Is it acceptable to use in-situ hydraulic testing methods in lieu of removing, dismantling, inspecting, re-assembling and bench testing PSV's installed on a high pressure ASME Section I power boiler?
The answer is no, if you want a full certified test.
It might be that a visual test and a simple functional test within pressure limits allowed for the connected vessel parts might be done for certain PSV types, but what does the local authorities require of tests and certifications?