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.?

 

[r6155]

I don't remember exactly, but in some designs we used a higher-class flange.
An alternative (in nuclear) uses a Weld Gasket (see Flexitallic Design Criteria).