Document B59X5d3YoQwgrd06oOXN4kRkj

I* Feature Article Exposure to Asbestos from Asbestos Gaskets Retort T. Cheng and Henry J. MoDetmoft Chevron Corporttfon, *.0. Rex TWd, ton ftenefee* CeMomte 041*0 fat avert than SO yews, whet fukati btn bant wad In piping. nlvM. pump*, ind ocher oqolpemnt io pctvrnr hifcrgi at fluidi becwttft solid uufxtv Although npeaw to* in Mflato tor orkn In tht fluN niMudktwrlnf toft act no pubUtod npora oo ubnm i^iiwn (W fto-- amu tWi artkto pmrna dm oo ubcMot rxpoeum during use ted handling of ubtttoe yikiti in to oil and cfeemka! kdmtku Ultff dowwtighwd avtraga expoautw to bta* during l* pUcMM of a/Ur-tcrvfct gttott, write ftbrkmioa kwdag) of thim gatef. and handily of orw and itoinHa gwfcwt bride G**ic TrdJtrt win all witMa to OccuftWtiri later and Hrridv Administration <0$HA) teoioWf ImoOtca lifnfe. Thr pnectot of dry ttmsml at ihwmika sMtl to* M lowed by dry pdUhtoc of to aaottofl surfaces fm a aoodm ooto eroatoa tonternt otootoa oxponif* loroftooveoto of to OSHA houraloo UrAto Ihb QfpooffOMMial, tofooacaii Mfh ra>oiwra howrwr. can be ottovfaotcd simply by aiwln to flatoca aod toaring narflma ikIoc tofitot raetoaottot* toJuly 19t9, to U.t. InritViawarri Pftociloa AginrytfPA) prohibited to mamifetuN. hnpomitob piaroHlag, and db- crOwdon to commerce of moot wbnw faritm hr IfH SMh daciifon n ban wboaa pitoti waa baaad aoMf on aoniw dau obtained from to guket mmvfecniafca* Hewno. atoacaa gaskets wlfl canttout to be used far mwyyears to to ewSiplim a Mfratet (otota art tomoved and storing sappllw an to mBsS/Bata from Ala Inwaadfiiloe tuggnt tor asbestosgabs* can bo aatey bandied tfptopw pmcagusos oat frihoed. CttoR Uti UcOemwx, MX: Expossri to Atotooi tom teboom tatosto. Appi Oooup Mm. Hyg. iflei-aiii m *im-w--a*w-wo--n Asbestos gates ere wed extenteyto piping (ftangesx vahea, pumps, end ocher equipment to prevem leakage of fluids between solid ettrfiees. tts high physical strength, host and chemical rcMmance, and reasonable cost mike atocstosi good choice where these features are Impotent In July >989* the U$. Environmental Ffotoctiprt Agency (Ete) taood a Anal rule banning. In stages, the msnufee* lure, importation, processing, and distribution in com merce of *emtally ail ubestos products.0' BRI pieced asbestos gaskets under a Stnge2 ban. The effective dates tor the Stage l ban arc AugiM *5, 1995,.for manufacture, importation, and prcceulng and August 25,1904, tor dto tribute in commerce, bra's deefekm to ban asbestos ga te** was baaed solely on expumue data ot the ssbatos gasket msnufccturtng tocdttics. a scorch of the literature showed no published studies reporting gasket users' u> ' bestos exposures. Despite the BAft reoent action, asbestos gasketa will continue to be handled tor many year* in the workplace as to-aervke gaskets are replaced and inven tories of the remaining asbestos gasket material are used This ankle presents data cn ashotoa exposure! during it* ^2bcsoa gates in toe ott and chem ical industries. Some pump* contain asbestos in toe pack ing materia! used to seal routing shafts; these are nos included m ton study. Type* of Aabaatos Qeekeu The following three types ofgaskets are commonlyused In the oil end dttmkal proceaa plaiuas Sheet gaskets, which are typically Wt or H inch fhkfc comprewed asbestos ahoeu (containing * least 70* chryeotUe asbestos) with Nitrile orffioprene hinder. Spiral around gstes, whkh constat of asbestos flUer wtorlal compcemed between Type 504 Samlets feed spiral wtndli^i The windings are held in place be tween an outside carbon steel compression centering ring and a Type 904 Sukitesa Stcd inner fit*. Spiral around gaskets costmuch more than sheet gates tot provide greater aetlability and better blow-out prevention. Meteldacketed gates, which consist of compressed/, asbestos flller material held within or between metal fetelng. Mctai-Jacketed gsskeu are primarily used in large heat exchangers or vessel manways. Because the asbestos flller material in a metakjateed gmket It virtually enclosed by toe metal Jacket, asbestos exposure la nor a problem for users of meiaHateed gaa'ken. therefore, the emphasis of this article is on spiral wound gates and sheet gaskets. wnanxmemAmzSM a mm AAV UK ' A\ -'L im m MO* NlCHS i . <J' <_0' <J5 i <J** IS.ST.IM) 14*14 NO. 3 202 P. 3 OwcrtstbBrfQasMSsMcsUoRTsclHiquM Uftft-tewfiecm CuShe Bft rase ihar and timer punch 0**c a* pom dee ms wad era* CuMq * we m a W rata m Cud* Sh ssaar Mar art tamer pa* Ovtiaa * arartfear mS Kbm tWSra tom tar 4 ftramr sua* euBra slag 4UW ed NMr sura SlffMfcRSMMl CtaoefcittaiM Ctaotaitamv Oita 4* soar dear an* M ata Ota sfe sasar Osar ana raaal ata feme* OuratfaM m ISO 409 410 144 4M m m is IS so 10 tSMMMt dbsracd 001$ aoir eoit UN 0001 0003 0003 1.3ft 0J3 t* ft04 Spiral Wound Owkett Spiral wound gaskets come prafrbrioited from the manufkturera. Therefore, there ere no tshexux exposures m* tiled to the onstite gasket fabrication or alicmJoa During gasket replacement, an after-service apirtl wound gvket can be easily lifted from the totting turfeex. In fea. fbr ucnlmUy Installed eptrnl wound gasket, the old gBtcei would bit off by Is own weight s soon is the seating surfeces are sepuioed Ifthegasket wa not held m place (Figure 1> Defers tnaufling the newgasket*, worker* may wipe the anting surikce* dean with a rag or may remove any cor ruriun with a wfte bruit). Consequently, asbestos Abort remaining on the seutlng surfaces are disturbed, resulting in brfrf exposure so tlrboroe aflbeuts.`Hvo ihon^lucarion air simples were collected during replacement oftwo typ ical spiral wound gasket* in a piping system. The monitormg period covered the lifting and disposal of the old gaskets, wire brushing ties surbees of Ute Range*, and Installing the new gusketa. Hesults show nondetectable a^ borne fiber levels (detection limit oud fihenee). indl* rating no worker exposure problem during the umi and handling of spiral wound gaskets. Fgbrtottion of Shod Gaskets to oil refineries and larger chemical pious, ashostui sheetgasket materials are usuallypurchased in bulksheets. These are later fabricated (cut) imogaskew ofvartoussixes tnd stupes at me bdhty's machine shop, various type* of equipment and took, including power shears, hammer punch, whed cuticr, knife, and saber iw, may he used 1ft the bbrfcadon process (Figure 2). Workers* asbenus exposurcs during fabrication of sheet gafcecs are summa rized tn Table!. Seven fu!l-*htft, peraonal air sample* rul. tetxd during the dais & stews grata ^briCAton rtowvd dot time'weti;r.-d 'average (TWb) exposure concentra tions nngod from 0.001 to 0.017 Rberttc, well wkhin the 04 ftbente FermUnlbte exposure Limit (F8L) out by the Occupational Safety and health Admlnbarnkm (OSHA)^' nouaci. ftgmrtno t trim mum pitm rx- awisour.cmvmsm.eraM AxvtMt 1 wusit nwaunsimatsMtet. l i'tOfl MtlKt is.as. tm 1* 19 NO, J UWI Uferfcsrt' Ot#ft*Tsm Mb*** ftpowrw During R*4*c*tHM * AAsrUrtm ******* WstwS si foetsto aai leasni tortara QmH Dry fwwtt | raw gtsai. raismwrato . dry --eat Hwg grim. ******** tty mmk t sks wmwtm. tow mto wmrawwtitrafaui warn, brake fompb ton** m 19 *6 S' 3 10 It Cswontratoi gbwifed All 119 MS 1.4 <016 <006 S, 4 four short-term tir samples cufleeted during foe peak ae* don period of grata fabrication showed dot shortdunttan exposures ranged from 033 to M9 fiber/ce, afcich were within the 1$ fibet/ec OSHA Excursion Umfc.<,`Although respfraocy protection ii not required * these exposure level* by the OSHA Asbestos Standard. worker* ere kv atructcd to wear a half-mask 1JBM respirator a* * precau* tionary measure during fabrication of sheet pastas. nimlarlnn fihsai Oaaknte The Job of replacing sheet gariera is generally e rimv duration task, lasting from several minute* for replacing small pipe ftu$e grata In (be Held to-slightly under one hour for replacing a large^tred pump gasket in the shop. The sheet gasket* are under tremendous setting stress (eg., 10W Pl) during service, and they may be in contact with oxJdtadng or corrosive fluids. As the seating surfaces are separated, sometimes the after-aervice sheet garitet team, and pieces of the brdcee gMket mated*! stick Ujthdy to one or both of the seating surfaces. A flat screw driver, putty knife, nr scraper is used to lift the broken gasket off the meta), followed by scraping, brushing! polishing, or even aanefing to clean the setting surfaces before instaiKng the new gasket (Figure 9X When this cleaning is done In dry