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P a g e
Needle valves
Needle valves in the pumping station adjust the hydraulic flow to the
cylinders.
There are four: one for each telescoping spray bar extension/retraction
cylinder, one for both cylinders that lock the front spray bar housing, and
one for the cylinders that tilt the front spray bar housing.
Note:
The needle valves are set at the factory and likely will not
need adjustment
.
Pneumatic system
The pneumatic system includes an air compressor (Figure 20), which is
powered by a hydraulic motor. This system also includes the solenoid
valves, which control the various valves.
Some models have an auxiliary connection at the compressor for a
compressed air supply.
Air compressor
The air compressor is located on the paver or screed deck. It provides
compressed air to the solenoid valves and ultimately to the pneumatic
valves that control many of the spray paver functions.
When there is low pressure, a switch on the air compressor triggers a
relay to open the hydraulic valve for the air compressor's hydraulic
motor. The low pressure switch also sends a signal to the control unit and
in turn to the display screen unit as a warning (delayed 45 seconds on
startup).
Another pressure switch triggers the relay to close the valve when the
high pressure is reached. The compressor cycles between 85 psi and 125
psi.
