Document Ja18g0RDwq3vBadd0ngZ021O

CHARLES Z. CARROLL-PGRCZYNSKI . j_-r * ` - ' . ' . .VS .* * * * . . .. ASBESTOS * * ' * . FROM ROCK TO FABRIC THE TEXTILE INSTITUTE io Blackftiars Street'.* Manchester 3 1956 j-fl. . ' ASBESTOS ' ASBESTOSIS--Asbestos Dust RECENT LITERATURE OF INTEREST Asbestosis. A. J. Vorwald, T. M. Durkin and P. G. Pratt" Arch. Ind. Hyg. Occ. Med., 1951, 3, No. 1; Brit. Chem. Abstr., A.jjl 1951, 1106, 1. Inhalation or injection of asbestos fibres caused peribronchiolar fibrosis similar to human asbestosis in guinea-pigs, rats, rabbits, and cats, but not in dogs or mice. The mode of action of asbestos in production of this reaction is mechanical rather than chemical: fibres of 20--50[i in length produced the reaction, shorter fibres were inert: ignition ofchrysotile fibres which changed their structure made them inert. Injection of brucite produced a similar fibrosis, glass-wool was inert. AI(OH)a did not retard or prevent development of fibrosis. Air containing less than 1 million fibres longer than 10^ per cubic foot was capable of producing typical asbestosis when inhaled. The duration of exposure necessary to produce asbestosis was inversely proportional to the concentration .of long fibres. Established asbestosis ceased to progress after discontinuance of dust exposure,. possibly due to formation of asbestosis .bodies which are not able to produce fibrosis. The outcome of experimental pulmonary tuber culosis was unaffected by inhalation of asbestos. . Effects of asbestos on tissue cultures; Comparative studies with quartz and coal dust. T. H. Belt, I. Friedman and E. J. King. J. Path. Bad., 1947, 59, 159--164. Compared with quartz and coal dust, asbestos was slowly phagocytosed: no toxic effects were observed on the phagocytes, though their motility was decreased. Symposium of industrial medicine. Pneumoconioses. L. U. Gardner. Med. Clinics. N. Amer., 1942, 26th July; Attention is given to Roentgen findings, the part played by tuberculosis in asbestosis and its relation to infection, chemical course, complications and diagnosis. . Chemical studies in asbestosis. M. J. Stone. .Amer. Rev. Tubera, 1940, 41, Jan. This report is based upon examination of 180 persons formerly employed in the opening, carding, spinning and weaving departments of an asbestos brake lining plant. . Carcinoma and asbestosis of the lung. Report of a case. T. K. Owen. Brit. J. Cancer, 5, 382--3. Asbestosis of the lung was found 20 years after the patient had worked in an asbestos factory for one year. . Asbestosis. R. R; Sayers and W. C. Dreesen. Amer. J. Publ. Healthy 1939, 29, 3, 205; Ceramic Abstr., 1939, p. 168. In a study of the North Carolina textile mills using asbestos fibre, a hydrated PHYSICAL AND CHEMICAL PROPERTIES OF ASBESTOS FIBRES 45 magnesium silicate containing no quartz, pulmonary asbestosis was the principal defect found. Exposures ranged from 0*10 to 76 million particles/cu.ft. Persons exposed from 5 to 10 years to dust concentrations exceeding 5 million particles/cu.ft. showed definite evidence' of asbestosis. Data so far obtained indicate that 5 million particles/cu.ft. is the maximum safe concentration. Prevention of pneumoconiosis. Anon. Chem. Age (London), 1944, 51, 180--181. Medical Problems of the asbestos-cement industry. Hindley-Smith. Brit. J. Phys. Med., 1947,10,2,50: Brit. RubberResearch, 1948,26,316. The author, whowasa part-timemedicalofficeratah asbestos-cement factory for five years, did not find-a tingle case ofincipient asbestosis . in this period, though he came across a few long-standing chronic ones. Dermatitis was the* biggest problem, the cases occurring amongst men handling cement or a mixture of cement and asbestos. Asbestos itself did not appear to cause dermatitis. Asbestosis. G. Luton and J. Ghampftt. Arch, maladies profess. med. trav. sec.'sociale, 1946, 365: Brit. J. Ind. Med., 1948, 5, 44: Chem. Abstr.y 1948, May, Aug. In a factory processing waste asbestos, the atmospheric dust concentration was 6-74 mg./cu.m., and the dust contained 2-14*6 per cent free silica; most of the particles were large. When raw Canadian asbestos was substituted for the waste asbestos, the atmospheric dust concentration fell to 6-11 mg./cu.m., there was no free silica, and 90 per. cent of the particles-were not larger than Iff. Asbestosis bodies appeared in the sputum within 3 months after exposure and persisted for.as long as 15 