Introduction to Pressure Relief Devices

Pressure relief devices are a key piece of plant safety. Pressure relief devices are used to prevent overpressure of protected equipment for plant safety, containment of process fluids, and mechanical integrity.  There is also protection for underpressure of protected equipment most commonly in atmospheric storage tanks.  The applicable codes and standards that an engineer will need to become familiar with in order to properly design, size, and install pressure relief devices and relief systems include but are not limited to API 520 Pt I and Pt II, API 521, ASME Sect VIII, API 2000, and ASHRAE 15.  Knowledge of the process operations and start up and shutdown procedures is another element needed for proper pressure relief system design.  The most common relief devices include pressure relief valves or pressure safety valves (PRVs or PSVs), rupture disks, rupture pins, and tank vents.  As pressure relief devices are typically considered the last layer of protection from a safety and containment point of view, proper installation of pressure relief devices is crucial.