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Advice for stopping and re-starting air compressors, dryers and gas generators

I need more assistance

If you need to reduce production and switch off your air compressors temporarily, we have put together some stopping and re-starting guidelines for you to follow.

How to stop for periods of time due to factory closure or shutdown

Atlas Copco service engineer walking away from service van towards compressed air installation

If the machines are to be stopped for a prolonged period of time the following rules should be applied:

  • General recommendation: if production is stopped completely, manually stop the compressor, even if they are integrated in a central controller. If this is not done, it’s possible that the machine will run at minimal capacity to compensate for small leaks in your compressed air network. This may be harmful (for example, it will create condensate in GA machines).
  • VSD compressors: Carry out a program stop, make sure the electrical power supply is left turned on to keep the capacitor bank charged and ready for restart.
  • Water-cooled air compressors: After stopping be sure to isolate the water supply.  This will stop condensate forming inside the compressor element(s).  Don’t forget to turn it back on at start up. Please make sure any air blast cooling systems are turned off.
  • Atlas Copco Z compressors: these need the main drive shaft to be manually rotated via the motor drive coupling, 3 complete rotations, once a week. This is to prevent the low pressure and high pressure compression stages from seizing up during a long period of down time. If the Z Compressor is a VSD version, don’t forget to turn the power supply back on after turning the compressor over by hand, to protect the inverter drive capacitors.
  • Centrifugal / ZH compressors – should be programmed stopped, leave the power supply on.  They need to have the auxiliary oil pump turned on once a week for 10 minutes whilst the compressor is stopped. This will maintain the oil temperature and periodically start up the auxiliary oil pump to circulate warm oil around the bearings during long periods of downtime.
  • Dryers (adsorption or refrigerant) and gas generators can be stopped manually and depressurized if required. For gas generators, when depressurizing you should monitor the oxygen level in the machine room.

Starting up after long periods of shutdown

Before turning equipment back into operation, a visual inspection is needed. 

apropriate compressor switch on procedure
First turn off the power supply to the air compressor, remove the drive shaft protection guard and turn the drive coupling to check that the compressor is free to turn. If the compressor turns freely, re fit the guard and turn on the power supply to the compressor; turn on the cooling water if the compressor is water cooled. Slowly open the compressor air discharge valve until the air pressure equalizes between the compressor and the air net. Start the compressor. The compressor is now back online. If the air compressor is connected to a sequence controller, make sure the compressors are integrated onto the controller/ Optimizer.

For adsorption dryers and gas generators never start up against an empty air-net. When starting close the outlet valve behind the dryer or generator and pressurize the system. Then slowly open the outlet valve to pressurize the air-net, this to avoid high air speeds damaging the adsorption material.

Please contact your local Atlas Copco customer center in order to assist you in taking your equipment out of operation and back into operation as they do have all the in-house experience in keeping your compressor room in optimal health.