Design for optimum gasket assembly stress and leak rate control in bolted gasketed joints

Abstract

The behavioural factors affecting the design of a bolted gasketed joint for a prescribed leak rate are described. The traditional approach is now known to be ill founded while the proposed alternative has disadvantages. These approaches are outlined and their problems described. An improved design method is presented, on the basis of a design chart. In this the optimum gasket assembly stress to achieve a given level of leak tightness is plotted against the known gasket stress change as the fluid pressure is applied, giving curves for a series of leak-tightness values. The design chart can be derived graphically from a Pressure Vessel Research Council (PVRC) ‘ROTT’ test-data plot or by calculation from the PVRC gasket coefficients Gb, a and Gs; the procedures are described. The approach presented has the advantages of simplicity and accuracy. Examples of the new design chart are given for ten types of gasket and the effects of varying individual PVRC gasket coefficients are demonstrated.