Which test determines the relieving capacity of safety valves?

The accumulation test is designed to determine the relieving capacity of safety valves by simulating a pressure build-up in a system. During this test, the safety valve is subjected to a controlled increase in pressure beyond its setpoint to measure how effectively it can relieve pressure and prevent system overpressure. By assessing the amount of pressure that accumulates before the valve opens and the amount of flow it can handle once it does open, operators can ensure that the safety valve will perform as intended during an actual overpressure condition. This test is critical for verifying that the safety device meets regulatory and safety standards to protect equipment and personnel.

In the context of the other options, the hydrostatic test is used primarily to assess the integrity and strength of a vessel or piping system, while the Orsat test is used for analyzing gas compositions, and the evaporation test assesses the cooling efficiency of systems, none of which directly measure safety valve relieving capacity. The accumulation test stands out as specifically focused on the safety valve's operational parameters, making it the correct choice in this context.