Document M41NOBMZ14xej0bXRjV6Gzmjj

FILE NAME: Oil Industry and American Petroleum Institute (API) DATE: 1937 July DOC#: API155 DOCUMENT DESCRIPTION: Report Excerpt - Dust Producing Operations in the Production of Petroleum Products and Associated Activities :'v^s^,ri-Trr; i':hr*bl'*'."-.'>; y*r.,5'/.'!."'v**-..j:.`- y: -:. >:>V - j ; . " . T cr " -n-i- .- - t.,5 B U U LtTiN u * 9 s jP i.iC A r c = o p u o l u h c : w it h o u t w o rrrtN p u :J 5 .on ' . ... . - 'f MEDICO - SAFETY MEMORANDUM d u st producing o perations in th e pro du ctio n of petroleum pro d u cts A N D ASSOCIATED ACTIVITIES CONTENTS PAGE INTRODUCTION PART I - DUST AS A HEALTH HAZARD ` t X - WET IS THE DUST PROBLEM SO IMPORTANT?............................ . II - WHAT IS MEANT B "DUST"?............................................ III - WHAT ARE THE PHYSIOLOGICAL EFFECTS PRODUCED BY The Inhalation of Dust........ Silicosis in General............. ' First National Silicosis Conference....... Silicatosis............ " Asbestosi6.................................................... IV - WHAT IS THE MAXIMUM PEHMISSABLE DUST CONCENTRATION? Formula For Determining Mjdmum Permissible Concentration of Silica in The Air Breathed....... ............... ............ Safe Dust Concentrations, Impringer Samples...................... V - HOW MAY THE CONCENTRATION ANDCHARACTER OF INDUSTRIAL DUSTS BE DETERMINED?................................................ The Impinger Apparatus.......................................... The Zeiss Konimeter.............................................. The Bausch & Lamb Dust Counter............ .................... .. PART II - DUST PRODUCING OPERATIONS STUDIED ' WHAT ARE THE PRINCIPAL DUST PRODUCING OPERATIONS? ,, 2 2 3 4 4 5 7 7, 8 9 9 10,11 11 11 I - SAND-BLASTING........................................................ 13-15 n - FILTERING OPERATIONS................................................. 15-27 A - Filter Clay or Fullers Earth? What is Filter Clay or Fullers Earth?........................ How is Filter Clay Mined and Prepared?........................ How is Filter Clay Used?..................................... "Burning" Clay............................................ Charging Filters.......... Dumping Filters............. Composition of Filter House Air Borne Bust...... ............ Control of Filter Clay Dust................ ...... ........... 15,16 16,17 17,18 18,19 19,20 20,21 21 22 B - Contact Clay? Main Constituents ofContact Clays............................ What is "Filtrol" and How is it Produced?.................... What is the Chemical Composition of Filtrol?......... ....... How is Contact Clay Used?. .. 22,23 23,24 24,25 -2- PAGE C - Done Black or Charred Bone; How is Bone Black Used....................................... . 26 III - INSULATING OPERATIONS; A - What Physiological Reactions are Provoked by ' Insulating Materials?.................... ................ . 27 B - What Are The Principal Insulating Operations and How Much Dust is Produced During Such Operations?........... 27 . Insulating 12" Steam Lines................................ 27,28 Insulating a 750-Pound Cracking Coil Accumulator......... 28 Insulating Treating Plant Acid Suction Line...... ........ 28 Insulating Cracking Coil Hot Oil Lines.................... 28 Dismantling or Removing Old Insulation.................... 28,29 Crushing Scrap Asbestos...... ................. ........ . 29 Crushing Old Cork Insulation.............................. 29 IV - GUNITING OPERATIONS; What Is Gunite and How Is It Applied?........................ 29,30 . Removal of Gunite Lingins.............. .'............... ..... 30 V - WELDING AND CUTTING OPERATIONS; A - Welding Operations; 1. Electrio Arc Welding............ ...... .................. 30 What are Coated Electrodes?............................ 30,31 What do These Electrodes Contain and What ^ Products Result Pram Their Use?..................... . 31,32 What is The Amount and What Are the ' Characteristics of Fumes or Dust Produced By The Various Electric Arc Welding Operations...... 32-35 What Physiological Effects on Welders is i Produced by The Use of Coated Electrodes............. 35-37 2. Oxy-Acetylene Welding.................................... 37 Fumes or Dust Produced by Oxy-Ac etylene Welding........ 