plants which rely upon this type of eye protection, some system must be evolved to determine when the workman must wear goggles. This determination seems to have taken three separate courses: the concept of an eye protection area, the decision of the employee's foreman, or the decision of the workman himself. In a so-called "goggle area" signs are usually posted to inform that goggles must be worn in this area. However, this does not protect the people working or passing adjacent to this area, and historically people have suffered eye injuries when they have entered the area, as they put it, for a short time. Programs which depend on the foreman or the worker to determine whether goggles should be worn really place too much responsibility on the foreman or workman. Probably neither of these individuals is competent 100% of the time to say whether a significant eye hazard exists. Furthermore, this type of program leads to arguments between management and the workman, usually with agreements that are only temporary. The introduction of a 100% safety-glasses program is not something which can be done overnight. One usable method is to begin by an nouncing to the supervisory staff that at a future date safety glasses will be introduced, first on a permissive basis, and later on a mandatory basis. At this time request the foremen to begin wearing safety glasses and to equip wearers of prescription glasses with prescription safety glasses. Even at this early stage you will encounter some resistance from the foremen. This resistance can be met in many ways, such as pointing out the frequency of eye accidents in your company, and comparing safety glasses with other safety equipment commonly in use, such as rubber gloves, aprons, and gas masks. When the workmen are equipped with safety glasses resistance and high initial cost will be encountered. The cost will come from the fact that employees are simply not used to wearing safety glasses and will break them, lose them, or leave them at home. We should be prepared to replace these glasses and initially there will be a need to carry a comparatively large inventory. Later on supply problems will diminish considerably, as the employees become accustomed to wearing glasses all the time. Glasses which are worn on the nose do not get lost or Eye Safety in Chemical Processing 433 broken. The way glasses get lost or broken is by being sat on, falling out of the pocket, or getting knocked about in a tool box. Eventually some unexpected dividends will be found in a 100% safety-glasses program. One of them is the psychological reaction of the workman who wears safety glasses. By the very act of his equipping himself with a protection device he becomes more safety conscious and will perhaps unconsciously consider other hazards in the plant more closely. Furthermore, a workman who wears safety glasses is inclined to kid a fellow workman who for some reason has left his glasses off. Another dividend consists in a reduction of offthe-job eye injuries. As workmen become used to safety glasses and convinced of their value they will wear the glasses off the job when doing things that carry a degree of risk to the eyes. This is particularly true on do-it-yourself projects. There are frequent testimonials from workmen who say that their eyes were saved by their glasses in accidents involving power tools in their own work shops. A good eye safety program does not stop at safety glasses. Some operations require more complete protection. For example, in line breaking operations the minimum requirement should be a full face shield. This should be worn over safety glasses in order to protect the eyes when the shield is removed or momentarily raised (Fig. 24.5). Chipping, welding, and other high-hazard jobs likewise require additional protection such as mono-goggles or cup goggles. These additional requirements are best spelled out in safety manuals or posted in high hazard areas. Full hoods may be necessary (Fig. 24.4). 434 Safety and Accident Prevention in Chemical Operations I would like to say a word about the future of eye protection pro grams with relation to safety glasses. Better glasses can be made They can be better fitted, and delivery schedules can be improved It is obvious that some standardization of safety glasses is needed At the present time not all safety glasses parts are interchangeable For example, there are 3, 5, and 7 barrel hinges, and variations in the shape of lenses. In a large chemical plant there may be two or three different brands of glasses, and the lack of standardization makes it difficult to replace broken parts. As for delivery schedules, these are not a problem on piano glasses, but delivery promises, so far as prescription glasses are concerned, have to be taken writh a grain of salt. We are within our rights to insist upon minimum periods be tween placement of orders and delivery of prescription glasses. Concerning the fitting of safety glasses, it is obvious that the better they are fitted to the individual the more likely he will wear the glasses all the time and the more comfort he will enjoy. There is a trend toward initial fittings by oculists or other members of the pro fession. These services cost money but they increase eye protection and additionally they relieve the busy safety engineer from the purely mechanical job of fitting and dispensing glasses. 24.4. MINIMIZING THE INJURY We come at last to the important subject of treating the eye injury after it occurs. In a chemical plant the answer, which is deceptively simple, is water. The first-aid measures for a chemical injury to the eye consist solely of the application of water, lots of water, and for a long time. The best place to administer this water is as near to the scene of the injury as possible. This calls for lots of hoses as a minimum, many safety showers as a medium, and adequate eyewash fountains as an ideal. (We personally like home-made eye-wash fountains.) A simple design consists of three conventional shower heads each mounted 90 apart and at about waist level (Fig. 24.6). Such an eye-wash fountain takes care of the entire face and the position of the face relative to the ground is such that it provides for a maximum of dilution and run-off. There is an excellent arrangement which protects bench workers. This consists of nothing more or less than a kitchen type of hose spray on a reel, with a spring-loaded nozzle at the end. If materials are accidentally introduced into the eyes the bench worker need only reach for the nozzle, pull it toward him, and direct the stream into his face. Following the use of water at the point of injury it is usually necessary to continue eye irrigation in the first-aid room. Very often other parts of the body are involved, and many first-aid rooms use tubs for immersion washing. These tubs should include spray hoses similar to home-shampoo hoses so that the eyes and head may be irrigated at the same time. Some workers may be exposed to chemical burns of the eyes away from your plant. Examples would be truck drivers and those per forming services at customers locations. Trucks should carry supplies of emergency water, in the glove compartment or in 1 or 5-gal cans kept in the cab of the truck. Lately an ideal place to keep water has been found--in acid tank-truck transports. These transports are equipped with roll-over bars. The bars are actually hollow7 compart ments, w7hich can be filled with water and fitted with a nozzle. As for w7ork at customer locations, your people should be instructed to look for emergency sources of water as soon as they enter the location, and to report to you if such sources of water do not exist. It has been found sometimes that customers receiving products do not have safety showers near the point of unloading, and also found that uniformly the customer has been cooperative in providing such showers when requested. Eye-w'ash fountains and showers should be periodically tested and a record of such testing maintained. No valves should be permitted in these lines. Fountains and showers in cold climates can be pro tected against freezing in various ways, such as using warmed circu lating water, installing the piping below the freeze line, or using dry pipes from a warmed building (Fig. 24.7). Showers and fountains should be marked writh signs and distinctive painting, and it is a good idea to use a green light at each shower. Some companies are using "drills" because it is probably against instinct to get under a show7er with your clothes on. We have seen many instances in which a man T contaminated with a chemical splash would use a hose or even a basin instead of an easily available safety shower. Drills, which might take the form of getting under a shower just before quitting time, will condition the workman to use a shower when he needs it. A final word is necessary relating to water substitutes and the fight we must make against them. In almost any plant individuals are found who feel that certain types of chemical burns are best treated not with water but with special solutions. For example, some people want to treat acid burns with sodium bicarbonate solutions or weak ammonia. There are serious deficiencies in these routines. For one thing, the so-called special solutions are never as readily available as water, or in the large quantities necessary to flush away the offending chemical. Even more important, the so-called neutralizer very often produces a secondary injury in that in the process of neutralization a new chemical product is formed in the ocular tissue. This not only increases the injury but makes the treatment more complicated as the physician who ultimately sees the patient will find it necessary to remove the chemical which has been formed before he can treat the injury. Chemicals splashed into eyes can enter behind contact lens and do grave damage before the lens can be removed. Dr. D. J. Kilian, of Dow Chemical, has demonstrated this mechanism in experiments using fluorescein stains. Workers should be forbidden to wear contact lens when exposed to chemical splash; alternatively, they should wear cup goggles. To summarize the modern concept of eye protection in chemical processes, we have four lines of defense: to prevent the accident, to etc 03465 Eye Safety in Chemical Processing 437 prevent the injury, to guard the person, and to minimize the injury. These lines of defense are interdependent and each must be carefully planned for maximum eye safety. REFERENCES 1. R. E. Joyner, "Eye Protection in the Chemical Industry. A Report on Six Year's Experience," Indust. Med. and Surg., 28, 174-177 (April 1959). 2. \Y. M. Grant, Toxicology oj the Eye, C. C Thomas, Springfield, Illinois, 1962. 3. Toxic Eye Hazards, Manual prepared by the Joint Committee on Industrial Ophthalmology of the American Medical Association, and the American Academy of Ophthalmology and Otolaryngology, No. 494, National Society for the Prevention of Blindness, New York. New York. No. 494, 1949. 4. Eyes in Industry, Guide to Better Industrial Vision Testing, No. P-119, Na tional Society for the Prevention of Blindness, New York, New York, 1963. 5. Clark Holmes, Director of Surveys, Guide to Occupational and Other Visual Needs, P. 0. Box 5310, Metro Station, Los Angeles 55, California, 1958. 6. "Use of Contact Lenses in Industry." American Medical Association, Council on Occupational Health, JAMA 188, 397 (April 27, 1964). 7. American Standard Safety Code for Head, Eye and Respiratory Protection Z2.1-1959, American Standards Association, New York. 8. Plastic Eye Protectors, Final Report, American Society of Safety Engineers, Engineering Section, National Safety Council, Chicago, Illinois, 1947. 9. I. W. Silberstein, "The Fracture Resistance of Industrially Damaged Safety Glass Lenses, Plano and Prescription--An Expanded Study," American Jour nal oj Optometry and American Academy oj Optometry, 41, 4, 199-221 (April, 1964). 10. Ralph Stair, Spectral-Transmissive Properties and Use of Eye Protective Glasses, United States Department of Commerce, National Bureau of Stand ards, Circular 471, For sale by the Superintendent of Documents, U. S. Govern ment Printing Office of Documents, U. S. Government Printing Office, Washington, D. C. 11. A. H. Keeney, Lens Materials in the Prevention oj Eye Injuries, Charles C Thomas, Springfield, Illinois, 1957. 12. W. A. S. Denham, "Safety Equipment in the Lab," Research Development, Vol. 15, No. 9, pp, 24-28, Sept., 1964. 25 Other Personal Protective Equipment H. H. Fawcett T In addition to previously discussed respiratory protection and sight conservation (eye protection and care in the broader sense), several other types of personal protective equipment play important roles in safety with chemical operations. As with other "safety devices," it must be emphasized that although these items do not reflect the true spirit of "accident prevention" (for if the accident or unwanted incident were completely prevented, no protection would be needed for the individual), they are an important "second-line" of defense, whereby the injury or exposure is either prevented completely, or is minimized in its severity. Whenever an unwanted incident or accident does occur, the presence in place of personal protective equipment of the proper type, designed, manufactured, sold, and accepted by the wearer through adequate training, may easily determine whether or not injury occurs. Since the need and application for personal protective equipment are even more varied than the wide diversity of the equipment itself, this chapter will outline a few fundamentals and limitations, with the intent of encouraging the reader to an independent analysis in depth, in relating the equipment,'with its inherent limitations and advantages, to his specific needs. It should be pointed out that the impeccable integrity both of the salesman and the manufacturer whose products he represents are of paramount importance in specifying, discussing, 438 ETC 03467 Other Personal Protective Equipment 439 scheduling, purchasing, or applying such equipment. Unlike the respiratory protective devices (many of which are covered by test schedules of the United States Department of the Interior Bureau of Mines and the United States Department of Agriculture, which assure at least minimum standards have been met by the devices), no generally accepted schedules or testing by impartial agency cover these devices. This statement is made to emphasize that, while certain American and government standards exist for many of these devices, the potential user must accept the word of the manufacturer that they meet these tests, or conduct tests at his own expense. Control by some recognized completely independent agency or testing group is critically needed, especially in certain phases of personal protective equipment. Head Protection For chemical operations, especially in facilities with extensive overhead piping, tanks, columns, and other equipment which oc casionally leaks or ruptures, some form of head protection, preferably including a wide brim or visor-peak, is indicated and frequently used. This protection may range all the way from a felt hat or a leather cap, both of which give considerable protection from chemical splashes, to bump caps and hard hats especially designed to furnish head pro tection. (The term bump cap is used to describe a relatively new head protector which furnishes much less protection against falling objects, but gives a satisfactory protection against many objects, such as pipes, conduits, and other obstacles encountered in a complex en vironment. Since the bump cap is difficult to distinguish from a hard hat by superficial observation, the reader is encouraged to consult the manufacturer on this point.) At one time hard hats usually referred to a specific type of headgear, either of laminated fiberglass or of metal, but in recent times a be wildering variety of hats and caps have appeared. To further com plicate the field, a few years ago the engineering department of a highly respected university reported tests they had conducted on a few hard hats, with conclusions that evoked considerable discussion about the efficiency of the hats. A wide variety of plastics are now available which have a high resistance to impact, such as the polycar bonates, and these are being used to make hard hats, bump caps, baseball caps, and firemen's hats. Further appeal is given by the rainbow of colors, which can be used practically to designate the craft, working group, or security clearance to which the wearer has been 440 Safety and Accident Prevention in Chemical Operations assigned. In selecting hats for use in a chemical operation, it js suggested that some of the less glamorous and subtle aspects of hats should be explored, such as the exact distinction between hard hats bump caps, and their applications, that the electrical conductivity be fully explored (nonconductive hats should withstand 15,000 volts AC 60 cycles, for 1 min with leak-through and leak-over not in excess of 8 milliamperes, while insulating hats should not fail below 20,000 volts), the reaction between the chemicals and mixtures of chemicals to which the hat will be exposed (no plastic or metal is completely inert to every chemical in all concentrations), as well as the design and construction of the suspension mounting, and, if the hat is to be worn in cold weather, the possible ease of attachment of ear muffs or wind barricades to prevent frostbite. Ear Protection Several states have recently awarded workmen's compensation benefits for partial loss of hearing, allegedly caused by occupational noise. This is only one manifestation of a growing awareness of noise in our complex civilization, as radio, television, stereo, PA systems, outboard motors, power mowers, jet engines, rocket blasts, and super sonic booms compete for our attention. The chemical industry is not without noise problems, although compared to other industry, it is relatively quiet. Agitators, grinders, mixers, pulverizers, com pressors, fans, blowers, and other equipment produce noise; at what point this noise is objectionable or harmful requires careful analysis. The analysis and control of noise frequently requires an acoustics engineer (who supplies fundamental information), an industrial hygienist (who makes the measurements using equipment specified by the acoustics engineer), and the plant physician or a consultant specialist who can interpret this information into meaningful terms as it relates to the employees. Where possible, noise should be reduced or eliminated at the source using engineering methods which have been proven. This would in clude attenuation by isolation or baffles and other means. However, for the many operations where it is economically or technically im possible to control the noise at the source, some form of ear protec tion may be considered by the physician, using the knowledge and data to aid in determining each problem in terms of the specific employees who will be affected. At the same time, the medical department might institute a regular program of audiometric testing, which can be used r Other Personal Protective Equipment 441 to periodically determine whether or not a hearing loss is or is not occurring, either from occupational or nonoccupational causes. Once a program is decided upon, the medical department still has a key role--the proper fitting of devices (ear plugs, ear muffs, helmets, or the combination) so they are exactly matched to the individual, who must understand their importance. This is highly important if the program is to succeed. It should be noted that ear plugs, which are ETC 03470 mm* 442 Safety and Accident Prevention in Chemical Operations the simplest and least expensive control measure, have only a limited ability to attenuate sound, and for higher sound levels, they are often supplemented by specially designed muffs, and, in extreme levels, by a helmet with built-in muffs. To facilitate voice communication with muffs and helmets, built-in earphones and attached microphone's permit the use of telephones or radio equipment (Fig. 25.1). The field of hearing protection is highly technical, and the reader is encouraged to seek specialized assistance from acoustic, medical, and industrial hygiene specialists who have specialized in this field, before embarking on any program of evaluation or control. Interest in this field doubtlessly will continue to increase. Gloves, Aprons, and Specialized Clothing Since many chemicals are corrosive to the skin and/or toxic by skin absorption, an effective barrier between the skin and the chemical in troduces a highly desirable "second-line" of protection. As with other items, the more complex the device the more resistance may be ex pected in having it actually used, but an understanding of why is often the secret to securing acceptance. In this brief discussion, the virtues of various devices will be assumed, and the less-appreciated aspects mentioned. Not all rubber or plastic used in gloves, aprons, or other clothing are suitable to the exposure from the specific chemical which may be encountered. In investigating gloves, aprons, or other clothing, the manufacturer should be consulted and asked to submit in writing the recommendations and suitability of the material for protection against the chemicals in the concentration, combination, and temperatures which will be encountered. Many manufacturer's tests are unbeliev ably incomplete and misleading: to recommend a glove for "sulfuric acid" is meaningless unless the concentration of the acid is specified, for battery acid and concentrated sulfuric acid differ widely in their action on gloves, although both may properly be listed as sulfuric acid. Temperatures, at which the gloves, aprons, and clothing will be used, as well as the temperatures of the chemicals to be contacted, should be questioned. Some rubber and plastics are unsatisfactory at extreme temperatures, both cold and hot, within the ranges actually encoun tered in use. Gloves, aprons, and other clothing are made in a wide range of sizes and styles. Unless an item fits properly and permits the proper work actions, including the highly important finger dexterity, they may actually introduce additional hazards. This is especially true ETC 03471 Other Personal Protective Equipment 443 if impervious plastic or rubberized cloth is used for clothing which prevents normal body "breathing," and hence becomes so hot and humid that working efficiency is reduced drastically. For this reason, the air-ventilated suits, which introduce supplied air both for cooling the suit as well as for respiratory use, and the more recently intro duced ventilating suits, inspired by the astronaut suits, in which liquid air (not liquid nitrogen or liquid oxygen) is used in a similar manner, may be of great practical significance as they are developed further and as their widespread need would suggest. (In this con nection, it may be noted no Bureau of Mines schedule currently exists for air-supplied suits or for the liquid-air breathing systems. In view of the difficulty which has been encountered in the past in con trolling the exact composition of "liquid air," it is hoped considerable care would be employed before these become widely used.) Maintenance of gloves, aprons, and clothing must be of a high order, just as with respiratory protective equipment. For example, a small pin-hole leak (too small to note visually on casual observation) may permit entrance of sufficient amounts of corrosive or toxic agent to cause injury. This has been demonstrated many times with dilute (10 to 20%) hydrofluoric acid, which has no immediate warning prop erty, but whose delayed effects may be noted several hours after the unsuspected contact from the defective glove. Checking of rubber or plastic gloves by inflation with air, immersing in clear water, and noting the air bubbles which indicate a leak, should be a frequent inspection procedure with gloves used with acids and other harmful substances. To use a defective glove is to have a false sense of security. Talc sprinkled into the gloves after each use will prolong the life as well as comfort of the glove. Safety Footwear Safety shoes and safety boots have become-an accepted part of many chemical operations, perhaps because the intrinsic value of the steel safety cap, which weighs only an ounce, has been so dramatically demonstrated. In addition, safety shoes and boots have become at tractive and comfortable, and they represent an excellent value. Part of this attractiveness has created some discussion in that shoes which offer somewhat less protection for heavy use (such as safety shoes with webbing and open stitches) are sometimes used where regular standard safety shoes are indicated. In spite of this, the major shoe manufacturers have continued to develop an ever-widening acceptance. Of special interest to chemical operations are safety shoes known as 444 Safety and Occident Prevention in Chemical Operations "powder shoes" which have no magnetic metal in their construction and hence cannot make a spark due to frictional impact, "conductive shoes" which have sufficient built-in electrical conduction that they permit static electricity accumulated on the body and clothing to bleed harmlessly to ground (assuming the floor or ground is sufficiently con ductive to permit this!, and acid-oil shoes, either all specialized rubber construction or with special oil-acid-moisture resistant soles and heels, especially made to be worn in liquid-contaminated areas. Since shoes are the one item of safety clothing which may be worn by nearly everyone (unfortunate high-fashion designers have yet to produce safety shoes for ladies which are acceptable to their vanity), availability of safety shoes is of importance in securing acceptance. Recently, the "shoemobile" method of marketing was introduced suc cessfully, which permits even small plants in relatively isolated areas to be serviced regularly by a wide variety of off-the-shelf shoes, with no inventory problems for the plant. This selection, coupled with payroll deduction permitted in many plants, and the fact that safety shoes are a deductible item for federal income tax purposes, as well as the need for foot protection in domestic situations, such as power lawn-mowers, has stimulated interest in safety shoes as desirable additions to the "second line" of defense. Conclusion Personal protective equipment has a place in any comprehensive safety program, but the success of its use will be the degree of accept ance. Unless it is actually worn in place at the time of the unexpected incident, it is worthless. For this reason, it requires extreme care in selection, maintenance, and, most important of all, sufficient under standing by the wearer so it will be used at all times for its intended purpose. Permit Systems Jeremiah J. O'Driscoll The repetition of accidents and injuries in performing certain tasks or under certain conditions emphasizes the need for a positive control of the operation and the spelling out of necessary actions to accomplish the work safely. Permit systems have been developed as the most satisfactory method for insuring the proper control and safe perform ance of repeated operations which have been proven to be hazardous. Maintenance or repair operations which involve separate sections of a plant, or when different supervisory areas could be affected, must include a positive system of notification and approval by all con cerned personnel to be accomplished safely. The permit system, or a form of licensing and documenting in writ ing, is a convenient method of preparing a basic standard operating procedure, spelling out the task, personnel, equipment, method, loca tion, the precautions to be taken, and the time for an operation to be performed. The permit system offers one of the best methods to meet all the various conditions required for making difficult operations safe to perform. Several types of permit systems have been developed to various degrees of detail over a period of time by different industries depending on their particular needs and experience. Frequently, it is practical to combine the requirements of several permits on one printed form to reduce the number of forms needed and to simplify the administration for a comprehensive permit system. The use of permits has several advantages that could not be obtained 445 446 Safety and Accident Prevention in Chemical Operation* with certainty in any other manner. They provide written information and instructions on hazards to be avoided in the operation, and these items must be reviewed by the person responsible for doing the work They can insure that proper tests and preparations are made prior to to starting the work. They can restrict the performance of the work to personnel who are known to be adequately trained. They can in sure adequate notification of all parties interested in the operation prior to its starting. They can clarify the responsibility for the opera tion; and the signing of the permit insures that the person is satisfied the proper conditions are being met. All persons signing the permit have their responsibility for the safety of the operation emphasized. They also provide a written record of the operation, including those who were involved in authorizing and supervising it. In general, thev can provide an unusual degree of control over the operation to be performed. The many advantages possible from the permit system would seem to warrant its continued expanding use as an important device to improve the control and safety of normally hazardous op erations. The numerous types of permit systems that have been developed emphasize the large variety of operations that can be improved by their use. In general, all of these permits fall into one of several general types of permits such as hazardous operation permits, hazard ous work area permits, special hazard permits, and equipment operat ing permits. The most generally used permits are for hazardous operations such as "hot work": welding and cutting, or the use of open flames; and for "tank entry": the opening and entering of tanks, voids or vessels by personnel. There are numerous additional types of spe cialized permits which have been developed in various industries to improve the performance of operations that are particularly hazardous. Permit systems frequently used may be grouped in the various gen eral types of permits: Hazardous Operation Permits Hot work (welding, cutting, open flame) Tank entry (vessels, voids, closed spaces) Line breaking (opening) Disposal operations Testing operations (explosives, propellants) Excavations After-hours operations Hazardous Work Area Permits Explosives building work Permit Systems 447 Acid-area work Flammables-area work Special Hazard Permits Toxic materials Matches and lighter Equipment Operating Permits Material handling equipment or vehicle operating (vehicles, fork lift trucks, hoists, graders, etc.) Sprinkler-valve closing permit 26.1. HAZARDOUS-OPERATION PERMITS Hazardous-operation permits usually cover those operations which are repeated occasionally by various personnel and have repeatedly proven to be unusually hazardous if certain precautions and measures are not taken before starting the work. Hot Work (welding, cutting, open flame) Fire has been the greatest universal hazard to which chemical opera tions are exposed. Numerous times uncontrolled welding and cut ting operations have been the source of fire in all types of industrial operations. These activities can be closely controlled by an effective permit system.'2-3 There are many areas where smoking, open flames, and welding and cutting operations are prohibited during normal op erations because of the nature of the exposure or the large damage potential of the area. In these areas a permit system can provide for the controlled use of heat or open-flame sources. The approval and granting of a "hot work" permit is usually re stricted to a senior supervisor of the area involved and for a limited time period. Most of these permits actually require inspection of the area and approval by the plant safety supervisor, the fire chief, or their representatives, and the local area supervisor. Figure 26.1 is a sample of a "hot work" permit form. The issuing of the permit is usually the responsibility of the area supervisor, who must inspect the area and verify that the following measures have been taken: 1. The equipment has been emptied and cleaned and all flammables, combustibles, or toxic materials have been removed from the area, and those items that cannot be removed have been shielded or wet down. ETC 03476 ETC 03477 Permit Systems 449 signs the permit and authorizes the work to be performed. Upon com pletion of the work, the area is inspected by the worker and the "fire watch" to insure that there are no smouldering or incipient fires started in the area. They then sign the form certifying the work has been completed safely and return it to their supervisor. He, in turn, for wards it to the area supervisor and to the plant engineer's office or the safety department. Work postponed beyond the period of the permit usually requires reissue or extension of the permit after a review of the area and condi tions by specified personnel. Fires, or significant changes of conditions in the area during the work, usually voids the permit and reissue is required. Tank Entry (opening or entering vessels, voids, or closed spaces) The numerous serious or fatal incidents involved in tank entry op erations have emphasized the urgent need for close control of these operations.4'5-6 (See also Chapter 23.) The approval and granting of a "tank entry" permit is usually restricted to a senior supervisor of the area involved and for a specified time. Figure 26.2 is a sample of a typical "tank entry" permit form. Prior to approval and use of the "tank entry" form, the area supervisor must insure that the area and equipment have been inspected and that the tank has been emptied, washed, and flushed, and that all lines and drains have been disconnected and blanked off. All equipment, such as agitators or mixers, must also be disconnected or locked out. The work-crew supervisor is also responsible for inspecting the area and equipment and must insure that the following items have been accomplished: 1. Adequate tests have been made of the residue and atmosphere to insure that it is safe for entry. These tests usually include tests for flammable gases or vapors, oxygen content determination (mini mum of 18%), and toxic materials exposure. Tests should be re peated at intervals to determine if an unsafe condition develops while work is being performed. 2. Personnel are properly equipped and clothed for work in the tank, and adequate forced ventilation has been provided. (Several air changes per minute are desired.) Equipment may include: Air line masks or self-contained breathing apparatus Life lines 450 Safety and Accident Prevention in Chemical Operations REYNOLDS PLANT ENCLOSED VESSELS B'ORK PERMIT For one or more of the following Pipe Fitting--------------------------------Permit Electricians -- _ __ _ ______ No Machinist __ _ _ Carpenters _ Labor Crew __ _ _ __ _ _ jop Descript Dept. APPROVED ev Dept Supecv isor ot Foteroan; Maim Supvr Leadman Foreman PROTECTION CHECK LIST CHECK ITEMS INSPECTED l All Employees of precautions olved have been informed 2. AH lines dm lines blanked vnd pressure released ami } Tank neouaLied, before tmenng 4. Necessary Safety Equipment on hand and used 5- Switch Lockout used 6 Arrangements made to thoroughly check area after |ob completed _______ ' Man stationed outside ot tank ahifo wort Flammable Vapors Gas Oxvgen Content ' 16" mm FRONT BACK FIG. 26.2. Enclosed vessels work permit form. Acid suits or protective clothing Explosion-proof lights (extension lights should be low7 voltage) Rescue equipment 3. A safety watch or observer is assigned and is familiar with his duties and the proper actions to take in an emergency. The "safety ob server" should be stationed in a position outside the tank to observe the personnel in the tank at all times. When the responsible supervisor is satisfied that all of the appropri ate items above have been accomplished, he then signs the permit and authorizes the work to start. Figure 26.3 is a combined form of a "hot work" and "tank entry" permit. Line Breaking (opening) The breaking or opening of pipe lines, pumps, or attached equipment has been a continuous source of serious injury and incidents in chem- ETC 03479 ETC 03480 452 Safety and Accident Prevention in Chemical Operations ical operations.5 Ail of these operations should be subject to a permit system to insure careful supervision and safe performance. Figure 26.4 is a sample form for a "line breaking" permit. All lines to be worked on should always be assumed to be loaded and under pressure. The following measures are usually followed in issuing these permits: 1. The issuing of a permit should be limited to the supervisor of the area who is completely familiar with the system, and who has veri fied the proper line to be opened and that all steps possible have been taken to drain and vent the line and any connected pumps valves, and tanks. All pumps on the line should be locked out and all gages and sight glasses should be checked for zero readings. 2. The personnel assigned to do the work should be properly equipped and clothed completely with protective equipment as if the line were going to vent or spray when broken. The nearby area should be enclosed with a barrier rope and signs to exclude personnel not involved in the operation. 3. The procedure for actually breaking the line should be reviewed with the persons who do the work. The placement of a deflector of lead or a suitable material over the flange joints is usually required for the initial cracking of corrosive or toxic material lines. Adja cent nuts and bolts are loosened first, slowly, and in the most acces sible position where they can be retightened quickly if necessary. 4. Emergency equipment and materials should be checked and avail able in the immediate area. Safety showers, hose lines, fire extin guishers, neutralizers, or other emergency materials should be on hand and ready for use. Emergency actions to be taken should be reviewed by the supervisor with the personnel involved. 5. Removed sections and involved valves or parts should be handled carefully until they are inspected for trapped material or residues and are flushed. Lines that have caked or contain residues that can not be cleaned immediately should be tagged with warnings identi fying the contaminant or condition until they can be properly decontaminated. 6. Broken lines remaining in place should have all openings blanked off to prevent later drips or spills. Disposal Operations The disposal of hazardous waste materials is frequently the source of accidents and injuries. This is probably because of the general ETC 03482 454 Safety and Accident Prevention in Chemical Operations feeling that it is a simple operation not requiring supervision and can be done in the most convenient manner. The frequency of serious injuries in these operations emphasizes the need for adequate supervi sion, careful planning, and development of safe procedures which take into consideration all the characteristics or peculiarities of the materials involved.4 Requiring a permit for these operations can insure that only trained personnel are used and that adequate forethought has been given to the methods and facilities to be used in disposing of each material. The permit form (Fig. 26.5) usually specifies the number of personnel involved and the manner in which each material is to be disposed. It can also be used as a standard operating procedure in spelling out specific measures to be taken at the site. These may include: Fire-equipment standby and the checking of water or phone connec tions. Flying of warning flags or the sounding of warning signals. Notification of security, fire, or administrative department personnel. Inspection of the area for intruders and perimeter control. Inspection of the area at the conclusion of the operation and shutdown. Testing Permit (explosives and propellants) Testing operations involving explosions or possible explosions, fires, the release of toxic materials, high-noise sources, or other possible hazardous reactions can be effectively controlled by a permit system. The permit can insure adequate warning of nearby personnel and that proper procedures are followed to reduce the hazards involved to the absolute minimum. The form and requirements of the testing permit are usually similar to those for the disposal of hazardous materials. Testing operation permits may also be expanded to include a Standard Operating Procedure, when tests are of a similar nature and are repeated frequently. The addition of the Standard Operating Pro cedure to the permit form greatly improves the effectiveness of both measures and insures that all responsible personnel are familiar with all requirements and procedures. Excavation Permit In plants with numerous underground systems, such as pipelines and power conduits, or where soil conditions are unstable or possibly con taminated, digging or excavation operations are frequently controlled Permit Systems 455 DISPOSAL PERMIT No. 001 Mr.___________________________________ , foreman, is authorized to dispose of the following materials in the manner indicated: Method Location The procedures posted at the burning ground and disposal area must be followed in detail during these operations. Personnel Authorized #_____ Time Date (Supervisory FIG. 26.5. Disposal permit form. by a permit system.7, * 8 An "excavation permit" can be used to insure that any of the following desirable measures have been or will be taken: 1. The drawings of the area have been checked for existing lines and the plant engineer's office agrees to the operation. 456 Safety and Accident Prevention in Chemical Operations 2. The soil has been checked for contamination by flammable or toxic materials. 3. The area is properly posted and barricaded or roped off. 4. Proper shoring materials and methods are going to be used if the excavation exceeds a certain minimum depth, usually 5 ft. Figure 26.6 is a sample "excavation permit" form. After-Hours Operation Permit Two instances when a permit system can prevent difficulties or com plications are when unusual operations are conducted after normal working hours, or when equipment must be operated unattended over night. The permit can provide information as to the responsible parties and spell out emergency actions to be taken if necessary. It can also spell out any unusual hazards involved such as flammable or toxic materials. The permit form should provide a copy to be placed on or attached to the equipment and a copy to be sent to the guard force for informa tion. Before approval of the permit by the area supervisor, it is usually desirable to have a review of the setup by safety personnel. Figure 26.7 is a sample form for an "after hours operation permit." 26.2. HAZARDOUS WORK AREA PERMITS Work areas where hazardous materials are processed or stored are frequently restricted to operating personnel only. Repair and main tenance activities in these areas can present an undue hazard to some operations as well as to the maintenance personnel unless necessary measures are taken to eliminate or isolate the potential hazard. Several types of "Hazardous Work Area Permits" have been developed by organizations to provide a means of controlling all opera tions in high hazard areas other than the normal production activities. All "hazardous work area permits" will require the approval of the area supervisor, who must also certify that all hazardous materials have been removed from the work area and that any necessary de contamination procedures or tests have been accomplished. When the planned work includes hazardous operations such as hot work or tank entry, which in themselves require a "Hazardous Operation Permit," these permits should also be approved by the area supervisor. Permit Systems 457 EXCAVATION PERMIT DATE _______ EXCAVATION FOR: No. 001 LOCATION: CAUTION: Contained with the excavation area are: SPECIAL MEASURES TO BE TAKEN: Area to be barricaded and marked. Shoring required if 5' depth exceeded. Authorized By Plant Engineer FIG. 26.6. Excavation permit form. 458 Safety and Accident Prevention in Chemical Operations AFTER HOURS OPERATION PERMIT No. 001 FROM TO (Time-Date) (Time-Dace) LOCATION: _________________________________________________________ OPERATION: ________________________________________________________ EMERGENCY INSTRUCTIONS: POTENTIAL HAZARDS: RESPONSIBLE PERSON: _________________________ HOME PHONE NO. ___________________________ ADDRESS ___________________________________ OPERATION SET UP MUST BE APPROVED BY: SAFETY SUPERVISOR Approved __________________________ (Safety Supervisor) FIRE DEPARTMENT Approved __________________________ (Fire Dept. Rep.) OPERATION AUTHORIZED BY: Dace Area Supervisor Note: One copy of permit to be attached to equipment. One copy to filed with guard force office FIG. 26.7, After hours operation permit form. ETC 03488 460 Safety and Accident Prevention in Chemical Operations 1. All hazardous materials have been removed from the buildings or danger area, thorough decontamination or cleaning has been accomplished, and any necessary safety tests have been made 2. Precautions have been taken to prevent the reintroduction of haz ardous materials into the area until completion of all repair and maintenance operations. 3. It is also frequently required that the normal building foreman be present while all repair or maintenance work is performed. 