Document a5MjVK3p5JQ9vzBL6Eqj9QpX

SCIENC AMD JWDtJSTK* MECHANICAL ENGINEERING Published by The American Society of M.echanical Engineers 55Volume Number 4 Contents for April, 1933 THE BALANCING OF ECONOMIC FORCES (PART l)......................................................211 elihu Thomson................................................................................K. T. Compton 225 dust in industry............................................................./. J. Bloomfield 229 social trends..................................................................................................E. E. Hunt 234 THE FERMI-DIRAC STATISTICAL THEORY OF GAS DEGENERATION---- 1 . Vladimir Karapetoff 237 A THERMODYNAMIC THEORY FOR STEAM? . H. E. Longivell 243 significance of speed standardization J. Decker and W. P. Acres 246 CHARLES MacCAUGHEY sames, 1866-1933 .............................................................. 249 PLAINTIFFS | EXHIBIT I ASM-5 editorial 250 SURVEY OF ENGINEERING PROGRESS 252 CORRESPONDENCE.................................................... 263 what's GOING ON.................................... A.S.M.E. BOILER CODE POWER TEST CODES ... BOOK REVIEWS AND LIBRARY NOTES ....................................................................... 271 266 268 269 DISPLAY ADVERTISEMENTS PROFESSIONAL SERVICE 1 CLASSIFIED ADVERTISEMENTS ... 16 14 INDEX TO ADVERTISERS......................................18 OFFICERS OF THE SOCIETY: A. A. Potter, President Erie Oberg, Treasurer Calvin \V. Ricb, Secretary PUBLICATION STAFF.* George A. Stetson, Editor Frederick Lass, Advertising Mgr. COMMITTEE ON PUBLICATIONS! L. C. Morrow, Chairman S. VVL Dudley S. F. Voorhbbs, Vice-Chairman M. H. Roberts W. F. Ryan C. E. Davies, Secretary to Committee on Publications moodily by The American Society of Mechanical Engineers. Publication office at 10th and Northampton Streets, Easton, Pa. Editorial and Advertising departments at the head* qoartssof the Society* 29 West Thirty-Ninth Street, New York, N. Y. Cable address,"Dynamic/' New York. Price 60ccnts a copy, $5 00 a year; to members son affiliates, $0 cents a copy, $4.00 a year. Pottage to Canada, 75 cents additional, to foreign countries, $1.50 additional. Changes of address must be received at Society headquarters two weeks before they are to be edeccm on the mailing list. Please tend old as well as new address. . . . By-Law: The Society shall not be responsible for statements or opinions advanced in papers or . . . printed in its pablkanoes (Bl. Pax. J). . . . Entered as second-class matter at the Post Office at Easton, Pa., under the Act of March 5, 1879. . . . Acceptance for mailing at special rate of postage provided ior to Kcnon 1105, Act of October 3,1917, authored on January 17, 1921.... Copyrighted, 1933, by The American Society of Mechanical Engineers. DUST in INDUSTRY The Sampling and Analysis of Industrial Dusts By J. J. BLOOMFIELD1 HE abundant evidence at hand showing that the inhaled dust gain access or arc retained by the human Tinhalation of certain industrial duscs is an impor lung. For this reason it is essential to determine the tant factor in die causation of pulmonary disease size of the dust particles present in the industrial atmos has emphasized the significance of the quantitative pahse re. pects of this problem. A knowledge of the dust content With reference to the quantity of dust present in the air of the industrial atmosphere is required not only for the of a workroom, it is apparent that when the dusc concen purpose of determining the extent of the hazard involved tration is high the exposed person will inhale a greater in various manufacturing processes, but is also useful quantity in a given period of time than he will when it is in measuring the dticiency of protective devices which relatively low, and since the rate of production of the may be used in the elimination of the dust hazard. The disease is partially dependent upon the total amount of object of the present contribution is to describe the under dust inhaled, this latter fact plays an important r61e in lying factors involved and the technique employed in determining the time of onset of the end result. The the study of the quantitative phases of the industrial need for the evaluation of the quantity of dust in the in dusts which may produce injur)' to the respiracory sys dustrial atmosphere is obvious. tem. Such dusts arc produced by the numerous indus trial operations involving the drilling, crushing, and grinding of mineral matter such as talc, quartz, granite, slate, and cement. The properties of a given dust which determine its capacity to produce pulmonary pathology are the nature of the dust, that is, its chemical and mineralogical com position, its particle size, and finally the quantity of the dust dispersed in the atmosphere. One of the outstanding results of the last 2.0 years of research in the field of dust inhalation is the demonstra tion of the fact that, in