37 B - Burning or Cutting Operations: 1. With Oxy-Acetylene....................................... Fumes or Dust Produced by Oucy-Acetylene Burning......... 2. With Natural Gas.......................................... 37,38 38 38,,. C - Health Hazards Produced by Welding and Cutting Operations.. . 38 VI - GRINDING OPERATIONS: What is The Composition of Grinding Wheels?.................. Is Abrasive Dust Harmful?............. ....................... 39 39,40 1 - What are the More Frequently Used Types of Grinders. the Quantity and character of the Dust they Produce?.' 40 -2- PAGE C - Done Black or Charred Bone: How is Bone Black Used.............. ............ . 26 _ INSULATING OPERATIONSt A What Physiological Reactions are Provoked by ~ Insulating Materials?.................. ..................... 27 B - What Are The Principal Insulating Operations and How Much Dust is Produced During Such Operations?.......... 27 . Insulating 12" Steam Lines................................ 27,28 Insulating a 750-Pound Cracking Coil Accumulator........... 28 Insulating Treating Plant Acid Suction Line.... .......... *' 28 Insulating Cracking Ceil Hot Oil Lines.................... 28 Dismantling or Removing Old Insulation............. . 28,29 Crushing Scrap Asbestos............. ................ . 29 Crushing Old Cork Insulation.............................. 29 - GUNITING OPERATIONS; What Is Gunite and How Is It Applied?................... . Removal cf Gunite Lingins............................... . 29,30 30 ~ WETDING AND CUTTING OPERATIONS; A - Welding Operations; 1. Electric Arc Welding..................................... 30 What are Coated Electrodes?................. . 30,31 What do These Electrodes Contain and What Products Result From Their Use?..................... 31,32 What is The Amount and What Are the . ' Characteristics of Fumes cr Dust Produced By The Various Electric Arc Welding Operations...... 32-35 What Physiological Effects on Welders is Produced by The Use cf Coated Electrodes............ 35-37 2. Oay-Acetylene Welding. ................................ 37 Fumes or Dust Produced by Oxy-Acetylene Welding....... 37 B - Burning or Cutting Operations; 1. With Oxy-Acetylene........................... ........ . Fumes or Dust Produced by Oay-Acetylene Burning......... 2. With Natural Gas......................................... 37,38 _ 38 38 C - Health Hazards Produced by Welding and Cutting Onerations.... 38 RINDING OPERATIONS ' What is The Composition of Grinding Wheels?.................. Is Abrasive Dust Harmful?.................................... 1 - What are the Mere Frequently Used Types of Grinders. the Quantity and Character of the Dust thev n--J- * 39 39,40 -3- PAGE A - TANDEM FLOOR TOOL GRINDERS................................... Dust Produoed by Tandem Floor Grinders...................... 40,41 41,42 B - TANDEM BENCH GRINDERS........................................ 41 Dust Produced by Tandem Bench Grinders...................... 41 Characteristics of Dust Produoed by Tandem Benoh Grinders............................. ......... ...... 42 C - SINGLE FLOOR TOOL GRINDERS.................... !.............. 43 Dust Produced by Single Floor Grinders................... 43 Characteristics of Dust Produoed............................ 43 D - UNIVERSAL GRINDERS........................................... Dust Produced By Universal Grinders......................... Charaotersitics of Dust Produced....................... . 44,45 44 45 E - SURFACE GRINDERS............................................. 45 Dust Produoed by Surfaoe Grinders......................... . 45 F - LANDIS TOOL GRINDERS....................................... 45,46 Dust Produced by Landis Tool Grinders....... ............... 45 G - YANKEE DRILL GRINDER......................................... 46 Dust Produoed by.Yankee Drill Grinder....................... 46 H - AUTOMATIC CIRCULAR SAW SHARPENING MACHINE.................... 46 Dust Produoed by Yankee Drill Grinder............ .......... 46 I - AUTOMATIC BAND SAW GRINDER............... ................... Dust Produoed by Automatic Band Saw Grinder................. 46,4747 J - AUTOMATIC BAND SAW LAP GRINDER............................... 47 Dust Produoed by Lap Grinder................................ 47 K - PLANING KNIFE BLADE GRINDER......... ......................... if Dust Produoed by Blade Grinder........................ ...... 