Bolt Force to Flatten Warped Flanges

Abstract

Initial lack of flatness of the flanges of pipe connectors can result in leakage if the bolt loads are not sufficient to achieve positive gasket compression at all points on the circumference. Equations are presented for computing the magnitude of the bolt load necessary to flatten the flange. Account is taken of the bending and twisting resistance of the flange itself, the membrane and hoop bending restraint afforded by the pipe, and the fact that the bolt circle is displaced from the gasket circle. The analysis applies to flanges whose warping can be adequately described by considering it to vary as cos 2θ. Numerical examples are considered for several typical flanges.