Rigging Hardware and Slings
Core Concepts
This domain covers the hardware that connects the crane to the load: shackles, hooks, links, swivels, turnbuckles, eye bolts, and the slings themselves-wire rope, chain, synthetic web, and synthetic round sling. Candidates must know that every component has a rated capacity marked on it, and that the assembly is only as strong as its weakest link. Shackle pins must be fully seated and the shackle must not be side-loaded. Hooks need a functioning safety latch, and the load should sit in the bowl of the hook, not on the tip.
Sling Selection and Care
Wire rope slings fail from broken wires, kinking, crushing, and corrosion; chain slings from stretch, cracks, and worn links; synthetic slings from cuts, abrasion, ultraviolet degradation, and chemical damage. Each sling type has its own removal-from-service criteria, and questions often ask you to identify the correct defect for a given sling. Know that synthetic slings must be protected from sharp edges and heat, and that sling angle affects capacity-capacity decreases as the angle from horizontal decreases.
Traps and a Rule of Thumb
Traps include confusing working load limit with breaking strength, using a shackle with a screw pin that is not fully engaged, and assuming a sling's capacity stays constant regardless of hitch type or angle. Another trap is mixing hardware of different ratings in one assembly.
Worked example: A two-leg bridle sling with legs at 60° from horizontal carries a share of the load in each leg equal to (load/2) ÷ sin 60° ≈ 0.577 × load per leg-so the legs see more tension than half the load. Always check the tag and the angle before lifting.