REDwire How to avoid wire rope bending fatigue

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Bergen Cable Technology LLC

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Wire rope is designed to handle bending.

Bergen Cable Technology has a reputation for producing reliable wire rope products. But even when wire ropes come from an expert manufacturer like Bergen, there are still important factors to keep in mind to ensure they last as long as possible. 

Cause and effect

Wire rope is designed to handle bending, because unless it is being used as a guy or support, all wire ropes are subjected to bending around drums or sheaves. But if the size of those components is not properly chosen, or the location of the sheaves and drums not properly selected, the result will be premature fatigue and loss of strength.

As wire rope is bent, the individual wires and strands must slide upon one another. For this reason, it’s essential that wire rope is properly lubricated and that drums and sheaves are properly sized. If the strands and wires are not able to adjust to their changed position, the wire rope will lose strength. Repeated flexing then leads to the development of points of stress concentration.

The appearance of small cracks at over-stressed points is a symptom of the fatigue effect. As the wire rope is repeatedly bent, the cracks spread until the only metal still intact is not enough to handle the bending load.  

How to avoid fatigue

The larger the diameter of sheaves or drums, the less likely they are to prematurely fatigue wire ropes. There are many factors that affect the service life of wire ropes, so it is impossible to give an absolute minimum size. Some of the factors include the weight of the load and the speed of bending.  

As an example, when dealing with fast moving and heavily loaded ropes, it is recommended that sheaves and drums have diameters 800 times the size of the rope’s outer wires. 

Get help from the experts

Bergen Cable Technology has more than 60 years of experience in the design and manufacture of wire ropes, cables and cable assemblies. Its expert staff works with customers to design the best solution for their application. Contact Bergen Cable for assistance.

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