1、Designation: D 2440 99 (Reapproved 2004)Standard Test Method forOxidation Stability of Mineral Insulating Oil1This standard is issued under the fixed designation D 2440; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 resis
3、tance 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 fo
4、r used orreclaimed oils.NOTE 1A shorter duration oxidation test for evaluation of inhibitedoils 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.21.2 The values stated in metric units are to be r
5、egarded asthe standard.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
6、 to use.2. Referenced Documents2.1 ASTM Standards:3B 1 Specification for Hard-Drawn Copper WireD 664 Test Method forAcid Number of Petroleum Productsby Potentiometric TitrationD 974 Test Method for Acid and Base Number by Col-orIndicator TitrationD 2112 Test Method for Oxidation Stability of Inhibit
7、edMineral Insulating Oil by Rotating BombD 2272 Test Method for Oxidation Stability of Steam Tur-bine Oils by Rotating Pressure VesselD 3487 Specification for Mineral Insulating Oil Used inElectrical Apparatus2.2 IEC Publication:CEI/IFC 61125: 1992 Unused HydrocarbonBased Insulat-ing LiquidsTest Met
8、hods for Evaluating the OxidationStability43. 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 evalua
9、ted 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
10、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 underpres
11、cribed 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 D 3487 tend to minimizeelectrical conduction, ensure acceptable heat transfe
12、r, 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 t
13、he consistencyof oxidation stability of production oils.5. Apparatus5.1 Aging (Oxidation) BathAn oil bath, wax bath, oraluminum block heater (see IEC Standard 61125) of a suitabletype capable of controlling the temperature at 110 6 0.5C1This test method is under the jurisdiction of ASTM Committee D2
14、7 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.06 on Chemical Test.Current edition approved Oct. 1, 2004. Published November 2004. Originallyapproved in 1965 as D 2440 65 T. Last previous edition approved in 1999 asD 2440 99.2ASTM Research Report No
15、. RR: D27-1001, available from ASTM Headquar-ters, 100 Barr Harbor Drive, West Conshohocken, PA 19428.3For 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
16、Document Summary page onthe ASTM website.4International Electrotechnical Commission. Available from American NationalStandards Institute, 25 W. 43rd St., 4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.w
17、ith a temperature gradient of less than 1C in the body of theliquid. Use any nontoxic liquid having low volatility at 110Cand containing no volatile additives and having a flash pointabove the test temperature. Mineral oils, waxes and siliconeoils have been used satisfactorily. Circulation of the oi
18、l or waxheating medium by means of a pump or stirrer is recom-mended. See also 5.4, relating to the depth of fluid in agingbath and position of oil receptacles.5.2 Drying TowerA drying tower 25 to 30 cm in height,fitted with a ground-glass stopper and side tubes for condition-ing of the oxygen suppl
19、y.5.3 Oil Receptacle and HeadAn oil receptacle consistingof a heat-resistant glass test tube 25 mm in outside diameter,1.25 mm in wall thickness, 210 mm in overall length includinga standard taper 24/40 outer joint, with a Dreschsel-type headconsisting of a standard taper 24/40 inner joint with side
20、 outlettube 5.0 mm in outside diameter and an oxygen delivery tube5.0 mm in outside diameter and 3 mm, minimum, in insidediameter which extends to within 2.5 6 0.5 mm of the bottomof the oil receptacle and has its end ground at an angle of 30to the axis of the tube. The design is shown in Fig. 1.5.4
21、 Position the oil receptacle in the aging bath in accor-dance with the drawing shown in Fig. 2.NOTE 3The oil receptacle and position in the aging bath are essen-tially the same as specified in IEC Standard 61125, “Test Method forOxidation Stability of Inhibited Mineral Insulating Oils,” Glasswaredim
