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Solution to increase the resistance and durability of slings – Steel Cables

Improper folding of the body of the sling can cause a reduction in strength and permanent damage.


🔸 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.


🔸 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.


🔸 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.

Photo 1: 85-ton shackle with a roller Ø 150 mm at the bottom of the “V”, for cable Ø 57 mm.

Photo 2: Vertical pressure vessel, 81 tons, height 28 m, lifted by 4 lifting points.

Photo 3: Detail of the roller with the sling folded around the body, with the cable under tension. D/d = ratio between the bending diameter and the cable diameter.

Photo 4: Rollers can also be used for tubular flat straps. This one is for a 55-ton grade 8 shackle. It is made of aluminum, and the contact surface is flat.