Document 06R3JaRq363Q04KaQnEqq25jk

SECTION 15 EXPOSURE TO ASBESTOS FROM ASBESTOS GASKETS Robert T Cheng Henry J. McDermott July 1991 APPLIED OCCUPATIONAL AND ENVIRONMENTAL HYGIENE Volume 6 Number 7 July 1991 Editor In Chief Jeffrey S. lee University of Utah Assistant Editor in Chief J. Thomas Pierce Central Missouri State University Editorial 566 Message from the Chair Features 583 Asbestos Contamination of Abatement Equipment Surfaces Hurry J. Beaulieu 588 Exposure to Asbestos from Asbestos Gaskets Kolxrrt T. Cheng and Henry J. McDermott Staff Editor Slviron K. Ziegler Assistant Editor Karen M. Stewart Advertising Coordinator MkhaeUtnn Kelley Applied Occupational and EmirOfimcntai Hygiene 6500 Glenway Avenue, Building I>-7 Cincinnati, Ohm 4521 M43 TcleplKMie: (513) 66I-7HHI TAX: (513) 661-7195 Articles 592 Solvent Desorption from Carbon Bed* Ln Ducted and Nonducted Laboratory Fume Hoods Setxt 1). Keindg, Nunan A. Esmen, Scrap Ertlul, and Erie B. Sansone 59 Reduction In Airborne Silicon Carbide Whiskers by Process Improvements Gerald P. Beaumont 604 Size Characteristics of Particles Released from Broths Man Juan Pan. Wlodzimierz Piladnskl, Krzysztof W. Szewcv^-k, Uslm Krishnan, and Klaus Willeke 608 Capture, Digitization, and Enhancement of Videotape Frames foe Industrial Hygiene Appllcadons Sara R. McDonald and Steven P. Levine Applied Industrial Hygiene, Inc. Publisher William I). Kelley Business Manager John F. Ilcuvtcr Publixfctd by Applied Industrie) Hygi. for tke AmtricM Coaisrsncs d Governmestei Indoilriei Hygienists Departments 567 From Our Readers 573 Case Studies 575 Conference Summary 577 Ergonomics in Mining 58i Ventilation News Digest 616 Notice of Intended Change--Guidelines for the Classification of Occupational Carcinogens 621 Notice of Intended Change--Carbon Monoxide 625 Nodcc of Intended Change--TrimelUtlc Anhydride 628 Notice of Intended Change--4-VInylcyclohcxene 633 New Products 635 Available New Literature 636 Ad Index Classifieds AfrL occur. (NV)(K)H HY6 kO) juv.t mi B63 Feature Article Exposure to Asbestos from Asbestos Gaskets Robert T. Cheng and Henry J. McDermott Chevron Corporation, P.O. Box 7924. San Francisco. California 94120 For rnorf than 50 year*. *bsto* g*skecs hsv* b^n used In piping, vmjvci, pump*, and other equipment to pnrrent leakage of fluid* between solid surfaces. Although exposure data are a-raj labIe for workers in the gasket manufacturing industry, ther# art no published reports on asbestos exposure* for gasket users. This article presents data on asbestos exposures during use and handling of asbestos gaskets in the oil and chemical industries. User*' time-weighted average exposures to asbestos during re placement of after-**rvice gaskets, on-site fabrication (cutting) of sheet gaskets, and handling of new and after-serrice gaskets inside Gasket Trailers were all within the Occupational Safety and Health Administration (OSIJA) Permissible Exposure Limit. The practice of dry removal of ftr-*ervic sheet gaskets, fol lowed by dry polishing of the seating surfaces with a power sandcr, could create a short-term asbestos exposure level in excess of the OSHA Excursion Limit. This type of potential, short-term, high exposure, however, can be eliminated simply by wetting the gaskets and seating surface* prior to gasket replacement. In July 1989, the U.S. Environmental Protection Agency (EPA) prohibited the manufacture, importation, processing, and dis tribution in commerce of most asbestos gaskets bf 1994. EPA'* decision to ban asbestos gaskets was based Solely on exposure data obtained from the gaskci manufacturers. However, asbestos gaskets will continue to be used for many years in the workplace as tn-serricc gaskets are removed and existing supplies are in stalled. Data from this investigation suggest that asbestos gaskets can be safely handled if proper procedures are