Gaskets are materials used to seal one compartment of a device ...

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During this time period, estimated domestic production declined 99.7 percent, from 952.34 to 3 short tons and fiber consumption declined 99.8 percent, from 877.54 to 2.1 short tons (ICF l986a, ICF 1985, TSCA 1982). In 1986, Durametallic Corporation, which accounted for two-third of the total output for asbestos packings in 1985, ceased processing because of costly insurance premiums and the possibility of regulatory action (ICF 1986a). D. Substitutes Asbestos-containing packings, the large majority of which are based on various compositions and configurations of braided yarn, have dominated the market until very recently. A typical high performance braided asbestos packing includes an alloy wire reinforcement, various lubricants, a zinc powder corrosion inhibitor, and a graphite powder lubricant coating on the yarn itself (Union Carbide 1987). In addition, these packings may contain various binders (e.g., elastomers or resins), fillers (e.g., mica, clay, or asbestos) and dry lubricants (Monsanto 1987). Asbestos fibers have been used to make the braided jackets for packings because of the favorable qualities that asbestos imparts to products made from it. Asbestos-containing packings are ideally suited for high temperature and pressure, as well as corrosive environments. Braided asbestos packings show good acid/fire resistance, low thermal conductivity, and molten metal resistance. Asbestos also withstands fairly high pressures (up to 4500 psi at room temperature) and exhibits good tensile strength and abrasion resistance (Klein 1987). Another property of asbestos packings that has made them a standard in the packing industry is their good compressibility and recovery (EPRI 1982). The packing industry has been unable to find a single substitute for asbestos that can reproduce its numerous qualities. Hence, manufacturers have - -11-
een forced to replace the asbestos fiber with a combination of substitute materials, including cellulose, aramid, PBI, PTFE, glass, and graphite fibers. The formulations of the substitute products most often include a combination of more than one type of substitute fiber and fillers in order to reproduce the properties of asbestos necessary for a particular application. Formulation of substitute products is done on an application-byapplication basis by each manufacturer (ICF l986a) and for the purposes of this analysis, substitute products will be classified according to the fiber with the largest percentage in content. The substitute products can be grouped into six major categories according to the type of non-asbestos substitute used: 3 a Aramid fiber mixtures, • Glass fiber mixtures, a PBI fiber mixtures, • PTFE mixtures, • Graphite mixtures, and • Other fiber mixtures including cellulose, phosphate, and ceramic (ICF l986a, Palmetto Packing 1986, Monsanto 1987). The current market share for the different substitute formulations has been estimated as indicated in Table 4. 1. Aramid Mixture Aramid fibers act as a reinforcing fiber in asbestos free packings and other materials. They are not as heat resistant as asbestos (500°F),but are quite strong and flexible amd can withstand mild acids and alkalies (A.W. Chesterton 1982). Kevlar(R) and Nomex(R) produced by DuPont Corporation are The grade or the fiber and style of the packing used (e.g., square braid, braid-over-braid) determine the pressure rating for all applications. Any substitute fiber can be formulated into a packing that will meet most pressure requirements, but temperature and chemical limitations may dictate the selection of a partic~.darfiber for a particular application. - -12-
Page 1 and 2: XXVII. SHEET GASKETS A. Product Des
Page 3 and 4: Table 1. Fluid and Pressure Ranges
Page 5 and 6: $20.5 million in 1985, based on an
Page 7 and 8: Table 3. Substitutes for Asbestos S
Page 9 and 10: Aramid gaskets are usually composed
Page 11 and 12: esistance. A wire insert is often a
Page 13 and 14: 6. Ceramic Fiber Mixtures Ceramic f
Page 15 and 16: REFERENCES Carborundum. 1986. Produ
Page 17 and 18: Bulk Square braád Rolled (over cor
Page 19 and 20: Table 1. Standards of Asbestos Yarn
Page 21 and 22: A. ‘I’ A. ‘-I PRESSURE ~ Movi
Page 23 and 24: Table 2. Operating Conditions and U
Page 25: Table 3. Production of Asbestos Pac
Page 29 and 30: Table 4. Estimated Market Share for
Page 31 and 32: useful temperature limit of approxi
Page 33 and 34: 6. Other Substitute Fibers Other fi
Page 35 and 36: Table 6. Data Inputs for Asbestos R
Page 37 and 38: TSCA Section 8(a) submission. 1982.
Page 39 and 40: a viscosity control for waterproofi
Page 41 and 42: Table 1. Production of Asbestos Roo
Page 43 and 44: or talc. The additives ease grindin
Page 45 and 46: Table 2. Manufacturers of Cellulose
Page 47 and 48: Cellulose bodied roof coatings and
Page 49 and 50: equivalent basis, they are favored
Page 51 and 52: compounds. These formulations have,
Page 53 and 54: . Other Roof Coatings and Cements O
Page 55 and 56: Table 4. Data Inputs for Asbestos R
Page 57 and 58: ATTACHMENT B PROJECTED PRICES ANALY
Page 59: ICF Incorporated. 1986 (July-Decemb

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