FEM Stress Analysis and Sealing Performance Evaluation in Pipe Flange Connections with Spiral Wound Gaskets Subjected to External Bending Moments (Case where Internal Fluid is Liquid)

Abstract

The leakage evaluation when gas is used is more severe than that when liquid is used in pipe flange connections. In a practical design, it is also necessary to examine the leakage in the connections under liquid internal pressure application. The contact gasket stress distributions in the connection with a spiral wound gasket subjected to internal pressure and bending moment were analyzed by using elasto-plastic finite element method (FEM) taking account hysteresis and nonlinearity in the stress-strain curve of the gasket. The effects of the initial clamping bolt force (bolt preload), the nominal pressure and the nominal diameter of the pipe flange and the equivalent pressure on the contact gasket stress distributions were examined. The leakage tests for the connections under the bending moment and the internal pressure were also conducted by using liquid (water). By using the results of the leakage tests and the calculated contact gasket stress distributions, the sealing performance of the connections was evaluated. It was found that the sealing performance of the connection can be estimated when liquid (water) was used. In addition, a method for determining the bolt preload in the connections under the bending moments was proposed for the reliable design.