Pressure Reducing/Sustaining Valve
Pressure Reducing/Sustaining valves are piloted hydraulic valves, activated by line pressure and controlled by pilots. Both pilots have spring-loaded diaphragms. One pilot is responsive to upstream pressure and the other to downstream pressure. The combined operation of the two pilot valves sustains the preset minimum upstream pressure of the valve, and at the same time, reduces the downstream pressure to a preset maximum pressure. The valve opens or closes gradually to maintain both required pressures simultaneously.
Use the pressure reducing/sustaining valve to define two pressure zones along a supply line. Typically, this occurs along a downhill flow.
- 3-way plastic piloted Pressure Reducing/Sustaining valve. Plastic pilot is used for 2” -6” sizes with pressure rating up to 145 PSI (10 bar).
- 2-way pressure Reducing/Sustaining valve with pressure rating up to 232 PSI (16 bars).
Adjust the pressure set points with the adjusting screws on the pilots.
The Pressure Reducing/Sustaining valve is activated by the line pressure and controlled by two pilot valves. Both pilots include spring-loaded diaphragms. The sustaining pilot is preset to sustain the upstream pressure at a preset point. The reducing pilot reduces the downstream pressure and maintains it at a lower preset level. Under normal flow conditions, the valve is partly open to sustain the upstream pressure and reduce the downstream pressure. It partly closes when the downstream pressure rises above the lower set point or when the line pressure drops below the upper set point. It opens again when the upstream pressure rises. In 3-way pilot configurations, the control chamber of the valve drains out to atmosphere, enabling the valve to fully open. In 2-way pilot configurations the control chamber drains downstream, enabling faster reaction time and gradual opening without water discharge.
Manual: Use the three-way selector to close or open the valve by turning the handle to C (closed) or O (open) positions.
Automatic: Position the three-way selector handle to A (automatic). When the upstream pressure is low, the line pressure flows through ports 2-3 of the sustaining pilot and flows into the valve's control chamber. The valve closes to sustain upstream pressure. When the upstream pressure reaches the set point, the diaphragm of the reducing pilot moves upward and connects ports 2-3 . The control chamber drains through the sustaining pilot and exits port 2 of the reducing pilot. The valve then opens to the preset downstream pressure. When the downstream pressure is greater then the desired level, the reducing pilot's diaphragm moves up, allowing water to flow into the control chamber through ports 4-3 of the sustaining pilot.
Manual: To open the valve, open isolation valves 1 and 2 . To close the valve close the downstream isolation valve. The upstream isolation valve should remain open.
Automatic: When the upstream pressure is low, the control chamber is connected through the 2-way sustaining pilot to the line pressure and the valve closes. When the line pressure rises and overcomes the spring of the sustaining pilot, the pilot's membrane moves upward to open port 5 (outlet downstream). The control chamber then drains downstream through the 2-way reducing pilot. The valve then opens and reduces the upstream pressure. As the line pressure is reduced, the sustaining pilot closes, as does the valve. If the downstream pressure is greater than the set point of the reducing pilot, the reducing pilot's membrane moves upward and closes port 1 or 2 (outlet downstream). The control chamber is connected to the upstream pressure and the valve closes.