Linkage Operation of Overhead Crane

In the actual production process, sometimes we encounter situations where the mass of the hoisted object exceeds the rated lifting weight of the on-site bridge crane, or the hoisted object is too long, the bridge crane is unstable, the hoisted object is deformed, and other practical problems. In the above situation, if conditions permit, methods are appropriate, on-site command is strengthened, and safety is ensured, the solution of collaborative hoisting by two bridge cranes can be adopted.

The operation method is as follows: When two bridge cranes jointly hoist the same object, the first thing to meet is the most basic condition that the sum of the rated lifting weights of the two bridge cranes must be greater than the mass of the hoisted object. If the hoisting method of the balance beam is used during hoisting, the requirements are as follows:

• Go+Gb≤G1+G2

• Go: weight of object lifted, t

• Gb: weight of balance beam, t

• G1, G2: rated lift weight of 2 overhead cranes, t

The balance beam is to reasonably distribute the mass of the hoisted object to the load-bearing components of the two bridge cranes. Therefore, it must meet the strength and stiffness conditions to ensure the safety and reliability of the hoisting work.

To ensure safety, when two bridge cranes work together to lift the same object, the following rules must be followed:

(1) Under the leadership of the relevant departments, relevant personnel such as equipment, production and safety technology must participate in the development of lifting plans and lifting processes.

(2) After the lifting process is determined, the contact signals and gestures between the bridge crane driver and the ground commander must be unified. The entire lifting operation must be directed by a dedicated person, and the division of labor of various operators should be clear and each should be responsible for their own duties. Safety inspection supervisors should be assigned to conduct on-site safety inspections.

(3) In addition to a comprehensive and careful inspection of the mechanical, electrical and metal structures of the two bridge cranes, special attention should be paid to the inspection of the hooks, wire ropes and brakes of the lifting mechanism. Defective machinery must not be used.

(4) Before the two bridge cranes are officially hoisted, the balance beam should be hoisted for coordination test, that is, the same mechanism of the two bridge cranes should be started at the same time, the difference in the working speed of the two bridge cranes should be measured, and the respective working gears should be determined in advance, so as to achieve the same speed or nearly the same speed of the two bridge cranes; if the working speed difference of the two bridge cranes is large, the coordination plan of intermittent work can be determined in advance to prevent accidents caused by uncoordinated actions during the formal hoisting.

(5) Before the formal hoisting, the drivers of the two bridge cranes should start the lifting mechanism at the same time to lift slowly. When the hoisted object is about 200mm off the ground, the brakes should be lowered to check the reliability of the lifting mechanism brake. Only when it is confirmed that there is no problem can the formal hoisting be carried out.

(6) During the hoisting process of the two bridge cranes, only the same mechanism is allowed to be started at the same time, and two mechanisms are not allowed to be started at the same time to prevent accidents caused by misalignment. In addition, they should work at the slowest gear speed of each mechanism to adjust the speed difference of the two corresponding mechanisms. Sudden rapid start and rapid start are strictly prohibited.

(7) To ensure that the two bridge cranes can work in coordination, the bridge crane driver must always pay attention to the balance of the hoisted object during operation, always pay attention to the signals sent by the ground commander, and always adjust the working speed of the mechanism to ensure that the balance beam or the hoisted object always maintains a horizontal balance state. This is the key to safe and correct hoisting work.

(8) When starting and braking the mechanisms of the two bridge cranes, they must strive to be smooth and sudden starting and braking are not allowed to eliminate the impact on the bridge crane caused by excessive inertia due to too short acceleration time.