The boom of crawler crane is usually not more than 78 degrees, and the elevation of the arm is too large, which is easy to cause the phenomenon that the crane is inclined or inclined. Crane to arm dropped to 40 degrees to 60 degrees, and transferred to the downwind direction, to reduce arm windward area, prevent windy arm blown backward, overturned and folded rod accident.

In order to ensure the safe operation of the operation, the crane is provided with a safety device:

(1) a weight indicator (angle plate, also called the weight limit)

The angle indicating that the root of the arm is close to the driving position, it changes with the elevation angle of the arm, reflecting the angle of the arm to the ground, and knowing the elevation of the different position of the arm.

(2) a hoisting limiter (also known as super limiter)

Installed in the arm end of the pulley block limit hook lifting height, to prevent the occurrence of after lifting safety device. It guarantees the hook lifting to the limit position, can automatically send out alarm signal or cut off the power supply stops lifting, to prevent excessive volume.

(3) torque limiter

The torque limiter is a limiter for preventing overload caused by the overload of the crane when the load torque is reached when the load torque is automatically cut off or the variable amplitude power source is automatically cut off.

(4) anti boom device and anti back bar bracket

The anti boom device and the anti back bar bracket are the safety device when the boom is raised to the maximum rated angle, and it prevents the boom of the boom.