Rising oil temperature The first step is to raise oil temperature up to 65°C to give latent heat which separates moisture and gases. Heating the oil will make it easier to filter because of the decrease in oil viscosity. Removal of dirt and impurities The second step is to remove sludge and dirt from the insulating oil. There are 2 ways to eliminate dirt in the transformer oil. By filter candles Insulating oil filtration by filter candles can be classified by using a classical edge filter or depth type filter. However, new advancements were made in which transformer oil filtration machines use filter cartridges instead of edge type paper filters. By centrifuging action Another method for separating dirt from oil is through centrifuging. With this process, you can save the recurring cost of changing filters. Dehydration and degasification of insulating oil This is the stage of dehumidification of insulating oil and removal of gasses. This process is completed in the transformer Oil Dehydration Machine.