1、Designation: D 3612 02Standard Test Method forAnalysis of Gases Dissolved in Electrical Insulating Oil byGas Chromatography1This standard is issued under the fixed designation D 3612; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 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 covers three procedures for extractionand measurement of gases dissolved in electrical
3、insulating oilhaving a viscosity of 20 cSt (100 SUS) or less at 40C (104F),and the identification and determination of the individualcomponent gases extracted. Other methods have been used toperform this analysis.1.2 The individual component gases that may be identifiedand determined include:Hydroge
4、nH2OxygenO2NitrogenN2Carbon monoxideCOCarbon dioxideCO2MethaneCH4EthaneC2H6EthyleneC2H4AcetyleneC2H2PropaneC3H8PropyleneC3H61.3 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 appr
5、o-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements see 6.1.8, 30.2.2 and 30.3.1.2. Referenced Documents2.1 ASTM Standards:D 2140 Test Method for Carbon-Type Composition of In-sulating Oils of Petroleum Origin2D
6、 2300 Test Method for Gassing of Insulating Oils UnderElectrical Stress and Ionization Modified Pirelli Method2D 2779 Test Method for Estimation of Solubility of Gasesin Petroleum Liquids3D 2780 Test Method for Solubility of Fixed Gases inLiquids3D 3613 Test Methods of Sampling Electrical Insulating
7、 Oilsfor Gas Analysis and Determination of Water Content2D 4051 Practice for Preparation of Low-Pressure GasBlends3E 260 Practice for Packed Column Gas Chromatography42.2 IEEE Standard:C 57.104 Guide for the Interpretation of Gases Generated inOil-Immersed Transformers52.3 IEC Standard:Publication N
8、o. 567 Guide for the Sampling of Gases andof Oil from Oil-Filled Electrical Equipment and for theAnalysis of Free and Dissolved Gases63. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 gas content of oil by volumein Method A, the totalvolume of gases, corrected to 760 torr (101.3
9、25 kPa) and 0C,contained in a given volume of oil, expressed as a percentage.In Methods B and C, the sum of the individual gas concentra-tions corrected to 760 torr (101.325 kPa) and 0C, expressed inpercent or parts per million.3.1.2 headspacea volume of gas phase in contact with avolume of oil in a
10、 closed vessel. The vessel is a headspace vialof 20-mL nominal capacity.3.1.2.1 DiscussionOther vessel volumes may also beused, but the analytical performance may be somewhat differ-ent than that specified in Method C.3.1.3 parts per million (ppm) by volume of (specific gas) inoilthe volume of that
11、gas corrected to 760 torr (101.325 kPa)and 0C, contained in 106volume of oil.3.1.4 sparging, vagitating the liquid sample using a gas tostrip other gases free.3.1.5 volume concentration of (specific gas) in the gassamplethe volume of the specific gas contained in a givenvolume of the gas sample at t
12、he same temperature and pressure1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.03 on Analytical Tests.Current edition approved Oct. 10, 2002. Published December 2002. Originallyapproved
13、 in 1977. Last previous edition approved in 2001 as D 3612 01.2Annual Book of ASTM Standards, Vol 10.03.3Annual Book of ASTM Standards, Vol 05.02.4Annual Book of ASTM Standards, Vol 14.02.5Available from IEEE, 345 E. 47th St., New York, NY 10017.6Available from IEC.1Copyright ASTM International, 100
14、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(as the measured total volume), expressed either as a percent-age or in parts per million.4. Summary of Test Method4.1 Method ADissolved gases are extracted from a sampleof oil by introduction of the oil sample into a p
15、re-evacuatedknown volume. The evolved gases are compressed to atmo-spheric pressure and the total volume measured.4.2 Method BDissolved gases are extracted from a sampleof oil by sparging the oil with the carrier gas on a strippercolumn containing a high surface area bead.4.3 Method CMethod C consis
16、ts of bringing an oil samplein contact with a gas phase (headspace) in a closed vesselpurged with argon. The dissolved gases contained in the oil arethen equilibrated in the two phases in contact under controlledconditions (in accordance with Henrys law). At equilibrium,the headspace is overpressuri
17、zed with argon and then thecontent of a loop is filled by the depressurization of theheadspace against the ambient atmospheric pressure. The gasescontained in the loop are then introduced into a gas chromato-graph.4.4 There may be some differences in the limits of detectionand precision and bias bet
18、ween Methods A, B, and C forvarious gases.4.5 Aportion of the extracted gases (MethodA) or all of theextracted gases (Method B) or a portion of the headspace gases(Method C) is introduced into a gas chromatograph. Calibra-tion curves are used in Method C to establish the concentrationof each species
