Improper folding of the body of the sling can cause a reduction in strength and permanent damage.
STANDARDS:
🔸 ABNT NBR 13541-1 does not provide specifications for limits on folding of the sling by the body (or throat);
🔸 ABNT NBR 13541-1: Attempt to include these criteria in the next revision of NBR 13541-1;
🔸 ISO 19901-6 Standard: Minimum limit of 2.5 times the cable diameter, considering the loss of strength due to folding by the body.
🔸 ISO 19901-6 Standard: Indicates that only with a folding ratio above 4, there will be no permanent deformation in the cable.
SOLUTIONS:
🔸 Wide body shackles: preferred solution for larger diameter cables. Depends on supplier availability;
🔸 Steel rollers: Increase the pin diameter to mitigate the damage of folding. Depend on a second shackle for the sling to support on the pin with the roller.
🔸 Use of a shackle with greater capacity: solution to be avoided, as it increases the cost and weight of the assembly, as well as handling difficulty.
ROLLERS:
🔸 Made of carbon steel, with a minimum folding diameter of 2.5 times the cable diameter;
🔸 Sizing done by finite elements;
🔸 “V” shaped surface for automatic centering of the sling on the roller
🔸 2 versions: one for slings that do not need to rotate and another for slings that need the roller to rotate, the latter being a differentiated design with additional elements to reduce friction with the pin.
