1、Designation: D4308 95 (Reapproved 2010)An American National StandardStandard Test Method forElectrical Conductivity of Liquid Hydrocarbons by PrecisionMeter1This standard is issued under the fixed designation D4308; the number immediately following the designation indicates the year oforiginal adopt
2、ion or, in the case of revision, 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.This standard has been approved for use by agencies of the Department of Defense.1. S
3、cope1.1 This test method covers and applies to the determinationof the “rest” electrical conductivity of aviation fuels and othersimilar low-conductivity hydrocarbon liquids in the range from0.1 to 2000 pS/m (see 3.2). This test method can be used in thelaboratory or in the field.1.2 The values stat
4、ed in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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 appro-priate safety and
5、 health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements, see 7.1.1, 7.2, and 8.3.2. Referenced Documents2.1 ASTM Standards:2D150 Test Methods for AC Loss Characteristics and Per-mittivity (Dielectric Constant) of Solid Electrical Insu
6、la-tionD2624 Test Methods for Electrical Conductivity ofAviationand Distillate FuelsD4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationE1 Specification for ASTM Liquid-in-Glass Thermometers3. Terminology3.1 picosiemens per metrethe unit of electrical conductiv
7、-ity is also called a conductivity unit (CU). A siemen is the SIdefinition of reciprocal ohm sometimes called mho.1 pS/m 5 1 3 10212V21m215 1cu5 1 picomho/m (1)3.2 rest conductivitythe reciprocal of the resistance ofuncharged fuel in the absence of ionic depletion or polariza-tion. It is the electri
8、cal conductivity at the initial instant ofcurrent measurement after a d-c voltage is impressed betweenelectrodes.4. Summary of Test Method4.1 A sample of liquid hydrocarbon is introduced into aclean conductivity cell which is connected in series to a batteryvoltage source and a sensitive dc ammeter.
9、 The conductivity,automatically calculated from the observed peak current read-ing dc voltage and cell constant using Ohms law, appears as adigital value in either a manual or automatic mode of meteroperation.5. Significance and Use5.1 The generation and dissipation of electrostatic charge infuel du
10、e to handling depend largely on the ionic species presentwhich may be characterized by the rest or equilibrium electri-cal conductivity. The time for static charge to dissipate isinversely related to conductivity. This test method can supple-ment Test Method D2624 which is limited to fuels containin
11、gstatic dissipator additive.NOTE 1For low-conductivity fluids below 1 pS/m in conductivity, anac measurement technique is preferable to a dc test method for sensing theelectrical conductivity of bulk fluid. This dc test method can be used atconductivities from 0.1 to 1 pS/m if precautions are observ
12、ed in cellcleaning and sample handling.Awaiting period of 15 min is required afterfilling the cell before measuring dc conductivities below 1 pS/m. Asingle-laboratory program was conducted comparing this test method withac Test Methods D150.31This test method is under the jurisdiction of ASTM Commit
13、tee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.J0.04 on Additives and Electrical Properties.Current edition approved Feb. 15, 2010. Published March 2010. Originallyapproved in 1983. Last previous edition approved in 2005 as D430895 (2005).DOI: 10.1520
14、/D4308-95R10.2For 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.3Supporting data have been filed at ASTM Interna
15、tional Headquarters and maybe obtained by requesting Research Report RR:D02-1241.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Apparatus6.1 Conductivity ApparatusComponents of the dc con-ductivity apparatus are shown in Fig. 1.4
16、,56.1.1 The conductivity cell shown in Fig. 1 consists of aninner electrode and an outer electrode separated by an insula-tor. The outer electrode and cap provide a ground path andelectrostatic (Faraday) shield.6.1.2 The electrometer shown in Fig. 1 contains a batterywhich supplies a voltage to the
17、cell and a bridge circuit whichsenses the flow of current and converts the output signaldirectly into conductivity units, that is, pS/m. A pushbuttonselector allows selection of zero reading, calibration, and fourrange selections.6.1.3 The cell and electrometer are connected by a triaxialcable as sh
18、own in Fig. 1.6.2 Thermometer, calibrated to 0.5C and conforming toSpecification E1.7. Reagents7.1 Cleaning Solvent, The following may be used:7.1.1 Toluene-Isopropyl Alcohol Mixture(WarningFlammable. Vapor harmful. See Annex A1.1.) Mix two vol-umes of toluene and three volumes of isopropyl alcohol
