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.
2、 A number 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 metho
3、d covers the 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.NOTE 1For testing insulating oils with viscosities above 100 SUS, seeTest Method D 831. For in
4、dividual gas concentrations, 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 regul
5、atory limitations prior 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 an
6、d Determination of Water 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 toat
7、mospheric pressure, and 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
8、 oil. The degree of degasification 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. Thisproce
9、dure provides a simple method to 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
10、 permit magnifi-cation of small details. 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 t
11、ight.5.1.1 Rubber Vacuum TubingAbout 1200 mm 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 cemente
12、d to the three-way stopcock, Fig. 2.This serves to 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 bul
13、b support is fastened to the woodenapparatus mounting 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 o
14、fplastic or metal is attached to the syringe to support 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
15、 April 1990. Originallypublished as D 2945 71. Last previous 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 o
16、nthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, 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
17、 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 gas buret, capacity 100 mL
18、, graduated in15-mL divisions1 stopcock, 120 bore with TFE fluorocarbon plug, 3 stems, 2-mm bore1 leveling bulb, capacity 250 mL1 beaker, capacity 250 mL1200 mm (4 ft) vacuum rubber tubing, 8-mm (316-in.) inside diameter2 rubber tubing clamps, adjustable, cadmium-plated steel2-pinch clamps, Hoffman
19、swivel jaw, screw compressor,34 by 1 in. for vinyl tubing for 5 and 50-mL syringes1 pinch clamp, Hoffman screw compressor for rubber tubing,34 by1in.6 clamps, wall type with wood screw to support buret, stopcock, and rod1 leveling bulb support, adjustable, Fisher-Castaloy-R, self-locking1 rod, diame
20、ter 12 mm (12 in.), length 1500 mm (58 in.)1 syringe, Luer, resistance glass, 50 mL, subdivisions 5 mL1 syringe, Luer, resistance glass, 5 mL, subdivisions15 mLVinyl tubing, 1.6-mm (116-in.) inside diameter, wall thickness 1.3 mm (132 in.), length 150 mm (6 in.)4.5 kg (10 lb) mercury1 needle, 50 mm
21、long, Stubbs gage 201 wooden board 1500 by 700 by 20 mm (58 by 28 by78 in.)Components for Gas-Content ApparatusFIG. 1 Dissolved Gas Content AnalyserFIG. 2 Detail of Needle InletD 2945 90 (2003)e125.4 Mercury ReservoirA250-mL capacity leveling bulb isfilled with 4.5 kg (10 lb) of mercury.6. Sampling6
22、.1 Samples should be drawn in accordance with MethodsD 3613. An alternative sample container and method are givenin the Sampling section of Test Method D 831.6.2 An effective method is to take the sample directly fromthe pressurized line into the sampling syringe. The syringe ismaintained under slig
23、ht positive pressure during the taking ofthe sample, during sample transfer, and during the introductionof the sample into the analyzer. This can be accomplished byattaching rubber bands to the syringe to force the barrel into thesyringe or by similar means.6.3 For highly degassed oils, the oil must
24、 not be drawn intothe syringe by pulling at the barrel. For oils fully saturated, orwith a high gas content, the sampling procedure is less critical.However, it is desirable in all cases to obtain samples under apositive pressure.6.4 An example of a sampling arrangement for highlydegassed oils is sh
25、own in Fig. 3. After attaching the syringewith its capillary vinyl tubing, the18-in. sampling valve isopened just enough to provide a steady flow through the14-in.drain tubing without forcing the syringe barrel. After that, thedrain tubing is squeezed by fingers which will create sufficientback pres
26、sure to overcome tension of rubber bands to fill thesyringe. When full, release the drain tubing and allow thesyringe to empty itself into the tee. This is repeated severaltimes with the syringe in vertical position to expel any possibleair bubbles from the syringe and inspect visually. After the la
