GROVE 4-13
CD3340B/YB4411 HYDRAULIC SYSTEM
Published 04/07/2015 Control # 569-00
Port No. 7
Hydraulic oil under low pressure flows through this port from
the hoist motor drain.
Troubleshooting
Leakage between the passages of the hydraulic swivel will
cause loss of power or possible wrong operation of one of
the circuits. It is important to know the arrangement of the
passages in the hydraulic swivel. Remember that the oil will
always follow the path of least resistance.
LIFT CIRCUIT
Use the hydraulic schematic in Section 12 along with the
following text to understand how the lift circuit functions.
General
The lift hydraulic circuit includes two lift cylinders, two holding
valves, Ports 3 and 4 in the hydraulic swivel, an anti-double
block cutout solenoid valve, a valve section of the four-spool
control valve (Figure 4-4), and the hydraulic lines.
Oil Flow
When the valve spool is in the neutral position, both A and B
ports are closed and oil is held in the circuit to prevent
movement of the lift cylinders.
Raising the Booms
Pulling the joystick towards the operator connects the pump
passage A in the control valve. Oil leaves Port B of the
control valve section and passes through Port 4 of the
hydraulic swivel and enters the base end of the lift cylinders
through the holding valves. In this direction, the oil flows
freely through the holding valves and into the base end of the
cylinder. The cylinder rod starts to extend, pushing oil ahead
of the piston out the rod end port. The oil returns through Port
3 of the hydraulic swivel to Port A of the control valve section.
From here, the oil is routed to the tank passage of the control
valve assembly and returns through the return filter to the
hydraulic oil tank.
The anti-double block valve will shut off the oil supply to the
cylinders in the event the hook block comes in contact with
the boom head. In this case, the operator must let out more
rope on the hoist before the boom can be raised.
Lowering the Booms
Pushing the joystick away from the operator sends oil in the
opposite direction and causes the cylinder to retract. The
holding valve lets the cylinder retract only if there is oil under
pressure available to the rod port of the cylinder. See Holding
Valve.
FIGURE 4-3
Hydraulic Swivel Port Arrangement, Typical
Reference Only
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