1、Designation: D 1534 95 (Reapproved 2002)e1Standard Test Method forApproximate Acidity in Electrical Insulating Liquids byColor-Indicator Titration1This standard is issued under the fixed designation D 1534; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made in April 2002.1. Scope1.1 This test method describes the de
3、termination of theapproximate total acid value of used electrical insulatingliquids having viscosities less than 24 cSt at 40C. It is a simpleprocedure that can be applied in the field. Where a quantitativeneutralization value is required, use Test Method D 664 or TestMethod D 974. These test method
4、s should be applied in thelaboratory.1.2 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 lim
5、itations prior to use.2. Referenced Documents2.1 ASTM Standards:D 664 Test Method for Acid Number of Petroleum Productsby Potentiometric Titration2D 974 Test Method for Acid and Base Number by Color-Indicator Titration2D 1193 Specification for Reagent Water33. Summary of Test Method3.1 To determine
6、whether the acidity is greater or less thana specified arbitrary value, a fixed volume of liquid to be testedis added to a graduated cylinder, together with a small amountof indicator (phenolphthalein) and the appropriate quantity ofstandard potassium hydroxide solution. The mixture is shakenand all
7、owed to separate. The color of the aqueous layer at thebottom of the container when testing mineral oils, or at the topwhen testing askarels, determines whether the acidity is lessthan or greater than the arbitrary value chosen.3.2 To determine the approximate total acidity, the proce-dure is the sa
8、me as described in 3.1 except that the potassiumhydroxide solution is added in small increments until the colorof the aqueous layer, after shaking and settling, is a faint pink.The volume of standard potassium hydroxide solution useddetermines the approximate total acid value.4. Significance and Use
9、4.1 The approximate acidity of used electrical insulatingoils is an estimate of the total acid value of the oil. As acidvalues increase, oil quality decreases. This is usually due tooxidation of the oil while in service. In general, acidicby-products produce increased dielectric loss, increased corr
10、o-sivity, and may cause thermal difficulties attributable to in-soluble components called “sludge.” This test method isadapted to a specific volume of oil; total acid values of 0.05 to0.5 mg of potassium hydroxide per gram of oil is a range whichis functionally significant.5. Apparatus5.1 Graduated
11、Cylinder, 50 mL, stoppered.5.2 Medicine Dropper, calibrated at 1-mL intervals.5.3 Calibrated Pipet, 1-mL capacity, calibrated to deliver0.05-mL increments.6. Reagents and Materials6.1 Purity of ReagentsUse reagent grade chemicals in alltests. Unless otherwise indicated, it is intended that all reage
12、ntsshall conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society, wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the acc
13、uracy ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water (see Note1) conforming to Specification D 1193.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the
14、direct responsibility of Subcom-mittee D27.06 on Chemical Test.Current edition approved Sept. 10, 1995. Published November 1995. Originallypublished as D 1534 58 T. Last previous edition D 1534 90.2Annual Book of ASTM Standards, Vol 05.01.3Annual Book of ASTM Standards, Vol 11.01.4Reagent Chemicals,
15、 American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Form
16、ulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.NOTE 1Any grades of water listed in Specification D 1193 aredeemed satisfactory for the purpose of this test method.6.3 E
17、thyl or Isopropyl Alchol, reagent grade.6.4 Phenolphthalein Indicator Solution (100 g/L)Dissolve 10 g of phenolphthalein in 100 mL of denaturedalcohol by slight warming.6.5 Potassium Hydroxide, Standard Solution (0.031 60.003 N)Prepare a 0.031 6 0.003 N solution of potassiumhydroxide (KOH) by dissol
18、ving solid KOH in a solution ofequal volumes of alcohol and water in accordance with themethod of preparation and standardization described in TestMethod D 974 or Test Method D 664, except for the solventand the normality.NOTE 2As applied to mineral oil, this normality is chosen to simplifythe calcu
19、lation. The 20-mL sample weighs 17.6 g, assuming an averagespecific gravity of 0.88. With a 17.6-g sample, 10 mL of 0.031 N KOHsolution corresponds to an acid value of 1. The normality should bechecked from time to time in a laboratory. If it is outside the 60.003tolerance, due either to evaporation
20、 of solvent or precipitation of potas-sium carbonate (K2CO3) formed by reaction with carbon dioxide (CO2)from the atmosphere, it should be discarded.The specific gravity of commonly used askarels is 1.56, or approxi-mately 1.8 times that of mineral oil, and this difference must be recognizedin the c
21、alculation or equipment calibration, or both, as applied to askarels.7. Procedure7.1 Rinse the graduated cylinder first with denatured alcoholand then with a small amount of the liquid to be tested. Pour inthe test specimen to the 20-mL mark and add two drops ofindicator solution with a medicine dro
22、pper. Proceed in accor-dance with 7.2 or 7.3.7.2 To determine whether the acidity is greater or less thana value specified by the user, add the appropriate volume ofKOH solution by dispensing from a calibrated pipet (forexample, 0.5 mL if the fixed figure is 0.05 mg KOH per gramof oil, as applied to
23、 oil). Shake vigorously for several seconds,allow to settle, and observe the aqueous layer. If it is free ofpink, the acidity is greater than the specified value.7.3 To determine the approximate total acidity, add KOHsolution in increments of 0.5 mL until the color of the aqueouslayer, after shaking
24、 and settling, is a pale pink.8. Calculation8.1 For mineral oil, calculate the approximate total acidvalue, T, as follows:T 5 B 2 A!/10 (1)where:A = test specimen used, (20) mL,B = liquid in the cylinder at the conclusion of the test,mL, andBA = KOH solution added, mL.8.2 For askarel, calculate the
25、approximate total acid value,T, as follows:T 5 B 2 A!/18 (2)NOTE 3Other concentrations of base may be used in the titration. Aless concentrated solution of KOH provides a greater volume of theaqueous layer. The calculations must then be modified to account for thedifference in the concentration of b
26、ase.NOTE 4As an alternative, prepackaged field kits have been used.59. Report9.1 Report the following information:9.1.1 The approximate total acidity value, T, in mgKOH/gtest specimen.9.1.2 When possible, report the acidity as “greater than” or“less than” the value specified by the user.10. Precisio
27、n and Bias10.1 This test method provides for an approximation of totalacidity, with a minimum detection level of 0.005 mgKOH/gtest specimen. The total acidity is based on whether the acidityis greater or less than a user-specified value corresponding tothe addition of specific volumes of KOH solutio
28、n. Because thistest method is only an approximation of total acidity, precisionand bias statements will not be developed.10.2 To determine quantitative acidity values, use TestMethod D 664 or Test Method D 974.11. Keywords11.1 acidity; color titration; insulating liquid; neutralizationnumberASTM Int
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30、y their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand sh
31、ould be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on St
32、andards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).5Field kits, available from Gerin Co., 1109 Seventh Ave., Neptune, NJ 07753have been found satisfactory for this purpose.D 15342