general, the degree of health hazard associated with the inhalation of any dust, all other factors remaining constant, is dependent upon the mineralogical composition of the dust. For example, it is now well established that the inhalation of certain types of dust, such as granite dust, will in time produce fibrosis of the lungs, frequently associated with tubercu losis. In other cases exposure to dust may result in the production of a far lesser degree of fibrosis without sub sequent tuberculosis; this is true of cement dust. . And finally, there are certain types of dusts which produce little or no lung fibrosis, as typified by marble dust. In general, it has been found that those dusts which are NATURE OF DUST Research on the problem of industrial-dust inhalation has demonstrated that so far as their fibrosis-producing qualities are concerned, dusts may be divided into three groups: (1) those composed completely of combined silica, that is, silicates, such as pure asbestos; (1) those containing free silica in the crystalline form known as quartz (granite contains approximately 35 per cent of quartz), and lastly, (3) dusts containing free silica in a non-crystalline form such as diatomaceous earth. In general it has been found that the harmfulness of a quartz-containing dust is in direct proportion to its quartz content. For this reason in attempting to evalu ate the harmfulncss of a dust it is of the utmost impor tance to ascertain its quartz content. This should be done by a chemical and mineralogical analysis. We find in practice that samples of dust settled out of the atmosphere at the breathing level of the worker serve admirably for these chemical and mineralogical determinations. It is our practice to have such analyses made by an expert geologist. Only in this way is it possible to determine accurately the amount of quartz present in a given sample. Table 1 presents the quartz high in quartz content are the ones which produce a TABLE 1 PERCENTAGE OF QUARTZ PRESENT IN VARIOUS disabling fibrosis of the lungs most readily. Hence the necessity for knowledge concerning the chemical and mineralogical composition of a dust is obvious. INDUSTRIAL DUSTS Kind of dusc Rock-drilling dusc (bituminous-coal mine).... Percentage of ijuartz 54.0 So far as the size of the dust particles is concerned, it is Granite-cutting dust............................................ 35 -2 apparent that in order for any given dust to produce in jury to the lung it must gain access to the parenchyma Rock-drilling dust (anthracite mine)................ Brass-foundry dusc............................................... Dusc from raw mills in cement plant................ 31-0 19.0 6.5 of the lung, the site where the harmful effects of the dust take place. It is known that not all of the particles of1 Slate-mill dust (Vermont red slate)................... Silverware-polishing dust................................... Anthracite dusc.................................................... 3.0 1.7 1.5 Bituminous-coal dust........................................... 1.2 1 Sanitary Engineer, U. S. Public Health Service, Washington, D. C. Cement dust.......................................................... less than 1.0 Presented at the National Process Meeting arranged by the Process Slate-mill dust (Vermont green slate)............... trace Industries Committee of the A.S.M.E., and held under die auspices of Talc-mill dusc....................................................... none the Buffalo Section of the Society, Buffalo, N. Y.,June6 to8,1932. Marble-cutting dust............................................. none 229 230 Mechanical Engineering content of dusts obtained in various industries which we have studied. It is quite evident that, judged by quartz content, rock drilling occupations in the coal-mining industry and certain occupations in the granite-cutting industry and in brass foundries may be considered as hazardous. That this is true is evidenced by the high rates of illness and death from silicosis and tuberculosis in some of these industries.2 at a high magnification (1500 to 2.500 diameters); from this cither an enlarged print may be made, or the nega tive may be enlarged by means of a stercopticon. The particles revealed on the enlarged print or screen may be measured by means of a millimeter scale. The particlesize dimensions arc grouped in classes according to size, from which a percentage distribution curve is easily obtained. Fig. 1 presents the particle-size distribution of talc dust from the air of a workroom in which talc PARTICLE SIZE OF DUST It has been demonstrated that particles of a size greater than 10 to 11 microns in the longest dimension are very seldom found in the lungs. This absence of larger par ticles is partly due to the fact that the number of such particles greater than 10 microns in size present in indus trial air is, as compared with the lower sizes, compara tively small, and, due to gravity and