Low pressure relief valves control primary pressure (p1, ahead the valve). Low pressure relief valves ZM-B/D and LPS/D are controlling protective gas or inert gas to isolate processes from contamination by atmospheric oxygen.
ZM-B/D and LPS/D is a spring loaded differential pressure relief valve with reference to actual atmospheric pressure via a sensor hole to ambient. Under non operating conditions, the atmospheric pressure and the adjustable range spring close the valve via and a stem. Under operating conditions, gas enters from primary (p1) to the valve seat and reaches counter side of diaphragm via an internal pulse line. So, differential pressure is exactly in balance with atmospheric pressure and the force of adjustable range spring. The valve will be opened as soon as primary (p1) raises set point of adjustable range screw. Valves will be closed with primary (p1) below set point for constant back pressure service. Valves seat tightness is at least according to VDI/VDE 2174. Option external pulse line is compensating dynamic pressure drop in longer pipes. Best performance with pulse line pick-up directly at process. Optional D-connection is used for pilot line connection in case of dome loaded service (high pressure blanketing). ZM-B/D and LPS/D is vacuum-proof, manufactured in decreasing design and uses no external energy.
The back pressure relief valve ZM-B/D and LPS/D works similar to ZM-B and LPS. But in addition, a
dome pressure of up to 2000 mbar relative can be applied via “D-connection”.
So the regulator can be used with higher reference pressure to "blow-out" vessels for example. A pneumatic control unit can be offered and delivered accordingly.