Cycle; Details - Carrier 17 Start Up & Operation Manual

HERMETIC MACHINES (19 SERIES)
LUBRICATION CYCLE
Summary —
The compressor oil pump and oil reservoir
are located in the compressor base. Oil is pumped through
an oil cooler and a filter to remove heat and any foreign par-
ticles. Part of the oil flow is directed to the compressor motor-
end bearings and seal. The remaining flow lubricates the
compressor transmission, thrust and journal bearings and seal.
Oil is then returned to the reservoir to complete the cycle
(Fig. 5).
Details —
Oil is charged into the reservoir (Item 1) through
a hand valve (Item 4) which also functions as an oil drain.
If there is refrigerant in the machine, a pump is required for
charging. Sight glasses (Item 10) on the reservoir wall per-
mit observation of the oil level. The normal operating oil
level is from the middle of the lower sight glass to the top
of the lower sight glass.
The motor-driven oil pump (Item 8) discharges oil to
an oil cooler (Item 12) at a rate and pressure controlled by
an oil regulator (Item 7). The differential pressure (supply
versus return) is registered at the control center. Oil differ-
ential pressure is maintained between 18 to 30 psi (124 to
207 kPa).
The oil pump discharges to the oil cooler and filter. On
EX compressors, the filter is located ahead of the oil cooler.
On FA compressors the oil cooler is located ahead of the
filter. The filter is capable of being valved closed to permit
removal of the filter without draining the entire oil system
(see Scheduled Maintenance, Changing Oil Filter section,
page 76 for details).
The oil cooler on the EX compressor is a plate-and-frame
type, refrigerant cooled, heat exchanger. The EX compres-
sor oil cooler heat exchanger uses refrigerant from the con-
denser as a coolant. The refrigerant cools the oil to a tem-
perature between 110 and 120 F (43 and 49 C) supply oil
temperature to the bearings.
The FA compressor oil cooler heat exchanger is water cooled.
The water flow through the cooler is manually controlled by
a plug valve. The valve should be adjusted to maintain ap-
proximately 145 F (63 C) in the oil sump during running
conditions.
As the oil leaves the oil cooler, it passes the oil pres-
sure transducer (Item 14) and then the thermostatic expan-
sion valve bulb (Item 13). The oil flow is then divided, and
a portion flows to the motor-end bearing (Item 19) and
seal. The remainder lubricates the compressor transmission
(Item 2) and the thrust and journal bearings (Item 3). Thrust
bearing temperature is indicated at the Local Interface De-
vice (LID). Oil from each circuit returns by gravity to the
reservoir.
A demister (Items 17 and 18), by centrifugal action, draws
refrigerant gas from the transmission area to the motor shell.
The resulting pressure difference prevents oil in the trans-
mission cavity from leaking into the motor shell.
Several safety features are part of the lubrication system:
In the event of power failure, a small oil reservoir
(Item 16) supplies sufficient oil reserve to ensure continued
lubrication until all compressor parts have come to a com-
plete stop. The bearing temperature sensor (Item 15) moni-
tors thrust bearing temperatures and shuts off the machine if
the temperature rises above a selected point. Low-oil pres-
sure will shut down the machine or prevent a start if oil pres-
sure is not adequate.
The PIC (Product Integrated Control) measures the tem-
perature of the oil in the sump and maintains the tempera-
ture during shutdown (see Controls, Oil Sump Temperature
Control section, page 38). This temperature is read on the
LID default screen.
During the machine start-up, the PIC will energize the oil
pump and provide 15 seconds of prelubrication to the bear-
ings after the oil pressure is verified and before the controls
start the compressor. During shutdown, the oil pump will
run for 60 seconds after the compressor actually shuts down
for the purpose of post-lubrication. The oil pump can also be
energized for testing purposes in controls 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 any
refrigerant in the oil to flash. The resulting oil foam cannot
be pumped efficiently; oil pressure falls off, and lubrication
is poor. If oil pressure falls below 15 psi (90 kPa) differen-
tial, the PIC will shut down the compressor.
Oil reclaim is accomplished by returning the system oil
through the check valve/orifice (Item 11). As oil builds up
behind the second stage impeller, it is drained by the check
valve/orifice back into the oil reservoir. An oil/refrigerant mix-
ture is drawn up from the operating level of the cooler into
the guide vane housing. This assists the oil return system at
low load operating conditions.
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