4. Adequate information is given to the supervisor of the work crew as to any unusual conditions or hazards that may be present or develop during the operation, and the proper action to be taken in an emergency. The supervisor of the work crew also is usually responsible for in specting the area and accomplishing the following items before ap proving the permit and starting the operation: 1. Inform all employees of the operation to be done and explain all precautions and emergency actions to be taken. 2. Obtain any specific "hazardous operation permits'' needed during the course of the work, and taking all measures needed to prepare the area for the work to be performed such as wetting down, locking out controls, and posting or marking the work area. 3. Insure that all necessary safety equipment, emergency equipment, and fire fighting equipment is on hand, and that personnel know its location and are trained in its use. The testing of local hose lines and safety showers should also be performed by one of the crew members. Equipment needed may include: Neutralizing materials Protective clothing Air-line masks Gas masks Gloves Fire extinguishers 4. See that all the necessary tools, parts, equipment, and supplies are on hand for the work to be done. 5. See that after completion of the work, the area is inspected to insure that it is in proper condition, that all spills have been flushed or neutralized, and that all tools and work equipment or scrap have been removed. Permit Systems 461 The permit is then usually signed in the space certifying that the work has been properly completed and returned to the area supervisor for acknowledgment and forwarding to the plant engineer. Acid Area Work Permit Maintenance and repair operations in an acid manufacturing or processing area can contain an unusual number of hazardous situa tions, making use of a permit system very desirable or necessary. Figure 26.9 is a sample form of an "acid area work permit" form. The area supervisor, in authorizing a work permit for the acid area, is usually responsible for insuring that the following actions have been taken: 1. The work area has been inspected, all necessary safety tests have been made, and any unusual hazards or conditions are marked -- REYNOLDS PLANT ACID *ORK PERMIT For on? or m ore of the following: Pipe Fitting Machinist Carpenters Labor Crew Permit No Job Descript Floor Dare APPROVED BY Dect Superv sot ot Foreman: Maint. Supvr Leadman Foreman: Saietv Insp : PROTECTION CHECK LIST Check Items Inspecied 1 All Emplovees involved have been informed of nreraiirions 2 Combustible Materials have been removed 3 All lines drained and pressure released or lines blanked. 1 Area neutralized irh Soda Ash before entering ------------------------------ 3 Necessary Safety Equipment on hand and A. Swurh lock-out used Area thoroughly checked and safe 5 Tank entrv permit if needed 9 Hot work permit if needed. Uork Completed: iTunel ilork Supervisor! FRONT BACK FIG. 26.9. Acid area work permit form. 462 Safety and Accident Prevention in Chemical Operations and made known to the supervisor of the work crew. He should also verify the identification of the specific equipment to be worked on. 2. All necessary measures have been taken and any specific "haz ardous operation permits" needed have been issued. 3. Operating personnel, in the area or in adjacent effected areas, have been notified, and any necessary safety measures have been taken to prevent complications in the operation. 4. Adequate information is given to the work-crew supervisor con cerning any unusual emergency actions necessary to protect the facility. The supervisor of the work crew is usually also responsible for inspecting the area--and accomplishing the following items before ap proving the permit and starting the operation: 1. Informing all employees of the planned operation and explaining all the precautions and emergency actions to be taken if necessary. 2. Obtaining any specific hazardous operation permits needed dur ing the course of the work and taking all measures needed to pre pare the area, such as removing combustibles, and posting and roping off the work area. 3. Insuring that all necessary safety and emergency equipment is on hand and that a hose line is connected and available. He should also satisfy himself that personnel assigned are trained in the use of emergency equipment, know its location, and have tested the safety showers and eye-wash stations in the area. Equipment needed may include: Gas masks Acid suits Air line masks Face shields Acid hoods Gloves Boots Explosimeter (Ha) Neutralizing materials Life lines Fire extinguishers Danger signs Testing instruments 4. Seeing that all necessary tools, parts, equipment, and supplies are on hand for the work to be done. 5. Seeing that after completion of the work, the area is inspected to insure that it is in proper condition, that all spills have been flushed or neutralized, and that all tools and work equipment or scrap have been removed. ETC 03491 Permit Syitems 463 The permit is then usually signed in the space certifying that the work has been properly completed and returned to the area supervisor for acknowledgment and forwarding to the plant engineer. Flammables Area Work Permit Operations not a part of normal production activities in areas where large amounts of flammables are processed or stored are often subject to a permit system to limit the fire or explosion exposure of the facility. Normal maintenance and repair activities can be a serious threat where accumulations of flammable liquids, vapors, or gases may be encountered. An effective work permit system for these operations can greatly reduce the probability of accidental ignitions or fires, and greatly re duce the results of accidental fires by insuring the presence of adequate equipment. The "flammables area work permit" form (Fig. 26.10) is usually originated by the area supervisor who must authorize all work done in the area, and must certify that the following pertinent pre cautions have been taken: 1. The work area has been inspected and all necessary safety tests have been made; all hazardous materials or conditions have been removed or corrected, and, where impossible to remove, have been marked and made known to the supervisor of the work crew. 2. All necessary measures have been taken, and any specific "haz ardous operation permits" needed have been issued. 3. Operating personnel in the area or adjacent areas which may be affected have been notified, and all necessary safety measures have been taken to prevent causing complications in the operation. The supervisor of the work crew is usually also responsible for in specting the area and accomplishing the following items before ap proving the permit and starting the operation: 1. Informing all employees of the planned operation and explaining the precautions and emergency actions to be taken if necessary 2. Obtaining any specific hazardous operation permits needed during the course of the work, and taking all measures needed to prepare the site, such as wetting down, removing combustibles, posting and roping off the work area. 3. Insuring that all necessary safety and emergency equipment is on hand and that a hose line is connected. It may also be re quired that the plant fire department be notified. He should ETC 03493 Permit Systems 465 satisfy himself that the personnel assigned to the job are familiar with the emergency equipment provided. 4. Seeing that after completion of the work, the area is inspected to insure that it is in proper condition and that all tools and scrap have been removed. After completion of the work, the permit is usually signed in the space certifying that the work has been properly completed and re turned to the area supervisor for acknowledgment and forwarding to the plant engineer. 26.3. SPECIAL HAZARD PERMITS Special hazard permits are particularly useful when certain mater ials that are normally forbidden, or are to be restricted in use, must be handled. Special hazard permits are usually valid for a considerable period of time, depending on the circumstances under which the controlled items are needed, and frequently the permit restricts the items to a particular location or area. The permit can also insure that all neces sary conditions have been met, and it can be used to identify the specific persons or person authorized to handle the material. In cases where the material is particularly hazardous, the permit may not be issued until the personnel involved have been trained and have passed tests on their knowledge of the hazards involved, and the proper procedures and details of the standard operating procedure. Toxic Materials Permit Operations involving particularly hazardous materials or highly toxic compounds are usually spelled out in detail in a standard operat ing procedure or operation manual. In such operations a "toxic ma terials permit" can be used to control the locations and the personnel involved in such operations. The issuing of a "toxic materials permit" is usually limited to the senior supervisor in charge of the operation involved. The criteria for issuing the permit will vary, depending on the circumstances and the degree of control or limitation desired. Qualifications of personnel and test requirements may also be spelled out. When operations are to be limited to a certain room or area, any special conditions or requirements, such as control of access, marking, ventilation control, or structural requirements may also be spelled out. ETC 03495 ETC 03496 468 Safety and Accident Prevention in Chemical Operation* Equipment operating permits may also be used in controlling such critical operations as interrupting fire main systems and the clos ing of sprinkler control valves. Vehicle Operating Permit The restriction of the operation of vehicles to certified personnel is usually necessary because of the specialized nature of the equip ment and the large variety of operating controls involved. The proper operation of specialized equipment such as fork lift trucks, payloaders, graders, bulldozers, and transporters requires a considerable amount of training for operating personnel. The training course usually involves complete familiarity and knowledge of the operating rules, local traffic regulations, and prov ing actual operating ability by successfully completing a standard obstacle course. The permit is usually valid for a fixed period of one to two years with renewal requiring a refresher course and retesting. Figure 26.13 shows a permit in card form to be carried by the operator on his person. VEHICLE OPERATING PERMIT No. 001 Mr. _________is hereby authorized to operace the following equipment: RESTRICTIONS:_____________________________ This permit expires one year from date of issue. Date of Issue Supervisor FIG. 26.13. Vehicle operating permit form. ETC 03498 470 Safety and Accident Prevention in Chemical Operations Sprinkler Valve Closing Permit The operation of fire-main valves or sprinkler-system valves by unauthorized personnel, or without specific authorization, can seri ously jeopardize the fire protection system for the entire activity Many insurance carriers require notification of any anticipated inter ruption of fire mains or sprinkler systems. The use of a permit system for the closing of sprinkler or firemain valves can insure that adequate measures have been taken to reduce the hazards because of interruption of fire protection Figure 26.14 is a sample permit form for closing sprinkler valves. The issuing of these permits is usually limited to the plant engi neer, who will be required to insure that the following items are ac complished by responsible personnel: 1. The insurance carrier is notified. 2. Equipment is on hand for emergency restoration of the service, such as plugs, caps, and fittings. 3. Supervisors of the area affected are notified, and the local fire department or fire brigade is informed. 4. Fire hazardous operations are stopped or removed from the area. 5. Fire watch personnel are assigned to insure immediate discovery of fire or other serious developments during the period of interrup tion. 6. The system is inspected and all valves are opened after completion of the work or interruption. 7. The insurance carrier is notified of the return to service of the system. REFERENCES 1. National Safety Council, Accident Prevention Manual for Industrial Opera tions, 5th ed., Chicago, Illinois, Welding and Cutting, 1964, Chap. 29, pp. 29-1, 29-28. 2. American Standards Association, Safety in Welding and Cutting, Z 49.1, New York, 1950. 3. American Petroleum Institute, Accident Prevention Manual on Gas and Elec tric Welding and Cutting, New York, 1953. 4. Manufacturing Chemists' Association, Inc., "Entering Tanks and Other En closed Spaces," Safety Guide SG-10, and "Disposal of Hazardous Waste," Safety Guide SG-9,1961. 5. Joseph Guelich, Chemical Safety Supervision, Reinhold, New York, 1956, Chap. 19, Working in Tanks Safely, pp. 108-116; Chap. 17, Breaking Lines--A Serious Problem, pp. 98-104. ETC 03500 27 Proper Maintenance Prevents Accidents David. T. Smith Maintenance in the chemical industry differs from other industries because of the nature of the materials, processes, and types of equip ment used. Since much chemical work involves the movement of fluids, gases, and powdered solids from one piece of equipment to another, many pipelines, conveyors, fork-lift trucks, and other mate rial-handling devices are used. Containers are more likely to be tanks, drums, or some form of closed container than in other industries. Much of the chemical-reaction equipment involves mixing, "cooking," cooling, and stirring under widely varying levels of temperature and pressure in sizes from one-quart laboratory autoclaves to huge col umns that loom against the sky like grain elevators. Disassembling and reassembling in itself requires special rigging and millwrighting techniques. Specialized problems such as high corrosion rates, flam mable liquids, and toxic or noxious materials are peculiar to this in dustry. Therefore a high quality of work is more necessary for safety of operation than in most other industries. Leaking pipes, equipment improperly reassembled, and so on expose personnel to hazards.. The cases where the process line was connected into the stair-pipe railing, where steam was connected into the toilet, and where the electronic recording instrument began to play radio programs are part of the folklore of chemical maintenance. If they did not happen, they should have, because they are so typical of the many "boners" that 472 Proper Maintenance Prevents Accidents 473 are possible as a result of inadequate identification of pipes, wiring, and equipment. Records show many serious injuries and even deaths from mistakes such as connecting inert or toxic gases into air lines supplying air for humans to breathe or connecting piping so that wrong materials were added to reactions with resulting fires, explosions, and emission of toxic gas. Connections have been left open which allowed the escape of dangerous materials to expose personnel. Relief devices have been left inoperative or removed with vessels and systems to rupture from overpressure. A second source of hazard to personnel and property from improper maintenance is the failure of equipment during either normal or ab normal operations. For example, leaking acid pipes can drip on per sons, escape of flammable gas may result in fire or explosion, and loss of sulfide liquors to an acid stream will result in formation of deadly hydrogen sulfide gas. Even broken steps and stair rails take their toll of injuries every year. In summary, in no other industry is high quality of maintenance, workmanship, and proper identification as important to safety as in the chemical industry. Preventive Maintenance By inspecting, repairing, and replacing equipment on an intelligently planned schedule, we can prevent failures from occurring, for the most part. There are tremendous cost advantages to this type program as well as safety advantages. Breakdowns during manufacturing opera tions result in loss of production, inefficient use of manpower, and increased repair cost because of overtime and other emergency pen alties. These factors cost far more than the investment in a planned preventive maintenance program. The advantages to safety are ob vious because of the reduction of exposure to emergency conditions and the ability to plan and provide safe procedures and equipment. The advantages to quality and quantity of production are not to be over looked. Preventive maintenance essentially is the system of determining the probable frequency of failure of a device or system, and inspecting, repairing, or replacing it before it fails. We can draw a curve showing the probability of failure of a given device against time, and it will appear as the `'normal probability" curve (see Fig. 27.1). There is a very low probability that it may fail very early, then there is a rapid rise of probability of failure to an average value, then the curve 474 Safety and Accident Prevention in Chemical Operation* drops again. There is a very low probability that failure will be deferred until long after the average time. The shape of the curve will appear as a bell, with the peak as the average. Our job is to schedule maintenance so that we are confident that we take action before the likelihood of failure is 2%, or some other chosen figure. In other words, we would be confident that 98% of the time we will have ap plied maintenance before a failure occurs. It is obvious that this requires a knowledge of the average length of time before breakdown of the particular device under the specific conditions of operation. Often this is not easy to determine. Past experience in similar operations, studies of rate of deterioration, and other means of analysis can be used. Knowledge of how the device or system can fail, and of the most likely ways for it to fail can help to determine the frequency of failure. Needless to say the ability to match optimum maintenance dates and time with availability of equipment (release by operations for shut down), availability of materials, maintenance facilities and manpower are required. To accomplish this, planning ahead, using schedule sheets, and keeping everybody informed, appear to be key points. It is important to control all equipment from a preventive maintenance standpoint by making schedules for every piece, even if the frequency is as long as once every ten years. An example of the working of preventive maintenance in a typical plant follows. Pumps P-16 through P-22 in Building A310 step 1. Area-maintenance engineer and operating-department super visor agree on frequency of inspection and removal of pumps to pump Proper Maintenance Preventi Accidents 475 shop for overhaul. Spare pumps will be installed. Frequency is an nual and one pump is scheduled to be replaced each month, January through July. step 2. Shut-down dates and times are entered in production control schedule to coincide with down time for other mechanical work. step 3. Maintenance engineering group enters dates and times on work-order control-system cards. step 4. Monthly maintenance work-order schedule shows dates and times. step 5. Work order is issued one week in advance by maintenance engineering group. Time and date are agreed on again by operating supervision. Instructions are issued to operating personnel on readying equipment. step 6. Work procedures are reviewed with maintenance foreman and men. Men, equipment, and materials are lined up. step 7. Work done. step 8. Results are recorded on equipment maintenance record of the pump, and next overhaul date is scheduled. Proper maintenance to prevent accidents means more than achiev ing freedom of failure of the equipment and buildings maintained. It means protection of people while doing this maintenance. This can be considered in three phases: First, protection of operating personnel from temporary environmental haz ards caused by maintenance work. For example, roping off temporary open ings, keeping areas cleared below overhead work to protect against falling objects, keeping discarded parts and tools from being a stumbling hazard on floors, shielding of welding arcs, etc. Second, protection of maintenance personnel against hazards of the oper ating conditions. This requires clearance with operating supervision before doing any mechanical work, coordination of operating activities with mechan ical work, and use of permits where necessary to formalize this coordination. For example, a mechanic could step back from a pump repair job into an aisle in front of a moving fork-lift truck carrying a pallet of drums, unless operating personnel is familiar with his assignment, he has posted warning signs to protect his work location, and he has made himself familiar with the movements of the operating personnel in their work. Third, protection of maintenance personnel against hazards of their own work. Methods of doing work should be standardized where possible and written procedures prepared covering steps and key points. In this way we can avoid overlooking the lessons learned from previous mistakes and injuries. Too often we say, "every maintenance job is different, we cannot freeze them into a neat procedure." What we really mean is that we are too lazy to work out "agreed on" methods for repetitive jobs, and to put them down on paper. 476 Safety and Accident Prevention in Chemical Operations Shut Down and Start Up Clear cut responsibility for each step is the key note of planning and execution of shut down and start up. Shut down of operating equipment should be the responsibility of operations, not maintenance or other service groups. Auxiliary service groups should handle their own specialties, such as a power group handling the outside steam, electric, air, gas, and other services to buildings. Close coordination is required. Notification of shut down to interested groups should be made as far in advance as possible. Operating supervision must be held responsible for emptying, wash ing out, steaming out, purging with inert gas, and other steps to make equipment safe before turning it over to the maintenance group for working on it. Maintenance supervision has the responsibility to check as far as feasible to see that this has been accomplished before accept ing the equipment. Key points are proper blanking off of pipelines connected to the equipment, proper ventilation, and testing for flam mable vapors. During actual shut down, and even more likely during start up, unusual thermal stress may be added to the normal mechanical stresses. Exposure of personnel to leaks and ruptures of equipment must be guarded against. No connections should be tightened during warm-up periods--we must wait until temperatures have leveled off. During shut downs and start ups special care must be taken to see that all "lock-out" procedures are followed closely for electrical work, for moving machinery, and valves. Written procedures for emergency shut downs as well as for normal shut downs must be prepared, rehearsed, kept up to date, and kept available to people that have to use them. Provision must be made for emptying safely all lines that are to be opened, for accounting for conditions in all equipment, and for know ing the condition of all vents and relieving devices. Personnel must not be permitted to break into any pipeline without full protection against it being "loaded" regardless of draining and other procedures. Too often pipes have been plugged or partially plugged, trapping dangerous materials in them. Complete protection to the body means "acid-suit" protection or better against corrosive materials, and supplied air of breathing quality for respiratory pro tection against noxious fumes and gases. Proper Maintenance Prevents Accidents 477 Entering Vessels and Confined Spaces Entering vessels presents special problems because of the inability of the workmen to get out of the vessel without outside help in case of emergency and because of difficulty of communication. For these reasons, plus the possibility of emergency chemical exposures, rigidly enforced special precautions must be taken. These are required by statute or governmental regulation in many states. In general these include: 1. The vessel must be thoroughly cleaned by operations. 2. All connecting pipelines must be disconnected and blanked off. 3. All power driven devices (such as agitators) must be locked out at positive disconnect switches. 4. Air samples must be taken to prove absence of flammable vapors, and also in some cases, of toxic or noxious materials. 5. Air samples must be taken to prove presence of a normal amount of oxygen. 6. A tank entry permit must be signed by operating and maintenance supervision verifying that above steps have been satisfactorily complied with, and posted at the vessel site. 7. Men to enter vessel and watchman must be equipped with life belts and ropes. (Belts should be type fitting high under armpits for ease in lifting, not around waist. Handcuff types are preferred as alternates by some, opposed by others.) 8. In most cases, an air mask and fresh-air supply must be available for each man entering the tank and for the watcher. A chemical protective suit of impervious material completely enclosing the body, and provided with fresh breathing air and air conditioning for comfort not only serves that purpose but provides a safe com fortable working environment. It is equipped with an air-supply hose which also acts as a life line. 9. There must be one watcher at the vessel entrance who can keep in touch at all times with the man or men inside. In addition there must be at least one other man within call of the watcher to help in case of emergency. One man can do little by himself. Devices for signaling for additional help such as a ``Freon" ac tuated horn are acceptable. 10. Rope or chain ladders with rigid rungs of wood or metal may be used for vessel entry where straight ladders cannot be used. How- 478 Safety and Accident Prevention in Chemical Operations Similar principles should be followed when placing men in any confined space from which emergency exit may be hampered. Any pit or trench deeper than 5 ft, and any work on a roof or column where a man may be trapped in case of liberation of toxic fumes, requires special control procedures of similar principles. Burning, Welding, and Other Flame-Producing Work Because the chemical industry handles so many flammable and volatile materials, and because of the rapidly changing technology which in turn causes frequent changes in materials handled, control of ignition sources to prevent fires and explosions is of prime impor tance. Therefore, special procedures to reduce the hazard of fire from heat and flame producing work are essential. In general they cover these key points: 1. No welding or burning is permitted outside of designated welding shops and specified welding areas, without first obtaining permis sion of the operating supervision responsible through the use of a written, signed "burning permit" or "hot work permit." This should indicate the nature and location of the work, any particular restric tions required for safe performance, and the time during which the work is to be permitted. Since the issuance of a permit also entails the control of operations to prevent the creation of any hazardous conditions during the work period, it is important that the permit be made a responsibility of the operating-line organiza tion, not a service or staff group such as the safety or fire-protection group. It may be necessary to assign additional personnel to act as fire watchers during the job, and they may be supplied by the safety or fire protection group, but the responsibility for authoriz ing the work in any given location should be put squarely on the supervision responsible for the operating conditions of that loca tion. 2. Only qualified burners and welders should be given authority to perform this type of work, and mere mechanical skill is not enough. Proper Maintenance Prevents Accidents 479 These men must be trained in the responsibility to properly analyze and protect surrounding flammable materials, to extinguish fires, and to handle emergencies. A permit system certifying qualified welders has been proved useful in many plants. 3. All burners and welders must have first-aid fire protection on the job with them. Water hoses are generally needed also. Cracks and flammable materials must be protected by incombustible cov ers or barriers. Overhead work must be analyzed to provide suf ficient protection from sparks falling below. No flammable gas or oxygen cylinders should be permitted inside of operating, laboratory, or storage buildings, except under most unusual and carefully con trolled circumstances. Pressure Testing, Corrosion Inspection While various instruments are now available to permit accurate measurement of thickness of vessel walls at selected areas, they do not guarantee that a weakness has not developed at some location not measured. Therefore, they do not take the place of periodic hydrostatic pressure testing to determine the ability of the vessel to withstand pressures in excess of those of normal operation. The generally ac cepted ratio for periodic testing during usage of a vessel is one and onehalf times the normal working pressure; the frequency of hydrostatic test may be determined by analysis of the results on instrument studies of rate of thinning of the container walls, by measurement of container wall thickness by drilling or metallurgical study of plugs, and by experience. Once set, the hydrostatic testing schedule should be rigidly followed. Plans should be made in advance with operations so that production schedules can be arranged to fit. Hydrostatic testing is normally done with water, but if water is incompatible with the use of the vessel, other nonhazardous inert liquids may be used--never air or other gas. The only time that gases may be used for pressure testing is when use of liquids is not feasible, and then only when the vessel is barricaded to protect personnel and property from missiles and blast force in ease of rupture. The gas pressure in a vessel acts as an energy spring which will impel missiles at high velocities. Liquid pressure in a vessel drops instantly to zero on failure of the container. There is no need to hydrostatically test pipe and certain equipment used for noncritical services, unless failure can expose personnel to injury. No hydrostatic testing program is better than its control. Ad equate card files on each piece of equipment, adequate scheduling 480 Safety and Occident Prevention in Chemical Operations and communications with all parties concerned are needed to make it work. Locking and Tagging for Safeguarding Personnel While details vary from plant to plant, safe maintenance requires that no one may work on (or where exposed to) power-driven equip ment without locking out or physically disconnecting the source of power beforehand. This may be done either by (1) locking the electric switch on the power circuit (not the starting circuit) in the off position, (2) dis connecting the motor electrically or mechanically (3) by removing the belt drive or (4) locking feed valves to prime movers in the "off" position and blocking movement of pistons, crank arms, or fly-wheels. Any exceptions, such as adjusting glands and seals, must be approved by supervision. Written procedures should be prepared and thorough training given in their use. In general these procedures will stress: Operating supervision must first identify the equipment and equip ment controls. Operating supervision and each person who is to work on the equip ment go to the controls and individually place their locks on the controls after they have been placed in the off position. Each person keeps the key to his own lock. The equipment is rechecked then to be certain that it cannot be started. Work on it can then be commenced. When the work is completed, the reverse procedure is completed before turning the equipment back to operating supervision. When electric motors are disconnected, the switch box is still locked with the switch in the open position. In large scale mechanical jobs where numerous men and crafts are concerned with the same equipment, most plants permit a "group lock-out" where only the mechanical foreman's lock is placed on the switch, and each mechanic places his individual tag on the lock. Only the mechanic can remove his own tag, and the foreman will not remove the lock until all tags are accounted for. Whenever electricians work on electrical circuits or equipment, the same procedures can be followed unless testing or other work involving energizing the circuit is required. In these cases, after proper iden tification of the equipment and circuits by operating supervision, the Proper Maintenance Prevents Accidents 481 circuits and equipment are turned over to the electrician, who affixes his "blocking out" tags to the control points. No one but this electri cian can operate any controls after that until he removes his tags. As an additional safeguard, the electrician will lock the switch box during periods when his work will permit. Similar principles should be followed in doing work on pipelines or piping systems, with the valves tagged and locked if possible. All lines should be disconnected and blanked if practicable. Disposal of Chemically Contaminated Equipment It is the responsibility of operating supervision to see that all equip ment leaving the area is clean to a point where an employee, untrained in the hazards of corrosive, toxic, or flammable materials, can work on it safely. All equipment that is removed from service should be tagged immediately as to its state of chemical contamination, and the tag changed as conditions change. When it is clean it should be so tagged. Otherwise, there is always the danger someone may assume it is clean, and either move it or work on it. Obviously, it is impractical to decontaminate equipment before dismantling in many cases. In such cases cleaning and decontamination should be accom plished if possible before removal from the area. If it cannot be decontaminated at the area, it must be handled separately on a planned basis and taken to an adequate salvage area where it can be worked on. Each job may have to be individully studied and planned from a decontamination standpoint. Among the details to remember is that it is important to give special attention to prevent pipe and valves from being discarded with materials trapped in them. They can become bombs. All valves should be cleaned, the bonnet should be loosened, and the gate opened before being discarded. - Pipe may be heated at a burning ground. Flammable liquid wastes should not be allowed to reach drainage ditches or sewers. Glass should be handled separately from other waste materials. Other special problems will be apparent on detailed consideration. The important point is not to leave this phase of the maintenance work to chance. Emergency Maintenance Emergency maintenance should more properly be termed emergency repairs, since maintenance implies preventing emergency repairs. How ever, some emergencies do occur, and we must be prepared to meet 482 Safety and Accident Prevention in Chemical Operations them. In general, day-to-day maintenance procedures will meet th I situations arising, but some special problems require additional plan ning to meet. For example, what do we do if a pipe connection breaks off a chlorine tank? The time to plan to take care of it is in advance not after it happens. Considering this case, special clamp fittings can be made in advance and kept in an emergency kit with supplementary equipment to meet just such an emergency. Suppose a sulfuric acid pipeline ruptures. Planning shut down, wash down, and repair activ ities in advance will make it possible to take such mishaps in stride with minimum exposures to personnel and property. The key point is to "brainstorm" such incidents, decide in advance who should do what, with what, and line it up so that it can be accomplished if it happens. How about rupture of an underground pipeline? How are we going to handle the shut down? Who will be available to excavate? How will we flush out the broken pipe? How can it be plugged to keep it clean while the excavation is being pumped out? Are emergencv sleeves suitable? Are they available? How about pipe stock? What do we do when an electric line fails? Do wre have alternate routes of supply? Where are the switching facilities? What effect does loss of power have on emergency shut down of operations? These are all typical problems of emergency maintenance for which solutions can and should be planned in advance. There is one principle to adhere to in emergency maintenance. If it is not safe to do it a certain way under normal maintenance, then it is doubly unsafe to try that way under emergency conditions. A reasonably safe method can be found if we really try. If it is not safe to do electrical hot work under normal conditions, then it should be even more strongly forbidden during emergencies. Equipment Inspection and Maintenance Hand Tools. Several books could be written on ways in which hand IT tools can deteriorate into an unsafe condition; suffice to say the pipe wrench with dulled jaws has injured more mechanics than the most spectacular explosions. Mushroomed chisel heads, cracked or bent wrenches, faulty hammer and screw-driver handles, and poor chisel and screw-driver blade condition are all too common. We can meet these hazards only by special effort to educate our mechanics to keep their tools up to standard, and by making sufficient tool inspections to know that they are kept that way. Doing it after the injury helps, but periodic checking is better. A check list is desirable. ETC 03511 Proper Maintenance Prevents Accidents 483 Ropes. Slings, Chains, and Hoisting Equipment. Because the danger of failure presents unusually severe safety hazards, and because of the high wear factor, periodic inspection at a central point, with good record control, is a must for proper maintenance of ropes, slings, chains, and hoisting equipment. This includes life lines and life belts. In spection for defects seems the best procedure in most cases. Over loading for test purposes in itself may cause failure later on the job. However, tests up to rated capacity may uncover hidden defects. Because of wide variation of deteriorating exposures, no rules can be given for frequency of inspection and test, but it pays to err on the conservative side. There is a wealth of material available from sup pliers on safe use and maintenance of this equipment which can be used to advantage. For example, synthetic fiber ropes may be much less subject to chemical attack and therefore give longer life with a greater margin of safety--but the user should allow for their being smoother and hence they provide him with less hand grip. Ladders. Ladder failures during use usually result in falls and in juries--therefore they must be prevented. Standards for their pur chase should be established. Use only the stronger industrial grade ladders, even if cheaper ones will pass American Standards Association standards. They give greater margin of safety against abuse and wear. The length of ladders permitted should be spelled out in standards. Ladders should be carefully inspected by trained personnel, including hammer testing, and the inspection dates as well as ownership should be marked on each ladder. Strays have a way of developing among ladders. Many plants inspect each ladder annually, others more often. Supervision of Maintenance Personnel Supervision of maintenance workers presents special problems of its own from a safety standpoint, but these problems are capable of solution. Because of the changing work locations and assignments, mechanics are usually "on their own" more than chemical operating or laboratory people. It requires more effort on the part of mainte nance supervision than in the case of other groups to know how their men are performing, but it can and must be done. Sampling techniques applied to observation can be used because continuous observation is impractical. However, the setting of standards of performance in maintenance work and the training of men to achieve these standards is no more difficult than in other work groups. The same management 484 Safety and Accident Prevention in Chemical Operation* principles apply. We have to know the capabilities and characteristics of each man, and give him guidance where he needs it so that he can reach his highest potential. Management tools of communication commonly effective are daily short "tail gate" or "tool box" meetings scheduled individual contacts on safety subjects, scheduled inspection of work in various stages of completion to observe work techniques condition of tools and equipment, and housekeeping. In summary, good maintenance prevents accidents, by use of careful well-planned preventive maintenance, planning for emergencies, and day-to-day good techniques in management of men. REFERENCES Safety Codes, American Standards Association, 10 E. 40th St., New York. ASA-B31.1-1955, Code jor Pressure Piping with addenda. ASA-B7.1-1956, Use, Care and Protection oj Abrasive Wheels. ASA-B30.1-1943 (R. 1952), Jacks. ASA-B30.2-1943 (R. 1952), Cranes, Derricks, and Hoists. ASA-A17.1-1960, Elevators, Dumbwaiters, and Escalators with supplement 1963. ASA-C2. Motional Electrical Code. ASA-C5.1-1963, Protection Against Lightning. ASA-C33.8-1957, Grounding and Bonding Equipment. ASA-Z49.1-1958, Welding and Cutting. National Safety Council, Chicago. Illinois. Safe Practice Pamphlets. No. 70, Maintenance and Repair Men. No. 68, Pressure Vessels--Fired and Unfired. No. 98, Use and Care oj Hoisting Chains. No. 1, Ladders. No. 12, Scaffolds. No. 41, Tools--Hand. No. 76, Portable Electric Hand Tools. No. 105, Welding. 28 Fire Extinguishing Agents and Their Applications Arthur B. Guise Edmund D. Zeratsky 28.1. INTRODUCTION In recent years there have been increasingly rapid developments both in the field of fire extinguishing agents and fire extinguishing equipment. Simultaneously new and unusual fire hazards have also been increasing. These developments have made it difficult for persons concerned with fire protection in the chemical industry to make knowl edgeable decisions as to what should be used to adequately provide needed fire protection. This chapter is intended to provide informa tion that is not otherwise readily available to the director of in dustrial plant protection. Where the word "approved" is used in this chapter, it refers to materials or devices listed as suitable after examination and test by the Underwriters' Laboratories, Inc., Underwriters' Laboratories of Canada, or the Factory Mutual Laboratories. 28.2. CLASSIFICATION OF FIRES Fires are commonly divided into four basic classifications accord ing to the nature of the combustible material.16 However, there are different types of fires within each classification. For example, flam 485 486 Safety and Accident Prevention in Chemical Operations mable liquids may be in depth, flowing (sometimes escaping under pressure), or in relatively thin layers, as in a spill fire. Metals can be in powder form, chips or turnings, ingots or castings. Class A Fires Normally Class A fires are defined as "fires in ordinary combustible materials such as wood, cloth, paper, etc.," all of which produce glow ing embers as the result of the formation of carbonaceous material such as charcoal. Usually overlooked is the fact that charcoal it self is a Class A material which requires special consideration, be cause under certain circumstances neither w'ater nor bicarbonate-base dry chemicals are effective extinguishing agents, as will be discussed later. Also, rubber, rubber-like materials, and certain plastics are in the early stages of combustion burning more like Class B materials but in the latter stages are definitely Class A materials. Class B Fires Normally, Class B fires are defined as "fires in flammable petroleum products or other flammable liquids, greases, etc." However, there are certain solids, of w-hich naphthalene is an excellent example, which melt while burning and exhibit all of the characteristics of a flam mable liquid fire and have no embers. In recent years, metal alkyls have been found more frequently in the chemical industry, and these flammable liquids present special problems because of unusually low autoignition temperatures and, in some cases, violent reactivity with water. Technically, at the present time flammable gases do not fall in any fire classification category, but practically they should be treated as Class B materials. For many years it has been common practice to recommend against extinguishing fires in escaping gas because it was felt that if the flames were extinguished the gas would continue to flow to form an explosive mixture which might become later ignited and cause greater damage than if the original fire had been allowed to burn. Practical experience, however, has shown that in some cases it is necessary to extinguish the flames in order to stop the escape of gas. Gases normally stored in liquid form, such as propane and vinyl chloride, present a more difficult fire when escaping in liquid state than when escaping in gaseous state. Fire Extinguishing Agents and Their Applications 487 Class C Fires Class C fires are defined as "fires involving energized electrical equipment where the electrical nonconductivity of the extinguishing media is of importance." Where the electrical equipment is de energized, extinguishing equipment suitable for use on Class A fires may be used unless flammable liquids such as transil oil are involved. In the latter case extinguishers suitable for Class B fires should be employed. If a combination of Class A and Class B fire materials are involved, either water spray or multipurpose dry chemical should be used as the extinguishing agent. Class D Fires Class D fires are defined as fires in combustible metals. Low melting point metals such as sodium and potassium present problems in extinguishment because the fire soon involves only liquid metal which, being of low specific gravity, allows most extinguishing dry powders to sink through while the liquid metal is constantly exposed to the air. These metals also offer problems in that they spontane ously react with water, sometimes violently. High melting point metals are found in a variety of forms: powder, chips and turnings, sheet, ingots, castings, and extrusions. An ex tinguishing agent that might be entirely suitable for use on fires in castings might be hazardous to use on powder, or chips and turnings. A very common combustible metal, magnesium, is unusual in that it falls between the extreme low melting point metals and the high melt ing point metals so that it is found in all of the solid forms listed but also melts quite readily while burning to form liquid magnesium.22 Although the fumes from any burning metal should not be inhaled, the fumes from burning radioactive metals present extremely serious health hazards to fire fighters. Otherwise, the problems of extin guishing fires in radioactive metals are similar to those encountered in the extinguishment of fires in nonradioactive metals. When dry metal hydrides are burning, they should be considered equivalent to metal fires because both hydrogen and metal are burning. It is desirable to use dry powder metal fire extinguishing agents on such fires. 