The 106-RPS and 206-RPS Pressure Sustaining Valves from HMA Flow & Industrial are based on the model 106-PG or 206-PG main valve. The 81-RP pilot senses the upstream pressure through a connection to the valve inlet. The valve and pilot remain closed until the inlet pressure exceeds the pilot setting. Under flowing conditions, the pilot reacts to small changes in pressure to control the valve position by modulating the pressure above the diaphragm. Should the upstream pressure fall below the setpoint, the valve will close or modulate to ensure that the set-point is maintained. The valves ensure minimum upstream pressure for critical use, with easily-adjustable pressure setting, and closes if inlet pressure drops below the set-point.