Strain relief

The essential protection for every cable

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 conduit 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 connector or in the cable inside the control cabinet are zero. No matter how the cable moves on the outside, it stays still inside. This protects 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 connector, this can lead to the conductors 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.

1- Cable diameter 2- Bending radius 3- Outer radius 4- Inner radius 5- Stretched or elongated jacket at outer radius 6- Compressed jacket on inner radius

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 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.

More about the food industry
Strain relief in the food industry

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.

What types of strain relief does LAPP offer?

Cable ties secure cables or cable bundles to sockets and provide basic protection against cables that aren’t moved from being pulled out, for instance in a control cabinet. The LAPP portfolio includes Basic Tie cable ties and TY - FAST® cable ties.
If cables need to move, more complex solutions are needed. One is SKINTOP® GRIP, a brass cable conduit available in the variants up to M 32x1.5. It’s equipped with a double lever that provides ten times higher strain relief than the standard. This cable duct is primarily intended for use in machine and system parts that are moved, such as foot switches and push-button control units.

Cable sleeves are installed in gaps and are used to feed through cables. For example, the SKINDICHT® DTN enables cables with a diameter of up to 32 mm (1.248 in) to be inserted.

A real innovation is SKINTOP® MULTI, a practical cable multi-entry for control cabinets and automation technology. In the space-saving multi-bushing, you can simply feed up to 30 unassembled round cables with different diameters and AS-I cables through an elastic gel membrane. The gel seals firmly around the cable insulation over a wide clamping range and hermetically seals the opening, while also acting as the optimum strain relief for the entire cable bundle.

Cable clamps secure a cable to protect it from being torn off. LAPP offers metal cable clamps, such as the SILVYN® BW-M, or plastic cable clamps, such as the SILVYN® BW-K-M.
Protective cable conduits can be strain-relieved using the SILVYN® conduit connector. Numerous types are also available in the HYGIENIC variant for the food industry.
Strain relief is also an important topic in cable chains. The ÖLFLEX® CONNECT CHAIN range includes fully equipped cable chains in which the assembled cables are optimally strain relieved in the factory. The configuration is simplified by the ÖLFLEX® CONNECT CHAIN configurator, where a cable chain can be engineered with just a few mouse clicks.