ASTM D2685-11(2019)

Standard Test Method for Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas Chromatography

SIGNIFICANCE AND USE
4.1 Air and carbon tetrafluoride (CF4) are two contaminants of interest in sulfur hexafluoride (SF6). Both of these contaminants adversely affect the performance of SF6 when used as an electrical insulating gas. Specification for maximum levels of these contaminants are given in Specification D2472.  
4.2 Gas chromatography is used to separate these contaminants from a sample of SF6 and to determine their concentration.
SCOPE
1.1 This test method covers the determination of air (Note 1) and carbon tetrafluoride as impurities in sulfur hexafluoride.  
Note 1: Nitrogen, oxygen, or any of their mixtures is considered to be air. Commercial grade air or nitrogen is used for standardization.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2019
• ICS: 71.060.50 - Salts
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.03 - Analytical Tests

Relations

• Replaces: ASTM D2685-11 - Standard Test Method for Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas Chromatography
• Effective Date: 01-Oct-2019
• Refers: ASTM D2472-15(2023) - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Dec-2023
• Refers: ASTM E260-96(2019) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Sep-2019
• Refers: ASTM D2472-15 - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Oct-2015
• Refers: ASTM D2472-00(2014) - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Nov-2014
• Refers: ASTM E260-96(2011) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Nov-2011
• Refers: ASTM E355-96(2007) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Mar-2007
• Refers: ASTM D2472-00(2006) - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Apr-2006
• Refers: ASTM E260-96(2006) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Mar-2006
• Refers: ASTM E355-96(2001) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96 - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96(2001) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001
• Refers: ASTM E355-96 - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM D2472-00 - Standard Specification for Sulfur Hexafluoride
• Effective Date: 10-Apr-2000

Overview

ASTM D2685-11(2019) is a widely recognized international standard developed by ASTM International. It specifies the test method for determining air and carbon tetrafluoride (CF4) impurities in sulfur hexafluoride (SF6) using gas chromatography. SF6 is commonly used as an electrical insulating gas in high-voltage equipment, and the presence of air and CF4 as impurities can significantly affect its insulating performance. This standard provides a uniform, reliable approach to quantifying these contaminants, ensuring that SF6 meets the required purity levels for safe and effective application.

Key Topics

• Purpose of the Test Method: Detects and quantifies air (nitrogen, oxygen, or their mixtures) and carbon tetrafluoride present as impurities in SF6 gas.
• Gas Chromatography Technique: Utilizes gas chromatography for separating and measuring contaminant concentrations, with helium commonly used as a carrier gas.
• Sample Analysis and Calibration: Involves comparing chromatographic results to reference standards with known concentrations for accurate impurity measurement.
• Equipment and Setup:
  • Gas chromatograph fitted with an appropriate column and detector
  • Calibration using commercial grade air or nitrogen, and reference gas mixtures
• Reporting and Units: Results are expressed in SI units, typically in weight percent or parts per million (ppm).
• Quality Assurance: Emphasizes repeatability and consistency, with defined thresholds for acceptable variance in repeated tests within the same laboratory.

Applications

ASTM D2685-11(2019) is essential for industries and laboratories where SF6 is used as an insulating material, primarily in the electrical power sector. Its key applications include:

• Quality Control in SF6 Production: Ensures that manufactured SF6 meets purity specifications for air and CF4 content, preventing equipment malfunction or failure.
• Acceptance Testing of SF6 Bulk Deliveries: Used by gas suppliers and end-users to verify gas quality before use in critical high-voltage systems.
• Routine Monitoring and Maintenance: Supports preventative maintenance by identifying contaminants in SF6 used in circuit breakers, transformers, and gas-insulated switchgear.
• Regulatory Compliance: Aids in meeting industry and government requirements for safe handling and environmental protection regarding greenhouse gases.
• Laboratory Analytical Procedures: Serves as a benchmark for laboratories standardizing their gas chromatographic methods for SF6 analysis.

Related Standards

For organizations implementing ASTM D2685-11(2019), familiarity with the following related standards is recommended:

• ASTM D2472: Specification for Sulfur Hexafluoride, establishing maximum allowable impurity levels.
• ASTM E260: Practice for Packed Column Gas Chromatography, offering additional guidance on gas chromatographic methods.
• ASTM E355: Practice for Gas Chromatography Terms and Relationships, clarifies terminology and measurement relationships in gas chromatography.

