SHRINKAGE

Shrinkage tests confirm if the materials, both the sheath and the insulation, do not shrink when they are in use. This prevents electrical faults such as electric shocks or short-circuits due to shrinkage that leaves active parts of the cables exposed.

Test methods

Shrinkage tests for insulation. UNE-EN 60811-502

The samples are prepared by separating all the coatings from the insulated conductors. These samples are tested horizontally in an air oven at the temperature and for the duration established in the specific product standard, while being supported by the bare conductors or a layer of talcum powder, although in all cases this permits free movement of the insulation when heat is applied.

Once the samples have cooled to ambient temperature after heat treatment, the difference in length measured before heating, L₁ and after heating L₂ is recorded. The test is satisfactory if shrinkage of the insulation is less than established in the specific product standard.

Shrinkage tests for sheaths. UNE-EN 60811-503

The test is carried out on a complete cable sample, applying periodical heat cycles at the temperature and duration established in the specific product standard.

At the end of the heat treatment, shrinkage is measured before, L₁, and after treatment, L₂. The performance of the samples is considered to be satisfactory if shrinkage is less than established in the specific product standard.