22、ensions have been altered slightly to conform to sizes readily availablein the United States.5.5 Filtering CruciblesA glass filter crucible having amaximum diameter of the pores between 5 and 15 m asdetermined in accordance with the method described in theAppendix. Cellulose ester type membrane filt
23、ers of 5-mporosity have been used successfully also.6. Reagents and Materials6.1 Purity of ReagentsUse reagent grade chemicals in alltests. Unless otherwise indicated, all reagents are to conform tothe specifications of the Committee on Analytical Reagents ofthe American Chemical Society, where such
24、 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 temperat
25、ure, 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 specifica-tions for p-naphtholbenzein are prescribed in Test MethodD 974. Prepare a solution containing 10 g p-naph
26、tholbenzeinper litre of titration solvent (see 6.7).6.5 OxygenObtained from liquid oxygen, minimum pu-rity 99.4 %.6.6 Potassium Hydroxide Solution, Standard Alcoholic (0.1N)Prepare alcoholic potassium hydroxide solution and stan-dardize as described in Test Method D 974. Commerciallyprepared Alcohol
27、ic Potassium Hydroxide Solution is available.6.7 Titration SolventMix 3 parts by volume of toluenewith 2 parts by volume of isopropyl alcohol.6.8 Silicon Carbide Abrasive Cloth, 100-grit with clothbacking.6.9 Wire CatalystAWG No. 18 (0.0403-in. (1.01-mm)diameter) 99.9 % purity conforming to Specific
28、ation B1.Soft-drawn copper wire of equivalent grade may also be used.6.10 Hydrochloric Acid, 10 Volume %.7. Hazards7.1 Consult Material Safety Data Sheets for all materialsused in this test method.8. Preparation of Oxygen Supply8.1 Oxidize the oil by contact with oxygen of 99.4 %minimum purity condi
29、tioned as follows:8.1.1 Use metal or glass tubing to deliver the oxygen to theoxygen delivery tube. Eliminate rubber connections if possible.If used, the rubber should be at room temperature. Limit thelength of rubber tubing exposed to the oxygen flow to 13 mm.Do not use rubber connections in contac
30、t with the liquid of theheating bath or under conditions where the temperature of therubber will be above room temperature. Where it is necessaryto use rubber connections, only sulfur-free rubber is permis-sible. FOA/USP Nalgene tubing has been found satisfactory inthis application.5“Reagent Chemica
31、ls, American Chemical Society Specifications,” Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing of reagents not listed bytheAmerican Chemical Society, see “Reagent Chemicals and Standards,” by JosephRosin, D. Van Nostrand Co., Inc., New York, NY, and the “United StatesPharmacopeia.
32、”FIG. 1 Oil Receptacle and HeadD 2440 99 (2004)28.1.2 Dry the oxygen by forcing it through a solid desiccantof high moisture-absorbing capacity.6Arrange the desiccant inthe drying tower to a depth of 205 to 254 mm. Change thedesiccant when the indicator begins to change colors frommoisture absorptio
33、n. If an indicator is not used, change thedesiccant at least weekly.8.1.3 After passing oxygen through the drying tower, admitit directly to the receptacle containing the oil to be tested. Donot preheat the oxygen.8.1.4 Determine the rate of oxygen supply with an elec-tronic flow meter, calibrated r
34、otameter, or soap bubble buret,and adjust the flow rate to deliver the conditioned oxygen at arate of 1.0 6 0.1 L/h to each tube of oil being tested.9. Preparation of Oil Receptacle9.1 Wash each oil receptacle thoroughly, first with acetoneand then with soap and water, and rinse in acid solution. Th
35、efollowing reagents have been found suitable: chromic acid,aqua regia, and ammonium persulfate. Wash each receptaclefree of acid, using tap water, and finally rinse with distilledwater. Dry in an oven at 105 to 110C for at least 3 h, cool toroom temperature in a desiccator, and keep the receptacle i
36、n thedesiccator until ready for use.10. Preparation of Copper Catalyst10.1 Immediately before use, polish the copper wire withsilicon carbide abrasive cloth and wipe free of abrasive with aclean dry cloth.10.2 Wind a 300-mm length of the polished wire into ahelical coil approximately 16 mm in outsid
