In the construction of crane, the hook is an important part. When the crane works, the weight is lifted by the hook, and then the weight is removed.
Therefore, in the crane maintenance, the maintenance of the hook is essential, the maintenance of the hook first has to do the hook inspection, the following detailed inspection methods of the hook.
Crane hook is mainly composed of pulley, pulley shaft, anti-decoupling device, hook body, beam, bearing, combination bolt, round nut, guide rope block and splint.
In order to ensure the normal operation of crane hook, crane operators and maintenance personnel should carry out safety inspection on these parts according to the actual situation. The inspection includes 3 items: 1) checking technical documents; 2) checking appearance and surface cracks; 3) measuring wear amount, opening degree and torsion deformation.
1. Check technical documents
Before the new crane is put into operation, operators should check the relevant technical documents of hook assembly.
The rated load of the label of the hook assembly shall conform to the actual load of lifting, and the related technical documents and factory certificate of qualification shall be complete.
2. Appearance inspection
The crane operator shall inspect the appearance of the hook assembly every day, and the requirements of each part are as follows: the pulley shall rotate flexibly on the roller shaft without obvious slack;
The rim of the pulley shall not be damaged or cracked, otherwise it shall be replaced.
The decoupling device should be opened and closed freely and its spring should be intact to prevent the wire rope from slipping off the hook body;
The hook body should rotate flexibly on the bearing at the beam.
Round nuts and combination bolts should not be loose.
3. Check the surface cracks of the hook body
Clean the hook body with kerosene first, and then check whether the hook body is cracked with a 20-fold magnifier.
For the crane hook of super-large tonnage, non-destructive inspection (magnetic inspection, ultrasonic inspection) should be used to check whether the hook is cracked inside or outside.
If there are cracks on the surface and inside of the hook body, it should be replaced immediately.
4. Measure the geometric dimensions of the hook
The caliper or caliper should be used to measure the amount of wear on the surface of the hook during the regular annual inspection of the crane.
If the wear of the larger section under force reaches 10% of the original size, it should be replaced.
The lifting hook assembly shall be disassembled and checked during crane overhaul, and the wear of roller shaft, beam, bearing and clamp shaft hole shall be measured.
When the wear reaches 5% of the original size, it should be replaced.
(2) opening degree
The measurement method of the opening degree of the hook body is as follows: load test was conducted according to the rated load indicated on the hanger label, and the load was gradually increased to 1.25 times of the rated load in an incremental manner, and the lifting time was not less than 10min.
Measure the opening of the hook with caliper after unloading. Compare the value with the original opening size, the increase of the opening should not exceed 0.25%.
When the new hook is used, one mark can be made by the punch on both sides of the opening of the hook body, and the distance between the marks can be measured and recorded as the original opening size.
If the opening deformation of the hook body increases by 15% compared with the original opening, it should be replaced.
(3) torsional deformation
The measurement method of the torsion deformation of the hook body is as follows: the side edge of the steel ruler is used to hold the side of the hook body, and the clearance between the steel ruler and the side of the hook body is observed.
If the gap between the two sides of the hook body is different, it indicates that the hook body has torsional deformation.
If it is necessary to measure the torsion deformation of the hook body accurately, it can be disassembled and placed on the platform for detection with scriber.
Hook torsional deformation of more than 10 ° should be replaced.