Rigging and Load Handling
Rigging and Load Handling
Rigging questions test whether you can connect a load so every component is loaded within its rating and the load stays controlled. The exam expects familiarity with sling types, hitches, hardware, center of gravity, and the effect of sling angle. It also expects you to reject a rigging plan that induces side load, shock load, or load rotation.
Core rules
- Know the load’s weight and center of gravity before selecting gear. An asymmetric pick needs a trial lift or load-leveling device.
- Sling tension increases as the angle from horizontal decreases. For a symmetric two-leg bridle, tension per leg = load ÷ (2 × sin of the angle from horizontal).
- Protect slings from sharp edges and heat; never tie knots in chain or wire rope slings; inspect hooks, shackles, and links before use.
- Use tag lines to control rotation. Keep hands clear of pinch points; never ride the load or stand under it.
- Avoid shock loading by taking up slack slowly and lifting vertically.
Worked example
A 6,000 lb load is lifted with a two-leg bridle, each leg at 60° from horizontal. Tension per leg = 6,000 ÷ (2 × sin 60°) = 6,000 ÷ 1.732 = 3,464 lb. If each sling has a 3,500 lb vertical working load limit, the legs are barely within rating-any load shift or angle change could overload them. If the legs were at 30° from horizontal, tension would be 6,000 lb per leg, far over the 3,500 lb rating. The fix is a spreader bar or higher-rated sling, not a slower lift.
Traps
Using the load weight as sling tension; measuring the included angle instead of the angle from horizontal; ignoring hardware weight; and assuming a shackle’s working load limit can be exceeded because it is only a connector.