Slinging Techniques and Load Control
Slinging is about controlling the load, not just attaching it. Before rigging, establish the load's weight (from marking, documentation or calculation - never guess), its centre of gravity, and its lift points. Choose a hitch that suits the load: vertical for straight lifts, choker for bundles and pipes (note reduced capacity), basket for stable support, and double-wrap or choked arrangements for loads that could slip. Use packing or softeners on sharp edges, and tag lines to control rotation and swing. Balance the load so it hangs level; an off-centre load shifts and can spill.
Understand the effect of sling angle. As legs move away from vertical, tension in each leg increases for the same load. A useful rule of thumb is that at 60° from horizontal each leg carries close to the load divided by the number of legs, but at shallower angles tension rises sharply - never exceed the rated angle. Multi-leg slings are rated for a stated included angle; do not assume equal sharing, as the load may be taken by two legs.
Traps: assuming all legs share equally; forgetting that choker hitches reduce capacity; using the load's own sharp edges without protection; and allowing people to guide a load by hand instead of tag lines. Never stand under a suspended load or place hands between load and sling.
Worked example: a 1-tonne load in a two-leg sling at 45° from horizontal. Each leg tension ≈ (0.5 × 1000 kg) / sin 45° ≈ 707 kg, not 500 kg - a 40% increase. Check the sling rating at that angle.