HYDRAULIC SYSTEM 5540F/YB5515 SERVICE MANUAL
4-30 Published 10-21-2010, Control# 198-04
SWING CIRCUIT
General
The swing motor is controlled by a spool in the control valve
Figure 4-31. In the neutral position, oil is held in the circuit
and the motor is prevented from turning. The gear/pinion is
protected by a main relief valve set at 2400 psi (16 547 kPa)
in both swing directions.
Oil Flow
Swing Right
Pushing the handle spool OUT sends oil through motor port
B of the valve section to the swing motor. The motor rotates
clockwise and causes the mast to rotate to the right. Oil from
downstream side of the motor returns through the A port and
sent back to tank through the return filter.
Swing Left
Pulling the handle spool IN sends oil through motor port A of
the valve section to the swing motor. The motor rotates
counter clockwise and causes the mast to rotate to the left.
Oil from downstream side of the motor returns through the B
port and is sent back to the tank through the return filter.
ANTI-DOUBLE BLOCKING SYSTEM
General
The anti-double block circuit protects the hoist, telescope
and lift circuits from damage in the event that the hoist block
comes in contact with the boom head causing a double
blocking situation. The anti-double block system includes an
anti-double block mechanism Figure 4-32 at the end of the
boom head, a valve block with three normally closed
solenoids Figure 4-33, and a check valve in the main control
valve sections for lift, telescope and hoist functions.
FIGURE 4-31
a1629
Oil Flow - Swing Right
Reference Only
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