Self-acting pressure reducers are simple control valves offering accurate control while being easy to install and maintain. They control the pressure downstream of the valve without requiring pneumatic or electrical control elements.
The DM 3 and DM 4 pressure reducers are medium-controlled weighted-lever valves for medium to large volumes. These valves require no auxiliary energy. Thanks to their integral control characteristics they are very accurate. The time reponse is set by means of an oil-filled damper. DM 3 is a single seat, DM 4 a twin seat valve; both are piston-controlled. The valves can be supplied with soft or hard seals.
When the pipeline is depressurised the valve cone is kept in open position by the weighted lever. As the outlet pressure rises a control piston is pressurised via a pilot line, lifting the lever and moving the valve cone towards the „closed“ position. During normal operation the opening force of the weight and the closing force of the piston balance each other and the pressure reducer operates continually. The outlet pressure is kept constant irrespective of inlet pressure and flow volume. The control pressure is set by changing the weight on the lever.
The maximum outlet pressure must not exceed 1.5 times the set pressure, unless specified otherwise.
In the case of toxic or hazardous media a leakage line must be installed to the control unit capable of draining leaking medium safely and without pressure if the control element should become defective.
The valves requires a sense line (to be installed on-site).