Document LoE4ObN6kXV2bQ0ZXraDkvw2w

FILE NAME: Raybestos-Manhattan (RBM) DATE: 1937 DOC#: RBM095 DOCUMENT DESCRIPTION: US Public Health Report - Study of Dust Control Methods in an Asbestos Fabricating Plant with Cover Letter from Raybestos-Manhattan General Asbestos & Rubber Division of Raybestos-M anhattan, Inc. North Charleston, S. C. "ay 25, 1937 * Dr. I;. li. Sayers, Senior Surgeon, chief, division of In d u strial Hygiene, national In s titu te of Health, U. 3. r u b l i c H e a lth S e r v ic e , W ashington, i>. C. ` Sear Doctor;- I have received yours o f the 20th. en c lo sin g a copy of the paper showing the r e s u lts of the study conducted a t our p la n t during t h e c o n th o f Huron. o f t h i s y e a r . I d e la y e d acknow led g in g t h i s pap e r i r r r .e d l a te ly a s I w ished to r e a d st rre v e r y c a r e f u l l y , and a f t e r h a v in g r e a d t h i s r e p o r t I f e e l t h a t f d s s r s Haga ana B lo o m fie ld have made a very careful study of the conditions ex istin g a t this plant* ^Iso, I w ish to thonk you f o r th e o p i n i o n e x p r e s s e d a s p e r tfca l u s t s e n t e n c e of the f i r s t paragraph of your l e t t e r o f the 20th* In r e g a rd to th e s ta te m e n t &3 cade in th e second p a r a g ra p h o f your l e t t e r a s to your d e s irin g to p u b lish th is re p o rt in the o f f ic ia l organ o f the Tu'clio H ealth .serv ice (P u b lic H e alth .sp o rts), I would l i k e to a d v is e t h a t when hr* <*ilso;i o f th e C outh C a ro lin a c t s t a H u a lth 'd ep artm en t f i r s t a p p ro ach e d ns in r e g a r d t o t h i s m a t t e r , I a d v i3 c u U r. W ilson ch a t I v;ould*havo to f i r s t ta k e th e m a tte r up w ith o u r ;r c 3 lu o n t 'T . Suitnor SlmpBon, b e fo re I could g r a n t h l3 r e q u e s t 03 to making a stu d y o f th is p la n t. A fter ta k in g th e a tta r up w ith Ur. C lapson, i t was a g re e d w ith f r . i l s o n th a t no p u b l i c i t y would bo g iv e n a3 to th e r e s u l t s o f th e in s p e c t i o n by th e U. f . H e a lth D epartm ent in c o o p e ra tio n w ith the douth C aroline c ta to Departm ent of H ealth u n til a f te r your r e p o r t he a been subm it tad to ua and we c o u ld p a s s on same* I c:.t t h e r e f o r e , in acco rd an ce w ith t h a t unde rs can ding, fo rw ard in g today to Hr. Simpson th e r e p o rt which you su b m itte d , a lo n g w ith your l e t t e r , and re q u e s tin g Hr.*.impson to g iv e c o n s id e ra tio n to your re q u e s t as to th e p u b lish in g of the re p o rt. J u s t a s soon as X h ear f r o t h ia , I w ill ad vise you. I might also s ta te th a t I heve cade a copy of th is re p o rt and have turned i t over to -"r. J u lia n kifcokoll f o r h is c o n s id e r s tio n . fhsak in*-' you f o r h av in g s e n t ms t h i s r e p o r t and a l s o ov y o u r l e t t e r of ths 20th, and w ith k i n d e s t p e r s o n a l r e g a r d s to you anu a l s o to f s s a r a . huge and Dlooftfield, I re c a in , . Yours very tru ly , --.Ji jo Guu.hiAl, AcBC.^foJ cit hUBdc.it DIVlDIoJS wiyS HITOITULL / o f-h jO y b e a to s -'- 'a n h a t t a n , Inc* fr f / a study of dust cohthol :.Ic.jho3s m ah asbestos fabricating p l -.dt By R ichard T. Page, A s s is ta n t P u b lic E e a lth E n g in ee r, and J . J . B loom field, P . A. S a n ita ry E n g in eer, United S tates P ublic H ealth S ervice. An e x te n s iv e medical and e n g in e e rin g stu d y o f th e h e a lth o f asb e sto s workers has been conducted by the U nited S ta te s P u b lic H ealth S e r v ic e ! / The m a te ria l c o n ta in e d in t h i s pap er supplem ents the g e n e ra l stu d y w ith a d e ta ile d study of th e d u st c o n tr o l methods used in an a s bestos fabricating plant. The fo llo w in g re p o rt on p re s e n t c o n d itio n s and how th ey have been obtained i s p re sen ted as an example o f th e r e s u lts of th e a p p lic a tio n of s c ie n tif ic methods of dust c o n tro l. These d ata should be i n t e r e s t ing not only to the asbestos in d u stry but also to other in d u strie s h aving s im ila r d u sty p ro c e s s e s . The p la n t s tu d ie d has o n ly p a r t l y com pleted an e x te n siv e d u st c o n tr o l program and c o n d itio n s a re bein g improved c o n tin u a lly and, co n seq u en tly , th e s e r e s u lt s should not be i n te r p r e te d as r e p re s e n tin g the maximum p o s s ib le e f f io ie n c y in th e con tro l of asbestos dust, but i t is believed th at they are representative o f th e b e s t p r a c tic e in t h i s o o u n try a t t h i s tim e . The d u st c o n tro l systems in use w ith the various processes in each departm ent are de s c r ib e d . An o c c u p a tio n a l a n a ly s is o f employees i s p re se n te d w ith a comparison of the atm ospheric dust co ncentrations asso ciated w ith con- --$ tro lle d and s im ila r unco n tro lled p ro cesses, FABRICATIOU OF ASBESTOS TEXTILES A sbestos i s th e c la s s name f o r s e