19、. The composition of the sample is calculatedfrom its chromatogram by comparing the area of the peak ofeach component with the area of the peak of the samecomponent on a reference chromatogram made on a standardmixture of known composition.5. Significance and Use5.1 Oil and oil-immersed electrical i
20、nsulation materials maydecompose under the influence of thermal and electricalstresses, and in doing so, generate gaseous decompositionproducts of varying composition which dissolve in the oil. Thenature and amount of the individual component gases that maybe recovered and analyzed may be indicative
21、 of the type anddegree of the abnormality responsible for the gas generation.The rate of gas generation and changes in concentration ofspecific gases over time are also used to evaluate the conditionof the electric apparatus.NOTE 1Guidelines for the interpretation of gas-in-oil data are given inIEEE
22、 C 57.104.6. Apparatus6.1 Apparatus7of the type shown in Fig. 1 or Fig. 2 issuitable for use with up to 50-mL samples of oil and consistsof the following components:NOTE 2This sample size has been found to be sufficient for most oils.However, oil that has had only limited exposure to air may contain
23、 muchsmaller amounts of nitrogen and oxygen. For these oils it may be desirableto increase the size of the sample and the extraction apparatus.NOTE 3Alternative apparatus designs including the use of a Toeplerpump have also been found successful.6.1.1 Polytetrafluoroethylene (PTFE) Tubing, narrow-bo
24、re,terminated with a Luer-Lock fitted glass syringe, and leading toa solid plug, three-way, high-vacuum stopcock.6.1.2 Degassing Flask, with a glass inlet tube, of sufficientvolume to contain up to 50 mL of oil below the inlet tube,capable of being evacuated through a vacuum pump, contain-ing a PTFE
25、-coated magnetic spin bar, and mounted on amagnetic stirrer.6.1.3 Means of Measuring Absolute Pressure within theapparatus.6.1.4 Vacuum Pumping System, capable of evacuating theglassware to an absolute pressure of 1 3 103torr (130 mPa)or lower.6.1.5 Vacuum Glassware, sufficiently large compared to t
26、hevolume of the oil sample, so that virtually complete degassingis obtained and that the volumetric collection ratio is as large aspossible. A 500-mL gas collecting flask has been foundsuitable.6.1.6 High-Vacuum Valves or Stopcocks, employing theminimum necessary amounts of high-vacuum stopcock grea
27、seare used throughout the apparatus.6.1.7 Gas Collection Tube, calibrated in 0.01-mL divisions,capable of containing up to 5 mL of gas, terminated with asilicone rubber retaining septum. A suitable arrangement isshown in Fig. 3.6.1.8 Reservoir of Mercury, sufficient to fill the collectionflask and c
28、ollection tube. (WarningMercury vapor is ex-tremely toxic. Appropriate precautions should be taken.)7. Sampling7.1 Obtain samples in accordance with the procedure de-scribed in Test Methods D 3613 for sampling with syringetypedevices or rigid metal cylinders. The use of rigid metalcylinders is not r
29、ecommended for use with Method B.7.2 The procurement of representative samples without lossof dissolved gases or exposure to air is very important. It is alsoimportant that the quantity and composition of dissolved gasesremain unchanged during transport to the laboratory. Avoidprolonged exposure to
30、light by immediately placing drawnsamples into light-proof containers and retaining them thereuntil the start of testing.7.2.1 To maintain the integrity of the sample, keep the timebetween sampling and testing as short as possible. Evaluatecontainers for maximum storage time. Samples have beenstored
31、 in syringes and metal cylinders for four weeks with noappreciable change in gas content.NOTE 4Additional sampling procedures using flexible metal cans arecurrently being studied for use with Method A.METHOD AVACUUM EXTRACTION8. Method AVacuum Extraction8.1 Method A employs vacuum extraction to sepa
32、rate thegases from the oil. The evolved gases are compressed to7Ace Glass and Lurex Glass manufacture glass extractors. For Ace Glass, theglass apparatus conforming to Fig. 1 is Part E-13099-99-99 and Fig. 2 is PartE-1400-99. Available from P.O. Box 688, 1430 Northwest Blvd., Vineland, NJ08360 or Lu
33、rex Glass, 1298 Northwest Blvd., Vineland, NJ 08360.D 3612 022FIG. 1 Extraction of Gas from Insulating OilFIG. 2 Extraction of Gas from Insulating OilD 3612 023atmospheric pressure and the total volume measured. Thegases are then analyzed by gas chromatography.9. Preparation of Apparatus9.1 Check th
34、e apparatus carefully for vacuum tightness ofall joints and stopcocks.9.2 Measure the total volume of the extraction apparatus,VT, and the volume of the collection space, Vc, and calculatethe ratio as the volumetric collection ratio:VcVT2 Vo(1)where Vo= the volume of oil to be added.9.3 Calculate th
