Cranes – Sling capacities aren’t always what they seem
All slings should have a tag showing their capacity using a vertical, basket, or choker hitch. Typically, a 3,000 lbs capacity sling used in the vertical will be rated twice that in a basket (6,000 lbs), and about 75% in a choker (2,250 lbs).
Furthermore, slings used at angles require an additional reduction. For example: If two 3,000 lb. capacity slings are used to pick a 5,000 lb. load, whose center of gravity lies equally between the two pick points, and the angle of these slings is 45°, then each sling is going to see more than half the load that they would see if they were vertical or at 90° (2,500 lbs). The sling angle factor at 45° is 1.414; multiplied by half the load equals 3,535 lbs; and so each of these slings is being overloaded by 535 lbs.
Similarly, a true choker (angle of choke is between 120° – 180°) who’s capacity is 2,250 lbs could be reduced by up to 50% more if its angle of choke is below 30°. (This could be the case if you pounded down on the eye to get a tighter grip or if the choker hitch is used to turn a load.)
So, the 3,000 lb. vertical capacity sling used in this example could be rated at 6,000 lbs if used in a true basket or reduced to 1,125 lbs if used in a tight choker to turn a load. Makes you think, doesn’t it.