years after exposure had ceased. Although these bodies were found in all exposed to the dust, their presence in numerous amounts and massed arrangements in the sputum provided partial diagnostic evidence of pulmonary asbestosis. : Lung carcinoma caused by asbestos inhalation. Fr. Boemke. Med. Monatsschr, 1953, 7, 77--81; Chem. Abstr., 1953, April, July. The relation between fibrotic' changes caused by asbestos deposits in the lung and carcinoma is discussed. The lower lobe is the site .of predilection. Characteristic are the multi-centred developments of fiat.epithelium carcinoma. : .. The pathology ofdiseases due to the inhalation ofdust. Fr. Boemke. Med. Monatsschr., 1947, 1, 2--6; Chem.- Abstr., 1948, 42,. 9002.`: Thomas-slug pneumonia, pulmonary disorders due to Aluminium u dust; and asbestosis are discussed. Attention is called to the associ ation of asbestosis with pulmonary carcinoma, the latter almost, always taking the form of carcinoma of the pavement epithelium. 46 ASBESTOS Mineralogical aspects ofpneumoconiosis research. G. Nagelschmidt. Research (London), 1949, 2, 170--5; Chem. Abstr., 1950, 44, 8020. Three different fibrotic mineralogical groups are distinguished:--- (1) quartz and other forms of uncombined SiO*, (2) other silicate minerals, (3) fibrous silicates especially asbestos. The effect of asbestos and asbestos and aluminium on the lungs of rabbits. E. J. King, J. W. Clegg and V. M.. Rae. Thorax, 1946, 1, 118. ; _. Toxicology. T. Lawrence. Ann.Res. Med., 1952, 3. A review with particular reference to asbestos, silicones, halogenated methanes arid insecticides. , . Mortality from lung cancer in asbestos workers. R. Doll. Brit. Jx Ind. Med. 1955, 12, 81---6; Chem. Abstr.y 1955, 49, 9195. Among 105 persons who had been employed at one asbestos works,. and for whom the cause of death was determined at autopsy, 18 showed lung cancer. Of these 18, 15 also showed asbestosis; these 15 had worked at least 9 years before dust-control regulations had become effective. Among 113 men who had worked at least 20 years in places where they were liable to be exposed to dust, there were 11 deaths from lung cancer, 22 deaths from other respiratory and cardiovascular diseases, and 39 deaths in all as compared with expected numbers of 0*8, 7*6 and 15*4 respectively; all cases of lung cancer were associated with asbestosis. Conclusions: Lung cancer was a specific industrial hazard of certain workers. The risk has become less as the duration of employment under old dusty conditions has decreased. * Destruction ofmineral particles and fibres in the lung after exposure to asbestos dust. J. F. Knox and J. Beattie. Arch. Ind.. Hyg. Occ. Med., 1954,10,30--6; Chem. Abstx., 1944, 48, 14045. Examination of lungs from 27 cases where asbestos exposure showed that the greatest proportion of particles were in the 5 to 25(z range, and that in early exposure an appreciable portion was found above 25[i. in length, with this fraction decreasing after the 8th year following the last exposure. . Asbestos dusting apparatus. L. C. Pharo. U.S.P. 2,420,495. Dust is removed from asbestos continuously without injury to the material by introducing it into the top of vertical and cylindrical screens containing a shaft which is rotated at 300-T-720 r.p.m. and to which are attached agitating arms to disperse the fibres. Finely divided material is dislodged and the dust removed through the screen by suction. ' - PHYSICAL AND CHEMICAL PROPERTIES OF ASBESTOS FIBRES 47 The problem ofdust in asbestos preparation. M. C. Benham. 1954. Office of Chief Gov. Mining Engineer,. Salisbury, Rhodesia. This comprehensive report deals with various problems of dust suppressipn during the extraction of asbestos from rock. Air handling and dust control at the Jeffrey Mine of Canadian Johns-Manville-Company. H. Rozowsky. Canad. Mining J., 1953, Sept. The separation of air-borne dusts and particles. G. H. Davies. Proc. Jnstn. Mech. Engrs. (London), 1952, IBV185--98; Communi cations 199--213. . Filter efficiency and standardisation of test dust. H. Heywood. Proc. Jnstn. Mech.