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FILE NAME Packings and Gaskets PAG DATE 1991 July DOC PAG007 DOCUMENT DESCRIPTION Journal Article - Exposure to Asbestos from Asbestos Gaskets 01/06/94 12:24 Feature Article 301 462 1039 C 07 07 Exposure to Asbestos from Asbestos Gaskets Robert T. Cheng and Henry J. McDermott Chevron Corporation P.O. Box 7924 San Francisco California 94120 For more than 50 years asbestos gaskets have been used in piping valves pumps and other equipment to prevent leakage of fluids between solid surfaces Although exposure data are available for workers in the gasket manufacturing industry there are no published reports on asbestos exposures for gasket users This article presents data on asbestos exposures during use and handling of asbestos gaskets in the oil and chemical industries Users weighted average exposures to asbestos during re- placement of service gaskets site fabrication cutting of sheet gaskets and handling of new and service gaskets inside Gasket Trailers were all within the Occupational Safety and Health Administration OSHA Permissible Exposure Limit The practice of dry removal of service sheet gaskets followed by dry polishing of the seating surfaces with a power sander could create a short asbestos exposure level in excess of the OSHA Excursion Limit This type of potential short high exposure however can be eliminated simply by wetting the gaskets and seating surfaces 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 by 1991. EPA's decision to ban asbestos gaskets was based solely on exposure data obtained from the gasket manufacturers However asbestos gaskets will continue to be used for many years in the workplace as service 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 Cheng R.T McDermott H.J Exposure to Asbestos from Asbestos Gaskets Appl Occup Environ Hyg 588 5911991 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.S. Environmental Protection Agency EPA issued a final rule banning In stages the manufacture importation processing and distribution in commerce of essentially all asbestos products EPA placed asbestos gaskets under a Stage 2 ban The effective dates for the Stage 2 ban are August 25 1993 for manufacture importation and processing and August 25 1994 for diss 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 ilie EPA's recent action asbestos gaskets will continue to be handled for many years in the workplace as service gaskets are replaced and inventories 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 comain asbestos in the packing material used to seal rotating shafts these are not included in this study Types of Asbestos Gaskets The following three types of gaskets are commonly used in the oil and chemical process plants Sheet gaskets which are typically ... or inch thick compressed asbestos sheets containing at least 70 chrysoule 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 prevention Metal jacketed gaskets which consist of compressed asbestos filler material held within or between metal jacketing jacketed gaskets are primarily used in large heat exchangers or vessel manways Because the asbestos filler material in a jacketed gasket is virtually enclosed by the metal jacket asbestos exposure is not problem for users of jacketed gaskets Therefore the emphasis of this article is on spiral wound gaskets and sheet gaskers BAQ 1047- 0607-53 88 02 6072 -5X 88 @ 1991 AIN APPL OCCUP ENVIRON HYG 7 ' JULY 1991 01/06/94 12:25 fi301 462 1039 C 08 TABLE 1. Workers Asbestos Exposures During Sheet Gasket Fabrication Description of Gasket Fabrication Techniques Long Samples Cutting with power shear and hammer punch Cutting with power shear and wheel culler Cutting with knile on a load surface table Cutting with power shear and hammer punch Culling with power shear and scissors Culling with power shear and hammer punch Cutting with wheel cutler and hammer punch Short Samples Culling with a saber saw Cutting with a saber saw Cutting with power shear and wheel culter Cutting with power sheal and wheel cutter Sample Duration min 330 408 490 344 470 359 465 Concentration fibers 0.015 0.017 0.012 0.009 0.001 0.005 0.003 3388 039 3388 0.33 3388 0.19 30 0.34 Spiral Wound Gaskets Spiral wound gaskets come prefabricated from the man- ufacturers Therefore there are no asbestos exposures related to the site gasket fabrication or alteration During gasket replacement an service spiral wound gasket can be easily lifted from the seating surfaces In fact for a vertically installed spiral wound gasket the old gasket would fall off by its own weight as soon as the seating surfaces are separated the gasket was not held in place Figure ) Before installing the new gaskets workers may wipe the seating surfaces clean with a rag or may remove any corrosion with a wire brush Consequently asbestos fibers remaining on the seating surfaces are disturbed resulting in a brief exposure to airborne asbestos Two duration air samples were collected during replacement of two typical spiral wound gaskets in a piping system The monitoring period covered the lifting and disposal of the old gaskets wire brushing the surfaces of the flanges and installing the new gaskets Results show nondetectable air- borne fiber levels detection limit === 0.06 fiber indi- cating no worker exposure problem during the use and handling of spiral wound gaskets Fabrication of Sheet Gaskets At oil refineries and larger