488 Safety and Accident Prevention in Chemical Operations 28.3. EXTINGUISHING AGENTS AND METHODS OF APPLICATION Water and Water-bttsed Extinguishing Agents PORTABLE FIRE EXTINGUISHERS In this discussion soda and acid fire extinguishers and calcium chloride solution antifreeze fire extinguishers are considered as equiva lent to those containing plain water because the chemicals do not in crease the fire extinguishing effectiveness. Although loaded stream fire extinguishers are also antifreeze extinguishers, this type of ex tinguisher is discussed separately because of its greater extinguishing effectiveness on Class A fires and because it has a small degree of effectiveness on Class B fires. Fire extinguishers containing water, calcium chloride antifreeze solutions, or soda and acid solutions are effective on Class A fires and on fires in wood soaked with oils or greases. These extinguishers are approved in capacities from 1% gal to wheeled 33 gal sizes. The water or water solutions are expelled from the extinguishers by a manually operated pump (pump tanks), by carbon dioxide from the chemical reaction of sodium bicarbonate solution and sulfuric acid (soda-acid extinguishers), by carbon dioxide from cartridges (cartridge-operated extinguishers), or by air stored under pressure in the same chamber with the water or water solu tion (stored-pressure extinguishers). All of these extinguishers are equipped with a hose and a nozzle designed to throw a solid stream for distances ranging from 30 to 50 ft. SODA AND ACID EXTINGUISHERS All soda and acid extinguishers are put into operation by first in verting to allow the acid to mix with the sodium bicarbonate solution so as to react to form carbon dioxide. Because sodium bicarbonate in solution loses carbon dioxide as it slowly converts to sodium car bonate, these extinguishers should be recharged annually in order to insure that there will be a sufficient quantity of expellant gas produced when the solution is mixed with acid. Soda and acid ex tinguishers must be protected against freezing. Fire Extinguishing Agents and Their Applications 489 WATER Water cartridge-operated extinguishers are pressurized by invert ing and bumping on a firm surface in order to puncture the seal of the cartridge and release the pressurizing carbon dioxide. Pump tanks and stored-pressure water extinguishers are operated while in the upright position. These extinguishers must be protected against freezing. ANTIFREEZE EXTINGUISHERS Calcium Chloride. Calcium chloride antifreeze solution cartridgeoperated extinguishers are pressurized by inverting and bumping on a firm surface in order to puncture the seal of the cartridge and release the pressurizing carbon dioxide. Pump tanks and stored pressure ex tinguishers of this type are operated while in the upright position. Because calcium chloride antifreeze solution is corrosive, approved extinguishers in which it is used are constructed of corrosion-resistant materials. Approved stainless steel extinguishers are not resistant to the corrosive effects of calcium chloride solution and it should never be used in these extinguishers. These extinguishers are suitable for use down to temperatures of --40F. Lithium Chloride. An antifreeze extinguisher using a solution of lithium chloride, and suitable for use to temperatures as low as --65F, has been developed by the United States Department of Defense.1 Loaded Stream. The chemicals in water solution discussed so far have not increased the extinguishing effectiveness of the solutions. They served only to produce carbon dioxide as an expellant gas or to lower the freezing point. Other chemicals when added to water increase the extinguishing effectiveness and the best known of the extinguishers of this type is the "loaded stream extinguisher." The extinguishing agent of a loaded stream extinguisher is a solu tion of potassium carbonate in water with other additives to reduce the freezing point to --40F. These extinguishers are available in capacities from 1 to 33 gal. The older extinguishers of this type were operated by inverting which mixed acid with the potassium carbonate to form carbon dioxide expellant gas. Later models used carbon dioxide cartridges for the storage of carbon dioxide gas and were operated by inverting and bumping to puncture the cartridge seal and release the gas. More recent models have been of the stored 490 Safety and Accident Prevention in Chemical Operation* pressure type in which air under pressure in the same chamber as the loaded stream solution expels the latter when a valve is opened with the extinguisher in the upright position. In addition to depressing the freezing point to -- 40F, the loaded stream solution improves the extinguishing effectiveness to the ex tent that 1% gal of loaded stream solution is given a 2-A rating by the Underwriters' Laboratories--which is obtained only by 2y2 ga] of plain water, soda and acid solution, or calcium chloride solution. A 21/a gal loaded stream extinguisher is given a 1-B rating by the Underwriters' Laboratories. On Class B fires, the loaded stream solution is most effective when applied in the form of spray. Rather specialized techniques are required to extinguish fires in volatile flam mable liquids with loaded stream extinguishers. Loaded stream solution should be used only in extinguishers in which its use has been approved. Other extinguishers may not be resistant to the corrosive effects of potassium carbonate, corrosion may impair the operating mechanism or weaken the shell and hazardous rupture of the extinguisher could result. Ethylene Glycol. Some owners of water extinguishers have used ethylene glycol to reduce the freezing point because their extinguishers are not designed for the use of calcium chloride or loaded stream solu tions. It requires 50% by volume of ethylene glycol with water to obtain a freezing point of --40F. It has been observed that if such a solution completely controls a fire it is equal to water in extinguish ing effectiveness. However, if complete control of the fire is not ob tained prior to. the exhaustion of the extinguisher, the water will be easily evaporated, and the fire will rekindle to become more intense because the ethylene glycol is a flammable liquid. It has also been stated that antifreeze agents of the ethylene glycol type may con tribute to corrosion at the weld joints of stainless steel extinguishers. Such corrosion could result in either leaks or hazardous rupture of the extinguisher shell. Wet Water. For certain purposes the extinguishing effectiveness of water may be improved by the addition of a wetting agent. A wetting agent is a compound which, when added to water in proper quantities, increases its penetrating and spreading abilities. Certain wetting agents in water solution will produce "wet water foam" when mixed with air by nozzles similar to those used in the production of mechan ical foam. Wet water streams and wet water foam streams are both effective on Class A fires and wet water foam is effective on Class B ETC 0351 Fire Extinguishing Agents and Their Applications 491 fires of the hydrocarbon type, such as gasoline, but should not be used on fires in flammable liquids soluble in water, such as alcohol. Depending upon the wetting agent, wet water streams sometimes can be used to emulsify certain flammable liquids thereby achieving extinguishment. Experience has indicated that Class A fires can be extinguished by wet water in a shorter time and with less water than if plain water had been used. Wet water, because of its penetrating power, is particularly effective on fires such as those in baled cotton or stacked hay. Not all materials that can be called "wetting agents" are suit able for fire protection purposes. Although NFPA No. 18 "Standard for Wetting Agents"21 gives detailed information on wetting agent specifications and tests, the average person responsible for fire protec tion will find it best to use only those wetting agents listed by the Underwriters' Laboratories. Listed wetting agents are no more cor rosive than plain water to steel, brass, bronze, or copper. Wet water should be used only in extinguishing equipment or storage tanks designed for such use since listed wetting agents, although noncor rosive, exhibit a tendency to accelerate corrosion because of the clean ing and penetrating action and will penetrate and loosen unbonded coatings. For continuous storage, even galvanized iron or lead coated iron are not suitable. Approved wheeled wetting agent extinguishers are available in capacities from 10 to 50 gal. WATER SPRAY ("FOG") The more effective use of water in the form of drops rather than a solid stream was first practically recognized in the installation of the perforated pipe extinguishing systems that preceded the automatic sprinkler systems (1864).12 The value of spray nozzles on hose lines was recognized in the latter part of the nineteenth century, but it was only in the 1930's that hose-spray nozzles began to be used to an important extent by both public and industrial fire departments. It was also in the 1930's that special spray, or "fog," nozzles were developed for installation in systems. These spray nozzles produced directed streams of drops of water much smaller in size than those produced by the automatic sprinklers of that time. An automatic sprinkler improved in design to produce more finely divided drops of water in a better regulated pattern than the older automatic sprinklers was first used in 1952.3 In general, water spray may be used effectively for any one or any combination of the following purposes: extinguishment of fire, 492 Safety and Accident Prevention in Chemical Operation! control of fire, exposure protection, or prevention of fire.19 The short range of spray nozzles is not a factor where the nozzles are installed on a well-engineered system but the short range imposes a definite limitation on the effective use of spray nozzles on hose lines. The droplet size is related to the range of the streams from spray nozzles the heavier drops traveling farther than the very fine drops. A con siderable number of carefully controlled tests with portable spray nozzles have been run to determine the effect of nozzle pressure and droplet size on the control and extinguishment of both Class A and Class B fires.15'13,25,9 The conclusions drawn from the results of the tests may be summarized briefly as follows: 1. Increasing the nozzle pressure beyond 100 psi results in little or no increase in fire extinguishing effectiveness. 2. Very fine droplets tend to evaporate before reaching the seat of the fire and therefore control, but do not always extinguish the fire. On Class B fires, droplets having diameters of 100 to 150 microns are considerably more effective than droplets having diam eters in the order of 300 microns, but the very fine droplet may evaporate before reaching the surface of the burning liquid which will therefore not be cooled. 3. Although coarse drops of spray do not evaporate as readily as very fine drops, the unevaporated portion of the coarse drops penetrates the flame zone to reach the seat of the fire and exert cooling action. Where approach to the fire permits, portable water-spray nozzles are considerably more effective on Class A fires than straight streams because the water is applied with less run off. British tests showed that a spray gave more rapid control of a fire than a straight stream and that when straight streams were used more water was required to extinguish the test fires. Although very small gasoline fires can be extinguished under certain conditions by the use of water-spray noz zles, the latter are usually successful only in extinguishing flammable liquids having flash points of 150F or higher.3 Electrical equipment involved in a fire should be de-energized as quickly as possible, but it is not always possible to do so. Even so, either fresh or salt water may be safely applied to energized electrical equipment if the following clearances between nozzles and electrical apparatus are observed or exceeded. (See Table 28.1.) Spray nozzles, either on hose lines or in systems, are sometimes used only to control fires where extinguishment is not possible or extinguish ment is not desired because the fire is in flammable gases or extremely volatile flammable liquids. Sometimes such fire control is combined ETC u3 o 21 Fire Extinguishing Agents and Their Applications 493 TABLE 28.1. Table of Clearances19 Voltages Up to 7,500 7,500 to 15,000 15,000 to 25,000 25,000 to 37,000 37,000 to 50,000 50,000 to 73,000 73,000 to 88,000 88,000 to 110,000 110,000 to 132,000 132,000 to 154,000 154,000 to 187,000 187,000 to 220,000 Distances 6 in. 12 in. 17 in. 24 in. 32 in. 44 in. 52 in. 64 in. 77 in. 89 in. 106 in. 124 in. with the protection, by cooling, of exposed equipment, structures, or storage tanks. Spray nozzle systems installed for extinguishment, control, or ex posure protection may also sometimes be used for the prevention of fires if operated when hazardous materials have been accidentally released but before they have become ignited. As a guide to the quantities and rates of application of water in spray form the following may be used: (a) Extinguishment --0.2 (b) Control --0.2 (c) Exposure protection--0.2 to0.75 gpm/sq ft to0.5 gpm/sq ft to0.25 gpm/sq ft Water spray systems should be designed by experienced fire protec tion engineers to insure adequate protection for the hazard involved. SOLID STREAMS OF WATER When water-spray streams cannot practically be used because of lack of reach because of fire intensity or fire location, or where there are dangers from falling walls or possible explosions, solid streams must be used. Solid streams are, of course, used primarily in the extinguish ment of Class A fires--structures, lumber storage, and so on. How ever, they are also used for the extinguishment of fires in high flash point Class B materials in thin layers or fires in flammable solids such as naphthalene. Solid streams are also used for the protection of ex posed equipment, structures, and storage tanks when such protection ETC 03522 494 Safely and Accident Prevention in Chemical Operations is not afforded by spray-nozzle systems and are out of reach of water spray from hose lines. Effective streams are the result of advance planning to insure ade quate water supplies, of proper layout of water mains, and of train ing of the fire fighters to make best use of hydrants, hose, nozzles, and pumpers, if the latter are available. One of the best books for in dustrial and volunteer fire fighters, as well as large paid departments, is Effective Streams jor Fighting Fires by Warren Y. Kimball, Na tional Fire Protection Association. Other helpful information may be found in Mobile Fire Equipment, Organization, Management, Na tional Fire Protection Codes, Volume VII, National Fire Protection Association. Information on water supplies and the layout of mains and hydrants may be found in Fixed Extinguishing Equipment, Na tional Fire Code, Volume IV, and in the NFPA Handbook of Fire Protection. Although no reports are yet available as to practical use, research is being carried on at Syracuse University for the United States Navy Bureau of Yards and Docks on Additives to Improve the Fire-Fighting Characteristics of Water. This research is aimed at evaluating the effectiveness of increasing the viscosity of water to decrease the rate of run-off and of increasing the opacity of water to transmission of infrared. It has been reported that the addition of opacifiers such as aluminum and bronze powders to water, increased in viscosity by certain chemical additives, has decreased the extinguishing time on certain standard fires to below that required for plain water. Foam. There are two types of fire fighting foams: chemical foam in which the bubbles are filled with carbon dioxide, and mechanical foam in which the bubbles are filled with air. Chemical foam is pro duced by a chemical reaction which generates carbon dioxide bubbles in water solution containing a foaming ingredient. The reacting chemicals, usually sodium bicarbonate and aluminum sulfate, may be stored in separate water solutions, which are mixed when foam is wanted, or in powder form in separate containers and simultaneously mixed with water to form foam, or in powder form in a single con tainer and mixed with water to form foam. Portable chemical foam extinguishers all employ two solutions which are mixed when the extinguishers are inverted. Although chemical foam is used almost exclusively for the protection of Class B fire hazards, the Underwriters' Laboratories gives portable foam extinguishers Class A ratings equal to those given water extinguishers of the same volumetric capacity. 4 Fire Extinguishing Agents and Their Applications 495 Chemical foam solutions should not be exposed to temperatures lower than 40F nor higher than 120F. The sodium bicarbonate solution is especially sensitive to temperature conditions, the sodium bicarbonate crystallizing out of the water if the solution is frozen and decomposing to lose carbon dioxide when the solution is at temper atures exceeding 90F. Annual recharge of portable foam extin guishers compensates for normal deterioration of the sodium bicar bonate solution. However, chemical foam itself is also sensitive to the effect of tem perature. At low temperatures the chemical reaction takes place more slowly and the foam has a lower expansion ratio as compared with the approximate ratio of eight found at normal ambient tem peratures. At high temperatures the chemical reaction takes place rapidly, there is a high expansion ratio, and the foam breaks down more rapidly. Approved hand portable chemical foam extinguishers are available in capacities of lx/4 to 5 gal, with the latter size intended primarily for use in industrial establishments w'here persons of ample strength will handle it. Approved wheeled extinguishers are available in capac ities of 17 and 33 gal. The hose of these larger extinguishers are equipped with shut-off nozzles. Stream ranges are in the order of 30 to 40 ft for hand portable extinguishers and up to 50 ft for wheeled extinguishers. MECHANICAL (.AIR) FOAM Mechanical foam is produced by mixing air with a dilute solution of a liquid foaming agent in water. The air is mixed with the water solution by aspiration into a foam maker or by means of a specially designed pump. The liquid foaming agent is available in two concen trations: one intended for mixing in water to a 3% concentration and the other intended for use in 6f/'( concentration. Mechanical foams are classified by expansion ratios, that is, the gallons of foam produced per gallon of water-foaming agent solution mixed with air. The most common is low-expansion foam having an expansion ratio of 7 to 12. High-expansion foam has a ratio of 16 to 18. A special, and less common, category of mechanical foams is the wetting agent type which is approved for use on Class A fires and, when having an expansion ratio of 8 to 10, is approved for Class B fires. There is also what might be called "super-high expansion'' foam having an expansion ratio of 1000. This foam is produced by blowing ETC 035 A foam agent introduced in 1964 contains a fluorochemical sur factant that creates a film over the surface of fuels similar to gasoline and thereby retards reignition even after the foam layer has broken down.31 The foam is completely compatible with military specification potassium bicarbonate-base dry chemical. Tests with developmental equipment have indicated that the new agent, referred to as "light water," is approximately four times more effective than mechanical foams when used for the extinguishment of spill fires. Ordinary mechanical foam concentrates should be stored at tem peratures of 20F or higher as specified by the concentrate manufac turer. Special "low-temperature" concentrates are available and these concentrates may be stored at temperatures as low as --20F. Con centrates producing mechanical foam suitable for use on alcohols and ketones should be stored at 35F or higher. However, no mechanical foam concentrate should be stored at temperatures higher than 120F. Although chemical foam is not affected, ordinary dry chemical causes mechanical foam to break down, the degree of breakdown depending to some extent on the formulation of the foam concentrate. However, there are special dry chemicals which have been examined and tested by the Underwriters' Laboratories and found suitable for use with mechanical foams which are designated by the Underwriters' Laboratories as "compatible for use with listed foam-compatible drychemical Extinguishers."32 These compatible concentrates are gen erally 3 and 6% solutions of regular- and low-temperature concentrate. The foam concentrates for producing mechanical foam for use on al cohol and ketones are not compatible with foam-compatible dry chemical. There are no approved portable extinguishers that produce mechan ical foam although such extinguishers are used in Europe. SYSTEMS Hose Line Systems. Chemical-foam hose streams are almost invariably straight streams. The nozzle throat size is much larger than that commonly used with water. If the manufacturers recommend un available nozzle sizes, it is best to remove the tip from the play pipe and use the full 1% in. opening. Although it is possible to operate a chemical-foam generator with water pressure of 50 psi at the inlet, the inlet pressure should be between 75 and 125 psi. The back pressure at the discharge side of the generator should not exceed 40% of the jl I ETC 03525 Fire Extinguishing Agents and Their Applications 497 generator inlet pressure. With a single powder generator it is best not to have more than 50 ft of hose between the generator outlet and the nozzle. With a dual hopper chemical foam generator using the sep arate powders, longer lines can be used between the generator and the nozzle as long as the back pressure is not in excess of 40% of the generator inlet pressure. Mechanical foam hose streams are of two types: one in which the water and foam concentrate are mixed in the proper proportions before entering the hose line and air is aspirated to make the foam in the play pipe, and a second type in which the foam is made with a special pump and the foam itself moves through the hoseline. In the first case the length and size of hose are not important as long as the pressure at the nozzle is not less than 50 psi. However, when the foam is pumped through the hose the length and size of the hose becomes much more important and the manufacturers' recommenda tions should be closely followed. Mechanical-foam hose nozzles are available in a variety of types to produce straight streams or spray streams. Fixed Nozzles Systems. Two-solution foam system equipment is in modern practice of limited capacity and intended primarily for the protection of small industrial hazards. Foam powders are generally used for extinguishing fires in large flammable liquid storage tanks. The dual powder system has the advantage of allowing longer runs of pipe between the point of introduction of the powders into the water streams and the protected tank because mixing of the two re sulting solutions takes place at a foam-mixing chamber mounted on the tank. However, the dual powder system has the disadvantage of requiring more manpower than the single powder system.3 Chem ical foam is best made from solutions of water in the temperature range of 50 to 90F. Foam systems are used for the protection of specific Class B hazards where the quantity of water, the quantity of foam-producing agent, the rate of application, and the number of outlets can be predeter mined. The type and the location of foam outlets for the protection of flammable liquids in depth are related to the rate of application of foam and the quantity of foam-producing material required because foam is more effectively applied if there is a minimum of submergence of the foam and a minimum of agitation of the surface of the flam mable liquid. On indoor hazards such as dip tanks foam is applied from fixed nozzles located along the edge of the tank or from pendant nozzles 498 Safety and Accident Prevention in Chemical Operationt arranged overhead. On outdoor vertical storage tanks discharge out lets are sometimes supplemented with means for delivering foam onto the surface of the burning liquid without undue submergence or undue agitation of the surface of the liquid. This may be accomplished by a Moeller tube which is designed to unroll and fall to the flammable liquid level and which permits the foam to flow through the coarse mesh of the tube, or by a foam trough attached to the inside of the tank wall to form a descending spiral to within 4 ft of the bottom, or by a foam chute which is a delivery conduit within the tank with staggered openings so that the. foam is delivered onto the surface of the flammable liquid from the opening just above the surface. When such methods of delivering foam are not provided, the amount of foam-producing agent required for extinguishment should be dou bled. Foam has been applied to vertical storage tanks to a limited ex tent by injecting the foam below the surface of the flammable liquid. This is called "subsurface application." A discussion of this method of application will be found in the April, 1946 Quarterly of the National Fire Protection Association. Because foam is broken down by the heat of the fire and, to some extent, by the flammable liquids to which it is applied, the rate of application must be sufficiently high to offset the breakdown and to cover the flammable liquid surface to an adequate depth in a reason able period of time. Although the following discussion of. rates of application and quantities required is based on water or water-foam agent solution, not foam, the intent of the recommendations is that a 6-in. blanket of foam be formed on localized inside hazards such as dip tanks and a 4-in. blanket of foam be formed on the surface of flammable liquids in outdoor storage tanks. A foam system for a localized inside flammable liquid hazard should be designed to have an application rate of 0.16 gal/min/sq ft of flam mable liquid surface and a sufficient quantity of foam-producing mate rial to insure that foam is applied for not less than 3 min. On outdoor storage tanks, the minimum rate of application should be 0.10 gal/min/sq ft of flammable liquid surface but should be con siderably higher, even doubled, where very volatile materials (such as casing-head gasoline) or water soluble solvents are protected. If hose streams are used, the minimum recommended rate of applica tion is 0.16 gal/min/sq ft of surface. The quantities of foam-producing material required for systems protecting outdoor storage tanks vary widely according to the flammable liquid and the method of applying Fire Extinguishing Agents and Their Applications 499 the foam. For example for gasoline the system must be designed to apply foam for periods ranging from 30 min to as high as 65 min depending on the method of application. Recommendations for the foam application rates and the quantities of materials required are given in considerable detail in NFPA No. 11, Standard jor Foam Extinguishing Systems.11 Foam-Water Sprinkler Systems. Foam-water sprinkler systems are installed where it is desired to protect large areas where fires may be anticipated in thin layers of flammable liquid such as spills. The foam discharge is intended to cover the area regardless of intervening ob struction, and the system should be arranged to continue automatically as a deluge type water sprinkler system after foam injection is com pleted. The most complete specifications for foam-water sprinkler sys tems can be found in Chapter 16 of NFPA 409, Standard, on Aircraft Hangars.2* For hangars the recommended rate of application is 0.17 gal/min/'sq ft with a supply of foam agent sufficient to allow foam to be supplied for 10 min. Foam may also be used for the prevention of ignition of flammable liquid spills by laying down a blanket which allows less hazardous handling of the spill. Even traces of certain wetting agents may prevent the formation of mechanical foam. This becomes important when a wetting agent has been used and later replaced by mechanical foam concentrate, or wetting agent foam is applied simultaneously with mechanical foam. Dry Chemicals A dry chemical extinguishing agent is a finely divided powdered material that has been specially treated to be water repellent and capable of being fluidized and free-flowing so that it may be discharged through hose lines or piping when under expellent gas pressure. The major components of three types of dry chemicals used in approved extinguishers are sodium bicarbonate, potassium bicarbonate, and ammonium phosphate (usually monoammonium phosphate). TYPES OF DRY CHEMICALS Sodium Bicarbonate-base. The use of sodium bicarbonate as the major component of a dry chemical extinguishing agent, expelled by gas pressure from an extinguisher, started in Germany in 1912. About 1926, the forerunner of the modern dry chemical extinguisher ] ! I ETC 03528 Safety and Accident Prevention in Chemical Operations was first produced in the United States. The dry chemical extin guishing agent consisted of a fairly coarse sodium bicarbonate powder compounded with magnesium stearate to produce water repellency and free-flowing properties. In 1943 it was found that the extinguishing effectiveness of dry chemical could be greatly increased by usino more finely divided sodium bicarbonate and later improvements in the method of applying the dry chemical stream to increase effectiveness even further, resulted in this type of fire extinguisher becoming of great importance as first-aid equipment for Class B fires. In 1930 the effectiveness of dry chemical in quickly reducing the intensity of flames was recognized, even on Class A materials. It was also known that it would be advisable to follow up with the application of water to extinguish remaining smoldering embers. Improvements in agent and improvements in equipment resulted in recognition by the Factory Mutual Engineering Division in 1948, after a very thorough test program, that dry chemical extinguishers were preferable for use in cotton processing areas.4 In 1952, extinguishers containing sodium bicarbonate-base dry chemical were submitted to the Under writers' Laboratories for test on Class A fires. Although flames were more rapidly reduced in intensity when dry chemical was used, as compared with w'ater, it was found that there was a greater tendency to reflash in a shorter period of time and the extinguishers were not approved. Potassium. Bicarbonate-base Dry Chemical. Recognition of the great effectiveness of dry chemical extinguishers resulted in increased re search and development on powdered extinguishing agents other than those of sodium bicarbonate-base. The extinguishing effectiveness of potassium bicarbonate-base dry chemical on gasoline fires was first investigated by the Naval Research Laboratory and they reported in 1958 that this type of dry chemical was twice as effective as sodium bicarbonate-base dry chemical.26 This work resulted in a military specification for the foam compatible potassium bicarbonate-base dry chemical which is now being used in Naval Air Stations in place of sodium bicarbonate-base foam compatible dry chemical. Potassium bicarbonate-base dry chemical extinguishers were first approved in 1961 by the Underwriters' Laboratories. The results of their tests, as shown in Table 28.2, confirmed the high extinguishing effectiveness reported in 1958 by the Naval Research Laboratory. Despite the greater effectiveness of potassium bicarbonate-base dry chemical on Class B fires, the chemical similarity between sodium F-TC 0352 9 Fire Extinguishing Agents and Their Applications 501 I TABLE 28.2. Comparative Effectiveness of Sodium Bicarbonate-Base | and Potassium Bicarbonate-Base Dry Chemical Fire Extinguishers (Based on Underwriters' Laboratories Listings)32 Ratings for Class B and C Fires Nominal Charge lb Potassium Bicarbonate- base Sodium Bicarbonate- base 2% 4% lb 125 300 350 SB: C 16B: C -- -- 160B.-C 240B: C -- 6B:C -- 10B: C 80B:C -- -- 160B.-C bicarbonate and potassium bicarbonate indicates that the latter would be basically similar in effectiveness on Class A fires. Foam Compatible Dry Chemicals, The United States Air Force in 1950 evaluated sodium bicarbonate-base dry chemical as an extin guishing agent for aircraft crash fires. Although the agent was found suitable from an extinguishing standpoint the metal stearate treat ment of dry chemical caused rapid breakdown of mechanical foam blankets. A good solution to the problem of foam compatibility of dry chemicals was not reached until water repellency and free-flow characteristics were obtained by coating the particles of dry chemical with a silicone polymer instead of a metal stearate. Impetus to the solution of the problem of foam compatibility was given by the promulgation of a United States Coast Guard regula tion that marine-type dry chemical fire extinguishers over 5 lb in capacity must contain foam compatible dry chemical if manufactured after January 1, 1962.6 The first standard for evaluating the foam compatibility of dry chemical agents was developed by the Naval Research Laboratory and incorporated in a military specification in 1956.2; The Under writers' Laboratories Incorporated developed a different procedure for the evaluation of foam compatible dry chemicals in 1961. The degree of foam compatibility required by the Underwriters' Laborato ries Incorporated is greater than that required to meet the military specification. However, dry chemical meeting the military specifica tion has been in use for several years and under practical fire fighting conditions has been found to be adequately foam compatible. ETC 03530 502 Safety and Accident Prevention in Chemical Operationt Multipurpose Dry Chemical. The newest of dry chemical extin guishing agents is the so-called "multipurpose" dry chemical that ' approved for use on Class A, B, and C fires. In 1956 multipurpose dry chemical was being used in German but this material was of poor quality. It had limited effectiveness on both Class A and Class B fires and a pronounced tendency to cake In 1960 the Underwriters' Laboratories Incorporated approved for the first time a multipurpose dry-chemical fire extinguisher which used an extinguishing agent based upon a patented German formula. By the end of 1961 a number of other multipurpose dry chemical ex tinguishers had been approved, including wheeled extinguishers. The majority of approved multipurpose dry chemical fire extinguishers are very effective on both Class A and Class B fires and also are listed as suitable for use on Class C fires. Table 28.3 shows the effective ness of the highest rated multipurpose dry chemical extinguishers as compared with water on Class A fires and as compared with sodium bicarbonate-base dry chemical on Class B fires. TABLE 28.3. The Effectiveness of Multipurpose Dry Chemical Extinguishers as Compared with the Effectiveness of Water and Sodium-Bicarbonate-Base Dry Chemical Extinguishers (Based on Underwriters' Laboratories Listings)32 Nominal Charge Underwriters' Laboratories Ratings Class A Class B Pounds 7.5 10 10.4 17 20 20.8 41.6 125 150 275 300 350 558 Gallons -- D/4 -- -- 2% 5 -- -- 33 -- -- 67 Water _ -- 1-A -- -- 2-A 4-A -- -- 20-A -- -- 40-A Multi- ' purpose Dry Chemical 1-A 2-A -- 3-A 4-A -- -- 20-A -- -- 40-A -- -- Sodium bicarbonate- base Dry Chemical -- 20-B -- -- 20-B -- -- -- 80-B -- -- 160-B -- Multi purpose Dry Chemical 16-B 20-B -- 20-B 20-B -- -- 80-B -- -- 160-B -- -- ETC 03531 Fire Extinguishing Agents and Their Applications 503 It is obvious that when considered on a pound-for-pound basis multi purpose dry chemical is approximately twice as effective as water on Class A fires and slightly more effective than sodium bicarbonate-base dry chemical,on Class B fires. Multipurpose dry-chemical extinguishers have certain obvious ad vantages where Class A fire hazards are to be protected: 1. For equivalent protection, they are lighter in weight which is advantageous where it is anticipated that women may use firstaid fire extinguishing equipment. 2. Where mixed Class A, B, and C fire hazards are involved, only one type of extinguisher is needed, and there is no chance of the wrong type of extinguisher being used on a fire. 3. Special models are approved for use as low as -- 65F. 4. Where water damage is highly undesirable, such as in libraries, art museums, or other locations where there are articles or materials of high value that would be irreparably damaged by water, the multipurpose dry chemical extinguisher may furnish the best fire protection. PORTABLE FIRE EXTINGUISHERS Portable fire extinguishers using all three types of dry chemicals are of two general types, one in which the fluidizing and expellant gas is stored in a separate container under high pressure and released into the dry chemical container when it is wished to put the extinguisher into operation, and the other in which the expellant gas is stored in the same container with the dry chemical. Hand portable fire ex tinguishers of the first type have the expellant gas, usually carbon dioxide, contained in a small compressed gas cylinder commonly called a "cartridge." The expellant gas in the case of extinguishers approved for use at -- 65F is nitrogen. In almost all approved extinguishers of the cartridge type, the expellant gas is released into the dry chemical container by puncturing a metal sealing disk. Some of the cartridgeoperated hand portable extinguishers have the nozzle integral with the extinguisher. However, the majority are equipped with both hose and a controlling nozzle. Hand portable cartridge-type extinguishers range in capacity from 4 to 30 lb. Wheeled extinguishers in which the gas is stored separately from the dry chemical chamber use nitrogen as the expellant gas, controlling the pressure within the dry chemical container by means of a regula tor. This type of design permits the expellant gas to continue to flow ft ETC 03532 constant pressure. As a result there is little change in the flow characteristics throughout the entire discharge. Wheeled extinguishers of the foregoing type range in capacity from 75 to 350 lb. Extinguishers in which the expellant gas is stored in the same container with the dry chemical extinguishing agent are called "stored pressure" extinguishers. Although most stored pressure extinguishers are equipped with pressure gages there is one special type of approved stored pressure extinguisher that is not required to have a pressure gage. Inspection' of this extinguisher requires weighing to detect pos sible loss of gas by leakage. This type of extinguisher is sometimes called a "sealed pressure" extinguisher because the dry chemical con tainer must be factory filled and sealed, and is nonrefillable. There fore it is sometimes called a "disposable shell" extinguisher. Portable stored pressure extinguishers range in capacity from 1 to 250 lb. The smaller sizes have the nozzle integral with the control valve, but the larger sizes of hand portable extinguishers are equipped with hose, in most cases controlling the flow by means of the valve on the extinguisher, but in other cases the nozzle at the end of the hose is also to-control the flow. All wheeled stored pressure extin guishers control the flow with the nozzle at the end of the hose. Stream ranges of dry chemical extinguishers vary widely since even a single manufacturer may provide nozzles of two ranges for extinguishers otherwise identical in size and capacity. Hand portable extinguishers have stream ranges of 5 to 25 ft. Wheeled extinguishers have stream ranges of 10 to 45 ft. HAND HOSE-LINE SYSTEMS Dry chemical systems of the hand hose-line type range in capacity from 150 to 2000 lb. Most use nitrogen in separate cylinders for fluidizing and expelling the dry chemical, controlling the flow with regulators. Stored pressure hand hose-line systems are approved in capacities from 150 to 250 lb. It is possible to supply as many as eight hose stations from large systems but such arrangements should be engineered by the manufacturer of the equipment. Dry chemical hand hose-line systems are generally located where it is not necessary to have the extinguishing equipment mobile, as in the case of wheeled extinguishers. A typical fire hazard protected by such systems is a petroleum-products loading rack. ETC 03533 Fire Extinguishing Agents and Their Applications 505 FIXED-NOZZLE SYSTEMS Dry-chemical systems with piping and fixed nozzles are approved for both automatic and manual operation. Approved systems range in capacity from 30 to 500 lb. These systems may be used for the protection of specific hazards by local application of the dry chemical or installed so as to flood an entire room or building. The design and installation of a dry-chemical piped system should be supervised by qualified fire-protection engineers having full knowledge of the special problems of piping dry chemical to obtain the correct rate of application and the proper distribution from the nozzles. Helpful in formation is given by NFPA No. 17, Standard for Dry Chemical Ex tinguishing Systems.20 Dry-chemical piped systems are used for the protection of electrical equipment such as generators, circuit breakers, transformers, and for many other hazards where flammable liquids are involved. They have been notably successful in installations protecting asphalt im pregnating equipment in the manufacture of roofing and siding. Ii Because air dilution is not such an important factor with dry chemical, i piped-system protection of duct work is quite common, and there is an increasing use of dry-chemical systems for the protection of cotton gins. Because dry chemical is nonconductive, care should be taken in the use of dry-chemical extinguishers in locations where there are many delicate low-voltage electrical contacts, such as in telephone relay rooms. SPECIAL DRY CHEMICAL AGENTS Because of the flexibility allowable in composition of dry-chemical extinguishing agents, it is possible to compound free-flowing powdered materials for the control and extinguishment of fires in unusually hazardous chemicals. A typical example is an extinguishing agent for use on metal alkyl fires in which the agent is a mixture of sodium bicarbonate-base or potassium bicarbonate-base dry chemical and an activated adsorbent such as silica gel. The pyrophoric characteristics of short-chain metal alkyls such as triethylaluminum (which reacts violently in contact with water) allow extinguishment of the flames only during application of dry chemical. If application is discontinued, immediate reflash occurs. The special compound containing adsorbent ETC 03534 506 Safety and Accident Prevention in Chemical Operationt material extinguishes the flames and at the same time the spilled m J j]alkyl is being adsorbed, resulting in extinguishment of the fire allowing disposal of the now safe pyrophoric material.33 Because of the necessity of adsorbing spilled material while controlling the fire considerable quantities of the special agent are required. As a guide' from 8 to 10 lb of the special extinguishing agent are required for each pound of metal alkyl involved in the fire. An alternative method of controlling metal alkyl fires is to apply an ordinary dry-chemical extinguishing agent on the flames simulta neously with the application of an activated adsorbent from a separate extinguisher. This requires that the adsorbing agent by itself possess good flow characteristics. Other hazardous chemicals such as fluorine and chlorine trifluoride offer unusual problems when spilled, and special dry chemical agents have been used. A good reference manual is The Handling and Storage of Liquid Propellents issued by the Office of the Director of Defense Research and Engineering, Washington, D. C. Approved dry-chemical extinguishing agents are not classified as toxic. Personnel of manufacturers and approval agencies have been exposed over a period of years to these dry chemicals and there have never been any ill effects reported. Persons inhaling dry chemical in high concentrations will experience