Abstract
The contact stress distributions of pipe flange connections with larger nominal diameter (20”) and smaller nominal diameter (3”) including spiral wound gaskets under internal pressure are analyzed taking account non-linearity and hysteresis of the gaskets by using the finite element method (FEM) . The difference in the contact stress distribution is substantial between the pipe flange connections with the 20”nominal diameter and the 3”nominal diameter. The leakage tests were also conducted using the actual pipe flange connections with the 20”nominal diameter and the 3”nominal diameter including the spiral wound gasket. Using the contact stress distributions under the internal pressure, the values of the new gasket constants proposed by PVRC (Pressure Vessel Reseach Council) are estimated by taking account the changes in the contact stress. A difference in the new gasket constants is substantial between the PVRC values and the estimated results, which are obtained by using the initial clamping stress. However, the difference is small between the PVRC values and the estimated values, which are obtained by using the actual gasket stress under the internal pressure. In addition, a method for determining the bolt preload for a given tightness parameter is demonstrated. The differences in the bolt preload between the actual pipe flange connections and the PVRC values are substantial.
