Rotation resistant wire ropes are a series of steel ropes that were built specifically to not spin or rotate under a load. These ropes are designed to resist spinning by putting layers of wire rope spun in one direction, while the outer layers are spun in the opposite direction. The more layers there are, the less likely it will rotate.
When to Use Rotation Resistant Wire Rope
When lifting a load, wire ropes are used in instances when rotation resistance is necessary for its ability to stabilize the load. Rotation resistant wire rope is used when it is impractical or impossible to:
- Implement a tag line
- Locate the dead-end of a rope
- Increase sizes of sheaves
- Eradicate “odd-part” reeving
- Significantly reduce rope fall length
- Fundamentally reduce rope loading
The rotational force of the outer strands is counteracted by the rotational force of the inner strands, Conventional wire ropes that have more of a tendency to unlay than rotation-resistant wire ropes so the rotation resistant ropes are used to improve rotational stability in the lifted load. These ropes were created so that when they are carrying a load, the rotational force of the outer strands is counteracted by the force of the inner strands to resist rotation. The stability of conventional ropes doesn’t even come close to the stability of rotation-resistant ropes on both long and shortfalls.
Safety Design Factors
To maintain a low rotation of the wire rope, and eliminate the tendency to overload the inner core, it is essential to choose the wire rope with the correct strength design factor. ASME B30.5 specifies that rotation-resistant ropes have a rotation factor of five or greater. Anything less would cause a reduction in rope strength.
Handling and Installation
When using a rotation-resistant wire rope, it is necessary to take the following precautions:
- To prevent unlaying of strands, you must properly seize rope ends
- To prevent unlaying of rope or kinking, you must attach end fittings carefully so as not to harm the rotational balance of the rope
- To prevent distortion of the rope structure, such as bird caging or core protrusion, you need to avoid shock loading. Shock loaded wire ropes must immediately be removed from service because of the potential for complete rope failure.
- A swivel may be used temporarily during the initial installation, only to assist eliminating installation-induced cabling or twisting, however; it is not recommended to use a swivel with 8×25, 19×7 and SPF 19 rotation resistant wire ropes.
- The inner core will twist tighter with the use of a swivel which severely reduces the rope strength. This could result in early rope failure.
- Before the crane begins operation, the swivel must be removed from the reeving after completing the rope installation.
- Always check with the manufacturer, as some rotation resistant ropes may be used with a swivel.
If you require wire resistant ropes, we can help you here at Silver State Wire Rope and Rigging. We have all of your rigging needs and a wide array of wire ropes to choose from, including rotation resistant wire ropes. Contact us and let us help you find what you need.