Document v68dx6er7m5JDpQ52VKDaVzY6

.i ( 1713 Norasber V, t037 A STUDY OF DUST CONTROL METHODS IN AN ASBESTOS . . FABRICATING PLANT By Richard T. Pace, Amstant Public Health Engineer, nd J. J. Bloomfield. Patted Attuiant Sanitary Engineer, United State* PubMe Health Service An extensive medical and engineering study of the health of asbestos workers has been conducted by the United States Public Health Service (J). The material contained in this paper supple ments the general study with a detailed study of the dust control methods used in an asbestos fabricating plant. It is a report on present conditions and how they have been obtained and is presented as an example of the results of the application of scientific methods of dust control. 'Thes data should be interesting not only to the asbestos industry but also to other industries having similar dusty processes. The plant studied has only partly completed an extensive dust control program, and conditions are being improved continually; consequently, these results should not be interpreted as representing the maximum possible efficiency in the control of asbestos dust, but it is believed that they are representative of the best practice in tliis country at this time. The dust control systems in use with the vari ous processes in each department are described. An occupational analysis of employees is presented, with a comparison of the atmos pheric dust concentrations associated with controlled end similar uncontrolled processes. ' EABBICATtOX or ASBESTOS TEXTILES Asbestos is the class name for several different fibrous minerals, but the asbestos of commerce (1) is mainly the fibrous form of ser pentine known oo chrysolite.1 Duo to its fibrous nature, ilexibility, and heat-resistant properties, asbestos fiber finds mnny practical applications. One of its important industrial uses is in the manu facture of fire-resistant textiles. In the plant studied, practically all raw material was crude Canadian or South African asbestos. Some imported short fiber was used, as well as some of the short fiber salvaged in the recovery process, but most of the short recovered fiber was shipped to other plants. Signif icant variations in atmospheric dust concentrations due to the grade of fiber being processed were not evident in controlled processes in this plant. Consequently, the type of fiber used has Dot been con sidered in the analysis of the duta. Each dust controlled process tended to decrease the amount of dust generated in subsequent i CirysotU* Is s brCrous auesasiua suiutt (EXiMqSIsO, or UliO-JJJirO.lSiO,) containin* M.l par. wot Allies* 43.0 perat rn^n-nim. And 119 parasol wnicr. Otbcr Xjim of 13bastes oft&Q oontula alliestas of too, calcium, ldc! aiun^aam as iraii u cscmoiitua (f). . Pctbho lieoatSHepoft SZj /?7 i * NoTwnber J8, 1017 1714 processes. These factors must be considered when comparing dust concentrations reported in this plant with the data which have been reported for other pinuta. -. Approximately 300 persons were employed in this plant, of whom 180 worked in denartments having a potential asbestos dust hazard. This study was confined to those departments; namely, preparation; carding; spinning, twisting and winding; and weaving. The occupa tional distribution of exposed workers is shown in table 1. Tabu !---Occupation* and dust expoturet of loorkan in an asbetiot textila plant tfao. u. r. re.onoc.orji.tr*. WIthoot ex> NOttMl bust rcaU- ItllOB 1tDouasptleexahaftuesrt1shrsotearra1!* for this operation. operation irithoatexhaoct. Sample uum Inside bin during leading. II ~ TH" m >#.7 **> 10.0 ' L7 *4.0 . 1.7 '814 40.4 17 .1 ------------ ----- . A0 >10 At 11.0 18 10 '.7 1 11.70 LI 11 l. M U.0 / - ' - METHOD OV STUDY * This investigation included a study of atmospheric dust concentra tions in the factory workrooms and a study of the exhaust systems used to remove asbestos dust. Eighty-two atmospheric dust samples wore collected at the workers' breathing level with the impingor dust sampling apparatus (d). Sixty-nine of these represented present working conditions and 13 represented conditions whiie exhaust apparatus had been turned of? for 1 hour. A collecting ineuium conta.uing 25 percent ethyl alcohol in distilled water was found to proveat flocculation without