A device that protects a tank or pressure system against pressure increases above its permissible value. Its operation is based on automatic opening at the set pressure value, allowing the entire stream of compressed air supplied to the tank to be released and expanded into the atmosphere. The opening pressure is set by using and properly tensioning the appropriate torsion spring. Valves of this type are subject to supervision and inspection by technical inspection institutions in accordance with local national regulations
(See also, ‘Pressure relief valve’)