Politubes produces a wide range of tubes for the transformers industry:

• For oil-filled transformers we supply insulating spiral tubing for leads made by smooth or creped kraft paper which guarantees a larger impregnation surface, durability, flexibility and mechanical strength during assembly;
• For cast resin dry-type transformers we supply spiral tubing made of Mylar® or Nomex® used for insulating tie-rods when high temperatures are reached.

It is important to electrically insulate the tie rods that hold the sheet metal bundles together, so that no induced currents are generated within the tie rods.

Such currents can be induced by electrical fluxes produced by certain windings which, for example, do not fully interconnect with the other windings.

Some of the flux lines can, therefore, coil up through the air and reach the tie-rods, crossing them and generating a potential difference: this can constitute a serious risk to the proper functioning of the transformers themselves.

Politubes’ insulating spiral tubing are used precisely to ensure the correct insulation of the tie-rods and avoid this risk.

The advantages of spiral wound tubes over coiled tubes are:

1. Jamming or telescoping during insertion is avoided;
2. They can be supplied custom designed at lengths between 20 and 6000 mm, reducing wastes;
3. Increased durability;
4. Tubes are perfectly round without internal or external overlaps, ensuring uniform impregnation and insulation.

Tubes are supplied with an adequate wall thickness (between 0.3 and 3 mm) in order to guarantee the requested insulation and mechanical resistance.