discomfort because of the me chanical action of*the dry material on moist mucous membranes. Carbon Dioxide Although the possibility of using carbon dioxide as an extinguishing agent was recognized as early as 188228 it was not until the 1920's that liquefied carbon dioxide came into general use for this purpose. l The most important single factor in the successful development of portable carbon dioxide extinguishers was the use of an entrainment shield, or "horn," to limit the amount of air entrained by the carbon dioxide at the point of discharge. PORTABLE EXTINGUISHERS Approved hand portable carbon-dioxide extinguishers are available in capacities of 2 to 25 lb. The smaller sizes, 2 to 5 lb, usually have the discharge horn attached directly to the valve through a swivel connection and a metal tube. The larger extinguishers are equipped with both hose and horn. Most carbon dioxide wheeled extinguishers } ETC 03535 Fire Extinguishing Agents and Their Applications 507 are 50, 75, or 100 lb in capacity but there is one low pressure (re frigerated) wheeled unit of %ths ton capacity. With the single exception of the %ths ton unit, portable carbondioxide extinguishers consist basically of ICC 3A or 3AA cylinders for the storage of the liquid carbon dioxide (under a pressure of 850 psi at 70F), a valve for controlling the flow, a horn, and either metal tubing or flexible hose connecting the horn to the valve. The f extinguishers are always operated in the upright position and are provided with siphon tubes extending to close to the bottom of the cylinder so that liquid carbon dioxide is discharged from the orifice. As the liquid discharges from the orifice, within the horn, the carbon dioxide evaporates to form a mixture of gas and particles of solid carbon dioxide which forms an effective extinguishing stream as dis charged from the horn. HAND HOSE-LINE SYSTEMS There are two types of liquid carbon-dioxide storage used for both hand hose-line systems and fixed-nozzle systems. In one type of storage the liquid carbon dioxide is in ICC cylinders, either single cylinders or manifolded, under a pressure of 850 psi at 70F. These are called high-pressure systems. In the second type of storage, the liquid carbon dioxide is in insulated tanks under a pressure of 300 psi at 0F with the reduced temperature maintained by refrigeration units. This type of system is called a low-pressure system, and it is used only where the quantity of carbon dioxide in storage is %ths ton or greater. Hand hose-line systems consist of a supply of carbon dioxide, either under high pressure or low pressure, connected through piping to one or more hose lines on reels or racks. Like all hand hose-line systems, carbon-dioxide hand hose lines are used for the protection of specific hazards or supplementary to a fixed-nozzle system. FIXED-NOZZLE SYSTEMS Fixed-nozzle systems are designed for the protection of specific I hazards by local application or for the protection of rooms or buildings i by flooding. Although normally considered as an extinguishing agent I for Class B hazards, carbon dioxide in the proper concentration will extinguish fires in Class A materials in spaces that are tight enough to prevent leakage of carbon dioxide or entrance of air after the space has been flooded. For this reason carbon-dioxide flooding ETC 03536 508 Safety and Accident Prevention in Chemical Operationt systems are used for the protection of record vaults, fur-storage vaults and similar occupancies where the use of water would result in ex' cessive damage to the contents. However, precautions must be taken to insure that the doors to such storage spaces are not opened until the contents have cooled to a point where reignition will not occur when air is admitted. Carbon-dioxide extinguishing systems should be designed by, and the installation supervised by, qualified fire protection engineers on the basis of NFPA No. 12, Standard tor Carbon Dioxide Extinguish ing Systems.18 Spaces protected by fixed-nozzle carbon-dioxide systems should be provided with an adequate audible warning system with discharge of carbon dioxide delayed to allow personnel to leave safely. There is a considerable record of fatalities where personnel have been asphyxiated in protected spaces where no audible signal was pro vided. Carbon dioxide, being a gas, leaves no residue when it is used on a fire, and it is not decomposed by the flames to produce corrosive chemicals. Being a nonconductor of electricity, it is therefore an excellent extinguishing agent for use where there are delicate lowvoltage relays, as in a telephone exchange, or where electronic equip ment is involved in a fire. i EFFECT BY TEMPERATURE Normally the liquid carbon dioxide is expelled from its container by its own gas pressure. Portable extinguishers charged with the specified amount of carbon dioxide are approved for use from --40 to +120F. However, the flow rate is reduced at the lower tempera tures, and the fire extinguishing effectiveness is also reduced. The [ Underwriters' Laboratories recommends that the extinguisher be charged with only 90% of the normal amount for use at temperatures over 120F and up to 130F. When the extinguishers are to be used where-the temperatures will be very low, normal practice is to charge with carbon dioxide to 90% of the standard charge and supercharge with nitrogen. The same procedures may be followed with hand $ hose-line systems of the high-pressure type. Where low pressure systems are used at extremely low temperatures, it may be necessary to provide heating systems as well as refrigerating systems with thermostatic control to maintain the temperature of the liquid carbon dioxide in the vicinity of 0F. I ETC 03537 Fire Extinguishing Agents and Their Applications 509 Fixed-nozzle systems are designed to deliver carbon dioxide at specific rates of application, and where there may be considerable ranges of temperature, high-pressure storage systems should be so located that they may be heated should the temperature fall below 32F. At temperatures of over I20F, the carbon dioxide may be delivered from local application nozzles at too high a velocity and may splash flammable liquids as the result. Halon 1301 Bromotrifluoromethane, commonly called Halon 1301, is a liquefied compressed gas-extinguishing agent developed in the 1950's. Although jt has been used for several years as an extinguishing agent for fires in aircraft engines while in flight, it has only recently become available to civilian users in the form of an approved 2% lb hand portable extinguisher. Although Halon 1301 is a halogenated hydrocarbon, tests have shown that the undecomposed vapors of this agent are less toxic than carbon dioxide. However, whereas carbon dioxide is not changed in toxicity by exposure to flame, Halon 1301 is decomposed to form vapors which are toxic, even though far less toxic than the products of decomposition of carbon tetrachloride.11 Vaporizing Liquids TYPES Vaporizing liquid extinguishing agents have as their major com ponent carbon tetrachloride or chlorobromomethane. Both have addi tives to depress the freezing point to -- 50F. Carbon tetrachloride has a boiling point of 171 F and chlorobromomethane has a boiling point of 219F, and these agents are called "vaporizing liquids" because, although applied to a fire in the form of a liquid, they readily vaporize to form heavy gases that assist the extinguishing action by smothering the flames. Carbon tetrachloride-base extinguishers were first approved in 1912 and were the first to be approved for use on electrical fires and fires in flammable liquids. Chlorobromomethane was developed as an extinguishing agent by the Germans during World War II and approved extinguishers using chlorobromomethane-base extinguishing agent first appeared in the United States in the latter part of the 1940's. ETC 03538 510 Safely and Accident Prevention in Chemical Operations PORTABLE EXTINGUISHERS Approved vaporizing liquid extinguishers are available in sizes from 1 quart to 31/2 gal and the liquid is expelled either by pumping or by gas pressure from the stored pressure type using air, nitrogen, or carbon dioxide as expellant gases. Air and nitrogen are for all prac tical purposes insoluble in vaporizing liquids, but carbon dioxide readily dissolves in the liquids and the stream from a stored pressure ; extinguisher using carbon dioxide as the expellant gas is more of a ! spray than a straight stream because the carbon dioxide coming out of solution breaks up the stream into droplets. The Underwriters' Laboratories Incorporated lists vaporizing liquid extinguishers as suitable for use only on Class B and Class C fires. The Factory Mutual Laboratories, on the other hand, lists certain vaporizing liquid extinguishers as suitable for use on incipient Class A fires and on fires in electrical apparatus. "Specially designed" chlorobromomethane extinguishers are in addition approved for use on small flammable liquid fires. The stream range of 1 to 2% quart extinguishers is 16 to 28 ft and the range of large extinguishers is 30 to 35 ft. The larger stored pressure extinguishers are equipped with nozzles permitting the use of either a straight stream or a spray stream, the latter being more effective than the straight stream for use on fires in flammable liquids. The smaller extinguishers of this type are used primarily for pro tection of electrical equipment, industrial trucks, and over-thehighway trucks. The larger extinguishers are used primarily for the protection of electrical equipment. Vaporizing liquids have only a small fraction of the cooling effectiveness of water and therefore are not as effective on Class A fires as a similar quantity of water, and they are not as effective as multipurpose dry-chemical extinguishers of similar weight capacity. When vaporizing liquids are used on fires, corrosive fumes are liberated as the result of decomposition of the halogenated compounds. Accordingly, this type of extinguisher is not recommended where delicate electrical contacts may be involved or where fine tools or precision metal parts would be effected by corrosion. The practical effect of the vapors released or produced when vapor izing liquids are applied to a fire has long been a matter of contro versy. However, both the Fire Protection Equipment List of the Underwriters' Laboratories, Inc. and NFPA No. 10, Portable Fire ETC 03539 Fire Extinguishing Agents and Their Applications 511 Extinguishers, warn against the use of extinguishers of this type in confined spaces and recommend that operators and others should take precautions to avoid effects which may be caused by breathing the vapors or gases liberated or produced. Considerable discussion and data on the toxicity of vapors of various fire extinguishing agents may be found in NFPA Q 48-8 The Halogenated Extinguishing Agents. Using data presented in this booklet, Table 28.4 presents the com parative toxicities of agents that form gases or vapors. Carbon dioxide was assigned a value of 1 in this comparison because it is normally considered to be nontoxic and does not decompose when used on a fire. TABLE 28.4. Toxicity of Vaporizing Liquids Compared with Carbon Dioxide and Halon 130111 (Ratio basis: Carbon Dioxide = 1) Agent Carbon Dioxide Halon 1301 Chlorobromomethane Carbon Tetrachloride Natural Vapor 1.0 0.8 10.1 23.5 Decomposed 1.0 47.0 164.5 2195 The use of vaporizing liquid extinguishers may be prohibited in some states and municipalities. In addition, United States Coast Guard regulations have required that "Vaporizing-Liquid Type fire ex tinguishers, such as those containing carbon tetrachloride or chlorobromomethane, shall be removed from all vessels on or before January 1,1962."6 SPRINKLER UNITS There are two vaporizing liquid automatically operated sprinkler units, one containing 2 quarts of carbon tetrachloride and 1 pint of ammonium hydroxide (the latter to provide the expellant pressure and to counteract corrosion) and the other containing 1 gal of chlorobromomethane and pressurized with carbon dioxide. These units are intended primarily for protection where Class B fires may be expected and are limited in the volume of space that can be protected. Because of the limitations on installation recommended for these units by the Underwriters' Laboratories, Inc., reference should be made to the Eire Protection Equipment List published by the approval agency. f ETC 0354 0 512 Safety and Occident Prevention in Chemical Operations Dry Powders for Fires in Combustible Metals APPROVED AGENTS The first approved agent specially compounded for extinguishin fires in combustible metals was made available in 1940 as the result of the increasing use of magnesium in aircraft construction. This first approved dry powder is composed of a commercial grade of graphite to which an organic phosphate has been added. The graphite absorbs heat from the fire, and the organic material breaks down to a gas that penetrates the spaces between the graphite particles, excluding air. Because the powder cannot be discharged through pipe or hose it is applied to a fire by means of a scoop or shovel. A second dry powder for use on fires in combustible metals was approved in 1958. The major component of this dry powder is sodium chloride with a noncombustible thermoplastic material added to bind the particles of sodium chloride together when exposed to the heat of a fire. The dry powder contains other ingredients to pro duce good flow characteristics, and it is treated with metal stearates to produce moisture repellency. This agent cannot only be applied with scoop and shovel but it can also be discharged from fire-extinguishing equipment/ Portable fire extinguishers ranging in size from 30- to 350-Ib capacity, charged with this agent, are approved for use on fires in combustible metals.22 Although the two dry powders are approved for use only on mag nesium, powdered aluminum, sodium, potassium, and sodium-potassium alloy (NaK), in practice they have been used successfully on fires in other combustible metals such as titanium, zirconium, and uranium. The sodium chloride-base dry powder, because of its good flowcharacteristics, can be applied through systems of piping and fixed nozzles and a number of such installations have been made. Such installations are used to protect liquid metal pumping, storage, and filtering systems where the liquid metal is used as a heat transfer medium in connection with atomic power reactors. Under these con ditions, fire fighting with manual equipment is impractical, and the extinguishing agent for the combustible metal must be applied through piping. A system typical of this type is designed to discharge 8000 lb of the sodium chloride-base dry powder from four 2000 pound units. There has been a very limited amount of fire experience with such systems. Fire Extinguishing Agents and Their Applications 513 UNAPPROVED agents There are several nonapproved dry powders that have been specially compounded for the extinguishment of fires in combustible metals. One is primarily composed of a hard graphitic material that can be discharged from fire extinguishing equipment. Although this agent was originally compounded primarily for the extinguishment of fires in lithium, which are very difficult to extinguish because of the very low specific gravity of the liquid metal, it has been used successfully on many other combustible metals. There are two other dry powders specially compounded for use on fires in combustible metals and intended for application by scoop or shovel. The first is a shale-like material mixed "with tar or pitch and ammonium chloride. The second originated with the United Kingdom Atomic Energy Authority and is a patented mixture of sodium chloride, potassium chloride, and either barium chloride or lithium chloride, in such proportions as to form a eutectic mixture having a melting point between 900 and 1100F.2 Many materials have been used on metal fires with varying degrees of success. Some materials readily absorb moisture and must be kept in tightly sealed containers. Others are successful in extinguishing small fires where large masses of material may be applied but may react with the burning metal if the fire is of considerable size. The following materials have been used on a variety of metal fires: foundry flux, lithium chloride, sodium chloride, zirconium silicate, Dolomite, soda ash, asbestos powder, talc, graphite, sand, and cast-iron borings. Multipurpose dry chemical is not suitable for use on fires in com bustible metals. Although under certain circumstances small mag nesium fires may be extinguished, under other circumstances there may be a reaction between the burning magnesium and multipurpose dry chemical. The latter also reacts violently with burning lithium. There are three liquid agents that are prepared especially for the extinguishment of fires in combustible metals. None is approved. One is a petroleum derivative applied from 2-quart and 2y2-gal stored pressure extinguishers. The liquid acts as a cooling and smoth ering agent and under certain conditions, it is flammable. However, j the application of additional liquid, if available, is said to cool the ! burning material below the fire point. It is suggested for use on only small magnesium fires. A second liquid agent is composed primarily ! of peanut oil which is discharged from an extinguisher pressurized ETC 03542 514 Safety and Accident Prevention in Chemical Operations with carbon dioxide. The extinguisher has a capacity of 2y2 gal 0f oil and \y2 lb of carbon dioxide, the latter being in a separate con- tainer within the body of the extinguisher. A three-way valve allows first the discharge of the oil to act as a cooling and smothering agent with a final discharge of carbon dioxide to extinguish any fire which may result in the peanut oil. This agent also is suggested for use only on small magnesium fires. The best known liquid extinguishing agent for fires in combustible metals is trimethoxyboroxine (TMB). TMB is applied from a 2i/o-gai stored pressure extinguisher which has a nozzle permitting use of either a spray or a straight stream. TMB is a flammable liquid organo-metallic compound similar in flammability characteristics to methyl alcohol. It burns with a green flame, liberating large volumes of dense white fumes. A glassy boric oxide coating remains on the metal. This coating will pick up moisture very rapidly from a humid atmosphere. The use of TMB as a fire extinguishing agent for com bustible metals is patented. The Naval Research Laboratory developed the TMB extinguisher for use on magnesium castings and structural shapes under aircraft crash fire conditions. L'nder these conditions of application, fast extinguishment results which can be quickly followed up by foam or water. TMB extinguishers are used primarily by the United States Navy Bureau of Weapons on crash fire and rescue trucks. Although the flammability and heavy fuming characteristics of TMB may be undesirable under conditions of industrial fire fighting indoors, TMB is a good extinguishing agent for fires in oily or dry magnesium chips, turnings, or castings. It is also suitable for control and, in most cases, extinguishment of fires in titanium chips, turnings, sponge, and powder. TMB will control, and in some cases, will com pletely extinguish fires in zirconium chips or turnings. TMB is not recommended for fires in sodium, potassium, sodiumpotassium alloy (NaKl or lithium. TMB reacts violently with lithium and NaK. Where combustible metals may ignite in enclosed equipment such as heat-treating furnaces, gaseous extinguishing agents may be used. Boron trifluoride and boron trichloride will control and sometimes extinguish magnesium fires in heat-treating furnaces. Boron trifluoride is considerably more effective than the boron trichloride. The gases may only control large fires which may require the application of suitable dry powders for extinguishment. The fumes of these gaseous agents are toxic and irritating, and suitable gas masks should be available. Fire Extinguishing Agents and Their Applications 515 Argon, helium, and, sometimes, nitrogen can also be used to ex tinguish fires in combustible metals in enclosed spaces. Caution should be exercised in the use of nitrogen however, because this gas reacts readily with certain burning metals. If there is uncertainty as to whether a metal will burn in a nitrogen atmosphere, the applica tion of a small amount of water to the residue of the metal burned in air will result in an odor of ammonia if the metal reacts with nitrogen. Argon and helium, of course, will not react. Steam Steam is the oldest of the smothering agents although it is seldom used in modern practice, having been replaced by carbon dioxide and other inert gases. It is most effective when used for the protection of relatively small spaces such as ovens at temperatures of 225F and higher. The visible cloud of condensed vapor has little smothering action and will act mainly through cooling. Large volumes of steam are usually necessary because of the rapid condensation that takes place unless the walls of the enclosure are above the boiling point of water. Steam should not be used for protection against fires in cotton, paper, wood pulp, and similar carbonaceous materials, because the charcoal produced by the fire will reignite by spontaneous heating very quickly after the steam has been shut off and air is introduced. The best information on steam smothering systems is in NFPA No. 86 Standards on Class A Ovens and Furnaces-3 Steam hose lines are sometimes used for extinguishing small fires in flammable liquids such as those that may occur from a leak in a pipe line. 28.4. MECHANISM OF EXTINGUISHMENT Flames exist when there is a fuel, a substance which readily reacts with the fuel, and sufficient heat to speed the reaction to a point where visible and infrared radiation takes place. A familiar, and over simplified, version of extinguishment states that it is accomplished by removal of the fuel (by blanketing with foam or interposing a layer of inert gas between the fuel and the flames), by removal of oxygen (by dilution with inert gases or vapors), or by removal of heat (by cooling with water or other extinguishing agents). All of the foregoing explanations of extinguishing action are correct but are insufficient in themselves to explain w'hy loaded stream extinguishers are more ETC 0.154 4 516 Safety and Accident Prevention in Chemical Operations effective than plain water extinguishers, why Halon 1301 is more ef fective than carbon tetrachloride, or why potassium bicarbonate-base dry chemical is more effective than sodium bicarbonate-base dry chemical. It can be said with considerable confidence that water, whether in the form of a straight stream or a spray, with or without wetting agent acts for all practical purposes entirely as a cooling agent for the removal of heat. Wood and similar Class A materials burn only when heated to the point where destructive distillation results in the evolu tion of combustible vapors. The cooling action of water stops the evolution of combustible vapors and the fire is extinguished. Water spray and "fog" are practically effective only on flammable liquids having flash points in excess of 150F. It is therefore obvious that even on Class B fires the cooling action of the water is of greatest importance. The cooling action of water sometimes allows extinguishment of fires by application at very high rates of flow where low rates of flow wrould only increase the intensity of the fire because of chemical re action between water and the burning material. One familiar example is the extinguishment of a fire in charcoal. If water is applied at too low a rate of flow, the well-known water-gas reaction takes place: H20 + C -* H2 + CO At high rates of application, the cooling effect of the water reduces the temperature to a point where the foregoing reaction will not proceed. Another good example is the extinguishment of fires in magnesium castings. Applied at too low a rate, the wTater reacts w'ith the burning magnesium: H20 + Mg-- H2 + MgO Applied at high rates of flow, the water cools the castings to the point where combustion no longer is sustained. Loaded stream extinguishers containing a solution of potassium carbonate are more effective than extinguishers containing plain water not only on Class A fires but on Class B fires also. There are only theories as to why the addition of potassium carbonate to water increases the extinguishing effectiveness.30 However, in addition to the cooling action of water it is possible that the heat of the fire evaporates the solution to leave solid particles of potassium carbonate that act in the same way as dry chemical to interrupt and suppress the chain reaction of the flame. Carbon dioxide can be considered for all practical purposes to act ETC 03545 Fire Extinguishing Agents and Their Applications 517 as a diluent to both fuel vapors and oxygen. When sufficient carbon dioxide is introduced into the fire area, the reacting materials are diluted to the point where the reaction cannot proceed with sufficient rapidity for the flames to exist. Where carbonaceous material is in volved in a fire, however, reignition takes place unless it is possible to maintain a sufficient concentration of carbon dioxide until the previously burning material has cooled. Although the action of halogenated extinguishing agents, such as Halon 1301, chlorobromomethane, and carbon tetrachloride, was once thought to be entirely because of cooling action and smothering because of the dilution of fuel vapors and air, it is now believed that the major extinguishing mechanism results from pyrolysis of the halogenated hydrocarbons and reaction of the resulting radicals with the active radicals present within the flame zone. Generally speaking, a halogenated hydrocarbon containing bromine is a more effective extinguishing agent than a halogenated hydrocarbon containing only chlorine, but the effectiveness does not depend only upon the percent of bromine in the molecule. Published data do not satisfactorily explain why Halon 1301 (bromotrifluoromethane) has such high ex tinguishing effectiveness as compared with other halogenated hydro carbons. The extinguishing action of foam is obvious in that it forms a barrier that prevents contact between fuel vapors and air. The extinguishing action of dry chemicals has been given a great deal of study in recent years, but no one theory as to the mechanism involved has gained complete acceptance. Originally, it was thought that sodium bicarbonate decomposed upon striking-flame to give off carbon dioxide and w'ater vapor and extinguish the fire by simul taneously cooling' and smothering. It is now known that, although this may occur, it is not an important factor because equally finely divided sodium chloride treated to flow and discharge properly is an effective dry-chemical extinguishing agent. One modern theory of the extinguishing action of dry chemical is that the fine particles capture sufficient of the free radicals in the flame zone to interrupt the chain reaction and suppress the flame practically instantaneously.8 Op ponents of this theory have pointed out that the mathematics involved, which relate to the diffusion of free radicals from the flame zone to the surface of the dry-chemical particles, can equally well support a theory that the dry-chemical extinguishing action is because of transfer of heat from the flame to the particles. The relation between particle size and surface area of dry chemicals and the extinguishing effectiveness has been reported by several tiHYL CQRPOHJTISN CHEMICAL LEYEIMMEHT LIBRARY r. o. BOX 341 BATftN R8U8E1, LOUISIANA ETC 03546 r 528 Safety and Accident Prevention in Chemical Operations sources.8-10 Experimental and theoretical studies have showed that the extinguishing effectiveness increases as particle size decreases and surface area increases. The most recent theory on the extinguish^ mechanism of dry chemicals is that evaporation takes place and that the evaporated material acts as a flame inhibitor.29 Using this theory also, the smaller the particle size, the more rapidly the particles will be heated to a temperature at which evaporation can proceed. The theory also takes into account "metal availability" in the salt which is inconsistent with the experimental evidence that ammonium phosphate-base dry chemical is more effective as an extinguishing agent on Class B fires than sodium bicarbonate-base dry chemical. In summary, presently there is no completely satisfactory ex planation as to how powdered solids extinguish' fires or completely satisfactory explanation for the greater extinguishing effectiveness of ammonium phosphate and potassium bicarbonate. The effectiveness of monoammonium phosphate-base multipurpose dry chemicals on fires in Class A materials is probably because of a dual extinguishing action. The flames are extinguished by an unknown mechanism as discussed in the foregoing paragraphs. The mono ammonium phosphate is decomposed by the heat and leaves a residue of phosphoric acid or phosphoric anhydride on the material which had been burning. This residue prevents afterglow which would lead to renewed flaming. The use of monoammonium phosphate-base dry chemical on a wood fire results in a fire retardant coating that is very effective in pre venting reignition. This was discovered in trying to dispose of the charred 2 x 4's remaining from large Class A fire tests in which 18,000 board feet of lumber was used. The 2 x 4's on which water had been used were easily disposed of by burning, but a pile of charred 2 x 4's on which multipurpose dry chemical had been used resisted reignition to such an extent that it was necessary to haul them to the public dump. 28.5. COMPARATIVE EXTINGUISHING EFFECTIVENESS OF AGENTS Evaluation of the effectiveness of extinguishing agents can be ac complished by several methods, but the final criterion is the effective ness in actual use. Data gathered on the laboratory bench are of value only for the preliminary screening of agents for special applica tions. For example, data obtained by the peak flammability explosion buret method14 do not correlate xvith fire extinguishing effectiveness data obtained with fixed nozzles and a 3 ft diameter gasoline fire.8 ETC 0.3 54 7 1 Fire Extinguishing Agents and Their Applications 519 The data obtained in tests with fixed nozzles may be used to predict the effectiveness to be expected in practice with fixed-nozzle local application systems. In the use of manually operated fire-extinguishing equipment, the evaluation is really that of a combination of agent and equipment, and many variables can effect the results. For example, a fire fighter skilled in the use of one agent may not be adequately skilled in the use of other agents. Fire tests made with flammable liquids in depths of over 1*4 in. are much more severe than fire tests that simulate spill fires. Also, an agent that may be excellent for extinguishing fires in flammable liquids in tanks or on spill fires, may be valueless when the flammable liquid is escaping under pressure or even just flowing. The extinguishment of flammable liquid fires indoors is more difficult for the less experienced operator than if the same size fire is attacked out-of-doors. The Underwriters' Laboratories uses wood panel fires and wood crib fires for determining the Class A rating of fire extinguishers, and observation of many tests shows that water ex tinguishers are more effective on the panel fires than on the crib fires whereas multipurpose dry-chemical extinguishers are more effective on the crib fires. Two fire extinguishers containing exactly the same amount of the same agent may have widely different degrees of fire extinguishing effectiveness. Two important factors that determine effectiveness are the type of stream expelled from the nozzle and the rate of application of the agent. The rate of application of an extinguishing agent is of critical importance. If the rate is too low, the fire may not be extinguished, and if the rate is too high the supply of agent may be exhausted before the fire is extinguished.'8 Where unlimited water supplies are available, it is obvious that the higher'the rate of application, the sooner the fire will be extinguished. However, the statements re garding rates of application are also applicable to portable fire extinguishing equipment, to hose-line systems using special extin guishing agents, and even to systems employing fixed nozzles. The Underwriters' Laboratories in its test and examination of equipment submitted for listing evaluates the extinguishing effective ness of agent and equipment as an integral unit. For example, in order to obtain a Class A rating the submitted equipment must be able to extinguish standard wood crib, wood panel, and excelsior fires. The extinguishment of these fires is a function of the rate of discharge, the amount of extinguishing agent, and the type of discharge stream. Until recently the Underwriters' Laboratories Inc. had no standard ETC 03548 ETC 03549 Also listed as suitable fo r use on Class B and Class C fires. Fire Extinguishing Agents and Their Applications 521 fire tests for ratings in excess of 4-A and water extinguishers were assigned ratings based on 759& of that which would be obtained by using proportionate values given to Class A extinguishers of lower capacity. However, when wheeled multipurpose dry-chemical ex tinguishers were submitted for examination and test, the Laboratories developed evaluation procedures using large wooden cribs made up of 2 x 4's. Tests with these large standard Class A fires verified the ratings previously given to large water extinguishers. A fire extinguisher having a capacity of lVi gal of water and other wise meeting the requirements of the Underwriters' Laboratories will, when used by an expert operator, consistently extinguish a standard 1-A test fire. Table 28.5 shows the maximum effectiveness on Class A fires of Underwriters' Laboratories listed extinguishers where only the highest ratings for each size of extinguisher are used. The L'nderwriters' Laboratories procedures for assigning Class B ratings are considerably more involved than the procedures used for assigning Class A ratings. The fire tests are run using square steel pans with white gasoline as the fuel. Ordinary motor gasoline is not used because of the variation in volatility in winter and summer. The fuel is in 2 in. depth with 6 in. of tankside above the surface of the fuel. The fire is allowed to burn for one minute before being attacked. The test pans used by the Laboratories in the Class B fire tests are, in area, 2Vo, 5, 10, 15, 20, 25, 30, 40, 50, 100, 200, 300, 400, 500, and 600 sq ft. The Underwriters' Laboratories uses expert operators to determine the maximum area extinguished consistently by one extinguisher. To obtain the Class B rating, the maximum area as determined by test is multiplied by 0.40 to give the rating. The latter is intended to repre sent the flammable liquid area that might be expected to be extin guished by inexperienced operators. Fire tests with hand portable extinguishers are run indoors in a test house having a 40 by 60 ft floor area with the ceiling height in excess of 20 ft, and always with large roof vents opened. The largest indoor fire is 50 sq ft which imposes a limit of 20-B as the highest rating presently obtainable with hand portable fire extinguishers. Extinguishing equipment larger than hand portable in size is tested on outdoor fires but only when the wind velocity is less than 10 miles per hour. The maximum effectiveness of Underwriters' Laboratories listed extinguishers on Class B fires is shown by Table 28.6. It will be noted that 20-B ratings are obtained with potassium bicarbonate-base dry chemical extinguishers of only 9 lb capacity. The same rating is given to extinguishers of this type containing 18 ETC 03550 ETC 03551 Also listed as suitable fo r use on Class C fires. Also listed as suitable fo r use on Class A fires. Fire Extinguishing Agents and Their Applications 523 and 27 lb of dry chemical although it is obvious that they must have considerably greater extinguishing affectiveness. Using the data of Table 28.7 and taking into account the variations because of size, the extinguishers may be assigned approximate values to indicate relative effectiveness as shown below. ? TABLE 28.7. Relative Extinguishing Effectiveness of Underwriters' Laboratories Listed Extinguishers on Class B Fires Basis: Comparative weights of extinguishing agents for equal class B rating Agent Potassium bicarbonate-base dry chemical Multipurpose dry chemical Sodium bicarbonate-base dry chemical Halon 1301 Carbon dioxide Chlorobromethane Carbon tetrachloride Foam Loaded stream Relative Effectiveness 100 71 67 46 19 18 14 5 1 The Underwriters' Laboratories assigns Class C ratings to extin guishers having Class B ratings where the extinguishing agent is not a conductor of electricity. In the past, extinguishers rated for use on both Class A and Class B fires were not rated for use on Class C fires because the extinguish ing agents were electrically conductive. Also, extinguishers rated for use on both Class B and Class C fires were not sufficiently effective on Class A fires to obtain Class A ratings. Multipurpose dry chemical, * being electrically nonconductive and also effective on Class A fires as well as Class B fires, has permitted the listing of extinguishers for i all three classes of fires. Because there are many locations where protection must be furnished for more than one class of fire, Table 28.8 lists extinguishers approved as suitable for use on both Class A and Class B fires. There are two agents approved for use on fires in combustible metals. Because of the complexities of determining comparative ex tinguishing effectiveness, no numerical ratings are assigned. Reference must be made to the respective lists of approved equipment for infor mation as to the combustible metals for which the extinguishing agents are considered suitable and for guidance as to the quantities of agents required on various metal fires.5'32 ETC 03552 524 Safety and Accident Prevention in Chemical Operations TABLE 28.8. Maximum Effectiveness of Extinguishers Approved by the Underwriters' Laboratories as suitable for use on both Class A and Class B Fires32 (Weights and volumes denote nominal extinguisher charge) Underwriters' Laboratories Class A:B Rating 1-A: 2-B 1-A'. 16-B 2-A: 1-B 2-A: 6-B 2-A: 20-B 3-A: 20-B 4-A: 6-B 4-A: 20-B 10-A: 12-B 20-A: 40-B 20-A: 80-B 40-A:160-B M ultipurpose Dry Chemical* lb -- v/2 -- -- 10 17 -- 20 -- -- 125 300 Foam Pounds (Gallons) 10.4 20.8 41.7 142 275 UK) -- -- (2 y2) -- -- (5) -- (17) (33) -- -- Loaded Stream Pounds (Gallons) z 28.7 -- m -- -- -- -- -- -- -- -- -- * Also listed as suitable for use on Class C fires. The coordination of fire-protection systems in a chemical operation is beyond the scope of this chapter, but the reader is referred to his insurance carrier, to the N.F.P.A. and to the cited reference.34 REFERENCES 1. A. W. Bertschy, H. E. Moran, and R. L. Tuve, Lithium Chloride Solution for Fire Extinguishers Exposed to Low Temperatures, Naval Res. Lab. Rpt. 4853 (1956). 2. L. H. Cope (to the U.K.A.E.A.) Brit. Pat. 884,946 (Dec. 20, 1961). 3. Factory Mutual Engineering Division, Handbook of Industrial Loss Prevent tion, McGraw-Hill Book Co., New York, 1959. 4. Factory Mutual Engineering Division. "Cotton Process Fires," Loss Preven tion Bulletin 12.75, Norwood, Mass., 1948. 5. Factory Mutual Engineering Division, "Approved Equipment," Norwood, Mass., 1961. 6. Federal Register, Washington, D. C. (Sept. 6, 1958). 7. A. B. Guise, and J. A. Lindlof, "A Dry Chemical Extinguishing System," N.FPA. Quart., 49, 52 (1955). 8. A. B. Guise, "The Chemical Aspects of Fire Extinguishment," N.FPA. Quart., 53, 330 (1960). L ETC 03553 Fire Extinguishing Agents and Their Applications 525 9. D. Hird, "'Extinguishing Room Fires with High and Low Pressure Water Sprays," WF.D.B. Zeit., 9 (Special issue), 58-61 (I960). 10. D. Hird, and M. J. Gregsten. "Particle Size and Efficiency of Dry Powders," Fire Protection Review. 19, 473 (1956); and Fire, 49, 101 (1956). 11. J. E. Malcolm. "Halogenated Extinguishing Agents," N.FPA. Quart., 45, 119 (1951). f 12. Manufacturers Mutual Fire Insurance Co., The Factory Mutuals, 1S35-19S5 ti (1935). 13. A. F. Matson, and R. E. DuFour, "The Mechanism of Extinguishment of Fire by Finely Divided Water," Nat. Bd. of Fire Underwriters Res. Rpt. 10 (1955). 14. H. E. Moran Jr., "Developments in Fire Extinguishers," Proc. of the Symp. on Fire Extinguishment Res. and Eng'g., U. S. Nav. C. E. Res. and Eval. Lab., Port Hueneme, Cal. (1954). 15. National Board of Fire Underwriters, "Characteristics of Water Spray Nozzles for Fire Fighting Use," (1944). 16. National Fire Protection Association, Standard'No. 10, National Fire Codes, VIII (1963-1964). 17. National Fire Protection Association, Standard No. 11, National Fire Codes, VII (1963-1964). 18. National Fire Protection Association, Standard No. 12, National Fire Codes, VII (1963-1964). 19. National Fire Protection Association, Standard No. 15, National Fire Codes, VII (1963-1964). 20. National Fire Protection Association, Standard No. 17, National Fire Codes, VII (1963-1964). 21. National Fire Protection Association, Standard No. 18, National Fire Codes, VII (1963-1964). 22. National Fire Protection Association, Standard No. 48, National Fire Codes, III (1963-1964). 23. National Fire Protection Association, Standard No. 86A, National Fire Codes, IX (1963-1964). 24. National Fire Protection Association, Standard No. 409, National Fire Codes, X (1963-1964). 25. P. Nash, "Some New Techniques in Fighting Fires," Fire, 541 (1956). 26. R. R. Neill, "The Hydrocarbon Flame Extinguishing Efficiencies of Sodium and Potassium Bicarbonate Powders," Naval Res. Lab. Rpt. 5183 (1958). 27. H. B. Peterson, R. L. Tuve, R. R. Neill, J. C. Burnett, and E. J. Jablonski, "The Development of New Foam-Compatible Dry Chemical Fire Extinguish ing Powders," Naval Res. Lab. Rpt., 4986 (1957). 28. E. L. Quinn, and C. L. Jones, "Carbon Dioxide," ACS Monograph, Reinhold Publishing Corp., New York, 1936. 29. W. A. Rosser Jr., S. H. Inami, and H. Wise, "Study of the Mechanisms of Fire Extinguishment of Propellants," ASD Technical Rpt., 61-143, Aero nautical Systems Division, Wright-Patterson Air Force Base, Ohio (1961). 30. C. A. Thomas, and C. A. Hochwalt, "Effect of Alkali-Metal Compounds on Combustion," Ind. Eng. Chem., 20, 575 (1928). i 31. R. L. Tuve et al, "A New Vapor-Securing Agent for Flammable-Liquid Fire i Extinguishment," Naval Res. Lab. Rpt. 6057, 1964. ETC 03554. I 526 Safety and Accident Prevention in Chemical Operations 32. "Fire Protection Equipment List," Underwriters' Laboratories, Inc., Chic Illinois, 1964. ' ag0' 33. E. D. Zeratsky, "Special Dry Powder Extinguishing Agents," NFPA 54, 154, 1960. H' 34. Natiunal Safety News, entire issue on fire protection, 90, 1 (July, 1964). 4 J ETC 03555 1 29 Action Stations and Disaster Planning Alan L. Kling It is not uncommon in a metropolitan area to see streets partially blocked with barricades, flashing lights, and signs which read, "Dig we must--for a growing New York." This is a way one of our large, progressive utility companies offers apology for any traffic inconven ience which it might be causing. At the same time, the message is a rather subtle reminder to the public, their customers, that they have a long-range plan in operation and are getting ready today for the demands of tomorrow. This is precisely what we do in industry when we take preparatory action for possible future emergencies, and we might well paraphrase the electric company's slogan so that for our use it would read, "Plan we must--for greater security and better control of losses." Sometimes there is ample warning of an impending emergency, such as when a hurricane or flood is headed our way, but more often, major trouble comes with the awful suddenness of an explosion or fast-spread ing fire. There are, of course, other types of abnormal conditions, such as riot, civil commotion, wildcat walkouts, or unfavorable changes in the international situation. These are difficult to predict and hard 1 to handle, but they too have "panic-button" characteristics which j demand immediate attention. Regardless of how these conditions might ; develop, every prudent plant manager knows that a time could come ! when he would have to acknowledge that a catastrophe had overtaken j him, and he was knee-deep in disaster. Like Artemus Ward, one of i 527 ETC 03556 r 528 Safety and Accident Prevention in Chemical Operations America's earliest commentators, he would have to say, "The Fack can't be no longer disgised that a Krysis is onto us." How well the chief executive officer, whether he is called president operating head, or plant manager, fulfills his responsibility for the safety of personnel and the protection of property will depend, in large part, on the plans which he has formulated and put into practice. The response of a company to a catastrophe will be reflected in the actions of every employee. If there has been preparation and training, control measures will be initiated automatically. Injury and physical damage will be kept at a minimum and recovery will be prompt and positive. Without forethought and planning, minor emergencies can become major disasters, and what might have been merely a delaying incident can very quickly become the final scene in a costly and unhappy tragedy. Emergency preparation has been a frequent topic for discussion. There have been American Management Association conferences, gov ernment briefing sessions, and instructive meetings and field trips such as those sponsored by the National Institute for Disaster Mobilization. Many articles have been wrritten which help outline procedures and summarize experience of both large and small companies. There is an immense quantity of reference material available, and information on any phase of emergency planning can be obtained without much difficulty. Competent personnel can also be found who will provide excellent consulting service. Many companies appear reluctant to plan for a total emergency. We have lived near war for such a seemingly long period of time that complacency comes easy, and in time of peace or even cold war, na tional security does not have quite the priority over the immediate problems which must be handled in the office and shop on a daily rou tine basis. Actually no management is fulfilling its responsibility if it does not prepare plans which are broad enough to include its own security and future continuity. These are many compelling reasons why a comprehensive approach is important, and if the need is prop erly evaluated, sufficient time and talent can be found in every organi zation. The task of preparing a program will look less formidable if respon sibility centers are established for specific emergency functions. These action stations, when properly coordinated, will provide an adequate and effective over-all plan for total emergency. What are some of the specific functions which must be considered? There are not too many, and each has been covered in considerable detail in previous conferences and publications. However, the follow- ETC 03557 Action Stations and Disaster Planning 529 ing brief check list, with annotations, will serve as a reminder- for those who are either developing a new plan or evaluating one which already exists. ; CHECK LIST FOR TOTAL EMERGENCY PLANNING i ' 1. Policy. Top management must state its philosophy indicating the importance it places on emergency planning and the extent to which it expects action. 