John,

Thanks for the advice. I can see that the bolts of the flange was going to work by using the spiral wound gasket if the number of bolts were adequate. Or if I was using the different type gasket with lower seating pressure, the bolts were not going to fail.

The problem is coming from the selection of flange class (150#) with the spiral wound gasket without any calculation.

I hope the pipe specifications in the industry are going to be corrected by considering this issue especially for flanges with 150#.

The "Klinger" method that you mentioned, is that the one used in the German Flange Standards?

Best regards,

Ibrahim Demir