causing excessive evaporation in either tho sampling flasks or the counting '1 - 1: cells. All samples were counted the low dust concentrations eacot seated the dust in from 20 to 3( diluted with distilled water and c technique described by Bloomfield eyepiece having an engraved sq standard Whipple square was use to count only one quadrant oi th sample (0.25 cubic millimeter) pe The quantities of air t smoved i were calculated from pit t tube n in the pipe lines (4). Average e? table 2 and discussed a little later; Entrance velocities at open ho< velometer and checked with a vs were of the enclosed type designe vent the escape of asbestos dust ir measurements were impractical, hood were calculated from me Whenever differences in exhaust hoods on the some operation, the DESCRIPTION OP PROCESSES Asbestos is received in burlap Cotton is received in standard hoi used in the preparation of asoestorage,-and .transportation oi hazardous occupations. The pn to completed fabric is shown by : vidual processes and the measure: -. PBEPAXATK Crushing.--Some of the usbsst crushed" fiber, but most oi the c other than mining, sorties', and dumped from the bags into rhi-\ 15 minutes. These crushers ha radial axle, and revolve on a smcc is placed. During the crushia stirred by revolving scraprs. replaced in the bags and enme were not enclosed or tiou in the preparation denartr concentrations of dust near cL \ jf- i. 1715 KmmtMT M, 1837 '+ # fpjln. All samples wore counted the day alter collection. Owing to } */i* the low dust concentrations encountered, most of the samples repre sented the dust in from 20 to 30 cubic feet of air. Samples were diluted with distilled water and counted according to the light-field technique described by Bloomfield and DollaVaUo (3). A micrometer A .<-- eyepiece having an engraved square equivalent to one-fourth the standard Whipple square was used in counting. Since it is customary to count only one quadrant of the Whipple field, the same volume of sample (0.25 cubic millimeter) per field was counted (7). b` The quantities of air removed through the various exhaust systems were calculated from pitot tube measurements of center-line velocities in the pipe lines (4). Average exhaust rates per process are listed in l:rt table 2 and discussed a little later in the description of exhaust systems. Entrance velocities et open hoods were measured with an Alnor vdometer and checked with a vane anemometer. Most of the hoods were of the enclosed type designed to exhaust only enough air to pre vent the escape of asbestos dust into the workroom. Where individual measurements were impractical, air volumes exhausted through each hood were calculated from measurements of main-line velocities. Whenever differences in exhaust volumes were noted between similar hoods on the same operation, the average value is given. . DESCRIPTION OF PROCESSES AND DOST CONTROL MEASURES Asbestos is received in burlap bags containing 100 pounds of fiber. Cotton is received in standard bales. These are the only raw materials used in the preparation of asbestos yam at this plant. Unloading, storage, and transportation of the packed raw materials were not hazardous occupations. The progress of the material from raw fiber to completed fubric is shown by means of a flow sheet (fig. 1). Indi vidual processes and the measures for dust control are described below. , ' FBEFAEATION DEPARTMENT Crushing.--Some of the asbestos fiber arrives at the plant as "pre crushed" fiber, but most of the crude fiber has received no treatment other than mining, sorting, and screening. This latter type is hand dumped from the bags into rim-wheel crushers and crushed from 5 to "t - 15 minutes. These crushers have two heavy rollers attached to a radial axle, and revolve on a smooth-surfaced tray in which the asbestos is placed. During the crushing, the asbestos fiber is constantly stirred by revolving scrapers. After being crushed, the fiber is replaced in the bags and carried to the asbestos opener. Crushers I wore not enclosed or exhausted in any wuy, but the general ventila tion in the preparation department was sulficient to prevent high concentrations of dust near this operation. Crusher men had res- I'O i .. ). ii . -:i 1 ' ij NorarnHarm 1M7 1716 RAW materials