(a) Relief Valve for Air Compressor:
A relief valve suitable for use on the air side of a compressor is typically a pilot-operated pressure relief valve. Here’s a breakdown of its key features:
- Function: This valve automatically opens and releases compressed air when the pressure within the system exceeds a predetermined safe limit. This protects the compressor and downstream equipment from overpressure damage.
- Components:
- Main Valve: The main valve assembly directly regulates the flow of compressed air. It opens when the pressure overcomes a spring force or a combination of spring and pilot pressure.
- Pilot Valve: A smaller valve that senses the system pressure and controls the main valve indirectly. It often uses a diaphragm or piston to sense pressure.
- Spring: Provides a pre-set force that opposes the system pressure acting on the main valve.
- Adjustment Mechanism: Allows for setting the desired pressure relief level by adjusting the spring preload or pilot pressure.
- Operation: As the system pressure rises, it acts on the pilot valve. When the pressure reaches the set point, the pilot valve opens, relieving pressure from the top of the main valve piston or diaphragm. The system pressure then overcomes the spring force, pushing the main valve open and releasing compressed air until the pressure falls below the set point. The pilot valve then closes, and the spring reseats the main valve, stopping the flow of air.
(b) Resetting a Pilot-Operated Relief Valve After Overhaul:
After the valve is disassembled, cleaned, and inspected during an overhaul, resetting it for proper operation involves the following steps:
- Reassemble the Valve: Carefully reassemble the valve components according to the manufacturer’s instructions. Ensure proper alignment of parts and proper tightening of all connections.
- Adjust the Spring Preload (Optional): Some relief valves have an external adjustment mechanism for setting the spring preload, which determines the opening pressure. If the spring preload hasn’t been changed during disassembly, it might not require adjustment. Consult the manufacturer’s instructions for the specific valve model.
- Pilot Pressure Adjustment (Optional): In some pilot-operated valves, the pilot pressure can be adjusted to influence the opening pressure. This adjustment might be done using an external screw or by adjusting the pilot valve spring tension. Again, consult the manufacturer’s instructions for the specific model.
- Pressure Testing: With the valve reinstalled in the system, conduct a pressure test using an external pressure source. Gradually increase the pressure and observe the relief valve operation. It should open at the desired set pressure and close once the pressure falls below the setpoint. This ensures the valve functions correctly after the overhaul.
Important Note: The specific steps for resetting a relief valve can vary depending on the manufacturer and model. Always refer to the manufacturer’s instructions and service manuals for detailed procedures and safety precautions for your specific valve. It’s crucial to ensure the valve is set to the correct pressure relief level for safe operation of the compressed air system.