FEM Stress Analysis and the Sealing Performance Evaluation of Pipe Flange Connections Subjected to External Bending Moments and Internal Pressure

In previous study, the characteristics of the pipe flange connections such as the contact gasket stress distribution and the sealing performance of the connection subjected to bending moments are examined. The result suggests that the leakage increases as the bending moment increases. However, a design method for the connection subjected to bending moment is not taken into consideration. The sealing performance of the connection for the different loading history is changed due to non-linearity and hysteresis of non-asbestos gasket. After the pipe flange connections are tightened, bending moment prior to internal pressure is applied due to misalignment of the connections with bolts and nuts. So, it is necessary to examine the difference in the sealing performance due to different loading history and to establish a design method for the connections subjected to bending moment and internal pressure. In this study, the difference in the sealing performance due to different loading history is examined and pipe length in each usage condition is determined for the two loading histories using tensile strength of hub side and allowable leak rate of soppy bubble method to establish a design method of flange subjected to bending moment. The result suggests the average contact gasket stress for the different loading history is changed due to non-linearity and hysteresis of non-asbestos gasket and pipe length in each initial contact gasket stress is determined for the two loading histories.