We often notice a transparent glass cylinder filled with blue granules attached to the conservator tank of oil-immersed transformers. These granules are Silica Gel, a chemical substance that plays a pivotal role in preserving the lifespan and efficiency of the transformer.
A transformer 'breathes' during operation; as the load increases, the oil heats up and expands, expelling air from the conservator tank. When the oil cools, it contracts and draws air from the outside in. The problem is that outside air contains moisture, and the entry of this moisture into the oil dramatically reduces its insulating efficiency, exposing the windings to electrical breakdown.
This is where the silica gel breather intervenes. These granules absorb all the moisture from the incoming air so that only completely dry air reaches the oil. Silica gel granules are dark blue when they are dry and effective. Over time, as they absorb moisture, their color gradually changes to pink or pale white.
Therefore, continuous visual monitoring of the silica gel color is imperative. Once it turns pink, it must be replaced immediately or reactivated (by heating to vaporize the moisture) to maintain oil quality and thus prolong the transformer's operational life.