Self-limiting heating cables



varying output depending on the ambient temperature, which guard against overheating even if the cables crosses themselves. This also allows installation in Ex-surfaces (all VärmeKabelTekniks self-limiting heating cable types are Ex-rated).

The self-limiting cable have a unique capacity in proportion to the sheath temperature of the cable, reduce the emitted output. These cables are often mentioned as self-limiting cables but this is a wrong denomination, as a required temperature not can be guaranteed without temperature control.

On the other hand, the cables make it possible to give an even temperature on a pipe even if the ambient temperature varies along piping.

Värmekabeltekniks self-limiting cables are approved within Ex-range when the cables have a stated T-Rate, i.e. a maximum temperature that the cable reach. The T-rates varies for different output/m.

The self-limiting cables are built-up round a semi-conductive bed embedded in the outer edges. The bed between the conductors has a capacity to lead current, the conducting capacity is in proportion to the temperature. At rising temperature the conducting capacity decreases, overheating is prevented. At sinking temperature, the current increases and the increasing heat requirement is satisfied.

  • SRL Frost protection cables has a primary insulation and outer sheath of thermoplastic rubber. Are also available with outer sheath of teflon for aggressive environments.
  • SRM cables to keeping warm and heating, has an insulation and outer sheath of teflon.

The emitted output of the self-limiting cables are depending on the ambient temperature and the method of installation, a good dissipation of heat increase the emitted output. (Aluminium tape that covers all the length of the cable and is attached against the pipe, cool down the side of the cable, which borders against the insulation and thereby, emitted output with 30-50%).

All self-limiting cables have a starting current which is higher than the operating current. This must be taken into consideration when designing circuit/connection lengths, (see data sheet).