Material of safety relief valve body

[srijey]

In most safety relief valve construction, the service fluid does not come in continuous contact with the body material. Is it an acceptable practice to design the pressure relieving valve body based on pressure and temperature alone ignoring the fluid corrosion/erosion properties? I have not seen any API std touches this part. For instance, a 9Cr piping can have SA 316 WCB body on relief valve with matching flange rating.

 

[gr2vessels]

I'm not aware of specific design requirement for the body of relief valve material selection, but the piping spec prevails over other considerations. You cannot use a lower grade material for any piping component than listed in the piping spec. In the case you mentioned, the 316 material has a higher corrosion resistance rating than the pipe material and that is technically acceptable, if feasible.
Cheers,
gr2vessels

 

[srijey]

Thank you GR2vessels. I repent on my slip- It should be A216 WCB not 316 - pardon my inept typing. My question is around that piping or vessel spec. Do they govern the safety relief valve body when they are not exposed directly to operating fluid. Most of the safety relief valve design have superior metallurgy only for wetted components. I only question the valve body. As I said before, in some areas, we do have Safety relief valves not conforming to vessel or piping metallurgy!