We have a client in the U.S. who has purchased a facility and is telling us that they do not need to have PSV calculations redone for some parts of the process. We are of the opinion that recalculations are required because the process is changing. The previous owners made fermentation broth with algae in water and the new owners are making fermentation broth with bacteria in water. A lot of equipment is being reused. Flows, pressures, and temperature may or may not be changing. The client has asked for a code or standard that says they are required to redo the calculations.
Does anybody know of a U.S. code, standard, regulation, etc. that specifically states when recalculations are required? I cannot find anything concrete in API 520, 521 or ASME VIII, but I'm sure I missed it somewhere.
Thank you.