RWB II ROTARY SCREW COMPRESSOR UNITS
MAINTENANCE
070.200-IOM (DEC 11)
Page 26
Maintenance
GENERAL INFORMATION
This section provides instructions for normal main tenance,
a recommended maintenance program, troubleshooting and
correction guides, and typical P and I diagrams. For typi‑
cal wiring diagrams and control panel information, consult
S90‑010 M for the QUANTUM panel.
THIS SECTION MUST BE READ AND
UN DER STOOD BEFORE ATTEMPT-
ING 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:
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 procedure
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. If oil cooler heads were removed, reinstall and
remove tags.
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, par ticularly
on new systems where welding slag or pipe scale could
finds it way to the compressor suction. Excessive dirt in the
suction 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 probable the most tolerant to in‑
gestion of some refrigerant liquid of any compressor type
available today, they are not liquid pumps. Make certain
to maintain adequate superheat and properly size suction
accumulators to avoid dumping liquid refrigerant into com‑
pressor 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 setting for long periods without run‑
ning it is advisable to evacuate to low pressure and charge
with dry nitrogen or oil, particularly 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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