Manitowoc 999, Service And Maintenance Manual

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Reference
Only
INTRODUCTION 999 SERVICE/MAINTENANCE MANUAL
1-52
Published 05-16-17, Control # 233-03
Mast Cylinders Raise
See Figures 1-36 and 1-37
Place boom hoist brake switch (9) in off - park position. Boom
hoist brake remains spring-applied to boom hoist drum until
the PC releases the brake. Boom hoist drum pawl out
solenoid HS-15 is enabled to disengage pawl from boom
hoist drum. Boom control handle circuit to the PC remains
open.
After gantry support cylinders are fully extended, move boom
hoist handle all the way forward to extend mast cylinders and
push the mast upward. Handle neutral switch closes,
sending an input voltage of 5 volts or less to the PC.
The PC sends a positive output signal brake release
solenoid HS-13. Brake release solenoid valve shifts, to block
tank port and open port from low-pressure side of closed-
loop to boom hoist brake cylinder spring, releasing brake.
The PC sends a negative output signal to enable boom hoist
pump EDC that tilts pump swashplate to stroke pump in the
lower direction.
When boom hoist brake is released, an input signal is sent to
PC. The PC sends a negative output voltage to rear drum
pump EDC (13) that tilts rear drum pump swashplate to
stroke pump in the low-pressure side direction. Low-
pressure side hydraulic fluid flows to mast extend cylinder
solenoid HS-1 of accessory valve and through free flow
check valve sections on side “A” of load equalizing valve (8).
From equalizing valve, fluid enters counterbalance valves (7)
and piston end of mast raising cylinders (6), extending
cylinder rods to raise the mast assembly. As mast raises
boom hoist drum pays out wire rope between gantry and
mast sheaves. The PC monitors rear drum pressure senders
to control mast cylinder raising speed rate.
Fluid from rod end of mast raising cylinders is blocked by
free flow check valve sections on side “B” of counterbalance
valves and flows through valve flow restrain sections preset
for a relief pressure of 3,500 psi (240 bar). Counterbalance
valves operate with a 5:1 pilot ratio of the relief valve
pressure, permitting valve to open when pressure in piston
end of the cylinders is approximately 700 psi (48 bar).
FIGURE 1-37
HIGH
UPPERWORKS ACCESSORY MANIFOLD
REAR DRUM
PUMP DRIVE GEARBOX
HS
-4
A
A
A
B B
B
BOOM HINGE
PIN
CYLINDER
LOAD EQUALIZING
VALVE
4,000 PSI (275 BAR)
MAST RAISING CYLINDERS
3,500 PSI (240 BAR)
LOW
HS-
3
HS
-2
HS-
1
HS
-6
HS-
5
3 7
A
A
A
B B
B
LOAD EQUALIZING
VALVE
4,000 PSI (275 BAR)
GANTRY CYLINDERS
3,500 PSI (240 BAR)
HIGH
FRONT DRUM
PUMP DRIVE GEARBOX
LOW
LOW PRESSURE
ACCESSORIES
3
8
3 6
TO LOWERWORKS
ACCESSORY MANIFOLD
3 6
999CSM1-136
TO REAR HOIST MOTOR
LOOP FLUSHING VALVE
3
14