Spiral wound gaskets are different from common type of gaskets. They consist of three layers which are the outer ring, winding and inner ring. Figure shows the structural view of spiral wound gasket.
The spiral wound gasket is semi-metallic, comprising of a spirally wound V-shaped or W-shaped stainless steel strip and a non-metallic filler material, such as graphite or PTFE. On the gasket, a solid outer ring is used for centering and controlling compression. This minimizes the risk of material creep through over-tightening. For the toughest conditions, spiral wound gaskets are available with an additional inner ring. This protects the windings (particularly the filler), from contamination or attack by products travelling past the pipeline joint. Spiral wound gasket are made in different materials of fillers and strip. They can be differentiate with the color code on its outer ring. Table below shows the color code and its material.