ASTM D2440 for oxidation stability of mineral insulating oil
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 the work of IEC Subcommittee 10A.

1.2 The values stated in metric units are to be regarded as the 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
2.1 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 Rotating Bomb
D2272 Test Method for Oxidation Stability of Steam Turbine Oils by Rotating Pressure Vessel
D3487 Specification for Mineral Insulating Oil Used in Electrical Apparatus

2.2 IEC Publication:
CEI/IFC 61125: 1992 Unused Hydrocarbon–Based Insulating Liquids - Test Methods for Evaluating the Oxidation Stability