In designing bolted pipe flange connections with gaskets under internal pressure, it is important to predict an actual residual contact gasket stress in the connections. For estimating the reduced gasket stress, it is needed how to know the load factor of the connections with gaskets. In the previous paper (2017PVP), for predicting the load factor of the connections with gaskets, a new model was proposed using a circular plate theory. However, the rigidity of the flange hub was assumed and it is necessary to improve the model for calculation. In the present paper, a simple and more accurate calculation method is proposed using a circular plate theory taking into account the reaction force distribution at the gasket interfaces and the effect of flange hub. In addition, the effect of the flange hub is analyzed as a couple problem between a cylindrical shell (hub) and a circular plate. The obtained results of the load factor in the connections are in a fairly good agreement with those obtained from FEM. In the numerical calculations, the values of the load factor for JIS 10K flange connections and ASME flange connections with compressed sheet and spiral wound gaskets (from 2” to 24”) are shown. Using the obtained load factor, the residual contact gasket stress and an amount of gas leakage are predicted. For verification of the simple calculation method for obtaining the load factor and FEM results, experiments to measure the load factor and the amount of the leakage were conducted for 24” connection. The calculated results are compared with the experimental method. In addition, an issue how to determine the bolt preload for satisfying a give allowable real rate is demonstrated.

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