Rigging calculator

Start with the load: its weight, where the lifting points are and, if you know them, its height and size. Pick how it will be rigged, then set each level from the hook down. For every sling, chain, beam and shackle it gives the angle and the rating it needs, plus the weight on the hook, the height from the hook to where the load sits and the clearance above the load. The drawing is to scale and changes as you go.

Slings or a chain set straight from the hook are the simplest and need the least kit. A spreader beam, lifting beam or frame keeps the slings upright, which you need when the lifting points must be pulled straight up, when the slings would crush or bear on the load, or when the headroom is too tight for long slings. In step 3 the calculator lists the rigs that fit your load and the kit you have; pick one and change any part of it.

On a stiff load the four legs will rarely share it evenly, so the standards rate a 4-leg sling as if three legs carry it. The calculator does the same, and where only two diagonal legs could end up carrying the load it tells you what each would take.

When more of the load hangs under one end of a beam than the other, for example a 4-leg sling at one end and a 2-leg at the other, the hook has to sit over the centre of gravity. The top legs are then different lengths. The calculator works out the lengths; use slings made to length, turnbuckles, chains with adjusters or chain blocks, and check on a trial lift that the load hangs level.

From the LEEA Code of Practice for the Safe Use of Lifting Equipment, the British and European standards for chain, wire rope, webbing and roundslings, BS EN 13155 for beams and frames, BS 7121 and makers’ guidance. Where no standard covers a case, such as six or eight top legs on a frame, the rule is our own cautious assumption, for the appointed person to check. Tap any item in the kit list to see the standard it is rated to, or where to check the maker’s data.

No. It is a planning guide to help you choose and size the rigging. The appointed person plans the lift, checks the makers’ limits for the actual kit, and confirms the rigging in the lift plan. Use the ratings marked on your equipment.