ASTM D2440 Oxidation Stability of Mineral Insulating Oils
Transformer oils dissipate heat and provide electrical insulation to protect transformer components. Oxidation of these oils may produce sludge and acid products, potentially decreasing the service life of the oil and increasing the chance of expensive equipment failure. This test is intended to predict how well new transformer oils will resist oxidation.
A copper catalyst is added to the sample, the mixture is heated and oxygen is bubbled through for a specified period of time. The oil is then filtered and the sludge is dried and weighed. The neutralization number of the filtered oil is determined. The report lists the weight percent of recovered sludge and the neutralization value in mg KOH /g oil. This test normally runs for 72 and/or 164 hours. Other times are available by request..