"When an overpressure event occurs in the piping or facility, an automated on--off safety valve shuts down the system immediately. Pressure Safety Valves (PSVs) are included in the design of processing facilities to protect assets such as piping and vessels by relieving system pressures during abnormal plant conditions. PSVs are safety-critical devices, and there may easily be hundreds of them installed on a plant depending on the size and complexity of same. In most countries, industries are legally required to protect pressure vessels and other equipment by using relief valves. Also, in most countries, equipment design codes such as those provided by the ASME, API and other organizations like ISO (ISO 4126) must be complied with. These codes include design standards for relief valves and schedules for periodic inspection and testing after valves have been removed by the company engineer"-- Provided by publisher.