Document Jr79Mw0Ew45MqD0JQwRyrOOjZ

FILE NAME Owens Corning OC DATE 1937 DOC OC055 DOCUMENT DESCRIPTION Gov Report - A Study of Dust Control Methods in an Asbestos Fabricating Plant e .yue Eye Eta ne RUBY TAR GAC : IS oe FOR eT i > ra * + 2 * 2 ee as oh whee dha abadteran Di, ww U. S. TREASURY DEPARTMENT HENRY MORGENTHAU JR Secretary PUBLIC HEALTH SERVICE THOMAS PARRAN Surgeon General A STUDY OF DUST CONTROL METHODS IN AN ASBESTOS FABRICATING PLANT BY RICHARD T. PAGE Assistant Public Health Engineer AND J. J. BLOOMFIELD Passed Assistant Sanitary Engineer United States Public Health Service REPRINT No. 1883 FROM THE PUBLIC HEALTH REPORTS VOL 62 No. 48 November 26 1937 Pages 1718 1727 i ( CORNING FIBERGLAS CORP LEGAL & PATENT DEPT REC'D SEP 15 1941 UNITED STATES GOVERNMENT PRINTING OFFICE : WASHINGTON 1938 For sale by the Superintendent of Documents Washington D. s+ Price 10 cents ORLY es A ERE 1 EOP, ka trove.oath thad Cillaal fo ar Toe A STUDY OF DUST CONTROL METHODS IN AN ASBESTOS FABRICATING PLANT By Richard T. Page Assistant Public Health Engineer and J. J. Bloomfield Bloomfield Passed Assistant Sanitary Engineer United States Public Health Service An extensive medical and engineering study of the health of asbestos workers has been conducted by the United States Public Health Service 5 The material contained in this paper supplements the general study with 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 These 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 this country at this time The dust control systems in use with the various processes in each department are described An occupational analysis of employees is presented with a comparison of the atmospheric dust concentrations associated with controlled and similar uncontrolled processes FABRICATION OF ASBESTOS TEXTILES Asbestos is the class name for several different fibrous minerals but the asbestos of commerce 1 is mainly the fibrous form of serpentine known as chrysotile Due to its fibrous nature flexibility and resistant properties asbestos fiber finds many practical applications One of its important industrial uses is in the manu- facture of 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 Signifacant 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 not been considered in the analysis of the data Each dust controlled process tended to decrease the amount of dust generated in subsequent often nor Chrysotile is a hydrous magnasium silicate H.M^/40H.M^/4@ 0 1,0.3Mg0-2510s cent s^>lica43 percent magnesia and 12.9 percent water Other types of asbestos often nor af iron calcium and aluminum as well as magnesium 5 : os gleite ^/^fingleite 2 s 2786-38 enyat ay nage i DUST CONTROL IN AN ASBESTOS PLANT These factors must be considered when comparing dust processes concentrations reported in this plant with the data which have been ( reported for other plants were employed in this plant of whom 18A0pwporrokxiemdaitneldyep3a0r0tmpeenrtssonhsaving a potential asbestos dust hazard confined to these departments namely preparation This study was twisting and winding and weaving The occupa ctiaorndailndgisstpriibnuntiinogn of exposed workers is shown in table 1 Table Occupations and dust exposures of workers in an asbestos textile plani Average dust concentration M. P. P. F. Occupation Number of workers Normal Witbout l- | hansi ventiJation Preparation Crushermen Cotton openers Asbestos openers Bed bulldera Pickermen Others Darding Carders Stock rollers Card tenders Wick rope and oord SpinOntihnegrtwisting and winding Muls spinners and helpers Ring spinners Bpoolera oy Cop winders Universal windera Others Wesving Weaverscloth.ARTY Wet cloth Tape and listing Inspectors Cloth Inspectors Tape ... Inspectors . - N | i NAHARO NAHARO NAHARO NAHARO NAHARO NAHARO g s e2 e2 e2 e2 * * 38 i 123 184 16.7 12.4 260. 260. 