AXIAL STIFFNESS OF SPIRAL WOUND GASKET WITH PTFE FILLER: KEY DESIGN PARAMETERS

Spiral wound gasket (SWG) is the one type of semi-metallic gaskets, that are widely used in the bolted flange connections of industrial installations to contain fluids and prevent fluid loss. The typical spiral wound gasket consists of a spiral, inner and outer ring. The spiral is constructed of alternating plies of preformed steel tape and a soft non-metallic filler. All of these plies deform, extruding the soft filler axially from between the metal windings as the gasket is compressed, creates the seal against flange faces. The most commonly used materials for soft filler are expanded graphite or polytetrafluoroethylene, known as PTFE. The type of soft filler depends on the application of the gasket. For strong acids or oxidizing atmospheres, only PTFE can be used, but it requires higher assembly stress compared to a spiral wound gasket with expanded graphite filling. Tightness of the spiral wound gasket in the bolted flange connections depends on contact stress between gasket and flange. If the contact stress on the surface spiral wound gasket with flange face is more even, the leakage rate is smaller. For this reason, it turned out to be reasonable to design a spiral wound gasket in which segments of steel tape would maintain a vertical position during compression. The obtained results of this study show that the newly proposed asymmetric profile of the spiral wound gasket provides higher stiffness during axial deformation of the vertical segments and ensures more even contact stress between the gasket and flange.