47 L - LINDERMAN CUTTER GRINDER................................. . 47 Bust Produoed by Cutter Grinder................ ............ 47 M - GANG SAW BLADE GRINDER....................................... 47 Dust Produoed by Gang Saw Blade Grinder.................. 47 N - EDGER SAW GRINDER............................................ 47 Dust Produced by Edger Saw Grinder.......................... 47 0 - CIRCULAR SLAB CUT-OFF SAW GRINDER............................ Dus-fc Produod by Cut-Off Saw Grinder........................ P - "HOG KNIFE" GRINDER.......................................... Dust Produced by "Hog Knife" Grinder........................ 47,48 48 48 48 Q - CUTTER GRINDER,.............................................. 48 Dust Produced by Cutter Grinder............................. 48 Control of Dust from Grinding Wheels........................... 4B HANDLING POWDERED OR PULVERIZED MATERIALS: A - LIME: (1) Hydrated Lime............. ............ .................. (2) Lump Quick Lime..... ................. ................ . What Physiological Effect is Produced by Lime Dust........ . 49,50 50,51 51 B - METALLIC ZINC DUST: Typical Screen Analysis...................... . 51 Dust Produced........................................ ......... 51 What Physiological Effect is Produced by Zinc Dust;.......... 51 C - ASBESTOS "FLOAT": ' Dust Produced.... ...... . .Physiological Effect of Asbestos Particles........... 51,52 52 D - GROUND MICA: Dust Produced................................................. 52 Physiological Effect of Mica Dust.................. .*........ . 52 E - SULPHUR: (1) Sulphur Flour................ ........ ............... . (2) Crude Sulphur............. ........... ................... Physiological Effect of Sulphur............ .............. . 52 52,53 53 T - LITHARGE: Dust Produced..... ................ Necessary Precautionary Measures When Handling Litharge.... ........... ................ ........ .. 53 5^,54 G SODA ASH: : Dust Produced............ ........ .............. ............. . 54,55 H - TALC or "SOAPSTONE": .. . Dust Prodmed..... .............. .......... ............. . Physiological Effects Produced by Talo Dust.................. ; 55 55 I - GRAPHITE: . Dust Produc ed......... ..................... ............ . J - SLATE FLOUR: ' Dust Produced.................................... Effect of Slate Flour on the Lungs........................... 55,56 56 57 I - GRINDING DERRIS ROOT: ' Dust Produced................ 57 To What Extent is Derris Toxio?......... ................ . 57 L - GRINDING PfRETHRUM FLOWERS: Dust Produced...... .................... 57,53 M - MIXING AND PACKING "FLIT" POWDER: Dust Produced.......... `'fl amm -5- iliiM UaijiiHM HI NING TUBES AND DRUMS : 4 CRACKING COIL SOAKING DRUMS Duet Pr.oduc ed..... .............................. CRACKING COIL TUBES: Dust Produced...... ............................ I WATER HEADERS AND BOILER TUBES: Dust Produced.................................... Composition of Dust from Front Water Wall Header, FOOT DRY OPERATIONS: 'Aiv .* k; J A - POURING MOLTEN METAL INTO SAND MOULDS..., B - "SHAKING OUT" CASTINGS................. . U - CLEANING CASTINGS: (a) Preliminary Cleaning............. . (b) Tumblast........................... (o) Sly Tumbling Mill................. . (d) Tumbling Barrels................. . (e) Air-Blasting....................... (f) Rough Snagging Wheels............ . (g) Pine Snagging and Polishing Wheels, (h) Cone Grinding Wheels............ .. Average Dustiness of Cleaning Room Air, D - CORE MAKING............................. . E - SEPARATION OF BRASS FOUNDRY SKIMMINGS___ - MASON*S OPERATIONS: I . II J HI IY ';| Y ..l VI - TEARING OUT STILL FIRE BOXES..... . - CHIPPING OR CUTTING CONCRETE...... - CHIPPING MORTAR FROM BETWEEN BRICK, - CRUSHING FIRE BRICK.............. . - SHAPING FIRE BRICK ON EMERY WHEEL., - *"DISMANTLING MASONRY.............. . TI J i WOODWORKING OPERATIONS: A - BOX SHOOK MANUFACTURE (a) Resawing...................................... (b) Ripsawing..................................... (o) Cut of Sawing................................. (d) Planing....................................... Dustiness of Shoot-Factory Air.................... B - BELT SANDERS, SAND DISCS AND SPINDLES OR CYLINDERS: (a) Belt S a n d e r s . .............................. (b) Sand Discs or Wheels............... ......... . (c) Sand Spindles or Cylinders.................... 