117 148 14 40.4 1.7 |. eeccnrewee 1.7 J|annnensorecres .. J. cccccmeeewns a) 08.6 13.9 0 bcnncecommere= 31.0 28 pa /ATITOLO /ATITOLO BO TOPTOP 25 - 4224 42 4 4224 uy 27 9.6 een 1.0 1.0 11..1 1 18 | Dust exhaust for this operation B ample after 1 hour's operation without exhaust * Bample taken inside bin during loading METHOD OF STUDY This investigation included a study of atmospheric dust concentrations in the factory workrooms and a study of the exhaust systems used to remove asbestos dust Eighty atmospheric dust samples were collected at the workers breathing level with the impinger dustwosrakmipnlgincgondaiptpiaornastuasnd3 13 Sixty of these represented present had been turned off represented conditions while exhaust apparatus for 1 hour A collecting medium containing 25 percent ethyl alcohol in distilled water was found to prevent flocculation without causing excessive evaporation in either the sampling flaskosr the counting worsen qeas Fe ae ae Tee ore ee Uae Ce R. P Me ee Lh Rakea Eapt S : LER eed al wig kG# a ibe? Voskdiyad lyosg adRe) es te. se ae owe vi SUS ey i aaa Mp. easVeseads Git wi ; DUST CONTROL AN ASBESTOS ASBESTOS PLANT cells Allsampslaesmplseas mcponlceenstrcaotuintoends counted day after collection collection and counted were were micrometer technique distilled Bloomfield counted Bloomfield according the light technique technique described engraved engraved Dalla Valle A the eyepiece Whipple square square equivalent one customary the standard count used in counting counting Since Whipple quadrant quadrant the Whipple same customary customary volume Whipple count 0.25 cubic millimeter field was the same volume of of sample quantities air removed counted counted exhaust systems pitroetmmoeasvuremeentds through various center velocities velocities Average measurements exhaust center process in table and and discussed little little later the description description of exhaust systems systems in Entrance velocities open measured with an Alnor open hoods anemometer velometer and checked with Most the boods boods vane exhaust enough air pre- pre- line velocities . noted between similar average value given between similar the average value is given. DESCRIPTION OF PROCESSES AND DUST 100 pounds Asbestos is received in burlap .. Cotton is received in standard asbestos These only raw materials materials i yarn yarn this plant plant Unloading Unloading packed raw raw materials fiber the material from hazardous occupations shown means of flow Indi- Indi- to completed fabric is measures measures for dust sheet described below Indi- vidual processes and the control control described described below below, measures for dust DEPARTMENT are described asbestos arrives crushed most most the crushed than mining sorting sorting and fiber screening has received received type is hand other dumped from bags rim screening wheel This latter crushed from dumped minutes These These crushers crushers crushers and crushed attached attached to , the general ventila- ventila- tion tion the preparation preparation department department sufficient prevent high tion concentrations concentrations concentrations operation operation sufficient Crusher men res- near high concentrations of dust near this operwaatsionop.erationcient to prevent Crusher A. had res- DUST CONTROL IN AN ASBESTOS PLANT RAW MATERIALS COTTON CRUDE MILL ASBESTOS | ASBESTOS CRUSHERS RECOVERED MATERIALS ROVING |] WASTE 1 CYCLONE& SETTLING CHAMBER WASTE BAG HOUSE WASTE . . N COTTON OPENERS 4 5 ASBESTOS OPENERS &VIBRATING SCREENS s ROVING REOPNERR EOPENER FLY 4 VIBRATING SCREEN \ WILLOWER SCREEN PICKERS | > MARKET STOCK BINS CARDING DEPT WICKING TWISTED CORD MACHINES CARDS A ROVING CARDS MULE SPINNERS RING SPINNERS ROPE TWISTING MACHINES % Ss FOSTER WINDERS SPOOLERS N CHEM TREATMENT & BRAIDING DEPT COP WINDERS TWISTERS TWISTERS TWISTTWE ISR TES RS q UWNIINVDERESRASL . CHEM TREATMENT TREATMENT RUBBER DEPT INSPECTION IINNSSPPEECCTTIIOONN ~ N MARKET ke NOTE PROCESSES HAVE DUST EXHAUST UNDERLINED asbestos taxtlie plant FIGURE Proots flow sheet SYSTEMS piratore crushers them while loading or unloading the and usually wore man tending three The average exposure of a crusher crushers was 3.5 M. P. P. C. - repairman and janitors were provided with raspire- torsA oDf eamtpylpoeyeaepsprionvtehdebpyret parh aUt.ie oBn. dBepartumentdreepaarntmoefnth^anlndesaalglainst high