ICOTTON CRUDE ASBESTOS IasTestosI | CRUSHERS] RECOVERED MATERIALS KOVfNO WASTE CYCLONE i SETTLIN'0 CHAMBER WASTE C.VSMOUSfl WASTE 'C6tt6n' OPEMER9 Ag3>ST0S OPENEPS RC VING 8 VIBRATING SCREEN RfcCJPENER VibrAti SCREEN e i Asbesloe opening and terten bags to the floor beside the * lattice hopper with wooden n design were in operation, but Ft same on both. (See schen hopper was partially enclose A second hood exhausted tfc bottom of the opener (hood t hood C and pneumatically t: the fibers were remo, ed and o A large portion of ti . dust an STOCK BINS jCcARoiwa dept.)] JD wickins cards TWISTED CORD MACHINES I ROPE TWISTING MAOHINES i 1ROVINS PAROS MULE SPINNERS (RING SPINNERS 1f FOSTER WINDERS (SPOOLERS) CHEM. TREATMENT ft BRAIDING DEPT. COP WINDERS nTWISTERS LOOMS (universal] WINDERS ' CHEM.TREATMENT RU08ER "DEFT. ** 1--..............-- MARKET NOTE; UNDERLINED PROCESSES HAVE OUST EXHAUST SYSTEMa Fiat,'*s L--ttoetm Jiow-*bst, MtU! pJuL. pirators 2 and usually wore them while loading or unloading the crushers. The average exposure of a crusher man tending three crushers was 3.5 M. P. P. C. F. AB aoplerwi ta IS* rrerention d*prtiE*3t sod sli rspslncen sod jinitan were prortdad with rwplrv tsasfstrvsspprarwl by ih U. A. UurettitfMuiM union high coccectretieci or Cwiiuicsdtui. t< - ;*>.f t 4 4 4 ;V "TS' noou S.--SchtmaUe iew at was removed by hoods A ar pieces ot rock too heavy to be fell onto an enclosed belt coi carried to the recovery proersi Exhaust volumes through t 400 cfm; hood B, 400 cfm; Lc conveyor velocity, 2,730 feet: Each opener Luu its u ,vn i hausted vibrating ,->cm>n. Q beside the charging hopper u t' 1717 Nerwnbac 2ft, 1S37 Asbestos opening and screening--Tha crushed fiber is dumped from bftga to the floor beside the asbestos openers and lilted into the feed lattice hopper with wooden hand forks. Two openers of different Resign were in operation, but the method of exhaust hooding was the same on both. (See schematic design, fig. 2.) The feed lattice hopper was partially enclosed and exhausted at the top (hood A). A second hood exhausted the bottom ily and settled dust from the bottom of the opener (liood B)^ The opened fiber was picked up by hood C and pneumatically transported to a cyclone separator where the fibers were removed and dropped onto an enclosed vibrating screen. ^ }orgo portion of the dust and fine fibers entering the asbestos opener ' i; Was removed by hoods A and B. Clumps of unopened fibers and pieces of rock too heavy to be lifted by the pneumatic fiber conveyor fell onto an enclosed belt conveyor serving both openers, and were famed to the recovery process. (Belt conveyor is not shown in fig. 2.) Exhaust volumes tlirough the hoods were as follows: Hood A, 4QQ cfm; hood B, 400 cfm; hood C (pneumatic conveyor), 1,800 ci'm; fpnyejor velocity, 2,730 feet per minute. Each opener had its own cyclone separator and enclosed and ox- ||austed vibrating screen. One screen had two exhaust hoods, ono beside tho charging hopper drawing 400 cfm and ono over the tLis- \ i, 4. t V i Konmbar S3, 1037 . 1718 * charge end of the screen and the stock car, drawing 770 cfm. Tha second screen had ono imod only, over tho discharge end, drawing 010 cfm. Short fibers and rock particles passing the screens fell through a chute to the enclosed recovery conveyor. Fiber failing to pass these screens dropped into a stock car. Full stock cars were pushed to a platform scale and then to the mixing beds. , The sume men charged tLo openers and filled the stock cars. The average dust exposure of asbestos-opener operators was 3.6 M. P.P. C. F. Cotton' oveners.--The best grades of insulation contain very small amounts of cotton, if any; but in all other cases, cotton fiber is mixed with asbestos fiber to improve its spinning qualities. At this plant the batch seldom contained more than 15 percent of cotton by weight hut as much as 20 percent cotton was used in lower grade jams. The - two-stage Suco-Lowell cotton opener was provided with exhausts at three points; 770 cfm of air were exhausted through a canopy hood over the feed lattice, 270 cfm from the bottom of the primary opener, and 1,120 cfm from the bottom of the secondary opener. Opened cotton fiber was discharged into stock cars. No samples were taken at the cotton openers, but the operators' averago exposure was about 2.4 M. P. P. C. F. (general air, preparation department). . Mixing.