1 C - MAKING WOODEN CRATES: (a) Band Saws..................................... (b) Railroad Saws.................................. i PAGE 56,59 59 59 60 60,61 61 61 61,62 62 62 62,63 63 63,64 64 64 64,65 65 65 65 65,66 66 66 66 67 67 67 6^,68 68 68 66.69 69.70 70 70 -6- PAGE ROCK EXCAVATION; A - DRILLING................................................... B - BLASTING................................................... C - M U C K I N G . . ...................................V.............. D - DUST CONTROL MEASURES: (a) Wot Drilling and Wetting Down Rock Walls and Muck Piles.......................................... (b) General Ventilation.................................. (c) Dust Exhaust Hoods on Drills and Other Mucking Operations and LocalSources of Dust............... (d) Personal Protection by Means of Respirators and Positive - Pressure Masks........................ 70 71 71 71 71 71,72 72 PART III - MEASURES FOR REDUCTION OF THE DUST HAZARD HOW CAN THE DUST HAZARD BE REDUCED? --q , j . '. , 1 A - DESIGN PLANT FOR DUST CONTROL...................... 74 B - PROVIDE BUILDING VENTILATION....................... 74 C - STORE DUSTY MATERIALS IN DUST-TIGHT BINS................ 74 D - ENCLOSE MATERIAL HANDLING EQUIPMENT..................... 74 E - ISOLATE DUSTY PROCESSES................................. 74 F - PROVIDE WET METHODS OF OPERATION........................ 74 G - DESIGN EQUIPMENT TO CONTROL DUST........................ 75 E - PROVIDE EXHAUST SYSTEMS................................. 75 I - ESTABLISH MAINTENANCE AND GOOD HOUSEKEEPING PROCEDURE... 75 J - PROVIDE RESPIRATORS...................................... 76 ] (a) Air Purifying Types of Respirators......... ........ (b) Supplied Air Respirators...... ....................... The Air Line Respirator...................... . 76,77 77 78,79 "1 Abrasive Blasting Respirator...................... 79 J (c) Acceptance and Use of Personal Respiratory Protection by Workmen.............................. 79,80 (d) Use, Maintenance and Care of Respirators....... . 80 J ** WHAT MEDICAL CONTROL SHOULD BE EXERCISED IN THE SELECTION ' AND SUPERVISION OF MEN WORKING ONDUSTY JOBS?.................. 80,81 PHYSICAL EXAMINATIONS................................... 80 DESIRABLE PHYSICAL QUALIFICATIONS....................... 81 RE-EXAMINATIONS......................................... 81 T H E LIMITATIONS CONCLUSION......................... ........................................... 81,82 .aatosln - Aooording to authorities oited,1^'Drinker & Hatch in their book r Tjx Dusts", the pathology produced by asbesto^is not like that of silioosis. P Gardner of Saranao Lake is of the opinion.thit the asbestos fibers group neok of an. alveolus and shut it off, oausingiwhat is known as "Atelectasis". ^ no definite migration or transportation ofijshe dust particles to the lymph ^ ^ 'and no fibrous nodules. As the ateleotatio areas' inorease the reduction in oauses serious dyspnea or laborered breathing;:. Dr. A. J. Lanza (U. S. Health 50} 1 - 1935) suggests that the enlarged hearts'noted frequently in his ^*jes*of seoond stage Asbestosis may be due to the ihoreased load on the heart. It es'more work to pump blood through the fibrosed than:through the normal lung. Re- (^'pathologioal studies from human lungs from oases of asbestosis''have indioated a Effuse typo of Interstitial fibrosis with a oertain mount of emphysema. [*Cj7 - HHAT IS THE MAXIMUM PERMISSABLL DUST C01CENTRATI0N? - There appears to be a Ida variation in the maximum concentration of dust which might be inhaled without Ubsequent injury to workmen. Some dusts (as lead) are determined by chemioal Uthods and the oonoentrations in air are reoorded gravimetrioally as milligrams per ubio meter. However, the available information on the amount of lead dust that is .rmful and the methods of determining lead are better and more aoourate than those Tot; silica dust. It is rather well.agreed that an intake of abort 1.5 milligrams of'; * ^sad a day, whether this is oquired by breathing dust or by drinking water that oon- -.ains lead, is the maximum allowable quantity. Others (as silica, where size is a jjaotor in determining dangerous particles), are usually given by count. Neither Method tells the whole story, but in both cases it may be possible to seoure the in- ' formation necessary for the