Hi everyone,

I have saw many posts for my confusion "seating stress failure of 150# flanges using the spiral wound gasket", but I didn't find the suitable conclusion.
In my analysis results, 150# flanges using the spiral wound gasket of several size shown failure on seating stress of ASME BPVC VIII Div.1 appendix 2 method even without pressure, temperature and external force & moment. It seems to be due to seating stress 'y' specified in ASME code.
I am very surprised and I could not believe this result because many 150# flanges using the spiral wound gasket is normally operating in the numerous sites.

Shall we increase the flange rating to 300# or higher due to seating stress result?
or
Can we remain the 150# flange rating?

I attached the output for 8" and 16" flange leakage check.
Please review and help me anyone.