The stack valve is located on the right side of the valve
panel assembly. It consists of 13 separate valves.
Three valves control hydraulic flow to and from the stack
valve. Eight valves control screed extension cylinders
and hopper lift cylinders. Two valves are not used. The
stack valve operates at a maximum pressure of 2500 psi
(17 237 kPa). Hydraulic oil for the stack valve is supplied
by the right auxiliary hydraulic pump. Each valve in the
stack valve is controlled by a 12 volt DC electric coil.
Three valves control oil flow to the hydraulic stack valve
The power-beyond valve is a two-way valve
that switches hydraulic oil flow from the track tensioning
cylinders to the stack valve. It is normally open. When a
cylinder function is being controlled through the stack
valve, the power-beyond valve closes, turning off oil flow
to the track tensioning cylinders. When the stack valve
controlled cylinders are not operating, a coil spring opens
the power-beyond valve, turning on the oil flow to the
track tensioning cylinders. The - V power-beyond valve
has a nominal flow of 2.5 gallons (9,4 l) per minute.
Maximum internal leakage is 5.0 cubic inches (81,9 ml)