In lifting, hoisting, and other operations, the wear of the diameter of the steel wire rope is one of the important indicators for determining whether it should be scrapped. Many equipment accidents occur because the diameter of the steel wire rope significantly decreases over time, while its load-bearing capacity drops sharply, but it is still being used. According to the safety regulations for lifting machinery in China and the relevant national standards for steel wire ropes, when the diameter of the steel wire rope shows a significant reduction, it must be judged for scrapping strictly in accordance with the regulations, and it cannot be used merely through rough estimation with the naked eye.

The most core and unified scrapping standard is: when the measured diameter of the steel wire rope is reduced by 7% or more compared to the nominal diameter, it must be scrapped immediately and cannot be used any further. Here, the nominal diameter refers to the standard diameter of the steel wire rope when it was manufactured, which is indicated on the nameplate, certificate of conformity, or design drawings; the measured diameter is the average diameter obtained by measuring multiple positions and directions of the steel wire rope using a wide-mouth vernier caliper according to the specified method. Only when the comparison of the two diameters meets the above conditions, does it meet the mandatory scrapping requirements.

The reason for setting 7% as the scrapping limit is that a significant reduction in the diameter of the steel wire rope usually indicates severe damage to the internal structure. It could be that the rope core is compressed or damaged, losing its supporting function; or that the outer steel wires are severely worn and fatigue-strained, causing the structure of the entire rope to become loose and its strength to decrease. At this point, the actual breaking tensile force of the steel wire rope is much lower than the design value. Even if there are not many broken wires on the surface, it may suddenly break under normal loads or even light loads, causing serious safety accidents such as falling objects, failure of the lifting device, equipment damage, and even casualties.