Friday, November 14, 2008

shut down procedure of screw compressor

When unit is to be taken off the stream and shutdown, the following procedure should be followed:
1. Gradually open bypass to reduce discharge pressure to ½ normal pressure. Operate unit at this condition for approx. 20 minutes or until the gas discharge temperature levels off.
2. Stop unit. If unit starts turning backwards, immediately close the block valve.
3. Allow lube oil to circulate for 10 minutes after the unit is stopped to properly cool the rotors.
4. If unit is to be shutdown for an extended period in a freezing environment, drain all water from oil coolers, compressor jackets and piping.
5. If unit is shutdown for an extended period of time, following maintenance program should be followed to keep unit ready for service:

Open compressor inlet casing drains to allow condensate to drain out Circulate lube oil for a minimum of one hour once a week and rotate unit several revolutions.For extended down periods, remove silencers and piping from compressor inlet and discharge and spray a light film of lubricating oil on rotor surfaces and machines internal housing surfaces once every two weeks to prevent rusting If the unit shuts down instantly under full load (power failure, emergency shutdown), following procedure is to be followed if unit is to be started:

1. Let the cooling water flow through the oil cooler and compressor
2. Circulate the lube oil for one hour and rotate the compressor drive shaft ¾ turn by hand every 10 minutes
3. Turn until over by hand three revolutions. The unit is ready to restart when it turns normal with no tight areas.
4. Restart unit in normal manner. Operate at approx. ½ normal pressure for 15 min before applying rated pressure

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