-Engrs. (London), 1952, IB, 169--74; Discussion 175--9; Communications 180--4. The basic theory is developed lor determining the efficiency of air cleaners and filters. Character istics of natural air-borne dusts, methods of examination of dusts, and methods of preparing standard dusts for testing air filters are described. . Occupational Diseases ofthe Lungs. Institute ofIndustrial Medicine A.MJL. Arch. Induslr. Health 1955, 11, No. .3, 183--211. Papers presented at a symposium on the above subject are as follows:-- Pathology of Asbestosis. K. ,M. Lynch, 185--188; . Recent Trends in Industrial Health. A. J. Lanza, 183--184. Functional Abnormalities of Industrial Pulmonary Fibrosis. G. W. Wright, 196--203. Some Clinical Observations of Asbestosis in -Mine and Mill Workers. P. Cartier, 204--207.' Asbestosis as Differentiated from Other Pneumoconioses. O. A. Sander, 208--211. PHYSICAL AND CHEMICAL PROPERTIES OF ASBESTOS FIBRES 5I CHAPTER 3 Section V MICROSCOPY the asbestos mineral, although in the form of hard rock, can be. easily separated into slender fibres. The indlvidualvfibres ofasbestos' ^ afe so fine as to ,be below ,the limits that normal microscopes can 'resolve. '. . . Table 15 gives comparisons of approximate diameters of various fibres with asbestos:-- ;~ . . . " Table 1$. ' Type ofFibre > Fibre diameter . ' Fibres in one - in inches . ' . linear inch - Human Hair ... ... 0*00158 . . 630r Ramie ... ............... 0*000985 - 1,015 Wool ........................... 0^0008 to 0*0011 910 to 1,250 Cotton............................ 0*0004 2,500 Rayon........................... 0*0003 . . 3,300 Nylon............... ... 0*0003 3,300 Glass ........................... 0*00026 3,840 Rode Wool ............... 0*000142 to 0*000284 3,520 to 7,040 Asbestos (Chrysotile) ... 0*000000706 to 850,000 to 1,400,000. . 0*00000118 . Canad. min. metall. Bull., 1951, April. Owing to the unlimited splitting of the fibre, it is difficult to determine its proper form. The original theory for many years was that asbestos fibres were solid. A new theory has recently been advanced that asbestos fibres in the final stages of dissection are tubular. Tubular crystals are believed to be knownin other minerals, specifically endellite. Thus it is postulated that chrysotile, the fibrous form of serpentine, bears the same relation to antigorite, the plate-like form of serpentine, as the tubular endellite does to the plate-like kaolinite1. ; The tubular structure of chrysotile asbestos Has been reported : by several investigators?*8,4. It has.also been stated5,6 that chrysotile asbestos has an internal capillary structure, and that the capillaries within the individual fibres appear to be blocked in some manner with strongly sorbed water plugs, which are permeable to water vapour and-, ammonia but not to less polar gases. These water plugs can be removed by activation. at425G. at 10--5 mm. pressure and re-formed in samples activated at less than 425G. by saturation with water vapour. Fig. 16 Canadian Chrysotile Asbestos . X 30,000, 55 ASBESTOS TEXTILES 181 Fig. 93 : Asbestos Filled Rope Lagging ASBESTOS PACKING Asbestos yam is used in the manufacture of various forms of asbestos packing for valves, steam engines,. pipe lines, air pumps and gasoline pumps. The yarn is worked up into twisted or braided forms that are compressed info rings or into cloth which is subsequently coated with rubber compound and folded or wound into various forms of packing for high pressure steam work, and also transformed into gaskets for boiler tubes, handholes and manholes of boilers and for pipe flanges. ;. In fact asbestos packing is suitable for almost every purpose where packing is required. ... . . fig. 94 shows general constructions of steam packings. : 182 ASBESTOS - Fig. 94 Asbestos Rolled Cloth Packing Asbestos Multicore Packing - Asbestos Block Backing Asbestos and Lead Wire Packing SQUARE PLAITED ASBESTOS PACKING This material is used as self-lubricating packmgfor general steam purposes, and is made from good quality asbestos yam of winch each strand is individually impregnated with a high-grade lubricant, and the graphited square section is built up on solid plait con struction. . ASBESTOS TEXTILES Fig. 95 Plaited Asbestos Packing steam Tagring ASBESTOS . Fig. 97 v High TemperaturePacking Fig. 98 Add-Resisting Packing ASBESTOS TEXTILES " 185 Another type of steam packing is shown in Fig. 96. This material is -made of several bands of anti-friction white metal embedded in rubber-proofed asbestos cloth. Such composition forms a series of metal rings which give any piston rod a glass-like' surface, doing away with any possibility of scoring, and is particu larly recommended for marine and all high-pressure steam