1、Designation: D 4308 95 (Reapproved 2005)An American National StandardStandard Test Method forElectrical Conductivity of Liquid Hydrocarbons by PrecisionMeter1This standard is issued under the fixed designation D 4308; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in 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.This standard has been approved for use by agencies of the Department of Defense.1
3、. Scope1.1 This test method applies to the determination of the“rest” electrical conductivity of aviation fuels and other similarlow-conductivity hydrocarbon liquids in the range from 0.1 to2000 pS/m (see 3.2). This test method can be used in thelaboratory or in the field.1.2 The values stated in SI
4、 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 health
5、practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements, see 7.1.1 and 7.2.2. Referenced Documents2.1 ASTM Standards:2D 150 Test Methods for AC Loss Characteristics and Per-mittivity (Dielectric Constant) of Solid Electrical Insula-tionD 2624
6、 Test Methods for Electrical Conductivity of Avia-tion and Distillate FuelsD 4306 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-ity is
7、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 electrical cond
8、uctivity 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. The con
9、ductivity,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 due to han
10、dling 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 D 2624 which is limited to fuels containingstatic
11、 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 observed in c
12、ellcleaning 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 D 150.36. Apparatus6.1 Conductivity ApparatusComponents of the dc con-d
13、uctivity apparatus are shown in Fig. 1.41This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.J0 on Aviation Fuels.Current edition approved June 1, 2005. Published August 2005. Originallyapproved in 1
14、983. Last previous edition approved in 2000 as D 430895(2000)e1.2For 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 websi
15、te.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1241.4The KSLA Cell and Precision Conductivity Meter System, Emcee Model#1154 are available from Emcee Electronics, Inc., 520 Cypress Ave., Venice, FL34292.1Copyright ASTM I
16、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.1.1 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)
17、shield.6.1.2 The electrometer shown in Fig. 1 contains a batterywhich supplies a voltage to the 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,
18、 and fourrange selections.6.1.3 The cell and electrometer are connected by a triaxialcable as shown in Fig. 1.6.2 Thermometer, calibrated to 0.5C and conforming toSpecification E1.7. Reagents7.1 Cleaning SolventThe following may be used:7.1.1 Toluene-Isopropyl Alcohol Mixture(WarningFlammable. Vapor
19、 harmful. See Annex A1.1.) Mix two vol-umes of toluene and three volumes of isopropyl alcohol 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-hepta
20、ne through silica gel5as follows:7.2.1 Activate approximately 2000 g of 100 to 200 meshsilica 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 wool6for 24 h in clean n-heptane.7.2.2 Take a tube of borosilicate glass having
21、 an insidediameter of 60 to 70 mm, a length 1500 mm, with a conicallyshaped lower end provided 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
22、 to achievehomogeneous filling. The silica gel layer will be approximately1250 mm high. Wrap 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 sufficie
23、nt for the percolationof 1000 L of n-heptane, provided the conductivity of theuntreated n-heptane is below 1 pS/m.NOTE 2If the conductivity of the n-heptane after treatment, measuredin accordance with Section 11 in a thoroughly cleaned cell, is higher than0.1 pS/m, the treatment should be repeated.7
24、.3 Hydrocarbon, for calibration. The dielectric constantmust be known to 65 % at the temperature of calibration.78. Sampling8.1 The sample volume should be at least 0.7 L.5A suitable grade is available from W. R. Grace pipet instead.The sample should be clean and bright when tested.9. Preparation of
25、 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, the parts cleaned and the cell reassembled usin
26、gprotective 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-fluorocarbon insulator assembly.9.1.1.2 Each part
27、 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 After cleaning, check the cleanliness of the ce
28、ll 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 rinsedfive times with cleaning solvent, followed by
29、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 lower than 0.1pS/m.9.2 Cleaning of Auxiliary Eq
30、uipment: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 cell has been used to test samples of high-conduct
31、ivity,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.NOTE 6If testing is to be done on both low-conduct
32、ivity (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 pS/m after 3 s. If readingsexceed6 0.01 either
33、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 batteries should be replaced.10.2 Checking the Cell Con
34、stant:10.2.1 A check on the cell constant is necessary only if thecell has been damaged. Two capacitance measurements arerequired with a precision a-c bridge. Make a rigid two-terminalconnection between the cell assembly and the bridge. Measurethe total capacitance, CE(picofarad) of the empty assemb
35、ly.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 the actual capacitance, CA, of the emptycell as
36、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 constant cannot change signifi-cantly unless there
37、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 shouldindicate 1000 6 5.11.1.3 Rinse the cleaned cell thre
38、e times with the sample,empty completely, then fill the outer chamber until sampleoverflows into the center receptacle. (Alternatively, the outerchamber can be filled by pipet with 100 mL of sample).NOTE 7Static charges generated by handling the sample must beallowed to dissipate. If the sample is e
39、xpected to have a conductivitybelow 1 pS/m, 15-min waiting time must be allowed before reading.11.1.4 If the sample 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 appro
40、priate.D 4308 95 (2005)311.1.5 Using the AUTO mode, depress the appropriateRANGE switch. In the AUTO mode, the reading is stabilizedafter 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 temper
41、atureof the test samples to the nearest 1C with a clean thermometer.12. Calculation12.1 If the zero error in 10.1.2 was greater than 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:
42、Sample reading (11.1.5) 1.67Uncorrected zero error (10.1.2) + 0.03Calculated reading 1.6413. Report13.1 The report is to include 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 i
43、s recognized that the electrical conductivity of a fuel variessignificantly with temperature and that the relationship differs for varioustypes of aviation and distillate fuel. If it is necessary to correct conduc-tivity readings to a particular temperature, each laboratory would have toestablish th
44、is relationship for the fuels and temperature range of interest.14. Precision and Bias814.1 The precision of this test method obtained 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
45、9The data used to determine the precision of this test methodwere obtained using the auto mode.14.2 RepeatabilityThe difference between successive testresults obtained by the same operator with the same apparatusunder constant operating conditions on identical test sampleswould, in the long run, in
46、the normal and correct operation ofthe test method, exceed the values in Fig. 3 in only one case intwenty.14.3 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing at the same location on identical test materials would, in thelong run, exce
47、ed the values in Fig. 3 only in one case in twenty.14.3.1 In the event of a dispute or concern regardingshipped sample conductivity, it is recommended that operatorscome to the bulk hydrocarbon storage site to measure conduc-tivity on freshly obtained samples according to the citedprocedure. This en
48、sures 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 D 2624 wascarried out to investigate reproducibility of results when samples areshipped between laboratories.9While
49、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. The same possibility of conductivity changewould occur for samples tested according to Test Method D 4308.8Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1170.9Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:
