The 3-6 wire rope rule is a removal criterion for crane running ropes defined by ASME B30.5 and enforced under OSHA 1926.1413. Under this standard, a crane’s running rope must be immediately retired if a qualified person identifies
- three broken wires in a single strand within one rope lay,
- or six randomly distributed broken wires across the entire rope within one rope lay length. A rope lay length is the linear distance it takes for one strand to complete a full spiral revolution around the core.
Wire rope slings have different removal criteria. Under ASME B30.9 and OSHA 1910.184, a sling must be removed from service when 10 randomly distributed broken wires are found in one rope lay, or 5 broken wires in one strand within one rope lay. (OSHA 1926.251 uses a different criterion for construction: 10% of total wires in 8 rope diameters.) Rotation-resistant ropes have stricter thresholds — 2 broken wires in 6 rope diameters or 4 in 30 rope diameters.
Strict adherence to these removal criteria prevents catastrophic failures during crane operations and heavy lifting. Beyond counting broken wires, a qualified person must also permanently remove ropes exhibiting
- kinking,
- crushing,
- bird-caging,
- core protrusion,
- evidence of heat damage,
- or a localized diameter reduction exceeding 5% of nominal diameter. Any localized narrowing is a critical deficiency warranting close examination. Daily visual inspections are required before each shift, while documented periodic (annual) inspections are required to maintain a safe job site and ensure strict compliance with industrial rigging regulations.
To ensure your lifting gear meets all regulatory safety standards before your next critical lift, review our comprehensive Rigging Inspection Checklist.