9/8/2023 0 Comments Rigging sling chart![]() Assuming a CoG that lays exactly in the center of the box. When lifting a box on 4 equal lifting points. This factor is totally arbitrary and nowadays implemented the same way for every kind of material, no matter if it is polyester, HMPE or steel. To compensate for this difference in length engineers multiply the minimal required breaking load with a safety factor of typical 1.25, this is called the Skew-load-factor (SKL). This way the tolerance is somehow controllable, but the bigger the loads(and so the bigger the sling diameter), the larger the allowable length difference may be. This term has multiple possible definitions but mostly it refers to an item-to-tem length difference of max 0,5 times the sling diameter. In order to deal with this uncertainty, suppliers are requested to manufacture their slings in so called ‘matched pairs’. Elasticity in material will compensate for this effect as the shortest sling will stretch and distribute more of its load towards the other 3 slings in the rigging, but in material with low elasticity this effect is limited. Obviously the shortest sling will hold a larger load than the longtest. Especially in lifts with 4 slings to 1 lifting point, different sling lengths will result in different load in each sling. Due to manufacturing tolerances however, in real life one should take into account a certain mismatch in this length. ![]() Current sling tension calculations are typically considering exact sling lengths. ![]()
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