The hook is an important part of the chain electric hoist, it not only bear the weight of the object, but also bear the impact load of rise and braking, so the hook material mechanical should have high strength and impact toughness. The commonly used hook according to the manufacturing process can be divided into forging hook and plate hook. The forging hook generally forged by 20SiMn, 36Mn2Si and other steel, while plate hook is forged by the multiple pieces of steel plate riveted joint, generally use 20# steel, 16Mn steel. The plate hook is convenient to manufacture, and the load can be uniformly distributed on each steel plate, and the fracture can not happen at the same time, so the reliability of the work is higher than the forging hook. Hook once broken in use process, can cause accidents. Therefore in use must pay attention to check, use a magnifying glass check whether there are cracks. Once found crack, immediately stop using.
The hook dangerous section is the section of maximum bending stress.
The maximum bending moment at the point, and often appear groove cause to the friction of the wire rope, when the wear of the dangerous section reaches 10% of the original height, should be scrapped immediately. It is absolutely not allowed to continue to use after rewelding.
Hooks must be strict inspection before delivery, and loading capacity shall be all above the nameplate, can not use if there is no capacity mark, until it is calculated, determined the safety of the weight, and do the load test which load is 1.25 times the benchmark, no permanent deformation and crack phenomenon in the test. For the hook which is used regularly, should always check whether there is permanent deformation and wear. The hook should be equipped with a safety device to prevent unhooking.