In Episode 25 of No Dumb Questions, we break down the primary mechanisms behind cable failures in real-world applications and outline how custom engineering prevents them. Cable failures typically stem from harsh environmental exposure, mechanical fatigue, or insufficient cable design.
We examine the three most common failure modes:
- Loss of Continuity & Resistance Spikes: Repetitive bending and axial tensile pulling fatigue the internal conductors. Over time, micro-fractures increase conductor resistance or cause complete structural breaks, halting power and signal flow. Prevention strategies include using high-tensile copper alloys, optimizing internal lay lengths to limit internal friction, and incorporating aramid fiber (Kevlar) strength members to absorb axial pulling loads.
- Insulation Breakdown & Short Circuits: Exposure to environmental factors (UV radiation, moisture) combined with mechanical abuse (abrasion, impact, rolling cart crush) degrades outer jackets and primary insulation. When conductor insulation is breached, current escapes, causing short circuits, equipment damage, or fire hazards. Prevention relies on selecting durable jacketing materials (such as polyurethane for abrasion/cut-through resistance or silicone/fluoropolymers for high temperatures) and strictly maintaining minimum bend radius rules (5x OD for static installations; 10x OD for dynamic flexing).
- Loss of Shielding & EMI Ingress: Continuous cyclic flexing forces the woven strands of braided shields to abrade against one another, eventually severing individual wires. As the shield breaks open, electromagnetic interference (EMI) penetrates the cable, corrupting data transmission, video feeds, or audio signals. Prevention involves using heavier-gauge braid strands, combining braided shields with aluminum mylar tapes, and applying inner barrier wraps to protect shields from internal abrasion.
Key Technical Takeaways
- Loss of Continuity: Caused by cyclic flexing and tensile load fatigue; prevented using high-tensile alloy conductors, controlled lay lengths, and aramid (Kevlar) strength members.
- Insulation Failure: Triggered by mechanical impact, crushing, abrasion, UV exposure, and thermal degradation; leads to short circuits and fire hazards.
- Material Countermeasures: Polyurethane provides high cut-through and abrasion resistance; silicone and fluoropolymers withstand extreme operating temperatures.
- Bend Radius Rules: Prevent mechanical fatigue by maintaining a minimum bend radius of 5x OD for static installations and 10x OD for dynamic flex cycles.
- Shielding Degradation: Continuous flexing causes braid wires to saw into each other; prevented using heavier-gauge strands, hybrid foil-braid shielding, and protective barrier tapes.
Next up, Episode 26: What is UL and CSA?
Episode 25 Transcript – Common Cable Failures and How to Prevent Them
Welcome to No Dumb Questions
Hello, and welcome to our video series No Dumb Questions, where the only dumb question is the question you do not ask. Today we’re going to be talking about an issue that everybody should have some knowledge of. Our topic today is common cable failures and how to prevent them.
Cable failures occur for a number of reasons. Typically it’s a result of the environment that the cable is being installed into or the application for which the cable is being used. Sometimes it’s a result of poor cable design. We’re going to talk about how we can design the cable to prevent issues.
Failure Mode 1: Loss of Continuity & Rising Resistance
One of the most common types of cable failures is a loss of continuity. Loss of continuity can occur because the copper or other conductors in the cable receive stress as the cable is being used. So as we continuously flex a cable, or as we apply tensile strength from use between a device or handpiece, we can cause stress to build up in the individual components of the cable, and over time, that stress can compound and lead to a loss of continuity, or break in the conductor. I can demonstrate with this cable—that would be a serious loss of continuity. This means that the signal or the electricity can no longer transfer through the cable.
Other issues that are similar to continuity are a rise in resistance, where we’re actually stretching the conductor through cyclic flexing. And that rise in resistance can also lead to similar issues, such as loss of continuity.