2. Organization. Size and type of operation will dictate whether f f a full-time security officer should be appointed. A committee, in spite of frequent cynical comments about the ineffectiveness of such a group, can be productive if it has qualified leadership. For most companies the most practical plan appears to be assignment of specific functions to various department heads and coordination by one individual who regularly prepares status reports for top management. Regardless of the manner organized, there must be definite assignment of responsibility, coordination of activities, and periodic review of results. 3. Continuity of Management. The strength of a company depends not only on the ability of its officers but also upon their availability. Corporate by-laws must permit legal transaction of necessary busi ness under emergency conditions with only a minimum number of directors. A chain of command should also be established so that there is no doubt or confusion as to who has the authority for making or approving all decisions. The managers of plants which are distant from a central corporate office and which could become isolated should have their scope of responsibility so broadened that under emergency conditions they can, at least on a temporary basis, take whatever action is necessary. 4. Alternate Headquarters. Under some conditions an office with minimum supplies and records might be desirable, but the most practical approach for most companies is the designation of a rendezvous point where officers and designated staff and line per sonnel can meet to assess the situation, initiate recovery or receive instructions from the government if the occurrence involves national welfare. ! 5. Vital Records. Good management safeguards its legal documents, accounting records, and operating data as a matter of course, and planned protection is imperative even for normal conditions. 6. Money and Banking. In multiplant companies each separate lo cation must be certain it has access to temporary operating funds. ETC 03558 ii 530 Safety and Accident Prevention in Chemical Operations 7. Process Data and Man-power Inventory. Information should available as to raw materials sources, product specifications ^ erating data, and the administrative and operating skills avai]au within a company. 1 8. Communications. The problem of making contact with separated locations is primarily one for multiplant companies but even a single unit operation must be able to communicate with suppliers, customers, and under conditions of national emergency with the government itself. ' 9. Government Contact. The federal government and many of the IT states have made extensive plans for handling emergencies which are national in scope. Some industries, or plants within those industries, have been designated as key facilities. Every company should determine what its function will be under total emergency conditions, and how it will establish communication with designated government officials. ii 10. Plant Emergency Programs. The smooth, normal operation of a production unit can find itself in the middle of a crisis without much prior notice. Because modern plants are so highly integrated all facilities wall be effected. Detailed emergency plans will assign responsibility, outline a desired course of action, and establish means of coordination. 11. Post-Attack Planning. Thought must be given to recovery so that company assets, not totally destroyed, can be salvaged and production re-established, at least on a partial basis, as quickly as possible. All of the items included in this check list envision preparation for a major emergency, one that is national in scope and of catastrophic proportion. Whether such a situation will ever develop is one of the perplexing questions which only future events can answer. There are few persons, if any, who would consider themselves qualified to assess the probability of a nuclear attack on this country. On the other hand, it would be hard to find a normal individual who would not readily admit the possibility of an all-out war involving all nations, even before the end of this century. So, plan we must for our own security. Those who do will have all of the survival odds in their favor. 29.1. IN-PLANT EMERGENCY PLANNING We must also plan for better loss control on a day-to-day basis, because if the future is in any way similar to the past, we can expect ETC 03559 Action Stations and Disaster Planning 531 fires, explosions, and other unscheduled, unplanned, unwanted, costly, abnormal occurrences which if not properly handled will adversely af fect a company's position in the highly competitive market place, and actually challenges its economic survival. Defensive planning consists of establishing and co-ordinating action stations within a plant so that strong control measures can be brought to bear quickly and effectively on any of the many emergency situa tions which can occur. Action stations are really responsibility centers from which response is automatically initiated in time of need. Management specifies their location, the personnel who will serve, and the scope of their duties. It specifically defines an "emergency condition," grants authority for making emergency decisions, and provides means for declaring that an emergency situation exists. Because organization and facilities vary from one company to another, what are crises for some locations may be minor inconven iences for others. In a plant that has no automatic sprinklers, no trained fire brigade, and is dependent on a volunteer or distant munic ipal fire department, even a small blaze constitutes a first-order emer gency. Usually, however, an emergency can be defined as: 1. An accident causing fatal or severe injuries. 2. A fire or explosion in which damage exceeds a specified amount determined by management. 3. Actual or impending severe storm or flood conditions. 4. Any incident which could affect community relations, such as ac cidental discharge of toxic or noxious materials into the atmosphere or local waterways. The management statement of emergency policy will clearly desig nate the line of authority and will make certain that persons who can make decisions are on hand and available at all times. There must be someone in responsible charge empowered to activate the emergency plan in full and complete detail. A method of communication is needed so that all action stations can be notified. This can be a siren, bell, horn, public address system, or the telephone, but whatever system used, it must be dependable. Management may also want to designate a coordinator. In some companies, a full-time security officer may be required, but generally, where responsibility for specific functions is delegated to personnel in many departments, the main job is one of careful integration. This can, and often is, a part-time job. 03of>0 ETC 532 Safety and Accident Prevention in Chemical Operations CONTROL CENTER An emergency of any size or duration must have a command or control center. It is the focal point for communications, both within the plant and for incoming and outgoing calls. The individual in charge should make this his headquarters so that he can be reached easily. Time is one of the most essential elements in an emergency program, and many decisions simply will not wait until someone in charge can be found. Alternate locations should also be designated to provide flexibility. Often the guard headquarters at the main gate is an ideal place for the control center, but the plant manager's office the purchasing department (because of generally easy access for out-! side visitors), production center or the insurance manager's office are possibilities. CONTROL FACILITIES Several plant groups are needed at the scene of an emergency to properly handle injured personnel and to initiate control measures. Most large companies have well-trained fire brigades on every shift with maintenance men, such as electricians, pipe fitters, and riggers, as well as members of the yard crew with their trucks, responding to all fire calls. If no brigade exists, selected employees should be trained in fire-fighting techniques; actually it is a worthwhile practice to teach all personnel the proper use of portable extinguishers. MEDICAL SERVICES Within a plant there may be a full-time physician, one or more nurses, or only a first-aid squad. In addition to their availability in time of emergency, they must also have quick access to stretchers, resuscitators, and various medical supplies. Sometimes these are car ried on the fire truck, ambulance, or special vehicle equipped for the purpose. The plant protection groups, guards and watchmen, control the gates, handle traffic, safeguard property and often are key men in the communication system. Technical personnel, chemists and en gineers, are often needed at the site of a disaster to give advice and suggestions to firemen and others regarding toxicity and flammability of materials involved. ETC 03561 Action Stations and Disaster Planning 533 PERSONNEL PROTECTION The safety director frequently has a wide-ranging assignment for both prevention of injury and conservation of property. If he has not permitted himself to become desk bound, but gets out into the plant regularly, he will be intimately familiar with the people, equip ment, and products. This makes him well qualified to either direct the control facilities or advise those in charge of each of the individual functions. INDUSTRIAL RELATIONS Some of the most unpleasant and frustrating jobs fall into the lot of the industrial relations manager and his staff; most of them require an extra measure of patience, compassion, tact, and understanding. Notification to the family or next of kin when there has been a fatality or hospitalization because of serious accident is never easy. Sympathy is needed, but even more important is a keen appreciation for some of the simple but vital necessities, such things as grocery money, trans portation to hospital or funeral parlor, baby sitters, and even guidance in legal and insurance matters. There is a very fine line separating the private and personal life of an employee and his dependents, and the proper area or extent of a company's assistance. Much depends on the type of plant: large or small, urban or rural, new or old, and the gen eral climate of employee and labor relations. In any case, prompt action is an obligation when there is personal injury. Another impor tant assignment of the industrial relations group, unless there is a separate public relations department, is handling news representatives. Though we would perhaps prefer to say nothing about the difficulties that we create or befall us, an accident of any magnitude becomes public property the minute it occurs, and as news it is the proper province of radio, television, and the press. Under these conditions a company has only two choices: to provide reporters with as much correct information as possible within their deadline demands, or ac cept the generally less favorable publicity resulting from news stories based on hearsay. It has been the experience of most companies that if they cooperate with the news media, they will receive fair treatment. Other duties of the industrial relations action station include the issuance of passes to key personnel so that they can get through road blocks or police ETC 03562 534 Safety and Accident Prevention in Chemical Operations lines, the calling of off-duty employees for special assignment 0ht ing food or clothing changes for those who cannot be relieved general performing all those functions which pertain to the welfar persons involved in the emergency. INSURANCE DEPARTMENT The functions of the insurance manager are usually not well defined in most emergency procedures, and this is unfortunate for they have several important assignments. First, a contact man is needed f0r insurance company representatives. There will be many of these as well as men from rating bureaus and fire marshal's office who converge on the scene of a large-scale accident and their activities need carefy) coordination. Second, even though the accounting department will have an established procedure for issuing job-order numbers and col lecting loss data, the insurance manager should make certain that the method is satisfactory. Third, the claims of plant personnel and third parties will need careful handling to assure continuation of good em ployee and public relations. And fourth, in salvage work and the expediting of equipment delivery, the insurance companies can often be most helpful if their services are carefully coordinated by the in surance manager. PRODUCTION, ENGINEERING, AND MAINTENANCE DEPARTMENTS Each operating unit within a plant should have a detailed shutdown or hold-safe procedure. It should know the exact length of time it takes to discontinue safely any production unit and each of the haz ards which must be safeguarded. Equally important, there will be understanding as to the effect on all other plant units of an accident f in their own operation. Engineering and maintenance personnel will have special assignments depending upon the type and the seriousness of the emergency, but their services are an integral part of every loss control program. .L OUTSIDE AGENCIES Some of the most valuable and important action stations will be located outside the plant. If there is a mutual-aid organization, the task of developing and obtaining many needed services becomes infinitely easier. No plant is an island; it needs the support and help of many units, some public, some private, but all are useful at ETC 03563 Action Stations and Disaster Planning 535 one time or another in managing an emergency. They include as follows: (a) Fire Departments. Both municipal or those belonging to adjacent industrial plants. i (b) Police and Highway Patrol. It is essential that roads be kept : open so that help can reach a plant. (c) Industrial Plants. In addition to auxiliary fire departments, a certain amount of other vital equipment such as ambulances, cranes, and portable radios, is often available. (d) Red Cross and Salvation Army. Their services are well known, 1(e) Civil Defense. Wherever there is a CD unit that is well organized and not hampered by politics, a plant should include their faci! lities in the emergency program. ; (/) Ministerial Association. A minister, rabbi, or priest can be es pecially helpful when there is serious injury. (g) Medical. Local doctors, nurses, hospital facilities, and ambulance I service must be carefully listed in the emergency procedure and ! arrangements made for their responding on call. (h) Public Utilities. Contacts should be established with water, tele phone, and power and light companies. Each has special contri butions it can make. The telephone companies seem to have done an especially good job in developing emergency service. (i) Insurance Engineers. Their experience can be helpful in many ways. They may have been closely associated with a similar emergency and know effective control measures; they may be familiar with the location of special equipment that is needed; or they can assist in the investigation after the emergency is over. | Each emergency program must be tailor-made to fit specific needs. There could be other outside services which could be useful to a local plant, and of course the number of action stations will depend upon normal organization, personnel available, and kind of operation. In summary, seven positive steps are suggested to keep direct and in tangible losses to a minimum in case of disaster. 1. Be Pessimistic--Expect the Worst. The accident which we think i will not happen, often does. A good approach to emergency plan ning was defined by Victor Hugo over a hundred years ago when he wrote, "Nothing is more imminent than the impossible and what we must always foresee is the unforeseen." 2. Think Big. A super-sized screen is needed to view all of the lossproducing possibilities. Identify hazards or combination of hazards ETC 03564 536 Safety and Accident Prevention in Chemical Operations which could cause large losses and visualize their potential. Em ploy the techniques of "brain-storming" or "imagineering" to get out of mental ruts and narrow thought channels. 3. Develop a Plan. Determine in advance the best procedure to be followed for all abnormal conditions. 4. Assign Responsibility. Every person has a job. 5. Provide Backup. An emergency plan is like a chain, and failure at any point can compound the disaster. Someone must be in re sponsible charge at all times and be empowered to take whatever decisive action is necessary. 6. Practice Regularly. A plan may be very impressive on paper, but when an emergency occurs, there is not time enough to read the instructions. Familiarity with responsibilities and procedures must be thorough so that response can be automatic and in accordance with the over-all plan. 7. Review Procedures and Evaluate Performance. Careful evalua tion of practice drills will reveal shortcomings and inadequacies. Procedures should be frequently reviewed to reflect any changes in personnel, relocation of operations, or introduction of new processes. A plan is dependable only if it is accurate. Certainly one of the characteristics of the average American is an optimistic outlook on life, a sanguine and confident attitude, and so it is difficult to spend much time contemplating possible catastrophes. However, major disasters do occur and we are being unrealistic and imprudent if we do not consider carefully the unpleasant and costly emergency situations which might confront us tomorrow. Planning for the future is a basic responsibility of management and a matter of vital concern for all members of the management team. We may not have a knight like Don Quixote on our payroll, but we can appreciate what Cervantes had him say before charging into one of his many adventures, "Forewarned, forearmed; to be prepared is half the victory." i ETC 03565 30 Measuring Safety Effectiveness John V. Grimaldi Probably the most important factor in any organized effort is the system of measuring its effectiveness. In the absence of a credible measure, a program moves haltingly at best. Its administrator's ef forts will not be recognized satisfactorily, and neither will the degree of contribution from those who implement the program's course. When a measure that is not credible is tried, its value in motivat ing performance and signaling shifts in strength diminishes rapidly. In the final analysis, any system whose success depends on a current understanding of the vigor and direction of its components relies on measures of optimizing its effectiveness and determining the degree of recognition to be accorded its contributors.1 30.1. CRITERIA FOR EFFECTIVE MEASURES The principal requirements for an acceptable measure are that it be reliable and valid. "Reliability" requires that the values reported by the measure will be reproducible by any qualified investigator, with much the same accuracy, within reasonable limits. "Validity" means that the measure truly appraises what it purports to measure. Standard Measures In the United States the standard means for appraising safety progress is the American Standard Method of Recording and Measur- 537 etc. 03566 538 Safety and Accident Prevention in Chemical Operations ing Work Injury Experience, Z 16.1, R. 1959, published by the Amer' Standards Association. This has been the accepted approach s' D 1937 for computing and measuring work-injury experience. It refl J the opinions and practical experience of those interested in or affect^ by the application of the measure. Each interested group (such employers, employees, government, insurance companies, the National Safety Council, the American Society of Safety Engineers, and so onl named a representative and alternate to a committee, which Was balanced with respect to opposite and allied interests, according to the procedures of the American Standards Association. This workin group, representing a cross section of those interested in the standard is known as a sectional committee. From time to time the standard is reviewed by the committee, and it is either re-affirmed or revised as necessary, according to the experience of its users.2 The accepted standard measures of work-injury experience are frequency and severity. The first term refers to the frequency 0f occurrence of disabling injuries as defined by the American Standard The second term refers to the total days lost plus time charges for deaths and permanent disabilities resulting from the disabling injuries. USES OF MEASURES Detecting Changes in Effectiveness. A measure, as an indicator, facilitates taking necessary corrective action promptly. It has the equally important value of enabling the quick capitalizing on a notably successful development in the program. Appraising the Efforts of Contributors. The principal developers of a program and those who are expected to support it cannot be appro priately rewarded or disciplined for the degree of their effort without referring to performance measures. Motivating Accelerated Performance. A common application of safety measures (among other managerial measuring aids) is to employ them in a contest to stimulate employee effectiveness. Safety measures, therefore, often are used to compare the injury experience of one unit of a company with another. A difficulty occurs in such comparisons, however. Usually there are differences in exposure (one plant may have more hazardous operations or may be working under more trying circumstances) and as a consequence, the comparisons often are not equal and are criticized by the participants in the contest. Rarely do they operate on a completely' fair level. In some cases they may not take into account all injuries of similar classifications. ETC 03567 I i Measuring Safety Effectiveness 539 It will be seen in the following discussion of the American Standard that it is possible for a plant with many types of jobs and an alert, effective industrial medical center, to return to employment, without loss of time, an injured employee who has suffered no permanent disability, but who may not have been able to return to the job he had when injured. If the plant has a regularly established job to offer him, which will not aggravate his injury, it is common practice to place him in such an assignment. The standard does not count such a case if there is no lost time and no permanent injury. The large plant, then, obviously has an advantage over the smaller in being able to reduce the number of chargeable injury cases. The plant that cannot take advantage of this feature of the standard, but experiencing the same type of injury as its more fortunate associate, would have a case to report. The difference in its record would not necessarily imply that it is less effective in maintaining its safety program. There are sound employee relations reasons for encouraging injured employees to return to work as promptly as their injuries will allow. On the other hand there is criticism of this action when it affects safety-record comparisons. In such cases, the swift return of an employee through the cooperation of the medical center and employee relations officer, and, because of the opportunity to provide a suitable temporary assignment, would be considered more appropriate to injury control than safety effectiveness. Injury control is a proper element of the safety-effectiveness effort, but not necessarily deserving of being measured by the standard approach to appraising safety effectiveness. THE AMERICAN STANDARD METHOD The Z 16.1 Standard represents a sincere attempt to establish a precise basis for computing work-injury frequency and severity rates. "Work injury" is defined as "any injury suffered by a person which arises out of and in the course of his employment." ."Injury" is con sidered to include occupational disease and work-connected disability. "Occupational disease" is defined by the standard as "a disease caused by environmental factors, the exposure to which is peculiar to a particular process, trade, or occupation, and to which an employee is not ordinarily subjected or exposed outside of or away from such employment." Only disabling injuries are referred to in these rates. Sometimes they are referred to as "lost-time injuries," but the former term is more appropriate. 1 03 5fi8 540 Safety and Accident Prevention in Chemical Operations Disabling (lost-time) injuries have been grouped into four category3 of cases: 1. Fatalities. When death occurs from a work injury, it makes no difference how long after the injury the death took place for the purpose of classifying the injury. 2. Permanent Total Disabilities. These are injuries which are per. manent and likely to reduce the possibility that the w'orker can perform his job again as effectively as before he was injured. Thus the loss of or loss of use of both eyes, both hands, arms, legs, feet or any combination of these would be considered permanently disabling. As a matter of fact the use of prosthetic appliances, re habilitation programs, and the employers' increasing acceptance of disabled workers, with the help of second-injury fund laws in the states, have made it possible for people who have severe permanent injuries to return to gainful occupations. The appropriateness of this classification is questionable, therefore, but it does have sta tistical value. 3. Permanent Partial Disabilities. These injuries include the loss of or permanent impairment in the use of any part of the body unless a combination of several injuries incurred at the same time puts the case into the class described above (such as "Permanent Total Disabilities"). Some permanent injuries, apt to be suffered by a worker, are not included in this classification. For example, loss of teeth and disfigurement would not be calculated in this category. Neither would an inguinal hernia when repaired, nor loss of the tip of the finger without bone involvement be in this category. 4. Temporary Total Disabilities. This category includes all the in juries not resulting in death or permanent disability, but which render "the injured person unable to perform a regularly established job -- which is open and available to him, during the entire time interval corresponding to the hours of his regular shift on any one or more days (including Sundays, days off, or plant shutdown) subsequent to the date of injury." The decision as to whether the injured worker is able to perform a regularly established job is made by the employer's physician. A job arranged only for therapy purposes or which ordinarily is not a regularly established job in the plant is not considered to fall wuthin the requirements of the standard, when determining whether an injured but not permanently disabled worker has returned to work. It "will be apparent that most of the work-disabling injuries will fall into this temporary total-disability classification. ETC 03569 Measuring Safety Effectiveness 541 Other classifications of injuries, referred to in the American Stand ard, but not included in the calculation of the frequency and severity rates, are medical-treatment cases which may be further classified into doctor's cases and first-aid cases. The latter are those not qualifying for a doctor's attention while the former includes cases where the injuries are severe enough to be treated by a physician, but do not result in lost time or permanent disability. Some industrial safety-program directors attempt to measure their progress by using the first-aid injury totals and/or the doctor's cases. The rationale for such a measure is that the greater number of cases gives a better picture of what is taking place accident-wise in the plant. However, there are sound reasons for using only the permanently disabling or temporary disability case. First, the records for these injuries are likely to be much more accurate than those for the doctor's or first-aid cases--particularly in smaller plants. In many plants, it is difficult to say precisely how many first-aid injuries occur. For example, the workers may be lax in reporting to the dispensary, or supervision may discourage the employee from going to the dispensary, except for cases where it is obvious treatment is necessary. In some instances the dispensary may keep an incorrect record. On other occasions the dispensary may be too busy to record all the cases all of the time. And in some instances the dispensary counts every visit, including those for headache pills and cold tablets, as an indication of the extent of the services offered. Obviously this makes it much more difficult to make useful safety effectiveness com parisons from information based on dispensary records. Another complication, in the use of doctor's and first-aid cases for evaluation comparisons of various components' work-injury experience occurs, where the plant's doctor sees all cases with little regard to their significance. Thus, the first-aid case and the more distinctive doctor's case would be grouped together. The disabling-injury case, on the other hand, is more definitive, and it is almost certain to be recorded. Usually a record must be kept and filed promptly with the Workmen's Compensation Authority whenever an injury occurs which may be eligible for workmen's com pensation indemnification. (There usually is no correlation between the incidence of workmen's compensation cases and the frequency rate calculated according to the American Standard. The criteria for de termining the eligibility of an injury for workmen's compensation differ from the definitions of a disabling injury according to the American Standard.) 542 Safety and Accident Prevention in Chemical Operations Another reason for selecting the disabling-injury case as the basis for calculating frequency and severity rates is that the focus on this category eliminates the possibility that the relatively minor first-aid case may be discouraged by supervision from visiting the dispensary in order to improve the accident record. In minor cases it is very important that appropriate treatment be received promptly to reduce the possibility that an injury will become more severe. Some safety directors become so absorbed in attempting to develop an extraordinary record of accomplishment that they encourage the employment office to "create" jobs for injured workers who have no permanently disabling injury, but who would be "lost-time" cases according to the standard measure. The failure to count such cases is contrary to the intent of the American Standard, and in such cases the computed work-injury experience would not be properly represent ative of the plant's accident record as defined by the standard. The practice, although reprehensible because it improperly shades the workinjury record, is not criticizable with respect to the worker, unless, of course, he is placed in an assignment where his injury may be aggra vated or where his temporary incapacity would make him more vul nerable to another accident. Many times make-work type assignments are of genuine benefit to the injured worker's morale. Although they should be encouraged where possible it would be better if such moves were not made to favorably affect the work-injury record. "Work activity or the environment of employment" are terms used by the American Standard to identify those disabling injuries on which the standard is based. The American Standard explains that employ ment means: 1. All work or activity performed in carrying out an assignment or request of the employer including incidental and related activities not specifically covered by the assignment or request. 2. Any voluntary work or activity undertaken while on duty with the intent of benefiting the employer. 3. Any activities undertaken while on duty with the consent or ap proval of the employer. Injuries that occur in normal travel to and from work are not con sidered to "arise out of employment" unless they occur on the premises of the employer, but not in a parking lot provided by the employer unless the injured worker was carrying out duties in the parking lot for his employer at the time. On the other hand, work injuries do ETC 03571 Measuring Safety Effectiveness 543 include those that happen while traveling in the interests of the employer. When computing frequency and severity rates for the entire com pany, injuries from all departments (office, sales, as well as production) should be included along with the man-hour exposures for these operations. Also most companies compute the work-injury experience for the individual components of the company so that each unit can observe its progress. FREQUENCY RATE The frequency rate is defined as the number of disabling injuries per million man-hours worked. The formula is expressed as follows: Number of disabling injuries X 1,000,000 Frequency = Number of man-hours worked Example: A chemical plant employing an average of 200 workers during 1963 had eight disabling-injury accidents during the year. Calculating on the basis of a 40-hr week for about 50 working weeks each man put in about 2000 hr during the year. Therefore: tF-reqMuenc'v = --8 X4010,',000000'--,000 = 2o0ri Saying that a production unit has a frequency rate of 20 means that the ratio between disabling injuries and million man-hours worked is 20:1. This frequently disturbs some when they recall, as in the case of our example, that only eight disabling injuries occurred and that in fact the plant would have to work approximately 2x/o yr before 1,000,000 hr were accumulated. The 20, therefore, may appear to be unrealistic. One of the difficulties in applying the standard measure occurs be cause of its attempt to include practically all disabling-injury accident cases which arise out of and in the course of employment. Sometimes it is not clear whether the injury should be charged as a responsibility of the employer, in the light of the circumstances associated with its cause. Questionable cases may be referred to the Committee on Interpretations of the American Standards Association.3 SEVERITY RATE The severity rate is the number of days charged or lost per million man-hours worked. The lost-time charges include the total actual TC 03572 544 Safety and Accident Prevention in Chemical Operatioru TABLE 30.1. The American Standard Schedule of Time Charges Nature oj Injury Death Permanent total disability Time Charges as Number oj Days Lost 6000 6000 Fingers, Thumb,, and Hand Amputation Involving All or Part of Bone Distal phalange Middle phalange Proximal phalange Metacarpal Hand at wrist 3000 Thumb 300 600 900 Index 100 200 400 600 Fingers Middle Ring 75 60 150 120 300 240 500 450 Toe, Foot, and Ankle Amputation Involving All or Part of Bone Distal phalange Middle phalange Proximal phalange Metatarsal Foot at ankle 2400 Great Toe 150 300 600 Each oj Other Toes 35 75 150 350 Arm Any point above elbow, including shoulder joint Any point above wrist and at or below elbow 4500 3600 Leg Any point above knee Any point above ankle and at or below knee 4500 3000 Impairment of Function One eye (loss of sight), whether or not there is sight in the other eye Both eyes (loss of sight), in one accident One ear (complete industrial loss of hearing), whether or not there is hearing in the other ear Both ears (complete industrial loss of hearing), in one accident Unrepaired hernia 1800 6000 600 3000 50 50 100 200 400 -- Note: If hernia is repaired, it is not counted as a permanent disability but rather a temporary- total disability. Finger tips: Loss of a finger tip without surgical bone involvement is counted as a temporary total disability. Measuring Safety Effectiveness 545 calendar days (including holidays, weekends, and plant shutdowns) when the injured person was unable to work (temporarily totally disabled) because of his accident. However, the day of the injury and the day the injured worker returns to work are not counted in the total lost-time charges. The days-lost charges for permanent disability cases are taken from a schedule (see Table 30.1) provided in the American Standard and applicable for all deaths, permanent total, and permanent partial disability cases. In these cases the actual time lost from work when the accident results in death or permanent disability is not "ounted. The standard time charges alone are applied. They are considered sufficiently penalizing so that additional time charges are not appro priate. The time charge for a death is arbitrarily set at 6000 days. This is the estimated -working life for the average worker. Injuries involving more than one part of the body are calculated from Table 30.1, so as to total the charges for each part except that the total may never exceed 6000 days. When a part of the body is per manently disabled the charge that is greatest for that part in Table 30.1 is used in the calculation, not that charge plus the smaller charges for the other lesser sections of the part lost (disabled). Where a person suffers a temporary total disability and a permanent partial disability in the accident the higher of the two injury charges is used. When an injury results in partial, rather than complete, loss of use of a part of the body the percent loss of use is determined by the employer's physician. The time charge applied in such cases is equivalent to the percent of the loss of use of the member multiplied by the scheduled time charge for the complete loss of use of the member. Example: A 20% loss of use of the thumb at the proximal joint would be charged as 20% of 600 or 120 days. The severity formula is: Severity = standard time charges for deaths and permanent disabilities, plus actual days lost for temporary total disabilities, for all of the injuries that have occurred during the period covered by the rate, divided by the number of millions of man-hours worked. This is more succinctly stated as: ,, . _ Total days lost and charged X 1,000,000 y Number of man-hours worked ETC 03574 546 Safety and Accident Prevention in Chemical Operations Example: The chemical plant in the example used for calculating the frequency rate had the following lost-time and permanent disability injury cases during 1963: Cases 3 Temporary total disabilities: Three cases resulting in a total of 18 days lost Permanent partial disabilities: One thumb--10% loss of use at metacarpal joint One eye--50% loss of sight One index finger--amputated at middle phalange (joint) One toe--amputated at distal joint Permanent total disabilities: Hand and foot amputation 8 18 days lost 18 days lost 90 days charged 900 days charged 200 days charged 35 days charged 6000 days charged 7225 days charged The total time lost and charged for the eight cases in the example is: 7243 1 days. Therefore: cSeven..ty = 7--,-2-4--3-- 'x 1,000,-0-0--0- = 1l8o,1i0n7_ da, ys lo, st . and , ch.arged ' 400,000 per miUion hours The frequency and severity rates calculated in the example are atypical for the chemical industry. In actual practice work-injury rates for chemical plants customarily are much lower than the na tional industrial average. (See page 7.) Significance of the Standard Rates Most safety specialists believe that of the two standard rates, fre quency and severity, the frequency rate is the better measure of safety performance. This point of view is conditioned in part by the safety program's objective which simply is to eliminate accidents. Certainly when no accidents have occurred the frequency and severity rates are zero, and severity as a measure would have no significance. Although many plants successfully reach the objective, as a practical matter sustained long-term zero work-injury experiences are not likely. There always is the possibility that a momentary lapse will cause an accidental disabling injury, and the perfect zero (frequency = 0) will be interrupted. Then the severity rate assumes importance since it indicates the degree to which effective hazard controls were main tained. Inasmuch as it must be recognized that accidents may hap pen occasionally a second objective must be to control hazards to a i i ETC 03575 Measuring Safety' Effectiveness 547 degree where severe consequences are not apt to follow an accidental occurrence. The severity rate is a measure of meeting this objective when an accident occurs. When the number of man-hours worked is small (for example only i a few hundred thousand hours) every disabling injury case will cause the plant's frequency rate to rise markedly. In smaller plants, theres fore, the work-injury frequency rate may vary widely from year to year and often because relatively mild accidents have taken place. The frequency rate alone does not give a good indication of the degree to which the plant's hazards are being controlled so as to limit the possibility of any accidents having severe results. The severity rate, therefore, is an important complement of the frequency rate in the standard measure although it does not receive such recog nition from many practicing safety specialists. The reason for its disfavor is that often an accident's severity is due largely to chance. ' For example, the difference between whether a worker mashes a toe, ; crushes an instep, or misses his foot entirely, when he accidentally drops a heavy section of pipe, is only a matter of inches. ] It must be remembered, however, that the frequency rate also is i subject to chance. Whether an employee is involved in an accident I that results in no injury, a minor injury, or a severe disabling injury that would be included in the frequency rate, may be just a matter of proximity at the moment. Perhaps the principal objection that ; safety specialists have to the severity rate is that it swings widely, largely because of the penalty charges imposed when a permanent dis ability occurs. Thus, it becomes difficult for the safety director to iden tify a generally smooth performance trend and appraise the progress of his efforts. Nevertheless, the severity rate, as a weighted frequency rate, has value in its capacity to reflect the plant's success in control ling its severest hazards. In general it should be recognized that both the frequency and severity rates are important for appraising safety performance. Cer tainly a plant with a low frequency but high severity rate would mislead itself if it ignored its severity experience and recorded only its seemingly favorable frequency. In the final analysis it must be remembered that while the practicing safety specialist's long-term objective is to eliminate hazards to the point where accidents no longer will happen, his short range goal must be the identification and control of those hazards which can cause severe loss to the plant and injury to employees. Progress toward both aims deserves continuous appraisal with the best measures available. ETC 03576 i 548 Safety and Accident Prevention in Chemical Operations AVERAGE SEVERITY There is a valuable interrelationship between the frequency and severity rates which often is overlooked. When the severity rate is divided by the frequency, a ratio, the average days lost per disabling injury, results. This in itself often is a useful measurement statistic It indicates the average severity of the disabling-injury accidents which have occurred during the period being measured. When the average severity, frequency rate, and severity rate are compared as trends over a number of years, for example 10 yr, a threedimensional type of measure becomes available. It is sometimes assumed that a reduction in the frequency of disa bling injury occurrence is followed automatically by a proportional improvement in the severity rate. Rarely is this so, however, for a number of reasons. Often the safety program concentrates on improv ing the frequency rate without applying sufficient emphasis on the steps to take to control the severest exposure. W'hile the latter may not cause accidents frequently (probably because their implicit danger stimulates a greater safety awareness automatically), the time charges when an accident does occur are great enough to cause the severity rate to increase significantly. If, on the other hand, a safety program is successful in eliminating or controlling the plant's severe hazards, the severity rate will improve sharply, if it has been high, and will re main at a low figure once the controls are effective. The average severity trend tends to relate the relative effectiveness in controlling both the frequency of occurrence and severity of results in a plant's disabling-injury pattern. Figure 30.1 is a "three-dimensional" comparison of the 10-yr fre quency, severity, and average severity trends for one company. It will be noticed that both the frequency and severity rates were im proving notably, but the average severity trend rose sharply. If the safety program had been uniformly successful in its efforts to reduce the number of disabling injury accidents, the severity rate would have improved proportionately, and the frequency and the average severity trend line would have been flat. A few years later the results of the same company's effective drive on the control of severe accidents is indicated in the pattern in Fig. 30.2. When using this three-dimen sional application of the standard measures, it is important to remem ber that it should be applied in conjunction with the established safety program goals: elimination of accident-producing hazards (frequency ETC 03577 Measuring Safety Effectiveness 549 1947 1949 1951 1953 1955 FIG. 30.1. Disabling injuries ten-year trends. 