Rigging, Slinging, and Load Handling
Rigging, Slinging, and Load Handling
This domain tests hitch selection, sling tension, hardware rating, and control of the load. Expect center of gravity, sling angle, and shock loading.
Core rules
- Know the hitch: vertical, choker, basket, and bridle. A choker derates sling capacity; a basket can increase it only if the legs are parallel and the hardware is rated.
- Sling angle matters. For a symmetrical two-leg lift, tension per leg = load ÷ (2 × sin θ), where θ is the angle from horizontal. Lower angle means higher tension.
- Never exceed the working load limit (WLL) of the weakest component: sling, shackle, hook, master link, or eye.
- Protect slings from sharp edges, heat, and kinks. Use tag lines to control rotation; keep personnel out from under the load.
- The center of gravity should be below the hook for stable lifts; unbalanced loads need two hooks or a spreader.
Worked example: 4,000 lb load, two-leg bridle at 45° from horizontal. Each leg tension = 4,000 ÷ (2 × sin45°) = 4,000 ÷ 1.414 = 2,829 lb. If each sling has a 2,000 lb vertical WLL, the lift is overloaded; use a higher-rated sling or a steeper angle.
Traps
- Using load weight divided by the number of legs as tension.
- Measuring the angle from vertical instead of horizontal.
- Ignoring the weight of the spreader bar or shackles.
- Shock loading a sling by jerking the load.