Mini-Crawler Crane M A E D A Section 4 – MOMENT LIMITER (OVERLOAD DETECTOR)
1/2019 MC405C-3 4-69
Function of Moment Limiter
WARNING!
• Do not remove, disassemble, or repair
detectors. Do not move the detectors to
another location from original position.
• Should an object hit a detector or you find
any damage on a detector, be sure to verify
the actuation status of the auto stop.
If you find any abnormality with the
actuation of the auto stop, do not fail to fix
it.
• Do not turn ON the moment limiter override
switch unless you find an error or
check/perform maintenance on detectors.
Setting the moment limiter override switch
to the "ON" position disables the moment
limiter function for three minutes.
Overloading can cause the hoisted load to
fall, boom breakage, or overturning of this
machine that can lead to serious accidents
resulting in death or serious injury.
Note that if the moment limiter override
switch is set to the "ON" position and the
moment limiter function is disabled, the
working status lamp will light up in red and
the warning buzzer will sound.
• The machine will not stop automatically
even if the crane is overloaded during the
crane slewing operation. Do not slew the
crane when being overloaded.
• When the boom approaches the stop
position during the operation, be sure to
change the operation speed of the boom to
low speed.
With high-speed boom operation, the boom
may overrun the specified stop position,
causing serious accidents such as
overturning of the machine resulting in
death or serious injury.
Fig. 4-178
The moment limiter is a device installed to
prevent the hoisted load from falling, the boom
from breaking, or the machine from overturning
due to overloading.
Always check the operation of the moment limiter
before crane operation to verify no abnormality.
Fig. 4-179
Mechanism of Moment Limiter
The moment limiter calculates current "rated total
load" by knowing the current boom posture by
the boom angle gauge and the boom length
gauge, by knowing the outrigger extension
condition by the outrigger position switch, and by
knowing the number of wire falls (entered by the
operator).
Then by actually hoisting a load, the "read load"
(hoist load) is sent from the pressure sensor of
the derrick cylinder to the moment limiter.
The moment limiter comparatively calculates
between the "rated total load" computed out of
the current posture and the "real load" (hoisted
load), and issues an alarm if the result indicates
the real load/rated total load=90 to 100%.
If the calculation result indicates the real
load/rated total load=above 100%, an alarm is
issued and the causes the boom operation to
automatically stop.
Display of Moment Limiter Error
Messages
The moment limiter performs self-diagnosis on
the moment limiter display unit when an error is
issued by the boom angle gauge, boom length
gauge, pressure sensor, or when a circuit is
opened or a connector is disconnected.
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