purpose. . "i. The maximum silioa dust concentration considered permissible in the air breath ed by a workman at any point in the normal breathing tone has not been definitely es ' ;ablihed. There is considerable differenoe of opinion regarding the- range of par- n kioles that are oounted when using the Publio Health Servioe teohnique and light Jv* ..field illumination. Bloomfield of the United States/Public Health Service and Brown of the United States Bureau of Hines contend that they count partiles frcm one mi- , ** -pron and upward, or -even 0.7 micron and upward. The Industrial Commission of Wis- r . tonsin and its Advisory Committee, composed of both employers and soientists, how- * $ & . ever, agreed in 1932 on a tentative figure of 15 million oountable particles under y/ 10 miorons in longest dimension with free silioa content of 35 per oent in a cubic A vtfoot of air as determined by United States Publio Health Servioe technique. Varia- ** idtions in fr68 silioa oontent will make proportional inverse ohanges in this standard. j In the oase of practically pure silioa, the permissible dust count should probably y tfi naever exceed 5,000,000 oountable particles. By oountable partiles is meant those Jpartioles between 0.5 to 10 miorons in the longest dimension. Particles of this - t ^ size are the ones that are believed to oause the greatest damage and form no visible --.cloud. Dust partilos smaller than 0. 5 miorons in the longest dimension are not [ordinarily oountable. Dust partiles .larger than 10 miorons in longest dimension do -'not ordinarily reach parts of the lung where they oan produoe injury of a respira tory nature. Most industrial dusts have but few partiles above two or three ai leron* in size. They are usually about 90 to 95 per cent, below two or three microns _jandT50 per oent. below about 0.5 to 0,7 miorons. An oxooption to this would be a . dust sample taken olese to the point of generation of dust and before the larger particles had time to settle out of the air. In South Afrioa the figure is 1 milligram per oubio meter (or 300 particles per oubio oentimotor. or approximately 3,5 million per oubio foot. ) Dr. Lanza found in 1917 in the Joplin, Missouri district that with good engineering practioe, a figure of 1 milligram per 100 liters of air could be attained. This value attribut ed to Lanza appears too high in comparison with the South Afrioan standards. As there -27- ash III - INSULATING OPERATIONS Insulation plays an Important part in the prooessing of petroleum produota. W O types of insulating material most frequently used are "Sponge Felt" (asbee- fritk ground sponge to give dead air spaoe and thus increase the effectiveness tte insulation) and a mixture of 85# magnesia and 15# asbestos. Roclc wool is ^:0 a considerably lesser degree. In the ordinary commercial form, Rock Wool, ad at our refineries, does not present a dust hazard. It .is also used for f insulation, and is available in small nodule form which can be blown into r "85# magnesia" is a mixture of magnesia and granulated asbestos and pressed l^jblooks 0f various sizes and shapes (usually 16" x 18" x l-l/2"). The most dust jS -fj-om dismantling old insulation and grinding scrap material for use as a plae- 'r "ganister". The average service of men engaged in insulating operations is w o t fii'fce1 years. Most of these men have been transferred from the Common Labor i^rtoent. They work nine out of fourteen eight-hour shifts, in gangs of from two men, and are actually exposed to dust for less than sixty per cent, of their ig time* Goggles are sometimes provided, and occasionally MSA "Camfo" Reepira- g-.bufe this equipment is not used as muoh as it should be. Generally speaking, gfcoufc 85# of their work is with sponge felt and 15# with 85# magnesia insulation, jfc^ne of the larger southern refineries about 300,000 square fee of sppnge felt and gfoOO square feet of 85# magnesia are handled a year. -- - What Phvslologioal Reactions are Provoked by Insulating Materials? According to.Br. Leroy U. Gardner (Journ. Indust. Hyg, Mar. 1937,Yol. 19, No. 3,' P.121) asbestos dust it fibrous partiles does not seem to be readily handled by the protective ^ehanism of the lungs. Quoting from his article "They are not removed to the lymphoid tissue but remain in contact with the delicate walls of the air spaoes. They beoome surrounded