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

If the compressors 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 compressors, 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 programme 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 left turned on electrically whilst the compressor is shut down. 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 depressurised if required. For gas generators when depressurising monitor the oxygen level in the machine room.