What is this called and what used for?

Silica gel is used in transformers as a breather.

The silica gel breather is a pot of silica gel through which air passes during the breathing of the transformer.

The silica gel is a very good absorber of moisture. Silica gel breathers are put in the conservators of gas transformers by the majority of power-producing firms.

These silica gel breathers are built to withstand moisture from the air.

Power transformers require a method to account for changes in the volume of the insulating oil as it heats and cools.

As the transformer “breathes” from the expansion and contraction of the insulating oil, the silica gel dries (removes moisture) from the atmospheric air.

Moisture inside a transformer degrades the mineral oil’s insulating properties as well as the cellulose i…