Load and crane
Crane load chart utilisation
- where
- total lifted weight (t)
- weight of the load (t)
- hook block, if not deducted on the chart (t)
- lifting accessories and rigging (t)
- load chart utilisation (%)
- rated capacity from the chart at the radius (t)
- spare capacity (t)
Explain this equation
Adds everything hanging on the crane hook and compares it with the capacity on the load chart. Use it for every lift as the basic capacity check.
m is the weight of the load. m_hb is the hook block, if the chart doesn't already deduct it, and m_r is the slings, shackles, beams and other gear. W_t is the total lifted weight. C is the rated capacity read from the chart for the actual radius and set-up. U is the percentage of that capacity used, and S is what is left.
The crane only knows the total weight on the hook, so every item below the sheaves counts against the chart. Utilisation is simply that total divided by the chart capacity.
Sense check: an 8.2 t load with 0.5 t of hook and rigging on a 10 t duty uses 87%. Small changes in radius can change C a lot, so read it at the furthest point the load will reach.
Watch out: check the chart notes on what is already deducted. This is a static check only, with no allowance for wind or dynamic effects.
Adds up everything hanging on the crane and compares it with the rated capacity read from the chart.
Enter your values to see the result.
Good to know
Read the chart for the actual radius (to the load’s furthest position, not just the pick-up), boom length, counterweight and outrigger set-up. Check the chart notes: some manufacturers deduct the hook block and some do not. Include slings, shackles, spreader beams and any packing. Allow for weight uncertainty in the load itself; use the weighed or certified weight where you can.
Common mistake
Reading the capacity at the pick-up radius when the load has to be placed further out, or forgetting the weight of the hook block and spreader beam.
Limits
Static check only; ignores wind (see the wind calculator), side load and dynamic effects. For planning only: this does not replace a lift plan prepared by a competent person under LOLER 1998 (reg. 8) and BS 7121, and the manufacturer’s WLL markings, load charts and data always govern over this result.
Sources
- BS 7121-1:2016 Code of practice for safe use of cranes. General (lift planning, appointed person, multiple-crane lifts, ground conditions, wind)
- The Lifting Operations and Lifting Equipment Regulations 1998 (SI 1998/2307), reg. 8: every lifting operation properly planned by a competent person, appropriately supervised and carried out safely
- HSE L113 Safe use of lifting equipment. Lifting Operations and Lifting Equipment Regulations 1998. Approved Code of Practice and guidance
Results are calculations from the published methods and figures shown, and depend on the data you enter. For planning and checking only. Scaffolds must be erected to NASC TG20 or a bespoke design by competent persons, and lifting operations planned under LOLER by a competent person. Never rely on these results instead of a design, a lift plan or manufacturer ratings.