Standard Historical Last Updated: Nov 19, 2021 Track Document
ASTM D2440-13

Standard Test Method for Oxidation Stability of Mineral Insulating Oil

Standard Test Method for Oxidation Stability of Mineral Insulating Oil
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Significance and Use

4.1 The oxidation stability test of mineral transformer oils is a method for assessing the amount of sludge and acid products formed in a transformer oil when the oil is tested under prescribed conditions. Good oxidation stability is necessary in order to maximize the service life of the oil by minimizing the formation of sludge and acid. Oils that meet the requirements specified for this test in Specification D3487 tend to minimize electrical conduction, ensure acceptable heat transfer, and preserve system life. There is no proven correlation between performance in this test and performance in service, since the test does not model the whole insulation system (oil, paper, enamel, wire). However, the test can be used as a control test for evaluating oxidation inhibitors and to check the consistency of oxidation stability of production oils.


1.1 This test method determines the resistance of mineral transformer oils to oxidation under prescribed accelerated aging conditions. Oxidation stability is measured by the propensity of oils to form sludge and acid products during oxidation. This test method is applicable to new oils, both uninhibited and inhibited, but is not well defined for used or reclaimed oils.

Note 1A shorter duration oxidation test for evaluation of inhibited oils is available in Test Method D2112.
Note 2For those interested in the measurement of volatile acidity, reference is made to IEC Method 61125. 2

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 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.

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Book of Standards Volume: 10.03
Developed by Subcommittee: D27.06
Pages: 5
DOI: 10.1520/D2440-13
ICS Code: 29.040.10