1.4.2 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.

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 position by the boom angle sensor and the boom length sensor, 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 derricking cylinder to the moment limiter.

The moment limiter comparatively calculates between the "rated total load" computed out of the current position and the "actual 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 actual 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 sensor, boom length sensor, 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 1.4.9 Moment Limiter Error Causes and Actions to be Taken”.

1.4.3 MOMENT LIMITER OPERATIONS

The moment limiter is a device for unexpected events. Do not rely solely on the device to avoid danger. Pay sufficient attention during the operation not to cause auto-stop of the crane.

[1] PROHIBITED ACTIONS AFTER AUTO STOP

The following crane operations are prohibited after the crane has stopped automatically due to overloading. These operations may cause overturning of the machine or breakage of the boom and are very dangerous.

• Boom lowering operation • Boom extending operation • Hook raising operation

• Crane slewing operation

[2] MOMENT LIMITER OPERATIONS

Be sure to switch the engine speed to low speed and perform crane operation carefully if the moment limiter load factor is 90% or higher.

Performing crane operation at high engine speed will swing the hoisted load and is very dangerous, causing overloading and it may break the boom.

1. Safety Zone (With load factor of “less than 90%”)

When the hoisting load is less than 90% of the rated total load, the working status lamp lights in green, indicating normal operation status.

2. Pre-Warning (With load factor of “90 to less than 100%”)

When the hoisting load reaches 90% of the rated total load (pre-warning), the working status lamp changes from green to yellow and the alarm sounds intermittently, notifying the operator and those around that the hoisting load is close to the rated total load.

Green lamp light up

3. Limit Warning (With load factor of “100% or higher”)

When the hoisting load reaches 100% of the rated total load by continuing the crane operation after exceeding 90% of the rated total load (pre-warning), the working status lamp changes from yellow to red and the alarm now sounds continuously. The following crane operations will stop automatically.

• Hook raising operation • Boom extending operation

• Boom lowering operation

The LED of “100%” on the moment limiter load factor display lights up.

Yellow lamp light up

Red lamp light up

4. Recovery Operation from Auto Stop

The recovery operation from overloading should be the reverse operation of the crane operation that caused the auto stop. Perform one of the followings.

(1) Lower the hook and put down the hoisted load on the ground.

(2) Raise the boom. Lower the hook so that the hoisted load will be as low as possible.

(3) Retract the boom.