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Operation
The compressor is equipped with a
safety switch to stop the compressor if
the temperature of the oil leaving the
thrust bearing exceeds 185°F.
1. Check the temperature of the oil leaving the thrust
bearing; it should not exceed 185°F. (The main oil
supply temperature should be 100 - 140°F.)
The rise for thrust oil outlet above sup-
ply oil temperature will be 10°F to
45°F, depending upon speed and load.
A. A temperature differential of less than 10°F may
indicate a worn volute seal between the main
oil pump discharge and thrust bearing.
B. A temperature differential above 45°F may in-
dicate excessive load or insufficient oil circula-
tion, which may be due to a plugged oil filter
(refer to Replacing Oil Filter Element).
2. Check the temperature of the oil supply to the bear-
ings; it should not exceed 140°F.
A. A higher temperature indicates inadequate oil
cooling. Check the oil cooler water supply
and clean the water sides of the oil cooler, if
necessary.
B. Do not throttle the oil cooler. Oil cooling inhib-
its oil foaming. An exception is when a turbine
is being operated at it's "idle" speed.
Oil supply pressure at the filter outlet
will vary with speed – 30 to 260 psi
above suction pressure from low to
high speed respectively. This variation
in pressure is tailored to meet bear-
ing requirements at different speeds.
Oil pressure will be reduced slightly
as the vanes are closed or as the oil
temperature is increased. The oil pres-
sure will fall if the filter becomes
clogged with dirt and sludge.
3. If oil pressure falls, the oil filter element must be
changed before the oil pressure differential falls to
26
80% of its normal value, (refer to Replacing Oil
Filter Element).
Compressors on which the oil reser-
voir pressure can fall below atmo-
spheric should be equipped with a
shaft seal oil pressure gauge and regu-
lating valve.
4. Adjust the regulating valve to maintain a seal pres-
sure of 2 to 5 psi at minimum suction pressure. The
actual seal oil pressure will vary with suction pres-
sure and the pre-rotation vane position; closing the
vanes reduces seal pressure.
5. The shaft seal will drip a slight amount of oil to the
atmospheric trap built into the side of the compres-
sor housing. Normally, this leakage is very slight
and this oil should be discarded. (Refer to Atmo-
spheric Shaft Seal in this section.)
6. The compressor is equipped with a pressure gauge
to measure balance piston pressure. This pressure
depends upon the stage to which the balance piston
is vented (refer to Balance Piston) and varies with
compressor suction and discharge conditions. Over
a period of time, increasing balance piston pressure
could be an indication of balance piston seal wear.
Increasing balance piston pressure results in in-
creased thrust load to the thrust bearing.
7. Check the upper sight glass for the reservoir oil
level. The oil level is normal when it is visible in the
upper sight glass. If the oil level becomes visible in
the lower glass, add oil. If the sight glass is a reflex
type the oil level should be above minimum or at
normal. Especially before attempting to start the
compressor.
Maximum compressor discharge tem-
perature must not exceed 300°F for
aluminum impeller wheels; 600°F for
steel impellers. Based on metallurgi-
cal limitations, there may be other fac-
tors that further limit maximum dis-
charge temperature. All compressors
are equipped with a safety switch to
stop the compressor if the discharge
temperature exceeds its limit, which
is speed dependent (refer to the appli-
cation data sheet).
FORM 220.11-NM2 (602)
YORK INTERNATIONAL
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