1957 rate reducing to zero) and control of severe hazards to diminish the consequences of any accident that may occur (severity rate reducing to the level of the frequency rate). Auxiliary Measures of Safety Effectiveness The foregoing discussions will have indicated that the frequency and severity rates cannot assay fully the quality of a plant's safety ETC 03578 550 Safety and Accident Prevention in Chemical Operation* effort. In the first place a zero frequency rate does not necessar i imply that all is being done perfectly with respect to safety. On *h other hand, a high frequency rate does not necessarily mean that 6 extraordinarily poor safety program exists. In the latter case th* type of industry and the operations it employs may limit for h.6 moment the opportunity to develop safety successes common to oth * more easily controlled businesses. Other methods, therefore, must be r ETC 03579 Measuring Safety Effectiveness 551 used to determine whether a satisfactory effort is being exerted to achieve safety effectiveness.4 AUDITS One means of appraising the quality of the plant safety effort is to employ an in-depth examination of the facilities and the attitude, plans, and work of those responsible for the plant. The audit probes the hazard-control effort of the operation and usually is conducted in behalf of the plant's principal manager. A carefully drawn report of the auditor's observation provides an authoritative basis for decid ing whether a plant truly deserves the frequency rate it reports. COMPARISONS Another means for evaluating the quality of a plant's safety ex perience is to compare its experience to that of the industry it rep resents. It is well known that some industries, because of the inherent hazards in their operations, will consistently have higher frequency or severity rates than some others. The question then is whether the plant is doing better than its counterparts and over how long a span has it been improving or sliding. Other Measures Safety specialists have been searching vigorously for more descrip tive and reliable methods for appraising safety effectiveness. The frequency and severity rates are bitterly condemned, at one time or another, by most safety specialists. However, the efforts of those who have experimented with other measuring methods have not be come popular as yet. Among the measuring procedures which have been recommended or described by others are: 1. The Modern Standard Method.` Several years ago Simonds de scribed a realistic method for relating a plant's accident experience to its costs. The research was conducted under a grant from the i National Safety Council specifically to develop a simplified means for expressing the insurance cost plus the other expenses for the disabling-injury cases, doctor's cases, first-aid cases, and no-injury accidents. This method of computing the plant's accident ex perience has the advantage of being able to report a figure in dollars --a term that is readily recognizable. Frequency and severity, on ETC 03580 552 Safety and Accident Prevention in Chemical Operations the other hand, may be unintelligible to some. The "modern standard method" intends to overcome that difficulty by expressing itself in terms of the total accident cost experience, rather than only disabling injuries. 2. Work Sampling Methods. One means for determining the safety effectiveness of an operation is to sample the plant's work techniques periodically. This practice is becoming a common industrial engineering approach for identifying characteristics in an opera tion. With respect to safety, for example, a random sampling of unsafe practices and conditions could be obtained by looking for such deviations every 15 min for a brief period (5 min) through several hours of a shift at critical locations. The observations noted would be reported in an analysis that appraises the noted quality of the plant's safety effort. Appropriate recommendations usually conclude the report. 3. Disabling Injury Index.2 Although not a part of the American Standard this measure is included in its appendix as an aid to com bining the frequency and severity experience. The measure is: disabling injury frequency rate X Disabling injury index = disabling injury severity rate 1000 This is used primarily for ranking one plant or component against another. If it is to be used to indicate degree of improvement or to compare the degree of difference between plants, the square root of the index must be taken to make a mathematically correct comparison. 4. Contingency Cost Measures,3 This approach relies on a relation ship between costs that are a function of managerial performance and the plant's measured effectiveness in controlling severe hazards. The relationship was identified first in an intensive operations re search study, and a measure was then constructed. Subsequent studies indicate that the measure should be tailored specifically for each type of industry to obtain the most accurate results. Variations occur in the measured "management variables" (direct labor costs, rework costs, scrap, building maintenance, equipment maintenance, complaint costs, shop costs, and net sales billed) prob ably because of business factors which are distinctive to the partic ular industry. However, there is good evidence that the measure generally appraises management's effectiveness in maintaining tight control of its operations, and that the degree of control is related to the plant's ability to control its severe hazards as meas- ------------------------------------------------------------------------------------------- Measuring Safety Effectiveness 553 ured by the severity rate. The contingency cost measure in fact appears to have a capacity for forecasting the occurrence of severe accidents by approximately 9 months after the measure shows an established trend of diminishing managerial control. While it is tempting to use cost figures to express degrees of prog ress in controlling a plant's work-injury experience, some caution is advised when applying such measures. Certainly costs are effective attention getters, and they are becoming increasingly important to the businessman as he struggles to survive in the market place. How ever, in many companies the accident experience has been improved to such a degree that its total cost appears almost insignificant compared I to the other major sources of operating expense. It is difficult to make I a strong case for accident costs, specifically in such an instance, al] though the management certainly is aware that without its safety j programs its costs would be higher. { An overstressing of accident costs may in fact distract from the principal objectives of the safety program, namely, to eliminate or control hazards so that accidents are prevented or will not have severe consequences. Using accidental injuries and costs together as ele ments of the information-gathering process related to unsafe acts and conditions, and the significance of their influence on the plant's ability to reach its business objectives, would appear to be a most effective means of reporting safety progress. Measures of safety effectiveness, like any measure, are of value only when they assist administrators to make correct decisions on how to proceed in meeting their responsibilities. The application of the American Standard measure of work-injury experience or any of the experimental indicators of safety effectiveness should be tempered with the knowledge that their principal service is their ability to in dicate where weaknesses exist that must be buttressed and where strengths appear that may contain some special knowledge which will assist in moving the total effort forward another giant step. REFERENCES 1. R. H. Simonds and J. V. Grimaldi, Safely Management, Second Edition, Richard D. Irwin and Co., Homewood, 111.. 1963. 2. Z 16.1-1954, R. 1959, "ASA Method of Recording and Measuring Work Injury Experience,'1 American Standards Assoc., New York. 8. Committee on Intepretations of the American Standards Association, 10 East 40th St., New York, New York. 4. J. V. Grimaldi, "Appraising Safety Effectiveness," Jour. Am. Soc. of Safely'Eng. (November 1960), pp. 57-62. ETC 03582 The Future of Chemical Safety Arthur H, Christian With the future of chemistry itself almost beyond prediction, how can we predict what the future, even the next decade, will bring to chemical safety? We cannot exactly, but we can try to foretell reason ably the temper of the times ahead. Possibly many of our reflective predictions will not come to pass within the next decade or even the next century. Without question, however, it will be the era of the activist, and it is bound to be full of challenging change for all, par ticularly those working at chemical safety. Everything seems to be growing exponentially: total population and new nations; new chemicals and different names for them; new problems and different variations of old problems. Most important, the pyramid of knowledge is growing exponentially --truly exhibiting a "snowball" effect. With chemistry and chemicals involved with so very many of the "things" and the "action,'' who can doubt that chemical safety problems will increase proportionately --in numbers, in degrees, in uniqueness, in cost, both to solve and as a penalty for failure to solve, and in difficulty to detect and safeguard. Some claim there are many existing chemical safety problems of the so-called "unsolvable type." This had better not be true if progress is to continue at the predicted rate. Moreover new techniques and new approaches will have to be found for curing some of our chemicalsafety headaches, for undoubtedly soon there will be many tougher ones to solve than hardly could be conjured up in our wildest night mares. It would be most pessimistic and quite unrealistic to think for a moment that awesome new fields will not be discovered with j | 554 ETC 03583 The Future of Chemical Safety 555 unique hazards not imagined now. These will necessitate unorthodox approaches for safety, just as the field of atomic energy did. All of the accident-prevention problems must be solved in a practical fashion for us to remain competitive as individuals, as companies, as industries, and, yes, even as nations and possibly even as a planet. Many new fields with unimaginable accident-prevention problems may be opened up by the obvious expendiency of solving more of nature's age-old riddles. Everyone admits that mother nature really has something--for example, an aeronautical engineer knows that theoretically a bumblebee cannot possibly fly, yet the bee takes off anyway. Imagine the chemical process industry that might evolve when all the chemical mysteries of the human body alone are completely eluci dated--for example the exact mechanisms of seeing and hearing,' so that light energy and sound energy, through transmutation, could be converted into another more desirable product. Moreover, very com plex chemical procedures could be vastly simplified if they could be accomplished in the wonderfully direct manner of life processes. Undoubtedly, too, the space age will result in chemical-producing plants on space platforms or on far planets. This may result in trans portation back to earth of newly discovered elements or chemicals with absolutely unexpected hazards, but with end use of such value as to merit solution of any chemical-accident prevention problems. Both the "big-science" effort to get man routinely away from earth and the new knowledge found "out there" should yield totally new disciplines in chemistry or involving chemistry. It would seem to be anyone's guess as to what they might be. For example, chemistry on our planet generally is water-oriented for quite obvious reasons. Imagine the personal-protection problems, to say nothing of the tech nical problems to be solved, if chemistry on a newly settled planet logically should be ammonia-oriented for equally obvious reasons. What of hazards? There probably will be more acute versions of those presently known. Consider chemical processes--not merely for the foreseeable future but long range. There will be a plenitude of extremes. As a logical avenue of refinement and as a part of evolutionary development, research activities and production will in volve more extreme conditions: both higher and lower temperatures; greater vacuums and higher pressures; greater reactivity in all mediums; more insidious toxicity with more unexpected chronic and acute physiological manifestations as a result of unexpected adverse synergistic effects; larger and smaller scale reactions; routes for'molec ular rearrangement not now known. ETC 03584 556 Safety and Accident Prevention in Chemical Operations Fundamentally, however, much of chemical accident prevention will remain the same. Any chemical can be handled safely provided full knowledge of all hazards is deliberately obtained and wisely used. Every chemical reaction should be researched in breadth and depth for safety parameters equally as thoroughly as usually is done to maximize quality, productivity, cost, and other production, sale, and use factors. This will be an urgent necessity for the more advanced, complicated, and unknown reactions, and it is most advisable for older processes. In recent years a number of chemical plant disasters have resulted from unexpected phenomena where a certain set of conditions or se quence of events occurred for the first time, even though the process had been in use successfully and safely for many years. Engineering studies should include evaluation of stability and hazardous char acteristics of reactants, the reaction mechanism itself, and the' nature of intermediates. Other factors that should be studied include effects of error in the quantity or order of adding chemicals; problems arising from loss of cooling water, interruption of agitation, and malfunction of instrumentation. These may be coupled with excessive heat, pres sure, and holding time. Although actual laboratory or field investigations are invaluable in establishing widely expanded and detailed parameters for safe opera tion, the whole endeavor of necessity will be greatly simplified. Through use of a vastly improved compilation of data from fundamental re search and record keeping, together with more high-speed and thorough methods of data retrieval and association, much more com plete overall safety evaluations will be possible. With the growth in numbers of chemicals, the necessity for improved data systems be comes increasingly important, both economically and from a safety viewpoint. New materials of construction, more knowledgeable and creative engineering design, and new operating techniques will eliminate many of the present-day chemical safety headaches. For example, contact between people and chemical processes, even maintenance people, largely will be eliminated, as the equipment will be fail-safe, check itself out, and even automatically replace faulty miniaturized and unitized components. As new materials for fabrication of equipment are discovered, de vised, or formulated, many difficult problems will be solved. Cor rosion will be eliminated. Standardization of reactor size and type will permit molded systems of complex piping so that an entire sys tem can be replaced by remote control. Reactors themselves will 3? `3 ETC 03585 The Future of Chemical Safety 557 play the role of catalyst. In similar fashion walls and other build ing parts will serve to filter and react any chemical contamination, converting it to a harmless or acceptable compound. We will come ever closer to perfection in many thought-provoking areas--the uni versal solvent with no toxicity, flammability, or other undesirable side effects; the perfect inert material for construction of everything from buildings and process equipment to packages and consumer products; recovery systems to reprocess practically everything as so-called raw materials will become more scarce and will be re-used more and more. The problem of the aging and marginal chemical-producing or con suming plant will not be solved easily. AYhile many of these no doubt will be in good use for many decades to come, again, to be competitive, they must be ever alert to improve their accident-preven tion features, techniques, and safeguards. As for replacement, the population explosion probably will help in that urban redevelopment will overtake it. With the continued growth and evolutionary maturing of chemical industry, the necessary location of both expansion phases and sophisti cated new fields must be carefully considered. Air and water pollution alone will be tough problems to solve, as we know now. Add to this exposure hazards of types not yet encountered, such as sound, light, or other phenomena emotionally or physiologically harmful, and it would seem indicated that one logical course might be for these plants to be completely segregated from normal living areas using common services. This would be essentially a further refinement of the "industrial parks." Again, to be competitive and to control gross hazards, it may be necessary to use vast and complex disposal plants, with entire manufacturing areas "atmosphere conditioned" to preclude release of harmful materials. One advantage might be sharing maintenance and other service personnel. Revolutionary new approaches might also be indicated, such as locating plants deep underground where they would be more immune to enemy assault, closer to raw materials, and utilize energy from deep within our earth. Other plants might be located deep under the ocean or at least as an artificial island--again close to raw material, using solar or sea energy --remotely controlled and practically uninhabited. Automation and computer control will team up to cause awesome changes in technology and operations. Not only will major strides continue in the present areas of controlling chemical processes by automatically measuring and correcting variables from predetermined ETC 03586 558 Safety and Accident Prevention in Chemical Operations "programs," but other refinements will benefit accident prevention For example, by combining all applicable "instant literature" and knowledge from vast research, these machines will greatly outperform humans in sensing or predicting when an accident, such as an explo sion, is about to take place, and avert it. This technique even will be brought to bear in prevention of "garden variety" injuries such as cut fingers. Transportation of chemicals will become an increasingly significant safety consideration. Most trends obviously will not make problems simpler: volume increases; hazards and variety become greater; traffic will be more congested on highways; residential areas and onlookers much more prevalent to complicate matters in case there is trouble; consumers will be more widespread. While there may be no revolutionary new modes of transporting chemicals, there unquestionably will be impressive evolutionary refine ments. Emphasis will be on efficiency and savings--dehydration where possible, standardized sizes and unit packs, automated handling --in fact, separation of chemicals from humans both for handling and during transit. Use of pipelines, with greater variety of chemicals through the same system, solids as well as liquids and gases will in crease. So will barges, ships, and underwater plastic tanks. Auto mated high-speed trains or driverless vehicles on special commercial superways or tunnels will further isolate chemical freight problems from the population. Possibly our advances in accident prevention generally have ac tually lulled far too many of us into a false sense of security. In spite of headline accidents every now and then, who hesitates nowadays to step into a high-speed elevator, climb aboard a jet airliner, take a pill, or use a new oven cleaner? Few indeed! The use of chemicals will be increasingly wider, and thus exposure will be greater. The education of vastly larger numbers of consumers in the safe use of many new chemicals is going to be a challenging problem in itself. It will not be restricted to large and small chemical industries themselves, but essentially will cut across all human ac tivities. Chemicals in toy or educational chemistry sets will become more hazardous as will laboratory courses at school. Do-it-yourself kits and materials available for home use will become similarly more sophisticated with severe potential hazards. Certainly the manufac turing chemical industry has both a responsibility and a vested in terest to insure that the safest products possible are formulated and marketed, and that the consuming public is well educated in safe ETC 03587 The Future of Chemical Safety 559 practices and precautions. Hopefully such education will start early in school life. Legislation to prevent marketing of possibly hazardous chemicals, or to require full labeling to show contents, hazards, and precautions may be steps in the right direction but cannot be the full answer. In fact, legislative fiat may not contribute to improved safety--only to confused mediocrity. Disposal of waste is a problem that seems to increase in direct proportion to the advance of civilzation. Regarding chemicals, the rate may be more acute, both for manufacturer and consumer. As quantities increase, hazards become more complex, legislation becomes ie, tighter on methods and exposure allowed, and as costs go higher, disposal will become a greater factor. Certainly existing processes ng well may have to be modified and initial research efforts on new te- products or processes will have to carefully appraise impact of dis on posal problems. ng With all this, though, what may be some of the avenues to safe ng and practical disposal? Conversion to useful products, however elabo 's rate may be the route, may be the most attractive goal. Others may include orbiting, but we shudder at contemplating space becoming a dumping ground. Rapid advances in hazard control will be a must. New approaches, solid achievements in furthering fundamentals, and diligent applica tion of specifics--all adding up to hard, hard work at controlling chemical hazards--will be necessary to allow continued great achieve ments and advancement in the chemical industry. Many rewards will come from interdisciplinary research in the form of startling refine ments of existing knowledge and practices. More important, wre should anticipate amazing breakthroughs in accident prevention, and these well may come from completely outside the field that will benefit the most. For example, Madame Curie was not a physician, 3 but her discovery of radium benefited the practice of medicine pro 1 foundly. Hopefully chemical safety will be made easier and more positive from such blessings. Much progress no doubt wall ensue simply from application and f refinement of currently recognized fundamentals. Competition among equipment manufacturers will be so keen that key among designers will be safety engineers. Possibility of product liability must be eliminated on the drawing board. Safety features will be prime sales lures. Mechanical guards and intricate electronic interlocks to avoid any exposure to physical injury wall be automatically part of minimum ETc 03588 560 Safety and Accident Prevention in Chemical Operations or stripped models! Electrical shock will be a thing of the past, be cause of self-contained power sources. Falls will be unheard of. Each industrial worker will wear a tiny gyro stabilizer, controlling him nicely in preset planes. Scaffolding will be unnecessary, as workmen will simply use a by-then perfected degravitizer belt. Even hand injuries will be an almost unremembered misadventure In addition to greater inherent safety in "things" being handled, such as truly unbreakable bench-scale "glassware" equipment, the ulti mate in hand-protection gear will be available. Through chemistry indestructible, impenetrable, comfortable, and practical gloves will be commonplace. Highly developed complex continuous monitoring devices will safeguard the entire working environment to protect people, property process, and material absolutely against all potentially harmful chemicals or hazards, either in the process or in maintenance material. A speedy analysis on the spot of the total work area automatically will be fed into a computer for proper readout and corrective action. No longer can the process be safe, and a disaster wander in with re pair kits. Positive control will have arrived. Regardless of the wondrous advances in the field of chemistry and in other related fields of endeavor, all will have one common denominator--people. Only people can make things happen, and, of course, most regrettable things happen to people. While much de tailed effort invested in preventing a chemically involved disaster probably will yield as in the past very gratifying results, efforts to control or change people and their action probably will be slow, frus trating, and disappointing. Mores will change for the better very slowly. It is extremely unlikely that a strain of workers might be bred that would have greater resistance to effects of toxic chemicals or be more accident proof. The so-called "personal factor" will continue to be a significant part of the cause of chemical accidents and loss, and a target worthy of much effort to control. Hopefully, chemicals and other advanced techniques may open completely new fields to help people conquer safety problems as they have helped to cure mental illness. If electric shock and drugs can help eliminate or re-orient undesirable mental patterns, why cannot a safety vaccine be developed? Why cannot newT employees receive the maximum in safety orientation and job training by the simple ex pedient of receiving a shot during the employment physical, followed by several sessions of wearing an electronic headpiece? An electronic headpiece well might serve a useful purpose also to program a person's activities during an entire working shift, probably shortened to a few I j 1 ' i ; > kTC 03589 1 The Future of Chemical Safety 561 hours. Precise actions to be followed would already have been pro grammed taking into consideration his abilities and limitations, both physical and mental. These then would be somewhat like oldtime horse blinders. They would be a space-age version that would eliminate the personal factor in accidents by eliminating extraneous thoughts during the work period, and would keep the worker's atten i tion fully concentrated on doing the job in exactly the safest and best manner. Undoubtedly such a procedure will get stout resistance from many defenders of individual rights, as they will be appalled at the thought of such regimentation, and tinkering with the mind and its wondrous body. Few will stop to contemplate that this really would be only a question of degree--tinkering of this sort has been going on for ages, but not in such specifically tailored fashion. In such an advanced age of enlightenment, safety education will be included truly at the "grass roots," beginning in very early school years. By the time the highly trained chemically oriented specialist i is graduated, he will be highly proficient in the knowledge and practice of chemical safety. This single advance alone should go far to im prove safety practices in the profession--from research through pro duction to ultimate consumption and disposal. In spite of all the probable progress in prevention, it would be un realistic to postulate that every activity always would be under positive control, and the possibility of an unexpected event out of the question. Protection of people as a secondary line of defense still will be most prudent but vastly more sophisticated. First, through great strides in medical science, pre-employment physicals will be a great deal more revealing, both as to exact status of applicant's health, in addi tion to his possible susceptibility to future occupational exposures. Much of this knowledge will come from actual complex analysis and diagnosis by instruments of the future, but with the final decisions by people. When workers are exposed to possibly harmful chemicals, personal protection by complete encapsulation will be commonplace. Cost of work injuries may have risen to prohibitive levels, and as much from defense to stay competitive as from interest in the workers' welfare, chemical companies will maintain completely integrated safety programs. Personnel will be monitored continuously on the job for certain factors, and quite thoroughly at the end of the work period. Various bodily functions of each worker, depending on ex posure, will be followed by advanced techniques--pulse, respiration, ETC 03590 562 Safely and Accident Prevention in Chemical Operation* temperature, and possibly as yet undiscovered "indicators." Physj logical response would conclusively prove whether or not an in;, occurred on the job; if so, when, and to what degree. The rapid bat thorough complete physicals at end of shift could show if any expoSUre with possible delayed response had occurred. Happily, if in spite of all this accident-prevention effort a serious injury does happen, severity will be greatly lessened by heroic medical measures. Complete rehabilitation and replacement of body organs and limbs will be commonplace, and chemical science will have made remarkable contributions to these advances in successful technique. 1i i ETC 03591 1 Appendix I Sources of Information on Chemical Safety 1. Agricultural Ammonia Institute, 703 DuPont Building, 22 South Second St., Memphis, Tenn. 38103 (telephone 901-5250811), is the edu cational trade association for the anhydrous ammonia industry. Zenas H. Beers is executive vice-president. 2. Air Pollution Control Association, 4400 Fifth Ave., Pittsburgh 13, Pa. (telephone MAyflower 1-1100), is a nonprofit membership or ganization composed of industries with air pollution problems; manu facturers of air pollution-abatement equipment; control officials, and research, education, and consulting personnel. The Association's Tech nical Council works toward international adoption of reasonable engi neering performance standards. APCA through its Council seeks to establish definitions, methods, procedures, and recommended practical limits of air-pollution emission for the guidance of the membership and others who are interested. The association publishes bimonthly the Journal of Air Pollution Control Association and a monthly Abstract. It is the only technical association which has as its only objective the control of atmospheric pollution. 3. Air Traffic Conference of America is a division of the Air Trans port Association of America, 1000 Connecticut Ave., N.W., Washing ton 6, D. C. (telephone 296-5800). This group obtains information on chemicals and other items which may be offered for transport by air or carried on commercial airlines, and issues bulletins outlining the proper handling or prohibiting their transport. These bulletins are sent to subscribers of tariff 6-C. In view of the current interest in the role of cargo or baggage in air safety, restrictions and rules of this group are observed by commercial airlines. H. G. Gatlin, operations division of operation and engineering dept., handles technical problems. 4. American Association of Industrial Nurses, 170 East 61st St., New 1 York 21, N. Y. (telephone TE 8-7625), is the professional organization i of the industrial nursing specialty. Members are professional nurses employed by industrial, commercial, and business concerns in the United States and Canada. The monthly publication, American Asso ciation of Industrial Nurses Journal, contains frequent articles in the field of industrial health. Mrs. Helen C.- Rush, R.N. is executive director. 5. American Chemical Society, 1155 Sixteenth St., AVashington, D. C. (telephone RE 7-3337), is the professional society representing most 563 ETC 03592 564 Safety and Accident Prevention in Chemical Operations chemists in the United States. Through the Committee on Chemical Safety, organized in 1963, the A. C. S. is engaged on a broad effort to increase safety awareness at all levels, from high school chemistry through industrial research. Chairman of the Committee is Dr. H K Livingston, Professor of Chemistry, Wayne State University, Detroit Michigan; staff contact is Mr. David Roethel at the A.C.S. Wash-! ington headquarters. 6. American Conference of Governmental Industrial Hygienists 1014 Broadway, Cincinnati 2, Ohio (telephone DU 1-2200, ext. 2654)' is concerned with coordination of standards for safe use of chemicals insofar as governmental control is possible. Most widely known an nual activity of this group is preparation of a revised threshold limit value for several hundred different gases, vapors, dusts, fumes, and mists. These values are based on experience or information which attempts to estimate the concentration level at which it is believed injury will not occur during normal work exposures. Further informa tion about the listing and other work and publications of this group should be referred to Mr. A. Hosey, secretary. 7. American Industrial Hygiene Association, 14125 Prevost, Detroit, Michigan 48227 (telephone VE 6-0058), is concerned with the practice and science of industrial hygiene. Publications of the Association include the Journal of the A.I.H.A., Hygienic Guides for over 100 chemicals and other substances, and manuals on air pollution, indus trial noise, and respiratory protective devices. In preparation are manuals on engineering and on analytical guides. George D. Clayton is executive secretary. 8. American Institute of Chemical Engineers, 345 East 47th St., New York 17, New York (telephone PL 2-68001, has two groups con cerned with safety. The program committee has a safety subgroup, which considers air and ammonia, refining and natural gas, and chem ical safety. Six manuals on safety in air and ammonia plants are in print. Two surveys on safety in air and ammonia plants are avail able. The chairman of the safety subgroup is W. L. Bulklev, American Oil Co., P. O. Box 431, Whiting, Indiana. The Equipment Committee of the A.I.Ch.E. formulates and pro mulgates recommended procedures for the testing of chemical engi neering equipment. Stafford L. Ruhlen, E. I. DuPont de Nemours & Co., Inc., Beaumont, Texas, is chairman of the equipment testing committee. Ten equipment testing procedures manuals are available. The Institute also publishes frequent articles on safety in its sev eral publications, and it arranges safety' symposia in design and opera tions at national meetings. gjj ap ; ETC 03593  Appendix 1 565 9. American Medical Association, Department of Occupational Health, 535 N. Dearborn St., Chicago, Illinois (telephone 5271500) serves primarily member physicians. It does not act as an informa tion center for inquiries by laymen. One of the A.M.A. specialty journals is the AM.A. Archives of Environmental Health. This monthly publication contains numerous articles on health, safety, and toxicology of chemicals, as well as on other factors in industrial hygiene control. Subscriptions are avail able from the American Medical Association. J. T. Siedlecki is assistant director. 10. American Nurses' Association, 10 Columbus Circle, New York 19, New York (telephone JU 2-7230) is the national professional or ganization of registered nurses. Mrs. Judith G. Whitaker, R.N., is executive director of the association. Chemical Safety is the concern of the occupational health nurses section. Miss J. A. Cipolla, R.N., is the association director for this section. Objectives for the section include: improving nursing prac tice on the part of the practitioner, continuing the education of the occupational health nurse, and safeguarding the economic security of section members. The focus of occupational health nursing programs is going beyond the emergency care concept to placing more emphasis on the prevention of disease and promotion of health. 11. American Petroleum Institute, 1271 Avenue of the Americas, New York 20, New York (telephone JUdson 6-4200), is concerned with technical aspects of the petroleum and related industries. Vari ous committees develop information and reports for sale at a nominal price on chemicals and other substances derived from or related to I petroleum. Many of the petroleum practices and procedures apply in large measure to chemical operations, such as storage tanks, piping, cleaning of tanks, and tank cars, static prevention, fire protection, industrial hygiene practices, air pollution, and waste disposal. A booklet entitled List of Publications and Materials, American Petroleum Institute is available from publications section of the A.P.I. J. F. McKenna is safety coordinator. 12. American Society of Mechanical Engineers, 345 East 47th St., New York (telephone PL 2-6800), is a technical society with phases which reach into chemical safety, such as corrosion, pressure vessels, pressure piping, and related subjects. The Committee on Air Pollu tion Controls of the A.S.M.E. publishes a semi-monthly newsletter titled `'Smog News," a clipping service for articles in the public press on air pollution and related topics, and is available for $6 per year (24 issues). Technical papers on air pollution and other subjects are ETC 03594 566 Safety and Accident Prevention in Chemical Operations published as part of the Transactions of the A.S.M.E. Seriei Journal of Engineering for Power. 13. American Standards Association, Inc., 10 East 40th St v York 16, New York (telephone MU 3-3058), is the United States^*' ber of the International Organization for Standardization. Thes mem. i of information on toxic dusts and gases, classed as Z37, is from technical committee charged with responsibility for developing stand* ards. These standards are sold at a nominal cost and include several on exposures to chemicals. A list of available American Safety Stand ards will be furnished on request. Henry G. Lamb is safety engines for the A.S.A. r 14. Association of Casualty and Surety Companies, Accident Pre vention Department, 110 William St., New York 38, New York (telephone BE 3-0700), obtains information on accident prevention from varied sources and makes it available to casualty insurance com ` panies which constitute its membership. Chemical information i8 published in a Chemical Hazards Information Series, which has been indexed covering 1949-1959, in March 1960. Another group of reports which includes some chemicals is the Special Hazard Bulletin series an index for which covering 1948-1959 has also been issued under March 1960 date. Copies of reports may be obtained from a member company or agent. James C. Roumas is director of technical research. 15. Bureau of Explosives, Association of American Railroads, 63 Vesey St., New York, New York (telephone CO 7-6788) formulates shipping regulations for dangerous substances. Mr. T. C. George, agent, published in the fall of 1963 I.C.C. Regulations No. 15 on the transpor tation of explosives and other dangerous articles. The U. S. Coast Guard Regulations are published as I.C.C. No. 16. ' B. E. Pamphlet No. 7 contains general information relating to explosives and other dan gerous articles. Annual reports are published covering the various ac tivities of the Bureau, and include a compilation of reported accidents that have occurred in transportation in which explosives or other dangerous articles were involved, the most recent of which is B. E. Report No. 57 for 1963. For further information and prices on pub lications, contact the Bureau. Mrs. N. Kelly is supervisor of tariffs and publications. 16. Chemical Specialties Manufacturers Association, Inc., 50 East 41st St., New York, New York (telephone MU 5-8722), is a trade association composed of 500 companies whose members manufacture and distribute chemical products for household and industry. The Association acts as a clearing house for scientific developments in the ETC 03595 Appendix I 567 industries of its membership. In addition to publishing and dis tributing, free to members, copies of the proceedings of the annual and midyear meetings, CSMA publishes folders on labeling, caring for industrial floors, and testing products of industries it represents. The Association works with governmental agencies for uniformity in legislation in matters affecting the industry. It has also published compilations of economic poison laws, brake fluid and anti-freeze laws, labeling laws and regulations for hazardous substances, and an aerosol guide. Detailed information about the association or its activities may be obtained from the secretary, A. A. Milliken. A 102-page booklet, C.S.M.A. Vendors to the Trade, is a guide to the material supplies offered by the membership, classifies products by makers, and lists the makers by their products. 17. Chlorine Institute, Inc., 342 Madison Ave., New York, New York (telephone MU 2-4324), is a nonprofit association which provides chlorine producers, users, and firms with related interests to deal constructively with common industry problems in the areas of safety, transportation, regulations, legislation, and community relations. Safety and related experiences and problems are shared through com mittees, principally the technical committee on container specifica tions and safety and the committee on transportation. The results of committee deliberations are distributed on a worldwide basis to chlorine producers and other interested persons in the Chlorine Manual (a 32-page booklet, the third edition was published in 1959) and some 60 engineering and design recommendations, and drawings. A copy of the Institute's current publication list will be sent on request to the secretary, Robert L. Mitchell, Jr. 18. Compressed Gas Association, Inc., 500 Fifth Avenue, New York, New York (telephone LA 4-4796), is a nonprofit membership organiza tion which coordinates activity in the safe handling and use of various compressed and liquefied gases. These include the large tonnage gases, such as oxygen, nitrogen, carbon dioxide, fluorocarbons, hydrogen, acetylene, ammonia, and medical gases.- Standards are available on valves, cylinder testing, and related subjects. A list of pamphlets is available on request. Frank Fetherston is secretary-treasurer. 19. Factory Mutuals Engineering Division, 1151 Boston-Providence Turnpike, Norwood, Massachusetts (telephone Norwood 762-4300) is the inspector and engineering service for several mutual fire insurance companies which write industrial fire insurance. Most of the data on chemicals and other industrial fire sources is available in Handbook of Industrial Loss Prevention, published by McGraw-Hill Book Co., New York, 1959. A monthly newsletter, "Factory Mutual Record," ETC 03596 568 Safety and Accident Prevention in Chemical Operatinng is available by subscription, and frequently contains articles fire-safety aspects of chemicals and other industrial hazards r Magnuson is director of publications. 20. Industrial Hygiene Foundation of America, Inc., 4400 F'ftk Avenue, Pittsburgh, Pennsylvania (telephone MA 1-1100), is an aso ciation of industries and groups interested in industrial health. Sources of information are current literature and reports of the research studie conducted in the foundation's laboratories. These are primarily toxi cological, biochemical, and histopathological investigations The Industrial Digest is a monthly abstract service of the current liters ture, which is published primarily for members. Dr. R. T. P ^ Treville is managing director. 21. Institute of Makers of Explosives, Room 2449, 420 Lexington Ave., New York, New York (telephone MU 3-4229) obtains infor mation and experience reports on explosives and related substances and makes summary reports for its members only. Explosives con sumption reports are sent to the U. S. Bureau of Mines for inclusion in the annual report. An index of the publications issued by the Insti tute on specific subjects, such as the American Table of Distances, and Safety in the Handling of Explosives, is available without charge. 