Manitowoc 2250 Service Maintenance Manual

Reference Only
Manitowoc Published 07-19-16, Control # 249-01 1-81
2250 SERVICE/MAINTENANCE MANUAL INTRODUCTION
1
Counterweight Jack Cylinders
See Figure 1-51 and Figure 1-52 for the following procedure.
There are four counterweight jacks—one front left jack, one
front right jack, and two rear center jacks. The counterweight
trailer jack system is used to raise the wheels off the ground
to move the steering arms to the desired steering position.
The jacks allow the counterweight trailer to stand by itself
when not attached to the crane and to aid in tire
maintenance. Axle wedges help stabilize the counterweight
trailer when it is not attached to the crane and when the jacks
are retracted.
Each jack cylinder has a counterbalance valve at each
cylinder port. These valves allow smooth operation when
using the jack cylinders. The counterbalance valves lock the
cylinders in position if there is a problem with the system.
The counterbalance valves also provide relief protection for
the cylinders.
With the engine running, power is available to the MAX-ER’s
remote switch assembly when the power cable (W28) is
plugged into the receptacle on the left side of the
counterweight trailer. When the power button on the MAX-
ER’s remote switch assembly is pressed, power is enabled
to operate the counterweight jack switches. The four
switches are spring-returned to the OFF position.
Jack Cylinder(s) Extend
When the selected left, right, center, or extend all switch is
held in the UP (extend) position, an input signal is sent to the
programmable controller (PC). A 12 V output signal from the
PC enables the jack cylinder extend solenoid HS-44, HS-46,
and/or HS-48. Internal pilot supply pressure of 14 bar
(200 psi) enables the spool to shift the selected jack cylinder
solenoid valve(s). An internal relief valve and shuttle valve
for each spool valve allows pressure to be divided equally
when more than one valve is operated at a time. The crane’s
PC sends an output signal to shift the crane’s auxiliary
system disable-relief valve HS-12 to block the valve’s
bypass. Accessory system pressure increases to operate
the accessory items. Accessory system fluid enters the
MAX-ER’s accessory valve and flows to the free-flow check
valve section of the counterbalance valve. Fluid pressure on
the piston end of the selected jack cylinder extends the jack
cylinder to raise the counterweight trailer.
Fluid from the rod end of the jack cylinder is blocked by the
free-flow check valve section of the counterbalance valve
and flow-restraining section of the relief valve preset for a
relief setting of 276 bar (4,000 psi). The rod end cylinder
pressure opens the restraining section of the counterbalance
valve, allowing fluid to exit the valve. Return hydraulic fluid
passes through the MAX-ER’s accessory valve before
returning to the crane’s hydraulic tank through the return line.
When the desired jack cylinder extension is reached, release
the selected jack switch to the OFF position to lock the jack
cylinder(s) in position. Hydraulic fluid at the piston end of the
jack cylinder counterbalance valve supports the weight and
gravity force of the wheeled counterweight trailer.
DANGER
Tipping Hazard!
The wheeled counterweight assembly can tip:
• Extend and retract the jack cylinders slowly to
maintain the counterweight trailer as level as
possible.
• Do not extend the jacks if the counterweight trailer is
not attached to the crane and the wheels are not at a
90-degrees (stand-alone) position.
• Make sure the counterweight tray pins are in proper
position when raising the counterweight trailer with
the jacks.
• Read and understand the counterweight trailer jack
procedure before operating the MAX-ER remote
switch.

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English