
Reference
Only
INTRODUCTION
18000 SERIVCE/MAINTENANCE MANUAL
1-50
Published 12-05-17, Control # 035-23
MAIN HOIST 2 SYSTEM
Main Hoist 2 System Components
See Figures
The main hoist 2 system and the main hoist 1 system are
similar and operate the same. See Main Hoist 1 System in
this manual for main hoist 1 information.
Main hoist 2 drum is located in boom butt. Two main hoist 2
pumps drive two drum motors on each end of drive shaft that
is connected to a gearbox. Hydraulic connections between
main hoist 2 pumps and motors form a closed-loop system
that is controlled with control handle movement and node
controllers. The center load drum control handle on the right
side console operates the main hoist 2 in all drum mode.
Main hoist 2 control handle is inoperable when drum 2 park
brake is applied.
Main hoist pump 2/5 is dedicated to operate mast hoist
(Drum 5) motor. See Mast Hoist System in this manual for
mast hoist information.
Hydraulic charge pressure from left travel charge pump
supplies hydraulic pilot pressure to operate both main hoist 2
motor servos. Hydraulic charge pressure from system
charge pumps supplies hydraulic make-up fluid to low-
pressure side of each main hoist 2 motor. A pressure sender
in high-pressure side of each pump leg provides system
pressure information to node-1 controller. There are
equalizing lines between legs A and legs B when two pumps
drive two motors. A fixed orifice between pump ports A and B
allows for smoother drum operation.
When drum motors rotate, a speed sensor at one motor rotor
monitors and sends an input voltage to node-1 controller.
Node-2 controller sends an output voltage to rotation
indicator in control handle. As drum rotates faster, the
rotation indicator on top of control handle pulsates with a
varying frequency that indicates drum rotational speed. The
handle command in percent from neutral is displayed on
Drum 2 screen in operator’s cab.
Continuous changing of closed-loop fluid occurs with
leakage in pump, motor, and external sequence/flow valve.
Sequence/flow valve opens at 200 psi (14 bar) and removes
4 gallons per minute (15 l/m) of hot fluid from system by
dumping fluid into motor case where the fluid returns to tank.
Main Hoist 2 Drum Brake
Hydraulic pressure to operate main hoist 2 drum brakes is
from low-pressure side of drum 2/5.
When selected main hoist drum brake switch is in on - park
position, drum brake solenoid valve HS-10 (Drum 2) is
disabled so brakes are applied to each side of drum shaft.
Drum pump does not stroke in response to control handle
movement.
When selected main hoist drum brake switch is placed in off -
park position, brake solenoid valve HS-10 (Drum 2) remains
applied. Brakes remain applied until node-6 controller sends
a 24 volt output to release the brake. The drum circuit is
active, waiting for a control handle command.
Main Hoist 2 Raising
The following drum raising operation is for main hoist 2
(Drum 2) while operating in Standard mode.
When main hoist 2 control handle is moved back for
raising,
an input voltage of 2.4 volts or less is sent to node-1
controller. Node-3 controller sends a variable zero to 24 volt
output that is divided by a resistor and applied to each pump
EDC in the hoist direction. Node-6 controller sends a
variable zero to 24 volt output that is divided by a resistor and
applied to both motor PCP’s. Node-1 controller checks that
drum block-up limit switches are closed and no system faults
are present.
Pump EDC’s tilt swashplate in the
up
direction to satisfy
pressure memory. Node-1 controller compares drum holding
pressure to value in pressure memory. When system
pressure is high enough, node-6 controller sends a 24 volt
output to enable drum brake solenoid valve HS-10. Drum
brake solenoid shifts to block drain port and opens port to
low-pressure side of drum system to release brakes from
both sides of drum shaft.
Each pump EDC tilts swashplate in the up direction as
hydraulic fluid flow is from port A of pump 2 and port B of
pump 2/5 to port A of left side motor and port B of right side
motor. Return fluid is from motor ports A and B to return port
B of pump 2 and port A of pump 2/5.
Node controller output voltages to each pump EDC and each
motor PCP is relative to control handle movement. The
system pumps operate a slave and master with one pump
operating continuously and the other pump varying to keep
drum at handle command setting. As control handle is
moved back, an output voltage increases the pumps
swashplate angles. When system pressure exceeds the
PCOR (Pressure Compensating Over-Ride) valve setting of
4,930 psi (340 bar), the valve shifts to direct flow from shuttle
valve into maximum displacement side of servo cylinder. The
PCOR valve over-rides the command from servo PC valve,
increasing motor displacement and output torque and
reducing output speed. When PCOR valve closes, control of
the motor returns to servo PC valve.
Node controllers are continuously balancing drum system
pressures and the motor displacement angle so the motor
displacement goes to minimum when control handle is all the
way back, if the motor torque requirement is not too high.
Node-1 controller monitors motor displacement and controls
motor speed by regulating the hydraulic fluid flow through the
pump.
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