ASTM D4308-95(2005)
(Test Method)Standard Test Method for Electrical Conductivity of Liquid Hydrocarbons by Precision Meter
Standard Test Method for Electrical Conductivity of Liquid Hydrocarbons by Precision Meter
SIGNIFICANCE AND USE
The generation and dissipation of electrostatic charge in fuel due to handling depend largely on the ionic species present which may be characterized by the rest or equilibrium electrical conductivity. The time for static charge to dissipate is inversely related to conductivity. This test method can supplement Test Method D 2624 which is limited to fuels containing static dissipator additive.
Note 1—For low-conductivity fluids below 1 pS/m in conductivity, an ac measurement technique is preferable to a dc test method for sensing the electrical conductivity of bulk fluid. This dc test method can be used at conductivities from 0.1 to 1 pS/m if precautions are observed in cell cleaning and sample handling. A waiting period of 15 min is required after filling the cell before measuring dc conductivities below 1 pS/m. A single-laboratory program was conducted comparing this test method with ac Test Methods D 150.3
SCOPE
1.1 This test method applies to the determination of the "rest" electrical conductivity of aviation fuels and other similar low-conductivity hydrocarbon liquids in the range from 0.1 to 2000 pS/m (see 3.2). This test method can be used in the laboratory or in the field.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see 7.1.1 and 7.2.
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Standards Content (Sample)
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An American National Standard
Designation:D4308–95 (Reapproved 2005)
Standard Test Method for
Electrical Conductivity of Liquid Hydrocarbons by Precision
Meter
This standard is issued under the fixed designation D4308; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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.
212 21 21
1. Scope
1 pS/m 5 1 3 10 V m 51cu 5 1 picomho/m (1)
1.1 This test method applies to the determination of the
3.2 rest conductivity—the reciprocal of the resistance of
“rest”electricalconductivityofaviationfuelsandothersimilar
uncharged fuel in the absence of ionic depletion or polariza-
low-conductivity hydrocarbon liquids in the range from 0.1 to
tion. It is the electrical conductivity at the initial instant of
2000 pS/m (see 3.2). This test method can be used in the
current measurement after a d-c voltage is impressed between
laboratory or in the field.
electrodes.
1.2 The values stated in SI units are to be regarded as
4. Summary of Test Method
standard. No other units of measurement are included in this
standard.
4.1 A sample of liquid hydrocarbon is introduced into a
1.3 This standard does not purport to address all of the
clean conductivity cell which is connected in series to a battery
safety concerns, if any, associated with its use. It is the
voltage source and a sensitive dc ammeter. The conductivity,
responsibility of the user of this standard to establish appro-
automatically calculated from the observed peak current read-
priate safety and health practices and determine the applica-
ing dc voltage and cell constant using Ohm’s law, appears as a
bility of regulatory limitations prior to use. For specific
digital value in either a manual or automatic mode of meter
warning statements, see 7.1.1 and 7.2.
operation.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards: 5.1 The generation and dissipation of electrostatic charge in
D150 Test Methods for AC Loss Characteristics and Per-
fuelduetohandlingdependlargelyontheionicspeciespresent
mittivity (Dielectric Constant) of Solid Electrical Insula-
which may be characterized by the rest or equilibrium electri-
tion
cal conductivity. The time for static charge to dissipate is
D2624 TestMethodsforElectricalConductivityofAviation
inversely related to conductivity. This test method can supple-
and Distillate Fuels
ment Test Method D2624 which is limited to fuels containing
D4306 Practice for Aviation Fuel Sample Containers for
static dissipator additive.
Tests Affected by Trace Contamination
NOTE 1—For low-conductivity fluids below 1 pS/m in conductivity, an
E1 Specification for ASTM Liquid-in-Glass Thermometers
acmeasurementtechniqueispreferabletoadctestmethodforsensingthe
electrical conductivity of bulk fluid. This dc test method can be used at
3. Terminology
conductivities from 0.1 to 1 pS/m if precautions are observed in cell
3.1 picosiemens per metre—the unit of electrical conductiv-
cleaningandsamplehandling.Awaitingperiodof15minisrequiredafter
filling the cell before measuring dc conductivities below 1 pS/m. A
ity is also called a conductivity unit (CU). A siemen is the SI
single-laboratoryprogramwasconductedcomparingthistestmethodwith
definition of reciprocal ohm sometimes called mho.
ac Test Methods D150.
6. Apparatus
This test method is under the jurisdiction of ASTM Committee D02 on
6.1 Conductivity Apparatus—Components of the dc con-
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.J0 on Aviation Fuels.
ductivity apparatus are shown in Fig. 1.
Current edition approved June 1, 2005. Published August 2005. Originally
´1
approved in 1983. Last previous edition approved in 2000 as D4308–95(2000) .
