The approximate acidity of used electrical insulating oils is an estimate of the total acid value of the oil. As acid values increase, oil quality decreases. This is usually due to oxidation of the oil while in service. In general, acidic by-products produce increased dielectric loss, increased corrosivity, and may cause thermal difficulties attributable to insoluble components called “sludge.” This test method is adapted to a specific volume of oil; total acid values of 0.05 to 0.5 mg of potassium hydroxide per gram of oil is a range which is functionally significant.

1.1 This test method describes the determination of the approximate total acid value of used electrical insulating liquids having viscosities less than 24 cSt at 40°C. It is a simple procedure that can be applied in the field. Where a quantitative neutralization value is required, use Test Method D664 or D974. These test methods should be applied in the laboratory.

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.