Minimum Pressure Valve (MPV) Replacement – 216169

Minimum Pressure Valve (MPV) – Rotary Screw Air Compressor

The Minimum Pressure Valve (MPV) is a critical component in oil-injected rotary screw compressors. It maintains the required minimum pressure within the air/oil separator tank during start-up, ensuring efficient oil circulation and proper lubrication of the compressor. Once the preset pressure is achieved, the valve opens to supply compressed air to the system. It also functions as a non-return valve, preventing reverse airflow after shutdown and enhancing overall compressor performance, efficiency, and equipment protection.

How Does an MPV Work?

1. Compressor Start-up
   • When the compressor starts, the MPV remains closed.
   • Pressure builds inside the separator tank.
2. Maintaining Minimum Pressure
   • The valve stays closed until the internal pressure reaches approximately 4–5 bar.
   • This pressure is necessary for proper oil circulation and lubrication.
3. Air Delivery
   • Once the required pressure is reached, the MPV opens automatically.
   • Compressed air flows to the plant air system.
4. Check Valve Function
   • When the compressor stops, the MPV prevents compressed air from flowing back into the compressor.
   • This protects the airend and prevents reverse rotation.

Main Functions

• Maintains minimum pressure inside the separator tank.
• Ensures proper oil circulation and lubrication.
• Prevents oil carryover during start-up.
• Acts as a non-return (check) valve.
• Improves compressor efficiency and reliability.
• Protects internal compressor components.

Signs of a Faulty MPV

• Compressor takes a long time to build pressure.
• Low discharge pressure.
• Excessive oil carryover into the air line.
• Air leaks after shutdown.
• Reverse airflow when the compressor stops.
• Poor lubrication during start-up.