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Reference
Only
Manitowoc
Published 05-16-17, Control # 233-03
1-53
999 SERVICE/MAINTENANCE MANUAL
INTRODUCTION
1
Load equalizing valve ensures mast-raising cylinders
operate in unison, protecting mast from structural damage
caused by twisting. Load equalizing valve also provides
support resistance against mast to ensure control of the unit
while rotating it 120° at time of assembly.
Exhaust fluid from side “B” sections of both counterbalance
valves combines, and the free flow check valve section on
side “B” of load equalizing valve blocks the flow. The fluid
then passes through valve flow restrain section preset at
4,000 psi (275 bar).
Load equalizing valve operates with a 1.5:1 pilot ratio of the
relief valve pressure, permitting valve to open when the
hydraulic pressure (from the setup pump) on side “A” of the
load-equalizing valve is approximately 2,670 psi (185 bar).
Restraining section on side “B” of load equalizing valve
opens, controlling flow of fluid out of the cylinders and
ensuring cylinder operation is balanced.
The fluid then passes through non-restrictive portion of flow
control valve and enters accessory system valve. Hydraulic
fluid exits the accessory system valve through control valve
section before returning to tank.
When mast raises over 90°, and starts to move away from
mast assist arms, the PC sends an output signal to de-stroke
rear drum pump. The PC also sends an output signal to shift
mast extend cylinder solenoid HS-1 back to center position.
Mast Cylinders Lower
See Figures
To lower mast in Crane Setup mode, move boom hoist
handle (1) all the way back. Handle neutral switch closes,
sending an input voltage of 5 volts or more to 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 tilts boom hoist pump swashplate to stroke pump in
the raise direction. As mast lowers, boom hoist drum hauls in
wire rope. The mast cylinders provide supportive resistance
against mast while lowering to down position.
When lowering mast with computer programming, the mast
cylinders retract solenoid HS-2 is enabled. Gravitational
force from mast weight and boom hoist line pull helps retract
the mast cylinder rods.
Summary of Contents for 999
Page 1: ...R e f e r e n c e O n l y Service Maintenance Manual Manitowoc 999 ...
Page 2: ...R e f e r e n c e O n l y ...
Page 4: ...R e f e r e n c e O n l y THE ORIGINAL LANGUAGE OF THIS PUBLICATION IS ENGLISH ...
Page 297: ...R e f e r e n c e O n l y ...
Page 298: ...R e f e r e n c e O n l y ...