(9a) Selection of Pressure Relief Valves for Pressure Vessels

This session will review the factors important for selecting relief valves for pressure vessels. Only pressure relief valves will be discussed. The primary relief valves compared are spring-loaded-conventional, spring loaded balanced (bellows, diaphragm, piston), pilot-operated-modulating and pilot-operated-snap acting. Other devices, such as rupture disks, buckling pins, super-sonic relief valves, tank devices, poppet-vent valves, axial-flow valves, gas-assisted valves, etc. will not be included. The comparison will cover basic parameters as operation, inlet pressure effects, backpressure, trim, fluid types and phase released, and cryogenic service. In particular, the nuances for special situations will be outlined. The contrast between ASME sizing parameters and AP Standard 526 sizing will be evaluated.