35、e degassing efficiencies for each individualcomponent gas as follows:Ei511 1KiVoVT2 Vo(2)where:Ei= degassing efficiency of component i,Vo= volume of oil sample,VT= total internal volume of extraction apparatus beforeoil sample is introduced, andKi= Ostwald solubility coefficient of component i.9.4 D
36、etermine the Ostwald solubility coefficients of fixedgases in accordance with Test Method D 2780.9.5 Ostwald solubility coefficients that have been deter-mined for a number of gases in one specific electrical insulat-ing oil at 25C are shown as follows. Values for gases in otheroils may be estimated
37、 by reference to Test Method D 2779.Component GasOstwald Solubilityfvariant8 (Note 5)Coefficient, Ki, 25C, 760 mm HgHydrogen 0.0558Nitrogen 0.0968Carbon monoxide 0.133Oxygen 0.179Methane 0.438Carbon dioxide 1.17Acetylene 1.22Ethylene 1.76Ethane 2.59Propane 11.0NOTE 5The Ostwald coefficient values sh
38、own in this table are correctonly for the specific mineral oil having a density at 15.5C of 0.855 g/cm3used in the original determination. Ostwald coefficients for mineral oils ofdifferent density may be calculated as follows:Kicorrected!5Ki0.980 2 density0.130(3)where, density = density of the oil
39、of interest, g/cm3at 15.5C (60F).This equation is derived from the equation in Test Method D 2779. Noteespecially that all of the Ostwald coefficients are changed by the samefactor, meaning that though the absolute solubilities of each of the gaseswill change if a different oil is used, the ratio of
40、 the solubility of one gasto another gas will remain constant.9.6 A procedure to check the extraction efficiency requiresthe use of prepared gas-in-oil standards of known concentra-tion. The methods of preparation are outlined inAnnexA1 andAnnex A2.10. Procedure10.1 Lower the mercury level from the
41、collection flask.10.2 Evacuate the system of collection flask and degassingflask to an absolute pressure of 1 3 103torr (130 mPa) or less.(In Fig. 1, the space above the mercury in the reservoir mustalso be evacuated.)10.3 Connect the oil sample syringe by the PTFE tubing tothe three-way stopcock le
42、ading to the degassing flask.10.4 Flush a small quantity of oil from the syringe throughthe tubing and stopcock to waste, making sure that all the air inthe connecting tubing is displaced by oil.10.4.1 Any gas bubbles present in the syringe should beretained during this flushing operation. This may
43、be accom-plished by inverting the syringe so that the bubble remains atthe plunger end of the syringe during the flushing operation.10.5 Close the stopcocks to the vacuum pumps and thenslowly open the three-way stopcock to allow oil and any gasbubbles that may be present from the sample syringe to e
44、nterthe degassing flask.10.6 Allow the desired amount of oil to enter the degassingflask and operate the magnetic stirrer vigorously for approxi-mately 10 min. This is the volume, Voused in the calculationin 15.4.10.6.1 If a gas bubble is present in the syringe, eitheranalyze the total content of th
45、e syringe including the bubble;or, if the gas bubble is large, and it is suspected that theconcentration of dissolved gases is high, measure and analyzethe gas bubble separately, extract an aliquot of the oil sample,and correct as applicable.10.7 Close the stopcock isolating the collection flask, an
46、dallow mercury to flow into the collection flask.10.8 Open the stopcock to the reference column and bymeans of the hand pump (Fig. 1) or leveling bottle (Fig. 2)bring the level of the mercury in the reference column evenwith the level in the collection tube.10.9 Measure the volume of extracted gas i
47、n the collectiontube, and correct for collection efficiency by dividing it by the8Daoust, R., Dind, J. E., Morgan, J., and Regis, J, “Analysis of Gas Dissolvedin Transformer Oils,” Doble Conference, 1971, Sections 6110.FIG. 3 Retaining Rubber Septum for Gas Collection TubeD 3612 024volumetric collec
48、tion ratio calculated in 9.2. Correct to 760 torr(101.325 kPa) and 0C. Determine the volume of oil degassedin the degassing flask. Record the gas content as a percentageof the oil by volume.10.10 Because the total concentration of gas is not extract-able from the oil, a rinse step may be required wh
49、en highquantities are present. The extractor can be rinsed with oilcontaining nondetectable quantities of gases, except for thosepresent in air. The amount of rinsing needed will be dependentupon the gas concentration, type (solubility in oil), andefficiency of the extractor. To ensure that the combustible gaseshave been sufficiently removed from the extractor, the rinse oilmay be treated as a sample. General rinse procedures may beestablished. However, for samples with very high concentra-tions of gases, verify effectiveness of the rinse