condfUon*, asbestos fibers can become airborne to create a potential inhalation hoard To guard against e* deeding foe OSHA pa. or Excursion limfc, or simply m a precautionary measure, workers should be required to wear s half-face HEM respirator during dry femoral of aftcrcrvlce sheet gaskets. Workers' short-term asbestos cyosurcs win morri* tored at four different refineries and chemical plans dur* ing removal of afiur-servfce sheet gaskets. T&U sum- marfao* the monitoring results under two methods ofgrata remorai and seating surface cleaning, be* the old method ofdry removal and d^r surface derating and a new method of wet removal, and wet surface cleaning. Short-term'ex posure* during the old way ofdry removal variedbetween dll and 033 fiberfcc when surface dcaning w* done tah a scraper amtawfeh a wire brudt. One air sample, colloaedduriAgdrypoilshing ofpipe flangeswithapower sender, rimvred U fiberricc for a task that lasted for 2$ minutes. Although that particular air sample was coOeoed in 1986 and was in compliance with the then applicable OSHA pel ofOJfibcntc (gbourTnO.lt would no longer meot the current 1.0 flber/cc OSHA Excursion Umk. Awet>worie method was tecr established forthe remoral of rilewieivlce sheet gaxkets. Typically, foe wet-wrek pro- eadure calls for tl>e iprv^ of a Mbcnrtnacd wetting agent (eg.. Chesterton 723 Spnaoho Penetrating Ofl) to wet the gaAet and the seating surfaces before removing and cleaning (Figure O- Monitoring results Indicate that, when the wet method is employed, workers* ahoruerra asbosos exposures were all below detection (detection limit 0.0$ ftbe&cc). Because very Itrie time end labor re involved, and a spray can of wetting agent Is e9 die material that is required, the wetworit method for gasket replacement is wcU received by workers and by plant management ~ fttuva. inMint to print ssrifo arts*. Qtefcet TraUr Worker Exposure At aooK ofthe larger petroleum refineriesandchemical plants, gaskets of ail types are kept In a apeeial storage facility called the Grata Trailer. The trailer Is staffed by tti auendmt %4xe duties are to maintain an inventor of grakeut. to collect and dispose of used gaskets, end to dfeertbutc new gaskets to other worker* During unit shut down and turnaround time, the attendant can bevery busy a* gaskets in many pleceaof equipmentarc replaced. Six personal air samples were collected from Gasket Trailer wtcndtnu during two major shutdowns at an oil refinery. m m.am*CMMMMtt* Asttan i * r*Orf NfCHS l*3/ldO/'3l dTitfto 1991 16*lf HO. S 204 9. 0 prate of dry removal of lAcr-urMce sheet gukcu, Cl^ lowed by dry' polishing oftlw resttagsuffice* with t power lander, could create short^cmi exposure in excess of (he OSHA excursion limit. This pdendal exposure, how* ever, can be controlled by wetting the gasket and the scat' tag urfteea prior to gasket replacement. ftaoommendatton* Asbestos gadocting material* play an important role where (heir special Mures arc needed Their use remains ac ceptable long as they are still commercially available. Replacing afteMcivioe sheet gaskets and cleaning the acat* tagatirfiioes under wet conditions minimixes fiber release. In addition, regardles* of the exposure level, a haltece HEM respirator rfxxikj be provided as a precautionary measure when the seating surface droning involves bnahtag, polirfitag. or sanding, or when handllty filahle adwarecontaining waste gwket materials. . t RtKfMOM l I > Results show die nailer attendants* Wtourra exposures ranged from 0.0J7 M$$ ftbetfee, Ml within the OSIU PEL U OX WnlwnmaKd IHuK-qfc*iaastwyi 40 CWtfm SiS. Adww Mn stature, Jrrpunxkxi, ProcrMinx and attribution n Comweicc ft- ItetiaMi (tad US MA w.Vol H Me. I (My tk ISSSk L ox pspsruntw ot iMtot, oetuptaonri ataxy and ttonx uhawta tMkxii at ent n*t iSS&Sft: Mtmm, tremolos, AMhofAyUw; and C^^MMtedVUWlVlMfWI ^ anuwtac. red. aea mx st, Na it* ounc sx iasi)i aeienScd u tad. than. MX 4}. Nu. I7 (flepteodwr tilSSSX tepuaures to asbestos during onehc fitbricadon, han dling, and replacement ofgaskets can be otttatained well below the OSHA ns. wuft good wotfc practices. The past aueswee gawoo: >e<new oeemon grtMM; sewtetew wrtseo. eswnre tgrtd^g i am. sea* mmsmi mo ttn . mvwm f ***EHD* fill