Manitowoc 2250 Service Maintenance Manual

Reference Only
Manitowoc Published 07-19-16, Control # 249-01 1-41
2250 SERVICE/MAINTENANCE MANUAL INTRODUCTION
1
Boom Hoist/Luffing Jib System Operation
General
See Figure 1-24, Figure 1-25, and Figure 1-26 for the
following.
The boom hoist system and luffing jib system (optional)
share the same pump. Only one system can be operated at a
time. In Standard mode, the boom hoist (drum 4) is
controlled with the control handle on the left side console and
the luffing jib is inoperable. In Luffing Jib mode, the boom
hoist is inoperable while the luffing jib hoist (drum 5) is
controlled with the control handle on the left side console.
Each motor drives a gearbox on the end of a drum shaft.
Hydraulic pilot pressure from the boom hoist charge pump
operates the boom hoist and the luffing jib motor servos. A
pressure sender in the high-pressure side of each system
provides pressure information to the programmable
controller (PC). A fixed orifice between motor ports A and B
allows for smoother drum operation.
When the boom hoist or luffing jib drum rotates, a speed
sensor on the end of the boom hoist drum shaft or luffing jib
drum flange sends an input voltage to the PC. The PC sends
a variable 0 to 12 V output to the rotation indicator in the
control handle. As the drum rotates faster, the rotation
indicator on the control handle pulsates to indicate the
drum’s rotational speed. The speed is shown on the display.
Continuous changing of system fluid occurs through leakage
in the pump, motor, and external sequence/flow valve. The
sequence/flow valve opens at 19 bar (275 psi) and removes
15 L/min (4 gpm) of hot fluid from the system by dumping it
into the motor case where the fluid returns to the tank.
Brake and Pawl
Hydraulic pilot pressure from the boom hoist charge pump
operates the boom hoist or luffing jib brake. Air pressure
operates the boom hoist or luffing jib drum pawl.
When a brake switch is in the ON position, boom hoist brake
solenoid valve HS-6 or luffing jib brake solenoid valve HS-19
is disabled to apply the brake to the drum. Boom hoist pawl-
in air solenoid valve AS-14 or luffing jib pawl-in air solenoid
valve AS-16 is enabled to keep the pawl applied to the drum
flange. The boom hoist/luffing jib pump does not stroke in
response to the control handle’s movement.
When a brake switch is in the OFF position, the boom hoist
or luffing jib brake remains applied, waiting for a control
handle command. The PC sends a 0 V output to disable
boom hoist pawl-in air solenoid AS-14 or luffing jib pawl-in air
solenoid AS-16. The PC sends a 12 V output to enable boom
hoist pawl-out air solenoid AS-13 or luffing jib pawl-out air
solenoid AS-15. The solenoid valve shifts to exhaust the air
pressure from the piston end of the pawl cylinder and to
supply manifold air pressure to the rod end of the cylinder.
The cylinder retracts the pawl out of the drum flange.
Raising the Boom Hoist/Luffing Jib
The following description is for the boom hoist system. The
luffing jib system is similar.
When the left side console control handle is moved back for
booming/luffing up, an input voltage of 5 V or more is sent to
the PC. The PC sends a variable minus 0 to 2.8 V output that
is applied to the pump’s electrical displacement control
(EDC). The PC sends a variable 0 to 2.19 V output that is
applied to the boom hoist motor’s pressure-control pilot
(PCP). The PC checks that the system’s limit switches are
closed and that a system fault is not present.
The pump’s EDC tilts the swashplate in the UP direction to
satisfy pressure memory. The PC compares drum-holding
pressure to pressure memory. When the system pressure is
high enough, the PC sends a 12 V output to enable the brake
solenoid valve HS-6. The brake solenoid shifts to block the
drain port and opens the port to pilot pressure from the boom
hoist charge pump to release the selected drum brake.
The pump’s EDC continues to tilt the swashplate up as
hydraulic fluid flows from the pump outlet port to the motor
inlet port. Return fluid is from the motor outlet port to the
pump inlet port.
The PC’s output voltage to the pump’s EDC and the motor’s
PCP is relative to the control handle’s movement. As the
boom hoist control handle moves back, the pump’s
swashplate angle increases. When system pressure
exceeds the pressure-compensating override (PCOR) valve
setting of 340 bar (4,930 psi), the valve shifts to direct the
flow from the shuttle valve to the maximum displacement
side of the servo cylinder. The PCOR valve overrides the
command from the servo PC valve, increasing the motor’s
displacement, output torque, and reducing output speed.
When the PCOR valve closes, the control of the motor
returns to the servo PC valve.
The PC is continuously balancing the system’s pressure and
the motor’s displacement angle so the motor displacement
goes to minimum when the control handle is fully back, if the
motor torque is not too high. The PC monitors the motor’s
displacement and controls the motor speed by regulating the
hydraulic fluid flow through the pump.
When the boom hoist control handle is moved toward the
neutral position, the PC compensates for hydraulic system
leakage or changing engine speed. The PC sends a 0 V
output to the boom hoist pump’s EDC that moves the
swashplate to the center position. This shifts the motor back
to maximum displacement for slower output speed to slow
the drum’s rotation. The PC stores the load-holding pressure
in pressure memory. After the control handle center switch
opens, the PC sends a 0 V output to disable the boom hoist
brake solenoid valve HS-6. The drum brake solenoid valve
shifts to block pilot pressure to the brake and opens a line to
the tank. The brake applies before the drum pump de-
strokes.

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English