the protective action of the mucous surfaces of the upper respiratory tract, these larger particles do not penetrate to the terminal portions of the respiratory tract. Hence we need only concern ourselves with those dust particles that are less than 10 microns in the longest dimension. In order to ascertain whether or not an industrial dust is capable of gaining access to the lungs, it is necessary FIG. 2. PHOTOMICROGRAPH OF TALC DUST OBTAINED WITH THE OWENS JET DUST COUNTER. X6jO FIO. I PARTICLE-SIZE DISTRIBUTION OF TALC DUST to make particle-size studies of the dust under considera tion. In practice the samples for such studies may be obtained by the use of the Owens jet dust counter.' This apparatus projects the atmospheric dust directly on a microscope cover slip. This cover slip may then be properly mounted and examined by any one of sev eral methods. Such samples may be studied micro scopically, using a magnification of 1000 diameters (oil-immersion objective), and the horizontal diameter of a representative number of particles measured by means of a calibrated filar ocular micrometer.4 In another method a photomicrograph of the dust is made * Russell, A. E., Britten, R. H., Thompson, L. R., and Bloomfield, J. J., "The Health of Workers in Dusty Trades. II. Exposure to Siliceous Dust (Granite Industry)." Public Health Bulletin No. 187, July, 1929. Owens, J. S., "Jet Dust Counting Apparatus," Jl. lnd. Hy^imt, April, 1923, p. 522. 4 Hatch, Theodore, and Choate, Sarah P.t "Statistical Description of the Particle Size Properties of Non-Uniform Particulate Substances," U. Franklin Inst., March, 1929. was being ground to a very fine state of subdivision. The measurements, from which the data for this figure were obtained, were made by means of a filar ocular micrometer at a magnification of 1000 diameters. With this magnification it is possible to measure particles as small as 0.5 micron in diameter, while particles smaller than 0.5 micron arc easily distinguished at this magnifica tion, and, although not measured, their presence is re corded. For routine particle-size measurements the photomicrographic method as described by Green* has a decided advantage over the direct microscopic measure ments, in that the task is less tedious and the particles arc measured with more case and accuracy. However, for all practical purposes the filar-micrometer method should fulfil the required needs. An examination of Fig. 1 shows that only 16 per cent of the particles were found to be less than 1 micron, the major portion (65 per cent) being between 1 and 1.5 microns in size. The median size of the dust was found to be 1.5 microns. Fig. x is a photomicrograph of the same specimen of dust. QUANTITY OF DUST As pointed out earlier, a knowledge of the quantity of Green, Henry, "A Photomicrographic Method for the Determina tion of Particle Size of Paint and Rubber Pigments," Jl. FmUm Last., vol. 192, no. 5, p. 637, Nov., 1921. April, 1933 231 Just dispersed in the industrial atmosphere is very im portant, since with any given dust the rate of production of the injury will be dependent upon the total quantity of dust inhaled. The author feels that from the hygienic viewpoint the {article count is at present the best index of the degree of atmospheric pollution. The decision as to the size range of the partides which should be included in the dust count is a question requiring careful consideration. Ob viously the size of the smallest visible particle will de pend on the magnification and type of illumination used in the microscope, the refractive properties of the dust, and, to some extent, on the visual acuity of the observer. We must bear in mind that our chief interest in this prob lem is in its industrial and hygienic aspects. Primarily we are interested in differentiating between the dust content in ordinary normal atmospheres, not known to be harmful, and certain industrial dusts which arc known to be assodated with lung damage. This difference is sharply marked as far as the dust particles between ap proximately l/ and. io microns in diameter are con cerned; but the difference between such normal and ab normal air is masked and lost when we include in our determination the particles of ultramicroscopic size which arc present in vast numbers in all air. So far as the upper limit of particle size is concerned, it has been demonstrated by the South African studies that particles greater than io microns in the longest dimension are of negligible importance. The data con cerning the lower size limit of potentially hazardous dust is not so conclusive. The only available data which throw some light on this point are found in the work ofMoir,*ofSouth Africa, who examined microscopically no dust particles obtained from two specimens of silicotic lung and found that only 13 per cent of the particles were less than 0.5 micron and abouc 36 per cent of the particles less than 1 micron in diameter. The majority of the partides (60 