Spiral Wound Gaskets – ASME B16.20

A spiral wound gasket is a pre-formed V-shaped metal strip wound together with a soft filler tape. The metal spiral gives the joint spring-back and recovery under pressure and temperature cycling, while the filler fills flange-face imperfections and makes the seal. It is the standard choice for raised-face flanges in hydrocarbon, steam and chemical service. Styles: SW (sealing element only) for tongue-and-groove and male/female faces, valve bonnets and pressure-vessel covers where the gasket is located by the joint itself — not for plain raised-face pipe flanges. SW-IR (with inner ring): the inner ring backs up the windings against inward buckling and keeps them out of the flow; for male/female joints, not for plain raised-face flanges. SW-CR (with centering ring): the most common style for raised-face pipe flanges; the outer ring locates the gasket inside the bolt circle, limits compression and stops outward blow-out; not normally used with PTFE filler. SW-IR/CR (inner and centering rings): specified for PTFE filler; NPS 24+ in Class 900, NPS 12+ in Class 1500 and NPS 4+ in Class 2500; and for socket-weld, lapped, weld-neck and integral flanges on raised faces. Marking to ASME B16.20: manufacturer's name or trademark · nominal pipe size and pressure class · winding metal and filler material · inner ring material (when not SS304) · outer ring material (when not carbon steel) · ASME B16.20. Example: MANUFACTURER · 4" 150 · 316L / FG · ASME B16.20 · SS304 I.R. Packing: each gasket is supplied vacuum-sealed flat on corrugated fibreboard to protect the windings in transit. To order, state: NPS and class · flange standard · style (SW, SW-IR, SW-CR, SW-IR/CR) · winding metal · filler · inner and outer ring materials · quantity.