v e ra l d i f f e r e n t fib ro u s minor*-la but the asb esto s of oom m ercei/is mainly the fib ro u s form of serp en tin e known aa c h r y s o tile * . Due to i t s fib ro u s n a tu re , f l e x i b i l i t y , and h e a t r e s i s t a n t p r o p e r tie s , asb e sto s f i b e r fin d s many p r a c t i c a l a p p lic a tio n s . One o f i t s im portant i n d u s t r i a l uses i s in the m anufacture o f f i r e r e s i s tant te x tile s. In the p la n t s tu d ie d , p r a c t i c a l l y a l l raw m a te ria l was crude Canadian o r South A frican A sb esto s. Some im ported s h o rt f i b e r was used, os w ell as some o f the s h o rt f i b e r salvaged in the reco v ery p ro c e ss, but most of the sh o rt recovered f ib e r was shipped to o th e r p la n ts . S ig n if i cant v a ria tio n s in atm ospheric dust concentrations due to the grade of fib e r being processed were not evident in co n tro lled processes in th is p la n t. Consequently, the type of f ib e r used has not been considered in the a n a ly sis o f the d a ta . Eaoh dust c o n tro lle d process tended to decrease th e amount o f dust g en erated in subsequent p ro c e sse s. These f a c to r s must be considered when comparing dust c o n c e n tra tio n s re p o rte d in t h i s p la n t w ith th e d ata Tfaich have been re p o rte d fo r o th e r p la n ts . Approximately th re e hundred persons were employed in th is p la n t, o f whom one hundred and e ig h ty worked in departm ents having a p o t e n t i a l asb e sto s dust h a z a rd . This study was confined to th e se departm ents, namely: p re p a ra tio n ; card in g ; sp in n in g ; tw istin g and winding; and weaving, The o c c u p a tio n a l d i s t r i b u ti o n o f exposed workers i s shown in Table I . (Take in Table I ) * C lirysotile i s a hydrous magnesium a i l i b a t e (i^I^sSigO g or 2H2O.3i.tgO.28i(y c o n ta in in g 4 4 .1 # s i l i c a , 4 3.0# magnesia and 1 2 .9 # w a te r. Other types of aabeatos o ften contain s i l ic a t e s of iro n , calcium and aluminum aa w ell as magnesium.it/ ttTOD 02* STUDY T h is investigation included a study o f atm o sp h e ric d u s t concen trations in the f a c t o r y workrooms, and a study o f th e e x h a u st sy stem s used to remove asbestos dU3t. Eighty-tw o atm ospheric dust samples were c o lle c te d a t the w orkers1 breathing le v e l w ith the im pinger dust sam pling ap p a ratu s^ /. S ixty-nine of th ese re p resen te d p re se n t working co n d itio n s and th ir te e n rep resen ted conditions w hile exhaust apparatus had been turned o ff fo r one hour. A c o l l e c t i n g medium c o n ta in in g tw e n ty -f iv e p e rc e n t e t h y l a lo o h o l in d i s t i l l e d w a te r wa3 found to p re v e n t f lo o c u la tio n w ith o u t c a u sin g e x c e s s iv e evaporation in e ith e r the sampling fla sk s or the counting c e lls . A ll sam ples were counted th e day a f t e r c o l l e c t i o n . Due to th e low d u st con c e n tr a tio n s e n c o u n te re d , mo3t o f the sam ples r e p re s e n te d the d u s t in from tw enty to t h i r t y cubic fe e t o f a i r . Samples were d ilu te d w ith d is tille d w ater and counted according to the lig h t fie ld technic described by 31oomfield and D allaV alle^/. A m icrom eter eyepiece having an engraved sq u are e q u iv a le n t to o n e - fo u rth th e s ta n d a rd Whipple sq u are was u sed in co u n tin g . Since i t is custom ary to count only one quadrant o f the Whipple f i e l d , th e same volume o f sam ple (0 .2 5 cu.mm.) p e r f i e l d was counted. The q u a n t i t i e s o f a i r removed th ro u g h th e v a r io u s e x h a u st system s were c a lc u la te d from P ito t tube measurements o f c e n te r lin e v e lo c itie s in the pipe Xlnea^J, Average exhaust r a te s p er process are lis te d in Tabl8 I I and disoussed below in the d e s c rip tio n o f exhaust system s. E ntrance v e lo c itie s a t open hoods were measured w ith an Alnor V alom eter and checked w ith a vane anem om eter. I.!ost o f the hoods wore o f the en closed type designed to exhaust only enough a i r to prevent the escape of 4 a s b e s to s d u st in to th e workroom. Where in d iv id u a l measurements were im p rac tica l, a i r volumes exhausted through each hood were c a lc u la te d from measurements o f main l i n e v e l o c i t i e s . Whenever d iffe re n c e s in ex h au st volumes were no ted between s im ila r hoods on th e same o p e r a tio n , the average value is given. DESCRIPTION OP PROCESSES AiiD DUST CONTROL ISASURIiS Asbestos is received in burlap bags containing one hundred pounu3 o f f i b e r . C otton i s re c e iv e d in sta n d a rd b a le s . These a re th e only raw m a te r ia ls u sed in the p re p a ra tio n o f a s b e s to s y arn a t t h i s p l a n t . Un lo a d in g , sto ra g e and tra n s p o r ta tio n o f th e packed raw m a te ria ls were no t hazardous o c c u p a tio n s. The p ro g re ss o f th e m a te r ia l from raw f i b e r to com pleted f a b r ic i s shown