In variable flow circuits, Differential Pressure Control Valves (DPCV) are used to maintain a constant pressure differential across a sub-branch. This protects downstream control valves from having to operate with excessive pressure differences and neutralises the effects of system pressure variations. 

A DPCV contains a spring-loaded piston and a diaphragm that separates the upper / lower chambers of the valve. The piston is connected to the diaphragm, which closes the valve when differential pressure rises and opens it by the action of the spring, as the differential pressure falls. For those periods of equilibrium between diaphragm pressure and the piston spring, the valve position remains steady. 

Once a sub-branch has been commissioned, a DPCV prevents upset from other parts of the system, making the commissioning process much easier. Test points adjacent to DPCVs are recommended for ease of commissioning and future fault-finding. 

Danfoss self-acting controllers for fitting in return lines. Include impulse connections to the higher-pressure flow lines. 16 models cater for a wide range of system pressures and piping diameters.