Manitowoc 2250 Service Maintenance Manual

Reference Only
Manitowoc Published 07-19-16, Control # 249-01 1-55
2250 SERVICE/MAINTENANCE MANUAL INTRODUCTION
1
Jacking Cylinders Retract
The following operating description is for the front jacks.
Operation of the rear jacks is the same, except different
switches are used.
When the power button is pressed and both left and right
front jack switches are held in the DOWN (retract) position,
an input voltage is sent to the PC. The PC sends a 12 V
output signal to the auxiliary system’s disable-relief valve
HS-12 that adjusts system pressure to 276 bar (4,000 psi).
The PC also sends a 12 V output signal to enable the jacking
solenoids HS-26 and HS-28 to extend the left and right front
jacks. Hydraulic pilot pressure at 24 bar (350 psi) or 21 bar
(300 psi) shifts the valve(s) in the selected direction.
Hydraulic fluid from the auxiliary pump flows through the
auxiliary system’s disable-relief valve HS-12 and enters the
accessory valve. Fluid exits the valve sections of the
accessory valve and flows through the free-flow check valve
sections of the counterbalance valves. Fluid then enters the
rod end of the front jacking cylinders, retracting the cylinders
to lower the front of the rotating bed.
Fluid exhausting from the piston end of the jacking cylinders
is blocked by the free-flow check valve sections of the
counterbalance valves. From the counterbalance valve, fluid
flows through the flow-restraining section that has a relief
setting of 172 bar (2,500 psi). The counterbalance valve acts
as a deceleration control and functions with a 3:1 pilot ratio of
the relief pressure. This permits the valve to open when the
pressure in the piston end of the cylinder is approximately
57 bar (833 psi).
The restraining section of the counterbalance valves opens
to control the fluid out of the jacking cylinders while
maintaining back pressure on the piston end of the cylinders
to prevent the rotating bed from falling or lowering. Hydraulic
fluid then flows through the free-flow check valve section of
the flow control valve before entering the upper accessory
valve and returns to the tank.
When the power button or jacking switch is moved to the
OFF position, the PC sends a 0 V output to shift the spool of
solenoid valves HS-26 and HS-28 to the center position.

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English