Basic Rigging
Load, sling, and hardware
Rigging transfers a load safely from one place to another. Know the load weight, its center of gravity, and the working load limit (WLL) of every component: slings (wire rope, chain, synthetic web), shackles, hooks, links, and eyebolts. Never exceed the WLL, and remember the WLL already includes the design safety factor - do not add your own. Each hitch changes capacity: a vertical hitch carries the full rating per leg, a choker hitch typically reduces capacity about 25 percent, and a basket hitch can roughly double it when legs are vertical. Inspect slings before each lift and remove any with cuts, broken wires, stretched links, burns, or missing tags.
Sling angle is the number-one trap
As the angle between the sling leg and the horizontal decreases, tension in the leg increases. Use tag lines to control rotation, keep personnel clear of the load and the swing radius, and never ride the load or stand under it. Only one designated signal person directs the operator, using standard hand signals or radio; anyone may stop a lift.
Worked example
A 2,000 lb load on a two-leg bridle with legs at 60° from horizontal: each leg carries 1,000 ÷ sin 60° = 1,000 ÷ 0.866 ≈ 1,155 lb. At 30°: 1,000 ÷ 0.5 = 2,000 lb per leg - the tension doubles as the angle flattens. Keep sling angles at 60° or steeper from horizontal whenever possible.