DOI: 10.1520/D4308-95R05. Supporting data have been filed at ASTM International Headquarters and may
For referenced ASTM standards, visit the ASTM website, www.astm.org, or be obtained by requesting Research Report D02-1241.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM The KSLA Cell and Precision Conductivity Meter System, Emcee Model
Standards volume information, refer to the standard’s Document Summary page on #1154 are available from Emcee Electronics, Inc., 520 Cypress Ave., Venice, FL
the ASTM website. 34292.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4308–95 (2005)
FIG. 1 Precision Conductivity Meter
6.1.1 The conductivity cell shown in Fig. 1 consists of an desiccator under nitrogen or in vacuum. Soak approximately
inner electrode and an outer electrode separated by an insula- 0.5 g of glass wool for 24 h in clean n-heptane.
tor. The outer electrode and cap provide a ground path and 7.2.2 Take a tube of borosilicate glass having an inside
electrostatic (Faraday) shield. diameter of 60 to 70 mm, a length 1500 mm, with a conically
6.1.2 The electrometer shown in Fig. 1 contains a battery shaped lower end provided with a glass cock. Place a perfo-
which supplies a voltage to the cell and a bridge circuit which rated porcelain disk (diameter 25 mm) in the lower end of the
senses the flow of current and converts the output signal tube and put the soaked glass wool on top of the disk. Fill the
directly into conductivity units, that is, pS/m. A pushbutton tube with the activated silica gel while tapping to achieve
selector allows selection of zero reading, calibration, and four homogeneousfilling.Thesilicagellayerwillbeapproximately
range selections. 1250 mm high. Wrap the column in black paper to exclude
6.1.3 The cell and electrometer are connected by a triaxial light.
cable as shown in Fig. 1. 7.2.3 Percolate n-heptane through the column at a rate of
6.2 Thermometer, calibrated to 0.5°C and conforming to about 2 to 3 L/h. Discard the first 3 L. Never allow the column
Specification E1. to run dry.The silica gel charge is sufficient for the percolation
of 1000 L of n-heptane, provided the conductivity of the
7. Reagents
untreated n-heptane is below 1 pS/m.
7.1 Cleaning Solvent—The following may be used:
NOTE 2—If the conductivity of the n-heptane after treatment, measured
7.1.1 Toluene-Isopropyl Alcohol Mixture—(Warning—
in accordance with Section 11 in a thoroughly cleaned cell, is higher than
Flammable. Vapor harmful. See Annex A1.1.) Mix two vol-
0.1 pS/m, the treatment should be repeated.
umesoftolueneandthreevolumesofisopropylalcoholbothof
7.3 Hydrocarbon, for calibration. The dielectric constant
reagent grade and distill. Discard the first 20 % and last 5 %
must be known to 65 % at the temperature of calibration.
fractions.
7.2 n-Heptane—(Warning—Flammable. Harmful if in-
8. Sampling
haled. See Annex A1.2.) Prepare by percolating ASTM refer-
5 8.1 The sample volume should be at least 0.7 L.
ence fuel grade n-heptane through silica gel as follows:
7.2.1 Activate approximately 2000 g of 100 to 200 mesh
silica gel by heating at 180°C for 24 h. Allow it to cool in a
A suitable product is filtering fiber Pyrex Wool. Catalogue No. 3950, supplied
by Owens-Corning Fiber Glass Corp.
5 7
A suitable grade is available from W. R. Grace & Co., Davison Chemical A standard, such as cyclohexane, with certified dielectric constant, may be
Division, Baltimore, MD 21202 by specifying Code 923. obtained from the National Bureau of Standards, Washington, DC 20234.
D4308–95 (2005)
cleaning.Verythoroughcleaningmayalsobeaccomplishedbyplacingthe
8.2 Use a clean epoxy-lined can, or a new glass bottle that
disassembled cell in a Soxhlet apparatus containing boiling toluene/
has been rinsed successively with hot water, distilled water,
isopropyl alcohol for several hours.
acetone, and cleaning solvent then flush with dry nitrogen. Use
NOTE 6—If testing is to be done on both low-conductivity (<1 pS/m)
only non-contaminating caps.
and high-conductivity (>1000 pS/m) samples, separate cells are recom-
NOTE 3—Test method results are known to be sensitive to trace mended.
contamination from sampling containers. For recommended sampling
containers refer to Practice D4306. 10. Calibration and Standardization
NOTE 4—Bottle samples should be tested immediately, since the glass
10.1 Checking the Test Equipment:
surface tends to absorb from the fuel the conductive substances that the
10.1.1 Remove cell and cable from the meter.
test method is intended to measure.
10.1.2 Depress the 20-pS/m switch. The digital reading
8.3 Rinse the container several times with portions of the
should indicate 0.00 6 0.01 pS/m after 3 s. If readings
aviation turbine fuel to be sampled (JetAorA-1, (Warning—
exceed6 0.01 either adjust zero or record the zero error for
Combustible. Vapor harmful. See Annex A1.3.), Jet B
calculating final report value.
(Warning—Extremely flammable. Harmful if inhaled. Vapors
10.1.3 Depress the calibrate switch. The digital reading
can cause flash fire. See Annex A1.4). If possible fill the
should indicate 1000 6 3 pS/m.
container, let stand, then empty and refill. Avoid taking the
10.1.4 If low battery indicator is displayed during measure
sample for test by pouring from the container; pipet instead.
or calibration, the internal batteries should be replaced.
The sample should be clean and bright when tested.
10.2 Checking the Cell Constant:
10.2.1 A check on the cell constant is necessary only if the
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