ASTM_D_1988_-_20.pdf

Designation:D198820Standard Test Method forMercaptans in Natural Gas Using Length-of-Stain DetectorTubes1This standard is issued under the fixed designation D1988;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 test method covers a rapid and simple field deter-mination of mercaptans in natural gas pipelines.Availabledetector tubes provide a total measuring range of 0.5 to 160ppm by volume of mercaptans,although the majority ofapplications will be on the lower end of this range(that is,under 20 ppm).Besides total mercaptans,detector tubes arealso available for methyl mercaptan(0.5 to 100 ppm),ethylmercaptan(0.5 to 120 ppm),and butyl mercaptan(0.5 to 30mg/M3or 0.1 to 8 ppm).NOTE1Certain detector tubes are calibrated in terms of milligramsper cubic metre(mg/M3)instead of parts per million by volume.Theconversion is as follows for 25 C(77 F)and 760 mm Hg.mg/M35ppm3molecular weight24.45(1)1.2 Detector tubes are usually subject to interferences fromgases and vapors other than the target substance.Such inter-ferences may vary among brands because of the use of differentdetection principles.Many detector tubes will have a pre-cleanse layer designed to remove interferences up to somemaximum level.Consult manufacturers instructions for spe-cific interference information.Hydrogen sulfide and othermercaptans are usually interferences on mercaptan detectortubes.See Section 6 for interferences of various methods ofdetection.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.For specific hazard statements,see 8.3.1.4 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:2D4150 Terminology Relating to Gaseous Fuels2.2 GPA Standard:3GPA2188 Method for the Determination of Ethyl Mercaptanin LP-Gas Using Length of Stain Tubes3.Terminology3.1 DefinitionsFor definitions of general terms used inD03 Gaseous Fuels standards,refer to Terminology D4150.4.Summary of Test Method4.1 The sample is passed through a detector tube filled witha specially prepared chemical.Any mercaptan present in thesample reacts with the chemical to produce a color change,orstain.The length of the stain produced in the detector tube,when exposed to a measured volume of sample,is directlyproportional to the amount of mercaptan present in the sample.A hand-operated piston or bellows-type pump is used to drawa measured volume of sample through the tube at a controlledrate of flow.The length of stain produced is converted to partsper million(ppm)by volume mercaptan by comparison to acalibration scale supplied by the manufacturer for each box ofdetection tubes.The system is direct reading,easily portable,and completely suited to making rapid spot checks for mer-captans under field conditions(see Note 1).5.Significance and Use5.1 The measurement of mercaptans in natural gas isimportant,because mercaptans are often added as odorants tonatural gas to provide a warning property.The odor providedby the mercaptan serves to warn consumers(for example,residential use)of natural gas leaks at levels that are well below1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.07 on Analysis ofChemical Composition of Gaseous Fuels.Current edition approved Dec.15,2020.Published January 2021.Originallyapproved in 1991.Last previous edition approved in 2015 as D1988 06(2015).DOI:10.1520/D1988-20.2For 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 Gas Processors Association(GPA),6060 American Plaza,Suite700,Tulsa,OK 74135,http:/www.gpaglobal.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.the flammable or suffocating concentration levels of nat