ASTM_D_7940_-_21.pdf

Designation:D794021Standard Practice forAnalysis of Liquefied Natural Gas(LNG)by Fiber-CoupledRaman Spectroscopy1This standard is issued under the fixed designation D7940;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice is for both on-line and laboratoryinstrument-based determination of composition for liquefiednatural gas(LNG)using Raman spectroscopy.Although theprocedures in this practice refer specifically to liquids,thebasic methodology can also be applied to other light hydrocar-bon mixtures in either liquid or gaseous states,provided thedata quality objectives and measurement needs are met.Fromthe composition,gas properties such as heating value and theWobbe index may be calculated.The components commonlydetermined according to this test method are CH4,C2H6,C3H8,i-C4H10,n-C4H10,iC5H12,n-C5H12.Components heavier thanC5 are not measured as part of this practice.NOTE1Raman spectroscopy does not directly quantify the componentpercentages of noble gases;however,inert substances can be calculatedindirectly by subtracting the sum of the other species from 100%.1.2 UnitsThe values stated in SI units are to be regardedas standard.No other units of measurement are included in thisstandard.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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1945 Test Method for Analysis of Natural Gas by GasChromatographyD1946 Practice for Analysis of Reformed Gas by GasChromatographyD3588 Practice for Calculating Heat Value,CompressibilityFactor,and Relative Density of Gaseous FuelsD4150 Terminology Relating to Gaseous FuelsD7833 Test Method for Determination of Hydrocarbons andNon-Hydrocarbon Gases in Gaseous Mixtures by GasChromatographyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 BS EN Standards:3BS EN 60079-28 Explosive Atmospheres.Protection ofEquipment and Transmission Systems using Optical Ra-diationBS EN 60825-1 Safety of Laser Products Part 1:EquipmentClassification,Requirements and Users Guide2.3 ISO Standards:4ISO 6974-5 Natural GasDetermination of Compositionwith Defined Uncertainty by Gas Chromatography,Part 5:Determination of Nitrogen,Carbon Dioxide and C1 to C5and C6+Hydrocarbons for a Laboratory and On-lineProcess Application Using Three ColumnsISO 6976:2016(E)Natural GasCalculation of CalorificValues,Density,Relative Density and Wobbe Indices fromComposition1This practice is under the jurisdiction of ASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-LineAnalysis of Gaseous Fuels.Current edition approved Nov.1,2021.Published November 2021.Originallyapproved in 2014.Last previous edition approved in 2014 as D7940 14.DOI:10.1520/D7940-21.2For 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.3Available from British Standards Institution(BSI),389 Chiswick High Rd.,London W4 4AL,U.K.,http:/.4Available from International Organization for Standardization(ISO),1,ch.dela Voie-Creuse,CP 56,CH-1211 Geneva 20,Switzerland,http:/www.iso.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1?3.Terminology3.1 Definitions:For definitions of general terms used in D03Gaseous Fuels standards,refer to Terminology D4150.3.2 Definitions of Terms Specific to This Standard:3.2.1 accumulations,nthe number of exposures co-addedare referred to as accumulations.3.2.1.1 DiscussionWhile the exposure time is optimizedto control the amount of light entering the instrument for asingle exposure,multiple exposures can be co-added to im-prove signal-to-noise.3.2.2 charge-coupled device(CCD),nsilicon based twodimensional light sensor charac