by means o f a flow s h e e t (P lgure I ) In d iv id u a l processes and the measures fo r dust co n tro l are described below. . (Take in Figure I) P reparation Department. C rushing. Some o f th e a s b e s to s f i b e r a r r i v e s a t th e p la n t as "p recru sh ed " f i b e r but most o f the crude f i b e r has re c e iv e d no tre a tm e n t o th e r than m ining, s o r tin g and s c re e n in g . T his l a t t e r type i s hand dumped from the bags in to rim-wheel cru sh ers and crushed from fiv e to f if te e n m inutes. These cru sh ers have two heavy r o l l e r s a tta c h e d to a r a d ia l a x le , and re v o lv e on a smooth su rfa c e d tr a y in which th e a sb e sto s i s p la c e d . The a s b e s to s f i b e r i s c o n s ta n tly s t i r r e d d u rin g c ru sh in g by re v o lv in g scrap ers. A fter crushing, the f ib e r is rep laced in th bags and c a rrie a to the asb esto s opener. C rushers were not enclosed or exhausted in any way b u t th e g e n e ra l v e n t i l a t i o n in th e p r e p a r a tio n department was sufficient to p re v e n t h ig h c o n c e n tra tio n s o f d u s t n e a r t h i s o p e r a tio n . C rusher men had re s p ir a to rs * * and u s u a lly wore them w hile lo ad in g o r unloading th e c ru sh e rs. The average exposure o f a cruaherman ten d in g th re e c ru sh e rs was 3 .5 " .P .P .C .F . A sbestos Opening end S creen in g . The crushed f i b e r i s dumped from bags to the flo o r beside the asb e sto s openers and l i f t e d in to the feed l a t i e s hopper w ith wooden hand fo r k s . Two openers o f d i f f e r e n t design were in o p e ra tio n but the method of exhaust hooding was the same on both (See Schematic Design - F igure I I ) . The feed l a t i c e hopper wa3 p a r t i a l l y enclosed and exh au sted a t th e top. (Hood A ). A second hood exhausted the bottom f l y and s e t t l e d d u st from th e bottom o f the opener (Hood B ). The opened f i b e r was packed up by hood C and p n eu m atically tra n sp o rte d to a cyclone s e p a ra to r vdiere the f ib e r s were removed and dropped onto an enclosed v ib ra tin g sc re e n . A la rg e p o rtio n of th e d u st and f in s f ib e r s e n te rin g th e asb estos opener was removed by hoods A and B. Clumps o f unopened f i b e r s and p ie c e s of rock too heavy to be l i f t e d by the pneu matic f i b e r conveyor, f a l l onto an en c lo se d b e l t oonveyor serv in g both openers, and were c a rrie d to the recovery p ro cess. (B elt conveyor not shown in F igure I I ) . Exhaust volumes through th e hoods were: hood A400 ofm, hood B- 400cfm, hood C- (pneum atic conveyor) 1800 cfm, conveyor v e lo c ity 2730 f t ,/m i n u t e . (Take in F igure I I ) Each opener had i t s own oyclone s e p a r a to r and enclosed and ex h au sted , v ib r a tin g screen . One screen had two exhaust flo o d s, one beside i* A ll employees in the p re p a ra tio n departm ent and a l l r e p a ir men and J a in to r s were provided w ith r e s p ir a t o r s of a type approved by the U. 3. Bureau of liines a g a in s t h ig h c o n c e n tra tio n s o f fin e s i l i c a d u st. 6the ch arging hopper drawing 400 ofm and one o v er th e d isc h a rg e end o f the soreen and the sto o k o a r, draw ing 770 ofm. The second soreen had one hood o n ly , o v er th e d isch arg e end, drawing 615 ofm. S hort f ib e r s and rook p a r tic le s p assin g the screen s f e l l through a chute to the en closed recovery conveyor. Fiber f a ilin g to pass these screens dropped in to a stock c a r. F u ll sto ck c a rs were pushed to a p latfo rm so ale and th en 'go Ghe m ixing bed s, The same men charged Ghe openers and f i l l e d th e stock c a r s . The average dust exposure o f asb e sto s-o p en er o p era to rs was 3.6 M .P.P.C.F, Cotton O peners, The b e s t g ra d es o f in s u la tio n c o n ta in very sm all amounts o f co tto n i f any, but in a l l o th e r c a ses, co tto n f ib e r i s mixed w ith a sb e sto s f ib e r to improve i t s sp in n in g q u a l i t i e s . At t h i s p la n t th e b atch seldom c o n ta in e d more than 15; c o tto n by w eight but as h ig h as 20# c o tto n were used in low er grade y a rn s . The two s ta g e , S ao o -lo w e ll, c o tto n opener was exhausted a t th re e p o in ts , 770cfm of a i r were exhausted through a canopy hood o v er th e fe ed l a t i c e , 370 cfm from th e bottom of the prim ary opener and 1130 ofm from th e b o tto n o f th e secondary o p en er. Opened c o tto n f i b e r was d isch arg ed in to sto c k c a r s . Bo sam ples were taken a t the c o tto n openers b u t the o p e ra to rs average exposure was about 2 ,4 K .P .P .C .F . (G eneral a i r - p re p a ra tio n departm ent). Mixing. Weighed q u a n titie s o f asb e sto s and c o tto n were placed in a lte r n a te la y e rs in the mixing beds. O ccasionally, lay ers of roving w aste from the ca rd in g room wer8 reopened and added to the bed. Mixing was done in s ix exhausted booths, each lO '-S " deep by 6*-10n wide by 6 * hig h . Sides of the booths were permanent while th e back co n sisted of a rem ovable wood and canvas s e c tio n . Each booth was covered by a pyramid hood 32" high through which approxim ately 1025 ou, f t . a i r per minute p e r hood were e x h a u ste d . The v e lo c ity o f a i r motion in to th e s e booths averaged 50 f t . p e r m inute d u rin g bed making and about 30 f t . p e r minute during p ick er lo ad in g . Dust co n c en tratio n s averaged 5.4 L r.P.r.C .F. fo r th e bed making o p e ra tio n . A fte r a bed was p la c e d , the p ic k e r o p e r a to r removed the r e a r p a r titio n o f the booth ana forked the hatch in to the charging hopper of a p ic k e r (F ig u re I I I ) . The p ic k e r machine mixes th e f i b e r s in re v o lv in g b e a te rs * The fo u r machines re p re s e n te d th r e e d i f f e r e n t o p e ra tio n s and two d i f f e r e n t ty p es o f exhaust sy stem s. The f i r s t machine, not in o p e ra tio n d uring th is study disch arg ed mixed f ib e r in to a stock c a r. This m a te r ia l was th en passed through a second p ic k e r f o r rem ix in g . The second and th ir d machines discharged mixed f ib e r onto a b e lt conveyor which tr a n s p o r te d i t to b in s in th e c a rd in g room. The p ro d u ct o f th e fo u rth p ick er was c a rrie d to th e card in g room by a pneum atic conveyor. Each o f th e f i r s t th re e machines had a hood over the charging l a t t i c e ex h a u stin g ap p ro x im ately 500 cfm, a p ip e ex h a u stin g about 1650 ofm from th e b o tto m -fly s e t t l i n g chambers under th e main p ic k e r drum, and a hood o v er th e end o f th e d isc h a rg e l a t t i c e e x h a u stin g about 400 cfm. The fo u r th p ic k e r had the same hood arrangem ent o v e r th e ch a rg in g l a t t i c e b u t had no b o tto m -fly exhaust and the mixed f i b e r was removed by a pneum atic conveyor ex h a u stin g ap p ro x im a te ly 2000 cfm o f air* a t a v e lo c ity o f 2550 f t . p e r m inute. The p ic k e r o p e r a to rs wear r e s p i r a t o r s d u rin g the charging o p eratio n . Dust concentrations during picker charging v arie d from 4 .0 to 9.5 M .P.P.C.F, averaging about 6.7 M .P.P.C.F. (Take in Figure I I I ) R ecovery P ro c e s se s , Waste ro v in g from the card room was r e tu rn ed to th e p re p a ra tio n dep artm en t f o r re o p e n in g . The roving reoponor was exh au sted o n ly from th e p i t below th e l a s t b e a te r , but th e 1780 cfm of a i r drawn through t h i s hood ware s u f f ic ie n t to prevent the escape o f dust through the discharge l a ttic e . The d u sty a i r c o lle c te d by th e ex h au st system s in th e p re p a ra tio n and c a rd in g departm ent was blown in to a la r g e s e t t l i n g chamber occupying two s t o r i e s in th e end o f a s e p a ra te b u ild in g . A ir was d is p la c e d from th i s room to a bag house occupying the second f lo o r on th e o th e r end o f t h i s b u ild in g . Dust was f i l t e r e d o u t by b u rla p f i l t e r s s tr e tc h e d on "A" fram es. The f i l t e r s were b e a te n down by hand d a ily d u rin g the noon r e s t p e rio d . The c o lle c te d d u s t was removed d u rin g th e weekend shutdown, and s to re d in b in s in the p re p a ra tio n d ep artm en t. Bag house d u st was screen e d on a co m p letely en closed and ex h au sted v ib r a tin g sc re e n (Background F igure 17) and the long f ib e r s were removed to a cyclone c o lle c to r by a pneum atic oonveyor. The d u st from th e s e t t l i n g chamber, the lo n g f i b e r s from the bag house d u st, and f ib e r s sep a rated by cyclones on the exhaust lin e s from the spooling o p eratio n and the weaving departm ent were passed through a fly - w i'llo w er and v ib r a tin g screen (F ig u re 1 7 ). A pproxim ately 250 ofm o f a i r were exhausted from the to p o f th e ch arging l a t t i c e and 520 ofm from th e d isc h a rg e sid e of th e opening drum. D irt p a ssin g the so re en dropped onto an in c lin e d t r a y and was removed by an ex h au st hood drawing 730 ofm. F ib e rs which d id n o t f a l l through the sc re e n were removed by the hood a t the low er end o f th e so reen (1710 cfm) and p n e u m a tic a lly oonveyed to a cyclone c o l l e c t o r . Rock and o th e r im p u ritie s not pioked up by the pneum atic conveyor f e l l in to a waste box below the end o f th e so re e n . The m arket f o r re c o v e re d f i b e r i s lim ite d and suoh f ib e r 13 u su a lly too so ile d fo r use in high grade t e x t i le s . Consequently only p a rt of the c o lle c te d dust was passed through th is p ro c ess. Average exposure o f o p e ra to rs was e s tim a te d a t between 3 and 5 M .P.P.C .F. (Take in F igure 17) As a measure o f th e e f f e c tiv e n e s s o f th e d u st c o n tro l system in the p re p a ra tio n departm ent, the exhaust fans were s h u tt o ff fo r one hour. Pneuni8ticconveyor3 remained in o p e ra tio n . Dust co n cen tratio n s increased s t e a d i l y