--Weighed quantities of asbestos and cotton were placed in alternate layers in the mixing beds. Occasionally, layers of rov ing waste from the carding room were reopened and added to the bed. Mixing was done in six "exhausted" booths, each 10 feet 2 inches deep by 6 feet 10 inches wide by 6 feet high. Sides of the booths were permanent, while the back consisted of a removable wood and canvas section. Each booth was covered by a pyramid hood 32 inches high, through which approximately 1,025 cubic feet of air per minute per hood were exhausted. The velocity of air motion into these booths averaged 50 feet per minute during bed making and about 30 feet per minute during picker loading. Dust concentration averaged 5.4 M. P. P. C. F. for the bed-making operation. After a bed had been placed, the picker operator removed the rear partition of the booth and forked tho batch into tho charging hopper of a picker (fig. 3). The picker machine mixes the fibers in revolving beaters. The four machines represented three different operations and two different types of exhaust systems. The first machine, not in operation during this study, discharged mixed liber into a stock car. This material was then passed .through a second picker for remixing. The second and third machines discharged mixed fiber onto a belt conveyor which transported it to bins in the carding room. The product of the fourth picker was curried to the carding room by a pneumatic conveyor. Each of tho first three machines had a hood over the charging lattice, exhausting -approximately 500 cfm, a pipo exhausting about 1,(150 cfm from the bottom-fiy settling chambers I I 4 I ti S S. -Js~ .v ' fea. Ftta'its 3.--r Xc S5VH Fim-ag i--Flhcr nvovrry j-n. * f I I trollh Rfporti. Vi. iJL No, 4*. Nmnwinr 2*. l*7 Plate I i under the main picker drum, a * lattice exhausting about 400 < H hood arrangement ove r the ci exhaust, and the mixed fiber v exhausting approximately 2.00 per minute. Tito picker otters lug operation. Dust concent from 4.0 to 9.5 M. P. P. C. Fv * Recovery processes.--Waste i > to the preparation d'partmer 4 was exhausted only f >m the cfm of air drawn through th escape of dust through the ah . The dusty air collected by i. and carding department was * occupying two stories in the e placed from this room to a b. the other end of this building, stretched on A-framea, lhe . during the noon rest period, the week end shut-down, andi 'V tt ment. Bag-house dust was t exhausted vibrating screen were removed to a cyclone co dust from tbe settling chamb . dust, and fibers separated by spooling operation and the we - a fly-willower and vibrating s- of air were exhausted from the from the discharge side oi the dropped onto an inclined tray drawing 730 cfm. Fibers whi removed by tbe hood at the L pneumatically conveyed to a purities not picked up by the f below the end of the screen limited, and such fiber is us textiles. Consequently only through this process. Averse at between 3 and 5 M. P. P. C As a measure oi the effectiv preparation department, rhe - Pneumatic conveyors rcm&uit increased steadily to about 50 haust fans were turned on. Ty,')1;a,i 1 jj.iij ijii y. 1 . . 'TTTT . "7. <.. -i* r 'Vi- . ,V- .. *t -t 1719 * under the main picker drum, and a hood over the end of the discharge lattice exhausting about 400 cfm. The fourth picker had the same hood arrangement over the charging lattice but had no bottom-fly exhaust, and the mixed fiber was removed by a pneumatic conveyor exhausting approximately 2,000 cfm of air at a velocity of 2,550 feet per minute. Tho picker operators wear respirators during the charg ing operation. Dust concentrations during picks* charging varied from 4.0 to 9.5 M. P. P. C. F., averaging about 6.7 M. P. P. C. F. Recovery processes.