Operating and Maintenance Manual 09/2019 – part I
Screw compressors
34
The oil level should be checked when the compressor is switched off and
pressure has dropped to ambient pressure.
8.3.6. Water condensate draining
The presence of water condensate in oil has a significantly unfavourable effect on the
operating safety and life of the screw compressor.
Warranty claims shall be excluded if excessive wear or damage of the
bearings caused by water contained in oil is found. The condensate is
formed when the screw compressor is operated in short runs only, i.e. below
the temperature at which the thermostat in the oil circuit is activated. The
condensate comes from the humid atmospheric air sucked into the screw
block. When the compressor is stopped and cooled down, the moisture
contained in the air inside the compressor pneumatic system condenses.
The condensate should be drained from the cold screw compressor e.g.
before starting work. Proceed the same way as when draining oil.
Maintenance procedure:
− Stop the compressor and close the pressure conduit valve.
− Switch off the power supply and take measures to prevent it from being unintentionally
switched on again by unauthorised persons.
− Verify that the machine has been de-energised (0 V).
− Wait minimum 5 minutes and then open the compressor housing.
− Check that the system has been emptied by slowly unscrewing the oil filler cap (use
protective clothing) (Fig.10). The compressed air can be hot.
− Position an appropriate oil catch container under the oil drain plug and carefully unscrew
the oil drain plug.
− Drain the condensate from the body (oil tank) as long as oil appears, and then replace
the oil drain plug.
− Replenish the oil through the fill port in the compressor body (or oil tank) to the
maximum level, and then tightly screw the oil fill plug by hand.
− Start the screw compressor and let it run for about 3 minutes.
− Check the oil level: replenish the missing oil quantity up to the maximum level.
− Dispose the condensate in accordance with the applicable regulations.
8.3.7. Oil change and recommendations concerning oil
Oil change can only be done when the screw compressor is stopped and completely
unloaded. The machine should be heated up to the operating temperature (oil temperature
should be approx. 60°C to 80°C).
Maintenance procedure:
- Stop the compressor and close the pressure conduit valve.
- Switch off the power supply and take measures to prevent it from being unintentionally
switched on again by unauthorised persons.
- Verify that the machine has been de-energised (0 V).
- Wait minimum 5 minutes and then open the compressor cover.
The waste oil must be changed after previous machine heating, which ensures its fast and
accurate draining into the catch container.
- Check that the system has been emptied by slowly unscrewing the oil filler cap (use
protective clothing) (Fig.10). The compressed air can be hot.
- Position an appropriate oil catch container under the oil drain plug and carefully unscrew
the oil drain plug.
- Drain the oil completely and then replace the oil drain plug.
- Pour new oil through the fill port to the maximum level and then tightly screw the oil fill plug
by hand.
- Start the screw compressor and let it run for about 3 minutes.
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