to ab o u t 50 M .P.P.C .F. a t v?hich tim e th e ex h au st fa n s were tu rn ed on. The sam ples taken d u rin g t h i s p e rio d were on ly a p a r t i a l measure o f uncontrolled conditions since the hoods and enclosures had a d e fin ite oontrol value. While th e lo c a tio n and design o f hoods were the most im portant fa cto rs in dust control in the preparation department, general v e n tila tio n helped prevent high dust co n cen tratio n s. This department occupied approxim ately 320,000 cu. f t . o f space, from which approxim ately 34,650 cfm o f a i r were e x h a u ste d . C onsequently 6 .5 a i r changes p er hour were produced by m echanical v e n t i l a t i o n which was supplem ented by n a tu r a l ven t i la ti o n through doors, windows, and ro o f v e n tila to r s . F o rtu n ately h e a tin g was n o t a problem in t h i s p l a n t . Carding D epartm ent. Mixed f i b e r from th e p re p a ra tio n departm ent was dropped from pneum atic or m eohanical conveyors in to b in s in the ca rd in g d ep artm ent, A t o t a l volume o f 6850 cfm was exhausted from fo u r b in 3 , th e m ajor p o rtio n of t h i s a i r b ein g drawn th ro u g h th e one o r two b in doors l e f t open d u rin g th e lo a d in g o f oarding room s to c k c a r s . Dust co n cen tratio n s as high as 40.4 (2.P.P.C.F, were measured in sid e an a c tiv e bin while th e dust co n cen tratio n ju s t outside the door of the same b in was o n ly 4 .6 M .P.P.C .F. W orkers, c la s s e d as sto c k r o l l e r s , 10- fo rk the mixed f ib e r from the bin in to stock o a rs . This o p eratio n i s supposed to be performed w ith both sto ck c a r and stock r o l l e r o u tsid e the bin door. This ru le of keeping out o f th e bins should be s t r i c t l y enforced. Howdver,stock r o lle r s , wearing re s p ir a to rs , lik e to push th e ir cars under the chute and then climb in to the ca r and "tread-dow n" the stock. The cards are machines having a s e r ie s df re v o lv in g c y lin d e rs wound d ia g o n a lly w ith s t r i p s of l e a t h e r s e t w ith f i n e , sharp, s t e e l b r i s t l e s . C arding removes rem aining sm all b i t s o f rook and combs th e f ib e r s in to a more o r l e s s p a p a lle d co n d itio n to f a c i l i t a t e sp in n in g . At the time o f t h i s stu d y , th ir ty - o n e roving card u n its and two w lcking card s were being o p e ra te d . A roving card u n it (F igure Y) c o n siste d of two o ard s, a b re ak er o r prim ary card and a f i n i s h e r or roving c a rd . (Take in F igure V) The mixed f i b e r was fed by hand from th e sto ck car to the feed hopper o f th e b reak er c a rd . The s t o c k - r o ll e r wore a r e s p ir a t o r during t h i s o p e ra tio n . The f ib e r passed through th e b re ak er card emerging as a lo o se b lan k et or web. I t was c a r r ie d to the f in is h in g card by a l a t t i c e oonveyor, o r camel back. The f i b e r was s trip p e d from th e l a s t c y lin d e r of the fin is h e r onto a moving le a th e r apron where a s e t o f re c ip ro c a tin g rubbers condenses i t in to loose rovings o f unspun yarn. These rovings are wound oh long "Jack" spools to be taken to the spinning departm ent. The ro v in g s a t th e extrem e ends o f the ca rd s cannot- be used- fo r spinning because they lack uniform th ick n ess. These rovings are co llec te d by two sm all hoods and p n eum atically conveyed to a o o lle o tio n bin fo r r e tu rn to the p re p a ra tio n departm ent. The exhaust system a p p lied to ro ving oards i s shown sc h e m a tic a lly in F igure Y i. The q u a n tity o f a i r exhausted v a rie d from 1100 cfra to 1800 ofm on d i f f e r e n t oarding u n its w ith an average exhaust o f 1440 ofm p e r u n i t . Cards are p a r t i a l l y enclosed and only s u ffic ie n t a i r is exhausted to prevent the escape of dU3t. (Take in Figure VI) Each b re a k e r card i s exhausted a t th ree p o in ts . Hood "3" ex h a u sts from th e top o f the feed hopper o v er th e feed apron. This hopper was enclosed and covered, the cover being l i f t e d during f i l l i n g . About 160 cfm o f a i r were exhausted through the hood. Hood "A" exhausted the to p - f ly from th e en c lo su re covering th e main c a rd in g c y lin d e r. Hood "C" exhausted the bottom -fly from the s e ttlin g chamber under the carding c y lin d e rs . A pproxim ately 285 ofm were exhausted through each of th e se hoods. The f in is h in g card had fo u r exhaust connections besid es the two sm all hoods (G) which removed the w aste ro v in g . Hoods "En and "F" correspond to hoods "A" and "Crt r e s p e c tiv e ly on th e b re ak er card ex h a u s tin g approxim ately 285 cfm. each . The d o f f e r ca rd c y lin d e r, d o ffe r combs and roving apron were exhausted from below through hoods "D^" and nDgn a t 70 ofm eaoh. About 40 ofm was exhausted through each ro v in g c o lle c to r. The volumes o f a i r exhausted through each hood were estim ated on th e b a s is o f p ipe a r e a s . A