Manitowoc Published 05-09-17, Control # 014-28 1-51
16000 SERVICE/MAINTENANCE MANUAL INTRODUCTION
mast raising cylinders solenoid HS-51 in retract (mast
lowering) direction. The valve shifts to block tank port and
open port to low-pressure side of pump.
As mast lowers to transport position, boom/mast drum hauls
in wire rope between boom and mast sheaves.
From the accessory valve, the fluid pressure enters free-flow
check valve sections on side B of load equalizing valve.
From equalizing valve, fluid enters counterbalance valves
and rod end of mast cylinders, retracting cylinder rods.
Fluid flow from piston end of mast raising cylinders is
blocked by free-flow check valve sections on side A of
counterbalance valves and flows through valve flow restrain
sections preset for a relief pressure of 3,480 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 cylinders is approximately 700 psi (48 bar).
Hydraulic fluid from side A sections of both counterbalance
valves combines, and the free-flow check valve section on
side A of load equalizing valve blocks the flow. The fluid then
passes through the valve flow restrain section that is preset
at 4,000 psi (276 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 on side A of the load-
equalizing valve is approximately 2,680 (185 bar).
Restraining section on side B of load equalizing valve opens,
controlling flow of fluid out of the cylinders to ensure cylinder
operation is balanced.
When mast cylinders are retracting, Node-3 controller
monitors boom/mast hoist drum speed sensor. Node-1
controller maintains a speed that is proportional to accessory
system hydraulic pressure applied to the mast raising
cylinders.
Node-3 controller output voltage to pump EDC is relative to
control handle movement. The system pump varies flow to
keep drum at handle command setting. As control handle is
moved back, an output voltage increases the pump
swashplate angle.
Node-3 controller monitors the mast angle sensor when
mast is moving. When mast is near 0°, Node-3 controller
sends a zero output voltage to pump EDC that moves
swashplate to center position. After control handle center
switch opens, Node-4 controller also sends a zero output
voltage to disable drum brake solenoid HS-10 to apply brake
before pump de-strokes.
Node-4 controller sends a zero output voltage to shift spool
of mast raising cylinder HS-51 to center position. Node-3
controller sends a zero volt output to disable accessory
system proportional relief solenoid HS-68.
NOTE: It may be necessary to use the mast cylinders
switch to lower mast fully.
FIGURE 1-48
Pressure
Sender
Accessory
Pump
Mast Raising
Cylinders
HS-68
HS-51
HS-50
Pressure
Sender
Drum 4
Pump
Drum 4
Motors
HS-10
16-1038
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