Maintenance, Wire Rope, and Component Wear Limits
Wire rope removal criteria
For running ropes, remove from service at 12 randomly distributed broken wires in one lay, or 4 broken wires in one strand in one lay. Rotation-resistant rope is stricter: 2 broken wires in six rope diameters or 4 broken wires in 30 diameters. Diameter reduction limits are 3/64 in for rope up to 3/4 in, 1/16 in for 7/8 to 1-1/8 in, and 3/32 in for 1-1/4 to 1-1/2 in. Also reject kinking, crushing, bird-caging, severe corrosion, heat damage, electric-arc damage, and broken wires at end fittings.
Components and maintenance
Check sheave grooves for wear that lets the rope bottom, broken flanges, and misalignment. Hooks with a throat opening increased more than 15% (or 1/4 in, whichever is greater), more than 10° twist, 10% wear, cracks, or a missing latch should be removed. Keep brakes adjusted, linkages tight, and records current. Maintenance does not reset the load chart; repairs must restore the original configuration.
Worked example
A 7/8 in nominal rope measures 0.800 in. The reduction is 0.075 in. The limit for 7/8 to 1-1/8 in rope is 1/16 in (0.0625 in). The rope is removed. The fact that the loss is under 9% of the nominal diameter shows why the limits are absolute, not a judgment call.
Traps
Counting broken wires only on the visible side; confusing lay length with rope length; painting over corrosion; reusing cotter pins; and installing wire-rope clips with the U-bolt on the live end are common errors.