Maintenance should be performed on a regular basis. An initial inspection interval of no longer than 12 months is recommended. The user must establish an appropriate inspection interval depending on the service conditions, the condition of the valve and the level of performance desired.
The ASME Boiler and Pressure Vessel Code does not require nor address testing installed valves. The only thing the codes states are design and installation requirements, such as some valves must have a lifting lever.
For instance, for Section VIII: “Each pressure relief valve on air, water over 140F, or steam service shall have a substantial lifting device which when activated will release the seating force on the disk when the pressure relief valve is subjected to a pressure of at least 75% of the set pressure of the valve”.