ASTM_D_7607_-_D_7607M_-_11e1.pdf

Designation:D7607/D7607M111Standard Test Method forAnalysis of Oxygen in Gaseous Fuels(ElectrochemicalSensor Method)1This standard is issued under the fixed designation D7607/D7607M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEThis standard was revised editorially in October 2013 to reflect dual designation.1.Scope1.1 This test method is for the determination of oxygen(O2)in gaseous fuels and fuel type gases.It is applicable to themeasurement 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,pro-cess gases,and ambient air.The applicable range is 0.1 ppm(v)to 25%by volume.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D4150 Terminology Relating to Gaseous FuelsD5503 Practice for Natural Gas Sample-Handling and Con-ditioning Systems for Pipeline Instrumentation3.Terminology3.1 For general terminology see Terminology D4150.3.2 Definitions:3.2.1 electrochemical sensorA chemical sensor that quan-titatively measures an analyte by the electrical output producedby the sensor.3.2.2 span calibrationThe adjustment of the transmitterelectronics to the sensors signal output for a given oxygenstandard.3.2.3 zero calibrationThe adjustment of the transmitterelectronics to the sensors signal output for a sample gascontaining less than 0.1ppm(v)oxygen.4.Summary of Test Method4.1 Measurement of oxygen is accomplished by comparingthe electrical signal produced by an unknown sample with thatof a known standard using an oxygen specific electrochemicalsensor.A gaseous sample at constant flow and temperature ispassed over the electrochemical cell.Oxygen diffuses into thesensor and reacts chemically at the sensing electrode toproduce an electrical current output proportional to the oxygenconcentration in the gas phase.Experience has shown that thetypes of sensors supplied with equipment used in this standardtypically have a linear response over the ranges of applicationwhich remains stable during the sensors useful life.Theanalyzer consists of a sensor,a sample flow system,and theelectronics to accurately determine the sensor signal.5.Significance and Use5.1 This test method is primarily used to monitor theconcentration of oxygen in gases to verify gas quality foroperational needs and contractual obligations.Oxygen contentis a major factor influencing internal corrosion,fuel quality,gasquality,and user and operator safety.6.Interferences6.1 Interfering gases such as oxides of sulfur,oxides ofnitrogen,and hydrogen sulfide can produce false readings andreduce the expected life of the sensor.Scrubbers are used toremove these compounds.Special sensors suitable for gascontaining high fractions of carbon dioxide are available frommanufacturers.1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-LineAnalysis of Gaseous Fuels.Current edition approved June 1,2011.Published July 2011.Originally approvedin 2011.Last previous edition approved in 2011 as D760711.DOI:10.1520/D7607_D7607M-11E01.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.Apparatus7.1 SensorThe sealed sensor is contained in a housingconstructed of stainless steel or other non-permeable material.The sensor contains a cathode and an anode in an electrolytesolution.Afluorocarbon membrane allows the oxygen from thesample to diffuse into the sensor.Oxygen in the sample isreduced at the cathode and is simultaneously oxidized at theanode.The electrons released at the surface of the anode flowto the cathode surface when an external electrical path isprovided.The current is proportional to the amount of oxygenreaching the cathode and is used to measure the oxygenconcentration in the gas phase.The electrochemical reactionsfor a lead anode cell are as follows:O212H2O14e24OH(c