per cent) were between 1 and 3 microns in size. The median size of the dust was found to be 1.1 microns in diameter. Practically the same results were obtained by Watkins-Pitchford,7 who examined and measured the silica particles in sections of silicotic lungs illuminated by polarized light. Drinker,* in comparing the size frequency of the particles measured by .Moir with the partides found by him in the sputum of(men employed in ore mills, found a close correspondence. The findings of Moir and Watkins-Pitchford have also been corroborated by Mavrogordato,' who examined dust both with light and dark ground illumination, in sections of human and animal silicotic lungs as well as * Moir, J., "Report on a Specimen of Dust From Silicotic Lungs," General Report of the Miners' Phthisis Prevention Committee, Pretoria, 1916, Appendix 9, pp. 13S-140. * Watkvns-Pitchtord, W., "The Situation, Outline and Dimensions of Mineral Particles Visible by Polarized Lighc in Sections of Silicotic Lungs, Mounted in Canada Balsam." General Report of the Miners' Phthisis Prevention Committee, Pretoria, 1916, Appendix 8, pp. 135-- 138. * Drinker, Philip, "The Size-Frequency and Identification of Certain Phagocytosed Dusts,"/!. InJ. Hygiene, vol. 7, no. 7, July, 1925. Mavrogordato, A., "The Value of the Konimetcr," Publication of the South African Institute of Medical Research, no. 17. the dust recovered from these lungs. As a result of his work and that of his colleagues in South Africa, Mavro gordato says: "In the damaged lungs, as far as simple silicosis is concerned, the lesions arc discreet, localized, and associated with visible particles; whereas, if the ultramicroscopical particles were an important agent, one would expect the simple disease to be generalized and to show no particular association between lesions and visible particles." In connection with the lower limit of particle size of dust of pathologic significance, the following pertinent question arises: Aside from the evidence direct or indirect of the non-retention of minute particles of dust by the lungs, what evidence is there that appreciable per centages of ordinary industrial dusts ever fragment into those minute sizes less than 0.5 micron in diameter? It is a well-known fact that in most of the fine-grinding operations in use today, such as in the preparation of paint pigments, considerable energy must be expended to obtain a product the particle size of which is less than 0.5 micron in average diameter, and this not in an industry where dust is an evil by-product but where finely divided dust is the chief aim of the whole indus trial process. The best answer to the question just raised, namely, What is the particle-size distribution of industrial dust? would be data of actual measurements of such dust. Unfortunately we have but scant published data to date on the particle-size frequency of dusts in the air of in dustrial establishments. In 1919, Fchnel10 reported some particle-size dust measurements in connection with a dust study of hard-rock drillers in New York City. As a result of his study, Fehncl reported the findings on three samples, which showed the dust, which was less than one micron in size, to vary from 1 to 15 percent. Most of the dust in these hard-rock drilling operations was, according to Fchnel, between z and 5 microns in size. Badham,11 in studying the dust hazard among sand stone workers in Sydney, measured some 16,000 particles of dust in the air of work places and found that 67 per cent of these particles were about 1.5 microns in size. From his study Badham states: "It would appear that below 10 microns there is no selective action by the dust cells of the lung, and that the particles found in the lung have the same size-frequency as those in the air breathed...." In a particle-size study of 10 samples of aerial industrial dusts made by the filar-micrometer method at a mag nification of 1000 diameters, the author found that prac tically all of the dust was less than 5 microns in size. Only 1 per cent of the particles was less than 0.5 micron, 18 per cent were less than 1 micron, and the majority of the dust (73 per cent) was found to be between 1 and 3 microns in diameter. From all of the evidence just presented and in the ab- 10 Fehncl, William J., "A Study of Silica Dust in Hard Rock Drilling in New York City,"//. Ini. Hygiene, vol. 11, no. 2, Feb., 1929. 11 Badham, Charles, Reyner, H. E. G., and Broosc, H. D., "Dust Sampling in Sydney Sandstone Industries," Report of the DirectorGeneral of Public Health, New South Wales, Dec., 1927, p. 74. 