engines. HIGH TEMPERATURE PACKING . .. Exposure to high temperatures necessitate the use of chemically pure asbestos yams. The packing shown in.Fig. 97 is braided from pure asbestos yam reinforced; with phosphor-bronze wire. Such packing is used against superheated steam and hot oil at tempera tures up to liOOO0!1. , ACID-RESISTING PACKING Crocidolite asbestos is the most resistant type to acids and the packing shown in Fig. 98 is. made from pure blue asbestos yarn,, braided cover-upon-eover, and impregnated with a special add- resisting lubricant. One of the chief applications of this packing is in add pumps. . CHAPTER 14 . Other Industrial Uses of Asbestos GASKETS' . a gasket is a packing designed for inclusion between rigid parts of a fluid container in essentially stationary relationship*. The problems of making a pressure tight joint between flanges of pipes, or providing a gas right seal for engine cylinder heads, exhaust flanges, or manifolds require careful consideration of several factors in order to choose the right type of material1-4. Hie most important are (a) temperature and pressure,. (&) fluid--"whether it. is liquid, gas or steam, and whether it is corrosive and (c) nature of the flange surface. . . Asbestos, has been used for m^ny years as a gasketing material either in the form of' compressed fibre sheets or woven cloth-. Compressed fibrejointing was invented in 1886 by Richard Klinger. Since that time asbestos jointing has been increasingly used for many gasketing services and today every engineer is familiar with the. use of this material. . The best, grades' of jointing are made of long chrysotile fibres, which, after cleaning and opening, are compounded with binding agents and vulcanised under pressure into a.homogeneous structure. Compressed sheets consist usually of 65--80 per cent of fibres; the remainder is a binder or compounding agent. Natural rubber. Neoprene, Buna S and other synthetic binders are .used, compounded with plasticisers, anti-oxidants, etc. The first step in manufacturing this material is the cleaning and opening of the dry fibres. Particular attention should be paid at this stage to the elimination of hard fibre bundles and various mineral impurities* and at the same time care must' be taken to avoid excessive fibre breakage. The degree ofopening or fiberisation depends bn the use ofthe final product and the softness and density required. Well opened and cleaned fibres are mixed with the correct proportion of rubber and other mineral ingredients to a dough-like consistency and rolled out in calenders, where heat *A.S.T.M. definition. . . ' ' OTHER INDUSTRIAL USES OP ASBESTOS 273 ives off the solvent and the action of the rollers compounds the nstituents into a compressed homogeneous sheet. The finished sheet- acquires a " grain " and possesses a greater isile strength in the circumferential direction of the calender llers. In order- to improve the low tensile strength against the ain, two sheets are laid at right angles to each other and cemented jether. Such " cross-laminated " material has a similar tensile ength in all directions. Besides chrysotile, "blue" asbestos is also used:.as a jointing iterial in chemical and industrial plants where resistance to acids of primary importance. In general, the three types of jointing at are made are (a) plain, (A) coated with graphite on one or th sides, and (c) reinforced with brass, copper and steel mesh. Depending on the compounding, they are used for superheated ams, air, acids and alkalis, gas, water, oil, and in fact for most ier liquids. A quality ofmaterial intended for high duty (Grade G) >uld have a tensile strength exceeding 5,500 lb. per sq.in. with tin, and 2,000 lb. per sq.in. across grain, as frequently the ength of the material limits its applications*5. ' Fig. 122 Asbestos jointing Low duty purposes 3,000 and 1,200 lb. per sq.in., respectively. 