-Thanks again Tony
I agree, your explaination make sense. So basically this formula is most appropiate for RTJ-gaskets and maybe spiral wounded but you shouldn't really use it for soft gaskets like graphite gaskets. Normally I check flange leakage with Kellogg method but sometimes it's hard to suceed because the design pressure is equal to the rated flange pressure so it gives you only 50% of rated design pressure left for external bending moments and axial force. Has anyone compared the results from Blick, Kellogg, ASME concerning flange leakage? Or do you use some other methods for flange leakage calc?

D