Why Can’t Wire Rope Slings Be Made from Rotation-Resistant Wire Rope?

Industry Standards and Specifications

One of the most frequently asked questions from our clients is: Why are rotation-resistant wire ropes not used for sling fabrication? According to European and international standards, there are specific limitations:

• EN 13411-1 allows only 6×19 and 6×36 classes for fiber-cored ropes and 6×19, 6×36, and 8×36 classes for steel-cored ropes.
• ASME B30.9 explicitly excludes rotation-resistant wire ropes for slings, permitting only wire grades of 1770 and 1960 N/mm².

These standards are based on extensive research and practical performance data that highlight the risks associated with using rotation-resistant ropes in slings.

Design Characteristics and Internal Stresses

Rotation-resistant wire ropes are specially designed with inner and outer strands laid in opposite directions. This structure helps to counteract torque and prevent the rope from twisting under load. However, it also creates a unique set of challenges:

• The opposing lay of strands causes high internal stresses, especially at the crossover points.
• These stresses often lead to internal wire fractures which begin from the inside and progress outward.

Inspection Challenges and Safety Risks

One of the main concerns with rotation-resistant ropes is their failure mode:

• Internal damage is hard to detect because it often shows little or no signs on the rope’s exterior.
• These hidden fractures can result in sudden and catastrophic failure, posing serious safety risks in lifting operations.

This makes routine inspection and maintenance of such ropes far more complex and less reliable compared to standard wire rope constructions.

Impact of Bending and Sling Usage

Sling applications often involve tight bending radii and repeated mechanical stresses. Rotation-resistant ropes do not perform well under these conditions:

1) Tight bends further amplify internal stresses, accelerating wire breakage.

2) The formation of eyes or hitches can deteriorate the rope’s internal structure, reducing service life.

Such mechanical conditions undermine the structural integrity of rotation-resistant ropes, making them unsuitable for use in slings.

Safer Alternatives for Sling Fabrication

Due to these limitations, safer alternatives are recommended:

• 6×19 and 6×36 constructions are widely accepted for their flexibility and durability.
• These ropes offer better resistance to internal fatigue and allow for easier inspection and safer long-term use.

Choosing the right rope construction ensures not only regulatory compliance but also the safety and longevity of your lifting operations.

For further details on this research and its applications:

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