Strain Relief
The transfer of the pulling, bending and vibration forces on a cable to a clamp, a gland or a sheath rather than to the terminal. The aim is that the mechanical load never reaches the electrical contact point. Applied correctly, when the cable is pulled it is the clamp that is stressed, not the connection.
Electrical connection points are not designed to carry mechanical load. Continuous pulling on a terminal fatigues the wires under the crimp, cracks the solder joint and backs the pin out of its housing.
- Forms of application: the clamping nut of the cable gland at the enclosure entry, the cable clamp behind the connector, a tie inside the enclosure fixing the cable to the body.
- Service slack: leave a little slack between the terminal and the first fixing point; this allowance both absorbs vibration and makes disassembly easier at the next maintenance.
- Bending radius: do not force the cable into a sharp turn right after the entry; do not go below the minimum bending radius given by the manufacturer.
- Check: after installation pull the cable gently by hand; the movement must stop at the clamp, not at the terminal.
Because vibration is continuous on vehicle-mounted installations, strain relief is not an optional detail. Choosing the gland at the enclosure entries to suit the cable diameter provides both sealing and strain relief together.
The context in which this term is used: Installation, redundancy and field continuity