1 The surface has crack or break;
2 The hook tail and the thread part and so on the dangerous section and the hook tendon has the permanent distortion;
3 The wear of the hanging rope is more than 10% of the original height;
4 The opening degree is 15% higher than the original size, and the opening torsion deformation is more than 10 °;
5 when the plate hook bushing wears up to 50% of the original size, the liner should be scrapped;
6 The core axle of the board is worn out when it reaches the original size of 5%.