What is strain relief?
Strain relief is a mechanical protection device that protects cables and hoses against mechanical stress. This device is particularly important when connecting flexible cables to an end piece such as a plug, connector or cable gland.
The strain relief ensures that any tensile, pressure, turning or bending forces that occur do not cause damage to the cable. For this purpose, the cable is fixed to a permanently installed object such as a cable gland. This prevents the cable from tearing out or kinking. This protection is therefore indispensable for moving applications.
How does strain relief work?
A cable duct with strain relief secures the cable in the cable gland or connector. The strain relief ensures that external forces do not continue to the other side, but are absorbed by the structure on which the strain relief is mounted.
Ideally, the forces at the contacts in the plug or in the cable inside the control cabinet are zero. No matter how the cable moves on the outside, it stays still inside. This saves the contacts and sensitive electronics.
Why do cables need strain relief at all?
Cables are often exposed to mechanical stress, either because they are pulled or because they are bent or constantly moved back and forth. The cable is then stretched over the outer radius and pulled out of the opening of the housing, the connector or the cable gland. On the inner radius, on the other hand, it is compressed and pushed in.
If the bending radius is very small, the cable can even kink. If the cable is inserted into a plug, this can lead to the cores being damaged or torn off from the contacts in the long term.
Strain relief is also used for cables that are not exposed to tensile and bending forces, for example in static electronic systems. By fastening the cables or cable bundles inside the housing, the cables also remain in the original position in which they were installed for a long period of time. During repair work on the system, this ensures that all cables remain at their intended connections and connectors.
Which industries and applications need strain relief?
The answer: all of them. Or nearly all of them, such as the Mechanical and plant engineering or the Food and beverage industry. Wherever cables are subjected to mechanical stress, whether it’s by pulling, bending or frequent movement, strain relief is essential.
But there isn’t a single solution that can do everything. It always depends on the intended use.
What should be kept in mind when it comes to strain relief?
Mobile electrical equipment, which also includes everyday work equipment such as extension cables or power cables, must have strain relief.
There is no “strain relief cable specification”, but the requirements for strain relief are described in Europe by the DIN EN 62444 standard and in the USA by the UL standard UL 514B.
The cross-section of the cable and the associated cable diameter play a crucial role here, as this has an impact on the required strain relief.