SA-193 Gr.B7M bolt material used in Wet H2S service is not passing requirement of UG44b clause.

[KD007]

Hello All,

I have to design high pressure vessel as per Div 1 for wet H2S service in which bolt material requirement is to use 'M' grade material for bolt i.e SA-193 Gr.B7M. However when using UG44b for flange derating the B7M bolting is not fulfilling the requirement of having higher allowable strength than SA193 B8 Cl.2.

Kindly advise if there is any other CS bolt alternative with higher allowable strength and availability in M grade for sour service.?

 

[IdanPV]

Have you considered the usage of Code Case 2901?
As for the bolt material, we use SA354 Grade BD when need higher strength (steam service)

 

[TGS4]

Code case 2901-1 won't help you - it has the same bolting restrictions. Do you need to go with B7M bolting? Or would B8 bolting suffice?

 

[KD007]

Code case 2901-1 won't help you - it has the same bolting restrictions. Do you need to go with B7M bolting? Or would B8 bolting suffice?

Hello TGS4, Yes you are right code case 2901-1 wont help. The vessel which I am designing is carbon steel vessel for which I guess typically we have used B7M bolting only. Can we use B8M (S.S) bolting in CS vessel with wet H2S service?
Isnt there any other CS bolting grade with higher allowable to be used for sour service?