The controller is a self-acting differential pressure relief controller primarily for use in district heating systems. The controller is normally closed and opens on rising differential pressure. Ordering Example 1: Differential pressure relief controller; DN 15; kVS 4.0; PN 16; metallic sealing; setting range 0.15-1.2 bar; Tmax 150 °C; flange; – 1× VFG 2 DN 15 valve Code no: 065B2388 – 1× AFPA actuator Code no: 003G1021 – 2× Impulse tube set AF Code no: 003G1391 Products will be delivered separatly. Impulse tube set AF The controller has a control valve, an actuator with one control diaphragm and spring for differential pressure setting. Further on two valve versions are available: VFG 2 with metallic sealing cone; VFG 21 with soft sealing cone