Rigging
Total rigging weight and hook load
- where
- rigging weight (kg)
- hook block (kg)
- spreader or lifting beam (kg)
- number of slings and mass of each (kg)
- number of shackles and mass of each (kg)
- other items (kg)
- total hook load (t)
- weight of the load (t)
Explain this equation
Totals the weight of the lifting gear and adds it to the load to give the hook load. Use it before the load chart check so nothing hanging on the hook is missed.
m_hb is the hook block and m_sp is a spreader or lifting beam. n_s slings of m_s each and n_sh shackles of m_sh each are counted, and m_o covers master links, packing and tag lines. R_g is the total rigging weight in kg. W_t adds it to the load m in tonnes.
Everything below the hook sheave is lifted by the crane, so it all counts. Dividing by 1000 turns kilograms into tonnes so the result matches the load chart.
Sense check: a 350 kg hook block, four 12 kg sling legs and four shackles add about 0.4 t. On a 5 t load that is an 8% increase.
Watch out: spreader beams and frames are often heavier than expected. Take their weights from the manufacturer's marking.
Adds up the hook block, beams, slings, shackles and other gear so the total hook load can be checked against the crane chart.
Enter your values to see the result.
Good to know
Take masses from the manufacturers’ data or weigh the items. A 4-leg chain sling assembly is usually entered as one sling with its total mass. Spreader beams and lifting frames can weigh more than the load on light lifts. Carry the total into the load chart utilisation calculator.
Common mistake
Leaving out the spreader beam or the hook block because they “belong to the crane”. Everything below the hook sheave counts unless the chart notes say otherwise.
Limits
Simple sum; no allowance for weight uncertainty. 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.