TM 5-3895-373-20
After the hydraulic oil exits the stack valve, the pressure
is reduced by a 900 psi (6200 kPa) relief valve. The
excess hydraulic oil is sent to the return manifold and
back to the hydraulic reservoir. The reduced pressure
fluid is passed through a check valve.
The 900 psi (6200 kPa) hydraulic oil charges a hydraulic
accumulator and maintains pressure to the track
tensioning cylinders. When one or both tracks encounter
an obstacle, the track tensioning cylinder is compressed,
sending pressure pulsation’s into the track tensioning
system. The pressure pulsation causes the check valve
in the inlet of the track tensioning system to seat. This
prevents the pressure pulsation from traveling to the rest
of the hydraulic system. If the pulsation is small, it will be
absorbed by the hydraulic accumulator. Larger pulses,
which increase system pressure beyond 1800 psi (12
400 kPa), cause a relief valve to lift and vent excess
pressure to the return manifold.
1.21.
ELECTRICALLY CONTROLLED HYDRAULIC
CIRCUITS.
The paving machine uses electrically controlled hydraulic
circuits for all hydraulic functions. Hydraulic pressure is
supplied by two auxiliary pumps and an auxiliary vibration
pump.
Hydraulic functions controlled from the operator switch
panel are:
1) Screed lift
2) Auger/conveyor drive
3) Extension screed positioning
4) Screed vibrator drive
5) Hopper wing lift
Hydraulic functions controlled from the screed control
panels are:
1) Auger/conveyor drive
2) Tow point lift
3) Extension screed positioning
Auxiliary pumps and auxiliary vibration pump draw
hydraulic oil from a common hydraulic reservoir. Pump
output is routed through 50/50 flow dividers, pressure
relief valves and flow control and solenoid valves. The
flow control and solenoid valves control the speed of
hydraulic cylinders and motors. Hydraulic oil return is
routed to the return manifold. From the return manifold,
the oil is forced through a hydraulic oil cooler and a
return filter before returning to the hydraulic reservoir.
Each individual function is explained in the following
paragraphs.
1-41
