1、Designation: D 3612 021Standard 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 () indicates an editorial change since the last revision or reapproval.1NOTEThe mercury warning was added editorially in April 2009.1. Scope1.1 This test method covers three procedures fo
3、r extractionand measurement of gases dissolved in electrical 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 compone
4、nt gases that may be identifiedand determined include:HydrogenH2OxygenO2NitrogenN2Carbon monoxideCOCarbon dioxideCO2MethaneCH4EthaneC2H6EthyleneC2H4AcetyleneC2H2PropaneC3H8PropyleneC3H61.3 WarningMercury has been designated by EPA andmany state agencies as a hazardous material that can causecentral
5、nervous system, kidney, and liver damage. Mercury, orits vapor, may be hazardous to health and corrosive tomaterials. Caution should be taken when handling mercury andmercury-containing products. See the applicable product Ma-terial Safety Data Sheet (MSDS) for details and EPAs website(http:/www.epa
6、.gov/mercury/faq.htm) for additional informa-tion. Users should be aware that selling mercury or mercury-containing products, or both, in your state may be prohibited bystate law.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespon
7、sibility of the user of this standard to establish appro-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 Practice for Calculating C
8、arbon-Type Compositionof Insulating Oils of Petroleum OriginD 2300 Test Method for Gassing of Electrical InsulatingLiquids Under Electrical Stress and Ionization (ModifiedPirelli Method)D 2779 Test Method for Estimation of Solubility of Gasesin Petroleum LiquidsD 2780 Test Method for Solubility of F
9、ixed Gases inLiquidsD 3613 Practice for Sampling Insulating Liquids for GasAnalysis and Determination of Water Content2D 4051 Practice for Preparation of Low-Pressure GasBlendsE 260 Practice for Packed Column Gas Chromatography2.2 IEEE Standard:C 57.104 Guide for the Interpretation of Gases Generate
10、d inOil-Immersed Transformers32.3 IEC Standard:Publication No. 567 Guide for the Sampling of Gases andof Oil from Oil-Filled Electrical Equipment and for theAnalysis of Free and Dissolved Gases43. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 gas content of oil by volumein Meth
11、od A, the totalvolume of gases, corrected to 760 torr (101.325 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.1This test m
12、ethod 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 in 1977. Last previous edition approved in
13、2001 as D 3612 01.2Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.3Available from IEEE, 345 E. 47th St., New York, NY 10017.4Available from IEC.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United S
14、tates.3.1.2 headspacea volume of gas phase in contact with avolume of oil in a 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.
15、3 parts per million (ppm) by volume of (specific gas) inoilthe volume of that 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 gassampleth
16、e volume of the specific gas contained in a givenvolume of the gas sample at the same temperature and pressure(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 introducti
17、on of the oil sample into a pre-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 bea
18、d.4.3 Method CMethod C consists 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,
19、the headspace is overpressurized 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 detect
20、ionand precision and bias between 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
21、 concentrationof each species. 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
22、and oil-immersed electrical insulation 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 a
23、nd analyzed may be indicative 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
24、-in-oil data are given inIEEE C 57.104.6. Apparatus6.1 Apparatus5of 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 limite
25、d exposure to air may contain 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 Polytetrafluoroethy
26、lene (PTFE) Tubing, narrow-bore,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 va
27、cuum pump, contain-ing a PTFE-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, suf
28、ficiently large compared to thevolume 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
29、 of high-vacuum stopcock greaseare 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 f
30、ill the collectionflask and collection 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
31、rigid metalcylinders is not recommended 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
32、. Avoidprolonged exposure to light by immediately placing drawnsamples into light-proof containers and retaining them thereuntil the start of testing.5Ace 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 Pa
33、rtE-1400-99. Available from P.O. Box 688, 1430 Northwest Blvd., Vineland, NJ08360 or Lurex Glass, 1298 Northwest Blvd., Vineland, NJ 08360.D 3612 0212FIG. 1 Extraction of Gas from Insulating OilFIG. 2 Extraction of Gas from Insulating OilD 3612 02137.2.1 To maintain the integrity of the sample, keep
34、 the timebetween sampling and testing as short as possible. Evaluatecontainers for maximum storage time. Samples have beenstored in syringes and metal cylinders for four weeks with noappreciable change in gas content.NOTE 4Additional sampling procedures using flexible metal cans arecurrently being s
35、tudied for use with Method A.METHOD AVACUUM EXTRACTION8. Method AVacuum Extraction8.1 Method A employs vacuum extraction to separate thegases from the oil. The evolved gases are compressed toatmospheric pressure and the total volume measured. Thegases are then analyzed by gas chromatography.9. Prepa
36、ration of Apparatus9.1 Check the 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 o
37、il to be added.9.3 Calculate the 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 c
38、oefficient of component i.9.4 Determine 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 gase
39、s in otheroils may be estimated by reference to Test Method D 2779.Component GasOstwald Solubility6(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
40、 coefficient values shown 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
41、 = density of the oil 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
42、 is used, the ratio of 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 m
43、ercury level from the 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
44、 three-way stopcock leading 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 flushin
45、g operation. This may 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 t
46、he sample syringe to enterthe 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 t
47、he total content of the syringe including the bubble;6Daoust, 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 0214or, if the gas bubble is large, and it is su
48、spected 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, andallow mercury to flow into the collection flask.10.8 Open the stopcock to
49、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 in the collectiontube, and correct for collection efficiency by dividing it by thevolumetric collection 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 tot
