ASTM D2685-11

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D2685 −11
Standard Test Method for
Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas
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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. Significance and Use
1.1 This test method covers the determination of air (Note
4.1 Air and carbon tetrafluoride (CF ) are two contaminants
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1) and carbon tetrafluoride as impurities in sulfur hexafluoride.
of interest in sulfur hexafluoride (SF ). Both of these contami-
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nants adversely affect the performance of SF when used as an
NOTE 1—Nitrogen, oxygen, or any of their mixtures is considered to be
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air. Commercial grade air or nitrogen is used for standardization. electrical insulating gas. Specification for maximum levels of
these contaminants are given in Specification D2472.
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
4.2 Gas chromatography is used to separate these contami-
standard.
nants from a sample of SF and to determine their concentra-
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1.3 This standard does not purport to address all of the
tion.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Apparatus
priate safety and health practices and determine the applica-
5.1 Gas Chromatograph, consisting of a sample inlet
bility of regulatory limitations prior to use.
system, adsorption column, flow meter, detector, and data
handling system. Ensure that the column material of construc-
2. Referenced Documents
tion and sample components are compatible. The apparatus
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2.1 ASTM Standards:
must completely separate air, carbon tetrafluoride, and sulfur
D2472 Specification for Sulfur Hexafluoride
hexafluoride as indicated by return of the recorded peak to the
E260 Practice for Packed Column Gas Chromatography
base line between each successive peak. Chromatograms must
E355 Practice for Gas Chromatography Terms and Relation-
be reproducible so that successive runs of a reference standard
ships
agree on each component peak area or height within 5 %. For
additional information on gas chromatography see Practices
3. Summary of Test Method
E260 and E355.
3.1 Air and carbon tetrafluoride are separated physically by
gas chromatography and compared to corresponding compo-
6. Reagents and Materials
nents separated under similar conditions from a reference
6.1 Cylinder of Helium Gas.
standard mixture of known composition. The individual com-
pounds of air are not separated.The composition of the sample
6.2 Reference Standard Mixture—A gas mixture that con-
is calculated from its chromatogram by comparing the area of
tains known percentages of air and carbon tetrafluoride in
the peak of each component with the area of the peak of the
helium or air and carbon tetrafluoride in sulfur hexafluoride is
corresponding component on the reference standard chromato-
required. The concentration of a component in the reference
gram.
sample should not be less than 50 % nor more than 300 % of
the concentration of the corresponding component in the
unknown.
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This test method is under the jurisdiction of ASTM Committee D27 Electrical
Insulating Liquids and Gases and is the direct responsibility of Subcommittee
7. Calibration and Standardization
D27.03 on Analytical Tests.
Current edition approved May 1, 2011. Published May 2011. Originally
7.1 ApparatusPreparation—Preparethegaschromatograph
approved in 1968. Last previous edition approved in 2003 as D2685 – 95(2003).
DOI: 10.1520/D2685-11.
for use as directed by the manufacturer. The following operat-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ing conditions have been found satisfactory. However, any
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
combination of conditions that result in complete separations
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. as indicated in the apparatus section will be satisfactory.
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D2685−11
Carrier gas helium, 40 to 50 mL/min
A 5 ~b 3h 3a!/n (1)
(
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
where:
Column temperature 40 to 50°C
A = average area of each component peak,
Detector temperature 70 to 80°C
b = peak width at half height,
Sample volume 2 to 5 mL approximately
Atten
...