followed. CbSOfl. R.T.; McOtrmotl HJj Exposur* to A5tto from Mbcrtoi Gaskets. AppL Occup. Emlron. Hyg. 6:586-591; 1991. Introduction Asbestos gaskets are used extensively in piping (flanges), valves, pumps, and other equipment to prevent leakage of fluids between solid surfaces. Its high physical strength, heat and chemical resistance, and reasonable cost make asbestos a good choice where these features are Important. In July 1989. the U.5. Environmental Protection Agency (Eft\) Issued a final rule banning, In Mages, the manufac ture, Importation, processing, and distribution In com merce of essentially all asbestos products/1 * BRA placed asbestos gaskets under a Suge 2 ban. The effective dates for the Stage 2 ban arc August Z5, 1993. for manufacture. Importation, and processing and August 25, 1994, for dis tribution In commerce EPA's decision to ban asbestos gas kets was based solely on exposure data at the asbestos gasket manufacturing facilities. A search of the literature showed no published studies reporting gasket users' as bestos exposures. Despite the EPA's recent action, asbestos gaskets will continue to be handled for many years In the workplace as In-service gaskets arc replaced and Inven tories of the remaining asbestos gasket material are used This article presents data on asbestos exposures during use and handling of asbestos gaskets In the oil and chem ical Industries. Some pumps contain asbestos In the pack ing material used to seal rotating shafts; these are not Included In this study. Types of Asbestos Gaskets The following three types of gaskets arc commonly used In the oil and chemical process plants: Sheet gaskets, which are typically V4 or V Inch thick compressed asbestos sheets (containing at least 70% chry5odle asbestos) with Nitrile or Neoprene binder. Spiral wound gaskets, which consist of asbestos filler material compressed between Type 304 Stainless Steel spiral windings. The windings are held In place be tween an outside carbon steel compression centering ring and a Type 304 Stainless Steel Inner ring. Spiral wound gaskets cost much more than sheet gaskets but provide greater scalability and better blow-out prevention. . Metal-Jacketed gaskets, which consist of compressed asbestos filler material held within or between metal jacketing. Metal-Jacketed gaskets are primarily used In large heal exchangers or vessel manways. Because the asbestos filler material In a metal-lacketed gasket is virtually enclosed by the metal Jacket, asbestos exposure is not a problem for users of metal-Jacketed gas kets. Therefore, the emphasis of this article Is on spiral wound gaskets and sheet gaskets. 688 !M7-mxmA>W7-S*m.CW4 I Ml AJH Am. occur, fsvwon wre. tOI - Jtitr mi TAfLE 1. Worker*1 Asbeafaa Expoauro Ourktg She* Gulwt Fabrication Oeacrlption of Gaafcat Fabrication Tocftnfguoa Long-Term Samples Cutting with power shear and hammer punch Cutting with power shear and wheel cutler Cutting wim knife on i lead surface table Cutting with power shear and hammer punch Cutting with power shear and scissors Cutting with power shear and hammer punch Cutting wllh whed cutter and hammer punch Short-Term Samples Cutting with a saber saw Cutting with a atxt saw Cutting with power shear and wheel cutter Cutting wilh power shear and wheel cutter Sample Duration (min) 330 408 490 311 170 359 165 55 55 30 30 Concentration (fitma/cc) 0015 0.017 0012 0.009 0.001 0005 0003 039 0.33 0.19 0.31 Spiral Wound Gookata Spiral wound gaskets come prefabricated from the man ufacturers. Therefore, there are no asbestos exposures re lated to the on-site gasket fabrication or alteration. During gasket replacement, an after-service spiral wound gasket can be easily lifted from the seating surfaces. In fact, for a vertically Installed spiral wound gasket, the okI gasket would fall off by its own weight as soon as the seating surfaces arc separated if the gasket was not held In place (Ftp/ I). Before Installing die new gaskets, workers may wijjc die seating surfaces clean with a rag or may remove any cor rosion with a wire brush. Conscquendy, asbestos fibers remaining on the seadng surfaces are disturbed, resulting in a brief exposure to airborne asbestos. 