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    ASTM D2440 - 13

    Standard Test Method for Oxidation Stability of Mineral Insulating Oil

    Active Standard ASTM D2440 | Developed by Subcommittee: D27.06

    Book of Standards Volume: 10.03

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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. Scope

    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 1—A shorter duration oxidation test for evaluation of inhibited oils is available in Test Method D2112.
    Note 2—For 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.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    B1 Specification for Hard-Drawn Copper Wire

    D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration

    D974 Test Method for Acid and Base Number by Color-Indicator Titration

    D2112 Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure Vessel

    D2272 Test Method for Oxidation Stability of Steam Turbine Oils by Rotating Pressure Vessel

    D3487 Specification for Mineral Insulating Oil Used in Electrical Apparatus

    IEC Publication

    IEC 61125: 1992 Unused Hydrocarbon-Based Insulating Liquids--Test Methods for Evaluating the Oxidation Stability International Electrotechnical Commission. Available from American National Standards Institute, 25 W. 43rd St., 4th Floor, New York, NY 10036.

    ICS Code

    ICS Number Code 29.040.10 (Insulating oils)

    UNSPSC Code

    UNSPSC Code 15121505(Transformer oil or insulating oil)

    Referencing This Standard
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    DOI: 10.1520/D2440-13

    Citation Format

    ASTM D2440-13, Standard Test Method for Oxidation Stability of Mineral Insulating Oil, ASTM International, West Conshohocken, PA, 2013, www.astm.org

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