232 Mechanical Engineering sence of conclusive proof to the contrary, it is apparent that we need only be concerned with those dust particles between '/ and 5 microns in size, and from a practical standpoint the lower limit of particle size may well be taken at about one micron. The method of dust count ing which we have used, the description of which fol lows, is capable of revealing particles as small as one micron quite readily, and in the hands of a trained person smaller particles may be enumerated. Many methods have been devised and used for the a glass plate which is kept beneath the surface of the water or other suitable fluid in the collecting flask. The dust is momentarily arrested, wetted by the collecting fluid, and in this manner trapped. The impinger apparatus consists essentially of two portions: first, a source of sufficient suction to draw the air to be sampled through the sampling device; and second, the sampling device or impingcr itself, which consists of a container and the impingcr tube and plate. As a source of suction one mav use either an electrically driven pump or a compressed-air ejector device. Fig. 3 depicts the essential portions of the apparatus, which consists of a straight piece of Pyrex glass tubing 13 mm in outside diameter and approximately 315 mm in length. The tube is drawn down in streamline form at its lower end to a tip with a 1.3-mm orifice. A circular glass impinging plate approximately 3 mm in thickness and Z5 mm in diameter is attached to the lower end of the impinger tube at a distance of 5 mm from the orifice by means of three glass rods. The collecting medium (distilled water) in the sampling flask is of sufficient volume to keep the impingcr plate immersed at a depth of approximately 3 cm. In sampling, the outlet or suction elbow of the sampling flask is connected with the source of suction by means of a suitable length (15 ft) of non-collapsible rubber tubing. The duration of the sampling period should be such as to yield a satisfactory suspension of dust for analysis, and is thus dependent on the concentration of dust in the atmosphere. Under the usual industrial conditions, samples of from 10 to 30 cu ft of air yield sufficient suspended dust for analysis. Since a sampling rate of 1 cu ft per min is maintained, this will require a sampling period of from 10 to 30 min. The collecting efficiency of the apparatus is dependent upon adherence to the previously cited impingcr-tubc dimensions and the sampling rate of 1 cu ft of air per min. Experimental tests of this instrument against suspensions of finely divided silica dust in air have con- FIG. 3 ESSENTIAL PORTIONS OF THE GREENDURG-SMITH IMPINGER APPARATUS FOR DUST SAMPLING A purpose of determining the quantity of dust in air. These methods have already been fully discussed in an excellent review of this subject by Dr. Greenburg.12 Sedgwick-Rafter Cell Whipple Disk Suffice it to say that for the purpose of dust sampling in FIG. 4 SEDGWICK-RAFTER CELL AND WHIPPLE DISK EYE either high or low dust concentrations, the Grccnburg- PIECE FOR USE IN COUNTING DUST PARTICLES UNDER A Smith impingcr apparatus now finds universal favor.13 MICROSCOPE This instrument has been used by the United States Pub lic Health Service in all of its dust studies during the past sistently yielded efficiencies of 9S per cent at the specified nine years. It is also being used by other workers in sampling rate. this field both here and abroad. Since practically all dusts arc, to some extent, soluble in In this instrument, the air to be sampled is drawn water, it is good practice to analyze the samples as soon through a glass tube and impinged at a high velocity on** as possible. Such practice tends to prevent any undue llocculation as well as any solvent action on the dust par ** Greenburg, Leonard, "Studies on the Industrial Dust Problem," Public Health Reports, vol. 40, no. 16, April 17, 1925. ^Greenburg, Leonard, and Bloomfield, T. J., "The Impingcr Dust Sampling Apparatus as Used by the United States Public Health Ser vice," Public Health Reports, vol. 47, no. 12, March 18, 1932. ticles. In the laboratory14 the dust suspension in the 1 ` For a more detailed description of the dust-counting technique, the reader is referred to a contribution in the Public Health Repots of March 18, 1932. April, 1933 233 sampling fluid is filtered through a 315-mesh screen and then diluted so that the number of dust particles in the microscope field is equal to approximately 50 to 75. Two or more i-cc portions are placed in SedgwickRafter cells for counting (see Fig. 4). The microscope is of the ordinary type, provided with a suitable eyepiece and objective and fitted with an Ahbfc condenser. A Whipple disk-eyepiece micrometer (Fig. 4) is placed in the microscope eyepiece and the microscope tube length is adjusted so that the side of the ruling in the eyepiece is t mm in length. (We employ a 7.5 X eyepiece, 16mm objective, and a tube length of 17S mm.) As a source of illumination we use an ordinary type of micro scope lamp with the iris of the Abh condenser system adjusted so as to provide a high degree of visibility. In making counts the microscope should be focused throughout the depth of the cell since some of the dust particles may remain in suspension. Since the counting cell is 1 mm deep and the area in the microscopic field is