1、Designation: D 1827 92 (Reapproved 2002)Standard Test Method forGas Content (Nonacidic) of Insulating Liquids byDisplacement with Carbon Dioxide1This standard is issued under the fixed designation D 1827; the number immediately following the designation indicates the year oforiginal adoption or, in
2、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 describes the determination of the gascontent of electrical insula
3、ting liquids with a viscosity of 216cSt or less at 100C. Any gas that is nonreactive with a strongcaustic solution may be determined.NOTE 1The test method has a bias for samples containing gases otherthan oxygen and nitrogen in atmospheric ratios due to differentialsolubility effects. Gases which re
4、act with KOH such as carbon dioxidewill not be measured. Unsaturated hydrocarbons such as acetylene, ifpresent, will react with KOH to a small degree and will result in anunderestimation of the total gas present.1.2 This standard does not purport to address all of thesafety concerns, if any, associa
5、ted 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 prior to use.2. Referenced Documents2.1 ASTM Standards:D 831 Test Method for Gas Content of Cable and CapacitorOils2
6、D 923 Practices for Sampling Electrical Insulating Liquids2D 1193 Specification of Reagent Water3D 3613 Practice for Insulating Liquids for Gas Analysis andDetermination of Water Content23. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 gas content by volumeof an insulating liqu
7、id, thevolume of gas contained in a given volume of liquid. It isusually expressed as a percentage at standard atmosphericconditions of 760 mm Hg pressure and 0C temperature.3.1.2 gas content by weightthe weight of gas contained ina given weight of liquid, usually expressed in parts per million.4. S
8、ummary of Test Method4.1 This test method consists essentially of purging dis-solved gases from a small liquid test specimen with purecarbon dioxide gas. The dissolved gases are then carried into agraduated buret (precision nitrometer) filled with a potassiumhydroxide solution for a precise measurem
9、ent. The carbondioxide is completely absorbed by the potassium hydroxideand the volume of other gases is measured.5. Significance and Use5.1 Electrical insulating liquids, in many applications, re-quire low gas content. This is the case with capacitors andcertain types of cable, for example. This te
10、st is used as afactory control test and as a control and functional test ininstallation and maintenance work by utilities. This test re-quires care in manipulation and trained, careful personnel.6. Apparatus (see Fig. 1)6.1 Precision Nitrometer (azotometer), A, with a calibratedcapacity of 1.5 mL an
11、d calibrated in 0.01-mL divisions.Nitrometers shall have individual calibration correction tablesthat give the correct volume for each 0.01-mL point on thescale when a 40 % aqueous potassium hydroxide solution isused. The gas inlet shall consist of a 12/2 socket joint. Thenitrometer shall be provide
12、d with a liquid leveling bulb, B,of125-mL capacity. Rubber stoppers, K, with a short piece ofglass capillary tubing, should be placed in the top of thenitrometer and the leveling bulb, B, to prevent spattering of theKOH solution.6.2 Permanent Magnet and Steel Wire, The small steel wire,suitably cons
13、isting of a38-in. (10-mm) length of paper clip,shall be placed inside the nitrometer for manipulation by thesmall external permanent magnet.6.3 Pregl-Type Micro Stopcock, C, to allow delivery of gasto nitrometer or venting the gas to the atmosphere. Thisstopcock shall be provided with a 12/2 ball jo
14、int at the exit sideand a 12/2 socket joint at the inlet side.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-mittee D27.03on Physical Tests.Current edition approved Aug. 15, 1992. Published October
15、 1992. Originallypublished as D 1827 61 T. Last previous edition D 1827 84.2Annual Book of ASTM Standards, Vol 10.03.3Annual Book of ASTM Standards, Vol 11.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.4 Elbow Adapter, D, cons
16、isting of a 12/2 ball joint andhaving a drawn-down tip suitable for insertion in a small holein the rubber stopper, E.6.5 Stopper, E, of oil-resistant rubber, cut to fit the sample-purging chamber, F, and provided with two small holes toallow tight fitting of the elbow adapter, D, and sample deliver
17、ytube, G.6.6 Sample-Purging Chamber, F, with a 10-mm diameterfritted-glass disk, L, of medium porosity and a capacity of 15mL above the disk for 10-mL test specimens, or with a 25-mmdiameter fritted glass disk of medium porosity and a capacityof 75 mL above the disk for 50-mL test specimens. The gas