Prevention: Alloys, Lay Lengths, and Strength Members
How do we prevent the issue from loss of continuity from occurring? One thing we can do is use alloy conductors, which can receive higher tensile strength or can survive longer flexing. The other thing we can do is make sure that the cable is appropriately designed with proper lay lengths and proper cabling layups. We want the cable to have a good structure, meaning that the cable components are not moving around too much in the cable, abrading one another and damaging the components.
Another thing we can do is consider the use of strength members. Strength members allow us to put increased tensile strength on the cable. Typically, we’re going to use an aramid or a Kevlar fiber for this. Tensile strength in the axis of the cable can be opposed by using strength members.
Failure Mode 2: Insulation Damage & Short Circuits
Another type of common cable failure that can occur is damage to the cable insulation. Damage to the cable insulation typically occurs because of the environment for which the cable is being used. Such as an environment where the cable is being exposed to cyclic UV radiation from sunlight, or from exposure to moisture. Mechanical stresses such as impact to the cable or abrasion to the cable—sometimes we may have gurneys or vehicles that run over the cable—and cause impact to the insulation. Over time, these stresses can build up in the cable and lead to a failure of the actual insulation.
When the failure of the insulation occurs, the current that’s inside of the cable can no longer be contained. This is especially bad when the primary insulation of the conductors is compromised. This means that we can have a short circuit in the cable from the undesired current, or from the current being in undesired locations, which can lead to sparking or even a fire in serious situations.
Prevention: Jacket Selection & Bend Radius Rules
We need to consider this in the cable design. One of the ways that we can make the cable more robust is using insulation that’s designed for the application for where the cable is being used. Polyurethane, for instance, has very good cut-through resistance and abrasion resistance. This tough material is good for outdoor applications or applications where serious mechanical stress can impact the cable.
You may also want to consider the temperature of the environment for the cable being used. If we’re using a cable in a high-temperature environment, we’re going to want a high-temperature material such as silicone rubber or fluoropolymer. That way, the temperature doesn’t break down the material over time.
Another thing we can do is consider the bend radius for the application. Is the cable being installed in a very tight configuration, a fixed configuration, i.e., static bending? For static bending, New England Wire recommends a five times (5x OD) bend radius. For dynamic flexing, which is continuous, NEWT recommends a ten times (10x OD) bend radius.
Failure Mode 3: Shielding Failure & EMI Degradation
The final cable failure mode that we’ll talk about today is loss of shielding. Shielding is used in a cable, often to prevent electromagnetic interference. It’s typically in a weaved pattern that we call a braid. We also incorporate the use of spiral shields or aluminum mylar tapes.
When we repeatedly flex the cable over time, this weave structure can lead to actual breaks in the braid, because the individual wires are abrading one another, and eventually, over time, will cut through one another. So continuous flexing can lead to a break in the shield that looks like this. This kind of damage is a problem for the cable, because it means that electromagnetic interference can interfere with the signal quality or the data transmission of the cable. That means that your camera image or your sound is going to be subpar for a robust shield.
Prevention: Shield Gauges, Hybrid Layers & Barrier Tapes
So how can we prevent issues with the shielding? One of the things we can do is consider the material that’s being used, or the individual gauge size of the wires being used. A heavier gauge wire is going to typically last longer than a smaller gauge wire, in terms of the braided shield.
The other thing we can do is incorporate the use of multiple types of shields. We can use an aluminum mylar tape over a braided shield to help give the shield robustness and provide it with a longer flex-life over time. The combination of both of those shields yields a lot better electromagnetic resistance.
The other thing we can do is use barrier tapes to prevent components inside of the cable from damaging the outer components, such as the shield. We can also use these barrier wraps to prevent cut-through when terminating or assembling the cable for the end device. And again, as with loss of continuity or with damage to the insulation, we want to consider the layup or the actual configuration of the components in the cable. Again, to reduce movement and increase the cable flex-life.
Thank you for joining us for another one of New England Wire’s No Dumb Questions. If you have any questions, please feel free to reach out to us.