ASTM D7607/D7607M-19

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Designation: D7607/D7607M − 11 D7607/D7607M − 19
Standard Test Method for
Analysis of Oxygen in Gaseous Fuels (Electrochemical
Sensor Method)
This standard is issued under the fixed designation D7607/D7607M; 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.
ε NOTE—This standard was revised editorially in October 2013 to reflect dual designation.
1. Scope
1.1 This test method is for the determination of oxygen (O ) in gaseous fuels and fuel type gases. It is applicable to the
measurement of oxygen in natural gas and other gaseous fuels. This method can be used to measure oxygen in helium, hydrogen,
nitrogen, argon, carbon dioxide, mixed gases, process gases, and ambient air. The applicable range is 0.1 ppm(v) to 25%25 % by
volume.
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated
in each system mayare not benecessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall
be used independently of the other. Combiningother, and values from the two systems may result in non-conformance with the
standard.shall not be combined.
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.
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.
2. Referenced Documents
2.1 ASTM Standards:
D4150 Terminology Relating to Gaseous Fuels
D5503E177 Practice for Natural Gas Sample-Handling and Conditioning Systems for Pipeline InstrumentationUse of the Terms
Precision and Bias in ASTM Test Methods (Withdrawn 2017)
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 For general terminology, see Terminology D4150.
3.2 Definitions:
3.2.1 electrochemical sensor—sensor, n—Aa chemical sensor that quantitatively measures an analyte by the electrical output
produced by the sensor.
3.2.2 span calibration—calibration, n—Thethe adjustment of the transmitter electronics to the sensor’s signal output for a given
oxygen standard.
This test method is under the jurisdiction of ASTM Committee D03 on Gaseous Fuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-Line
Analysis of Gaseous Fuels.
Current edition approved June 1, 2011Nov. 15, 2019. Published July 2011January 2020. Originally approved in 2011. Last previous edition approved in 2011 as
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D7607D7607/D7607M–11.–11 . DOI: 10.1520/D7607_D7607M-11E01.10.1520/D7607_D7607M-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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D7607/D7607M − 19
3.2.3 zero calibration—calibration, n—Thethe adjustment of the transmitter electronics to the sensor’s signal output for a
sample gas containing less than 0.1ppm(v)0.1 ppm(v) oxygen.
4. Summary of Test Method
4.1 Measurement of oxygen is accomplished by comparing the electrical signal produced by an unknown sample with that of
a known standard using an oxygen specific electrochemical sensor. A gaseous sample at constant flow and temperature is passed
over the electrochemical cell. Oxygen diffuses into the sensor and reacts chemically at the sensing electrode to produce an electrical
current output proportional to the oxygen concentration in the gas phase. Experience has shown that the types of sensors supplied
with equipment used in this standard typically have a linear response over the ranges of application which remains stable during
the sensor’s useful life. The analyzer consists of a sensor, a sample flow system, and the electronics to accurately determine the
sensor signal.
5. Significance and Use
5.1 This test method is primarily used to monitor the concentration of oxygen in gases to verify gas quality for operational needs
and contractual obligations. Oxygen content is a major factor influencing internal corrosion, fuel quality, gas quality, and user and
operator safety.
6. Interferences
6.1 Interfering gases such as oxides of sulfur, oxides of nitrogen, and hydrogen sulfide can produce false readings and reduce
the expected life of the sensor. Scrubbers are used to remove these compounds. Special sensors suitable for gas containing high
fractions of carbon dioxide are available from manufacturers.
7. Apparatus
7.1 Sensor—The sealed sensor is contained in a housing constructed of stainless steel or other non-permeable material. The
sensor contains a cathode and an anode in an electrolyte solution. A fluorocarbon membrane allows the oxygen from the sample
to diffuse into the sensor. Oxygen in the sample is reduced at the cathode and is simultaneously oxidized at the anode. The electrons
released at the surface of the anode flow to the cathode surface when an external electrical path is provided. The current is
proportional to the amount of oxygen reaching the cathode and is used to measure the oxygen concentration in the gas phase. The
electrochemical reactions for a lead anode cell are as follows:
(cathode half reaction)
O 12H O14e →4OH
2 2
(cathode half reaction)
2 2
O 12H O14e →4OH
2 2
(anode half reaction)
2 2
2Pb14OH →2PbO12H O14e
(overall cell reaction)
2Pb1O →2PbO
Any electrochemical cell with different materials can be employed if the cell can give the same performance for selective oxy-
gen detection with similar sensitivity.
7.2 Electronics—Various electronic circuits are used to amplify and filter the sensor signal. The signal output may be corrected
for the gas sample temperature.
7.3 Output—Automatic digital or range selectable analog display of parts per million or percent oxygen reading by volume.
7.4 Sampling System—Sample gas must be introduced to the sensor of the analyzer. A flow control metering valve is positioned
upstream of the analyzer to provide a gas sample flow rate of 0.5 to 2 L/min [1 to 5 SCFM]. If necessary, a pressure regulator with
a metallic diaphragm can be used upstream of the flow control valve to provide 35 to 200 kPa [5 to 30 psig] inlet pressure. A
leak-free sample pump may be used for low pressure sampling. Stainless steel tubing and connections should be used to minimize
any air intrusion into the sampling system. Gas scrubbers may be necessary to remove interfering gases such as oxides of sulfur,
oxides of nitrogen, and hydrogen sulfide. A suitable coalescing or particulate filter can be used to remove condensation, moisture,
and/or particulates or particulates, or a combination thereof, to prevent erroneous analysis readings and damage to the sensor. A
meter, such as a rotameter, is used to monitor the sample gas flow through the analyzer.
8. Hazards
8.1 Use safe and proper venting if using this method for the analysis of hazardous or flammable gases. Failure to follow
manufacturer’s instructions for the instrumentation used in this test method may result in a hazardous condition.
8.2 Do not open the sensor. The sensor contains a corrosive liquid electrolyte that could be harmful if touched or ingested. Refer
to the Material Safety Data Sheet provided by the sensor manufacturer.
D7607/D7607M − 19
9. Preparation of Apparatus and Calibration
9.1 Zero alibration—Calibration—In theory, the oxygen sensor produces no signal when exposed to oxygen free sample gas.
In reality, expect the sensor to generate an oxygen reading when sampling oxygen-free sample gas due to minor leakage in the
sample line connections, residual oxygen in the sensor’s electrolyte, and tolerances of the electronic components of the analyzer.
Zero calibration is required after a new sensor is installed.
9.1.1 The sensor is exposed to the sample gas with less than 0.1 ppm oxygen. Follow the instrument manufacturer’s
recommended inlet sample flow rate and pressure, usually a flow rate of 1 liter per min or 2 SCFH is recommended for optimum
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