Operating instructions

14
2.3.5 - Lubrication cycle
2.3.5.1 - Summary
The oil pump, oil filter, and oil cooler make up a package
located partially in the transmission casting of the compres-
sor-motor assembly. The oil is pumped into a filter assembly
to remove foreign particles and is then forced into an oil
cooler heat exchanger where the oil is cooled to proper
operational temperatures. After the oil cooler, part of the
flow is directed to the gears and the high speed shaft bearings;
the remaining flow is directed to the motor shaft bearings.
Oil drains into the transmission oil sump to complete the
cycle (see Fig. 4 - “Lubrication system”).
2.3.5.2 - Details
Oil is charged into the lubrication system through a hand
valve. Two sight glasses in the oil reservoir permit oil level
observation. Normal oil level is between the middle of the
upper sight glass and the top of the lower sight glass when
the compressor is shut down. The oil level should be visible
in at least one of the 2 sight glasses during operation.
Oil sump temperature is displayed on the ICVC default
screen. Oil sump temperature ranges during compressor
operation between 52 to 66°C. The oil pump suction is fed
from the oil reservoir. An oil pressure relief valve maintains
124 to 172 kPa differential pressure in the system at the
pump discharge. This differential pressure can be read
directly from the ICVC default screen.
The oil pump discharges oil to the oil filter assembly. This
filter can be closed to permit removal of the filter without
draining the entire oil system. The oil is then piped to the
oil cooler. This heat exchanger uses refrigerant from the
condenser as the coolant. The refrigerant cools the oil to a
temperature between 49°C and 60°C.
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1. Rear motor bearing
2. Forward motor bearing
3. Labyrinth gas line
4. Oil supply to forward high speed bearing
5. Isolation valve
6. Filter
7. Sight glass
8. Isolation valve
9. Check valve
10. Filter
11. Eductor
12. Oil heater
13. Oil pump
14. Oil motor
15. Oil cooler
16. Isolation valve
17. Pressure transducer
18. TXV bulb
19. Motor cooling line
As the oil leaves the oil cooler, it passes the oil pressure
transducer and the thermal bulb for the refrigerant expan-
sion valve on the oil cooler. The oil is then divided, with a
portion flowing to the thrust bearing, forward pinion bearing,
and gear spray. The balance then lubricates the motor shaft
bearings and the rear pinion bearing. The oil temperature
is measured as the oil leaves the thrust and forward journal
bearings within the bearing housing. The oil then drains into
the oil reservoir at the base of the compressor. The PIC
(Product Integrated Control) measures the temperature of
the oil in the sump and maintains the temperature during
shut-down. This temperature is read on the ICVC default
screen.
During the chiller start-up, the PIC will energize the oil pump
and provide 15 seconds of prelubrication to the bearings
after pressure is verified before starting the compressor.
During shut down, the oil pump will run for 60 seconds to
post-lubricate after the compressor shuts down. The oil
pump can also be energized for testing purposes in the
Control Test.
Ramp loading can slow the rate of guide vane opening to
minimize oil foaming at start-up. If the guide vanes open
quickly, the sudden drop in suction pressure can cause the
expansion/vaporisation of the refrigerant in the oil. The
resulting oil foam cannot be pumped efficiently; therefore,
oil pressure falls off and lubrication is poor. If oil pressure
falls below 103 kPa differential, the PIC will shut down the
compressor.