Elasto-Plastic FEM Stress Analysis of Pipe Flange Connections Under Internal Pressure

This paper deals with the stress analysis of a pipe flange connection with a spiral wound gasket using the elasto-plastic finite element method taking account the hysteresis and the non-linearity in the stress-strain curve of the spiral wound gasket, when an internal pressure is applied to the pipe flange connections with the different nominal diameters from 2 to 20. The effects of the nominal diameter of the pipe flange on the contact stress distributions at the interfaces are examined. Leakage tests of the pipe flange connections with 3 and 20 nominal diameters were conducted and measurement of the axial bolt force was also performed. The results by the finite element analysis are fairly consistent with the experimental results concerning the variation in the axial bolt force. By using the contact stress distributions and the results of the leakage test, the new gasket constants are evaluated. As a result, it is found that the variations in the contact stress distributions are substantial due to the flange rotation in the pipe flange connections with the larger nominal diameter. In addition, a method to determine the bolt preload for a given tightness parameter is demonstrated.