chemical plants asbestos sheet gasket materials are usually purchased in bulk sheets These are later fabricated cut into gaskets of various sizes and shapes the facility's machine shop Various types 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 asbestos exposures during fabrication of sheet gaskets are summarized in Table 1. Seven shift personal air samples collected during the days of sheet gasker fabrication showed that weighted average TWA exposure concentric tons ranged from 0.001 to 0.017 liber well within the 0.2 fiber Permissible Exposure Limit PEL sea by the Occupational Safety and Health Administration OSHA a+ FIGURE 1. Replacing a spiral wound gasket PL OCCUP ENVIRON HYG 7 + JULY 1991 FIGURE 2. Fabricating a sheet gasket 589 01/06/94 12:26 & 301 462 1039 C 09 TABLE 11. Workers Short Asbestos Exposures During Replacement of After- Service Sheet Gaskets Method of Removal and Seating Surface Cleaning Dry removal 2 valve gaskets brushing Dry removal 1 pump gaskel brushing Dry removal 2 llange gaskets brushing Dry removal 2 pipe llange gaskets power sander Wel removal 1 pump gasket brushing Wet removal 2 pipe flange gaskots brushing Sample Duration min 280923 280923 280923 280923 280923 280923 Concentration fibers 0.11 019 033 1.4 < 0.06 < 0.06 Four short air samples collected during the peak action period of gasket fabrication showed that duration exposures ranged from 0.33 to 0.49 fiber which were within the 1.0 fiber OSHA Excursion Limit Although respiratory protection is not required at these exposure levels by the OSHA Asbestos Standard workers are instructed to wear a mask HEPA respirator as a precantionary measure during fabrication of sheet gaskets Replacing Sheet 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 sized 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 service sheet gasket tears and pleces 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 the 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 ex- ceeding the OSHA PEL or Excursion Limit or simply as a precautionary measure workers should be required to wear a face HEPA respirator during dry removal of service sheet gaskets Workers short asbestos exposures were moni- tored at four different refineries and chemical plants dur ing removal of service sheet gaskets Table 11 sum- marizes the monitoring results under two methods of gasker removal and seating surface cleaning i.e. the old method of dry removal and dry surface cleaning and a new method of wet removal and wet surface cleaning Short exposures during the old way of dry removal varied between 0.11 and 0.33 fiber when surface cleaning was done with a scraper and with a wire brush One air sample collected during dry polishing of pipe flanges with a power sander showed 1.4 fibers 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 hour TWA it would no longer meet the current 1.0 fiber OSHA Excursion Limi work method was buter established the removal of service sheet gaskets Typically the work pro cedure calls for the spraying of a solvent 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 asbestos exposures were all below detection detection limit == 0.06 fiber Because very little time and labor are 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 phone management FIGURE 3. Brushing the gasket seating surfaces Gasket Trailer Worker Exposure At some of the larger petrofeum refineries and chemical chemical plants gaskets of all types are kept in a special storage facility called the Gasker Trailer The trailer is staffed by an attendant whose duties are 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 the attendant can be very busy as gaskets in many pieces of equipment are replaced six personal air samples were collected from Gasket Trailer attendamis during two inajor shutdowns an oll refinery 690 APPL OCCUP ENVIRON HYG 7 JULY 1991 01/06/94 12:26 301 462 1039 C 10 practice of dry removal of service sheet gaske , fol lowed by dry polishing of the seating surfaces with a power sander could create a short exposure in excess of the OSHA Excursion Limit This potential exposure however can be controlled by wetting the gasket and the sear ing surfaces prior to gasket replacement FIGURE 4. Spraying a wetting agent Results show the trailer attendants hour TWA exposures ranged from 0.037 to 0.058 liber well within the OSHA MEL Conclusions Exposures to asbestos during site fabrication han- aling 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 acceptable as long as they are still commercially available Replacing service sheet gaskets and cleaning the seating surfaces under wet conditions minimizes fiber release In addition regardless of the exposure level a half HEPA respirator should be provided as a precautionary measure when the seating surface cleaning involves hrushing polishing or sanding or when handling friable asbestoscontaining waste gasket materials References U.S. Environmental Protection Agency 40 CFK Part 763 Asbestos Man ufacture Importation Processing and Distribution in Commerce Pro hibitions Final Itule Fed Reg Vol 54 No. 132 July 12 1989 2. U.S. Department of Labor Occupational Safety and Health Adminis tration 29 CFR Part 1926.58 Asbestos Tremolite Anthophylite and Actinolite Fed Reg Vol 51 No. 119 June 20 1988 amended in Fed Reg Vol 53 No. 178 September 14 1988 Received 6/28/90 review decision 8/13/90 revision 9/10/90 accepted 10/10/90 PL OCCUP ENVIRON HYG 7 + JULY 1991 591