Maeda MC-305C-2 - Function of Moment Limiter

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1.6.2 FUNCTION OF MOMENT LIMITER
• 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 (cancel) the emergency stop cancel
switch unless you find an error or check/perform
maintenance on detectors.
When turning ON (cancel) the emergency stop cancel
switch, always shift the crane speed to low.
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.
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.
[1] 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 driver).
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.
[2] DISPLAY OF THE 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.
The result is displayed on the “Rated total load Display” of the moment limiter display unit by an error code
to notify the operator of the error.
Immediately stop the use of the crane when an error code is displayed.
See “Operation 1.6.9 Moment Limiter Error Causes and Actions to be Taken”.