External flange loads and ‘Koves’-method

Abstract

Practical implementation of a much more realistic approach for treating external moments for various major flange assessment methods is proposed. First, the question of how to deal with torsion in flange rings weakened by bolt holes is addressed. This aspect was not covered by the original paper of Mr Koves on which our work is based. That our practical implementations result in quite accurate results is shown by an FEM-analysis of a loose flange ring. Correctly dealing with external moments, usually the major part of external loads on flanges, is important because as soon as design pressures are known, flange ratings are selected and initial designs for ‘custom’ flanges are made. Only in the later stages of a project do all loads on flanges become available and then these external flange loads have to be approved. Usually, the margins between internal pressures and maximum allowable pressures are not large and hence one can ill-afford the wasteful ways that flange assessment methods presently treat external loads.