Rigging and Load Handling
Domain 3: Rigging and Load Handling
The exam tests load control: knowing the weight, selecting and inspecting rigging, understanding sling angle, and keeping the load within the crane's rated capacity.
Core rules
- Determine the load weight and center of gravity before the lift. Use shipping papers, scales or known weights; if the weight is unknown, do not lift until it is verified. Add the weight of slings, shackles, hooks, spreaders and any attached device.
- Inspect slings and hardware before use. Remove slings with broken wires, cuts, burns, chemical damage, distorted hooks, missing latches or illegible tags. Protect slings from sharp edges and heat.
- Hook loads in the bowl, not on the tip; close and secure the latch. Do not side-load hooks or use a hook with a widened throat.
- Sling tension rises as the angle from horizontal decreases. For a symmetrical two-leg bridle, tension per leg = (load ÷ 2) ÷ sin(angle from horizontal). Verify the sling's rated capacity for the actual hitch-vertical, choker or basket-not just its vertical rating.
- Balance the load, control rotation with tag lines, and keep personnel clear of the load and pinch points. Never ride the load or stand under it.
Worked example
A 4,000 lb load is lifted with a symmetrical two-leg bridle at 45° from horizontal. Each leg carries (4,000 ÷ 2) ÷ sin 45° = 2,000 ÷ 0.707 = about 2,828 lb. A sling rated 3,000 lb in vertical hitch is not automatically acceptable if the hitch is choker or basket; use the capacity for that hitch and add shackle and hook weight to the crane load.
Traps
Estimating weight by appearance, measuring sling angle from vertical, ignoring off-center gravity that overloads one leg, using a damaged sling because the tag looks new, and forgetting that the crane chart must include rigging weight.