Conservator. The oil should not be allowed to come in contact with atmospheric air as it may take up moisture which may spoil its insulating properties. Also air may cause acidity and sludging of oil. To prevent this, many transformers are provided with conservators. The function of a conservator (Fig. 14) is to take up contraction and expansion of oil without allowing it to come in contact with outside air. The conservator consists of an air tight metal-drum fixed above the level of the top of the tank and connected with it by a pipe. The main tank is completely filled with oil when cold. The conservator is partially filled with oil. So the oil surface in con tact with air is greatly reduced. The sludge thus formed remains in the conservator itself and does not go to the main tank.
Breather. When the temperature changes, the oil expands or contracts and there is a
displacement of air. When the transformer cools, the oil level goes down, and air is drawn in. This is known as breathing. The air, coming in, is passed through an apparatus called breather for the purpose of extracting moisture. The breather consists of a small vessel which contains a drying agent like silica get crystal impregnated with cobalt crystal.
Note. Sludging means the slow formation of solid hydrocarbons due to heating and oxidation. The sludge producing more sludge. This process may continue will the transformer becomes unusable due to overheating, This makes transformer still hotter producing more sludge. The process may continue till the transformer becomes unusable due to overheating. So the contact of oil with air should be avoided as the air contains oxygen.