Heat-Shrink Tubing
Heat-shrink tubing is an insulating sleeve that wraps a cable by shrinking in diameter by a certain ratio when heated. It is sold with shrink ratios such as 2:1 and 3:1. Types with an adhesive-lined inner surface also form a moisture barrier as the glue melts and bonds to the cable sheath during shrinking.
Sleeving has two different jobs and the type is chosen accordingly. The standard type gives only electrical insulation and mechanical support; the adhesive-lined type also closes the joint against water. Outdoors and on vehicles the latter is preferred.
- Size: the diameter before shrinking must pass over the cable easily and the diameter after shrinking must be smaller than the cable; otherwise the sleeve does not wrap tightly.
- Heat source: use a hot air gun. A lighter flame burns and carbonises the sheath.
- Application: start in the middle and work towards the ends; this is how trapped air is avoided.
- Support function: sleeving fitted behind a soldered or crimped end spreads the bending stress to some extent.
You can also use sleeving for cable labelling: writing the circuit number on the writable type and slipping it over the ends is a far more durable solution than a taped label for maintenance years later.
The context in which this term is used: Installation, redundancy and field continuity