--Waste roving from the card room was returned to the preparation department for reopening. The roving reopens was exhausted only from the pit below tho last beater, but the 1,780 cfm of air drawn through tills hood were sufficient to prevent the escape of dust through the discharge lattice. i The dusty air collected by the exhaust systems in the preparation and carding deportment was blown into a large settling chamber occupying two stories in the end of a separate building. Air was dis placed from this room to a bag house occupying the second floor on the other end of this building. Dust was filtered out by burlap filters stretched on A-frames. The filters were beaten down by hand daily during the noon rest period. The collected dust was removed during the week end shut-down, and stored in bins in the preparation depart ment. Bug-house dust was screened on a completely enclosed and exhausted vibrating screen (background, fig. .4), and the long fibers were removed to a cyclone collector by a pneumatic conveyor. The dust from the settling chamber, the long fibers from the bag-house dust, and fibers separated by cyclones on the exhaust lines from the spooling operation and the weaving department were passed through a fly-willower and vibrating screen (fig. 4). Approximately 250 cfm of air were exhausted from the top of the charging lattice and 620 cfm 1: from the discharge side of the opening drum. Dirt passing'the screen i dropped onto an inclined tray and was removed by an exhaust hood drawing 730 cfm. Fibers which did not fall through the-screen wore removed by the hood at the lower end of the screen (1,710 cfm) and pneumatically conveyed to a cyclone collector. Bock and other im purities not picked up by tho pneumatic conveyor fell into a waste box below the end of the screen. The market for recovered fiber is limited, and such liber is usually too soiled for use in high-grade textiles. Consequently only part of the collected dust was passed through this process. Average exposure of operators was estimated at between 3 and 5 M. P. P. C. F. As a measure of the effectiveness of the dust control system in the preparation department, the exhaust fans were shut olf for 1-hour. Pneumatic conveyors remained in operation. Dust concentrations increased steadily to about 50 M. P. P. C. F., at which time the ex haust fans were turned on. Tho samples taken during this period f` *.f - I * O-,. 'V' - :; vyV.; . V & \ b I* t- ' KtnmM M> 107 1722 The volumes of air exhausted through each hood were estimated os the basis of pipe areas. Actual volumes showed wide variations on different units. Single cords were used in the manufacture of asbestos wick and rope, since a tliick rowing was desired. The wick or rope was twisted from the unspun roving. The wicking cards were exhausted at three points. Approximately 330 cfm of air were drawn from under the feed lattice, 490 cfm were exhausted from the top of the main cylinder cover to remove the top fly, and 550 cfm were exhausted from the bottom- fiy settling chamber. ' Dust concentrations during carding averaged 1.7 M. P. P. C. F. This was also the average exposure of wicking coni operators and wick and rope twisters. Samples token near the carding department weight scales showed less than 0.5 M. P. P. C. F. -- Card rolls "were cleaned and ground at night, except in cases of emergency. Cleaning was done with hand scrapers made of strips of card cloth, and the card cylinder was turned by hand. Grinding was done with the usual type of card grinders. The large roll was ground in place in tho carding machine. Slightly greater quantities of air were exhausted during grinding due to the decreased loss of head resulting from removal of the wooden card covers. The small card cylinders were ground in a grinding frame. These frames were partially enclosed and covered with a canopy hood exhausting 2,330 cfm per grinder. Dust concentrations averaged 0.65 M. P. P. C. F. during grinding. A special run of a group of carding machines made with all exhaust ventilation turned orf and windows closed showed that dust concen trations steadily increased. At the end of 1 hour the concentration was 62.4 M. P. P. C. F. in the air. Under normal operating conditions about 64,000 cfm of air are exhausted from tho carding department. This is equivalent to about 5.5 air changes per hour, disregarding natural ventilation through windows on all four sides of the room. Spinning, twisting, and winding.