Rotation resistant wire ropes

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What is a rotation-resistant wire rope?

In a conventional rope, an external load creates a moment which tries to untwist the rope and to rotate the load.

A rotation-resistant wire rope has a steel core which is an independent rope, closed in the opposite direction to the outer strands. Under load, the core tries to twist the rope in one direction, the outer strands try to twist it in the opposite direction.

The geometrical design of a rotation-resistant wire rope is such that the moments in the core and the outer strands compensate each other over a wide load-spectrum, so that even with great lifting heights no rope twist occurs.

Rotation-resistant or not?

Single leg wire rope sling

The use of rotation-resistant ropes is mandatory for the lifting of unguided loads with a single leg wire rope sling.

Multiple legs wire rope sling

Non rotation-resistant wire ropes with multiple legs achieve a higher service life than rotation-resistant ropes under identical conditions. Providing there are no other special conditions that require the use of rotation-resistant wire ropes, non rotation-resistant wire ropes should be used in multiple legs conditions.

Under certain conditions there is a danger that the legs could intertwine whilst under load. This is most likely with great lifting heights, narrow hook blocks, or under the influence of additional moments created by wind or the slewing of the crane. In such cases, rotation-resistant wire ropes or pairs of left and right hand lay wire ropes should be used.

Other conditions could also require a rotation-resistant wire rope.

Good to know

Rotation-resistant ropes should be used with a swivel, if possible. Non rotation-resistant ropes may not be used with a swivel.

If a crane has been supplied with a rotation-resistant wire rope by its manufacturer, then subsequent replacements should always be made with rotation-resistant wire ropes.