RWF ROTARY SCREW COMPRESSOR UNITS
MAINTENANCE
S70-600 IOM
Page 18
GENERAL INFORMATION
This section provides instructions for normal maintenance,
a recommended maintenance program, troubleshooting and
correction guides, and typical P and I diagrams. For typical
wiring diagrams and information about the
Quantum
con-
trol panel, consult publication S90-010 M.
THIS SECTION MUST BE READ
AND UNDERSTOOD BEFORE AT-
TEMPTING TO PERFORM ANY
MAINTENANCE OR SERVICE TO THE UNIT.
NORMAL MAINTENANCE OPERATIONS
When performing maintenance you must take several
precautions to ensure your safety:
1. IF UNIT IS RUNNING, PRESS [STOP] KEY.
2. DISCONNECT POWER FROM UNIT BEFORE PER-
FORMING ANY MAINTENANCE.
3. WEAR PROPER SAFETY EQUIPMENT WHEN COM-
PRESSOR UNIT IS OPENED TO ATMOSPHERE.
4. ENSURE ADEQUATE VENTILATION.
5. TAKE NECESSARY SAFETY PRECAUTIONS RE-
QUIRED FOR THE REFRIGERANT BEING USED.
CLOSE ALL COMPRESSOR PACK-
AGE ISOLATION VALVES PRIOR TO
SERVICING THE UNIT. FAILURE TO
DO SO MAY RESULT IN SERIOUS INJURY.
COMPRESSOR SHUTDOWN and START-UP
For seasonal or prolonged shutdowns the following proce-
dure should be followed:
1. Reduce the system pressure to the desired condition.
2. Press [STOP] key to cease operation of the compressor.
3. Open disconnect switches for compressor motor and oil
pump starters.
4. Turn on oil heater circuit breaker.
5. Close suction and discharge service valves, also liquid
injection and economizer service valves, if applicable. At-
tach CLOSED TAGS.
6. Shut off cooling water supply valve to oil cooler, if appli-
cable. Attach CLOSED TAG.
7. Protect oil cooler from ambient temperatures below freez-
ing or remove water heads.
To start-up after a seasonal or prolonged shutdown the fol-
lowing procedure should be followed:
1. Any water necessary for the operation of the system that
may have been drained or shut off should be restored and
turned on.
2. Open suction and discharge service valves, also liquid
injection and economizer service valves, if applicable. Re-
move tags.
3. Close disconnect switches for compressor, motor and oil
pump starters.
4. Turn off oil heater circuit breaker.
5. Perform checkpoints on prestart check list, then start unit.
GENERAL MAINTENANCE
Proper maintenance is important in order to assure long
and trouble-free service from your screw compressor unit.
Some areas critical to good compressor operation are:
1. Keep refrigerant and oil clean and dry, avoid moisture
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.
2. Keep suction strainer clean. Check periodically, particularly
on new systems where welding slag or pipe scale could find
its way to the compressor suction. Excessive dirt in the suc-
tion strainer could cause it to collapse, dumping particles
into the compressor.
3. 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.
4. Avoid slugging compressor with liquid refrigerant. While
screw compressors are probably the most tolerant to inges-
tion of some refrigerant liquid of any compressor type avail-
able today, they are not liquid pumps. Make certain to main-
tain adequate superheat and properly size suction accumu-
lators to avoid dumping liquid refrigerant into compressor
suction.
Keep liquid injection valves properly 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.
5. Protect the compressor during long periods of shut down.
If the compressor will be sitting for long periods without run-
ning it is advisable to evacuate to low pressure and charge
with dry nitrogen or oil. This is particularly true on systems
known to contain water vapor.
6. Preventive maintenance inspection is recommended any
time a compressor exhibits a noticeable change in vibra-
tion level, noise or performance.
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