Hi,

I would like to ask about the effective gasket width “b” in appendix 2 of ASME VIII

Based on the Pressure Equivalent Method, the diameter of effective gasket reaction “G” depends on the value of “b”.

“b” is dependent on the basic gasket seating width “bo”

When performing Peq method in CII, the default values of “G” (“Read from File…”) are generally the “mean diameter” of “spiral wound gasket”.

I checked the “bo” of spiral wound gaskets (outside and inside diameters from B16.20) and I found out that bo>6 mm from DN6 and above, which means that the values of “G” should not be the “mean diameter” but rather “outside diameter less 2b”.

Please throw some light if I am missing something in the appendix 2 or in CII default values, or it’s just that the default “G” values are just for reference only. Now I also have flat gaskets and ring joints to deal with, and I am planning to change every values of “G” if my understanding in Appendix 2 is correct.

I checked the CII procedure in flange leak check based on ASME VIII, that if I input the correct inside and outside diameters of gasket, the correct values of G will appear.

What I’ve found out is if we consider the “mean diameter” we are actually dealing with a more conservative case, which is good at some point.

You are correct, the default values are as you assumed, the mean diameter. You'll notice there is no place to define the type of flange or gasket on this dialog, therefore CAESAR II doesn't know "b0" or "2b". If you have a better value for "G", over-ride the value CAESAR II puts in that edit box.

thanks Richard!