Full definition
A static sealing element die-cut from flat sheet material and compressed between two flanges to prevent leakage of fluids or gases. The gasket material must be softer than the flange faces to conform to surface imperfections and create a seal. Materials by ascending temperature and pressure capability: (1) Rubber sheet (NR, SBR, NBR, EPDM, CR, silicone, FKM) — up to 100-200°C, 10-20 bar, selected by chemical compatibility. (2) Compressed non-asbestos fiber (CNF — aramid/glass fiber in nitrile or SBR binder) — up to 250°C, 40 bar, general industrial. (3) Flexible graphite sheet (Grafoil/Sigraflex) — -200 to +650°C, 100+ bar, excellent chemical resistance. (4) PTFE sheet — -200 to +260°C, universal chemical resistance, low friction, but cold flows under sustained load. (5) Metal (soft iron, copper, stainless) — highest temperature and pressure. Per ASME B16.21 (non-metallic flat gaskets for ASME flanges). Thickness: typically 1.5-3 mm for rubber, 0.5-3 mm for CNF and graphite. Bolt torque must achieve minimum gasket seating stress without exceeding crush limit. Gasket factors (m and y) per ASME BPVC Section VIII define minimum bolt load requirements. Brands: Garlock, Klinger, Flexitallic, Gore (PTFE).