The self-acting differential pressure relief controllers and pressure relief controllers are primarily for use in district heating systems. The controllers open on rising differential pressure or pressure. The controllers have a control valve, an actuator with control diaphragm and a spring for differential pressure setting.
Function of the controller: the diaphragm in the controller regulates the differential pressure the valve according to the effect, which the spring power has on the diaphragm. The valve is normally closed and opens at rising differential pressure.