1、Designation:D498406(Reapproved 2015)Standard Test Method forCarbon Dioxide in Natural Gas Using Length-of-StainDetector Tubes1This standard is issued under the fixed designation D4984;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,t
2、he 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 carbon dioxide in natural gas pipelines.Avail
3、abledetector tubes provide a total measuring range of 100 ppm(parts per million)up to 60%by volume,although the majorityof applications will be on the lower end of this range(that is,under 5%).At least one manufacturer provides a special kit formeasurements from 10 to 100%CO2,but the normal 100-ccha
4、nd pump is not used.See Note 1.NOTE1High-range carbon dioxide detector tubes will have measuringranges in percent(%)CO2,and low-range tubes will be in parts permillion(ppm).To convert percent to ppm,multiply by 10 000(1%=10 000 ppm).1.2 The values stated in SI units are regarded as standard.The inch
5、-pound units in parentheses are for information only.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 r
6、egulatory limitations prior to use.2.Referenced Documents2.1 Gas Processors Association Standard:2337 Test for Hydrogen Sulfide and Carbon Dioxide inNatural Gas Using Length-of-Stain Tubes23.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 detector tube pumpa hand-operated pump of
7、 apiston or bellows type.It must be capable of drawing 100 mLper stroke of sample through the detector tube with a volumetolerance of 65 mL.3It must be specifically designed for usewith detector tubes.3.1.1.1 DiscussionA detector tube and pump togetherform a unit and must be used as such.Each manufa
8、cturercalibrates detector tubes to match the flow characteristics oftheir specific pump.Crossing brands of pumps and tubes is notpermitted,as considerable loss of system accuracy is likely tooccur.33.1.2 gas sampling chamberany container that providesfor access of the detector tube into a uniform fl
9、ow of samplegas at atmospheric pressure and isolates the sample from thesurrounding atmosphere.A stainless steel needle valve(orpressure regulator)is placed between the source valve and thesampling chamber for the purpose of throttling the sampleflow.Flow rate should approximate 1 to 2 volume change
10、s perminute or,at minimum,provide exit gas flow throughout thedetector tube-sampling period.3.1.2.1 DiscussionA suitable sampling chamber may bedevised from a polyethylene wash bottle of nominal 500-mL(16-oz)or 1-L(32-oz)size.The wash bottles internal deliverytube provides for delivery of sample gas
11、 to the bottom of thebottle.A 14.7-mm(12-in.)hole cut in the bottles cap providesaccess for the detector tube and vent for the purge gas(see Fig.1).(An alternate flow-through sampler may be fashioned usinga 1-gal(3.8-L)“zipper”-type food storage bag.The flexibleline enters one corner of the bags ope
12、n end and extends to thebottom of the bag.The opposite corner of the bags top issealed shut.The basic procedure for the sampler in Fig.1applies.)3.1.2.2 DiscussionAn alternate sampling container is acollection bag made of a material suitable for the collection ofnatural gas(for example,polyester fil
13、m).The sampling bagshould have a minimum capacity of 2 L.3.1.3 length-of-stain detector tubea sealed glass tube withbreak-off tips sized to fit the tube holder of the pump.Thereagent layer inside the tube,typically a silica gel substancecoated with the active chemicals,must be specific for carbondio
14、xide and produce a distinct color change when exposed to asample of gas containing carbon dioxide.Any substancesknown to interfere must be listed in the instructions accompa-nying the tubes.A calibration scale should be marked directlyon the tube;however,other markings that provide for easyinterpret
15、ation of carbon dioxide content from a separatecalibration scale supplied with the tubes shall be acceptable.1This test method is issued under the jurisdiction of ASTM Committee D03 onGaseous Fuels and is the direct responsibility of Subcommittee D03.07 on Analysisof Chemical Composition of Gaseous
16、Fuels.Current edition approved Nov.1,2015.Published December 2015.Originallyapproved in 1989.Last previous edition approved in 2011 as D498406(2011).DOI:10.1520/D4984-06R15.2Available from Gas Processors Association,6526 East 60th St.,Tulsa,OK74145.3,First ed.,American Industrial Hygiene Association,Akron,OH 44311.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 The calibration scale shall correlate carbon dioxide concentra-tion to the