Up to 2500 kVA, the transformer tanks are of the corrugated (finned) type. For higher powers, cold-rolled or laminated steel radiators are used. The radiators are individually tested before assembly.
If so indicated, the transformers are fitted with a standard conservator for hot oil expansion. Transformers up to 2500 kVA can be manufactured without conservator.
The internal walls of the tanks are sandblasted, and then protected using special hot-oil insoluble paints. The external walls are protected with water-soluble paint, RAL 7031 (in accordance with ENEL specifications) or RAL 7033 with 100-120 microns painting thickness and are suitable for use in the most severe environmental conditions.