directional control valve in the same valve bank, it may be required to partially close or feather the valves that are located
in the bank first, in regards to flow from the pump, in order to provide sufficient flow to the valves located last in the bank.
The closed spool directional control valve functions basically the same way as the open spool directional control valve in
that the through passage of the valve must be blocked off by the valves spool to divert flow to the dead end parallel
passage. With flow diverted to the parallel passage, pressure then must unseat the load check valve to allow the flow to
reach the open work port. The load check valve is provided to prevent back sliding of components which support heavy
loads as is evidence by the circuits this valve is used in. Return flow from the component is through the return work port to
the reservoir return passage.
Integrated Outrigger Valve
The integrated outrigger valve is mounted near the center of the carrier frame in front of the front axle and is used for the
control of the outrigger circuit. The valve consists of five subassemblies; two solenoid valves, an inlet section, an outlet
section, and a working section.
The solenoid valves are normally closed. They are used to control a pilot pressure that positions the spool within the
working section. When the solenoid valves are de-energized, the springs maintain the spool in a centered position
permitting oil to flow to the pressure beyond circuit.
The inlet section contains two inlet ports and a pressure gauge port. It also contains an adjustable main relief valve set at
2500 psi (17,238 kPa/172.38 bar). This relief valve is an adjustable pilot operated type valve and relieves back to the
reservoir through the exhaust (EX) port.
The working section is the open center type and contains a spring centered spool which allows oil to flow through the
center to the pressure beyond circuit when the spool is centered. Work port A is cylinder spooled, or the oil is trapped in
the function while the spool is in neutral. Work port B is open to the reservoir (when the spool is in neutral) due to the fact
that there are two flats ground into the end land of the spool. These flats act as an orifice preventing the complete
blockage of oil in this circuit. This prevents an unwanted pressure buildup in this circuit when the spool is in neutral. The
flats are so small that when the circuit is being energized, the oil passing by these flats is negligible compared to the total
volume of oil. The working section also contains two nonadjustable relief valves and a check valve. The port A relief valve
is set at 300 to 400 psi (2069 to 2758 kPa/20.69 to 27.58 bar). The port B relief valve has full flow capability and is set to
relieve at 2000 psi (13.791 kPa/137.91 bar). The check valve in the bottom of the working section, prevents a reverse flow
of oil if the oil pressure in the working circuit is greater than the supply pressure.