Atlas Copco GA 160 VSD Instruction Book page 88

Procedure
1. Run the compressor until warm. Stop the compressor, close the air outlet valve and switch off the voltage.
Wait a few minutes and depressurize by unscrewing the vent plug on top of the air receiver to permit any
pressure in the system to escape. Wait until all the pressure in the system is released.
2. Drain the oil by removing the drain plug of the flexible fixed to the bottom of the air receiver.
Draining the oil cooler on air-cooled compressors:
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Instruction book
APF192090