Pressure and temperature of discharging steam at safety valve outlet

摘要

The pressure-temperature rating of the safety valve discharge piping and the size of the silencer at the end of safety valve vent stack depend on the pressure and temperature of the discharge steam leaving safety valves. When a safety valve opens, the steam flows into the safety valve inlet, through the nozzle, annular orifice, body bowl and out to the safety valve outlet. Flowing through the safety valve from the inlet to the outlet, the steam is under a thermodynamics process somewhere betweenconstant enthalpy and constant entropy processes. To find the thermodynamics process which best describes the steam flowing through a safety valve, various processes were reviewed and theoretical results were compared with a series of safety valves test data. Verification tests were conducted on a low pressure 1(1/2)" G-orifice valve and a high pressure 6" R-orifice valve. It was found that the iterative computational procedure presented in this paper gives adequate pressure and temperature estimationfor designers to design the safety valve discharge piping and silencers.