ASTM_D_2440_-_13.pdf

Designation:D244013Standard Test Method forOxidation Stability of Mineral Insulating Oil1This standard is issued under the fixed designation D2440;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method determines the resistance of mineraltransformer oils to oxidation under prescribed acceleratedaging conditions.Oxidation stability is measured by thepropensity of oils to form sludge and acid products duringoxidation.This test method is applicable to new oils,bothuninhibited and inhibited,but is not well defined for used orreclaimed oils.NOTE1A shorter duration oxidation test for evaluation of inhibitedoils is available in Test Method D2112.NOTE2For those interested in the measurement of volatile acidity,reference is made to IEC Method 61125.21.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3B1 Specification for Hard-Drawn Copper WireD664 Test Method for Acid Number of Petroleum Productsby Potentiometric TitrationD974 Test Method for Acid and Base Number by Color-Indicator TitrationD2112 Test Method for Oxidation Stability of InhibitedMineral Insulating Oil by Pressure VesselD2272 Test Method for Oxidation Stability of Steam Tur-bine Oils by Rotating Pressure VesselD3487 Specification for Mineral Insulating Oil Used inElectrical Apparatus2.2 IEC Publication:IEC 61125:1992 Unused HydrocarbonBased InsulatingLiquidsTest Methods for Evaluating the Oxidation Sta-bility43.Summary of Test Method3.1 Atest specimen of mineral transformer oil is oxidized ata bath temperature of 110C,in the presence of a coppercatalyst coil,by bubbling oxygen through duplicate test speci-mens for 72 and 164 h,respectively.The oil is evaluated at theend of each aging period by measuring the amount of sludgeand acid formed.The test specimen is diluted with n-heptaneand the solution filtered to remove the sludge.The sludge isdried and weighed.The sludge-free solution is titrated at roomtemperature with standard alcoholic base to the end pointindicated by the color change(green-brown)of the addedp-naphthol-benzein solution.4.Significance and Use4.1 The oxidation stability test of mineral transformer oils isa method for assessing the amount of sludge and acid productsformed in a transformer oil when the oil is tested underprescribed conditions.Good oxidation stability is necessary inorder to maximize the service life of the oil by minimizing theformation of sludge and acid.Oils that meet the requirementsspecified for this test in Specification D3487 tend to minimizeelectrical conduction,ensure acceptable heat transfer,andpreserve system life.There is no proven correlation betweenperformance in this test and performance in service,since thetest does not model the whole insulation system(oil,paper,enamel,wire).However,the test can be used as a control testfor evaluating oxidation inhibitors and to check the consistencyof oxidation stability of production oils.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-mittee D27.06 on Chemical Test.Current edition approved Feb.1,2013.Published March 2013.Originallyapproved in 1965 as D2440 65 T.Last previous edition approved in 2004 asD2440 99(2004).DOI:10.1520/D2440-13.2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D27-1001.ContactASTM CustomerService at serviceastm.org.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.4International Electrotechnical Commission.Available from American NationalStandards Institute,25 W.43rd St.,4th Floor,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Apparatus5.1 Aging(Oxidation)BathAn oil bath,wax bath,oraluminum block heater(see IEC Method 61125)of a suitabletype capable of controlling the temperature at 110 6 0.5Cwith a temperature gradient of less than 1C in the body of theliquid.When initially setting up the bath,a measurement of thetemperature gradient with the tubes immersed is to be con-ducted to e