19、both ofreagent grade and distill. Discard the first 20 % and last 5 %fractions.7.2 n-Heptane(WarningFlammable. Harmful if in-haled. See Annex A1.2.) Prepare by percolating ASTM refer-ence fuel grade n-heptane through silica gel5,6as follows:7.2.1 Activate approximately 2000 g of 100 to 200 meshsilic
20、a gel by heating at 180C for 24 h. Allow it to cool in adesiccator under nitrogen or in vacuum. Soak approximately0.5 g of glass wool5,7for 24 h in clean n-heptane.7.2.2 Take a tube of borosilicate glass having an insidediameter of 60 to 70 mm, a length 1500 mm, with a conicallyshaped lower end prov
21、ided with a glass cock. Place a perfo-rated porcelain disk (diameter 25 mm) in the lower end of thetube and put the soaked glass wool on top of the disk. Fill thetube with the activated silica gel while tapping to achievehomogeneous filling. The silica gel layer will be approximately1250 mm high. Wr
22、ap the column in black paper to excludelight.7.2.3 Percolate n-heptane through the column at a rate ofabout 2 to 3 L/h. Discard the first 3 L. Never allow the columnto run dry. The silica gel charge is sufficient for the percolationof 1000 L of n-heptane, provided the conductivity of theuntreated n-
23、heptane is below 1 pS/m.4The sole source of supply of the apparatus, the KSLA Cell and PrecisionConductivity Meter System, Emcee Model #1154, known to the committee at thistime is Emcee Electronics, Inc., 520 Cypress Ave., Venice, FL 34285.5If you are aware of alternative suppliers, please provide t
24、his information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.6The sole source of supply known to the committee at this time is Code 923,from W. R. Grace pipet instead.The sample should b
25、e clean and bright when tested.9. Preparation of Apparatus9.1 Cleaning the CellThe cleaning procedure to be useddepends on the estimated conductivity of the sample to betested.9.1.1 For samples that are expected to exhibit conductivitiesbelow 1 pS/m, the KSLA cell should be completely disas-sembled,
26、 the parts cleaned and the cell reassembled usingprotective gloves.9.1.1.1 Dismantle the cell by removing the loose batterycap, the outer electrode electrical connector and the bottomscrew-on cap. Press the inner electrode towards the bottom ofthe outer electrode and remove the inner electrode TFE-f
27、luorocarbon insulator assembly.9.1.1.2 Each part of the cell should be rinsed thoroughly fivetimes with cleaning solvent followed by rinsing with treatedn-heptane. The parts should be dried with a stream of nitrogengas.9.1.1.3 After reassembly, the cell should be rinsed withtreated n-heptane.9.1.1.4
28、 After cleaning, check the cleanliness of the cell bymeasuring the conductivity of treated n-heptane in accordancewith Section 11. The corrected value should be lower than 0.05pS/m.9.1.2 For samples that are expected to exhibit conductivitiesabove 1 pS/m, the KSLA cell still assembled should be rins
29、edfive times with cleaning solvent, followed by rinsing withtreated n-heptane. The cell should be dried with a stream ofnitrogen gas.9.1.2.1 After cleaning, check the cleanliness of the cell bymeasuring the conductivity of treated n-heptane in accordancewith Section 11. The corrected value should be
30、 lower than 0.1pS/m.9.2 Cleaning of Auxiliary Equipment:9.2.1 Pipets used to transfer samples should be rinsed insideand outside with cleaning solvent using a non-contaminatingsqueeze bottle, then blown dry with clean, dry nitrogen.Thermometers should be similarly rinsed and maintained.NOTE 5If a ce
31、ll has been used to test samples of high-conductivity,that is, more than 1000 pS/m, it should be disassembled for thoroughcleaning. Very thorough cleaning may also be accomplished by placing thedisassembled cell in a Soxhlet apparatus containing boiling toluene/isopropyl alcohol for several hours.NO
32、TE 6If testing is to be done on both low-conductivity (1000 pS/m) samples, separate cells are recom-mended.10. Calibration and Standardization10.1 Checking the Test Equipment:10.1.1 Remove cell and cable from the meter.10.1.2 Depress the 20-pS/m switch. The digital readingshould indicate 0.00 6 0.01
33、 pS/m after 3 s. If readingsexceed6 0.01 either adjust zero or record the zero error forcalculating final report value.10.1.3 Depress the calibrate switch. The digital readingshould indicate 1000 6 3 pS/m.10.1.4 If low battery indicator is displayed during measureor calibration, the internal batteri
34、es should be replaced.10.2 Checking the Cell Constant:10.2.1 A check on the cell constant is necessary only if thecell has been damaged. Two capacitance measurements arerequired with a precision ac bridge. Make a rigid two-terminalconnection between the cell assembly and the bridge. Measurethe total