--The yam as-roving is twisted or spun into compact threads on either mule or ring spinning frames. In this plant most of the spinning was done on mule spinners. The spun tliread was transferred from tho spinning spindles to spools, on Foster winding machines (spoolers). Spooled thread to be used as filler (or woof) in woven cloth was rewound on a cop winder into cops which will fit into the loom shuttles. Tho remaining spooled thread was respooled on twisters which twist several threads into u yarn. The number of strands used determined the size of yarn. Both plain and metallic yarns * ere twisted. Metallic yam contains one or more strands of lino wire. Pert of the twisted yam was used in cloth weaving while the remaining yam was rewound on Universal winding frames for the market. . Mulo spinning was separate 1> meat by partial partitions, Sf*- exhaust systems were used. 0.85 M. P. P. C. F. with a ma Ring spinning, cop winding, located in the same room wit posures in the first three or especially dusty, were due to c the exception of & trial exhau. - - machines were not ; rovided reported to be satis ictory i J' -rv X~ tlOV*M S.--SohMBiit.a machines. In this system, ti enclosed and a total of 1,700 c: ward past the twisting yarns ns along a central exhaust duct. Average dust concentrations were ring spinning, 5.0 M. P. P Universal winding, 2.8 M. P. C. F., with & maximum of If twisting frame. So accurate exhaust system on the single <?simultaneous samples on boil it- -V 1723 tfen.ab"rM, IWT * Jtfille spinning was separated from otlieF operations in this departpistil by partial partitions. Natural ventilation was good and no 'fbapal systems were used. The ayeraere dust eoneentration was jM Mt Ft ? C, F. with a maximum of |.S M. P. F, O. F. recorded. Ring spinning, cop winding, am| llntywrenl winding machines were iecsted in the same room with the twisting machines. Average exposi|res in the first three operations, which were not themselves especially dusty, were due to dust from the twisting operation. With |i}S exception of a trial exhaust system on one twister, the remaining fg&ehines were not provided with exhaust. The trial system was lepefled (9 b iftliefect&ry mi i fee instated ea tU twtm| c fKWt* *-=Sc>*ranti *ks af anu^st ^kUp apptiad ta fMt viaden. WftfMntS-. Id this system, the bottom of the twisting frame was eBlostl fthd a total of 1,700 ctm of air jw machine was drawm down* ffiii fWt the twisting yams and through five conical hoods distributed ikfff ft peptrai exhaust duct. 4wsg dust concentrations at the tpwua operations in this room fF Hf8 spinning, a.U M. P. P O, f, i cop winding, 0,tt Al, J*. P- C. F.; SMVftill1.} ^hiding, 2.3 Al. P. F. O, F.; and twisting, 11.0 Al. I*. P. 3. f., with a maximum of 13.3 Al, P. P. C. F. recorded hesi.lo a frame. No accurate measurements of the eOieiency of the system on tlta single exhausted twister could be secured, but imuUancoua samples on both sides of this frame showed a dust' I' ' `f I JfercmbarMlu 1724 concentration of 18.0 M. P, P. C. F. on the side toward the unex- * hausted twisting frames and a concentration of 6.3 M. P. F. C. F. on the other side. - Four Foster winders (spoolers) were partially separated from the ether operations by partitions (fig. 6). The exhaust system con sisted of an individual conical hood around each spindle holder (fig. 8). Approximately 46.5 cfm were exhausted through each hood, or a total of 9,270 cfm through the 200 hoods on the 4 spooling frames. - Dust concentrations at the spoolers averaged 2.9 M. P. P. C. F. and increased to 9.6 M. P. P. C. F. within 30 minutes after the ventilation had been shut od. WEAVING AND INSPECTION Cloth, tape, listing, and brake bands were woven on different types of looms. In this plant, exhaust systems had been applied to the dry cloth looms, since those were considered to he the most important source of dust. The dust control program calls for installation of exhaust systems on dry tape, listing, and brake-band looms. At present these operations are mainly performed wet or partially wet. Brake-band looms were not in operation during this study. Signifi cant differences could not be noted between dust samples collected around the various tape and listing looms. Dust concentrations ranged from 1.2 to 4.0 M. P. P. C. F. and averaged 3.0 M. P. P. C. F. Nineteen doth looms were in operation in this department One of these was a wet loom not provided with exhaust hoods, 4 were dry looms provided with exhaust