22. Manufacturing Chemists' Association, Inc., 1825 Connecticut Ave., N.W., Washington, D. C. (telephone HU 3-6126), is the trade association representing many of the major producers and users of chemicals. Long aware of the importance of proper instructions for safe handling and proper use of chemicals, various M.C.A. com mittees have developed a large volume of authoritative information on specific substances, as well as on general topics, such as air pollu tion, waste disposal, tank cars, and laboratory safety. For exam ple, nearly a hundred Chemical Safety Data Sheets have been issued, each on specific large volume chemical. A series of chemical safety guides covers miscellaneous aspects of safety in the chemical industry. Guide for Safety in the Chemical Laboratory, 234 pages, was pub lished by D. Van Nostrand Co., Inc., 250 Fourth Ave., New York, New York in 1954 after preparation by the General Safety Committee of M.C.A., and a revised edition is in preparation. The M.C.A. offers a free information service dealing with any aspect of chemical safety. It also furnishes a free list of the various publications which are sold at nominal charge. F. Gordon Stephenson is staff secretary of the general safety and fire protection committee. 23. National Board of Fire Underwriters, 85 John St., New York, New York (telephone BE 3-1400), is an organization of capital stock fire insurance companies, maintained for the purpose of conserving ETC 03597 Appendix 1 569 life and property from fire, explosion and associated effects, by pro viding engineering, statistical, and educational services to the public. It maintains a staff of technically trained experts and research engi neers to evaluate fire and explosion hazards and make recommenda tions for their alleviation. The engineering department is composed of three divisions: municipal surveys, codes and standards, and tech nical research. Standards and recommended practices for a large number of topics which include chemicals in various forms are avail able. A series of research and technical survey reports and special interest bulletins have been issued, including reports on the hazards of salt baths, chlorine dioxide, organic peroxides, and nitroparaffins. T Further details on available information may be obtained by writing or calling the N.B.F.U. Dr. M. M. Braidech is director of research. 24. National Clearinghouse for Poison Control Centers, Division of s Accident Prevention, Poison Control Branch, U. S. Public Health Servj ice, Department of Health, Education and Welfare, Washington, D. C. ((telephone WO 3-7513). This group obtains from many sources in formation on the various chemical constituents of household prod ucts and their toxicity. It welcomes submitted data on composition and emergency treatment of any substance that may be accidentally eaten, breathed, or otherwise find its way into a human body. The information is disseminated to over 500 member poison-control centers in the United States and Canada on 5x8 index file cards. These cards are available to operating poison-control centers, usually desig nated by state health departments. A periodic newsletter is available to anyone working in the area of poisoning, other accidents, or clinical medicine. Mr. Henry Verhulst is director of the national clearing house. The various poison control centers in large cities keep their files open 24 hours a day for emergency consultation by physicians who are called to treat a poisoning case. In addition, an active program of 1 public education on prevention of poisonings from chemicals is under way. 25. National Fire Protection Association, International, 60 Battery- march St., Boston, Massachusetts (telephone HU 2-1630), is a nonprofit technical and educational organization with a total membership of 17,000. Its sole objective is the reduction of loss of life and prop erty by fires and explosions. In addition to the regular publications issued (including the quarterly, which is the technical journal of fire protection), the N.F.P.A. has many active technical committees which develop standards of good practice and other recommendations to safeguard life and property. The N.F.P.A. committee on chern- fiTC U3 5 9 8 570 Safety and Accident Prevention in Chemical Operations icals and explosives, for example, has underway several projects in. volving the safe handling and use of chemicals and related substances Among these projects are a revision of the table of common hazardous chemicals, a code on explosives and blasting agents, a manual of hazardous chemical reactions, and a standard for storage and han dling ammonium nitrate. C. I. Babcock, Jr., is staff chemist and also manager of the fire records department. 26. National Plant Food Institute, 1700 Kay St., N.W., Suite 1004 Washington, D. C. (telephone 296-3225), is the national trade associa tion which promotes the interests of the entire fertilizer industry. Its membership is composed of manufacturers, importers, and brokers of fertilizer and fertilizer materials. The Institute is primarily con cerned with information of value in the storage, handling, and use of all plant foods, but is not concerned with economic poisons. The In stitute strongly supports the program of the Fertilizer Section of the National Safety Council, and conducts a series of accident prevention schools. Numerous publications issued by the Institute include: Plant Food Review (a quarterly magazine available on subscription), a catalogue of films and other visual aids on plant foods and other services of the Institute. Paul T. Truitt is president, and Louis H. Wilson, vice-president of information. 27. National Safety Council, 425 N. Michigan Ave., Chicago, 111. (telephone 527-4800), is a nonprofit organization chartered by the Congress of the United States to work for the prevention of injuries and deaths on the highway, in the home, and on the job. The monthly National Safety News frequently contains articles on chemical safety. The Chemical Section of the Council, which is one of the largest sec tions of the Industrial Division, coordinates information for use by persons using chemicals and allied substances. The Chemical Section Monthly Safety Newsletter is devoted exclusively to chemical safety. Grant Shibley is staff representative, and Julian Olishifski is industrial hygienist. The Occupational Health Nursing Committee, Mrs. A. Kloiber, R.N. chairman, and Mrs. D. Glover, R.N. staff representative, coordinates occupational health work of various other sections of the Council, and develops its own publications including a monthly newsletter. A directory of N.S.C. services is available on request. 28. Society of the Plastics Industry, Inc., 250 Park Ave., New York, New York (telephone MU 7-2675) is a trade association which coordi nates information for the plastics industry. The major technical data are presented in the Plastics Engineering Handbook, 3rd edition, 565 pages, published 1960 by Reinhold Publishing Corp., New York 22, ETC 03599 Appendix I 571 S'. Y. The Plastics Safety Handbook, 208 pages, contains essential information on a safety program for the plastics industry and re lated operations, and was jointly developed by the Society of the Plastics Industry with the National Safety Council in 1959. The S.P.I. Committee on Fire Prevention has developed a series of leaflets on various aspects of fire protection in the plastics industry. Informa tion on various publications with their charges is available by writing the Society in care of William T. Cruse, executive vice-president. 29. U. S. Department of Agriculture, Agriculture Research Service, I Pesticides Regulation Division, Independence Ave., between 12th and 14th St., S.W., Washington, D. C. (telephone RE 7-4142), is the group charged with insuring that commercial products comply with the Federal Insecticide, Fungicide, and Rodenticide Acts of 1947 as amended. Although much of the information is of confidential nature, the group will refer inquiries to the prime manufacturer of the chem ical in question. 30. U. S. Army, Headquarters, Materiel Command, Building T7, Washington, D. C. (telephone OX 5-9595), is to perform assigned ma terial functions of the Department of Army comprising research, development, engineering, testing and evaluation, procurement, and production. All army material is developed, produced, supplied, and maintained by the Army Materiel Command. Director of safety is ! it Fred M. Bishoff. 31. U. S. Department of The Interior, Bureau of Mines, Washington, D. C. (telephone EX 3-6400), is the central administrative group for all activities of the bureau. The Explosives Research Laboratory is part of the Central Experiment Station of the bureau and is located at 4800 Forbes Ave., Pittsburgh, Pa. (telephone MA 1-4500). In formation and reports on chemicals result from the laboratory inves i tigation, and publications appear as Information Circulars, as Reports of Investigations, or in the outside literature. Robert W. Van Dolah is chief, Explosives Research Laboratory. The Health and Safety Activity of the Bureau of Mines also has laboratory facilities at the Central Experiment Station in Pittsburgh. This group tests and publishes approval lists of respiratory protective equipment ranging from dust respirators to self-contained breathing apparatus. Selden J. Pearce is chief, Branch of Health Research. All publications of the Bureau of Mines are listed in ,Vew Pub lications, Bureau of Mines, which is issued monthly. 32. U. S. Department of Health, Education and Welfare, Public Health Service, Communicable Disease Center, Technical Develop ment Laboratories, P. O. Box 769, Savannah, Ga. (telephone 912- ETC 03600 572 Safety and Accident Prevention in Chemical Operations 8972741) is concerned with the toxicology of pesticides and other 1 economic poisons. A list of publications of the Technical Develop. 1 ment Laboratories, listing 289 references published between 1945 and 8 1959, is available on request as Reprint Number 294, "Pesticides in 1 JRelation to Public Health," by Wayland J. Hayes, Jr., reprinted from 3 the Annual Review of Entomology, 5, 379^04, 1960. Clinical Memoranda on Economic Poisons prepared by this group is 4 a 78-page report (Public Health Service Pub. No. 476) on the fun. ! damental aspects of toxicology of common poisons. Dr. Wayland J Hayes, Jr., is a medical director and chief of the toxicology section Toxicology Branch, Communicable Disease Center, U. S. Public Health Service, Atlanta, Ga. (telephone 912, 6345131). , U. S. Public Health Service, Occupational Health Branch, 1014 4 Broadway, Cincinnati, Ohio (telephone DU 1-2200, ext. 681), is a . consulting organization which gathers, digests, abstracts, and re-issues information on occupational health problems including toxicity and safe handling of chemicals. No charge is made for information and publications supplied by this section. Any individual or organization, private or governmental, is privileged to request information and con sultation services on matters of occupational health. Within reason able limits of utilization of staff and facilities, every effort is made to supply requested information. Discretion is exercised with regard to the information but assurance of confidentiality can be granted only for specific cases. An Occupational Health Information Exchange has been established recently by the collection and exchange of informa tion on all aspects of occupational health. Questions, contributions, and cooperation are welcomed. Dohrman H. Byers, scientist director, is in charge of the Occupational Health Information Exchange. 33. U. S. Department of Labor, Bureau of Labor Standards, Divi sion of Safety, Washington, D. C. (telephone EX 3-2420), concerns itself with standards for federal education and regulations of labor. It prepared bulletins, pamphlets, charts, and other educational mate rial for public distribution. Six wall charts on hazards and safe han dling of various chemicals, and seven folders on hazards of other chemicals are included with other publications on labor legislation and administration, and child labor and youth employment. A book let, Selected Publications of the Bureau of Labor Standards, 1962, is available on request. Robert D. Gidel is Director of the Office of Occupational Safety. Dr. F. A. Van Atta is Deputy Director, Office of Occupational Safety. 34. L'nderwriters' Laboratories, Inc., 207 East Ohio St., Chicago, 111. (telephone MI 2-6969), is a nonprofit organization to establish. ETC 03601 I Appendix I 573 maintain, and operate laboratories for the examination and testing of devices, systems, and materials. Sponsored by the National Board of Fire Underwriters, it is operated for service, not for profit. Exam ination and tests of submitted products are conducted by a staff of technically trained and experienced engineers in the following depart ments: electrical, fire protection, gases and oils, chemicals, casualty and automotive, burglary protection, and inspection control. Chem icals of a proprietary type (trade-name labeled) are investigated for fire hazard, and the results are published in the Gas and Oil Equip ment List, issued periodically. Lists with bimonthly supplements, are available free of charge to persons requesting them. Mr. Jack Bono is managing engineer of the Fire Protection Department of U. L. T i ETC 03602 Appendix II Threshold Limit Values for 1964 "Reprinted with permission from the American Conference of Governmental Industrial Hygienists" The threshold limit values refer to air-borne con centrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed, day after day, without adverse effect. Because of wide variation in individual sus ceptibility, exposure of an occasional individual at or even below the threshold limit may not prevent dis comfort, aggravation of a pre-existing condition, or occupational illness. Threshold limits should be used as guides in the control of health hazards and should not be regarded as fine lines between safe and dangerous concen trations. Exceptions are the substances given in Appendix A and certain of the substances given a "C" listing. The values not given a "C" listing re fer to timef-weighted average concentrations for a normal workday. The amount by which these concen trations may be exceeded for short periods without injury to health depends upon a number of factors such as the nature of the contaminant, whether very high concentrations even for short periods produce acute poisoning, whether the effects are cumulative, the frequency with which high concentrations occur, and the duration of such periods. All must be taken into consideration in arriving at a decision as to whether a hazardous situation exists. Enlightened industrial hygiene practice inclines toward controlling exposures below the limit rather than maintenance at the limit. Threshold limits are based on the best available information from industrial experience, from experi mental human and animal studies, and when possible, from a combination of the three. The basis on which the values ate establisned may differ from substance to substance; protection against impairment of health & # ETC 03603 I Appendix il 575 may be the guiding factor for some, whereas reason able freedom from irritation, narcosis, nuisance of other forms of stress may dominate the basis for others. The Committee holds to the opinion that limits based on physical irritation should be considered no less binding than those based on physical impair ment; growing bodies of evidence indicate that physi cal irritation may promote and accelerate physical impairment. On what basis a limit is developed is given separately for each listed substance in '`Docu mentation of Threshold Limit Values," a publication of the Threshold Limits Committee of the ACGIH. Ceiling vs Time-Weighted Average Limits. Al though the time-weighted average concentration pro vides the most satisfactory, practical way of moni toring air-borne agents for compliance with the limits, there are certain substances for which it is inap propriate. In the latter group are substances which are predominantly fast acting and whose threshold limit is more appropiately based on this particular response. Substances with this type of response are best controlled by a ceiling "C" limit that should not be exceeded. It is implicit in these definitions that the manner of sampling to determine compliance with the limits for each group must differ; a single grab sample, that is applicable to a "C" limit, is not appropriate to the time-weighted limit; here, a sufficient number of samples are needed to permit a time-weighted average concentration throughout a a complete cycle of operations or throughout the work shift. Whereas the ceiling limit places a definite bound ary which concentrations should not be permitted to exceed, the time-weighted average limit requires an explicit limit to the excursions that are permissible above the listed value. The magnitude of these ex cursions may be pegged to the magnitude of the thres hold limit by an appropriate factor shown in Appendix C. It should be noted that the same factors are used by the Committee in making a judgment whether to include or exclude a substance for a "C" listing. "Skin" Notation. Listed substances followed by the designation "Skin" refer to the potential con- ETC 03604 576 Safety and Accident Prevention in Chemical Operationt tribution to the over-all exposure by the cutaneous route including mucous membranes and eye. This attention-calling designation is intended to suggest appropriate measures for the prevention of cutaneous absorption so that the threshold limit is not in validated. Mixtures. Special consideration should be given also to the application of these values in assessing the health hazards which may be associated with ex posure to mixtures of two or more substances. A brief discussion of basic considerations involved in de veloping threshold limit values for mixtures, and methods for their development, amplified by specific examples are given in Appendix B. "Inert" or Nuisance Particulates. A number of dusts or particulates that occur in the working en vironment ordinarily produce no specific effects upon prolonged inhalation. Some insoluble substances are classed as inert (e.g. iron and steel dusts, cement, bentonite, silicon carbide, titanium dioxide, cel lulose); others may be soluble (starch, soluble oils, calcium carbonate) but are of such a low order of activity that in concentrations ordinarily encountered do not cause physiologic impairment; still others may be rapidly eliminated or destroyed by the body (veg etable .oils, glycerine, sucrose). In the case of the insoluble substances, there may be some accumula tion in the respiratory passages. In the case of the soluble substances, this accumulation will ordinar ily be temporary but may interfere to some extent with respiratory processes. Hence, it is desirable to control the concentrations of such particulates in the ait breathed by any individual, in keeping with good industrial hygiene practice. A threshold limit of 15mg/m, or 50 mppcf, which ever is less, is recommended for substances in these categories and for which no specific threshold limits have been assigned. This limit, for a normal work day, does not apply to brief exposures at higher concentrations. Neither does it apply to those substances which may cause physiologic impairment at lower concentrations but for which a threshold limit has not yet been adopted. Physical Factors. It is recognized that such phy sical factors as heat, ultraviolet and ionizing radia- I Appendix II 577 tion, humidity, abnormal pressure and the like may place added stress on the body so that the effects from exposure at a threshold limit may be altered. Most of these stresses act adversely to increase the the toxic response of a substance. Although most threshold limits have built-in safety factors to guard against adverse effects of moderate deviations from normal environments, the safety factors of most substances are not of such a magnitude as to take care of gross deviations. For example, continuous work at temperatures above 90F or over-time, ex tending the work-week more than 50%, might be considered gross deviations. In such instances judg ment must be exercised in the proper adjustments of the threshold limit values. These limits are intended for use in the field of industrial hygiene and should be interpreted and applied only by persons trained in this field. They are not intended for use, or for modification for use, (1) as a relative index of toxicity, by making a ratio of two limits, (2) in the evaluation or control of community air pollution or air pollution nuisances, (3) in estimating the toxic potential of continuous uninterrupted exposures, (4) as proof or disproof of an existing disease of physical condition, or (5) for carte blanche adoption by foreign countries. These values are reviewed annually by the Com mittee on Threshold Limits for revisions or additions, as further information becomes available. "Notice of Intent." At the beginning of each year, proposed actions of the Committee for the forth coming year are issued in the form of a "Notice of Intent." This Notice provides not only an oppor tunity for comment, but solicits suggestions of sub stances to be added to the list. The suggestions should be accompanied by substantiating evidence. Legislative Action The Conference does not consider the Threshold Limit Values appropriate matter for adoption in legislative codes and regula tions, and recommends against such use. Reprint Permission. This publication may be re printed provided that written permission is obtained from the Secretary-Treasurer of the Conference and that it be published in its entirety. ETC 03606 578 Safety and Accident Prevention in Chemical Operation* RECOMMENDED VALUES (In Alphabetical Order) Substance ppm* Mg'M*** Acetaldehyde................................. 200 Acetic acid...................................... 10 Acetic anhydride ......................... 5 Acetone.............................................. 1,000 Acetonitrile.................................. 40 Acetylene tetrabromide................ 1 Acrolein............................................ 0. 1 Acrylonitrile - Skin...................... 20 Aldnn (1, 2. 3, 4, 10, 10- hexachloro- 1, 4, 4a, 5, 8. 8 a-hexahydio-1, 4, 5, 8-di- methano-naphthalene) Skin. - Allyl alcohol - Skin........................ 2 Ally I chloride.................................. 1 C Allyl glycidyl ether (AGE).. .. 10 Allyl propyl disulfide.................. 2 Ammonia..................... 50 Ammonium sulfamate (Ammate) . - Amyl acetate................................... 100 Amyl alcohol (isoamyl alcohol). 100 Aniline - Skin................................... 5 Antimony & compounds (as Sb) - ANTU (alpha naphthyl thiourea)....................................... - Arsenic & Compounds (as As) - Aisine .............................................. 0.05 Barium (soluble compounds)...... - C Benzene (benzol) - Skin. . 25 Benzidine......................................... - Benzyl chloride.............................. 1 Beiy Ilium......................................... - Boron oxide..................................... - 360 25 20 2.400 ?o 14 0.25 45 0.25 5 3 45 12 35 15 525 360 19 0.5 0.3 0.5 0.2 0.5 80 Al 5 0.002 15 ' Parts of vapor or gas per million parts of air by volume at 25C and 760 mm. Hg pressure, 'Approximate milligrams of particulate per cubic meter of air. A Numbers, See Appendix A ETC 03R07 Appendix II 579 Subsfance ppm* Mg/M3** C Boron tiifluonde............................ 1 3 Bromine............................................. 0.1 0.7 Butadiene (1, 3-butadiene).........1,000 2,200 2-Butanone Imethyl ethyl ketone).......................................... 200 590 2-Butoxy ethanol (Butyl Cellosolve) - Skin.................... 50 240 Butylacetate (n-butyl acetate)200 950 Butyl alcohol.................................... 100 300 teit. Butyl alcohol ..................... 100 300 C Butylamme...................................... 5 15 C tert. Butyl chromate (as CrO a} - Skin........................................ - 0,1 n - Butyl glycidyl ether (BGE).... 50 270 Butyl mercaptan.............................. 10 35 p-tert. Butyltoluene.................... 10 60 Cadmium oxide fume..................... - 0.1 Calcium arsenate ............ - 1 Camphor ......................................... - 2 Carbon dioxide...................................5,000 9,000 Carbon disulfide - Skin................ 20 60 Carbon monoxide............................. 100 110 Carbon tetrachloride -Skin........ 10 65 Chlotdane (1, 2, 4, 5, 6, 7, 8, 8-octachloio-3a, 4, 7, 7a. tetrahydro-4, 7-methanoin- ! danei .................................. Chlorinated camphene, 60%....... - 0.5 0.5 Chlorinated diphenyl oxide........ - 0.5 1 Chlorine............................................ 1 3 i Chlorine dioxide............................ 0.1 0.3 C Chlorine trifluoride........................ 0.1 0.4 C Chloioacetaldehyde....................... 1 3 i Chlorobenzene (monochlorobenzene)..................... 75 350 Chlorobromomethane.................... 200 1,050 Chlorodiphenyl (42% chlorine) - Skin- 1 Chlotodiphenyl (54% chlorine) - Sktn- 0.5 i C Chloroform (tnchloromethane).... 1-Chloro-l-nitiopiopane............... 50 20 240 100 Chloropicrin..................................... 0.1 0.7 Chloroprene (2-chloro-l, 3-butadiene) . .. 25 90 ETC 03608 580 Safety and Accident Prevention in Chemical Operations Substonce ppm* Mg/M** Chromic acid and chromates (as Cr03) Cobalt............................................... - Crag (R) herbicide |_sodium 2-(2, 4- dichlorophenoxy) ethanol hydrogen sulfate]j _ Cresol (all isomers) Skin......... Cyanide (as CN) - Skin................ 5 - Cyclohexane.................................... . 400 Cyclohexanol................................. 50 Cyclohexanone............................... 50 Cyclohexene.................................... . 400 2, 4-D (2,4-dichlorophenoxy -acetic acid)..................... _ DDTj_2, 2-bis (p-chloropheny 1) - 1, 1, l-trichloroethane~j- Skin - DDVP (0, O-Dimethyl-2, 2-dichloro- vinyl phosphate) ... - Decaborane - Skin......................... 0.05 Diacetone alcohol (4-hydtoxy- 4-methyl-2-pentanone) 50 Diborane.......................................... 0.1 1,2-Dibromoethane (ethylene dibromide).................................. 25 + C o-Dichlotobenzene ....................... 50 p-Dichlorobenzene......................... 75 Dichlorodifluoiomethane............. .1,000 1,1-Dichloroethane...................... 100 1, 2-Dichloroethane (ethylene dichloride) .. 50 1, 2-Dichloroethylene.................. . 200 C Dichloroethyl ether...................... 15 Dichloromonofluoromethane...... 1,000 C 1 1-DiChloro-l-nitroethane......... 10 Dichloiotetratluoroethane........... .1,000 Dieldrin (1,2,3, 4,10,10-hexachloro -6, 7-epoxy-l, 4, 4a, 5,6, 7, 8,8a- octahydro-1, 4, 5, 8-dimethano- naphthalene) - Skin................. - Diethylamine................................... 25 0. 1 0.5 15 22 5 1,400 200 200 1,350 10 1 1 0.3 240 0.1 190 300 450 4,950 400 200 790 90 4,200 60 7,000 0.25 75 + 1964 Addition or deletion of "C** t!964 Revision - see Tentative Values ETC 03609 Appendix II 581 Substance ppm* Mq/M1** Difluorodibromomethane............... 100 Diglycidyl ether (DGE)................. 0.5 Dusobutyl ketone.......................... 50 Dimethyl acetamide - Skin.......... 10 Dimnthylaniline (N-dimethyl- aniline) Skin................................. 5 Dimethylformamide - Skin............. -- 1,1-Dimethylhydrazine Skin .... 0. 5 Dimethylsulfate - Skin................. 1 Dinitiobenzene - Skin.................... - Dinitiotoluene Skin...................... - Dinitto-o-cresol - Skin................. - Dioxane (diethylene dioxide)...... 100 Dipiopylene glycol methyl ether Skin.................................. 100 Endrin (1,2,3, 4,10,10- hexa- chloro-6, 7-epoxy-l, 4, 4a, 5, 6, 7, 8 8a-octahydro l,4-endo-5, 8-dimethanonaphthalene) - Skin.. -- EPN (O-ethyl O-p-nitrophenyl thionobenzenephosphonate) Skin - Ethyl acetate................................... 400 Ethyl acrylate - Skin.................... 25 Ethyl alcohol (ethanol)................ .1,000 Ethylamine...................................... 25 C Ethylbenzene.................................. . 200 Ethyl bromide.................................. . 200 Ethyl chloride................................ .1,000 Ethyl ether....................................... . 400 Ethyl formate.................................. . 100 C Ethyl mercaptan ........................... 20 Ethyl silicate................................. . 100 Ethylene chlorohydrin - Skin..... 5 Ethylenediamine............................ C Ethylene glycol dinitrate - Skin 10 0.2 Ethylene imine - Skin.................. 5 Ethylene oxide................................ 50 2-Ethoxyethanol (Cellosolve) - Skin................... . 200 2-Ethoxyethanol (Cellosolve) - Skin .................. 200 2-Ethoxyethylacetate (Cellosolve acetate) - Skin .. . 100 860 2.8 290 35 25 1 5 1 1.5 0.2 360 600 0.1 0.5 1,400 100 1,900 45 870 890 2,600 1,200 300 52 850 16 30 1. 9 90 740 740 540 * Safety and Accident Prevention in Chemical Operation* Substance ppm* Ferbam (feme dimethyl ....dithiocaibamate) ............. .....Ferrovanadium dust ............ .....Fluonde (as F) .................. - Fluorine.................................. ......... 0.1 Fluorotrichlorome thane....... .........1,000 Formaldehyde ....................... ......... 5 Furfural.................................... ........ 5 Furfuryl alcohol..................... ......... 50 Gasoline.................................. ......... 500 Glycidol (2, 3 - Epoxy-1 - propanol)............................. ......... 50 Heptachlor (1, 4, 5, 6, 7, 8, 8a-heptachloro -3a, 4, 7, 7a-tetrahydro-4, 7- methanorndane............................. - Heptane (n -heptane)...................... 500 Hexane (n-hexane)........................ 500 Hexanone (methyl butyl ketone) 100 sec-Hexyl acetate........................ 50 Hexone (methyl isobutyl ketone) 100 Hydrazine - Skin ........................... 1 Hydrogen bromide.......................... 3 Hydrogen chloride.......................... Hydrogen cyamde-Skin............... 5 10 Hydrogen fluoride.......................... 3 Hydrogen peroxide, 90%............... 1 Hydrogen selenide.......................... Hydrogen Sulfide ................. 0.05 Hydroquinone................................... - Iodine ................................................. Iron oxide fume.............................. 0.1 - Isophorone ........................................ 25 Isopropylamine................................. 5 Isopropyl glycidyl ether (IGE).... 50 Ketene................................................ 0.5 Lead................................................... - Lead arsenate ................................. ~ Lindane (hexachlorcyclohexane, gamma isomer)............................ - Lithium hydride............................... - 15 1 2.5 0.2 5,600 6 20 200 2,000 150 0.5 2,000 1,800 410 295 410 1.3 10 7 11 2 1.4 0.2 " 2 1 15 140 12 240 0.9 0.2 0.15 0.5 0.025 + 1964 Addition or deletion { *'CM 11964 Revision see Tentotive Values ETC 03611 1 Appendix II 583 Substance ppm* Magnesium oxide fume................ - Malathion (0,0-dimethyl dithiophosphate of diethyl mercaptosuccinate) - Skin..... - C Manganese ....................................... - Metcuiy - Skin................................ Mercury (organic compounds) - Skin................................................ - Mesityl oxide.................................. 25 Methoxychlor (2, 2-di-p- methoxy-phenyl-1, l, 1- trichloroethane)......................... - Methyl acetate................................ . 200 Methyl acetylene........................... .1,000 Methyl acrylate - Skin ................ 10 Methylal (dimethoxymethane)..... .1,000 Methyl alcohol (methanol)......... . 200 C Methyl bromide - Skin.................. 20 Methyl cellosolve (2-methoxy- ethanol) - Skin........................... 25 Methyl cellosolve acetate (ethylene glycol monomethyl ether acetate) - Skin................ 25 C Methyl chloride.............................. . 100 Methyl chloroform (1, 1, 1-tri- chloroethane).............................. . 350 Methylcyclohexane....................... . 500 Methylcydohexanol......................... 100 Methylcyclohexanone.................. . 100 Methyl formate.................................. 100 Methyl isobutyl carbinol (methyl amyl alcohol).............. 25 t Methyl mercaptan........................... - + C a Methyl styrene........................... .. 100 Methylene chloride (dichloromethane).................... ,. 500 Monomethyl aniline - Skin......... 2 Molybdenum ( soluble compounds).................................. - (insoluble compounds)........... - M9/M3** 15 15 5 0.1 0.01 100 15 610 1,650 35 3,100 260 80 80 120 210 1,900 2,000 470 460 250 100 480 1,750 9 5 15 + 1964 Addition or deletion of "C** t!964 Revision - see Tentotive Volue* TC 03 Sl 2 I I 584 Safety and Accident Prevention in Chemical Operatiom Subsronce ppm* Mg/MJ** Naphtha (coal tai)........................... 200 800 Naphtha (petroleum)...................... 500 2,000 (3 - Naphthylamine........................... - A2 Nickel carbonyl............................... 0.001 0.007 Nicotine - Skin................................. - o. 5 j Nitric acid........................................ - _ p-Nitroamline - Skin..................... 1 6 Nitrobenzene - Skin....................... 1 5 Nitroethane......................................... 100 310 C Nitrogen dioxide............................. 5 9 C Nitroglycerin - + EGDN - Skin... 0.2 2 Nitromethane.................................... 100 250 1 - Nitropropane............................... 25 90 2 - Nitropropane ............................. 25 90 N Nitiosodimethylamine (Oi- methylmtiosamine) - Skin A3 Nitrotoluene - Skin........................ 5 30 Octane................................................ 500 2,350 Oil mist (mineral)......................... - 5 Osmium tetroxide........................... - 0.002 Ozone................................................. 0.1 0.2 Parathion (O, O-diethyl O-omtrophenyl thiophosphate) - Skin.............................................. - 0.1 Pentaborane..................................... 0.005 0.01 Pentachloronaphthalene - Skin - 0.5 Pentachlorophenol Skin............ - 0.5 Pentane ............................. 1,000 2,950 Pentanone (methyl propyl ketone)......................................... 200 700 Perchloroethylene (tetra- chtoroethylene)........................... 100 670 Perchloromethyl mercaptan ........ 0.1 0.8 Perchloryl fluoride........................ 3 13.5 Phenol Skin.................................... 5 19 Phenyl glycidyl ether (PGE)...... 50 310 Phenylhydtazine - Skin.................. 5 22 Phosdrin (2-carbomethoxy -1- methyl vinyl dimethyl phosphate)................................... - 0.1 + 1964 Addition or deletion of *'C** tl964 Revision - see Tentative Values | ETC 03613 Appendix // 585 Substance ppm * Mg/M1** f Phosgene (carbonyl chloride)... - - Phosphine.......................................... 0.3 0.4 Phosphoric acid.............................. - 1 Phosphorus (yellow)..................... - 0.1 Phosphorus pentachloride......... - 1 Phosphorus pentasulfide............. - 1 Phosphorus trichloride............... 0.5 3 Picric acid - Skin.......................... -- 0.1 Platinum (Soluble Salts)............... - 0.002 Piopyl acetate................................ 200 840 Propyl alcohol (isopropyl alcohol).......................................... 400 980 Propyl ether (isopropyl ether).... 500 2,100 n-Piopyl nitrate................................ 25 110 Propylene dichloride (1, 2- dichloropropane)........................... 75 350 Propylene imine Skin................. 25 60 Propylene oxide............................... 100 240 Pyrethrum.......................................... - 5 Pyridine................................................. 5 15 Qumone.............................................. 0.1 0.4 Rotenone (commercial)................ - 5 j Selenium compounds (as Se)...... - - Sodium fluoroacetate (1080) -Skin.............................................. - 0.05 Sodium hydroxide............................ - 2 Stibme................................................. 0.1 0.5 Stoddard solvent............................ 500 2, 900 Stiychnine.......................................... -- 0.15 + C Styrene monomer (phenylethylene)........................ 100 420 Sulfur dioxide........................................ 5 13 Sulfur hexafluoride.......................... 1,000 6,000 Sulfuric acid..................................... - 1 Sulfur monochloride........................ 1 6 Sulfur pentafluoride........................ 0.025 0.25 Sulfutyl fluoride.................................... 5 20 2, 4, 5T (2, 4, 5 trichlorophenoxyacetic acid).. - 10 TEDP (tetraethyl dithionopyrophosphate)-Skin.. - 0.2 + 1964 Addition or deletion of "C" t!964 Revision - see Tentative Volues ETC 03614 586 Safety and Accident Prevention in Chemical Operations Substance ppm* Mg, MJ** Teflon (R) decomposition products . . .................. - TEPP (tetraethyl pyro- phosphatei Skin . .. - Tellurium - 1, 1, 2, 2 - Tetrachloroethane - Skin ................ 5 Tetrahydrofuran ..................... 200 Tetranitiomethane ................... 1 Tettyl (2, 4, 6 - trimtrophenyl - methylmtiamine) Skin....... - Thallium (soluble compounds) - Skin............................................. - Thiram (tetiamethyl thiuiam disulfide) .. - Titanium dioxide......................... - + Toluene (toluol) ..................... 200 o - Toluidme * Skin...................... 5 CTolylene-2, 4-dnsocyanate..... 0.02 Tfichloioethylene......................... 100 Trichloronaphthalene-Skin ....... - 1, 2, 3 - Tnchloropropane......... 50 1, 1, 2-Ttichtoto 1, 2, 2- trifluoroethane........................... 1,000 Triethylamme................................. 25 Tr if luoiomonobfomomethane...... 1,000 Tiinittotoluene-Skm.................... - Triorthocresyl phosphate.......... - Tuphenyl phosphate................... - Turpentine...................................... 100 Uranium (soluble compounds) . , - (insoluble compounds) , . . - C Vanadium (V 20 5 dust). IV2O 5 fume).................. .......... - C Vinyl chloride (chloroethylene). 500 Vinyl toluene ............................... 100 War far in (3 i_a acetonylbenzyQ^- hydroxycoumarin)....................... - C Xylene (xylol) .............................. 200 Xylidine - Skin............................... 5 A4 0.05 0.1 35 590 8 1.5 0.1 5 15 750 22 0.14 520 5 300 7,600 100 6,100 1.5 0.1 3 560 0.05 0.25 0. 5 0.1 1,300 480 0.1 870 25 + 1964 Addition or deletion of "CM t1964 Revision see Tentative Values Appendix II 587 Subsfonce ppm* Mg/M3** t Yttrium ................................... Zmc oxide fume.............................. Zirconium compounds (as Zr)... - 5 5 Radioactivity: for permissible concentrations of radio isotopes in air. see U S Department of Commerce. National Bureau of Standards. Handbook 69. "Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radi onuclides m Air and m Water for Occupational Exposure." June 5, 1959 Also, see U S. Department of Commerce National Bureau of Standards, Handbook 59. 'Permissible Oose from External Sources of ionizing Radiation," September 24, 1954. and addendum of April 15. 1958. * Parts of vapor or gas per million parts of air by volume at 25 C and 760 mm. Hg pressure * Approximate milligrams of particulate per cubic meter of air. A Numbers. See Appendix A 11964 Revision see Tentotive Volues MINERAL DUSTS Substance m.p.p.c.f.- SIIICA Crystalline Quartz, Threshold Limit calculated 250 ** from the formula .... %Si02+ 5 Cristobalite Amorphous, including natural diatomaceous earth ..................................... 20 SILICATES (less than 1% crystalline silica) Asbestos ........... 5 Mica ....................................................... 20 Soapstone ........................................................ 20 Talc .............................................. 20 Portland Cement .......................................... 50 "Inert" or Nuisance Particulates 50 (or 15 mg/m 3 whichever is the smaller) Conversion factors mppcf * 35.3 million particles per cubic meter = particles per c.c. e Millions of particles per cubic foot of air. based on impinger samples counted by light-field technics. * The percentage of crystalline silica m the formula is the amount determined from air-borne samples, except in those instances in which other methods have been shown to be applicable. ETr 03616 588 Safety and Accident Prevention in Chemical Operations 1 TENTATIVE VALUES Substance ppm* H-Anisidine (o, p-isomeis). .. -H-Benzoyl peroxide....................... Calcium oxide................................ -H-Carpaiyl (Sevin) (R).................... Copper Fume Dusts & Mists `Cotton Oust (raw)....................... -H-Cyclopentadiene .............. 75 Demeton (Systox) (R).................. ++1, 3 - Dichloro - 5, 5-dimethyl hydantoin ................................. -H-Dimethyl l, 2-dibromo-2, 2- dichloioethyl phosphate, iDibiom) (Rl H-Dimethylamine............................... 10 + Dimethylfoimamide - Skin 10 t+Di sec. octyl phthalate {Di*2* ethylhexyl-phthatatel ........... Epichlorhydrin................................ 5 Ethanolamme ............................. Graphite ........................................ 3 - Hafnium ............. - H-Hexachloroethane - Skin.............. 1 +Hydrogen Sulfide .......................... 10 ++L. P. G. (Low pressure gas) (Liquid petroleum gas) .......... 1,000 -t Maleic anhydride........................... - -Methane............................................. 1,000 H-Methyl acetylene-propadlene mature, IMAPP) .................. 1,000 Methylamine.................................... 25 + Methyl mercaptan....................... 10 Methyl methacrylate 100 C Methylene bis phenylisocyanate 0.02 Mineral wool, fibrous glass . . - H-Monomethyl hydiazine - Skin..... 0.2 `--Morpholine Skin........................... 20 0.5 5 5 5 0.1 1.0 1 200 0.1 0.2 3 18 30 5 19 6 15mppr 0. 5 ' 9.7 15 8 - - 31 20 410 0.2 2 035 70 * Parts of vapor or gas per million parts of air by volume at 25C and 760 mm. Hg pressure. ** Approximate milligrams of particulate per cubic meter of ETC 03617 I Appendix 11 589 Subltonce ppm* Mg/M1** Naphthalene..................................... -H-NIckel, metal and soluble compounds................................... +Nitric Acid ..................................... ++p-Nitrochlorobenzene................... ++Nitrogen trifluoride......................... C ++Oxygen difluoride.......................... ++p-Phenylene diamine-Skin........ 10 2 10 o.05 - 50 i 5 1 29 0.1 o. 1 +Phosgene.......................................... 0.1 0.4 H-Phthalic anhydride.......................... 2 12 ++Propane.................................................1,000 1,800 f (3 Propiolactone............................... - AS I +Selenium compounds...................... - 0.2 I +Silver, metal and soluble com pounds............................................ - 0.01 Tantalum............................................ - 5 +1, 1, 1, 2-Tetrachloro-2, . 2-difluoroethane........................ 500 4,170 j 1, 1, 2, 2-Tetrachloro-l, * 2-difluotoethane......................... 500 4, 170 Tetraethyl lead-Skin..................... Tin (inorganic compounds)........... (organic compounds as Sn) -Skin............................................. +Yttnum............................................... - - 0.075 2 0.1 1 * Parts of vapor or gis per million parts of air by volume at 25*C and 760 mm. Hg pressure. *'Approximate milligrams of particulate per cubic meter of air. A numbers. See Appendix A +1964 Revisions. ++1964 Additions. Appendix A A' Benzidine. Because ol high incidence of bladder [ tumors in man, any exposure, including skin, is extremely hazardous. A' tf-Naphthylamine. Because of the extremely high incidence of bladder tumors in workers handling this compound, and the inability to control ex- : posures, g-naphthylamme has been prohibited i from manufacture, use and other activities that in volve human contact by the State of Pennsylvania. ETC 03618 590 Safety and Accident Prevention in Chemical Operations A1 N-Nitrosodimethylamme Because of extremely high toxicity and presumed carcinogenic potential of this compound, contact by any route should not be permitted. A* Teflon decomposition products. At least one identi fied component of Teflon decomposition products is extremely toxic, but in the absence of more complete toxicity information and suitable analytic methods, a definite Threshold Limit Value is not recommended at this time, but air concentrations should be minimal. As -Propiolactone. Because of high acute toxicity and demonstrated shin tumor production in animals, contact by any route should be avoided. Appendix B THRESHOLD LIMIT VALUES FOR MIXTURES When two or more hazardous substances are present, their combined effect, rather than that of either indi vidually, should be given primary consideration. In the absence of information to the contrary, the effects of the different hazards should he considered as additive. That is. if the sum of the following fractions, _C^ + _Ci+ . . Cn T- T.