Pressure Sustaining Valves (PSVs) — also known as backpressure valves — are control valves that maintain a minimum upstream pressure in a system. Unlike pressure reducing valves (which control downstream pressure), PSVs ensure that the pressure upstream of the valve does not drop below a set value.
How They Work
- A PSV remains closed or partially open until the upstream pressure exceeds the setpoint.
- If the upstream pressure falls below the setpoint, the valve closes to sustain pressure in that area.
- Often pilot-operated or spring-loaded, similar to PRVs.
Applications
- Pump protection
- Prevents cavitation by maintaining pressure at the pump outlet.
- Zoned distribution systems
- Ensures pressure in high-priority zones (like firefighting systems).
- Hydraulic and gas systems
- Maintains backpressure for operational control or stability.
- Water treatment and supply
- Controls upstream tank or reservoir levels.
Key Differences: PSV vs PRV
Feature | PRV (Pressure Reducing Valve) | PSV (Pressure Sustaining Valve) |
---|
Controls | Downstream pressure | Upstream pressure |
Function | Reduces pressure | Maintains backpressure |
Opens when | Downstream pressure drops | Upstream pressure rises |
Closes when | Downstream pressure is satisfied | Upstream pressure drops |
Benefits
- Protects sensitive upstream equipment.
- Ensures stable operating conditions in pressure-critical areas.
- Helps balance flow and pressure across complex systems.