concentrations of fine rilim dust we wot et mrey met Dl ecm MA Im PREV Mew pege sack = Nt aL BRR? pS @ r it Ce? 5 pathy Sa ec i . * ms T ytasev etRE esseke,, at 4 ran . SBy TGE ad ag Tote 8s fo 4. oan ae, : ev Me tigtea petirose pik 4Waa i, * 1 es ae t aaev 4 elehede) a a a a ; DUST CONTROL ASBESTOS ASBESTOS PLANT PLawT he Asbestos opening screening Asbestos Asbestos opening opening crushed screening asbestos fiber dumped dumped from bags frox openers and lifted into feed lattice hfoplpeorowirth beside asbestos forks Two openers the feed Fo. design operation the method method exhaust different different the were operation same schematic fig hooding was wag ths ) both partially enclosed exhausted The feed lattice int hopper was partially exhausted bottom bottom exhausted the CONVEYOR : CONVEYOR BE CONVEYOR = bausted had own One screen beside bausted vibrating screen screen drawing drawing the charging hopper 400 and over the beside the screen 400 two dis- charging hopper drawing 400 efm exheust hoods, one and ene OVer the dis. a mex. = tor ee a Sime fe ares ai aka SS Frouzz Frouzz FFiibberer recovery process Willowher and vibrating stream per gu eee Bey VS aa SEAT US phe pe 1 suag 32 % m: ts race v aa nik + 3 a, 4 > sar: wees ix - A 2 5G ; . a er>. baa pora$ ry e Si>tobertae cy . ' Public Health Reports Reprint No. 1883 i ks ageNS 4 Nie ore ELARDt ~~ hale oa . FHULMTY eo AREau . e- th anenege a, - Phen. os, 1jtls SSA ee irs, petits 2 e FIGURE Breaker and roving cards ae i 4 4 oes , 5 . a . Geter, Ps mag AN : d a prpsiret a oi : RED Flourx Foster winding machines spoolers . rel meen u gd wee be tet : 2. ot js LOTO TUTEBe Teer 8. ragN ok decthre Hed Lege - Fa t DUST CONTROL IN AN ASBESTOS PLANT 7 charge end of the screen and the stock car drawing 770 cfm The second screen had one bood only over the discharge end drawing 615 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 same men charged the openers and filled the stock cars The average dust exposure of asbestos operators was 3.6 M.P.P.C.F. M.P.P.C.F. Cotton openers 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 but as much as 20 percent cotton was used in lower grade yarns The stage 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 average exposure was about 2.4 M. general air preparation department Weighed quantities of asbestos and cotton were placed in alternate layers in the mixing beds Occasionally layers of roving 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. for the making operation After a bed had been placed the picker operator removed the rear partition of the booth and forked the batch into the 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 fiber 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 carried to the carding room by a pneumatic conveyor Each of the first three machines had a hood over the charging lattice exhausting approximately 500 cfm a pipe exhausting about 1,650 cfm from the bottom settling chambers oe 200 ah tee cee -- om oe ne - 7 tee me nn pad endiAa RM n baer Oe Ringel eee R |, 8 DUST CONTROL IN AN ASBESTOS PLANT under the main picker drum and 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 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 The picker operators wear respirators during the charging operation Dust concentrations during picker charging varied from 4.0 to 9.5 M. P. C. averaging about 6.7 M. P. P. C. Recovery processWeasste roving from the card room was returned to the preparation department for reopening The roving reopener was exhausted only from the pit below the last beater but the 1,780 c^>mof air drawn through this hood were sufficient to prevent the escape of dust through the discharge lattice The dusty air collected by the exhaust systems in the preparation and carding department was blown into a large settling chamber occupying two stories in the end of a separate building Air was displaced 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 frames The filters were beaten down by hand daily during the noon rest period The collected dust was removed during the week end down and stored in bins in