18、inlet shall be cut straight to fit the stopper, E. A flexible heatingtape, wrapped around the purging chamber, is necessary forholding constant temperature when test specimens are purgedat temperatures in excess of room temperature.6.7 Sample Delivery Tube, G, made of a length of116-in.(1.6-mm) insi
19、de diameter stainless steel tubing, tightly insertedinto one of the holes in the stopper, E, and extending to thefritted-glass filter. A small syringe stopcock shall be soldered topermit the delivery of an accurate volume of liquid andsubsequent sealing of the purging chamber.6.8 Sampling Device, co
20、nsisting of a calibrated glass medi-cal syringe fitted with a syringe stopcock for sealing of the testspecimen during transfer or storage. The syringe for 10-mL testspecimens shall have a calibrated capacity of 10 mL, and for50-mL test specimens, a calibrated capacity of 50 mL. It shallbe capable of
21、 accurately delivering a liquid volume within theaccuracy required for the method.6.9 Ball-and-Socket Clamps, size 12, for tightly securing alljoints to prevent leakage.6.10 Two-Way Stopcock, H, fitted to the inlet side of thepurging chamber and having a 12/2 socket joint. The single-tube end of the
22、 stopcock shall be connected to the low-pressurecarbon dioxide supply to control the entry of this gas to theapparatus.6.11 Low-Pressure Source of very pure carbon dioxide(CO2) gas.4If gas of sufficient purity is not available, one ofthe following mechanisms utilizing solid CO2shall be used:6.11.1 A
23、 high-pressure cylinder having an opening largeenough to insert pieces of solid CO2and capable of withstand-ing 800 to 1000 psi (5.5 to 7 MPa) pressure when the solidevaporates. The cylinder should be provided with a pressure-reduction valve capable of delivering gas at a gage pressure aslow as 3 to
24、 5 psi (20 to 34 kPa). A pressure-relief valve set atabout 1200 psi (8 MPa) should be included, and care should beexercised to limit the quantity of solid CO2placed in thecylinder due to the greater volume occupied by the gas.6.11.2 A vacuum bottle that can be charged with solid CO2.The bottle may b
25、e closed with a large rubber stopper fitted witha pressure-bleed regulator, a mercury relief valve, a nichromeheating element, and a gas delivery tube to the apparatus.4Cylinders of 99.99 % minimum purity liquified carbon dioxide fitted with twostage regulator with stainless steel diaphragms have be
26、en found satisfactory.Cylinders of “Instrument Grade” carbon dioxide and regulators (Model No. 18-5,CGA 320) may be obtained from BOC Gases Customer Service Center, 100Corporate Drive, Lebanon, NJ 08833.FIG. 1 Semimicro Apparatus for Determination of Gas Content of Insulating LiquidsD 1827 92 (2002)
27、26.11.3 A 12-qt (12-L) aluminum pressure cooker that can becharged with solid CO2. It should be fitted with a suitablepressure-relief device and gas delivery tube. A minimum lengthof heavy-wall rubber or plastic tubing should be used inconnecting the source of CO2gas to the purging chamber.6.12 All
28、glass shall be heat- and chemical-resistant. Capil-lary tubing should be used wherever possible to minimize theamount of purging necessary to remove air from the apparatus.6.13 An auxiliary source of vacuum, with trap, to facilitateremoval of spent test specimen, is optional.7. Reagents and Material
29、s7.1 Purity of ReagentsUse reagent grade chemicals in alltests. Unless otherwise indicated, it is intended that all reagentsconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society, where suchspecifications are available.5Other grades may be used, pro-vid
30、ed it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type III of Specification D 1193.7.3
31、 Carbon Dioxide (CO2)Solid carbon dioxide (dry ice)for producing CO2of high purity.7.4 Potassium Hydroxide Solution (40 %)Dissolve 572 gof potassium hydroxide (KOH) in water and dilute to 1 L.7.5 Stopcock Grease that is resistant to KOH and the oilsample.8. Sampling8.1 When convenient, connect the s
32、ample delivery tube ofthe measuring apparatus directly to the container from whichthe liquid is to be sampled. This is usually not convenient andis often impossible. The methods described in 8.2 to 8.5 arerecommended as alternatives.8.2 For sampling liquid at or below the gas saturation point,a syri
33、nge and stopcock may be used in accordance withPractice D 3613.8.3 For liquids that are sampled under pressure or that aresupersaturated with a gas, follow the same procedure asdescribed in 8.2, except that after sealing off the sample apressure device is required to maintain a solution of the gas i
34、nthe liquid. Any spring mechanism that can be built around thesyringe is suitable, and the tension required will depend uponthe pressure required to maintain solution.8.4 Use 10 mL test specimens, except where it is desirableto increase the precision of the test. On samples having a gascontent of 1
