Operational Planning: Load Estimation, Slinging, Rigging and Communication
Plan before you lift
Operational planning starts with the load: mass, centre of gravity, shape, fragility and lifting points. Estimate mass from drawings, markings or calculations; never guess. Add the weight of slings, shackles, spreader beams and hook block to get the gross load, then compare with the chart capacity for the planned trolley position.
Slinging and rigging
Choose slings rated for the load and the configuration. A two-leg sling at 60° from horizontal shares load differently from one at 30°. The included angle matters: as the angle between legs widens, tension in each leg rises. Use edge protection, avoid sharp bends, and ensure the hook latch closes. The centre of gravity must sit below the hook to prevent tilt and load shift.
Communication
Agree signals before the lift. Hand signals, radio or whistle codes must be understood by the operator, rigger and spotter. One person directs the lift; only the designated signaler or an emergency stop call overrides. Radios need a clear channel and battery check.
Traps
Questions test whether you include lifting gear in the load, whether you account for sling angle, and whether you let an unauthorised person signal. "The rigger said it was fine" is not a plan.
Worked example
A 4 t machine with two lifting points is slung with two legs at 45° to horizontal. Each leg carries about 2.83 t (4 t ÷ (2 × sin 45°)). Select slings rated above that, add edge protection, and confirm the hook is directly above the centre of gravity.
Rule of thumb
Gross load = load + all lifting gear. Leg tension rises as the angle flattens - keep legs as vertical as practical.