Crane rigging utilizes four primary hitch configurations to secure loads, each with specific Working Load Limits (WLL) dictated by ASME B30.9 standards.
- A vertical hitch connects the load directly to the hook, delivering 100% of the sling’s rated capacity.
- A choker hitch wraps around the load and passes through itself, providing excellent grip but reducing the capacity to approximately 75% to 80% depending on the sling material.
- A basket hitch cradles the load with both sling eyes on the hook, yielding up to 200% capacity when legs are perfectly vertical.
- For large or asymmetric loads, a bridle hitch uses multiple legs to distribute weight.
When employing basket or bridle setups, qualified riggers must calculate sling angles; any horizontal angle under 90 degrees significantly increases tension and reduces safe lifting capacity, as outlined in OSHA 1926.251 requirements.
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