1、Designation:D 2945 90(Reapproved 2003)e1Standard Test Method forGas Content of Insulating Oils1This standard is issued under the fixed designation D 2945;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A num
2、ber in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.e1NOTEThe metric value for the inside diameter of vinyl tubing in Fig.1 was corrected editorially in December 2003.1.Scope1.1 This test method covers th
3、e determination of the gascontent of electrical insulating oils of low and mediumviscosities in the general range of 100 SUS and below at 100F(37.8C),and is suitable for field or laboratory use.NOTE1For testing insulating oils with viscosities above 100 SUS,seeTest Method D 831.For individual gas co
4、ncentrations,see MethodD 3612.1.2 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 limitations p
5、rior to use.2.Referenced Documents2.1 ASTM Standards:2D 831 Test Method for Gas Content of Cable and CapacitorOilsD 3612 Test Method for Analysis of Gases Dissolved inElectrical Insulating Oil by Gas ChromatographyD 3613 Practice for Sampling Insulating Liquids for GasAnalysis and Determination of W
6、ater Content3.Summary of Test Method3.1 This test method consists essentially of allowing oil toflow into an evacuated chamber as a thin film so that the oil isthoroughly exposed to the vacuum,allowing free volatilizationof the gaseous component.The system is brought back toatmospheric pressure,and
7、the evolved gases measured.Fromthe volume of oil degassed in the chamber and the volume ofreleased gas,the percent gas content may be estimated.Theapparatus used produces the necessary vacuum without resort-ing to use of a vacuum pump.This test method partiallydegases the oil.The degree of degasific
8、ation varies with thesolubility of each gas in the oil.4.Significance and Use4.1 In filling electrical apparatus,it is desirable to use lowgas content transformer oil in order to prevent foaming and toavoid air pockets that might result in gaseous ionization.Thisprocedure provides a simple method to
9、 measure the gas contentof the oil,and may be used as a factory-control test and as acontrol or functional test in installation and maintenance workby utilities.5.Apparatus5.1 Dissolved Gas Content AnalyserFig.1 shows theassembled instrument,not drawn to scale,to permit magnifi-cation of small detai
10、ls.A borosilicate glass gas buret,100-mLcapacity,graduated in15-mL divisions,serves as a vacuumchamber.A three-way stopcock,120 bore with TFE-fluorocarbon plug,3 stem,2-mm bore is fused to the buret orjoined by a vinyl sleeve so that the joint is vacuum tight.5.1.1 Rubber Vacuum TubingAbout 1200 mm
11、of 8-mmrubber vacuum tubing is securely fastened with a 20-mmHoffman pinch clamp to the lower tip of the buret,while theother end is secured to a 250-mL capacity leveling bulb.5.1.2 Stubs 20 Gage NeedleA short section,about 40 mmlong,is cut and cemented to the three-way stopcock,Fig.2.This serves to
12、 accommodate the vinyl tubing attached to thesyringe.All the glassware should be clamped to a suitable 1500by 700 by 20-mm mounting board with rubber-covered wall-type clamps.5.1.3 Metal Rod,12 mm,1500 mm long,fitted with anadjustable leveling bulb support is fastened to the woodenapparatus mounting
13、 board as in 5.1.2.5.2 Syringe Assembly(see Fig.3)A 50-mL Luer syringewith 5-mL subdivisions or a 5-mL Luer syringe with15-mLsubdivisions is fitted with a 150-mm length of 0.8-mm insidediameter capillary vinyl tubing.An upper and lower collar ofplastic or metal is attached to the syringe to support
14、the rubber1This 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 Feb.23,1990.Published April 1990.Originallypublished as D 2945 71.Last previous
15、edition D 2945 84.2For 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 Document Summary page onthe ASTM website.1Copyright ASTM International,100 Barr Harbor Dr
16、ive,PO Box C700,West Conshohocken,PA 19428-2959,United States.bands required to create positive pressure in the syringe.A20-mm Hoffman pinch clamp is used on the capillary tubingafter sampling.5.3 Oil Sampler(see Fig.3)A 3.2-mm tee is fitted with asyringe needle stem in one arm and a short length of 6.4-mm.Vinyl tubing is attached to the other arm.During sampling,thetee is attached to the sampling valve and the vinyl capillarytubing of the syringe assembly is attached to the needle of thetee.1 g