(1) Lifting height limiter

The restriction of the hook combination entering the boom head is limited by a differential limit device. Regardless of the position of the boom, when the hook combination approaches the boom head with about 2 meters left, the lifting direction and the lowering direction of the amplitude automatically stop, but the hook can be lowered and the boom can pitch up.

(2) Maximum and minimum arm amplitude limiters

Crane arm angle limit: The working range of the crane is 3.5-16m, and the corresponding elevation angle of the crane arm is 27-79 °. The angle limit is ensured by the limit switch installed on the side of the tower turntable and touched by the foot of the crane arm. When the elevation angle of the boom is greater than 79 °, two buffers are installed on the tower head to support the crossbar of the boom. When the lifting arm needs to be placed on the bracket, it can be lowered by pressing the foot switch.

(3) Slewing angle limiter, suitable for cranes with limited slewing angle.

(4) Travel limiter, suitable for walking cranes (such as cantilever cranes) and bridge cranes.

After the above limiter is activated, an alarm should be triggered, the operating power should be cut off, and the lifted load and crane should be able to be kept in the position of the limiter, except for auxiliary cranes (such as food cranes).

(5) Mechanical limit protection

① Hook high position protection: When the hook is at a short distance from the front end of the boom, lifting or lowering the boom cannot be carried out.

② Terminal protection of lifting rope: When the lifting rope is fully rolled, the hook stops lifting, and when there are only 3 turns left on the drum, the hook stops falling.

③ High and low position protection of the boom: When the boom is controlled by an oil cylinder, there is no need to install high position protection. The low position protection of the lifting arm is always located at an elevation angle of 25 ° above the horizontal line. When lifting goods, it is not allowed for the lifting arm elevation angle to be lower than this limit. When the work is completed and it is necessary to level the lifting arm, the dedicated button must be pressed.

In addition, the limit of the highest and lowest positions of the boom is ensured by the limit device next to the lifting drum, while preventing the steel wire rope from loosening. When the hook is placed in the lowest position (touching the corner of the bottom plate), there should be no less than 3 turns of steel wire rope left on the drum. When the hook is raised to the highest position, there should be about 1 turn of empty groove left on the drum.

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