'I'wo short-duration air samples were collected during replacement of two typ ical spiral wound gaskets In a piping system. The moni toring period covered the lifting and disposal of the old gaskets, wire brushing the surfaces of the flanges, and installing (he new gaskets. Results show nondetectable air borne fiber levels (detection limit = 0.06 fiber/cc), indi cating no worker exposure problem during the use and handling of spiral wound gaskets. Fabrication of Shaat Gaakatt At oil refineries and larger chemical plants, asbestos sheet gasket materials are usually purchased in bulk sheets, iheseare later fabricated (cut) into gaskets of various sizes and shapes at (he facility's machine shop. Various typos of equipment and tools. Including power shears, hammer punch, wheel cutter, knife, and saber saw, may be used In the fabrication process (Figure 2). Workers' xsliestos ex posures during fabrication of sheet gaskets are summa rized in Table I. Seven full-shift, personal air samples col lected during the days of sheet gasket fabrication showed that time-weighted average (TWA) exposure * neentradoos ranged from 0.001 to 0.017 fibcr/cc, well within the 0.2 fiber/cc Permissible Exposure Limit (PEI.) set by the Occupational Safety and Health Administration (OSHA).u* RGU 1. Replacing a spiral wound gasiart. APPL 0CCUP ENVIRON. HTO. 1171 JU1Y 1931 FIGURE 2. Fabricating a sheet gasket t>89 Method of lUmraf and Surface Cfan*ng Dry ranowfc 2 vaht pisfatt, scnpinybnrshing Dry removat 1 pump tpsket, scrspinybwshlnq Ofy removal: 2 (Ungt gaskets soaptogtaushing Dry remove! 2 pipe ftwge grsWvpowtf sancter Wet ramOYtt l pomp gasket. stxjpingrtxustilng Wtt removal 2 pipe ftangc octets, brushing S*<npw Dvritton (*4 19 ffi 55 25 30 15 (fflmt/cc} 0.11 0.19 0.33 1.4 <0.00 <0.06 Four short-ierm air samples collected during the peak ac tion period of gasket fabrication showed that short-duration exposures ranged from 0.33 to 0.49 fiber/cc, which were within the 1.0 fiber/cc OSHA Excursion Limit/2* Although respiratory'protection Is not required at these exposure levels by the OSHA Asbestos Standard, workers arc In structed to wear a half-mask HEfA respirator as a precau tionary measure during fabrication of sheet gaskets. Replacing Shet Gaskets The job of replacing sheet gaskets is generally a shortduration task, lasting from several minutes for replacing a small pipe flange gasket in the field to slightly under one hour for replacing a large-sited pump gasket in the shop. The sheet gaskets are under tremendous seating stress (e.g., 10,000 psi) during service, and they may be in contact with oxidizing or corrosive fluids. As the sealing surfaces are separated, sometimes the after-service sheet gasket tears, and pieces of the broken gasket material stick tightly to one or both of the seating surfaces. A flat screw driver, putty knife, or scraper Is used to lift the broken gasket off the metal, followed by scraping, brushing, polishing, or even sanding to clean die seating surfaces before installing the new gasket (Figure 3). When this cleaning Is done in dry conditions, asbestos fibers can become airborne to create a potential inhalation hazard. To guard against cx- ceedlng the OSHA PEL or Excursion Limk, or simply as a precautionary measure, workers should be required to wear a half-face HEft\ respirator during dry removal of after-service sheet gaskets. - Workers' short-term asbestos exposures were moni tored at four different refineries and chemical plants dur ing removal of after-service sheet gaskets. Table II sum marizes the monitoring results under two