RWB II ROTARY SCREW COMPRESSOR UNITS
OPERATION
S70-200 IOM
Page 20
COMPRESSOR OIL COOLING SYSTEMS
The RWB II unit can be equipped with one of several sys tems
for controlling the compressor oil tempera ture. They are single
or dual-port liquid injection, or thermo syphon and water-
cooled oil coolers. Each system is autom ati cally con trolled,
independent of compressor loading or unloading.
Oil cooling systems should maintain oil temperature within
the following ranges for R-717 and R-22:
Liquid
Injection
External*
Oil Cooling
Oil Cooling
130 - 170°F
120 - 160°F
* Thermosyphon oil cooling (TSOC) or Water-cooled oil
cool ing (WCOC).
SINGLE-PORT LIQUID INJECTION
The single-port liquid injection system is desig ned to per mit
liquid refrigerant injection into one port on the com pres sor
at any given moment and operates as outlined.
Solenoid valve SV5 is energized by the micro processor
when the temperature sensor, in stalled in the oil manifold,
ex ceeds the LICO set point. High pressure liquid refriger ant
is then supplied to the tempera ture control valve (TCV). The
tem per a ture control valve is equal ized to a constant back
pres sure by the dif feren tial pressure control valve (PDCV).
The differential pressure control valve uses dis charge gas
to maintain downstream pressure. The gas downstream of
the differential pressure control valve is bled off to the com-
pres sor suction to ensure steady and constant opera tion of
the valve.
RWB II BOOSTER OR SWING DUTY
APPLICATION
Discharge gas from the high stage compressor is required
to assist the differen tial pressure control valve (PDCV) in
pro vid ing the temperature control valve (TCV) with a con stant
back pressure.
A solenoid valve SV6 is installed before the differential
pres sure control valve (PDCV) to prevent migration of high
pres sure gas during shutdown. A Frick-installed timer limits
the high pressure gas to only thirty seconds duration, since
in ter me di ate gas pressure and spring tension are suffi cient to
maintain closure on unit shutdown. A metering valve is also
provided for use as a service valve and to allow discharge
gas fl ow regulation to prevent excessive force and resulting
closure “hammering”.
A fi eld-installed 1/4 inch OD tubing connection is required
between the high stage compressor discharge piping line (or
receiver) and the check valve.
DUAL-PORT LIQUID INJECTION
The dual-port liquid injection system is design ed to obtain
the most effi cient compressor performance at high and low
compression ratios by permitting injection of liquid refriger ant
into one of two ports optimally located on the com pressor.
This minimizes the performance penalty incurred with liquid
injection oil cooling.
The dual-port system contains all the com ponents of the
sin gle-port system with the addition of a double acting so-
le noid valve SV7 and operates as outlined.
Solenoid valve SV5 is energized by the micro processor when
the temperature sensor, in stalled in the oil manifold, ex ceeds
the LICO set point. Liquid refrigerant is then passed through
the tempera ture control valve (TCV) to the doub le-acting so-
lenoid valve SV7. Depending on the compressor’s op er at ing
volume ratio (Vi), the micropro cessor will select the fl ow of
the liquid refrigerant to either com pressor port SL-1 or SL-2,
whichever is more effi cient.
When the compressor operates BELOW 3.5 Vi, compres sor
port SL-1 supplies the liquid cool ing. When the (Vi) ris es
ABOVE 3.5 Vi, port SL-2 supplies the liquid cooling.
The temperature control valve is equalized to a constant back
pressure by the differential pres sure control valve (PDCV).
Both the differential pressure control valve (PDCV) and
the double-acting solenoid valve SV7 use discharge gas to
main tain downstream pressure. The gas downstream of both
valves is bled off to the compres sor suction to ensure steady
and constant operation of the valves.
LIQUID INJECTION ADJUSTMENT
PROCEDURE
Adjustments must be made to ensure the oil is at the proper
temperature. When the adjustments have been made cor-
rectly, the oil temperature, the discharge temperature and
the temperature of the oil in the separator should all be ap-
proximately the same. (Refer to P&I Diagram)
Carefully insert The bulb from the thermal expansion valve
( TXV ) into the well in the discharge pipe between the com-
pressor and the oil separator. Then open the valve to the oil
separator high pressure connection.
Next, open the refrigerant supply valve, remove the cap on
the pressure regulating valve (PCV ), and close the adjust-
ing valve.
For low temperature oil – 125° to 135°F
After the unit has been started, wait for the oil temperature to
reach 122°F. This is the preprogrammed temperature to open
the liquid feed solenoid in the liquid injection supply line.
Open the adjusting valve only until the needle on the gauge
begins to move a very small amount.
Next, adjust the pressure regulating valve to approximately
80 psig by turning the adjustment ring inside the top of the
valve with a 5/16" Allen wrench. Turn the wrench clockwise
to raise the oil temperature, and counterclockwise to lower
the oil temperature.
After the adjustment s been, made wait until the oil and
discharge temperatures have had a chance to stabilize
before readjusting. The end result should be between 135°
and 140°F.
For high temperature oil – 160° to 170°F
After the unit has been started, wait for the oil temperature to
reach 122°F. This is the preprogrammed temperature to open
the liquid feed solenoid in the liquid injection supply line.
Open the adjusting valve only until the needle on the gauge
begins to move a very small amount.
