Document x1KrXQ8EQ28onjJvpqaVqEga0

FILE NAME Packings and Gaskets PAG DATE 1992 DOC PAG012 DOCUMENT DESCRIPTION Journal Article Asbestos Gasket Materials A Close Example of the Surfaces of A Close Examination of the Surfaces of Asbestos Gasket Materials James R. Millette and Richard S. Brown MVA Inc. Keywords Asbestos chrysotile gaskets scanning electron microscopy ABSTRACT Gaskets containing asbestos are considered non able materials However a recently published study has shown that handling containing gaskets can release asbestos fibers into the air especially when the gaskets are handled dry A close examination of the surfaces of four unused gaskets showed that although most of the asbestos is bound within an organic binder uncoated asbestos fibers were present on the surface and on the edges of the gas- kets which would be released as free fibers with mild abrasion INTRODUCTION In assessing the condition of containing building materials ACBM for their potential to release asbestos fibers one fairly simple test is to determine whether or not the material is friable If an containing material ACM can be crumbled by hand pressure the material is considered friable and certain precautions are advised when the material is handled Chunks of fireproofing material which can be crushed to dust by hand are considered friable but containing sheet gasket materials which are composed of asbestos in an organic binder are not considered friable However friability may not be the only factor to consider 5500 Oakbrook Parkway Suite 200 Norcross GA 30093 when determining the potential for asbestos fiber release If asbestos fibers are protruding from product mild abrasion may dislodge the fibers without reducing the product to dust A recent study found that asbestos fibers could be released from asbestos gaskets under certain conditions 1 The authors reported that the practice of dry removal of service sheet gaskets followed by dry polishing of the seating surfaces with a power sander could create short term asbestos exposure levels in excess of the Excursion Limit 0.1 fibers centimeter established by the Occupational Safety and Health Administration OSHA The study showed that site fabrication cutting of sheet gaskets and handling new and service gaskets also released asbestos fibers into the air but at lower levels Wetting the gaskets during handling was found to minimize the release of asbestos fibers ASBESTOS GASKETS According to the United States Environmental Protection Agency USEPA gaskets are materials used to seal one compartment of a device from another in applications such as engine and exhaust manifolds Asbestos gaskets are used mainly to seal connections and prevent leakage of fluids between solid surfaces 2 Gaskets often consisting of more than 70 chrysotile asbestos are often used against alkaline neutral or weak acid solutions Blue asbestos crocidolite is often present in compressed sheet gaskets when pipes carry strong mineral acids Sheet gaskets commonly used in condensate and steam lines such as are found in power plants are composed of chrysotile asbestos compressed sheet 131 with styrene butadiene rubber or other binder 3 Other organic binders used in making asbestos gas- kets include natural rubber buna and buna synthetic rubbers 4 or neoprene 1 MICROSCOPICAL EXAMINATION In order to investigate the reason for the asbestos release during handling four unused gaskets were obtained for microscopical examination Two of the samples were circular gasket material Figure 1 and two were flat samples The gaskets were photographed as received and sections were carefully cut from each gasket under a High Efficiency Particle Absolute HEPA filtered exhaust hood The sections were carbon coated and gold coated for examination by scanning electron microscopy SEM utilizing a Philips 525 SEM equipped with an EDAX PV9900 energy dispersive ray spectrometer SEMEDS All imaging was performed on the flat sur- Figure 1. Photograph of an unused circular gasket after sections were removed A inch 15 cm ruler is shown for scale faces and edges of the gaskets in an received condition No abrasive materials were used to pre- pare the gaskets for SEM Chrysotile asbestos fibers were found protrud- ing from the flat surfaces and edges of all four gaskets tested Representative views of the flat and edge surfaces of a circular gasket and a sample of the flat gasket material are shown in Figures 2-13 The higher magnification images show that within the bundles and clumps of chrysotile mixed with the organic binder are thinner chrysotile fibers which are not coated by the binder These inner fibers are available to be released into the atmosphere when abrasive activities are applied to the gasket surfaces CONCLUSIONS The secondary electron images illustrate why when working with sheet gasket materials under certain dry conditions asbestos fibers can become airborne and create short exposures in excess of the OSHA Excursion Limit Not all asbestos fibers are bound in the organic matrix Documentation of asbestos fibers protruding from the surfaces of nonfriable containing gaskets reinforces the need to work with them under wet conditions to minimize fiber release References 1. Cheng R.T. and H.J. McDermott Exposure to Asbestos from Asbestos Gaskets Appl Occup Environ Hyg 6 588-591 1991 2. United States Environmental Protection Agency USEPA 40 CFR Part 763 Asbestos Manufacture Importation Processing and Distribution in Commerce Prohibition Final Rule CFR 312 29496 July 12 1989 3. Bowler W.J. Hows and Whys of Packing and Gaskets Paper Trade Journal October 11 1965 4. USEPA Asbestos Publication of Identifying Information Notice CFR 5153 Feb. 13 1990 Figures 2-13 follow on pp 133-135 132 MICROSCOPE am oo kV 374E1 1992/25 MVA Figure 2. Secondary electron SE image of an outside edge of a circular gas- ket Bar = 1 mm Wa 2.0kV 3.00EZ 1994/25 MUA Figure 3. SE image showing chrysotile fiber bundles and chrysotile fibers pro- truding from the gasket edge shown in Figure 2. Bar = 0.1 mm JAMES MILET and 121 120E3 1995/25 MVA RICHAD 12.1kU 3.74E1 1997/25 MVA S. Figure 4. SE image showing a higher magnification view of a portion of the 133 133 133 field in Figure 3. Bar = 10 micrometers Figure 5. SE image ofa surface of a circular gasket Bar = 1 mm BROWN 134 12.1kV 300E2 1998/25 MVA Figure 6. SE image showing chrysotile fiber bundles and chrysotile fibers protruding from the circular gasket surface shown in Figure 5. Bar = 0.1 mm 2,0120E3 19/25 1999/25 MVA Figure 7. SE image showing a higher magnification view ofa portion of the field in Figure 6. Bar = 10 micrometers MICROSPE 199 374E1 2000/25 MVA 19 2 Figure 8. SE image of an outside edge ofa piece of gasket sheet material Bar 40 mm 73) ae * 20,0 3.00E2 2001/25 MVA Figure 9. SE image showing chrysotile fiber bundles and chrysotile fibers protruding from the gasket material edge shown in Figure 8. Bar = 0.1 mm we ee st 200 120E3 " 2002/25 . MVA - - . ui : > 1mm200kV 374E1 2003/25 MVA Figure 10. SE image showing a higher magnification view of a portion of the fieldinFigurFeigure 9. Bar=10 micrometers Figure 11. SE image of a surface of a piece of gasket sheet material Bar = 1 JAMES R. MILET and 200 RICHAD 300E2 2004/25 MVA chrysotile Figure 12. SE image showing chrysotile fiber bundles and 10 200 120E3 2005/25 MVA S. fibers Figure 13. SEimage showing a higher magnification view of a portion of the _ BROWN protruding from the gasket sheet material surface shown in Figure 11. Bar = 135 0.1 mm 135 field in Figure 12. Bar = 10 micrometers