1、Designation: D2440 99 (Reapproved 2004)D2440 13Standard 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 yea
2、r 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 Department of Defense.1. Scope1.1 This test method determines the
3、resistance of mineral transformer oils to oxidation under prescribed accelerated agingconditions. Oxidation stability is measured by the propensity of oils to form sludge and acid products during oxidation. This testmethod is applicable to new oils, both uninhibited and inhibited, but is not well de
4、fined 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 the work of IEC Subcommittee 10A. IEC Method 61125. 21.2 The values stat
5、ed in metricSI units are to be regarded as the standard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate
6、 safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3B1 Specification for Hard-Drawn Copper WireD664 Test Method for Acid Number of Petroleum Products by Potentiometric TitrationD974 Test Method for Acid and Bas
7、e Number by Color-Indicator TitrationD2112 Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure VesselD2272 Test Method for Oxidation Stability of Steam Turbine Oils by Rotating Pressure VesselD3487 Specification for Mineral Insulating Oil Used in Electrical Apparatus2
8、.2 IEC Publication:CEI/IFCIEC 61125: 1992 Unused HydrocarbonBased Insulating LiquidsTest Methods for Evaluating the OxidationStability43. Summary of Test Method3.1 A test specimen of mineral transformer oil is oxidized at a bath temperature of 110C, in the presence of a copper catalystcoil, by bubbl
9、ing oxygen through duplicate test specimens for 72 and 164 h, respectively. The oil is evaluated at the end of eachaging period by measuring the amount of sludge and acid formed. The test specimen is diluted with n-heptane and the solutionfiltered to remove the sludge. The sludge is dried and weighe
10、d. The sludge-free solution is titrated at room temperature withstandard alcoholic base to the end point indicated by the color change (green-brown) of the added p-naphthol-benzein solution.4. Significance and Use4.1 The oxidation stability test of mineral transformer oils is a method for assessing
11、the amount of sludge and acid productsformed in a transformer oil when the oil is tested under prescribed conditions. Good oxidation stability is necessary in order to1 This test method is under the jurisdiction of ASTM Committee D27 on Electrical Insulating Liquids and Gasesand is the direct respon
12、sibility of Subcommittee D27.06on Chemical Test.Current edition approved Oct. 1, 2004Feb. 1, 2013. Published November 2004March 2013. Originally approved in 1965 as D2440 65 T. Last previous edition approvedin 19992004 as D2440 99.D2440 99(2004). DOI: 10.1520/D2440-99R04.10.1520/D2440-13.2 ASTM Rese
13、arch Report No. Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D27-1001,available from ASTM Headquarters, 100 Barr Harbor Drive, West Conshohocken, PA 19428 Contact ASTM Customer Service at serviceastm.org.3 For referencedASTM
14、standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 International Electrotechnical Commission. Available from American National Stan
15、dards Institute, 25 W. 43rd St., 4th Floor, New York, NY 10036.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all c
16、hanges accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
17、 United States1maximize the service life of the oil by minimizing the formation of sludge and acid. Oils that meet the requirements specified forthis test in Specification D3487 tend to minimize electrical conduction, ensure acceptable heat transfer, and preserve system life.There is no proven corre
18、lation between performance in this test and performance in service, since the test does not model the wholeinsulation system (oil, paper, enamel, wire). However, the test can be used as a control test for evaluating oxidation inhibitors andto check the consistency of oxidation stability of productio
19、n oils.5. Apparatus5.1 Aging (Oxidation) BathAn oil bath, wax bath, or aluminum block heater (see IEC StandardMethod 61125) of a suitabletype capable of controlling the temperature at 110 6 0.5C with a temperature gradient of less than 1C in the body of the liquid.When initially setting up the bath,
20、 a measurement of the temperature gradient with the tubes immersed is to be conducted to ensurethat no temperature gradient exists as the tubes may obstruct a uniform circulation. Use any nontoxic liquid having low volatilityat 110C and containing no volatile additives and having a flash point above
