RWF ROTARY SCREW COMPRESSOR UNITS
OPERATION
S70-600 IOM
Page 14
COMPRESSOR HYDRAULIC SYSTEM
The compressor hydraulic system moves the movable slide
valve (MSV) to load and unload the compressor. It also
moves the movable slide stop (MSS) to increase or de-
crease the compressor’s volume ratio (Vi).
The hydraulic cylinder located at the inlet end of the SGC
compressor serves a dual purpose. It is separated by a
fixed bulkhead into two sections. The movable slide valve
(MSV) section is to the left of the bulkhead and the movable
slide stop (MSS) to the right. Both sections are considered
double-acting hydraulic cylinders as oil pressure moves
the pistons in either direction.
Both sections are controlled by double-acting, four-way so-
lenoid valves which are actuated when a signal from the
appropriate microprocessor output energizes the solenoid
valve.
SINGLE-ACTING MODE - High Stage
Open valve at SC1
Close valve at SC2
Open valve at BP (bypass)
High stage compressor loading: The compressor loads
when MSV solenoid YY2 is energized and oil flows from the
unload side of the cylinder out port SC1, through valve
ports A and T to compressor suction. Simultaneously, dis-
charge pressure loads the slide valve.
High stage compressor unloading: The compressor un-
loads when MSV solenoid YY1 is energized and oil flows
from the oil manifold through valve ports P and A to cylinder
port SC1 and enters the unload side of the cylinder. Simul-
taneously, gas on the load side of the cylinder is vented
through port SC2 and valve BP to compressor suction.
NOTE: To control the rate of loading and unloading,
throttle the needle valve at SC1 port.
DOUBLE-ACTING MODE - Booster
Open valve at SC1
Open valve at SC2
Close valve at BP (bypass)
Booster Compressor Loading: The compressor loads
when MSV solenoid YY2 is energized and oil flows from the
oil manifold through valve ports P and B to cylinder port
SC2 and enters the load side of the cylinder. Simultaneously,
oil contained in the unload side of the cylinder flows out
cylinder port SC1 through valve ports A and T to compressor
suction.
Booster Compressor Unloading: The compressor unloads
when MSV solenoid YY1 is energized and oil flows from the
oil manifold through valve ports P and A to cylinder port
SC1 and enters the unload side of the cylinder.
Simultaneously, oil contained in the load side of the cylin-
der flows out of compressor port SC2 through valve ports B
and T to compressor suction.
NOTE: To control the rate of loading and unloading,
throttle valves SC1 and SC2.
NOTE: To slow all valve movements - loading, unloading,
and Vi change - throttle valve 2.
NEVER open valve BP and valve
SC2 at the same time during com-
pressor operation.
Figure 15
VOLUMIZER VOLUME RATIO CONTROL
Open valve at SC3
Open valve at SC4
Compressor Vi increase: The volume ratio Vi is increased
when MSS solenoid valve YY3 is energized and oil flows
from the oil manifold through valve ports P and A to com-
pressor port SC3, enters the increase side of the cylinder
and overcomes the decrease spring tension. Simulta-
neously, oil flows from SC4 port through valve ports B and T
to compressor suction.
Compressor Vi decrease: The volume ration Vi is de-
creased when MSS solenoid valve YY4 is energized and
oil flows from the oil manifold through valve ports P and B to
compressor port SC4, enters the decrease side of the cylin-
der. Simultaneously, oil flows form SC3 port through valve
ports A and T to compressor suction.
TO CONTROL THE RATE OF VI CHANGE, THROTTLE THE
NEEDLE VALVE AT SC3 PORT.
SC1
SC3
SEE HYDRAULIC
SCHEMATIC
FOR FUNCTIONAL
VIEW OF VALVE
OPERATION
Figure 16
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