Maeda MC305C-3 - Function of Moment Limiter; Mechanism of Moment Limiter

Section 4 – MOMENT LIMITER (OVERLOAD DETECTOR) Mini-Crawler Crane M A E D A
4-60 3/2019 MC305C-3
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.
• 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.
• 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.
If the Moment Limiter Override Switch is
"ON" (Override), the Working Status Lamp
will flash in red, and an alarm buzzer will
sound intermittently.
Fig. 4-166
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.
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 rated total load/real load=90 to 100%.
If the calculation result indicates the rated total
load/real load=above 100%, an alarm is issued
and the causes the boom operation to
automatically stop.
Fig. 4-167