1、Designation: D 6802 02Test Method forDetermination of the Relative Content Of Dissolved DecayProducts in Mineral Insulating Oils by Spectrophotometry1This standard is issued under the fixed designation D 6802; the number immediately following the designation indicates the year oforiginal adoption or
2、 in 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.1. Scope1.1 This test method characterizes by spectrophotometry therelative level of disso
3、lved decay products in mineral insulatingoils of petroleum origin. While new oil is almost transparent toa monochromatic beam of light in the visible spectrum, theincreasing concentration of dissolved decay products shift theabsorbance curve to longer wavelengths.1.2 This test method is applicable t
4、o compare the extent ofdissolved decay products for oils in service. It can assess theeffectiveness of used or stored oil purification during thereclamation process, as well.1.3 The values stated in SI units are to be regarded asstandard. The values stated in parentheses are provided forinformation
5、only.1.4 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 to determine theapplicability of regulatory limitations prior to use.2. Refere
6、nced Documents2.1 ASTM Standards:D 923 Practices for Sampling Electrical Insulating Liquids2D 1524 Test Method for Visual Examination of Used Elec-trical Insulating Oils of Petroleum Origin in the Field2D 3487 Specification for Mineral Insulating Oil Used inElectrical Apparatus23. Terminology3.1 Def
7、initions of Terms Specific to This Standard:3.1.1 aged oil, nan oil that no longer complies with thestandard specifications for mineral insulating oils used inelectrical apparatus according to D 3487.4. Summary of Test Method4.1 A test specimen of mineral insulating oil is placed in a10-mm path leng
8、th glass cuvette, which is installed in anUV-VIS scanning spectrophotometer. The instrument is firstzeroed with spectral grade heptane. The absorbance curve ofoil is then recorded from 360 to 600 nm. Integration of the areaunder this curve indicates the numeric value of the dissolveddecay products i
9、n the oil sample. Because of the high sensi-tivity of spectral analysis, the deterioration of oil purity can beassessed in the early stages of the decay process.5. Significance and Use5.1 The content of dissolved decay products in insulatingoils is made up of a variety of compounds, such as peroxide
10、s,aldehydes, ketones, and organic acids. Each of them is partiallyadsorbed on the large surface of paper insulation leading to thepremature aging of power transformers. The relative assess-ment of byproduct formation, therefore, can be used as anindicator of the aging of the mineral oil.6. Interfere
11、nces6.1 The condition of the oil specimen should be clearaccording to the requirement of Test Method D 1524.6.2 The oil specimen, therefore, should be filtered through50-m filter paper.7. Apparatus7.1 Recording UV-Visible Automated Spectrophotometer,capable of scanning the range between 360 and 600
12、nm isrequired. The software should permit the calculation of areaunder the absorbance curve of the oil specimen.8. Reagents and Materials8.1 Absorption CuvettesTo determine the absorbancecurve of a mineral insulating oil, two matched glass cuvetteshaving a path length of 1-cm 6 0.01-cm should be use
13、d.8.2 Cuvette Filling DeviceA disposable plastic dropper of2-mL capacity is recommended; however, any other suitablepipette may be used.8.3 Petroleum Spirits, of 6080C boiling range.8.4 Heptane, spectral grade.9. Sampling9.1 Obtain the oil sample in accordance with PracticeD 923.1This test method is
14、 under the jurisdiction of Committee D27 on ElectricalInsulating Liquids and Gases and is the direct responsibility of SubcommitteeD27.03 on Analytical Tests.Current edition approved June 10, 2002. Published August 2002.2Annual Book of ASTM Standards, Vol 10.03.1Copyright ASTM International, 100 Bar
15、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.10. Preparation of Apparatus10.1 Clean the cuvettes thoroughly with petroleum spirits.10.2 Adjust the automated spectrophotometer in accordancewith manufacturers recommendation.10.3 Carry out the testing procedure at room t
16、emperature(25 6 5C).11. Procedure11.1 Fill one glass cuvette with heptane; place it in thesample holder and zero the instrument by adjusting it to readzero absorbance.11.2 Move the heptane-filled cuvette by placing it to thereference position.11.3 Fill the second glass cuvette with the oil specimen
17、andplace it into the sample holder.11.4 Set the instrument to scan the region from 360 to 600nm and begin scanning the specimen.11.5 Display the absorbance curve and set the instrument tocalculate the area under the curve.12. Interpretation of Results12.1 A relationship exists between the area under
18、 theabsorbance curve and the total amount of dissolved decayproducts in mineral insulating oils. New oils usually have arelative area under the curve of less than 25 Abs. 3 nm.12.2 The shift of the absorbance curve to longer wave-lengths indicates an increased content of dissolved decayproducts in t
19、he oil.12.3 The shift of the absorbance curve to shorter wave-lengths after reclaiming a used or stored oil indicates theselective removal of dissolved decay products.13. Report13.1 Identification of oil sample.13.2 The value of the calculated area under the absorbancecurve for the oil specimen from
20、 360 to 600 nm.13.3 Comparison of this area to the area of typical new oil,which is usually less than 25 Abs. 3 nm, represents the relativecontent of dissolved decay products.14. Precision and Bias14.1 PrecisionThe precision of this test method has notbeen investigated through an interlaboratory tes
21、t program.14.1.1 RepeatabilityRepeatability measurements made inone laboratory on three samples resulted in a coefficient ofvariation of 2.8 %. At the 95 % confidence level, duplicatedeterminations should agree within 7.8 % of the average of thetwo results (see Table 1).14.1.2 ReproducibilityNo data
22、 are available on which tobase an estimate of the reproducibility of this test method. Aninterlaboratory test program will be conducted to develop thisdata.14.1.3 BiasNo information can be presented on the biasof the procedure for measuring the area under the absorbancecurve in this test method, bec
23、ause no materials having anaccepted reference value are available.15. Keywords15.1 chemical stability; dissolved decay products; insulatingoil; oxidation decay; visible spectrumTABLE 1 Data Used to Develop Precision and Bias Statementsfor Dissolved Decay Product AreaAbsorbance Area Under the CurveSa
24、mple Aged OilSouthAmerica1New Oil2Aged OilNorthAmerica3Test 1 450.42 18.55 359.74Test 2 455.54 18.39 361.03Test 3 450.05 18.85 382.55Test 4 443.08 18.85 387.25Test 5 451.46 18.80 378.36Average of tests (area) 450.11 18.69 373.79Variance, s2(n-1)20.21 0.04 159.75Standard deviation s(n-1)4.50 0.21 12.
25、64Coeff. variation, s/average, % 1.0 1.11 3.38Number of determinations (n) 5 5 5Number of DE (n-1) 4 4 4Grand average, Area 280.86Pooled variance, s260.00Pooled standard dev, s 7.75 Total FE=12Pooled coeff var, s/average, % 2.76Repeatability std dev, s 7.75ASTM repeatability 2.83 s, area 21.92Coeff
26、variation, s/average, % 2.76ASTM repeat 2.83 (s/average), % 7.81D 68022FIG. 1 Absorbance in the Visible Range of SpectrumD 68023FIG. 2 Absorbance in the Visible Range of SpectrumD 68024FIG. 3 Absorbance in the Visible Range of SpectrumD 68025ASTM International takes no position respecting the validi
27、ty of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subjec
28、t 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 should be addressed to ASTM International Headquarte
29、rs. 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 Standards, at the address shown below.This standard
30、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).D 68026
