Self-acting Pressure Controllers are used in district heating systems. It can maintain a constant differential pressure across and ensure stable flow conditions. It is normally closed and opens on rising pressure. It has control valve, actuator with one control diaphragm and a spring for pressure setting. It comes in connection sizes ranging from 1/2″ all the way up to 6″ with numerous temperature ranges and materials of construction. These are available as single seat design for tight shut-off as well as double seat design.