Pilot pressure control valves are a type of pressure relief valves that use a small valve, called a pilot valve, to control the opening and closing of a larger valve, called a main valve. The main valve is usually connected to a high-pressure or high-flow fluid system that needs to be protected from overpressure events. The pilot valve is connected to a low-pressure or low-flow control feed that senses the pressure in the system and regulates the pressure in the dome, which is the volume above the piston or disc of the main valve. When the system pressure reaches a set value, the pilot valve opens and releases the pressure from the dome, allowing the main valve to open and relieve the excess pressure from the system. When the system pressure drops below the set value, the pilot valve closes and restores the pressure in the dome, causing the main valve to close and resume normal operation.
The main advantage of pilot pressure control valves is that they can provide large shifting forces without the impact or wear that a manually operated valve would experience. They can also handle higher pressures and flows than conventional spring-loaded valves, and offer more precise and stable pressure control. Pilot pressure control valves can be used in various applications, such as:
- Hydraulic systems, where they can control the pressure and flow of hydraulic fluids to pumps, cylinders, motors, and other components.
- Steam systems, where they can prevent steam pressure from exceeding the design limits of boilers, turbines, and piping.
- Gas systems, where they can regulate the pressure and flow of natural gas, propane, or other gases to burners, compressors, and engines.
- Water systems, where they can control the pressure and flow of water to sprinklers, faucets, and other devices.
The following table summarizes some of the common types of pilot pressure control valves and their functions:
| Type | Function |
|---|---|
| Pilot-operated relief valve | Opens when the system pressure exceeds the set pressure and closes when the system pressure drops below the set pressure. |
| Pilot-operated reducing valve | Reduces the system pressure to a lower, constant pressure and maintains it regardless of the upstream pressure variations. |
| Pilot-operated unloading valve | Unloads the system pressure to a low, standby pressure when there is no demand for flow and restores the system pressure when there is a demand for flow. |
| Pilot-operated sequence valve | Opens when the system pressure reaches a set pressure and allows the flow to a secondary circuit. |
| Pilot-operated counterbalance valve | Balances the load pressure and prevents it from running away in a vertical or overrunning load application. |