Spiral Wound Gaskets
Spiral Wound Gasket Basics
Spiral wound gaskets are metallic gaskets consisting of an outer centering ring (also known as OCR, OR, or an outer guide ring), metallic windings with a soft filler material, and a solid inner ring, or any combination of the three. A spiral wound gasket is the most common metallic gasket used in industrial plants. A properly selected and installed spiral wound gasket can withstand high temperatures and pressures, preventing leaks throughout their intended lifespan. Spiral wound gaskets can handle more harsh and varied operating conditions than non-asbestos sheet gaskets in general.
Metallic Outer Ring
Ensures proper positioning and prevents over-compression.
Metallic Inner Ring
Protects sealing element from high temperatures; prevents turbulences in piping and protects flange from corrosion; prevents the inward buckling of the spiral element.
Metallic Winding with Soft Filler Material
The soft filler material acts as the sealing element, with the metal providing structural support.
Spiral Wound Gasket Materials
Spiral Wound Gaskets are available in multiple materials and configurations, which play a role in the suitability of the gaskets in different applications, such as enhancing resistance to corrosion from environmental elements or chemicals.
Filler Material
Some common spiral wound gasket filler materials are listed below. This is not an exhaustive list, but does cover some of the most prevalent options.
Flexible Graphite
Provides soft conforming material in fire-safe design with excellent chemical resistance. Typically rated to 842°F (450°C), but is dependent on the specific manufacturer.
PTFE
Polytetrafluoroethylene provides superior chemical resistance and great sealing ability. Typically rated to approximately 500°F (260°C), but is dependent on the specific manufacturer.
XHR
Extreme heat resistance. Uses combination of mica barriers and APX2 to provide exceptional sealing ability to 1500°F (815°C), but is dependent on the specific manufacturer.
Metallic Gasket Material for Winding Strip / Inner Ring / Outer Ring
Some common spiral wound gasket construction materials are listed below. This is not an exhaustive list, but does cover some of the most prevalent options.
The inner and outer rings of a spiral wound gasket may be the same material of the winding strip, or a different one, or may be different from one another.
Alloy with 18% Cr and 8% Ni is the material most used in the manufacturing of industrial gaskets due to its excellent resistance to corrosion, low cost and availability in the market.
This alloy with 18% Ni, 13% Cr and 2% Mo, offers excellent resistance to corrosion beyond that of 304 Stainless Steel.
Carbon Steel
xCommon, economical material for the manufacture of the outer ring as contact with the process fluid is limited. Low resistance to corrosion, including atmospheric corrosion.