What is a wire rope sling and when must it be removed from service?

Wire rope slings are among the most widely used rigging components in crane work. They are fabricated from wire rope formed into a loop or multiple-loop configuration, with the ends typically terminated by swaging, mechanical sleeve splicing, or hand tucking. Wire rope slings combine high strength with flexibility, making them suitable for a wide range of load shapes, weights, and environmental conditions. However, wire rope is subject to progressive degradation from use, and ASME B30.9 establishes specific conditions that require immediate removal from service.

Wire Rope Sling Configurations and Ratings

Wire rope slings are available in several standard configurations. A single-leg eye-and-eye sling is used in vertical, choker, or basket hitches. A two-leg bridle sling uses two legs joined at a master link to create a shared pickup point. Multi-leg slings (three and four legs) are used for loads with multiple attachment points or loads that require controlled load orientation. The rated capacity varies by configuration and by the angle of the sling legs from vertical in basket and bridle applications. ASME B30.9 tabulates rated capacities for each standard configuration, wire rope diameter, and construction type (6x19, 6x37, etc.) for each hitch type at standard sling angles.

Inspection Requirements

OSHA 1926.251 and ASME B30.9 require that wire rope slings be inspected before each use by a qualified person. The inspection should check for the following conditions, each of which requires immediate removal from service: ten randomly distributed broken wires in any rope lay, or five broken wires in one strand in one rope lay; severe abrasion, scrubbing, or crushing that has flattened or deformed the rope cross-section by more than one-third of its normal diameter; kinking, crushing, or bird-caging that has disturbed the rope structure; heat damage evidenced by discoloration, brittleness, or fused wires; evidence of corrosion that has pitted or noticeably reduced the wire diameter; damaged, cracked, or deformed end fittings; and any indication of core failure or loss of core support visible through the outer strands.

Proper Use Practices

Wire rope slings must be protected from contact with sharp edges on loads. A sling draped directly over a steel beam flange or structural angle without edge protection will develop broken wires at the contact point rapidly. Corner guards or softeners must be used whenever the sling contacts a radius of curvature smaller than the minimum specified by ASME B30.9 for the sling diameter. Slings must not be dragged along the ground or across abrasive surfaces, and they must not be exposed to chemicals or temperature extremes beyond the manufacturer's rated range. Storage should keep slings coiled or hung, not piled on the ground where they can be damaged by vehicular traffic or heavy equipment.