070.750-IOM2 (JUN 22)
Page 21
HPS 273 and 407 Rotary Screw Compressor
Maintenance
Maintenance
• Keep oil lters clean. If lters show increasing pressure
drop, indicating dirt or water, stop the compressor and
change lters. Running a compressor for long periods
with high lter pressure drop may starve the compres-
sor of oil and lead to premature bearing failure. Use
dual oil lters so that the lters can be changed with-
out shutting down the package.
• Avoid slugging the compressor with liquids such as
refrigerant or oil. While screw compressors are prob-
ably the most tolerant of any compressor type avail-
able today of the ingestion of some liquid, they are not
liquid pumps. Make certain to use a correctly-sized
suction accumulator in order to avoid dumping liquid
into compressor suction.
• Protect the compressor during long periods of shut-
down. If the compressor sits for long periods without
running, evacuate to low pressure and charge with dry
nitrogen or oil. It is also necessary to rotate the shaft
monthly to keep the seal faces lubricated. This is par-
ticularly true on systems known to contain water vapor.
• Preventive maintenance is best practice, which includes
measuring vibration and performing oil analyses. In-
spect the compressor any time it exhibits a noticeable
change in vibration level, noise, or performance.
Changing oil
Warning
Do not mix oils of different brands, manufacturers, or
types. Mixing of oils may cause excessive oil foaming,
nuisance oil level cutouts, oil pressure loss, gas or oil
leakage and catastrophic compressor failure.
Shut down the unit when changing oil. At the same time,
change all oil lter cartridges and remove and clean all oil
strainer elements.
1. Stop the compressor unit.
2. Lock out the motor starter.
3. Close the suction and discharge service valves.
4. Using appropriate equipment, lower the compressor
pressure to 0 bar (0 psig).
5. Open the drain valve, or valves, and drain oil into a
suitable container.
6. Drain the oil lter, or lters, and the oil coolers.
7. Remove the old lter cartridges and install new ones.
8. Remove, clean, and reinstall elements in the strainers.
9. Evacuate the unit.
10. Open the suction service valve and pressurize the unit
to system suction pressure. Close the suction valve and
leak test.
11. Add oil.
12. Open the suction and discharge service valves.
13. Remove the lockout from the motor starter.
14. Start the unit.
Note: Allow time for oil to cool before opening the drain
plugs.
General information
This section provides instructions for normal maintenance,
a maintenance program, and troubleshooting and correc-
tion guides.
Warning
This section must be read and understood before
attempting to perform any maintenance or service to
the unit.
WARNING
Compressor surfaces, especially those on the dis-
charge housing, may become hot during operation.
Additionally, surfaces near the suction ange may
be cold. Contact with compressor surfaces dur-
ing or soon after operation may cause burns. If it is
likely that anyone may touch the compressor during
operation and the conditions are such that burns
may occur, the packager must implement protection
measures. For compressors that must comply with
the Machinery Directive, refer to the requirements of
EN ISO 13732-1.
WARNING
Opening any part of the compressor unit to atmo-
sphere while under pressure may cause injury. Ensure
that the compressor pressure is at 0 psig before
removing any pressure containing part.
General maintenance
When performing maintenance, you must take several
precautions to ensure your safety:
• If the unit is running, press the STOP key.
• Stop the motor and lock out starter before performing
any maintenance.
• Wear appropriate safety equipment when the compres-
sor unit is opened to the atmosphere.
• Ensure there is adequate ventilation.
• Take the necessary safety precautions required for the
gas being used.
Correct maintenance is important to ensure long and trouble-
free service from your screw compressor. Some factors criti-
cal to ensure good compressor operation are as follows:
• Keep oil clean and dry, and avoid moisture contamina-
tion. After servicing any portion of the refrigeration
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
breakdown of the oil and refrigerant, which can gener-
ate corrosive agents. This can lead to the breaking down
of bearings and other vital components in a short time.
• Keep the suction strainer clean. Check periodically,
particularly on new systems where welding slag or
pipe scale may nd its way to the compressor suction.
Excessive dirt in the suction strainer may cause it to
collapse, dumping particles into the compressor.
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