hoods, and the other 14 were so provided but could be operated either wet or dry. A loom without exhaust hoods is shown in figure 9. The exhaust system is shown schematically in figure 11. A double exhaust hood drew air from under the warp while a second hood was attached to the top of the loom lay with exhaust ducts running down the side of each picker arm to an airtight swingjoint at the bottom. The openings in the loom-lay hood consisted of four dots mne inches long by 1 inch wide extending over a space of 4 feet across the woven fabric at right angles to the warp. A total volume of approximately 10,500 cfm of air was exhausted from the 18 hooded looms. This averaged about 580 cfm per loom; but since it was seldom necessary to operate more than 10 dry looms at one time, the average quantity of air exhausted was close to 1,000 cfm per loom. Exhaust dampers were provided on all looms, and a sufficient number to balance the system arc closed on wet or idle looms. The average dust exposure of a weaver operating a dry loom with exhaust was 0.7 M. P. P. C. F., v.iule the average exposure in wet weaving wiiiiout exhaust was 2.G At. P. P. O. F. Samples taken beside a diy loom without exhuust allowed dust concentrations ui O.ii M. P. P. C. F. ... It ! i * r *r r t ft*i> tikl R*i~u. VU il. No. w. IWto *. l'*B Plat* hi g r*yys \- yffwgw; ? 'h. t 'v^yrrr. after 45 minutes. Average d have been shown as 49.7 M. ] . Woven cloth was inspected, tion table shown in figure 10. 'j - f f V, Fiovii IS*--GcbiE*Uc riw* partially enclosed and exhauste drawn through each of tho tw about 200 cfm were drawn thr . 21481'--ST----- S 1725 Nowmbor 38, 1837 after 45 minutes. Average dust concentrations during dry weaving have been shown as 49J M. P. P. C. . (5). Woven cloth was inspected, brushed, and calendered on the inspec tion table shown in figure 10. Each of the power-driven brushes was IHIU U.--6fhemute (leal of ubiaa ijMem ippliod to brood looms. partially enclosed and exhausted. Approximately 750 efra of air were drawn through each of the two hoods at tho front of the tabic and about 200 cfm were drawn through the cleaning hood at the back of -1431*--37------3 \ ae {Eywr - * *.-*' . - T" . f't..'?*....!..*..*...* V- 't. V1-1**` v:." r.`? t ......... * Kotiksbar X, 1W7 1726 * the table. ' Dust rnncMitratioiiH during inspection nvoraged 0.5 i M. I\ P. C. F. A sample taken while a roll of fabric was passed Table 2 gives-a summary of across the table without benefit of exhaust showed a dust concentra as > hating the number of exhaust tion of 11.8 M. P. P. C. F. machine, as Well as the average Doffing, inspection, and calendering of tapo and listing were hand are exposed. Average dust operations and were not provided with exhaust. Dust concentrations aponding operations without e of 5.0 M. P. P. C. F. were recorded during these operations but the tiveness of the control methods exposure was intermittent. Creelera had an average exposure of about 1.3 M. P. P. C. F. while placing spools and threading looms. . c< An exhaust of 12,200 cfm of air was provided in the weaving de This study of actual results; partment, corresponding to approximately three air changes per hour. asbestos fabricating plant is p In cold weather, warm air was distributed through the department from a plenum system, while in warm weather natural ventilation was '.tt: control of an industrial hazar published to justify the detern secured through use of windows on all four sides of the department. which will produce as'aestosis OTHEB OPERATIONS absence of such threshold valut v aible limit? of dustiness on a m Other operations in this plant consisted of processes in which the dable decrease in the amount < yarn was chemically treated and fabricated, or processes for chemi the incidence and severity of cally treating or rubberizing fabricated cloth. No potential asbestos hazard was associated with these processes, with the exception of one tion of all the dust in an indus a physiological standjpoint an braiding machine used to make large diameter asbestos tubing. This Consequently, actual atmosph machine was covered with a coniad canopy hood about 6 feet in from the application of practic diameter, which provided an exhaust of approximately 200 cfm of as temporary standards by tl air. A sample taken beside this machine showed a dust concentration of 0.4 M. P. P_ C. F. at the operators' breathing level. B- Table 2.