27、stfiling, a pinch clamp is attached to the syringe tubing, thesampling valve is turned off, and the syringe is transferred withits tubing and closed pinch clamp to the analyzer for test.7. Procedure7.1 The mercury (Hg) reservoir is in position (1) from theprevious test. Fill the buret with mercury u
28、p to the very top ofthe capillary tube. If there is residual oil visible below thethree-way cock, discharge it by manipulating the cock to theBLEED position (F). After expelling the oil, return the cock tothe (1) OFF position (A). Mount the syringe assembly onsupport. Attach the tubing to the needle
29、 on the inlet stem andremove the clamp from the tubing.7.2 Turn the valve counterclockwise to FLUSH position(B). Oil from the syringe will flush out air as well as oil samplefrom the previous test. Continue flushing until the marking onthe syringe barrel coincides with the next syringe cylindergradu
30、ation. Turn the valve counterclockwise to the second OFFposition (C).7.3 Move the mercury reservoir from position 1 to position3 to evacuate chamber. Adjust the pinch clamp at the bottom ofthe buret to permit slow descent of the mercury column untilthe level of the mercury coincides with the zero gr
31、aduation ofburet. Tighten pinch clamp slightly to stop the movement of themercury column. A slight trace of oil will not affect the results.7.4 Turn the valve counterclockwise towards the FILLposition (D) and allow the oil to enter the buret slowly. Oilshould flow as a film on the inside walls of th
32、e buret. When thebarrel has traversed 10 mL (for oil fully saturated1 mL), turnthe valve clockwise to the second OFF position (E).NOTE 2During introduction of the sample, do not allow the barrel toreach the bottom of the syringe bore. This would create negative pressurein the syringe tubing and conc
33、eivably, air could be sucked into the oil, thuscreating an erroneously high reading.7.5 Change the reservoir from position 3 to position 2.Allow 1 min for the oil in the buret to degas. Loosen the clampslightly at the bottom of the buret to permit the column ofmercury to rise slowly in the buret. Ad
34、just the position of themercury reservoir so that the surfaces of the mercury in thereservoir and in the buret are level.7.6 The gas bubble will be located adjacent to the stopcockvalve at the top of the capillary stem. Turn the valve clockwiseto the BLEED position (F) to permit a small amount of oi
35、l toenter the capillary stem from the flushing stem. This will lowerthe gas bubble in the capillary stem to a position where thestems bore is cylindrical and where the length of the bubblecan be easily read. Allow the bubble to reach a positionapproximately 25 mm below the cock and then turn the val
36、vecounterclockwise to the first OFF position (G).FIG. 3 Oil SamplerD 2945 90 (2003)e137.7 Measure the length of the gas bubble in the capillarystem. It is recommended that a scale be prepared, graduated in0.01-mL gas volume, and attached to the stem. For a stopcockof 2-mm nominal bore, 0.01-mL volum
37、e corresponds to alength of 4 mm.7.8 Move the mercury reservoir from position 2 to position1. Turn the valve clockwise to the BLEED position (H) andallow the oil to flush out into the waste beaker. When themercury touches the valve, turn the valve counterclockwise tothe first OFF position (I).7.9 Di
38、scard the first reading because it might be affected byresidual oil from previous tests. The average from at least twoadditional tests should be used to compute the gas content.8. Calculation8.1 Calculate the volume percent of gas as follows:V 5 G 3 100/Swhere:V = volume %, mL,G = volume of extracte
39、d gas, mL, andS = volume of oil sample, mL.9. Precision and Bias9.1 The precision and bias of this test method have not beendetermined due to the difficulty in obtaining a uniform set ofsamples for round-robin use.ASTM International takes no position respecting the validity of any patent rights asse
40、rted 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 subject to revision at any time by
41、 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 Headquarters. Your comments will recei
42、ve 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 is copyrighted by ASTM Inter
43、national, 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 2945 90 (2003)e14
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