35、 capacitance, CE(picofarad) of the empty assembly.Without disturbing the connection, add 100 mL of a hydrocar-bon standard and measure the new total capacitance, CS(picofarad) and the temperature in the cell. Alternatively, thecell can be sent to the manufacturer for recalibration.10.2.2 Calculate t
36、he actual capacitance, CA, of the emptycell as follows:CA5 CS2 CE!/k21! (2)where:k = dielectric constant of the hydrocarbon at test tempera-tures.10.2.3 Calculate the cell constant as follows:K 5 8.854/CA(3)10.2.4 The cell constant of a new KSLAcell is 1.0. Becauseof its configuration, the cell cons
37、tant cannot change signifi-cantly unless there is gross damage.11. Procedure11.1 Attach the cleaned cell to the meter as shown in Fig. 2.11.1.1 Depress the ZERO switch, the digital reading shouldindicate the same value recorded in 10.1.2.11.1.2 Depress the CAL switch, the digital reading shouldindic
38、ate 1000 6 5.8A standard, such as cyclohexane, with certified dielectric constant, may beobtained from the National Bureau of Standards, Washington, DC 20234.D4308 95 (2010)311.1.3 Rinse the cleaned cell three times with the sample,empty completely, then fill the outer chamber until sampleoverflows
39、into the center receptacle. (Alternatively, the outerchamber can be filled by pipet with 100 mL of sample).NOTE 7Allow static charges generated by handling the sample todissipate. If the sample is expected to have a conductivity below 1 pS/m,allow 15-min waiting time before reading.11.1.4 If the sam
40、ple conductivity is known, select thecorresponding range position. When the conductivity is un-known, first check the fuel on a 2000 pS/m range position, thenread in a lower scale if appropriate.11.1.5 Using the AUTO mode, depress the appropriateRANGE switch. In the AUTO mode, the reading is stabili
41、zedafter 3 s and held on display for 9 s. Record the pS/m value.11.1.6 Repeat readings can be taken after a 1-min delay.11.1.7 Remove the cell cover and measure the temperatureof the test samples to the nearest 1C with a clean thermometer.12. Calculation12.1 If the zero error in 10.1.2 was greater t
42、han 6 0.01 andthe zero of the meter was not adjusted, the readings should becorrected by subtracting any positive zero error or adding anynegative zero error. For example:Sample reading (11.1.5) 1.67Uncorrected zero error (10.1.2) + 0.03Calculated reading 1.6413. Report13.1 The report is to include
43、the following:13.1.1 The calculated conductivity of the sample in pS/mafter correcting for the zero reading. Note MANUAL orAUTOmode.13.1.2 Temperature of sample.NOTE 8It is recognized that the electrical conductivity of a fuel variessignificantly with temperature and that the relationship differs fo
44、r varioustypes of aviation and distillate fuel. If it is necessary to correct conduc-tivity readings to a particular temperature, each laboratory would have toestablish this relationship for the fuels and temperature range of interest.14. Precision and Bias914.1 The precision of this test method obt
45、ained by statisticalexamination of test results in the range between 0.1 and 2000pS/m by operator/instrument pairs at a common test site isdescribed in 14.2 and 14.3.NOTE 9The data used to determine the precision of this test methodwere obtained using the auto mode.14.2 RepeatabilityThe difference b
46、etween successive testresults obtained by the same operator with the same apparatusunder constant operating conditions on identical test sampleswould, in the long run, in the normal and correct operation ofthe test method, exceed the values in Fig. 3 in only one case intwenty.14.3 ReproducibilityThe
47、 difference between two singleand independent results obtained by different operators work-ing at the same location on identical test materials would, in thelong run, exceed the values in Fig. 3 only in one case in twenty.14.3.1 In the event of a dispute or concern regardingshipped sample conductivi
48、ty, it is recommended that operatorscome to the bulk hydrocarbon storage site to measure conduc-tivity on freshly obtained samples according to the cited9Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1170.FIG. 2 Cleaned Cel
49、l Attached to MeterD4308 95 (2010)4procedure. This ensures that samples identical to bulk storageare tested by either or both parties and the precision data in Fig.3 shall apply (Note 10).NOTE 10In 1987, a test program using Test Method D2624 wascarried out to investigate reproducibility of results when samples areshipped between laboratories.10While repeatability values were similar tothose from common site testing, it was concluded that adequate reproduc-ibility values were not obtained due to changes in conductivity of samplesduring shipment and storage. T
