HYDRAULIC SYSTEM GRT8100 SERVICE MANUAL
2-42
Published 3/26/2018, Control # 596-05
MAIN DIRECTIONAL CONTROL MANIFOLD
VALVE
Description
The lift, telescope, and hoist directional valves (Figure 2-19
through Figure 2-21) located on the superstructure side plate
(Figure 2-18) are three-position normally closed proportional
valves. The lift, telescope, and hoist directional valves are
each controlled by two two-position solenoid controlled
proportional valves, which vary pilot supply circuit pressure
to each directional control valve based on operator inputs
through the electric joysticks in the operator’s cab.
The two-position solenoid controlled proportional valves
controlling the lift down, telescope out, and hoist up functions
act as RCL lockout valves and are de-energized, regardless
of joystick position, when the rated capacity limiter (RCL)
detects an overload condition.
A load sense relief valve in the main directional control
manifold valve limits the high pressure setting of the No. 1
and No. 2 pumps to 276 bar (4000 psi).
Maintenance
Main Directional Control Manifold Valve Removal
1. Tag and disconnect the hydraulic lines from the valve.
Cap or plug the lines and ports.
2. Tag and disconnect electrical connectors from the valve.
3. Remove the capscrews, flatwashers, and lockwashers
securing the valve. Remove the valve.
Main Directional Control Manifold Valve Installation
1. Install the valve on the turntable upright and secure with
the capscrews, flatwashers, and lockwashers. Torque
capscrews. Refer to Fasteners and Torque Values, page
1-15 for proper torque value.
2. Connect the electrical connectors to the valve as tagged
during removal.
3. Connect the hydraulic lines to the valves as tagged
during removal.
Functional Check
1. Start the engine and run it at normal speed.
2. Operate the joysticks of the valve bank(s). Check for
smooth operation of cylinders and motors.
3. Check the valve bank(s) and lines for leakage. Make
repairs as needed.
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