otual volumes showed wide v a r ia tio n s on different units. Single cards were used in the manufacture o f asbestos wick and ro p esin o e a th ic k roving was d e s ire d . The wick o r rope was tw iste d from the unspun ro v in g . The wioking ca rd s were exhausted a t th ree p o in ts . Approxim ately 380 ofm o f a i r were drawn from under th e feed l a t t i c e , 490 ofm were ex h au sted from the to p o f th e main c y lin d e r co v er to remove th e t o p - f l y and 550 ofm w ere ex h au sted from th e b o tto m -fly s e t t l in g chamber* Dust c o n c e n tra tio n s during card in g averaged 1*7 LI.P.P.C.F. This was a ls o th e av erage exposure o f w icking c a rd o p e r a to rs and w ick and rope tw is te r s . Samples taken near the carding departm ent weight s c a le s showed l e s s th an 0*5 H .P .P .C .F . Card r o l l s were cleaned and ground a t n ig h t except in cases of emergency. C leaning was done w ith hand s c r a p e rs made o f s t r i p s o f c a rd c lo th and the c a rd c y lin d e r was tu rn e d by hand. G rinding was done w ith th e u s u a l type o f card g r in d e r s . The l a r g e . r o l l was ground in p la c e in the carding machine. S lig h tly g re a te r q u a n titie s of a i r were exhausted during g rin d in g due to th e d ecreased lo s3 o f head r e s u ltin g from removal o f th e wooden card covers* The sm all c a rd c y lin d e r s were ground in a grinding fram e. These frames were p a r ti a ll y enclosed and covered w ith a canopy hood ex h a u stin g 2330 ofm p e r g r in d e r . Dust c o n c e n tra tio n s averaged 0.65 & .P.P.C.F. during g rinding. A s p e c ia l run o f a group o f c a rd in g m achines made w ith a l l ex h a u st v e n tila tio n tu rn ed o f f and windows d o s e d showed t h a t d u st c o n c e n tra tio n s s t e a d i l y in c re a s e d . At the end o f one h our th e c o n c e n tra tio n wa3 62.4 I.1.P.P C .F. in the a i r . Under normal o p eratin g c o n d itio n s about 64,000 cfm o f a i r are exhausted from the carding departm ent. This is eq u iv alen t to about 5.5 a i r changes p e r hour d is re g a rd in g n a tu r a l v e n 'tila tio ii through windows on a l l fo u r S id es o f th e room. S p in n in g , T w isting and W inding. 'The yarn aa ro v in g i s tw is te d , o r spun, in to compact th re a d s on e i t h e r rule o r rin g sp in n in g fram es. In t h i s p la n t c o s t o f the sp in n in g was done on m u le -sp in n e rs. The spun th re a d was tr a n s f e r r e d from the sp in n in g s p in d le s t o s p o o ls , on F o ste r Winding -13 machines (sp o o le rs). Spooled thread to be used as f i l l e r (o r woof) in woven o lo th waa rewound on a oop w inder in to oops which w ill f i t in to the loom s h u t t l e s . The rem aining spooled th re a d was reap o o led on t w is te r s which tw is t s e v e ra l th re a d s in to a y a rn . The number o f s tra n d s used determ ined the size of y arn . Both p la in and m e ta llic yarn were tw iste d . M e ta llic yarn c o n ta in s one or more s tra n d s of f in e w ire . P a rt o f the tw is te d y arn was used in c l o t h weaving w hile th e rem aining yarn waa rewound on U n iv e rsa l b in d in g fram es f o r th e m arket. Llile sp in n in g was s e p a ra te d from o th e r o p e r a tio n s in th i s d e p a r t ment by p a r t i a l p a r t i t i o n s . N a tu ra l v e n t i l a t i o n was good and no ex h a u st system s were u s e d . The average d u st c o n c e n tra tio n was 0.85 L .P .P .C .F . w ith a maximum o f 1 .3 I'.P .P .C .P . re c o rd e d . King sp in n in g , cop w inding and u n iv e rs a l winding Machines were lo c a te d in th e same room w ith the tw is tin g m achines. Average exposures in the f i r s t th ree o p eratio n s, which were not them selves e sp e c ia lly dusty, were due to d u st from th e tw is tin g o p e r a tio n . Y?ith th e ex c ep tio n o f a t r i a l exhaust system on one tw is te r , th e rem aining machines were unexhaust ed. The t r i a l system was re p o rte d to be s a t i s f a c t o r y and i s to be i n s ta lle d on a l l tw is tin g m achines. In th is system , the bottom o f the tw is tin g fram e was en clo sed and a t o t a l o f 1700 ofm o f a i r p er machine was drawn downward p a s t th e tw is tin g y a rn s and through f iv e c o n ic a l hoods d istrib u te d along a oentral exhaust duet. Average d u st c o n c e n tra tio n s a t the v a rio u s o p e ra tio n s in t h i s room were rin g spinning - 5 .0 M.P.P.C.F..J cop w inding - 6.9 K .P .P .C .F ., u n iv e r s a l w inding 2 .8 M .P .P,C .F .and tw is tin g 11 .0 L .P .P .C .F . w ith a maximum o f 18.8 L .P .P .C .F . re co rd e d b esid e a tw is tin g fram e. Mo. a o c u ra te measurements o f the e f fic ie n c y o f th e exhaust system on the sin g le exhausted tw ist could be secu red , b u t sim ultaneous samples on both s id e s of th is frame showed a d u st c o n c e n tra tio n o f 18 ,0 M .P .P.C .F . on the s id e toward th e unexhausted tw is tin g frames and