Importance of Knowing the Recommended Minimum Bend Radius for Cable
Posted on 9/9/19 7:24 AM
Cable is made up of different components which all need to work together to be effective in whatever product it is a part of, such as a power cord or cord set. If one of the components within the cable becomes damaged in some way, it can directly affect the product. That is why it is important to know the recommended minimum bend radius for the cable being used.
A key factor with cable is knowing what the recommended minimum bend radius is—how much it can be bent without causing damage—because if it exceeds the suggested number impairment can be caused, potentially resulting in compromised cable, shock, or even fire. There are various cable standards, such as the National Electrical Code Handbook (NEC) and HD 516, which give minimum bend radius requirements.
Dan Ford, Technical Support Specialist at Interpower®, explained that if cable exceeds the minimum bend radius repeatedly, some of the problems that can result include cracked insulation, broken conductors, and/or tears in the jacket or conductor wires. Part of it depends on the material of the jacket. If it is a harder material, it may not survive an 8 radius, but possibly a 12. The harder the material, the easier it can result in damage because it is not as flexible.
“It is important to avoid unnecessarily damaging the cable which can shorten its life, potentially leading to shock or fire,” Dan said. “The end use of the cable plays a big role in what the actual bend radius will be—it depends how it will be used. For example, if the cord is plugged into the wall and then jerked on from the side to get it out, that will violate the bend radius. If the cord is twisted a lot, that also will affect it.”
Dan gave this analogy as a comparison: When a garden hose is bent too tight, it kinks and blocks the flow of water. The same with cable that is bent more than it should be—the result can be damaged cable that won’t transmit power. “Bend radius failures usually happen over time and eventually will not work,” he said. “However, instant failure can occur if the wire in the cable is broken by jerking on the cord, especially at sharp angles.”
Determining Minimum Bend Radius
Figuring out how far a cable can bend without causing permanent damage to it depends on the type and diameter of the cable. The outer diameter of the cable times the cable multiplier equals the minimum bend radius. Cable multipliers vary according to the type of cable and per industry standards.
“It depends on the size of cable and the material—some types bend better than others,” Dan said. “Different jacket materials offer varying degrees of flexibility. Fillers or shielding inside the cable will reduce a cable’s ability to bend as far. Finer stranding size in the conductors will allow for more flexibility than larger stranding sizes.”
Cable manufacturers will typically issue recommendations for minimum bend radius that are rather conservative to cover a wide range of applications, due to the fact that the end application and stresses are typically not known. Therefore, if a manufacturer wants to use a cable at a smaller bend radius recommendation, it is advised they seek guidance from the manufacturer of the cable.
Indicators of Bend Radius Failures
Some indicators of bend radius failures include:
- Discoloration of the cable could occur
- Wrinkling, pinching, or kinking of the cable
- Stress tears on the cable jacket
- Increased resistance of the cable with the meter (a high resistance rating can indicate a previously damaged cable)
The important factor to remember is that the purpose of minimum bend radius is to protect the cable so that it does not become damaged. For questions, please contact Customer Service at Interpower.
For more information on specifications regarding cable offered by Interpower, see the Cable product line. Most cable part numbers found on the Interpower website include the minimum bend radius in the specifications.