Stress analysis and the new gasket factors of pipe flange connections with spiral wound gaskets subjected to internal pressure ( Comparison of the characteristics in gas types between helium and nitrogen)

摘要

This paper deals with the stress analysis of pipe flange connections with spiral wound gaskets using axisymmetric theory of elasticity, when an internal pressure of helium and nitrogen is applied to the connection in which two pipe flanges are clamped together by bolts and nuts with an initial clamping force. In addition, an axial bolt force and the contact stress distributions are analyzed when an internal pressure is applied to the connections. Using the contact stress distribution, an internal pressure when leakage occurs and the new gasket factor are estimated. In the numerical calculations, the effect of the Young's modulus and the thickness of gaskets on the contact stress distributions at the interfaces are clarified. Leakage tests were conducted and measurement of the axial bolt force was performed. The analytical results are compared with the experimental ones concerning the variation in the axial bolt force. The effects of gas types (helium and nitrogen) on the sealing performance and the gasket factors are examined by comparing the values of the gasket factors obtained from room temperature tightness test (ROTT). Discussion on the sealing performance and the new gasket factors between helium and nitrogen gas is made.