the preparation department 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 house dust and fibers separated by cyclones on the exhaust lines from the spooling operation and the weaving department were passed through a willower and vibrating screen fig 4 Approximately 250 cfm of air were exhausted from the top of the charging lattice and 620 cfm from the discharge side of the opening drum Dirt passing the screen dropped onto an inclined tray and was removed by an exhaust hood drawing 730 cfm Fibers which did not fall through the screen were removed by the hood at the lower end of the screen 1,710 cfm and pneumatically conveyed to a cyclone collector Rock and other impurities not picked up by the pneumatic conveyor fell into a waste box below the end of the screen The market for recovered fiber is limited and such fiber is usually too soiled for use in 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. As a measure of the effectiveness of the dust control system in the preparation department the exhaust fans were shut off for hour Pneumatic conveyors remained in operation Dust concentrations ed increased steadily to about 50 M. P. P. C. F. at which time the exhaust fans were turned on The samples taken during this period oe OE Se ee: eR oe Se co PetiPACT aye os Bis SitagePHS yo < ox sy hid shee Sedide PRINT ayer ce OF tan Dy or pes ot be . Me 3 . AR . | . . mut Dds Z . MITINf $i 2 . oe iv. ELOY FE. . > hoe oss yan Sine tt nite DUST CONTROL IN AN ASBESTOS PLANT 9 were only a partial measure of uncontrolled conditions since the hoods and enclosures had a definite control value While the location and design of hoods were the most important factors in dust control in the preparation department general ventilation helped prevent high dust concentrations This department occupied approximately 320,000 cubic feet of space from which approximately 34,650 cfm of air were exhausted Consequently 6.5 air changes per hour were produced by mechanical ventilation which was supplemented by natural ventilation through doors windows and roof ventilators Fortunately heating was not a problem in this plant CARDING DEPARTMENT Mixed fiber from the preparation department was dropped from pneumatic or mechanical conveyors into bins in the carding department The total volume of exhaust from four bins was 6,850 cfm the major portion of this air being drawn through the one or two bin doors left open during the loading of carding room stock cars Dust concentrations as high as 40.4 M. P. P. C. F. were measured inside an active bin while the dust concentration just outside the door of the same bin was only 4.6 M. P. P. C. F. Workers classed as stock rollers fork the mixed fiber from the bin into stock cars This operation is supposed to be performed with both stock car and stock roller outside the bin door This rule of keeping out of the bins should be strictly enforced However stock rollers wearing respirators like to push their cars under the chute and then climb into the car and down the stock The cards are machines having a series of revolving cylinders wound diagonally with strips of leather set with fine sharp steel bristles Carding removes remaining small bits of rock and combs the fibers into a more or less parallel condition to facilitate spinning At the time of this study 31 roving card units and 2 wicking cards were being operated A roving card unit fig 5 consisted of two cards a breaker or primary card and a finisher or roving card The mixed fiber was fed by hand from the stock car to the feed hopper of the breaker card The stock roller wore a respirator during this operation The fiber passed through the breaker card emerging as a loose blanket or web It was carried to the finishing card by a lattice conveyor or camel back The fiber was stripped from the last cylinder of the finisher onto a moving leather apron where a set of reciprocating rubbers condensed it into loose rovings of unspun yarn These rovings are wound on long jack spools to be taken to the spinning department The rovings at the extreme ends of the cards cannot be used for spinning because