- Tn exceeds unity, then the threshold limit of the mixture should be considered as being exceeded. Ciindicates the observed atmospheric concentration, and T- the corres ponding threshold limit, (See Example lA.a.I. Exceptions to the above rule may be made when there is good reason to believe that the chief effects of the different harmful substances are not in fact additive, but independent as when purely local effects on different organs of the body are produced by the various com ponents of the mixture. In such cases the threshold limit ordinarily is exceeded only when at least one member of the series (C- or C-- etc.I itself has a value 7" 77 exceeding unity, (See Example lA.b.). Antagonistic action or potentiation may occur with some combinations of atmospheric contaminants. Such cases at present must be determined individually. Poten tiating or antagonistic agents are not necessarily harm ful by themselves. Potentiating effects of exposure to such agents by routes other than that of inhalation is also possible, eg. imbibed alcohol and inhaled narcotic (trichloroethylene) Potentiation is characteristically ex hibited at high concentrations, less probably at low. ETC 0;ST19 r | i t i Appendix II 591 When a given operation or process characteristically emits a number ot harmful dusts fumes, vapors or gases, it will frequently be only feasible to attempt to evaluate the hazard by measurement of a single sub stance In such cases, the threshold limit used for this substance should be reduced by a suitable factor, the magnitude of which will depend on the number, toxicity and relative quantity of the other contaminants ordi narily present. Examples of processes which are typically associated with two or more harmful atmospheric contaminants art welding, automobile repair, blasting, painting, lacquering, certain foundry operations, diesel exhausts, etc. (Example 21 THRESHOLD LIMIT VALUES FOR MIXTURES EXAMPLES 1A General case, where air is analyzed tor each com ponent. a ADDITIVE EFFECTS C, C_ T, T. =1 Air contains 5 ppm of carbon tetrachloride (TLV, 101, 20 ppm of ethylene dichloride (TLV,50) and 10 ppm of ethylene dibromide, (TLV, 25). _5_____ M JLO 10 + 50 + 25 65 50 1.3 Threshold limit is exceeded. b INDEPENDENT EFFECTS Air contains 0.15 mg/mJ of lead (TLV, 0.2) and 0.7 mg/m1 of sulfuric acid (TLV, 1). 0.15 0.75; 0.7 = 0.7 0.20 Threshold limit is not exceeded. 16. Special case when source of contaminant is a mixture and atmospheric composition is assumed similar to that of original material, i.e. vapor pres sure of each component is the same at the observed temperature. a ADDITIVE EFFECTS, approximate solution. 1. A mixture of equal parts (I I trichloroethylene (TLV. 1001, and (2) methyl chloroform (TLV 350) ETC 03620 etc 03621 r 1 i Appendix II 593 T = Threshold Limit Value m ppm C = Vapor concentration in ppm p = Vapor pressure of component in solution. p = Vapor pressure of pure component. f = Mol fraction of component in solution. a - A constant of proportionality Subscripts 1.2, . n relate the above quantities to components 1.2, n, respectively. Subscript i refers to an arbitrary component from 1 to n. Absence of subscript relates the quantity to the mixture. Solution to be applied when there is a reservoir of the solvent mixture whose composition does not change appreciably by evaporation Exact Arithmetic Solution of Specific Mixture Mol. wt. Density T Trichloro ethylene ID 131.4 1.46 g/ml 100 p" at 25C Mol frac tion in half-and half solu tion by volume 73mm Hg 0.527 Methylchloroform 12) 133.42 1.33 g/ml 350 125mm Hg 0.473 F,p, = (0.527) (73) = 38.2 F:p,, = (0.473) (125) = 59.2 T = 38.2 + 59.2 = (97.4) (350) = (97.4) (3501 = 177 38^+59/2 133.8 + 59.2 193.0 100 350 T = 177 ppm (Note difference in T.L.V. when account is taken of vapor pressure and mol fraction in comparison with above example where such account is not taken). ETC 03622 ETC 03623 r Appendix II 595 Appendix C BASES FOR ASSIGNING LIMITING "C" VALUES By definition in the Preface, a listed value bear ing a "C" designation refers to 'ceiling' value that should not be exceeded; all values should fluctuate below the listed value. In general the bases for assigning or not assigning a "C" value rest on whether excursions of concentration above a proposed limit for periods up to 15 minutes may result in a) intolerable irritation, b) chronic, or irreversible tissue change, or c) narcosis of sufficient degree to increase accident pioneness, impair self rescue or materially reduce work efficiency. In order for the Committee to decide whether a sub stance is a candidate for a "C" listing, some guidelines must be formulated on the permissive fluctuation above the limit in terms of the seriousness of the response in the categories a, b, c, given above. For this the factors given in the table below have been used by the Committee. For both technical and practical reasons, the factors have been pegged to the concentration in an inverse manner. It will be noted that as the magnitude of the T. L. V. increases a correspondingly decreased range of fluctuation is permitted; not to decrease the factor for T. L. V.'s of increasing magnitude would permit exposures to large absolute quantities, an undesirable condition, a condition that is minimized at low T. L. V.'s. More over, larger factors at the lower T. L. V.'s are con sistent with the difficulties in analyzing and con trolling trace quantities. T.L.V. RANGE ppm* pr mt/mJ 0 to 1 1 + to 10 Test T.t.V. Fictor Examples 3 Toluene diisocyanate-T. L. V., 0.02 ppm, if permitted to rise above 0.06 ppm may result in sensitization m a single sub sequent exposure. "C" listing recommended on category b. 2 Maganese-T. L. V., 5mg m!, contains little or no safety factor. All values should flucuate below 5mg m'. "C" listing recommended on category b. ETC 03624 596 Safety and Accident Prevention in Chemical Operations T.I.Y. Test RANGE T.l.V. ppm* or mg/mr Factor 10+to 100 1.5 100+to 1000 1.25 Examples Methyl styrene-T. L. V. 100 if encountered at levels of 150 ppm will prove intense ly irritating, "C" listing recommended on category a. Methyl chlotofotm-T. L. V. 350ppm. at 438 ppm for per iods not exceeding 15 min utes is not expected to re sult in untoward effects relating to category c. No "C" listing recommended. * Whichever unit is applicable As stated in the preface, the same factors may be used as guides for reasonable excursions above the limit foi substances to which the time-weighted average applies. The time-weighted average implies that each excursion above the limit is compensated by a com parable excursion below the limit. Harry B. Ashe E. J. Baier Allan L. Coleman Hervey B. Elkins Bernard Grabois Harold N. MacFarland.Consultant E. Mastromatteo William F Reindollai Russel G. Scovill Ralph G Smith Wayland J. Hayes, Jr. Mitchell R Zavon Keith Jacobson Herbert E. Stokinger, Chairman ETC 03625 Appendix 11 597 Copyright 1964, by American Conference of Governmental Industrial Hygienists. The American Conference of Governmental Industrial Hygienists will welcome requests for permission to republish or reprint these Threshold Limit Values. Requests (or such permission should be directed to the Secretary-Treasurer, 1014 Broad way, Cincinnati 2. Ohio. Reprints may be purchased from the SecretaryTreasurer, 1014 Broadway, Cincinnati 2, Ohio. [ ETC 03626 598 ETC 03627 Appendix IV Identification of Contents Proper and adequate designation of the contents of packages, bottles, carboys, drums, tank trucks, tank cars, tank ships, stationary tanks, and warehouses is important to the health and safety of the public as well as employees of manufacturing and transportation facilities. Public Law 86-613,1 Federal Hazardous Substances Labeling Act clearly specifies the information required on consumer packages. Sev eral states and a few cities have similar ordinances intended to protect the public. Much preliminary work by committees of the Manufac turing Chemists' Association,2 Association of British Chemical Manu facturers,3 American Petroleum Institute,4 and others contributed to the background of precautionary labeling. MCA manual L-l2 is a partic ularly good source for proper wording of labels supplying the following information: 1. Name of the Product 2. Signal Word 3. Statement of Hazard 4. Precautions 5. First Aid and/or Emergency Action 6. Container Handling and Storage The Interstate Commerce Commission5 designates certain labels that must be affixed to packages and vehicles moving in interstate trade or by common carrier. Since their system is rather specific in exempting certain types of compounds and sizes of packages, the reader is referred to the reference manual for information. A familiar ICC requirement is that of labeling tank trucks to advise the public of the general nature of the hazard of its contents flammable, corrosive, etc. This informa tion is quite general and does not specify the degree of hazard. A recent activity of the Manufacturing Chemists' Association is the development of Chem-Cards to be given to truck drivers at the time of loading. Each card describes in simple language the hazards of one argo and instructs the driver and others in steps to be taken undei mergency conditions. - Inside the industrial plant the identification problem is two-fold: to ainimize error in operations or maintenance and to safeguard the lives 'f personnel in time of fire or other emergency. ASA Standard A13.1--1956, Scheme jor the Identification of Piping 599 600 Safety and Accident Prevention in Chemical Operations ETC 03629 r Appendix III 601 ETC 03630 I 602 Safety and Accident Prevention in Chemical Operations Systems,8 describes a combination of name designations with codes describing broad classes of contents'. Yellow. Hazardous Green. Nonhazardous Blue. Protective Red. Fire Lines Violet. High Value Materials NFPA 704-M--1964, Recommended System for the Identification of the Fire Hazards of MaterialsJ is an outgrowth of work initiated about 1952 by the NFPA Flammable Liquids Committee incorporating an idea proposed by James J. Duggan.15 He suggested a system for inplant use to mark tanks, process vessels, storage areas, lines, etc. Haz ards are identified in three categories, "health," "flammability," and "reactivity" (stability). Order of severity is expressed by numbers from "0" (no hazard) to "4" (severe hazard). Table III.l outlines the degrees of severity within each category. Figure III.l illustrates three alternate schemes for application of the diamond-shaped signals to plant tanks and other structures. The reader is referred to the most recent edition of NFPA 704-M for further details. NFPA 325, Prop erties of Flammable Liquids and NFPA 49M, Hazardous Chemicals Data will probably be revised to include the degrees corresponding to the three categories of 704-M. REFERENCES 1. Federal Register, April 29, 1961 and July 31. 1962. 2. Manual L-l, Guide to Precautionary Labeling oj Hazardous Substances, Sixth Edition, 1961, Manufacturing Chemists' Association, 1825 Connecticut Avenue, N.W., Washington, D, C. 3. Marking Containers (1958) Association of British Chemical Manufacturers. 166 Piccadilly W. 1, London. 4. API Bulletin on Precautionary Labels, API Bulletin 2511, Second Edition, 1964. American Petroleum Institute, 1271 Avenue of the Americas, New York, N. Y. 5. T. C. George, Interstate Commerce Regulations for Transportation of Ex plosives and Other Dangerous Articles--Tariff No. 15, 1963, Bureau of Explo sives, Assoc, of Amer. Railroads, 63 Vesey Street, New York, N. Y. 6. Scheme for the Identification of Piping Systems, A13.1-1956, American Stand ards Association. 10 E. 40th Street, New York 16, N. Y. 7. Recommended System for the Identification of the Fire Hazards of Materials, NFPA No. 704-M 1964, National Fire Protection Association, 60 Batterymarch Street, Boston, Mass. 8. J. J. Duggan, See Hazards cif a Glance, Chem. Eng. 66', #4, p. 162-166, Febru ary 23, 1959. FTC 03631 w Index Absenteeism, effect of alcoholism, 237 Absorption, 112, 255-258. 268, 271. 281; see also Toxicity Acceptance,safety, 12 Accident cost, 2-4, 15, 551-553 Accident proneness, investigations, 238- 239 psychological testing for, 237-238 Accidents without injuries, 230 Acetic acid. 332 Acetylenic compounds, 300 Acid area work permit, 461; see also Permits Acid-oil shoes. 444; see also Shoes Acoustics engineer, 440; see also Noise control Activation, energy of, 81 Acts, unsafe, 225-226 Administrative offices, location of, 45 Adsorbent, in firefighting, 505-506 Aerosols, 254-255, 376-377; see also Air, Respiratory hazards AFL-CIO Standing Committee on Oc cupational Safety and Health, 16 After hours operation permit, 458; see also Permits Agitation failure, 153 Agricir il Ammonia Institute, 563 Agrict. . U.S. Department of, 571 listing of respirators and masks, 378379 Air, 69-70, 373, 426 breathing, 69, 259-265, 373, 394-400, 410 conditioning in laboratories, 272-273 cooled suits, 443 masks, 69-70, 373, 394--395, 426 pollution, 71, 374 supplied respirator, 394-395 see also Breathing apparatus 603 Air Engineering magazine chart from, 598 reference to, 272 Air Pollution Control Association, 563 Air Traffic Conference of America, 563 Aisles, 75-76 Alarms on recording controllers, 141. 142 Alcoholism, 237 Alkylation, 89 Alkyl mercury, 270; see also Diethyl mercury Alkyls, aluminum, 334; see also Alumi num Allergens, 255, 268; see also Chemicals, Skin Allied Chemical Corp., eye protection program, 431 Alpha particles, 352 contaminated dust, 18 Aluminum alkyls, 334 triethyl, 334 trimethvl, 334 triisobutyi, 334 American Association of Industrial Nurses, 563 American Chemical Society, 563-564 American Conference of Governmental Industrial Hygienists, 284-285, 564 threshold limit values, 574-597 American Cyanamid Company, 23-25 American Industrial Hygiene Associa tion, 285, 564 American Institute of Chemical En gineers, 564 American Medical Association, 565 American Nurses' Association, 565 American Petroleum Institute, 335-336, 565 604 Index American Society for Testing and Ma terials, 332-333 American Society of Mechanical En gineers, 155, 565-566 Boiler Code Committee, 157 API-ASME Code for Unfired Pres sure Vessels, 156 Boiler and Unfired Pressure Vessel Code, 156 Code in United States and Canada, status of, 160-162 American Society of Safety Engineers, 538 American Standard Method of Record ing and Measuring Work Injury Experience, 537-545 American Standards Association, 17, 342, 537, 538, 566 American Table of Distances, 568 Amines, 300 Amination by ammonolysis, 87 Annunciators. 144-150 Antifreeze, 270; see also Water as a decontaminant Army, U.S. Department of the, 571 Aromatization and isomerization, 90 Arrhenius equation. 81 Asphyxiants. 380-381; see also Inert gases, Respiratory hazards Association of American Railroads, 566; see also Bureau of Explosives Association of Casualty and Surety Companies, 566 Atmosphere, grinding, 99 see also Inert gases Atmosphere, see Air Atomic energy. 18, 348 see also Radiation Audits, hazard control, 551 Audiometric testing, 440 Automation and computer control, 557, 558. 560 Azides, 301 Barrier creams. 256-257, 268 Baseball caps, 439, see Hats Batch processes. 117 Bathing, 67-68, 76-77; see also Water as decontaminant Behavior, personal, 224-226 Benzol, 231, 244, 277 effect on blood, 244, 277 Beta-naphthylamine, 272 Bicycloheptadiene dibromides, 288 Blood, effect of benzene on, see Benzol effects of radiation on, see Radia tion Blood pressure. 246 Boiler and Pressure Vessel Require ments in Foreign Countries 164173 Bonding and grounding. 342-343 Boric acid, 284 Breathing air. see Air Breathing apparatus, self-contained air purity with, 410 canisters, disposal of. 417-418 demand air or oxygen. 409-410 oxygen generating tvpe. 408. 414418 rebreathing type. 407-408 SCUBA, 381 Breathing, shallow, 403 Bromination and iodination, 88 Bromochloromethane, see Chlorobro- momethane Bump caps. 439, see Hats Bureau of Explosives, 566 Bureau of Mines, U.S., 571 approval schedules for respiratory protective devices, 425, 571 explosives research. 298, 319-329. 571 training service, 421-422 Burning, 478 grounds, 71 see also Fire Cafeteria, 77-78; see also Lunchrooms Calcination, 86 California. 15 Caps, see Hats Cavitation, 103 Canister, disposal of, 417-418 Canister mask, see Breathing appara tus, Masks, Respirators Carbon dioxide as inert gas, 70 effect of temperature, 508-509 fixed-nozzle systems, 507 hand-hose line systems, 507 ETC 03633 Index 60S }on dioxide, in breathing air, 410 irtable fire extinguishers, 506-507 e also Inert gases oon monoxide, 375, 424 arning of spent canister. 389 bon tetrachloride, 274-275, 277, 287 lemical criminal, 277 - fire extinguishers, 509-511 ibstitute for. 287 bonvl compounds, 299 d-gap test, 321; see also Explosives astrophe preparation, 529-536 istic soda, dilution, 427-428 masks, CBR, 391-392 M-17 (Army), 392-393 V-800, 391-392 Centrifugal pump, 104-106 Check points, operating, 54 Chem-Cards, 599; see also Manufactur ing Chemists' Association Chemical composition exposure, diagnosis of, 231 in toxicological evaluation, 280-281 Chemical hazards of the future, 555 Chemical industry, economic importance, 1, 21 employee injury experience, 5, 6, 7, 23 future, 554-562 growth. 8, 21 injury rates, 7, 23 Chemical safety, 251-252 Chemical Safety Data Sheets, see Man ufacturing Chemists' Association Chemical Section, National Safety Council, 10, 298, 570 monthly Safety Newsletter, 570 Chemical and mineral agents, adverse physiological effects, 598 Chemical Specialties Manufacturers Association, 566-567 Chemical hood, proper use of, 265-266 Chlorination, 88 Chlorine Institute, 567 Chlorobromomethane, 509-511 r'"'il Defense, 391-393. 535 thes changing, 76-77, 246, 256 laintenance, 443 ist Guard, U.S., 511, 566 ie, Flammable Liquid, 343 fational Fire, 343 Code, Pressure Vessel, Interpretations, 158 Code interpretations, 158 Combustion. 86, 331-334; see also Fire Community relations, 4, 42-43, 533-534 Company image, 4, 533 Comparisons of safety experience, 551 Compensation. 5, 14. 223, 541 Compounds, safety data on new, 294. 555-556, 563-573 Composition as actually used, 280-281 control by analysis. 127-129 Compressed air or gases, 69, 70, 567 for breathing, 263, 381 Compressed Gas Association, 567 Compressors, location of. 54 Computer control and automation. 557- 558 Condensation reactions, 89 nuclei, 378 Conditions, reaction, 117-119 Conductive shoes, 443, 444, see Shoes Conjugated unsaturated compounds, 299 Contact lenses, 436; sec also Eyes Contributors to safety effort, apprais ing the effects of. 538 Control house location, 54 systems (permits), see Permits see also Temperature control Controller, alarms on recording, 141- 142 displacer-type level. 140-141 pneumatic, 136-137 potentiometer, 137-138 Conveyors, 114 Cooling, vortex tube for, 398-400 Corrosion allowance, 178 and erosion, 113, 125, 479 Cost of accidents, 2-4, 15. 551-553 Crushing and grinding, size separation, 98-99, 112; see also Aerosols Derailments, 55 Dermatitis. 246-247; see also Allergens, Skin and chemicals Detonations, 319-320, 325, 326-327 Diazotization and coupling, 90 Diethyl mercury, 270 Dilution, see Caustic soda ETC 03634 606 Index Disabling injury index, 552; see also Education, safety, role of physiciiuJ Injuries 234-235 ' Disaster planning, 527-536 Dispensary, 48, 223-224, 240 use of slides and recording tan* 234-235 nurse, 240-249 see also Training physician, 228-239 Effective measures, criteria for, 555. Disposal of contaminated equipment, 552 481 Effectiveness, detecting changes in 533 in future, 557-559 Effects of toxic agents. 250-278. 598 see also Permits Efficiency, 2 Distances, American Table of, 568 Einstein. Professor Albert. 11 I Distillation, 112 Dock location, 46, 48 Doctor's cases, 541 Do-it-yourself projects, 433 Double decomposition, 86 Drainage. 113 Drop-weight test, 321 Drum dryers, 102 Dry chemical (fire extinguisher), types of, 499-503 Electrical facilities location. 48. 54 conductivity (in hats). 440 (in shoes). 444 lighting. 63-67 power, 63-66 repairs, 65 Electric sparks, 64-65. 335 Electrolysis. 86 Elevators. 75 bucket, 101 ammonium phosphate base, 502-503 Emergency control, 400-403. 529-536 fixed-nozzle systems, 505 for eye injuries. 434-436. 259 foam compatible, 501 Emergency, maintenance, 481-482 hand-hose line systems, 504-505 procedures. 529-536 portable fire extinguishers, 503 Emotional approach. 287-288 potassium bicarbonate base, 500-501 Endothermic reactions, 118 sodium bicarbonate base, 499-500 Energy of activation. 81 special dry chemical agents, 505-506 Entering vessels, see Vessel entry Dryers, flash, 102 Entry permit. 449-451, 477-478; see also spray, 102 Permits Drying. 102 Epoxy compounds, 299; sec also Der I Ducts, 102 Dust, explosion, 98, 102, 333 explosion suppressors, 84 respirators, 263, 384. 386 toxic, 254, 262. 376-378 see also Aerosols, Respiratory haz ards Ear muffs. 441-142 plugs, 441 Earthquake loadings, 180-182 matitis Equipment, operating permit. 468; set also Permits Equipment location. 44-56. 58-62 Erosion. 113, 125; see also Corrosion Esterification. 87 Ethanol (ethyl alcohol). 333 Ether, diethyl, 333 Evaporation, flash, 102 and crystallization. 103 Excavation permit, 457; see also Per Eating facilities, 77-78; see also Lunch mits rooms Exits. 75-76 Education, safety, 209-218, 219-227, 234- Exothermic reactions, 118-119 235, 558-559, 561 Expanding use of chemicals. 21. 008 first-aid training, 235, 248-249, 274- Experimentation, 290-295 275 role ol nurse, 245-249 Experiences, sharing of. 8. 10. 26-563-573 ETC 03635 Index 607 Explosion, dust, see Dust explosion Fire extinguishing agents, carbon diox suppressors, 84 ide, temperature, effect of, 508,509 Explosives, 319-329, 454 dry chemical, 499, 517 primary, 320 extinguishers, see Fire extinguish research, 319-329, 571 ing equipment tendencies, 293-294 foam compatible, 501 see also Permits multipurpose, 499, 502, 518, 519, 521, Exposures to toxicants, 231, 250-278, 522, 523, 524 555; see also Toxicity potassium bicarbonate, 499, 500, Extinguishing agents, see Fire extin 501, 521, 522, 523 guishers sodium bicarbonate, 499, 501, 517, Extraction, 112-113 522, 523 Eyes, 235, 243, 259, 270, 427-437 special for aluminum alkyls, 512, barriers, 429-431 513, 523 f contact lenses, 436 dry powders for metal fires, 512, 513, damage, 286 523 injuries, 259, 270, 434--436 effectiveness of, 518, 519 neutralizers in, 436 foam, 517, 522, 523, 524 protection, 427^137 chemical, 494 see also Water as decontaminant compatibility with dry chemical, 496 Fabrication, methods of, 197-199 expansion ratio, 495 Face shields, 433; see also Chemicals extinguishers, see Fire fighting and the skin, Eyes equipment Factory Mutuals, 342, 567-568 high expansion, 495 Fail safe, 93, 110, 133-137 light water, 496 Falls, 23, 72-75, 560 mechanical (air), 495 Fatalities, 14, 15, 19, 540, 544, 545 storage temperature, 496 Feed system, 109-110 super high expansion, 495 Fermentation, 90; see also Carbon di temperature, effect of, 494 oxide, Inert gases Halon 1301, bromotrifluoromethane, Filling containers, 428 509, 516, 522, 523 Filtration, 113 inert gases, 515 Fire classification, 485-487 liquids for metal fires, 513, 514 Class A, combustible materials, 485, TMB (trimethoxyboroxine), 514 486, 489, 490, 492, 493, 500, 502, rate of application of, 519 503, 507, 516, 517, 521, 523, 524 steam, 515 Class B, flammable liquids, 486, 489, vaporizing liquids, 509, 517 490, 492, 493, 497, 500, 501, 502, carbon tetrachloride, 509, 522, 523 503, 507, 516, 621, 523, 524 carbon tetrachloride toxicity, 511 Class C, electrical equipment, 487, chlorobromomethane, 509 501, 502, 503, 523 water, 488 Class D, combustible metals, 487, 523 antifreeze, 489 Fire extinguishing agents, approval of, calcium chloride, 489 485 ethylene glycol, 490 bromotrifluoromethane, see Halon lithium chloride, 490 1301 electrical equipment clearance, 493 carbon dioxide, 506, 516, 517, 523 loaded stream, 489, 515, 516, 522, extinguishers, see Fire extinguish 523, 524 ing equipment viscosity additives, 494 E1'c 03 63 6 608 Index Fire extinguishing agents, water, wet water, 490, 516 wetting agents, 491 Fire extinguishing effectiveness comparative effectiveness on class A fires. 520-521 comparative effectiveness on class B fires, 521-523 extinguishers effective on several class fires, 524 factors influencing effectiveness, 518519 methods of evaluating effectiveness, 519 Fire extinguishing equipment, approval of, 485 Factory Mutuals, 485, 500, 567-568 fixed nozzle systems, carbon dioxide, 507 dry chemical, 505 foam, 497 chemical, 497, 498 Moeller tube, 498 rate of application, 493, 516 subsurface application, 498 water-foam sprinklers, 499 water sprinklers, 491, 492 hose lines, hand held, carbon dioxide, 507 dry chemical, 504 foam, 496 chemical, 496 mechanical, 497 water, electrical equipment clear ances, 493 fog, 491, 492, 516 rate of application, 493, 516 straight stream, 492-494 stream effectiveness, 494 portable, carbon dioxide, 506, 522 cartridge, 489, 503 dry chemical, 503 foam, 494, 495, 522 loaded stream, 489-490, 515-516 pressurized, see Stored pressure pump, 489 range, 504 soda-acid, 488 stored pressure, 489, 504 water 488 Fire extinguishing equipment, Un writers' Laboratories, 485, 491, 500, 501, 508, 510, 511, 520, 521, 522. 523, 524, 572-51 Fire extinguishment, mechanism of, chain reaction, 517 cooling, 516 free radicals, 517 particle size, 517.518 surface area, 517 Fire fighting, 344-345 flammable liquid, 330-345 hydrants. 55 permit, 447-448 point, 334-335, 340 triangle, 331, 515-518 Firemen's hats. 439. see Hats Fire Research Abstracts. 342, see > tional Academy of Sciences First-aid cases, 541 training, 234-235. 248-249 Flammability, 330-345 Flammable area work permit, 464 gas and vapor detection, 340 limits. 336-339 liquids code, 343 materials, 43. 44, 330-346 range, 336-339 see also Permits Flash point, 340 Flooding, 49 Flow sheet, 109-116 Fluorination, 88 Foam, 494-499; see also Fire extii guishing agents, Fire extinguisl ing equipment Food, see Lunchrooms Foreman, in eye protection program, 43 in training. 209-215, 219-226 overzealous, 18 Frequency and severity, 543-545 rates, 5-7, 23, 543 Friction sparks, 335 Fulminates, 300 Fume offs, 84 Fumes, 273, 378; see also Aerosol* Respiratory hazards Furnaces, 54 Future of chemical safety. 554-562 legislation, 559 ETC 03 63 7 Future of chemical safety, of eye pro tection, 434. process plant location, 557 process plant problems, 556-557 Gage glass location, 430 Gantry cranes location, 50-51 Gases and vapors, 231, 251-266, 379-380 detection of flammable, 340-341 detection of toxic, 375 Gases, inert, see Inert gases Gas masks, 69-70, 388-393 dust, 263, 378, 383-384 V-800, 391-392 see also Respiratory hazards Gas with gas mixing, see Mixing gas with gas Glass, gage, see gage glass Gloves, 268, 443 aprons and specialized clothing, 442443 Goggles, 26, 432-433 areas, 432 see also Eyes Grounding and bonding, 342-343 Guard rails, 73 Guide for Safety in the Chemical Lab oratory, 568 Half-life, see Radioactive Halogenation, 88 Halon 1301, 509, 516, 517 Hand injuries, 560 tools, 482 Hats, baseball, 439 bump, 439 firemen's, 439 insulating, 440 nonconductive, 440 Hazard, 36-37, 39, 279, 373-426, 559 identification, 38-39, 280-281, 599-602 special, 465 see also Respiratory hazards Hazardous reactions, 298-302 work area, 456--465 see also Permits Headgear, see Ear muffs, Hats, Hoods Head protection, 439--440; see also Hats Health, Education, and Welfare, U.S. Department of, 571-572 Index 609 Health evaluation plan, 245 interview, 245-246 Hearing loss, 440 Heat of dilution, 427-428 Heat transfer, 94-98 surface, distribution of, 111 Helmets, air supplied, 395 built-in muffs, 441 see also Hats High-explosives building work permit, see Explosives, Permits High-pressure vessels. 204-205 see also Pressure vessels Hoods, air supplied, 395-398 Hood, chemical fume, 265-266 design, 430 full, 430-433 Hopcalite, 385 Hot spots, 80-81, 94-95, 111 work. 447-448; see also Permits Housekeeping, 72 Human aspect, 4, 25 error, 224-226 factor in safety and loss prevention, 11, 25 see also Infraction Humidification, 102 Hydrazine, 335 Hydrogenation and hvdrogenolysis, 89 Hydrogen cyanide, 273 Hydrogen peroxide, 334, 335 Hydrogen sulfide, 242, 275-276 Hydrolysis, 88 Hygienic Guides, 564. see American In dustrial Hygiene Association Identification of contents, 599-602; see also Composition Ignition energy, 335 source, 334-335 temperature, 334 Illuminating Engineering Society, 66 Illumination, 66, 67 Incident, severest credible, 93 Incompatible chemicals, 298, 301, 335 Indoor facilities, 55 Ionization-sensitive probe, 324-325 Indifference to safety, 11 Industrial commissions, see State in dustrial commissions ETC. 0338 610 Index Industrial Hygiene Foundation, 568 Industrial nurse, 240-249 in safety counseling, 230, 245-248 see also American Association of In dustrial Nurses, American Nurses' Association Industrial physician, relationship with nurse, 240-241 relationship with safety engineer, 223, 229 Inert gases, 261, 262-263, 271, 334, 381. 404-405 Information sources, 563-573 Infractions, 224; see also Human as pects, Human error Injuries. 540-541 accidents without, 230, 553 common denominator in disabling, 5-8, 14-20, 229-231, 235, 540 hand,560 Injury experience, method-of recording and measuring, 537-553 In-line equipment arrangement, 50-51 Inspection and testing of pressure ves sels, 199 of tools, 482, 483 Installation of pressure vessels, 202203 Institute of Makers of Explosives, 568 Instruction principles, 211 Instruction, vestibule, 210 Instructional aids, 213-215, 234. 235 Insulating hats, 440; see also Hats Insurance, 2, 3, 541; see also Workmen's Compensation Interdisciplinary research, 559 Interest in safety, 10 Interior, U.S. Department of the, 571 Interlocks, 150-154 International Brotherhood of Pulp, Sulphite and Paper Mill Work ers, 19; see also Unions Interstate Commerce Commission, 342, 599; see also Bureau of Ex plosives Irritants, 261 Isotopes, 350-351; see also Radioactive Joint labor-management safetv 19-20 safety program, 19-20 ort' Kipp generator (for hydrogen sulfide) 265,275 ' Laboratory, 45, 265-266, 272-273 27t_ 277, 390, 429-430 ' hood abuse, 265-266. 429-430 Labor. U.S. Department of. 572 Labor Conference, National Safety Council, 16 Labor officials' part in chemical safety 32-33 _" " Ladders, maintenance of, 72-75 Legal aspects, 4. 5, 559 Legislation in future, 559 Lenses, corrective, 431-132 with gas mask facepieces, 388 contact, see Contact lenses see also Eyes, Goggles Level gages, 430 Life, human, 4,9. 11. 13, 15. 555 unnecessary sacrifice of, 402-403 Lighter permit, 467; see also Permits Lighting, 66, 67 Line breaking, 450--453 Liquid, air, in suits. 400-401 -liquid mixing, 100 -solid mixing. 100 Line breaking permit, 453; see also Permits Lines of organization, see Organization Loading, facilities, location of, 46 due to weight, wind, earthquake, 179-182 Locking and tagging, 480-481 Looped systems, water and steam lines, 47-48 Loss of hearing, see Hearing loss Lost time injuries, see Injuries, dis abling Low-order detonations, sec Detonations Low-velocity detonations, see Detona tions Lunchrooms, 77-78 Job breakdown, 211, 212 Job instructor training, 210-212 Maintenance, 472--484 emergency, 481-482 Maintenance, equipment, inspection of, 483 facilities location, 46 of breathing apparatus. 420-421 of hoisting equipment, 483 of ladders, 72-75, 483 of ropes and slings, 483 scheduling, 474^175 Man. 9, 25 Management, prerogatives of, 20 responsibility and accountability, 9-10 responsibility for disaster control, 527-528 Manuals, safety, 219-220 Manufacturing Chemists' Association. 10. 22, 26, 27, 285, 298, 342, 568, 599 Chem-Cards, 342, 599 Chemical Safety Data Sheets, 599 contributions to safety, 26-28, 599 Safety Guides, 599 Masks, gas, see Gas masks Masks, CBR, 391-392 M-17 (Army), 393 canister, 69-70, 270, 388-390 see also Breathing apparatus, Respi rators Mass transfer, 101 Matches and lighter, 467; see also Per mits Materials handling, 100-101; see also Permits Maximal acceptable concentration, 374 Material, selection of, 177-178 specification, 177-179 Measurement of radiation, see Radia tion Mechanical pipe joints, 126 Mechanical stability tests, 312-316, 319-329 impact sensitivity, drop-weight tester, 312-313 shock sensitivity, card-gap tester, 313-314 Medical control, 231-233 of users of respiratory protective de vices, 423-424 Medical treatment cases, 231-233, 541 Meetings, material for, 213-214, 234235, 274-275 Index 611 Meetings, see also Education, Training Mental illness, association with occu pational injury,237 association with safety, 237 Metal fires, approved agents, 512 dry chemical for, 512-515 unapproved agents, 513-515 Methanol (methyl alcohol), 270, 332 Mists and sprays, 378; see also Aero sols, Respiratory hazards Mixing gas with gas, 99 gas with liquid. 99-100 gas with solid, 99 liquid with liquid. 100 liquid with solid, 100 solid with solid, 100 Models, use of. 40-41, 214 Modern standard method of apprais ing safety effectiveness, 551-552 Monitoring, 18, 127-129, 356-357, 359- 361 continuous, 560 Morale, 4 Motivating accelerated performance, 538 Moving pipe seals, 126 Muffs, ear, 442; see also Ear muffs Naphthalene, 332 National Academy of Sciences, Fire Research Abstracts, 342 National Board of Boiler and Pressure Vessel Inspectors, 156-159 National Board of Fire Underwriters, 298, 342, 569-570 National Electrical Code, 343 National Fire Protection Association, 342. 343, 569-570, 599-602 National Plant Food Institute, 570 National Safety Council, 5, 6, 10, 285, 570 National Safety News, 570 Navy, U.S., 10 Neighboring plants, 42-43 Neutralization, 86; see also Water as decontaminant New disciplines, 559 Nitration, 87, 251, 273,302 Nitrators, 87 Nitriles, 301 E'!'C 03 6 4 0 612 Index Nitro compounds, 301 Nitrogen, 70; see also Inert gases Nitrogen containing compounds, 300- 301 Nitrogen oxides, 115, 251, 261, 273. 274, 276. 379. 403 Nitroglycerin. 269, 271 Noise control, 440-442 Nonconductive hats. 440; .see also Hats Nurse, see Industrial nurse Occupational disease, definition, 539 treatment of. 229-231 Occupational health, 228-239, 240-249 noise, 440-441 Occupational Health Information Ex change. 572 Occupational Health Nursing Commit tee. see National Safety Council Occupational injuries, treatment of, 229-230, 243 Occupational medical program, 228-239 chart of, 228 Office location, 45 Oil, Chemical and Atomic Workers In ternational Union, 14-20 On-the-job training, see Training pro cedures Operating errors, prevention of, 151-153 procedures, standard, 445 Operation, break-down sheet, 216-217 Operational process and flow sheets, 216 Order of the reaction, see Reactions Organization, lines of, 226 Outlet system, 111-112 Oxidation, 86; see also Combustion, Fire Oxides of nitrogen, see Nitrogen oxides Oximes. 301 Oxygen, administration equipment, 247 balance, 294, 301 concentration, 339-340 deficiency, 262-263, 404--405 Pacific Coast Association of Pulp and Paper Manufacturers, 19; see also Unions Packing glands, 105 Parking lots, 78-79, 542 Pathways, 78-79 Penicillin G, 280 Pentane. 336-338 Permits, acid area work, 461 after hours operations, 458 disposal operations, 455 entry (vessels or closed spaces) 449451, 477-478 equipment operating, 468 excavation, 457 explosives building work. 459 explosives testing. 454 flammables area work, 464 hazardous operation, 447 hot work. 448, 451 line breaking, 453 match or lighter, 467 sprinkler valve closing, 469 toxic materials. 466 vehicle operating. 468 Personal factors, 560 protective equipment, 438-444 Phase separations, 106 Philosophy of life, 12 Phosgene. 261, 403 Physicians, 223-224, 229, 240-243 -nurse relationship, 240-241 Physical conditions, unsafe. 225 Physical examinations, assistance by safety engineer, 234 statistical evaluation, 234 Physiological effects upon man chart, 598 see also Effects of toxic agents, Tox icity Pictures, use of, 213-214, 234-235 Pin-hole leaks, in gloves, etc., 443 Pipe racks, 428 Piping. 113-114 Pittsburgh survey, 14 Plant layout, 43-49 Plastics Engineering Handbook, 570 Plastics Safety Handbook, 571 Plate thickness, minimum, 176-177 Platforms, 72-75 Plosophores, 293-294; see also Explo sives Plug cock hazard, 431 Pneumoconiosis, 262, 377; see also Re spiratory hazards, Respiratory tract Index 613 Poison Control Centers, 284, 569 Pyrolysis (cracking), 90 Poisons, 287; see also Toxicity, Toxic materials Quenching the reaction, 97-98; see also Polymerization, 89-90, 112 Reactions, Reactor. Port of New York Authority, 342 Powder shoes, 443, 444, see Shoes Radiation, biological effects, 361-365 Power, electric, 63-66 blood cells, 362-364 Pre-employment physical examinations, cell sensitivity, 362 231-232, 560-561 organs affected by isotopes, 364- communications regarding, 233 365 Pressure and temperature, 176 RBE, 355-356 Pressure containment, 125-127, 155-208 R.F., 347-348 Pressure relief devices. 76,127 control, 365-367 Pressure-sensitive probe, 324-325 distance. 366 Pressure vessels and piping, 125-127 pits, 367 Pressure vessels, and boiler require shielding, 366-367 ments in foreign countries, 164- shielding materials, 367 173 time, 365-366 design of, 155-208 exposure limits, external, 369 high, 204-205 internal, 369 repairs to, 203 nonoccupational, 369 testing and inspection, 76. 155-208, ionizing, 347-350 479 alpha, 18, 352-353 or vacuum, 177 beta, 353 Prevailing wind, see Wind, prevailing electrons, 353 Preventive maintenance, 473-474 gamma (or X-), 353-354 Primary explosives, see Explosives neutrons, 354 Procedures, control and standard op measurement, alpha detectors, 361 erating, 445-471 chemical dosimeters, 360 Process, designing safety into, 24-25 dosimeters, 359-360 Process design, 108-130 film badges, 357-358 Processes, continuous, 116-117 Geiger-Mueller counters, 360-361 batch, 117 ionization chambers, 358-360 Production supervisor, 17 reasons for, 356-357 Product liability, 558-559 scintillation counter, 361 Protective clothing, 18, 256-258, 438- nonionizing 444 lasers, 347 see also Respiratory protection, Toxic light, 347 1 agents P=v- hological counseling, association R.F., 347-348 sources. 350-351 with accident proneness, 237-239 units, curie, 354 evaluation with back X-rays, 233 LET, 356 need in safety program, 237 rad, 355 Public Health Service, see Health, Ed RBE, 355-356 ucation and Welfare rem, 355-356 Public relations, 4, 28-34, 531-536 roentgen, 355 Pumps, centrifugal, 104-106 Radioactive, 18, 347-372 compressors, agitators, 103-106 half-life, 352 positive displacement, 104-106 isotopes, 350-352 start-up, 103-106 see also Radiation ETc- 03 64 2 614 Index Radionuclides, see Isotopes Railroad location, 46, 55 Ramps, 73 see also Ladders, Stairways Rate constants, 81, 84 Reactants, safety data on, 291-293 Reaction, auto-catalytic, 84 kinetics, 81-83 order of the, 81 rates, 82-83, 85 Reactions, endothermic, 118 exothermic, 118-119 quenching the, 97-98 runaway, 94-98 unknown, 291-293 Reactive chemicals acetylenic compounds, 300 amines, 300 azides, 301 carbonyl compounds, 299 conjugated unsaturated compounds, 299 diazo compounds, 300 epoxy compounds, 299 fulminates, 300 nitriles, 301 nitro compounds, 301 nitrogen-containing compounds, 300- 301 oximes, 301 vinyl compounds, 299 water-reactive compounds, 300 Reactor location, 54 parametrically sensitive reactors, 96 radial temperature within, 95 types, boiling liquid-cooled tubular, 123-124 direct-fired kettle, 119-122 direct-fired process heater, 121-122 steam-heated tubular reactor, 122- 123 Recorders, alarms on multipoint, 141-- 142 Reduction, 87 Regulator, self-acting pressure, 133-134 self-acting temperature, 134-135 Rehabilitation, impact on safety pro gram, 236 role of the safety engineer in, 235 table of suggested approach, 236 Relief devices, 127 Repairs to pressure vessels, 203 Reporting injuries and illnesses, 223 Rescue kit, 248 Research for safety in depth, 237, 556 Respirators, aerosol filters, 384 air-purifying, 384 air-supplied, 393-394 ammonia, 386 chemical cartridge, 384-385 continuous flow. 394 demand-type. 394 half-mask, 386 hose mask, 394 mercury, 386 see also Breathing apparatus, Gas masks Respiratory hazards, 231, 251-266. 373- 426,598 protection (chart). 383 tract, 231-232, 243, 254-255, 259-264, 379-380 see also Threshold limit values Responsibility, basic rule of, 10 see also Management Road and pathway lighting, 79 Roadway location, 47, 78, 79 Rule books, 214-215 Rupture discs, 127, 128 Safety, boots, 443 committees, 16-17, 39 definition, 2 engineer, 17 relationship with industrial phy sician, 229 evaluation, 556 glasses, fitting of, 434 goggles, 18, 431 hats, 439-440 orientation and job training, 209227, 560 parameters, 556 policy and program, 16-17 program, disruption of, 226 sheet describing chemicals, 217-218, 244,563-573 shoes, 443--444 showers and eye wash fountains, 6768, 434-436 ETC 03K43 index 615 Safety, showers and eye wash fountains, drills, 435-436 freezing protection, 435 marking, 435 testing, 435 valves in lines, 435 standards, 221-222 operating procedures, 216-226 vaccine, 560 Scale accumulations, 103 Scale models, see Models, use of SCUBA, 381; see also Air, Breathing apparatus Seals, pipe, moving, 126 Second-hand equipment', 203 Seismic map, 181 Selection chart for respiratory protec tive devices, 383 Self-interests, 12 Self-preservation, 11 Separation by barrier, 38, 55 by distance, 38 see also American Table of Distances Service gases 70; see also Compressed air or gases, Inert gases, Piping Severity, 562 rate. 6, 7, 23, 543-546, 562 average. 548 Sewage, 46. 71-72, 559; see also Waste disposal Sharing of experiences, see Experi ences, sharing of Shoes, 256, 443-444 acid-oil shoes, 444 conductive shoes, 443-444 income-tax deduction, 444 powder shoes, 443-444 safety shoes, 443 shoemobile, 444 Showers, 67-68, 246, 256-257; see also Water as decontaminant Site selection, 36-43 Size reduction, 98-99 Skin and chemicals, 246-247, 255-256, 269-270; see also Dermatitis, Water as decontammant Slides, use of, 213-214, 234-235 Smoke bombs, 423 Smoking, 45, 222-223 areas for, 222 Smoking, identification of prohibited areas, 222-223 Society of the Plastics Industrv, 570571 Solids in pipelines, 106 Solid-solid mixing, see Mixing Solubility, 254, 257, 261-263 Solvents, 18-19, 598, 599-602 Solid streams, 493-494 Sparks, electric, 335 friction, 336 Special hazard permits, 465-470; see also Permits Speech transmission, amplifiers, 419 telephones and radio, 419 while wearing breathing apparatus, 418419 Sprinkler systems, 491^193; see also Fire extinguishment. Water reac tive compounds Sprinkler-valve closing. 469--470 Standardization in safety glasses, 434 Stability data sources, 301, 563-573 Stairways. 72-75; see also Falls Standard animal, 280 man. 280 Standard rates, significance, 546-547 Start-up and shut-down routine, 218 State industrial commissions, 14; see also Workmen's Compensation Static sparks, 335-336 Statistics, 7, 11, 23, 537-553 Steam, 70-71, 515 Steel safety cap, see Shoes Storage. 47, 49, 59, 114-116 gas, 116 hot materials, 98 liquid, 115 solid, 114-115 Suits, air supplied, 395-400 liquid air cooled, 400-401, 443 vortex tube cooled, 398-400 ventilated, 443 Sulfonation, 88 Summer schools, 16 Supervisors safety book, 220 instructions for, 220-221 Supports, vertical vessel heads and closures, 182 Switches, float, 138-139 ETC 03644 616 Index Systems, control, 132-154 permit, 445-470 Tank entry, 449-450, 477--178; .see also Permits Tankage location, 44-47, 115 Tear gas, 379; see also Respiratory hazards Temperature control, 111 gradients, radial, 80-81 high effects, 111 low effects. Ill and pressure, 176 Testing and inspection of pressure ves sels, see Pressure vessels Testing operations. 454; see also Per mits Tetraethyl lead, 269-270 Thermal stability tests, Dewar-flask thermal stability, 307-310 hot-coil thermal stability, 311-312 pressure tube test, 311 pretest, 303 simple thermal stability test, 303-304 thermal stability test bomb, 311 Threshold limit values, 284-285, 375, 574-597 Titanium tetrachloride, 269 TXT 272, 294; see also Explosives, Nitro compounds Total emergency planning, 529-536 Topography, 38. 41--12, 49 Toxic gases and particulates, 406--107 and vapors, 405-406 see also Air, Respiratory hazards Toxicity, in animals, 282 classification, 286 day-bv-day exposures, 284 definition, 279 dose, 282 in humans, 282 other influences, 282 rate of absorption, 281 site of injection, 281-282 units of dose. 282 see also Effects of toxic agents, Toxic materials Toxic materials, 18, 36, 38, 44, 250-27S, 279-289, 466, 598; see also Per mits, Threshold limit values Traffic, 42. 47, 52, 53. 78, 79 Training, procedures, 209-227 in first-aid. 235, 248-249 and follow-up, 215 on-the-job, 210, 212-213 personnel, 209-215, 234-235 Transportation of chemicals, 28-30 accidents at delivery points, 32 emergency procedures for accident-- 30-31 in future. 557 identification of contents, 599-602 Trichloroethane,1.1,1- (methyl chloro form). 287, 382 Trichloroethylene, 382 Type X universal gas mask, 389-390 see also Breathing apparatus. Gas masks Underwriters' Laboratory, 342, 572573 Unions, 14-20 Union safety and occupational health committees, recommendations for, 16-17 L'nit operations, 92-106 Units of radiation, see Radiation United Papermakers and Papenvorkers International Union, 19 L'niversal canister mask. 389-390 limitations of use, 390 misleading term, 390 see also Breathing apparatus, Gas masks Unknown reactions, 291-293 Unsafe acts, correction of, see Acts Valves, solenoid, 143-144 relief, 127 Valving, 113 \raporizing liquids, 509-511 portable fire extinguishers, 510 sprinkler units, 511 types. 509 see also Carbon tetrachloride, Chlo- robromomethane, Fire extin guishment Vehicles operating permit, sec Permit; Ventilation, 70, 263-264, 272-273; mi also Threshold limit values Index 617 Ventilated suits, 443 Vents, 102; see also Pressure relief de vices Vessel certification, 199-200; see also Pressure vessels Vessel entry. 449-450, 477-478 rescue kit, 248 see also Breathing apparatus, Per- ' mits. Respiratory hazards Vessel tolerances, 199-201 Vinyl compounds, 299 Vital record protection, 529 Voids entry, 449-450, 477-478; see also Permits Volatility. 332-333 Vortex tube, 398-400 Walking, 78-79 Walsh-Healy Public Contract Act, 5 Warning labels, see Identification of contents Washing, 67-68, 246, 256-257; see also Water as decontaminant Waste disposal, 4-5, 42, 46, 71-72, 559 Water as decontaminant, 243, 246, 256258, 268-269, 434-435 Water reactive compounds, 300 Water spray (fog), 491-493 fixed-nozzle systems. 491 hand-hose lines, 491 .see also Fire extinguishing agents Water-treating facilities location, 42 Welding, 336, 447-448, 478--479 Wind, prevailing, 38 Workmen's Compensation, 5, 246-247, 541 hearings, 14 ETC 03646 s g f? - tr> - S C, r* X Z* <y S2a> a -* 25 - fx. ETC 03647