Manitowoc MLC650, Service Maintenance Manual

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Reference
Only
HOISTS MLC650 SERVICE/MAINTENANCE MANUAL
5-26
Published 09-09-16, Control # 229-09
DRUM 4 BOOM HOIST OR MAST HOIST
(VPC-MAX™)
Drum 4 Brake Overview
A brake is attached to the drum motors, with the brake discs
attached to the drum shaft. The brakes are controlled by
joystick movement and the drum park brake switch.The
brakes are applied by spring force and released by hydraulic
pressure.
The brakes must be fully released to allow the drum to rotate
for hoisting and lowering. To accomplish this, the brake
pressure must be above 12 bar (175 psi). Any pressure
below this could cause the brakes to remain partially applied,
which could damage the drum brake system.
If brake hydraulic pressure or electrical control is lost, the
brake is applied by spring force.
Hydraulic flow to the drum 4 brake release solenoid valve is
provided by the main and charge pressure hydraulic flow
from pump 5.
Drum 4 Brake Operation
See Figure 5-14 and Figure 5-16 .
The J2 joystick sends a 24 V
DC
output to the drum 4 park
switch. The drum park switch is closed in the UN-PARK
position, causing the switch to send a 24 V
DC
signal back to
the J2 joystick. The J2 joystick communicates the un-park
brake command to the IOLC32 control module via the
controller area network bus (CAN Bus).
When the IOLC32 control module receives the un-park
command from the J2 joystick, IOLC32 control module
sends a 24 V
DC
output to the drum brake release solenoid
valve, energizing the solenoid. The solenoid valve shifts
position, routing hydraulic fluid from the pump 5 to the drum
brake piston, releasing the brake.
When the drum brake switch is moved to the ON-PARK
position, the drum park switch is open, sending a 0 V
DC
signal back to the J2 joystick. The J2 joystick communicates
the on-park brake command to the IOLC32 control module
via the CAN Bus.
When the IOLC32 control module receives the on-park
command from the J2 joystick, the IOLC32 control module
sends a 0 V
DC
output voltage to the drum brake release
solenoid valve, de-energizing the solenoid. This causes the
solenoid valve to return to the default position, allowing the
fluid in the brake piston to flow through the drum brake
release solenoid valve, and back to the tank. The reduced
hydraulic pressure allows spring force to apply the drum
brake.
Drum 4 Motor Loop Flushing
See Figure 5-14 and Figure 5-16 .
Loop flushing of the drum 4 right and left hydraulic motors (6
and 15) occurs whenever pressure on the lowering side of
the circuit is above 13,8 bar (200 psi). The charge pressure
check valve (8) only allows flow from the charge pump to the
lowering side of the circuit if the charge pressure is 0,35 bar
(5 psi) or higher than the lowering side of the circuit.
CAUTION
Possible Machine Damage!
When raising or lowering a load, do not use the drum park
switch to stop the load movement, since this could cause
damage to the boom. Use the joystick for a controlled
smooth stop.