a c o n c e n tra tio n o f 6 .3 M .P.P.C .F. on the other sid e . Four F o ste r Winders (sp o o lers) were p a r ti a ll y sep arated from the o th er o p e ra tio n s by p a r t i t i o n s (F ig u re V I I ) . The ex h au st system con s is te d o f an in d iv id u a l c o n ic a l hood around each s p in d le h o ld e r (F ig u re V I I I ) . A pproxim ately 46 ,5 cfm were ex h au sted th ro u g h each hood o r a t o t a l o f 9270 cfm th rough th e 200 hoods on the fo u r sp o o lin g fram es. Dust co n cen tratio n s a t the sp o o lers averaged 2.9 M .P.P.C.F. and in cre ased to 9 .6 M .P.P.C .F. w ith in 30 m inutes a f t e r th e v e n t i l a t i o n was sh u t o f f . (Take in F igure VII & Figure V III) Weaving and In sp e c tio n . C lo th , ta p e , l i s t i n g and brake bands were woven on d i f f e r e n t types o f loom3. In t h i s p l a n t , ex h au st system s had been ap p lied to the dry c lo th looms sin ce th ese were considered to be th e most im p o rtan t source o f d u s t. The d u st c o n tr o l program c a l l s fo r i n s t a l la t io n o f exhaust system on d ry ta p e , l i s t i n g and brake band looms. At p resen t these o p eratio n s are mainly perform ed wet o r p a r ti a ll y w et. Brake band looms were not in o p e ra tio n d u rin g t h i s study. S ig n if i cant d iffe re n c e s could not be noted between dust samples co lle c te d around the v ario u s tape and l i s ti n g looms. Dust co n c en tratio n s ranged from 1.2 to 4 .0 M.P.P.C.F. and averaged 3.0 M .P.P.C.F. N ineteen c lo th looms were in o p e r a tio n i n - t h i s d ep a rtm en t. One o f th ese wa3 a wet loom and u n ex h au sted , fo u r were d ry looms and ex h au sted and th e o th er fo u rte en were exhausted but could be operated eitherT O t or dry . An unexhausted loom i s shown in F ig u re IX . The ex h a u st system -1 5 i s shown s c h e m a tic a lly in F ig u re X. A doubel ex h au st hood drew a i r from (Take in F ig u re XX 5c F ig u re X) under th e warp w hile a seoond hood was a tta c h e d to th e top o f th e loom -lay w ith ex h au st d u c ts ru n n in g down th e s id e o f each p ic k e r arm to an a i r t i g h t swing j o i n t a t th e bottom . The openings in the loom lay* hood con s is te d o f fo u r s lo ts nine inches long by 1 inch wide extending over a space o f fo u r f e e t a c ro ss the woven f a b r i c a t r i g h t an g les to the warp. A t o t a l volume o f ap p ro x im a te ly 10,500 cfm o f a i r was ex h au sted from the e ig h te e n hooded loom s. T his averaged about 580 cfm p e r loom, but s in c e i t was seldom n e o e ssa ry to o p e ra te more th an te n d ry looms a t one tim e, the av erag e q u a n tity o f a i r ex h au sted was c lo s e to 1000 cfm p e r loom. Exhaust dampers were provided on a l l looms and s u f f i c ie n t dampers to b alan c e the system a re c lo se d on wet o r i d l e loom s. The average d u s t exposure o f a weaver o p e ra tin g an e x h a u ste d dry loom was 0 .7 M .P.P.C .F. w hile th e average exposure in u n ex h au sted wet weaving was 2 .6 T.P.P.C.F, Samples tak en b e sid e a d ry , u nexhausted loom showed d u st c o n c e n tra tio n s of 9.6 I'.P .P .C .F . a f te r fo r ty - fiv e m inutes. Average dust co n cen tratio n s d u rin g d ry weaving have been shown as 4 9 .7 !<!.?.P .C .F .^ / 4 Woven c l o t h was in s p e c te d , b ru sh ed and ca le n d e re d on the in s p e c tio n ta b le shown in F ig u re XI. Each o f th e power d riv e n b rushes was p a r t i a l l y en clo sed and ex h a u ste d . A pproxim ately 750 cfm o f a i r were drawn th ro u g h each o f th e two hoods a t the fr o n t o f th e ta b le and about 200 ofm was drawn through th e c le a n in g hood a t th e back o f th e t a b l e . Dust c o n c e n tra tio n s during in sp ectio n averaged 0.5 M .P.P.C.F. A sample taken w hile a r o l l of fa b rio was passed aeroaa th e ta b le w ith o u t b e n e fit o f exhaust showed a d u st c o n c e n tra tio n o f 11 .8 M .P.P.C .F. (Take in Figure XI) < . s If -1 6 - D offing, in sp ectio n and calendering or tap e and l i s ti n g ware hand o p eratio n s and were not exh au sted . Dust co n c en tratio n s of 5 ,0 G.F. were recorded during th e s e o p e r a tio n s b u t th e exposure was interm ittent. C re e le rs had an average exposure o f a b o u t 1 .3 U .P .P .G .F . w h ile p lacin g spools and th rea d in g looms, A t o t a l o f 12200 cfm o f a i r was exhausted from th e weaving de partment corresponding to approxim ately 3 a ir changes per hour, .In cold w eath eri warm a i r was d i s t r i b u t e e through the uepartm ent from a plenum system w hile in warm w eather n a t u r a l v e n t i l a t i o n was secu red th ro u g h u se o f windows on a l l fo u r sid e s o f th e d ep a rtm en t. Other O perations, Other eperations in th is p la n t co n sisted of p ro c e sse s in w hich th e yarn was c h e m ic a lly t r e a t e d and f a b r ic a te d , o r j p ro c e s s e s fo r ch em ically t r e a t i n g o r ru b b e riz in g f a b r ic a te d c lo th * 2Zo. | p o t e n t i a l a s b e s to s h azard was a s s o c ia te d w ith th e se p ro c e sse s w ith the \ ex c ep tio n o f one b ra id in g machine used to make la r g e d ia m e te r a s b e s to s tu b in g . This machine was covered w ith a c o n ic a l canopy hood about s ix fe a t in diam eter through which approxim ately 200 cfm o f a i r were ex h au ste d . A sample taken besid e t h is machine showed a d u st c o n c e n tra tio n of O.