Aux 1 Unit 6 Q7

A relief valve fitted to the air side of a compressor, often referred to as a compressor discharge safety valve, is designed to protect the compressor and associated systems from overpressure conditions. Here’s a description of a suitable relief valve:

Type:

• Spring-Loaded Pressure Relief Valve: This is the most common type used for air compressor discharge. It operates automatically based on the pressure in the system, requiring no external power source.

Construction & Materials:

• Body and Internal Components:
  • Typically made of materials like cast iron, ductile iron, steel, or bronze, chosen for their strength and durability to withstand high pressures.
  • May have a stainless steel or other corrosion-resistant trim for improved resistance to moisture and contaminants in the compressed air.
• Spring:
  • A calibrated spring applies a force on the valve disc, keeping it closed under normal operating pressures.
• Seat and Disc:
  • The disc rests against a precisely machined seat to create a tight seal.
  • The disc lifts off the seat when the pressure exceeds the setpoint, allowing air to escape.

Operation:

1. Normal Operation (Below Set Pressure):
   • The spring force keeps the disc firmly seated against the valve seat, preventing any air flow through the valve.
2. Overpressure Condition:
   • Pressure Increase: If the pressure in the compressor discharge line rises above the valve’s set point, the force exerted by the compressed air overcomes the spring force.
   • Valve Opens: The disc lifts off the seat, creating an opening for the air to escape.
   • Pressure Relief: The excess air flows out of the valve, venting to the atmosphere or a designated safe location, thereby reducing the pressure in the system.
   • Valve Closure: Once the pressure drops below the set point, the spring force closes the disc back onto the seat, stopping the flow.

Key Features:

• Adjustable Set Point: The pressure at which the valve opens can be adjusted by changing the spring tension or using a different spring.
• Fast Response: The valve reacts quickly to pressure surges, opening rapidly to prevent damage.
• Full Lift: Many compressor discharge safety valves have a full lift design, meaning the disc lifts fully off the seat when open, maximizing flow capacity for efficient pressure relief.
• Corrosion Resistance: The valve materials and internal components are designed to resist corrosion from moisture and contaminants in the compressed air.

Placement:

• Compressor Discharge Line: Typically installed directly on the compressor’s discharge line, downstream of the aftercooler.

Importance:

• Protects Compressor and System: The relief valve prevents excessive pressure buildup in the compressor and connected piping, safeguarding the compressor, motor, air receivers, and other components from damage or failure.
• Ensures Safety: It prevents potential explosions or ruptures that could cause serious injuries or damage to the vessel.

Maintenance:

• Regular Testing: The relief valve should be periodically tested to ensure it operates correctly at the set pressure and has sufficient flow capacity.
• Cleaning and Inspection: The valve should be inspected and cleaned regularly to remove any debris or buildup that could affect its operation.

In summary, a spring-loaded pressure relief valve suitable for the air side of a compressor is a vital safety device. It protects the compressor and the entire compressed air system from the dangers of overpressure, ensuring safe and reliable operation.

Resetting a spring-loaded pressure relief valve after a manual overhaul involves adjusting its set pressure back to the desired value. The exact procedure can vary depending on the specific valve model, but here’s a general outline of the steps involved:

1. Reassemble the Valve:

• Complete Overhaul: After completing the overhaul, which typically involves disassembling the valve, cleaning or replacing components, and inspecting for wear or damage, carefully reassemble the valve according to the manufacturer’s instructions.
• Ensure Proper Sealing: Make sure all gaskets, O-rings, and other sealing elements are in place and properly installed to prevent leaks.

2. Adjust the Spring Tension:

• Access Adjustment Mechanism: Locate the adjusting mechanism, usually a screw or bolt on top of the valve bonnet. This mechanism controls the compression of the spring, which in turn determines the set pressure.
• Consult Manufacturer’s Instructions: Refer to the valve’s manual or datasheet for specific instructions on how to adjust the spring tension and the corresponding pressure settings.

3. Set the Desired Pressure:

• Use Calibration Equipment: Use a calibrated pressure gauge and a suitable pressure source (like a hand pump or a regulated air supply) to apply pressure to the valve inlet.
• Monitor Pressure and Valve Opening: Gradually increase the pressure while monitoring the gauge and observing the valve.
• Adjust Spring Tension: Adjust the spring tension until the valve opens (lifts) at the desired set pressure.

4. Verify and Lock:

• Repeat Test: Once the set pressure is achieved, release the pressure and repeat the test a few times to ensure the valve consistently opens and closes at the correct pressure.
• Lock Adjustment Mechanism: Once satisfied with the setting, secure the adjusting mechanism with a locknut or other locking device to prevent accidental changes.

Additional Considerations:

• Safety Precautions: Always follow safety procedures and wear appropriate PPE when working with pressurized systems.
• Qualified Personnel: Valve overhauls and adjustments should ideally be performed by qualified technicians or engineers with experience in handling such equipment.
• Record Keeping: Document the overhaul, adjustments, and test results in the maintenance log for future reference.
• Regular Testing: Even after an overhaul, the relief valve should be periodically tested as part of the compressor’s maintenance routine to ensure it continues to operate correctly.

By carefully following these steps and adhering to manufacturer’s recommendations, you can reset the relief valve to its proper set pressure after an overhaul, ensuring it continues to provide reliable overpressure protection for your compressed air system.