274 ASBESTOS (Test sample 1 in. wide, 4--8 in. long, A in. duck, rate of traverse 9 in./min.). ,. Tearing strength may also be specified by various users of this material to suit their own requirements. The ignition loss in weight of the material on exposure to 850^3. serves also as a further check of quality: if it is greater than 30 per cent, it may indicate that the strength was increased by the excess of the rubber compound. '..' The specific gravity, test indicates whether the material is insufficiently compressed or, if the figure is high, whether too high a proportion of fillers was used in compounding. A specific gravity within a range of 1*65 to 2*0 is considered^normal. It must-be realised however, that all these tests give a general idea only and do not preclude the serviceability of the material in certain appli cations, even when the test results are outside the specified limits already mentioned. The performance of the material in actual conditions of use is the best criterion of its value. .. WOVEN CLOTH . Woven cloth as gasketing material is preferred in such cases where softness and pliability are most desirable. It is normally woven from asbestos yarns reinforced with fine brass .wire, and usually contains from 10 to 20 per cent of organic fibres, added to. aid tiie carding and spinning processes. Such addition of organic fibre decreases the heat-resistance properties of the woven doth and- their amount should be kept as low as possible. Because the woven fabrics are porous they are impregnated with either rubber or plastic compounds. . . .. . For boiler handholes and mahhoies, plain or metallic asbestos doth, treated with heat-resistant rubber , compounds is used. It is folded* formed and pressed to the required size and shape; Besides chrysotile fibres, blue " asbestos is also, used and the cloth made from it is treated with neoprene cement and serves against strong mineral adds, oil and organic solvents. . TADPOLE TAPE . ;. This is made of asbestos doth wrapped over a core of asbestos wick, rope, rubber tubing, etc., depending on the size and softness required and on the service conditions. Tadpole fjrewall seals arfe. made with cores of incond mesh or with synthetic rubber fdrhot places. Tests show that they resist penetration by a 2000F. ffiiine- and continuous temperatures up to 500F. .. . RUBBER GASKETS Natural rubber is mpsdy used, for hot and cold .water where its OTHER INDUSTRIAL USES OF ASBESTOS 275 elasticity and ability to adapt to any surface imperfections are generally appreciated. Several synthetic rubbers like Buna S, Buna N, Neoprene, Butyl, Thiokol, are used for sealing against oil. Recently developed silicone rubbers possess outstanding heat- resistance properties, and find application, alone or with asbestos reinforcement* as a gasketing material among other uses. (See also " Silicone Rubber " in Chapter 13). - Several plastic materials are used in the manufacture,ofenvelope* type and moulded-shield gaskets. Teflon (tetrafluoroethylene polymery and Kel-F (chlorotrifluoroethylene polymer) are most prominent* due to their resistance to heat and complete chemical inertness (see also Chapter 13). '. METALLIC GASKETS .. .The most important factors that influence gasket selection are the temperatures and corrosive effects to be encountered. Non- metallic gaskets are generally limited to temperatures below 400PF. Semi-metallic gaskets made of asbestos and partially or completely dad' with metal may be used up to 850F. Above 850F., only all-metal gaskets are satisfactory; A wide variety ofmetals are used- including lead, tin, aluminium* copper, brass, monel, nickel steel and even silver. . . . In addition to metals, organic fibres in.the form of treated paper and leather either alone or impregnated with rubber, are also teed for gasketings. . New products or improvements are constantly being made and . one of the latest worth mentioning is the combination of asbestos- metal-resin. .This new product, made by Lancork Ltd., is manu factured, for the specific purpose of providing a gas, tight seal for internal-combustion engine cylinder heads, exhaust flanges and manifolds6. One particular feature of this material is that when the engine heat causes the resin to flow and the gasket is compressed, the asbestos moulds itself to the two surfaces, and becomes impreg* nated throughout With resin and rock-hard, thereby ,giving the. asbestos a greater strength than would be passible if the heating and compressing occurred , prior to fitting the gaskets. Further strength is obtained by interleaving the asbestos with , copper or ahimiruiun for every A m* of sisbfestos. . . . Recently a new type of cylinder head gasket was. developed. This is made from a thick sheet of aluminium washer with an aluminium foil lamination on each/side. It is claimed , that these gaskets are superior to the conventional copper and asbestos types because of their better thermal conductivity7,8. L_ 376 ASBESTOS Fig. 123 Fitting ofAsbestos Gaskets OTHER INDUSTRIAL USES OF ASBESTOS 277 * \ BIBLIOGRAPHY . 