35、% or less, 25 to 50-mL test specimens aredesirable.8.5 The sample container and method for sampling liquidsfor the determination of gas content in Test Methods D 831 andPractice D 3613 have been found satisfactory and convenientfor obtaining samples in the field. This sample container hasbeen found
36、satisfactory for storing oil samples with a low gascontent for a week or more. Transfer the test specimen to thesample delivery tube of the measuring apparatus with asyringe.9. Preparation of Apparatus9.1 Fill the bottom portion of the nitrometer, A, withmercury to a point about 5 to 7 mm above the
37、gas entrycapillary. The mercury acts as a valve to allow the gas tobubble into the buret and also to prevent the KOH solutionfrom flowing into the system due to gravity. Place a38-in.(10-mm) piece of steel wire on the mercury.9.2 Open stopcock J and add KOH solution to the levelingbulb, B, until the
38、re are 20 or 30 mm of KOH solution above thestopcock, J, with the solution in the leveling bulb at the samelevel. Remove all bubbles from the nitrometer, using the steelwire and magnet.9.3 The system must be kept completely leak-free, sinceeven small leaks allow diffusion of air into the apparatus a
39、ndcause indeterminate errors. Leakage can easily be detected inthe purging operation. If leakage occurs, check all joints andconnections. Carbon dioxide of insufficient purity has the sameeffect as leaks.10. Procedure10.1 Close stopcock J, adjust stopcock C to allow gas toflow from the purging chamb
40、er to the atmosphere, and turnstopcock H to the vent position. Connect the syringe to thesample delivery tube, G, flush with 1 to 2 mL of the sample,and close the syringe or delivery tube stopcock. Reversestopcock H slowly, and flush the purging chamber with CO2for2 to 5 min. Divert the gas into the
41、 nitrometer with stopcock C,and allow it to flow for 10 to 15 s. If gas bubbles continue torise to the top of the nitrometer, again flush the purgingchamber. After completion of the purging, gas bubbles shouldcontinue to form just above the mercury in the nitrometer andrapidly decrease to micro size
42、 near the top of the KOHsolution, but there should not be sufficient unabsorbed gas tolower the level of the solution. If this condition does not exist,either repeat purging or replace the spent solution until nochange is noted.10.2 Make certain that the nitrometer is completely filledwith KOH solut
43、ion, that there are 20 to 30 mm of solutionabove stopcock J, and that the stopcock J is closed; then lowerthe leveling bulb to about the center of the calibrated portion ofthe nitrometer. Close stopcock C, vent H, open the stopcocksbetween the syringe and purging chamber F, and introduce ameasured t
44、est specimen of liquid. Ten-millilitre test specimenshave been found satisfactory for oils with a gas content of 1 %or more. For liquids with a gas content of less than 1 %, the useof 50-mL samples will increase the precision by a factor of 5.The introduction of test specimens of the more viscous li
45、quidsmay be accelerated by preheating the sampling device to someknown temperature from 40 to 100C. Record the temperatureand volume or weight of the liquid test specimen.10.3 Close stopcock G, then open stopcocks C and H toallow CO2to bubble through the sample into the nitrometerwith 1 to 5 bubbles
46、 a second in the nitrometer. Initially, the5“Reagent Chemicals, American Chemical Society Specifications,” Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing not listed by the AmericanChemical Society, see “Reagent Chemicals and Standards,” by Joseph Rosin, D. VanNostrand Co., Inc.,
47、New York, NY, and the “United States Pharmacopeia.”D 1827 92 (2002)3CO2may rapidly dissolve in the liquid and no bubbles willappear in the nitrometer, but in time the gas bubbles will beginto appear. Purging the test specimens requires about 10 min, ormore for higher viscosity liquids, and the end p
48、oint is reachedwhen the dissolved gases are completely removed and onlymicro bubbles appear at the top of the nitrometer. The purgingof the higher viscosity liquids may be accelerated by maintain-ing the purging chamber at some temperature between 40 and100C. This temperature need not be accurately
49、controlled.When the volume of gas in the nitrometer shows no furtherchange, vent stopcocks C and H to the atmosphere. Makecertain that all of the gas is above the KOH solution in thenitrometer, using the magnet and steel wire if necessary.10.4 After allowing sufficient time for drainage of thenitrometer, hold the liquid in the leveling bulb at the level ofthe liquid in the nitrometer column, and read and record thevolume of gas in the nitrometer to the nearest 0.005 mL.10.5 Run a blank test immediately after completing thesample analysis, for an equivalent period of t
