Transformer with conservator tank is the same as hermetic transformers with core and coil structure. The dimensions of the conservator tanks of this type of transformers are designed and manufactured as a result of calculations to store the conservator of the oil whose volume increases with temperature.

Since the transformers with conservator tanks are open to the atmosphere, the oil pressure is changed due to thermal effects, and the air exchange is ensured by taking the moisture of the air through the silicagel (air dryer) in the transformer tank. As a result of the air exchange due to the temperature differences after usage, the transformer with the working conservator tank loses its silicagel properties over time and causes the humidification of the oil and its structure.