What is the proper way to install a safety or safety relief valve (SRV)?

Mount SRVs in a vertical, upright position. Installing an SRV in any position other than vertical (within plus or minus one degree) will induce misalignment of moving parts, which will adversely affect its operation and may even reduce the service life. The inlet piping should be fastened directly to the valve inlet, without any interference from other equipment. Piping length should not exceed the face-to-face dimension of a standard tee of the same pressure class of the valve. Inlet piping should never be smaller in diameter than the inlet connection of the valve.

Pressure drop from the vessel to the valve should not exceed 3% of valve set pressure when the valve is at full-flow capacity. Excessive pressure drop at the inlet of the SRV will cause extremely rapid opening and closing of the valve, which is known as “chattering.” This can result in lowered flow capacity and may damage the valve’s seating surfaces SRV inlets should not be located where excessive turbulence is present, near elbows, tees, bends, orifice plates or throttling valves. The outlet piping must not be reduced from the nominal outlet size of the valve; it should be designed to compensate for expansion (if required) and must be fully supported.

Stress distortion of the valve body may cause misalignment of the internal components, causing leakage. When two or more valves are piped to discharge into a common header, the built-up backpressure resulting from the opening of one or more valves may cause a superimposed backpressure in the remaining valves. Valve function, overpressure and flow capacity reduction must be considered when designing common collection systems.