by an iron-oantaining coating that fraotures and gives rise to the peouliar structures known as 'asbestosis bodies'. The fibers are irri tating, perhaps because of their form, and they excite a fibrosis which begins about the terminal bronchioles and spreads to form dif fuse patches in the parenchyma. Often the distribution is sub-pleural. In the presenoe of infection, the reaction to asbestos dust is much more- severe than that caused by the dust alone." _ There is nothing in the pertinent literature, nor does the Bureau of Mines know of any evidenoo, which would demonstrate magnesite (a natural magnesium carbon ate) to bo harmful. It would fall in the olass of "nuisance dusts" such as gypsum. While many of the so-called "nuisance dusts" have never been found to be harmful, it lsvfche opinion of most investigators in the field of industrial hygiene that no work er, should be exposed to any dust in a concentration exceeding 75 or 100 millions of partiles per eubio foot of air. .& . j i B During What Such are the Principal Insulating Operations and How Much I>uat Operations? There is, of oourse, a wide variation in the is Produced amount of insu lation work and the amount of dust produced. A few examples, however-, will give & 5od general idoai 3?: INSULATING 12" STEAM LINESi 6" x 18" x l-l/2" blocks of 85# mag- p: nesia are tied on the steam line with 14-gauge galvanized wire and covered with roofing paper to make it waterproof. Often times this work is performed on scaffolds twelve to fifteen feet above the ground, with men lying on their backs under the line part of the time- -28- -iderablo dust (as "high as 18,124,800 particles of less than ten crons per cubic fooc) results from tapping the bloolcs into place, temples taken during the entire operation had an average concentra tion. of 6,881,760 particles per cubic foot. About 90# of these dust -articles were slightly angular, crystalline in appearance and above fire microns or less- in size (as seen under the Konimeter Microscope)j 5% we,re rounded opaque, ten microns or more in size; and 5% were opaque scale-like, five microns or more in size. Samples taken while applying asbestos sponge felt to a 12" steam line had a dust concen.tration as high as 23,788,800 particles of ten microns or less in size per cubic foot. The average was 12,574,080 particles per cubic foot. These dust concentrations are considered too high for work ing without adequate protection. _ INSULATING A 750-POUND CRACKING COIL ACCUMULATOR; 6" x 36" blocks of Johns-Manville "Fire Felt" are first applied and plastered with extra AA Rubberoid Asbestos Cement and waterproofed with Johns- . Jianville "Insulkote". The dustiness of handling these materials has "been, considerably reduced since the manufacturers began shipping the "Fire Felt" in cardboard cartons containing thirteen or twenty . blocks, and the plaster in hundred-pound paper bags. Samples taken .'during this operation had an average dust concentration of 4,502,880 particles, ten microns or less in size per oubio foot. About 75% of these dust particles were slightly angular in appearance, five mi- *orona or less in size; 1.0% were scale-like; opaque; and 15% were ' . `.rod-like and fibrous. INSULATING TREATING PLANT ACID SUCTION LINEu Seotions of "Sponge Felt Pipe Cover" are out to fit pipe lengths with an ordinary carpen ter's hand saw. This operation produces on an average 821,280 par ticles of dust, ten microns or less in size, per cubic foot. Uhder . 'the Konimeter Microsoope all of these particles are slightly angular, ,crystalline in appearance, and five microns or less in size. The blocks or sections of the pipe cover are held in place by wrapping #16 gauge galvanized wire about each one. . INSULATING CRACKING COIL HOT OIL LINES; All hot oil lines at crack ing coils are insulated with 2" asbestos tubing (85# magnesia an d 15# asbestos) held in place by fine copper wire. Sections of the tubing are cut to fit particular areas by means of an ordinary carpenter's hand saw. This produces 7,788,000 particles of dust, ten microns or loss in size, per cubic foot. Under the microscope, SO# of these dust particles appeared to be rounded crystalline and about three mi crons or less in size. Each section of tubing is pounded into place with the open hand so that it fits snugly against the pipe, and then wired into position. The