Service manual

24 – 2
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 2.0
Section 24 • Twin Screw Control
Operation
Once the twin screw is confi gured, its operation is
very similar as the single screw and all options that
are available for single screw confi guration are also
available for twin screw. The only operational differ-
ence is the manual mode of operation. Twin screw
compressors can experience leaky slide seals that can
cause the capacity slide to drift after it has been po-
sitioned by the controller. To counteract the capacity
slide drift problem, the twin screw manual mode op-
eration has an added anti-drift feature that automati-
cally maintains the position of the hydraulic actuator.
Slide Calibration - Capacity Slide Valve
Potentiometer
This section provides critical information and control
parameters related to the capacity slide actuator. The
“% cap” display shows the actual value in percent of the
capacity slide without any conditioning that might be
applied to the other capacity position displays. In addi-
tion, this section displays the value of the actuator sig-
nals in millivolts in the “input Value” display box, see
Figure 24-2.
“-” Button:
• When the operator presses and holds this button, the
output associated with capacity slide decrease sole-
noid is energized and the oil pump is energized. The
oil pump is needed to force oil into the capacity slide
chamber to move the capacity slide.
“+” Button:
• When the operator presses and holds this button, the
output associated with capacity slide increase sole-
noid is energized and the oil pump is energized. The
oil pump is needed to force oil into the capacity slide
chamber to move the capacity slide.
Software limit setpoint:
• The Vission 20/20 uses the “Min Limit” and “Max
Figure 24-2. Slide Calibration - Twin Screw Control