--Volumes o/ air exhausted per machine in carious operations in an asbestos textile plant . Operation Conneelions Total volume of air hausU per miout* (ca. fl./min.) Dust concrn* trailon with fthaust, M.P.F.C.F. Dust ennrt'ntmtlon -a ab out exhaust. M.F.P.C.F. Jkihestos opener..........-- Vihruiia* serren.. ___ --- ---------- Cotton np''iu*r i........1,,, r- ------------ - Mitlmt beds------------- ------- ------- ------------- Mdtcr............................................. XtovinK roopener............ -- _ ------__ --__ ___ Boeing cards: Breaker (primary)-----------------------.....----------- Fjabber______________ - --_ WtekiiutcirU......-------- . -- .-- Twlslfti............. ........... ..... Wmvlng (broad looms)... BruilKf--C slenderer ....... . ___ .. <2 1 5-1,000 TOO } 3 3*100 1 1,0-5 3 2,570 1 1,700 *1 1.000 3 I, <20 1 4 3 1. M0 1,43) Ir 1 xm *| 21 1.7WI 1,300 3 1,660 At 11.1-340 ............. 6.4 3.1-iO.# 6.7 I 31.3-74.1 ______.... n n 4 .7 Z6 is i 11.0 \7 U.7 .3 as (/) Ries, H., and Watson, T. L.: Ino., New York. 1037. (S) Fulton, W. B., Doelev, A., > Fart II: The nature and amouiit plants. Spec. Bull. No. 42, Penns 20 1935. (S) Bloomjcld, J. J., and Dal'.-Y industrial dust. Pub. Health Bull. D. C. 1935. (4) Harding, L. A., and Willard tioning. John Wiley and. Sons, It IS) unpublished data. United (0) Higgins, E., I f.nza, A. J., La relation to pulmonary disease arm Bull. 132, U. S. Bureau of Mines. 1 (7) Page R. T.: Note on a new Pub. Health Rep., Six 1315-1316. I Equipped with poeumittet*iavevor--tarouch conveyor act included. * Unpublished duu, omer plants (J. M. DalUVuii^ U. S. P. H. S.) Fulton, el al. U?f. {). *ludtvit!ual cone for each spindle connected tocxbaist manifold. sS- '-{Hi1 yii^uw''' 'alt g . . *> * f s. r Ir S' 1727 Nsramtar at, 1837 . SUMMARY Table 2 gives a summary of the operations provided with exhaust, feting the number of exhaust ducts and the rote of ventilation per machine, as well os the average dust concentrations to wliich operators m exposed. Average dust concentrations measured near corre sponding operations without exhaust are tabulated to show tbe effec tiveness of the control methods which have been described. CONCLUSION This study of actual results secured by a dust control program in an a&estos fabricating plant is presented as on example of engineering vntrol of on industrial hazard. Attenuate data have not yet been published[to justify die determination of threshold limits of dustiness uSucH. will produce asbestosis in any definite period of time. In the absence of such threshold values it is not possible to determine pormissble limits of dustiness on a medical basis. Nevertheless, any appre ciable decrease in the amount of asbestos dust will cause a decrease in fee incidence and severity of the resulting asbestosis. Tbe elimina tion of all the dust in an industrial workroom is rarely necessary from physiological standpoint and usually economically impracticable. Consequently, actual atmospheric conditions in an industry resulting from the application of practical methods of dust control con be used m temporary standards by that industry (6). REFERENCES (f) Ries, H., and Watson, T. L.: Engineering Geology. John Wiley and Sins, Enc., New York. 1937. (g) Fulton, W. B-, Dooley, A., Matthews, J. L., and Houtz, R. I.: Asbestosis. nit II: Tho nature and amount or dust encountered in asbestos fabricating plants. Spec. UulL No. 42, Pennsylvania Dept, of Labor and Industry. Sept. 20. 1933. (3) Bloomfield,. J. J.. and DallaValle, J. M.: The determination and control of industrial dust. Pub. Health UulL No. 217. Govt. Printing Office, Washington, D. C. 1933. (4) Harding, L. A, and Willard, A C.: Heating, ventilation, and air condi tioning. John Wilev and Sons, Inc.. New York. 1932. ffi) Unpublished data. United States Public Health Service. <0) Higgins, ik, Lanza, A J., Lauey, F. B-, and Rice, G. S.: Siliceous dust in ndatlon to pulmonary disease among miners in the Joplin District, Missouri. BulL 132, U. S. Bureau of Mines, 1917. (7) Page R. T.r Note on a new ocular micrometer for use in dust counting. Pub. Hea'th Rep., o: 1313-1316. a-;?' \ I