they lack uniform thickness These rovings are collected by two small hoods and pneumatically conveyed to a collection bin for return to the preparation department 10 DUST CONTROL IN AN ASBESTOS PLANT - The exhaust applied to roving cards is shown schematically in figure 7. The quantity of air exhausted varied from 1,100 cfm to 1,800 c^>m on different carding units with an average exhaust of 1,440 cfm per unit Cards are partially enclosed and only sufficient air is exhausted to prevent the escape of dust Each breaker card is exhausted at three points Hood B exhausts from the top of the feed hopper over the feed apron This hopper was enclosed and covered the cover being lifted during filling About 160 c^>mof air were exhausted through the hood Hood A exhausted the top fly from the enclosure covering the main carding cylinder Hood CAMEL CONVEYOR COTTE 1 . De [SQ pe A BREAKER FINISHER el a= e ; D Q D D ew 7 G e FEED BOX COVER Ficar 7 Schematic plat of card ezbaust system C exhausted the bottom fly from the settling chamber under the carding cylinders Approximately 285 cfm were exhausted through each of these hoods The finishing card had four exhaust connections besides the two small hoods G which removed the waste roving Hoods E and F correspond to hoods A and C respectively on the breaker card providing an exhaust of approximately 285 cfm each The doffer card cylinder doffer combs and roving apron were exhausted from below through hoods D and D at 70 cfm each About 40 cfm were ' exhausted through each roving collector We re ee a naaey ey ae tS, ea son Oe > . . we ph 2 ee, DUST CONTROL IN AN ASBESTOS PLANT 11 The volumes of air exhausted through each hood were estimated on the basis of pipe areas Actual volumes showed wide variations on different unite Single cards were used in the manufacture of asbestos wick andrope since a thick roving was desired The wick or rope was twisted from the unspun roving The wicking cards were exhausted at three points Approximately 380 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 bottomfly settling chamber Dust concentrations during carding averaged 1.7 M. P. P. C. F. This was also the average exposure of wicking card operators and wick and rope twisters Samples taken near the carding department weight scales showed less than 0.5 M. 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 the 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 off 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. in the air Under normal operating conditions about 64,000 cfm of air are exhausted from the 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 yarn as roving is twisted or spun into compact threads on either mule or ring spinning frames masin In this plant most of the spinning was done on mule spinners The spun thread was transferred from the spinning spindles to spools on masinas Foster winding machines spoolers Spooled thread to be used as jagta filler or woof in woven cloth was rewound on a cop winder into cops which will fit into the loom shuttles The remaining spooled thread 205ku was respooled on twisters which twist several threads into a yarn The number of strands used determined the size of yarn Both plain 205ku and metallic yarns were twisted Metallic yarn contains one or more strands of fine wire Part of the twisted yarn was used in cloth 43628aiks weaving while the remaining yarn was rewound on Universal winding frames for the market 436286aiks tee 18 SEN Ss ea gre y. Rasta adage | 12 DUST CONTROL IN AN ASBESTOS PLANT Mule spinning was separated from other operations in this department by partial partitions Natural ventilation was good and no exhaust systems were used The average dust concentration was 0.85 M. P. P. C. with a maximum of 1.3 M. P. P. C. F. recorded Ring spinning cop winding and Universal winding machines were located in the same room with the twisting machines Average exposures in the first three operations which were not themselves especially dusty were due to dust from the twisting operation With the exception of a trial exhaust system on one twister the remaining machines