s removed from service, it is usually taken to the shop for inspection and repair.
An important phase of maintenance is testing to determine the set pressure and tightness of the valve “as received”
and after its overhaul. The testing is usually performed on a test block with facilities for applying pressure to a valve
and indicating the pressure applied. Most test blocks have facilities for testing with either air or water to simulate, as
closely as possible, the media handled by safety and relief valves, respectively. Bottled nitrogen may be used instead,
especially for high-pressure valves. See ASME BPVC Section I, Section IV, and Section VIII, for requirements on
setting safety valves and pressure-relief valves in steam service