Manitowoc Published 05-16-17, Control # 233-03 1-55
999 SERVICE/MAINTENANCE MANUAL INTRODUCTION
The fluid exiting side “A” of load equalizing valve enters and
passes through control valve section of accessory system
valve and into check valve (8) that has a cracking pressure of
65 psi (4,5 bar).
Mast cylinders lower hydraulic solenoid HS-2 does not
enable when lowering the mast. Both cylinder ports are
interconnected with tank port while valve spool is in the
inactivated position. Both cylinder ports and tank port of
valve encounter a common 65 psi (4,5 bar) resistance.
Mast cylinder exhaust fluid returns to tank. Mast cylinder
exhaust fluid can also flow through check valve at 65 psi (4,5
bar) to replenish fluid on side “B” of the mast raising cylinders
during retraction of the rods. Hydraulic fluid through free flow
check valve sections on side “B” of counterbalance valves
and enters into rod end of the mast lowering cylinders.
To continue lowering mast, the gantry must be lowered.
When lowering gantry support cylinders to fully retracted
position, boom hoist hydraulic system is monitored by the PC
through boom hoist system pressure sender (12) and
controlled by the PC to maintain a minimum rope tension on
the boom hoist drum. The PC maintains this tension by
controlling boom hoist pump to create an average system
pressure of approximately 1100 psi (76 bar), while mast and
gantry lower with the gantry support cylinders.
FIGURE 1-39
HIGH
UPPERWORKS ACCESSORY MANIFOLD
REAR DRUM
PUMP DRIVE GEARBOX
HS-4
A
A
A
BB
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
BB
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
3
6
999CSM1-138
TO LOWERWORKS
ACCESSORY MANIFOLD
TO REAR HOIST MOTOR
LOOP FLUSHING VALVE
3
14
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