21、 the test temperature. Mineral oils, waxes and siliconeoils have been used satisfactorily. Circulation of the oil or wax heating medium by means of a pump or stirrer isrecommended.required. See also 5.4, relating to the depth of fluid in aging bath and position of oil receptacles.5.2 Drying TowerA d
22、rying tower 25 to 30 cm in height, fitted with a ground-glass stopper and side tubes at least 25 cm inlength for conditioning of the oxygen supply.5.3 Oil Receptacle and HeadAn oil receptacle consisting of a heat-resistant glass test tube 25 mm in outside diameter, 1.25mm in wall thickness, 210 mm i
23、n overall length including a standard taper 24/40 outer joint, with a Dreschsel-type head consistingof a standard taper 24/40 inner joint with side outlet tube 5.0 mm in outside diameter and an oxygen delivery tube 5.0 mm inoutside diameter and 3 mm, minimum, in inside diameter which extends to with
24、in 2.5 6 0.5 mm of the bottom of the oil receptacleand has its end ground at an angle of 30 to the axis of the tube. The design is shown in Fig. 1.5.4 Position the oil receptacle in the aging bath in accordance with the drawing shown in Fig. 2.NOTE 3The oil receptacle and position in the aging bath
25、are essentially the same as specified in IEC StandardMethod 61125, “Test Method forOxidation Stability of Inhibited Mineral Insulating Oils,” Glassware dimensions have been altered slightly to conform to sizes readily available in theUnited States. Both types of tubes can be used.5.5 Glass or Porcel
26、ain Crucibles50 mL size.5.6 Filtering CruciblesMembranesA glass filter crucible having a maximum diameter of the pores between 5 and 15 mas determined in accordance with the method described in the Appendix. Cellulose ester type membrane filters of 5-m porosityhave been used successfully also. poros
27、ity, 47 mm.FIG. 1 Oil Receptacle and HeadD2440 1326. Reagents and Materials6.1 Purity of ReagentsUse reagent grade chemicals in all tests. Unless otherwise indicated, all reagents are to conform to thespecifications of the Committee on Analytical Reagents of the American Chemical Society, where such
28、 specifications areavailable. 56.2 Chloroform, cp, or acetone, cp.6.3 n-Heptane, for dilution of the oxidized oil, precipitation, and washing of the sludge shall conform to the followingrequirements:Relative Density at 20C 0.6836 to 0.6839Refractive index at 20C 1.3876 to 1.3879Solidification temper
29、ature, min, C 90.72Distillation 50 % shall distill between 98.38 and98.48C. Temperature rise between 20 and80 % recovery shall be 0.20C maximum6.4 p-Naphtholbenzein Indicator SolutionThe specifications for p-naphtholbenzein are prescribed in Test Method D974.Prepare a solution containing 10 g p-naph
30、tholbenzein per litre of titration solvent (see 6.7).6.5 OxygenObtained from liquid oxygen, minimum Minimum purity 99.4 %.6.6 Potassium Hydroxide Solution, Standard Alcoholic (0.1 N)Prepare alcoholic potassium hydroxide solution andstandardize as described in Test Method D974. Commercially prepared
31、Alcoholic Potassium Hydroxide Solution is available.6.7 Titration SolventMix 3 parts by volume of toluene with 2 parts by volume of isopropyl alcohol.6.8 Silicon Carbide Abrasive Cloth, 100-grit with cloth backing.6.9 Wire CatalystAWG No. 18 (0.0403-in. (1.01-mm) diameter) 99.9 % purity conforming t
32、o Specification B1. Soft-drawncopper wire of equivalent grade may also be used.6.10 Hydrochloric Acid, 10 Volume %.5 “Reagent Chemicals, American Chemical Society Specifications,” Am. Chemical Soc., Washington, DC. For suggestions on the testing of reagents not listed by theAmerican Chemical Society
33、, see “Reagent Chemicals and Standards,” by Joseph Rosin, D. Van Nostrand Co., Inc., New York, NY, and the “United States Pharmacopeia.”FIG. 2 Position of Oil Receptacle in Aging BathD2440 1337. Hazards7.1 Consult Material Safety Data Sheets for all materials used in this test method.8. Preparation
34、of Oxygen Supply8.1 Oxidize the oil by contact with oxygen of 99.4 % minimum purity conditioned as follows:8.1.1 Use metal or glass tubing to deliver the oxygen to the oxygen delivery tube. Eliminate rubbertubing connections ifwhenpossible. If used, the rubbertubing should be at room temperature. Li
35、mit the length of rubber tubing exposed to the oxygen flowto 1340 mm. Do not use rubbertubing connections in contact with the liquid of the heating bath or under conditions where thetemperature of the rubbertubing will be above room temperature. Where it is necessary to use rubbertubing connections,
