The development of a procedure for the operation of block valves on both inlet and outlet of PSV.
Check with the local jurisdiction for their rules. If they don't provide guidance, you can consider the following points from California regulations.
(3) Stop valves may be installed between a pressure relief valve device and the operating vessel for the purposes of inspection, repair and/or replacement of the pressure relief device. Where stop valves are installed, the employer shall develop, implement, and maintain a written plan containing all of the following:
(A) Procedures to ensure that stop valves are open and locked or sealed during normal operations and are not to be closed except by a qualified person(s).
NOTE: In the case of multiple relief device installations having spare capacity or spare relief valves, the stop valve can be closed on the inactive relief valves providing sufficient system relief capacity is maintained.
(B) Procedures to minimize the frequency of closing stop valves while the vessel is in service. Stop valves shall remain open and locked or sealed until a replacement pressure relief device is available for installation.
Exception: Stop valves may be closed for emergencies such as pressure relief device failure.
(C) Procedures to ensure that a replacement pressure relieving device or needed replacement parts are readily available prior to closing the stop valve and removing the pressure relief device. An index for the location of all stop valves subject to this section shall be maintained.
(D) Before the removal of a pressure relief device from operating equipment, facility management shall review and approve a written operations plan for closing the stop valves.

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