A computational procedure for the stress and deformation analysis of high-pressure vessel flanges

Abstract

A computational procedure is presented for the analysis of stress and deformation patterns in high-pressure vessel flanges. (Typically light-water nuclear reactor vessel flanges.) The suggested computer model utilises an assemblage of basic shell- and rigid ring elements. The integral flange assembly is schematised, including the bolts which are treated as rectangular beams with equivalent bending and tensioning properties. Particular attention is paid to the local gasket face behaviour. Both mechanical and (transient) thermal loadings are considered, the first including bolt-tightening and subsequent pressurising. The (three-dimensional) calculation of temperature fields, preceding the structural analysis for thermal loads, is also discussed. A sample problem for a transient thermal loading condition is presented, illustrating the thermal ‘bolt-lag’ effect in a nuclear vessel during start-up and stop.