What Are They and Why Are They Needed
What: A stand-alone device that opens and recloses at a pre-selected pressure, containing an orifice sized to flow a required capacity to prevent / avoid overpressure.
Why: All natural gas equipment (pipelines, pressure vessels, air-cooled heat exchangers, compressor cylinders, odorant tanks, instrument control lines, valves, underground storage, industrial-residential-commercial system supply) has a maximum allowable operating pressure (MAOP) rating. Pressure ratings (MAOP) of each piece of equipment may be different. Pressure relief valves with proper application will prevent overpressure above MAOP. Set point is dictated by the lowest MAOP equipment in the system.