-i !.!.?.P .C .F . a t the o p e ra to rs b re a th in g l e v e l . Summary. Table I I g iv e s a summary of th e exh au sted o p e r a tio n s , l i s t* ing th e number o f exhaust d u cts and r a t e o f v e n t i l a t i o n p e r machine, a s vrei; as the average dust co n cen tratio n s to which o p erato rs are exposes. Average dust co ncentrations measured near Corresponding unexhausted operatio n s a re ta b u la te d to show the e f r o c tiv e n e s s of th e c o n tro l m ethod which have been d escrib ed . (Take in Table I I V -1 7 - Conclusion: li This study of a o tu a l r e s u l t s secured by a dust con t r o l program in an asb esto s fa b ric a tin g p la n t i s p resented aa an example o f engineering c o n tro l o f an in d u s tr ia l hazard.jiif A- dequate d a ta have not yet been published to J u s tif y the determ ination of threshold lim its of dustiness which w ill produce asb e sto a is in any d e fin ite period o f time. In the absence of such th re sh o ld values i t is not p o ssib le to decermine p erm issib le lim its of d u stin ess on a medical b a s is , iiav erth a le ss, any ap p reciab le decrease in the amount of a sb e sto s dust w ill cause a decrease in the incidence and s e v e rity of th e r e s u ltin g a s b e s to s is . The e lim in a tio n of a l l the dust in an in d u s tr ia l workroom is r a r e ly necessary from a physioological standpoint and u su ally economically im p rac tica l. Conse q u en tly , a c tu a l atm ospheric co n d itio n s i s an in d u stry r e s u ltin g from the a p p lic a tio n o f p r a c tic a l methods of dust c o n tro l, can be used as temporary standards by th a t in d u stry , / ** t > >t _,_- A 18- REFERENCES 1 / Ris3, H ., and Watson, T. 1 .; "Engineering Geology" ; John Wlloy & Sons, In o .; Bew York; (1937) 2j Fulton, W. B ., Dooley, A., Matthews, J . L . f end Houtz, R. Ij "A 3be3tosia. P a rt I I . ih e Nature and Amount of Dust Encountered in A sbestos F a b ric a tin g P la n ts " ; Spec. B u ll. Ho. 42; Penna. Dept, of Labor and In d u stry ; Sept. 20, 1935. 3 / B loom field, J . J . , and D a lla V a lle , J . 1.; "ih e D eterm ination and C ontrol o f I n d u s tr ia l D ust" ; Pub. H ealth B ull* Ho. 217, A p ril 1935. 4 / Harding, L. A., and 'H illa rd , A. C ., "Heading, V e n tila tio n and Air C o n d itio n in g "; John Wiley and S o n s., I n c .; Hew Y ork;1932. 0 / Unpublished Data, U .S.P.H .3. 6 / H iggins, E ., Lanza, A. J . , Laney, F. B. and Pdca, G. S. " S ilic e o u s Du3t in R elatio n to Pulmonary D isease Amoung diners in th e J o p lin D i s t r i c t , M isso u ri" ; B u ll. 132; U. 3. Bureau o f Idinee, 1917. Population ______- . i,0` .ir1-~ro ----" Prepara tion Crushercan Cotton Openers Asbestos openers Bed Builders ric>or;r.3n Others Cardine 6 Carders 10 3tools Rollers 8 Card Tenders 6 7ick, rope & cord 6 Others Spinning, fo istin g & binding I:ule Spinners Helpers 52 Bing Spinners 6 16 Spoolers 4 Cop T inders 13 Twist3rs 7 Universal Tinders 16 Others having Weavers -Cry Cloth ) Wet Cloth ) n Tape & Listing) Creelers Inspectors Inspectors Others Cloth Tap 18 ( ( 7 Z Z 7 Without xnaust Normal_______ Ventila non, _ ) 3.5* ) 5.4* } 6.7* ) 2.4* ) 4.6* 0.7* 1.7 0.3 0.9 5.0 2.9* 6.9 11.0 2.8 5.0 0.7* 2.7 3.0 1.3 0.5* 3.1 1*3 59.6 (a) 62.4 (a) 40.4 (b) 9.6 (a) 9.6 (a) 11.8 (a) {a} Semple a f t e r one hours operations w ithout ex haust, (b) Sample taken in s id e bin during lo a d in g . * Dust Hxhaust system fo r th is o peration. i T able I I . --Volumes o f A ir E xhausted par Vaohine In V arious O perations In on Asbestos T e x tile P la n t O p eratio n Connections T o ta l Volume o f Dust Cone, Air exhausts w ith per minue Exhaust ( o u . f t . / c i n . ) i'. P. ?. 0 .F . Dust Cone, w ithout xhau31 Asbestos Opener Yib. Screen Cotton Opener fix in g Cede P ic k e r Roving Reopener Fly Willower & Screen Roving Cards Breaker (Primary) F in ish e r 'Ticking Card Card G rinders F o ster Winders* (S p o o le rs) Tw isters Weaving (Broad looms) Brusher C alen d er 2 (*) 1 3 1 3 1 3 (*) 3 3 1 1 (*) 1 2 3 625-1000 ) 700 ) 3.5 2160 - 1025 5.4 2570 6.7 1780 8 1600 1420 ) 1440 ) ) 1.7 1420 ) 2330 0.7 2225 2.9 1700 - 1300 0.7 1650 0.5 1 1 .1 - 5 5 .Oay - 3 .1 -1 0 .6 ^ / 34.3-74.3Sy - 62.4 13.1 / 11.0 4 9 .7 -/ 11.8 --------------* Equipped with, pneumatic conveyor - exhaust th ru conveyor not includ / $ In d iv id u al cone fo r each sp in d le connected to exhaust m anifold. __a/ Unpublished d a ta - o th e r p la n ts ( J . a . D a lla V a lle - U .3 .P .H .S .} \ b / Fulton, e t a l. re f. Zj \ \