1. Good Gasket Practice. W. F. Schaphorst. Asbestos, 1951, 33, No. 3, 8.. . 2. Gaskets and Their Selections. W. F. Schaphorst. Asbestos, 1950,32, No. i, , 18--20.. 3. ; Asbestos, Its Reparation and Application. A. E. Williams, Mechanical World Monographs 47: 1948. . * 4. Gaskets. S. Elonka. Tower, 1954,98, No. 3,105--124. . 5. Compressed Asbestos-Jointing for tite Petroleum Industry. ' British Standard No; 1832: 1952. .. 6. Langcork Company Ltd., 8, Ajax Crescent, Cambridge, East London, - S. Africa, (private communications). ' 7. De-rating Gaskets. Anoxi,AutomobUc Engr. 1953,43, No. 564, 112. 8. B.P. 721,475. Improvements relating to the Production of Metallised Laminated Jointing Materials. Turner Brothers Asbestos Co. LSxtitpd. CHAPTER 17 Asbestos, Trader ASBESTOS TEXTILE INSTITUTE the asbestos textile institute with office and laboratory at the Philadelphia Textile Institute, Philadelphia, U.S.A., serves the affiliated'.members of "the industry through its many specific- committee activities and those projects, pursued in' the/ general interest of the industry. -: The organisatipn of the Asbestos Textile Institute is directed, by die Board of Governors consisting of the following officers and members:--F. J. Wakem, Johns-Manville Corporation, President; J. A. Bettes, Raybestos-Manhattan, Inc., Vice President; J. G. Schoepf, Asten-Hill Manufacturing Company* Treasurer; R. S. Hul&e, Southern Asbestos Company; G. W. Marshall, Jr., Ray bestos-Manhattan Inc.; A. J. Scanlan, American Asbestos Textile Corp.; and D. W. Widmayer, Keasbey & Mattison Company. Dr. M. G. Shaw serves the Institute as Executive Secretary and Director of Research. . . The membership of the Asbestos Textile Institute consists of six asbestos textile manufacturers located in the United States, four asbestos fibre mining companies located in Canada* three asbestos textile manufacturers located in England, two asbestos' textile manufacturers located in France and one asbestos fibre mining company located in Africa with offices in England and the United States. There are four ftmetioning groups or committees within the. Institute* each concerned with different aspects of the industry and each carrying on studies designed to Improve or develop that segment of the industry in which it is particularly interested. The Air Hygiene sefction is engaged in important investigations relating to dust control and elimination in the manufacturing operations involved in this, industry and in studies designed to determine the hygienic and physiological effects resulting from exposure to various dust conditions. The Sales Promotion Committee is continually engaged in ASBESTOS TRADE 363 efforts to promote the use of asbestos textiles and in investigating and initiating new applications for the materials produced by the industry. Industry-wide improvements in quality and serviceability are the aims of this section of the Institute, and consumers are becoming increasingly aware of the fruits of the efforts of the group. The section works closely with the Technical Committee and the Research Fellow in seeking the solution to many of the .problems with which it is confronted. The Technical Committee is continually investigating thejnany problems involved imimproving the quality of available materials, development of new materials and in devising new and improved methods for testing and evaluating results. : The Fellowship laboratory under the direction of Dr. M. C. Shaw serves all of the committees in their many investigations and provides technical assistance whenever necessary. In addition, there is conducted by the Fellow an extensive research programme as established by a special committee of the Institute. The activities of the Asbestos Textile Institute are continually expanding and the efforts exerted through the participation of the membership in the programme encompassed by the several specialized sections of the organisation serve to provide the industry with an ever-increasing fund of knowledge regarding the products of the industry. With this increased understanding it is felt that the industry will be in a position to continue' to expand and to meet the demand for the new and improved materials which will be required by the engineers of the future. .