ASTM D2685-95(2003)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D2685 – 95 (Reapproved 2003)
Standard Test Method for
Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas
Chromatography
This standard is issued under the fixed designation D2685; 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.
1. Scope 4.2 Gas chromatography is used to separate these contami-
nants from a sample of SF and to determine their concentra-
1.1 This test method covers the determination of air (Note 6
tion.
1) and carbon tetrafluoride as impurities in sulfur hexafluoride.
NOTE 1—Nitrogen, oxygen, or any of their mixtures is considered to be 5. Apparatus
air. Commercial grade air or nitrogen is used for standardization.
5.1 Gas Chromatograph, consisting of a sample inlet sys-
1.2 This standard does not purport to address all of the
tem, adsorption column, flow meter, detector, and data han-
safety concerns, if any, associated with its use. It is the
dling system. Ensure that the column material of construction
responsibility of the user of this standard to establish appro-
and sample components are compatible. The apparatus must
priate safety and health practices and determine the applica-
completely separate air, carbon tetrafluoride, and sulfur
bility of regulatory limitations prior to use.
hexafluoride as indicated by return of the recorded peak to the
base line between each successive peak. Chromatograms must
2. Referenced Documents
be reproducible so that successive runs of a reference standard
2.1 ASTM Standards:
agree on each component peak area or height within 5 %.
D2472 Specification for Sulfur Hexafluoride
6. Reagents and Materials
3. Summary of Test Method
6.1 Cylinder of Helium Gas.
3.1 Air and carbon tetrafluoride are separated physically by
6.2 Reference Standard Mixture—A gas mixture that con-
gas chromatography and compared to corresponding compo-
tains known percentages of air and carbon tetrafluoride in
nents separated under similar conditions from a reference
helium or air and carbon tetrafluoride in sulfur hexafluoride is
standard mixture of known composition. The individual com-
required. The concentration of a component in the reference
pounds of air are not separated.The composition of the sample
sample should not be less than 50 % nor more than 300 % of
is calculated from its chromatogram by comparing the area of
the concentration of the corresponding component in the
the peak of each component with the area of the peak of the
unknown.
corresponding component on the reference standard chromato-
7. Calibration and Standardization
gram.
7.1 Apparatus Preparation—Prepare the gas chromato-
4. Significance and Use
graph for use as directed by the manufacturer. The following
4.1 Air and carbon tetrafluoride (CF ) are two contaminants
operating conditions have been found satisfactory. However,
of interest in sulfur hexafluoride (SF ). Both of these contami-
any combination of conditions that result in complete separa-
nants adversely affect the performance of SF when used as an
6 tions as indicated in the apparatus section will be satisfactory.
electrical insulating gas. Specification for maximum levels of
Carrier gas helium, 40 to 50 mL/min
these contaminants are given in Specification D2472. Column Porapak Q-80/100 mesh or Porapak R 50/80 mesh
Column size 6 to 10 Ft (2–3.5 m) by ¼ in. (6.4 mm) nominal
Column temperature 40 to 50°C
Detector temperature 70 to 80°C
This test method is under the jurisdiction of ASTM Committee D27 on
Sample volume 2 to 5 mL approximately
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
Attenuation lowest which will keep peaks on a scale may be varied
mittee D27.03 on Analytical Tests. during run
Current edition approved Oct. 1, 2003. Published November 2003. Originally Detector thermal conductivity
published as D2685 – 68. Last previous edition D2685 – 94. DOI: 10.1520/D2685-
7.2 ExampleofChromatographyConditions—Specific con-
95R03.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or ditions used by one laboratory which produces acceptable
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
chromatograms are as follows:
Standards volume information, refer to the standard’s Document Summary page on
Carrier gas helium, 50 mL/min
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D2685 – 95 (2003)
Column packing Porapak R 50/80 mesh
h = peak height above base line.
Column size and material 0.25 in. (6.4 mm) nominal ID,
a = attenuation,
10 ft (3.5 m) long, copper
n = number of peaks included in average, and
Column temperature 48°C
( = summation of the individual peak areas.
Detector thermal conductivity
Detector temperature 75°C
9.3 Calculate the concentration of each component in the
Sample volume 5 mL
sample as follows:
7.3 Reference Standard Introd
...