Manitowoc 2250 Service Maintenance Manual

Reference Only
INTRODUCTION 2250 SERVICE/MAINTENANCE MANUAL
1-50
Published 07-19-16, Control # 249-01
Load Drum System—Free Fall
General
See Figure 1-30 and Figure 1-31 for the following.
In Free Fall mode the load can be lowered with the control
handle (Standard mode) or working brake pedal (Free Fall
mode). Depending on the crane’s load drum configuration,
the left load drum working brake pedal on the cab floor
normally operates either full front drum (drum 1) or right rear
drum (drum 2), while the right load drum working brake pedal
on the cab floor normally operates either full rear (drum 2) or
left rear drum (drum 3).
The PC will not allow a drum to be switched to Free Fall
mode until the following steps are performed.
1. Apply and latch the working brake pedal for the drum
being used.
2. For right rear drum operation, place the load drum
selector switch in the right rear (drum 2) position.
3. Select DRUM 2 FFALL on the crane’s mode switch then
turn the switch to confirm the position.
4. Turn the drum 2 park brake switch to the OFF position.
When the selected load drum control handle is in the OFF
position, the load drum pumps do not stroke. If the selected
load drum control handle is in the OFF position when charge
pressure is lost, the programmable controller (PC) applies
the selected drum brake, but the clutch remains released
from the drum’s shaft.
If a low-charge pressure fault occurs while hoisting or power
lowering, the load drum pumps de-stroke. The PC sends an
output signal that applies the clutch to the drum and applies
the selected drum brake. Apply and latch the working brake
pedal before moving the load drum control handle to the OFF
position.
Hoisting the Load Drum—Free Fall
The following description is for hoisting the right rear load
drum (drum 2) while operating in Free Fall mode. Free fall
hoisting of the other load drums is the same, except for
different drum, brake, clutch, and working brake pedal.
The procedure for hoisting in Free Fall mode is the same as
in Standard mode. The selected free fall drum clutch is
engaged, and the brake is released by the PC.
When the control handle is moved to the OFF position, the
selected load drum brake remains released from the drum.
The PC sends a 12 V output signal to the right rear drum
clutch solenoid AS-10 to release the drum clutch. This
applies air pressure to the cylinder of the right rear drum
clutch to release from the drum shaft, returning the drum to
Free Fall mode.
Lowering the Load Drum —Free Fall
The following description is for lowering the right rear load
drum (drum 2) while operating in Free Fall mode. Free fall
lowering of the other load drums is the same, except for
different drum, brake, clutch, and working brake pedal.
In Free Fall mode if a selected load drum control handle is
moved in either direction from the OFF position, the PC
sends an output signal to the right rear drum clutch solenoid
AS-10. This exhausts air pressure from the selected drum
clutch cylinder. The clutch spring applies to connect the drum
shaft to the motor. The load is then controlled in full power in
the direction the handle was moved.
When the working brake pedal is applied, full manifold air
pressure closes the free fall safety pressure switch, sending
an input signal to the PC that allows free fall operation.
WARNING
Falling Load Hazard!
Avoid possible injury. When operating in Free Fall mode,
the load will lower uncontrolled if the drum brake is not
applied with the working brake pedal when the control
handle is moved to the OFF position.
Be ready to apply the load drum working brake pedal so
lowering speed can be controlled and the load can be
stopped immediately, when necessary.
WARNING
Dropping Load Hazard!
Begin moving the selected load drum handle to the OFF
position before releasing the working brake pedal to hold
the load while the clutch releases from the drum shaft.
The hoisted load will drop momentarily if the working
brake pedal is not applied.
CAUTION
Clutch/Motor Hazard!
Do not move a load drum control handle in either direction
from the off position while a load is free falling. Damage to
the clutch and/or motor drive system could occur. Stop the
load with the working brake pedal before moving a load
drum control handle in either direction.
Do not turn Free Fall mode off or turn the drum brake on
while a load is free falling. Stop loads with the working
brake pedal, then turn Free Fall mode off or turn on the
drum brake.

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English