we have Atlas copco make GX7 model screw compressor. When we started the air compressor, it working ok. Loading 6kg/cm2 & off loading 7.5kg/cm2.

If the working pressure reaches the maximum limit, the solenoid valve is de-energised venting the control air, the inlet valve closes completely & the unloading valve opens completely. The compressor will run fully unloaded.

If the compressor keeps running unloaded for uninterrupted period of 150 seconds, it will be stopped. The compressor will automatically restart when the net pressure drops to the minimum limit. We have problem of tripping at overload when automatically restart when the net pressure drops to the minimum limit.

Surendra Mahajan,
Nasik, India