x sq mm, each count represents the amount of dust in a cubic millimeter of the sampling fluid. Knowing the original dilution of the sample and the number of cubic feet of air sampled, it is an easy matter to compute the number of dust particles in the sample per cubic foot of air. It is of course necessary to make control dust counts on the sampling fluid. In Table 1 a summary is presented of the average dust content of the air in certain dusty industries. This table shows that the highest dust exposure was in the TABLE 2 AVERAGE DUST COUNT IN CERTAIN DUSTY TRADES Industry Dust count in millions of particles per cubic foot of air SUce-finishing mills: Floor men....................................................................... Loaders.......................................................................... Disk-crusher operators................................................ Talc mining: Jack-hammer drillers....... Muckers......................................................................... Talc-finishing mills: Crushers and cylindermen........................................... Packers........................................................................... Marble cutters.................................................................. Marble carvers.................................................................. Granite quarrying: Leyner driilers.............................................................. Jack-hammer drillers................................................... Plug drillers.................................................................. Cement mill, average of all operations......................... Gramre curdng: Hand pneumatic-tool operatives................................ Machine pneumacic-tool operatives.......................... Attendant labor........................................................... Anchracite mining: Miners and miners' helpers......................................... Attendant labor............................................................ Bicuminous-coat mining: Coal curcers and coal loaders..................................... Attendant labor............................................................ Silverware manufacturing: Dusty processes............................................................ Non^lusry processes..................................................... Municipal dust (street cleaners): Congested district........................................................ Residential district....................................................... Corroa industry: Carding room................. Weaving and spinning room...................................... 1598.0 1276.0 312.8 2159.8 44.8 14.0 50.1 32.8 19-1 144.4 112.1 36 *9 26.0 59 2 35 9 17 0 231.5 31.1 112 3 39 52 1.7 4.1 18 8.6 45 slate mills, talc and coal mining, and in the granitecucring industry. Owing to the high percentage of quartz (35 per cent) present in granite, as compared with the dusts in the other industries listed in Table x, gran ite cutcing is revealed to be the most hazardous of rhe occupations we have studied. A test of the value of any technique is in the results obcained in its practical application to a definite prob lem. Such a test was offered to us in the study of the health hazards of granite cutters in Vermont. In this study the following investigations were conducted for a period of slightly more than two years on a large group of workers: (i) Examination of the workers to determine (a)annual frequency of ABSENTEES FROM TUBERCULOSIS 10 0 AB CD Granite Worker* 1.3 1 4 IS HordRock Iron General Gold Cement and Sick Mining Steel Benefit 195 (\>) ANNUAL DEATH RATE PER 1000 PERSONS FROM TUBERCULOSIS A B C D Rural SS* 4* \* Vermont Deaths Deaths Deaths Age 20'59 * From Qtginninq of Study to Working Up of Report - about Three Years - among 972 Workers:A,6/4;3,/04;C, !46iJ>,i05. FIG. 5 (a) ANNUAL FREQUENCY OF ABSENCES FROM TU (A)BERCULOSIS (EIGHT DAYS AND MORE). ANNUAL DEATH RATE PER IOOO PERSONS FROM TUBERCULOSIS their general physical condition; (x) special physical examinations to determine the prevalence of specific diseases of the respiratory system and the lung pathology resulting from exposure to granite dust; (3) record of the nature and severity of disabling illnesses; (4) occupa tional mortality statistics; (5) autopsies; and lastly (6), detailed studies of the nature and quantity of the dust exposure in each occupation. Let us briefly examine the results of this study. The whole group of workers was divided into four sub groups, depending on their average dust exposure. Fig. 5 shows the annual frequency of absences due to tuberculosis and the annual death rate per 1000 persons from tuberculosis among the workers in these four groups. This figure also compares this data with simi lar information for other industrial groups. In group A, which included hand pneumatic-tool operators and in which the exposure averaged about 59 (Continued on page 262)