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HPS Rotary Screw Compressor Units
070.700-IOM (MAR 21)
Page 29
Maintenance
Maintenance
General information
This section provides instructions for normal main tenance,
a maintenance program, troubleshooting, and correction
guides, and P and I diagrams. For wiring diagrams and
information about the
Quantum™
HD
control panel, refer
to
090.040-M
.
Warning
This section must be read and un der stood before
attempting to perform any main tenance or service
to the unit.
Normal maintenance operations
When performing maintenance you must take several
precau tions to ensure your safety.
Warning
1. If unit is running, press [stop] key.
2. Disconnect power from unit before performing any
maintenance.
3. Wear appropriate safety equipment when com-
pressor unit is opened to atmosphere.
4. Ensure adequate ventilation.
5. Take necessary safety precautions required for the
refrigerant being used.
Warning
Close all compressor package isolation valves before
servicing the unit. Failure to do so may result in seri-
ous injury.
General maintenance
Correct maintenance is important in order to ensure long
and trouble-free service for your screw compressor unit.
The following points are some areas critical to good com
-
pressor operation:
•
Keep refrigerant and oil clean and dry, avoid mois
-
ture contamination. After servicing any portion of the
refrigera tion system, evacuate to remove moisture
before returning to service. Water vapor condensing
in the compressor while running, or more likely while
shut down, can cause rusting of critical components and
reduce life.
• Keep suction strainer clean. Check periodically, par-
ticularly on new systems where welding slag or pipe
scale could find its way to the compressor suction.
Excessive dirt in the suction strainer could cause it to
collapse, dumping particles into the compressor.
• Keep
oil filters clean. If filters show increasing pressure
drop, indicating dirt or water, stop the compressor and
change filters. Running a compressor for long periods
with high filter pressure drop can starve the compressor
for oil and lead to
premature bearing failure.
• Avoid
slugging compressor with liquid refrigerant. While
screw compressors are probably the most tolerant to
ingestion of some refrigerant liquid of any compressor
type available today, they are not liquid pumps. Make
certain to maintain adequate superheat and correctly
size
suction accumulators to avoid dumping liquid re
-
frigerant into compressor suction.
Keep liquid injection valves correctly adjusted and in
good condition to avoid flooding compressor with liquid.
Liquid can cause a reduction in compressor life and in
extreme cases can cause complete failure.
•
Protect the compressor during long periods of shut
down. If sitting for long periods without running, it is
advisable to evacuate the compressor to low pressure
and charge with dry nitrogen or oil. This is particularly
true on systems known to contain water vapor.
• Perform a preventive maintenance inspection any time
a compressor exhibits a noticeable change in vibra tion
level, noise, or performance.
Compressor shutdown and start-up
For seasonal or prolonged
shutdowns, perform the follow-
ing procedure:
1. Reduce the system pressure to the appropriate condi-
tion.
2. Press the
STOP
key to cease operation of the com-
pressor.
3. Open disconnect switches for the compressor motor
and oil pump starters.
4. Turn on the oil heater circuit breaker.
5.
Close the suction and discharge service valves, and the
liquid injection and economizer service valves if ap-
plicable.
Attach
CLOSED TAGS
.
6.
Shut off the cooling water or glycol supply valve to the
oil cooler, if applicable.
Attach
CLOSED TAG
.
7. Protect the oil cooler from ambient temperatures be-
low freezing or remove water heads.
To start up after a seasonal or prolonged shutdown,
per-
form the following procedure:
1. Restore and turn on any water necessary for the op-
eration of the system that may have been drained or
shut off.
2.
Open suction and discharge service valves, and liquid
injection and economizer service valves, if applicable.
Remove tags.
3. Close the disconnect switches for the compressor, mo-
tor, and oil pump starters.
4. Turn off the oil heater circuit breaker.
5. Perform checkpoints on prestart check list, then start
the unit.
General instructions for replacing
compressor unit components
Notice
See Publication
070.660-SM
for procedures covering
replacement motor and compressor mounting.