Substituting a stainless steel fitting grade is easy on paper and expensive in the field. This walks through what actually changes when you move between SA-182 forged grades and SA-403 wrought fitting grades: carbon limits, nickel and molybdenum ranges, strength minima and what the welding procedure has to survive.

Sour service is defined by hydrogen sulfide in a wet environment, and the failure it causes is not a leak. It is a brittle, invisible crack that can develop in…