were not provided with exhaust The trial system was reported to be satisfactory and is to be installed on all twisting FIGURE B bematic views of exhaust system applied to Foster winders machines In this system the bottom of the twisting frame was enclosed and a total of 1,700 cfm of air per machine was drawn downward past the twisting yarns and through five conical hoods distributed along a central exhaust duct Average dust concentrations at the various operations in this room were ring spinning 5.0 M. P. P. C. F cop winding M. P. C. F Universal winding 2.8 M. P. P. C. F and twisting 11.0 M. P. P. C. F. with a maximum of 18.8 M. P. P. C. F. recorded beside a twisting frame No accurate measurements of the efficiency of the exhaust system on the single exhausted twister could be secured but simultaneous samples on both sides of this frame showed a dust sere eka tet 5: -Se vas ~2erty Pea EE re Cpe Met OS IONE . ER whe . rf f eee ae Pare Pe er PO wen ^' Public Health Reports Reprint No. 1863 > PLATE T t : a { t P e Hse Biter gee 2H ' Me eas she . Whe Dae? Figure Onexhausted broad cord Ca EDce fs ioe 2 ' Figure Table for inspecting calendaring and brushing woven cloth cows ne wee a Pare ry a ns: -S-. oe eae. a. Pye . Sh - nee. et pyte J wee , DUST CONTROL IN AN ASBESTOS PLANT 13 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. P. C. F. on the other side Four Foster windefs spoolers were partially separated from the other operations by partitions fig 6 The exhaust system consisted 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 off 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 these were considered to be the most important source of dust The dust control program calls for installation of exhaust systems on dry tape listing and brake looms At present these operations are mainly performed wet or partially wet Brake looms were not in operation during this study Significant 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. C. F. and averaged 3.0 M. P. C. Nineteen clotb 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 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 swing joint at the bottom The openings in the loom hood consisted of four lotsnine 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 par loom Exhaust dampers were provided on all looms and a sufficient number to balance the system are closed on wet or idle looms The average dust exposure of a weaver operating a dry loom with exhaust was 0.7 M. P. C. F. while the average exposure in wet weaving without exhaust was 2.6 M. Samples taken beside a dry loom without exhaust showed dust concentrations of 9.6 M. P. P. C. F. ET IT bk Nh deer et ne rer _ -- to nate et, ee Pe aay, i - fmm he ee ee el . _ 14 DUST CONTROL IN AN ASBESTOS PLANT ^' e - after 45 minutes Average dust concentrations during dry weaving have been shown as 49.7 M. P. P. C. F. 5 Woven cloth was inspected brushed and calendered on the inspec- tion table shown in figure 10. Each of the driven brushes was | i rene Fiovuz Schematic views of exhaust system applied to broad looms partially enclosed and exhausted Approximately 750 cfm of air were drawn through each of the two hoods at the front of the table and about 200 cfm were drawn through the cleaning hood at the back of oe + ene etme Oa TS By te ca Stave es ww . hie te ep oe ee fe pa eo, tee int wwe se Qe "3 . > DUST CONTROL IN AN ASBESTOS PLANT 15 the table Dust concentrations M. P. C. F. A sample taken across the table without benefit of tion of 11.8 M. P. C. F. during while exhaust inspection averaged 0.5 roll of fabric was passed_ showed a dust concentra- Doffing inspection and calendering of tape and listing were hand operations and were not provided with exhaust Dust concentrations of 5.0 M. P. P. C. F. were recorded during these operations but the exposure was intermittent Creelers had an average exposure of about M. C. while placing spools and threading looms An exhaust of 12,200 cfm of air was provided in the weaving de- partment corresponding to approximately three air changes per hour In cold weather warm air was distributed through