Why do cables fail?March 04, 2020
Six common causes of cable failure
There are many ways a cable can fail, especially in continuous-flex applications, and it can be helpful for designers and engineers to understand how and why failures happen. Below are six of the main causes of cable failure with a few expert tips on how to prevent them.
This failure is easily recognizable by the mechanical deformation of the entire cable. Corkscrewing occurs when torsional forces are released during operation due to incorrect cable configuration, pitch length and pitch direction. It can also be caused by improper installation.
An easy way to prevent corkscrewing is to utilize cables that have a bundled design rather than layered conductors. These bundled types of cables are very difficult, if not impossible, to corkscrew thanks to the equal stress on the shorter conductor pitch.
2. Loss of continuity
Copper conductors can sever and break when insulated conductors are twisted with an incorrect pitch length or pitch direction, causing loss of continuity. The cable core cannot absorb the mechanical load while flexing so it transfers the force to the copper conductors, which causes them to break under the increased tensile load.
3. Insulation damage
Insulation damage occurs when the insulation integrity of the conductors is compromised. This is caused by material fatigue under constant bending stress, abrasion within the cable structure, and/or conductor strand breakage. All of which can perforate the insulation.
4. Jacket abrasion
Jacket abrasion occurs when the outer jacket of a cable wears through to the underlying layer of conductors or shielding. This failure is especially common when using cables with soft jackets. However, this problem can also be caused by a thin wall-thickness which can develop during the jacket extrusion process.
Using jacket materials that are rated for use together and with cable carriers can help reduce or eliminate jacket abrasion.
5. Jacket swelling/cracking
The outer jacket of a cable swells when it has been exposed to oils or chemicals it was not designed to withstand. Jacket cracking occurs when the jacket breaks and deteriorates down to the cable’s shield, normally as a result of excessively high or low temperatures.
Using jacket materials tested and rated for temperature extremes can help this, or at least postpone damage occurred.
6. Shielding losses/EMC problems
Increased electromagnetic interference (EMI) occurs when the shield, which is designed to protect cable signals from electromagnetic fields, breaks and abrades due to continuous bending.
For more videos on how to avoid cable failure, visit the videos section of our Engineer's Toolbox.