The Effects of Fluid Media and Environmental Temperatures on the Set-Pressure of Safety Valves

The ASME OM Code provides guidance for set-pressure testing of safety valves. It requires that valves designed to operate on steam, including safety valves that are installed on water-filled loop seal, shall be tested with saturated steam. Alternative compressible fluids are permissible as the test media provided correlations can be developed to substantiate the test. The Code further requires that testing be performed in an environment that is consistent with the installed ambient temperature. This paper presents the results of set-pressure tests of safety valves with nitrogen and steam under controlled environmental temperatures. The results show the ASME Code concerns regarding the test media and ambient temperature considerations are valid.