the department from a plenum system while in warm weather natural ventilation was secured through use of windows on all four sides of the department OTHER OPERATIONS Other operations in this plant consisted of processes in which the arnwas chemically treated and fabricated or processes for chemically treating or rubberizing fabricated cloth No potential asbestos bazard was associated with these processes with the exception of one braiding machine used to make large diameter asbestos tubing This machine was covered with a conical canopy hood about 6 feet in diameter which provided an exhaust of approximately 200 cfm of air A sample taken beside this machine showed a dust concentration of 0.4 M. P. P. C. at the operators breathing level Table Volumes of air exhausted per machine in various operations in an asbestos textile plant Operation Connee-Connee- Connee- Total Thoataulsts Dust | tions air volume Dust per | on ft./min tratiocnoncen axhaust M.P.P.C.F. concan tration with- out exhaust M.P.P.O.F. Asbestas opener CottonCoVttiobn roap tienn g escrreen Mixing beds Picker .. se. le seen ceeeeccoes wee Raving reopener 2. Fly willower and screen cards RovingBreaker primar)y wo Finisser reece Wicking card ocean reemm enc nn wn ween, ----------- a ee CFoasrtdergrwiinnddeerrtsspoolars we spoolars Twisters broad Calenderarspolarsspoolars Weaving broad looms a. 3 826-1,000 826-1,000 826-1,000 } 1 as 11.3-0.0 3 2,160 nn J 3.025 3 2.870 2.870 ie &d 3.1-10.6 1 1,780 1,780 t3 1,000 11,,420 420 1.430 43 1.440 1.440 i 2.830 2.830 " 225 2225 2 1.300 1.300 3 1,650 Uppubished Dalle Valle conveyor ) 4 Equipped with pneumatic conveyor exhaust through data other plants 1. M. Fulton al Ref f U. E. P. conveyor not included H. B. Individual cons for each spindle connected to exhaust manifold -- w - Tlmess Le, . Wo ~ 9 tees TITS 2 2 ee ~ ee : -_ ae ' 16 DUST CONTROL IN AN ASBESTOS PLANT SUMMARY exhaust Table 2 gives a summary of the operations listing the number of exhaust ducts provided with and the rate of ventilation machine as well as the average dust concentrations to which per are exposed Average dust concentrations operators sponding operations without exhaust measured near corre- tiveness of the control methods which haraevetabbeuelnatdeedsctroisbehdow the effec- CONCLUSION This study of actual results secured by a dust control in asbestos fabricating plant is presented as program an control of an industrial hazard an example of engineering published to justify the determinatAiodneqoufattheredsahtoaldhlaivmeitsnootf dyusteintess which will produce asbestosis in any definite period of time In absence of such threshold values it is not possible to determine permis- sible limits of dustiness on a medical basis ciable decrease in Nevertheless any appre the amount of asbestos dust will cause a decrease the incidence and severity of the resulting asbestosis The in tion of all the dust in an industrial industrial elimina- workroom is rarely necessary from & physiological standpoint and usually economically impracticable Consequently from actual atmospheric conditions in an industry resulting the application of practical methods of dust control can be as temporary standards by that industry 6 * used REFERENCES Inc1. NReiwesYoHr.kand19W3a7tson T. L Engineering Geology John Wiley and Sons plants Par2 t IFIulTthoen Wna.tuBr.e DaonodleaymoAu.ntMaotf tdhueswtseJn.coLu.ntaenrdedHoiun tazsbRe.st.o:s Asbestosis 20 1935 Spec Bull No. 42 Pennsylvania Dept. of Labor and IndustfrabyricSaetpitn.g industrial dust 3 Bloomfield J. J. and Dalls J. M The determination and Pub Health Bull No. 217 Govt control of 1935 Printing Office Washington Unpublished data 4 Harding tioning L. A. and Willard A. C Heating ventilation and air John Wiley and Sons Inc. New York 1932 condi- 6 6 Higgins E. United States Public Health Service relation to Lanza A. J. Laney F. B. and Rice G. .: Siliceous dust iin n Bull 132 U.puS.lmBounraerayu doifseMaisneeasm1o9n1g7 miners in the Joplin District Missouri 1315-1316 hing Pu7 b HPeaaglethR.RT ep N5o2te on a new ocular micrometer for use iin n dust coun : --