methods of gasket removal and seating surface cleaning, Lc., the old method ofdry removal and dry surface cleaning and a new method of wet removal and wet surface cleaning. Short-term ex posures during the old way of dry removal varied between 0.11 and 0.33 fiber/cc wiien surface cleaning was done with a scraper and'or with a wire brush. One air sample, collected during dry polishing ofpipe flanges with a power sander, showed 1.4 fibers/cc for a task that lasted for 25 minutes. Although that particular air sample was collected in 1986 and was In compliance with the then applicable OSHA PEL of 0.2 fiber/cc (8-hour TWA), It would no longer meet the current 1.0 fibcr/cc OSHA Excursion Limit A wet-work method was later established for the removal of after-service sheet gaskets. Typically, the wet-work pro cedure calls for the spraying of a solvent-based wetting agent (e.g,, Chesterton 723 Sprasolvo Penetrating Oil) to wet the gasket and the seating surfaces before removing and cleaning (Figure 4). Monitoring results indicate that, when the wet method Is employed, workers' short-term asbestos exposures were all below detection (detection limit = 0.06 fiber/cc). Because very little time and labor arc Involved, and a spray can of wetting agent Is all the material that Is required, the wet-work method for gasket replacement Is well received by workers and by plant management. HGVRE 1 Brushing tiie gistei sitting iurf*c. Gasket Trailer Worker Exposure At some of the larger petroleum refineries and chemical plants, gaskets of all types are kept In a special storage facility called the Gasket Trailer. The trailer Is staffed by an attendant whose duties arc to maintain an Inventory of gaskets, to collect and dispose of used gaskets, and to distribute new gaskets to other workers. During unit shut down and turnaround time, die attendant can be very busy as gaskets in many pieces of equipment are replaced. Six personal air .samples were collected from Gasket Trailer attendants during two major shutdowns at an oil refinery. 590 APPL OCOJP. OVYIlKN. HYS. tn\ JIXT 1*81 practice ot cry removal of afier-servlce sheet gaskets, fol lowed by dry polishing of the seating surfaces with a power sander, could create a short-term exposure in excess of the OSHA Excursion Llmlc. This potential exposure, how ever. can be controlled by wetting the gasket and the seat ing surfaces prior to gasket replacement. RGUR 4. spraying a writing agent Results show the trailer attendants' &-hour TWA exposures ranged from 0.037 to 0.058 fiber/cc, well within the OSHA PEL Conclusions Exposures to asbestos during on-site fabrication, han dling, and replacement of gaskets can be maintained well below the OSHA PEL with good work practices. The past Recommendations Asbestos gasketing materials play an Important role where their special features are needed. Their use remains ac ceptable as long as they arc still commercially available. Replacing after-service sheet gaskets and cleaning the seat ing surfaces under wet conditions minimizes fiber release. In addition, regardless of the exposure level, a half-face HEPA respirator should be provided as a precautionary measure when the seating surface cleaning involves brush ing, polishing, or sanding, or when handling friable asbestoscontaining waste gasket materials. References 1. U-S. Environmental Protection Agency; 40 CFR Part 763, Asbesto6: Man ufacture, Importation. Processing, and Distribution in Commerce Pmhlbltlotui Final Rule. Fed. Reg. VoL 54, No. 132 (July 12. 199). 2. US. Department of Labor, Occupational Safety and Health Adminis tration: 29 CFR Pan 1926.58: Asbestos, TrcmoJUe. Anihophyiitc, and Actlnolke. Fed. Reg. VoL 51. No. 119 0urt<: 20, 1988): amended In Fed. Reg. Vol. 53, No-178 (September 14.1988). Racer**! 6/24/90; revfcw 8*dsfon 8/13/90; ravkloo 9/10/90; Kcaptad 10/10/90 Afn. occup. environ, wra. un JtAt 1531 591