Crane selection and lift planning, without the jargon

A crane described as a hundred-tonne machine will not lift a hundred tonnes anywhere useful. Understanding why makes lift planning much less mysterious.

Capacity falls away with radius

Rated capacity applies at minimum radius, close to the machine. The further out the load, the less can be lifted — and the reduction is steep. The load chart, not the headline figure, is what governs.

The practical consequence is that crane position matters more than crane size. A machine that can stand close may be far smaller than one that has to reach across an obstruction.

What the plan has to establish

• Weight of each lift, including lifting gear
• Radius at pick-up and at placement, not just one of them
• Crane position, and whether it has to move between lifts
• Ground bearing capacity under outriggers, with mats sized accordingly
• Overhead and underground obstructions, including buried services beneath the standing position
• Wind limits, and who stops the lift
• Exclusion zone and how it is kept clear

Ground conditions

Outrigger loads are concentrated and can be several times the load being lifted. Backfilled ground, recent excavation, basements and buried services all need checking before the machine is positioned. This is the item most often taken on trust, and the consequences of getting it wrong are severe.

Wind

A long member is a sail. Lifts get stopped by wind well below any structural limit on the crane, because the load becomes uncontrollable. The plan should state the limit and who has authority to call it, before anyone is under time pressure.