Materials Handling, Rigging, and Hoisting
This domain tests your ability to move loads safely: estimating weight, finding the centre of gravity, selecting and inspecting rigging, understanding sling angle effects, and directing the hoist with clear signals. Expect questions on working load limits, sling tension, hardware inspection, and exclusion zones.
Load and rigging basics
- Estimate the load weight before rigging. Weigh a known volume or use a shipping document; never guess on a heavy or awkward pick.
- Identify the centre of gravity and rig above it so the load stays level; add tag lines for control.
- Every sling, shackle, and hook has a working load limit (WLL). Never exceed it, and never tie knots in slings.
- Inspect before use: check tags, cuts, abrasion, broken wires, heat damage, stretched links, and hook latches. Tag out and remove defective gear from service.
- Use shackles and hooks correctly; a hook must be loaded in the bowl with the latch closed, never on the tip.
Sling angles
- Sling tension rises as the angle from horizontal decreases. For a two-leg sling, tension per leg = (load ÷ 2) ÷ sin of the angle from horizontal.
- At 60° each leg carries about 0.58 of the load; at 45° about 0.71; at 30° the full load per leg.
- Keep included angles moderate; wide slings multiply the load on the sling and on the load's attachment points.
Hoisting practice
- Only one designated signaller directs the operator; everyone knows the stop signal.
- Keep the exclusion zone clear, never stand or walk under a suspended load, and never ride the load or the hook block.
- Watch for power lines, wind, and ground bearing under outriggers.
Worked example
A 2,000 kg load is lifted with a two-leg sling at 60° from horizontal. Load per leg is 1,000 kg; divided by sin 60° (0.866), the tension is about 1,155 kg per leg. The crew selects slings with a WLL above 1,155 kg and checks the shackles and attachment points for the same load. If the rigger had used 30°, each leg would carry 2,000 kg, doubling the tension and likely overloading the same slings.
Traps that cost marks
- Measuring the sling angle from vertical instead of horizontal.
- Ignoring the centre of gravity so the load tips on the pick.
- Keeping a sling in service after visible damage because a tag says it is rated.
- Standing inside the exclusion zone to steady a load by hand instead of using a tag line.