36、 onlysulfur-free rubbertubing is permissible. FOA/USP Nalgene tubing has and certain types of PVC tubing have been foundsatisfactory in this application.8.1.2 Dry the oxygen by forcing it through a solid desiccant of high moisture-absorbing capacity.6 Arrange the desiccant in thedrying tower to a de
37、pth of 205 to 254 mm. Change the desiccant when the indicator begins to change colors from moistureabsorption. If an indicator is not used, change the desiccant at least weekly.8.1.3 After passing oxygen through the drying tower, admit it directly to the receptacle containing the oil to be tested. D
38、o notpreheat the oxygen.8.1.4 Determine the rate of oxygen supply with an electronic flow meter, calibrated rotameter, or soap bubble buret, and adjustthe flow rate to deliver the conditioned oxygen at a rate of 1.0 6 0.1 L/h to each tube of oil being tested.9. Preparation of Oil Receptacle9.1 Wash
39、each oil receptacle thoroughly, first with acetone and then with soap and water, and rinse in acid solution. Thefollowing reagents have been found suitable: chromic acid, aqua regia, and ammonium persulfate. Wash each receptacle free ofacid, using tap water, and finally rinse with distilled water. D
40、ry in an oven at 105 to 110C for at least 3 h,h; cool to roomtemperature in a desiccator, and keep the receptacle in the desiccator until ready for before use.10. Preparation of Copper Catalyst10.1 Immediately before use, polish the copper wire with silicon carbide abrasive cloth and wipe free of ab
41、rasive with a cleandry cloth. Clean the copper wire with acetone or chloroform before it is wound to remove the debris from polishing.10.2 Wind a 300-mm length of the polished wire into a helical coil approximately 16 mm in outside diameter and 50 mm inheight. Clean the coil thoroughly with chlorofo
42、rm or acetone, air dry, and insert immediately into the oil receptacle. Handle theclean copper coil only with clean tongs and clean gloved hands to avoid contamination.10.3 Commercially available, prepackaged, preformed coils that meet the requirements described in this test method may beused as an
43、alternative method of catalyst preparation. Clean the coil in a 10 % HCl solution for 30 s, rinse three times with tapwater and with distilled water, chloroform or acetone and air dry immediately before use. Preformed coils were used in a 1997Round Robin Study and found suitable for this application
44、.711. Preparation of Glass Crucible and Filtering CrucibleMembrane11.1 Clean the glass filtering crucible and dry the crucibles and filtering membranes in an air oven at 105 to 110C until it hasreached constant mass. Cool and store in a desiccator and, when needed, weigh to the nearest 0.0001 g.12.
45、Conditioning of Test Specimen12.1 Filter the oil test specimen by gravity at ambient pressure or at reduced pressure, through acid-free filter paper to removetraces of sediment, fiber, and excess water. Alternatively, filter the test specimen under vacuum through a 0.45 m mixed ester orcellulose fil
46、ter. Discard the first 25 mL of the oil filtrate. Carefully protect the filtrate during the filtration against dust and othercontaminations.13. Procedure13.1 Prepare two copper catalysts as described in Section 10. Insert one in each of two clean, dry oil receptacles prepared asdescribed in Section
47、9.13.2 Transfer 25 6 0.01 g of the conditioned oil test specimen into each of the two prepared oil receptacles by means of a cleandry pipet. Immediately place the head on the oil receptacle to protect the oil from contamination during the interval betweenplacing the oil in the receptacle and the act
48、ual start of the oxidation.13.3 Adjust the heating bath to maintain a temperature of 110 6 0.5C during the oxidation of the sample.test specimen.6 Anhydrous magnesium perchlorate (Anhydrone or Dehydrite) is a suitable desiccant for this purpose.7 A research report is available from ASTM headquarters
49、. Request RR:D27-1011.D2440 13414. Oxidation14.1 Immerse the oil receptacle in the heating bath, which has been adjusted to the test temperature. Immerse the oil receptaclein the bath to a depth such that the surface of the liquid in the heating bath will be 3 to 5 cm higher than the surface of the testoil in the receptacle, after the test oil reaches test temperature.Attach the oxygen inlet tubes to the oxygen supply line. When morethan one oil receptacle is fed from a single oxygen supply line, adjust the oxygen flow to each oil recepta
