Total Acid Number(TAN) is a parameter to define the deterioration of lubricants. The more acidity lubricant oil contains, the worse quality lubricant oil is. In other words, the lubricant oil is degraded. In addition, once the lubricant oil has a large amount of acid number, it will be harm to equipment or machinery as the acidity will be corrosive to the metal. It will accelerate the wearing of equipment or machinery in sequence. Then, there will be much risks of failure of equipment or machinery.