dust produced from both of these operations averages about 3,379,520 particles per cubic foot. Under the micro scope, approximately 80# or 90# of the dust particles appear crystalline, more or less angular, and five microns or less in size; the re maining 10# or more are rounded in appearance, and over ten microns in size. DISMANTLING OR RHiOVING OLD INSULATION; As a general rule, the dismantling or removal of old insulation is a more dusty operation than the application of new insulation. The old insulation is chopped or cut with a hatchet or small hand-axe, and pried loose and pulled off with the hands. This produces dust concentrations as high as 5,890,560 particles, ten microns or less in size, per cubic foot. In ** R R R bp; c= EC C Zr C `T SC C? ,B| E 8 8 8 a * -29- ling an old cracking coil 4" tar line, the average dust concenwas 2,322,240 particles per cubic foot. In appearance these lies were clear crystalline, rather rounded, and fire microns or in size. No fibres were observed in any of the dust samples from itling operations. After a few weeks or months service, insula no on hot lines dries out and appears to disintegrate. This is probdue. to the fact that suoh insulation is usually covered with a ^ther-proof material whioh prevents absorption of moisture from the air. B p CRUSHING SCRAP ASBESTOS: Sorap asbestos inBul&tion, usually the ggj magnesia type, is crushed in a belt-driven Williams orusher to pass `through a screen with one-inch holes or slots, and is then mixed with ow asbestos to make insulating plaster. This operation, which is a very dusty one, is performed by two men, with an average service credit of about twelve years. Goggles and MSA. "Comfo" or Willson Dust Respi rators are worn. Considerable dust is produoed in breaking up the 'sorap insulation by hand prior to crushing (10,195,200 particles, ten miorons or less, per qubio foot), and also when feeding the crusher nhioh B done by shovelling the broken-up pieoes into the hopper and (poking them down with a short wooden stiok (14,839,680 particles per bubio foot). Dust counts as high as 27,527,040 partiles per cubic foot were found in samples taken from over the hopper. These dust con centrations are dangerously high. About 95# of these particles are arply angular, orystalline in appearanoe and five miorons or less in .dizej 5# are opaque scale-like, six miorons or more in size. Crushing ^s'orap asbestos is not a steady routine operation, the exposure varying j^fram eight hours a month to about twelve hours a week. jp- CRUSHING OLD CORX INSULATIONt This operation is performed approxi mately twioe a year and takes about twenty or thirty minutes. The in sulation is orushed on a belt-driven Williams orusher, by the same men ;who orush the scrap asbestos. This orushed oork is used for insulating .lines in the oold settling plant. The average amount of dust produced "is 20,016,178 particles, ten miorons or less in size per cubic foot. `About 80# of the partiles are slightly angular, orystalline, in ap'pe&ranoe, and five miorons or less in size) 20# are round, semi-opaque, *tea miorons or more. Therefore also a large number of .very small black r or dark gr.qy specks. * IV - GUNITING OPERATION 1What is Gunite and How is it Applied? - Gunite is a mixture of approximately irt (one 94 pound bag) of Portland Cement and two parts (twelve scoop shovels) n sharp sand. The sand and cement are mixed dry, ahoveled into the hopper runite machine, using water under about 40-pounds per square inch pressure and jsaed air at thirty to ninety pounds per square inoh. It is applied under pres as a semi-fluid, against the surface to be proteoted (usually process equipment, is, oraeking ooil soaking drums and storage tanks). In practically every case .guniting is done, it follows immediately, after the sand blasting job used to the sura.ce. In most cases, the work is performed by the same crew. The indi-^holding the gunite nozzle is provided with the same protection as is -the of the sand blast nozzle, and the men tending the gunite machines are pro with respirators and are required to use them while actually handling the sand paent. This involves mixing the materials and charging them into the machines wo dustiest parts of a guniting job). Samples taken during these operations the following dust counts of particles ten microns or less in sizei