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TOWER CRANE OPERATION AND SERVICE MANUAL
10.5.1 Purpose
The tower crane is calculated and designed according to constant max. load moment.
It is forbidden to exceed the max. load moment. The moment limiter is a device to
inspect the hoisting and trolleying motion with rated load so as to prevent the tower
crane from overturning.
10.5-2 Working Principle
The moment limiter, which is located on the main member at the counter-jib foot, is
composed of a pair of elastic plate, three micro-inching limit switches as well as
installation support, adjustable screw, housing and so on. When hoisting with load,
the elastic plate began distorting (the distance between the two plates became smaller)
due to the action of load moment. If the load exceeds rated value, the adjustable
screw on one elastic plate depresses the switch contact which located on the other
elastic plate so as to cut off the control circuit and stop the mechanism motion.
10.5.3 Adjustments
Special suggestion:
Confirm the rated load moment of tower crane before adjusting the moment limiter,
then debug the relevant data.
1
Light load
Overload
4
A
C
2
D
5
3
SLMO
A (Fixed radius, variable load)
SDMO
C (Fixed load, variable radius)
RDMO
D (Variable radius, deceleration)
1. Elastic plate
2. Limit switch
4. Moment housing
5. Installation support
3. Adjustable screw
Fig. 10.5-1
10B-9
en-version 2.0