A flange assembly, consisting of bolts/nuts, washer, gasket and flanges is a complex mechanical system. Existing calculations are mostly based on the Taylor Forge method looking at the allowable stress in the flange and bolts. Only a limited (static) parameters are used to take for example the gasket behavior into account.
A more advanced calculation method is the EN 1591-1. This calculation code is more detailed and considers the behavior of all components. For example the gasket thickness reduces due to the gasket stress imposed by the flanges, the elasticity of the gasket changes with the temperature and others.
The calculation will also give some indication of the expected leak tightness of the flange assembly in addition of the allowable stress check on the components. The method can be used for regular piping flanges but also custom design body flanges for equipment. Red-Bag is member of the EN committee dealing with the EN 1591-1 calculation code.