Non-rotating Wire Ropes

PROlift® provide wire ropes to suit the requirements of your applications, including non-rotating wire ropes and special wire ropes.

Non-rotating (non-rotational) wire ropes are used in various on and offshore cranes, various machinery, winches and trolleys, in the maritime and fisheries sector, on and offshore oil exploitation, civil and industrial construction, engineering and infrastructure works, underground and surface mining, timber mining and numerous other industries and applications.

The most common constructions provided are shown below:

Rotational resistant and non-rotating properties of a wire rope increase with number of outer strands and number of layers of strands in section.

Thus, a wire rope with at least 14 outer strands and at least 3 layers is a very good non-rotating wire rope (see above rule for opposite lay’s direction of adjacent strands lays).
Wire ropes with 11-13 outer strands and 2 layers of strands have good non-rotating properties.
Wire ropes with 8-10 outer strands and 2 layers of strands have medium non-rotating properties.

Statistical, a non-rotating wire rope with 2 layers of strands and a free end, develop between 55% and 75% of minimum breaking load force, while a 3 layers strands develop between 95% and 100% of this force. This parameter is named spinning loss factor.

For tower cranes and other larger cranes, using non-rotating wire ropes with 3 layers strands it is recommended.

When loaded, every wire rope will develop torque; that is it has the tendency - to unravel itself unless both rope ends are secured against rotation. Both torque and rotation speed increase directly with load applied. Non-rotating wire ropes are designed so that the wire-rope outer rotational force naturally counteracts the inner strands rotational force in the event of a load applied.

Rather than all wires and strands being laid in the same direction, a rotation resistant wire rope consists of inner strands being laid in the opposite direction to the outer layers, for example the inner may be constructed in left hand lay whilst the outer layer is in right hand lay. This construction means that torsional forces on the inner and outer wires / strands will counteract each other and so minimise the risk of unraveling.

Using an ordinary lifting wire rope for a job or equipment which demand a non-rotating wire rope si very dangerous and it presents the following risks:

• violent twisting and even unravel during loads manoeuvring;
• spin the load, possible out of control;
• decrease of minimum breaking load;
• fatigue of wire rope and premature disposal;

All wire ropes rotate to a certain degree; by choosing the correct wire rope you can minimise this effect.

It is very important during replacing a non-rotating wire rope to know outer strands direction; the new wire rope will have the same outer strands direction and the same construction (diameter, strands, wires per strands, breaking load, lubrication, inner filling or protective coating ).