37、e diameter and 50mm in height. Clean the coil thoroughly with chloroform oracetone, air dry, and insert immediately into the oil receptacle.Handle the clean copper coil only with clean tongs to avoidcontamination.10.3 Commercially available, prepackaged, preformed coilsthat meet the requirements des
38、cribed in this test method may beused as an alternative method of catalyst preparation. Clean thecoil in a 10 % HCl solution for 30 s, rinse three times with tapwater and with distilled water, chloroform or acetone and airdry immediately before use. Preformed coils were used in a1997 Round Robin Stu
39、dy and found suitable for this applica-tion.711. Preparation of Glass Filtering Crucible11.1 Clean the glass filtering crucible and dry in an air ovenat 105 to 110C until it has reached constant mass. Cool andstore in a desiccator and, when needed, weigh to the nearest0.0001 g.6Anhydrous magnesium p
40、erchlorate (Anhydrone or Dehydrite) is a suitabledesiccant for this purpose.7A research report is available from ASTM headquarters. RequestRR:D271011.FIG. 2 Position of Oil Receptacle in Aging BathD 2440 99 (2004)312. Conditioning of Test Specimen12.1 Filter the oil test specimen by gravity at ambie
41、ntpressure or at reduced pressure, through acid-free filter paper toremove traces of sediment, fiber, and excess water. Alterna-tively, filter the test specimen under vacuum through a 0.45 mmixed ester or cellulose filter. Discard the first 25 mL of the oilfiltrate. Carefully protect the filtrate du
42、ring the filtration againstdust and other contaminations.13. Procedure13.1 Prepare two copper catalysts as described in Section10. Insert one in each of two clean, dry oil receptacles preparedas described in Section 9.13.2 Transfer 25 6 0.01 g of the conditioned oil testspecimen into each of the two
43、 prepared oil receptacles bymeans of a clean dry pipet. Immediately place the head on theoil receptacle to protect the oil from contamination during theinterval between placing the oil in the receptacle and the actualstart of the oxidation.13.3 Adjust the heating bath to maintain a temperature of110
44、 6 0.5C during the oxidation of the sample.14. Oxidation14.1 Immerse the oil receptacle in the heating bath, whichhas been adjusted to the test temperature. Immerse the oilreceptacle in the bath to a depth such that the surface of theliquid in the heating bath will be 3 to 5 cm higher than thesurfac
45、e of the test oil in the receptacle, after the test oil reachestest temperature. Attach the oxygen inlet tubes to the oxygensupply line. When more than one oil receptacle is fed from asingle oxygen supply line, adjust the oxygen flow to each oilreceptacle to deliver 1 6 0.1 L/h.14.2 Oxidize the two
46、oil test specimens for 72 and 164 hrespectively, under carefully controlled conditions.15. Treatment of Oxidized Oil15.1 Sludge FormationAfter the required period of oxi-dation, shut off the oxygen supply and remove the oil recep-tacle and test specimen from the oxidizing bath. Cool for1htoroom temp
47、erature in a clean dark box or dark room, protectingthe test specimen from dust, moisture, or other contaminationand light. At the end of the cooling period, remove the oxygendelivery tube and the copper catalyst coil from the oil testreceptacle and transfer the oxidized oil into a 500mL Erlen-meyer
48、 flask fitted with a ground glass stopper. Separate 300 mLof n-Heptane into three equal aliquots to be used for thesequential washing of the oxygen delivery tube copper catalystcoil and the test receptacle to recover the adhering oil. Into thesame flask, thoroughly rinse the catalyst coil, delivery
49、tube,and test receptacle to recover adhering oil, using a total of 300mL of n-Heptane.15.2 Weighing SludgeAllow the mixture to stand in thedark for 24 h, at a temperature of 20 6 2C, before filteringthrough a glass filter or polymer membrane, previously dried toconstant weight. To prevent sludge from passing through thefilter, use a small pressure drop at the start of filtering. Passcloudy filtrates through a second time. Remove all traces of oilfrom the sludge by repeated washing with n-Heptane. Wash the500-mL Erlenmeyer flask with n-heptane