Keywords: ASTM D2685, sulfur hexafluoride analysis, SF6 impurities, gas chromatography, carbon tetrafluoride detection, air in SF6, insulating gas quality, laboratory gas analysis, electrical insulation standards.

By adhering to ASTM D2685-11(2019), stakeholders can ensure that SF6 used in electrical and industrial applications meets stringent quality and safety standards, enhancing operational reliability and compliance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D2685 −11 (Reapproved 2019)
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 pounds of air are not separated.The composition of the sample
is calculated from its chromatogram by comparing the area of
1.1 This test method covers the determination of air (Note
the peak of each component with the area of the peak of the
1) and carbon tetrafluoride as impurities in sulfur hexafluoride.
corresponding component on the reference standard chromato-
NOTE 1—Nitrogen, oxygen, or any of their mixtures is considered to be
gram.
air. Commercial grade air or nitrogen is used for standardization.
4. Significance and Use
1.2 The values stated in SI units are to be regarded as
4.1 Air and carbon tetrafluoride (CF ) are two contaminants
standard. No other units of measurement are included in this
standard. of interest in sulfur hexafluoride (SF ). Both of these contami-
nants adversely affect the performance of SF when used as an
1.3 This standard does not purport to address all of the
electrical insulating gas. Specification for maximum levels of
safety concerns, if any, associated with its use. It is the
these contaminants are given in Specification D2472.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter- 4.2 Gas chromatography is used to separate these contami-
mine the applicability of regulatory limitations prior to use. nants from a sample of SF and to determine their concentra-
1.4 This international standard was developed in accor- tion.
dance with internationally recognized principles on standard-
5. Apparatus
ization established in the Decision on Principles for the
5.1 Gas Chromatograph, consisting of a sample inlet
Development of International Standards, Guides and Recom-
system, adsorption column, flow meter, detector, and data
mendations issued by the World Trade Organization Technical
handling system. Ensure that the column material of construc-
Barriers to Trade (TBT) Committee.
tion and sample components are compatible. The apparatus
2. Referenced Documents
must completely separate air, carbon tetrafluoride, and sulfur
hexafluoride as indicated by return of the recorded peak to the
2.1 ASTM Standards:
base line between each successive peak. Chromatograms must
D2472 Specification for Sulfur Hexafluoride
be reproducible so that successive runs of a reference standard
E260 Practice for Packed Column Gas Chromatography
agree on each component peak area or height within 5 %. For
E355 Practice for Gas Chromatography Terms and Relation-
additional information on gas chromatography see Practices
ships
E260 and E355.
3. Summary of Test Method
6. Reagents and Materials
3.1 Air and carbon tetrafluoride are separated physically by
6.1 Cylinder of Helium Gas.
gas chromatography and compared to corresponding compo-
6.2 Reference Standard Mixture—A gas mixture that con-
nents separated under similar conditions from a reference
tains known percentages of air and carbon tetrafluoride in
standard mixture of known composition. The individual com-
helium or air and carbon tetrafluoride in sulfur hexafluoride is
required. The concentration of a component in the reference
This test method is under the jurisdiction of ASTM Committee D27 Electrical
sample should not be less than 50 % nor more than 300 % of
Insulating Liquids and Gases and is the direct responsibility of Subcommittee
the concentration of the corresponding component in the
D27.03 on Analytical Tests.
unknown.
Current edition approved Oct. 1, 2019. Published October 2019. Originally
approved in 1968. Last previous edition approved in 2011 as D2685 – 11. DOI:
7. Calibration and Standardization
10.1520/D2685-11R19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
7.1 ApparatusPreparation—Preparethegaschromatograph
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
for use as directed by the manufacturer. The following operat-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. ing conditions have been found satisfactory. However, any
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2685−11 (2019)
with an integrator, if available.
combination of conditions that result in complete separations
as indicated in the apparatus section will be satisfactory.
A 5 b 3h 3a /n (1)
~ !
(
Carrier gas helium, 40 to 50 mL/min
Column Porapak Q-80/100 mesh or Porapak R 50/80 mesh where:
Column size 6 to 10 Ft (2–3.5 m) by ¼ in. (6.4 mm) nominal
A = average area of each component peak,
Column temperature 40 to 50 °C
b = peak width at half height,
Detector temperature 70 to 80 °C
Sample volume 2 to 5 mL approximately
h = peak height above base line.
Attenuation lowest which will keep peaks on a scale may be varied
a = attenuation,
during run
n = number of peaks included in average, and
Detector thermal conductivity
∑ = summation of the individual pe
...