18
• Controls - Instruments which control the brine temperature,
protect the various elements of the machine, and automati-
cally start and stop the compressor. When specified, addi-
tional controls for automatic operation of interconnecting
equipment such as fans and pumps are furnished.
• Drive - Prime mover which supplies the power to drive the
compressor.
• A refrigerant pumpout and storage unit is usually furnished
with this equipment. The refrigeration cycle covers the first
three major components; the others are described in other
portions of this manual.
Refrigeration Cycle — See Fig. 8. In the cooler, heat is
transferred from water flowing thru the tubes to cold refriger-
ant around the tubes. The cooler refrigerant temperature corre-
sponds to cooler pressure as listed in Tables 6A and 6B. Heat
extracted from the water evaporates the liquid refrigerant, re-
leasing large volumes of refrigerant gas which pass into the
compressor.
Eliminators in the top of the cooler prevent any liquid re-
frigerant from being carried over into the compressor.
The compressor impeller raises the gas from cooler pressure
up to condenser pressure. Gas flow into the compressor is con-
trolled by adjusting the suction inlet guide vanes and the vari-
able diffuser width. This controls cooler pressure and, there-
fore, machine capacity.
In the condenser, heat is transferred from the high-pressure
refrigerant gas to water flowing through the tubes. The gas con-
denses on the tubes and the liquid drains in to the condenser
subcooler section. A subcooler level control keeps the subcool-
er tubes covered with refrigerant and provides an effective liq-
uid seal, preventing refrigerant gas flow from high-pressure to
low-pressure side of the machine.
Since the coldest condenser water flows through the sub-
cooler tubes, the temperature of the refrigerant is reduced as
much as possible before it enters the cooler.
When the refrigerant clears the refrigerant flow valve and is
once again at cooler pressure, the refrigeration cycle is com-
plete.
Oil Cycle — See Fig. 9. External, positive displacement oil
pump (Item 9) mounted on reservoir (Item 11) discharges to
cooler (Item 7) and filter (Item 6). Auxiliary oil pump (Item 10)
is provided to maintain continuous lubrication during
emergencies.
Supply oil temperature is read on thermometer (Item 5) lo-
cated in line between cooler and filter. Oil temperature is con-
trolled by regulating water flow to the cooler. Differential pres-
sure regulator (Item 8) maintains seal and seal end journal
bearing (Item 15) oil pressure at 35 psid (241 kPa) above back-
of-seal refrigerant pressure. Seal oil low pressure cutout (Item
1) shuts down compressor if seal oil pressure drops below cut-
out pressure. Seal end journal bearing temperature is read on
thermometer (Item 14).
Pressure regulating valve (Item 4) regulates oil supply pres-
sure to thrust bearing and seal-end journal bearing (Item 15).
Bearing oil pressure is read on bearing oil supply pressure gage
(optional). Thrust bearing oil low-pressure cutout safety func-
tion shuts down compressor if bearing oil pressure drops below
cutout pressure.
Oil from the seal and bearings returns by gravity flow thru a
common drain line to the oil reservoir. Oil leakage thru the seal
to the refrigerant side drains to a separation tank (Item 13)
where absorbed refrigerant is driven from the oil by a small
heater.
The refrigerant gas is vented to the compressor suction. The
oil is returned to the reservoir thru a float valve (Item 12) which
controls the oil level in the separation tank.
Fig. 8 — Refrigeration Cycle
a17-575
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