1、Designation:D405110(Reapproved 2015)Standard Practice forPreparation of Low-Pressure Gas Blends1This standard is issued under the fixed designation D4051;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A num
2、ber 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 covers a laboratory procedure for thepreparation of low-pressure multicomponent gas blends.Thetechnique is applicable to the ble
3、nding of components atpercent levels and can be extended to lower concentrations byperforming dilutions of a previously prepared base blend.Themaximum blend pressure obtainable is dependent upon therange of the manometer used,but ordinarily is about 101 kPa(760 mm Hg).Components must not be condensa
4、ble at themaximum blend pressure.1.2 The possible presence of small leaks in the manifoldblending system will preclude applicability of the method toblends containing part per million concentrations of oxygen ornitrogen.1.3 This practice is restricted to those compounds that donot react with each ot
5、her,the manifold,or the blend cylinder.1.4 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 limi
6、tations prior to use.2.Summary of Practice2.1 Through the use of a blending manifold,the blendcomponents are combined based upon partial pressure.Com-ponents are added in order of ascending vapor pressure;that is,components of lowest vapor pressure are added first,with theexception that components a
7、t concentrations of 5%or lesswould usually be added first.Compressibility factors areapplied to the component partial pressures to convert themfrom ideal to real gas.The real partial pressures,which areproportional to gas volumes,are normalized to give molpercent composition of the blend.3.Significa
8、nce and Use3.1 The laboratory preparation of gas blends of knowncomposition is required to provide primary standards for thecalibration of chromatographic and other types of analyticalinstrumentation.4.Apparatus4.1 Blending ManifoldConstruct manifold as shown inFig.1.Details of construction are not
9、critical;that is,glass,pipe,or tubing with welded or compression fittings may beused.The manifold must be leak free and arranged forconvenience of operation.More than one feedstock connectionpoint may be included if desired.Connections to the pump andmanometer shall follow accepted vacuum practice.V
10、alves shallhave large enough apertures to permit adequate pumping in areasonable length of time.4.1.1 The finished manifold shall have a leak rate no greaterthan 1 mm Hg/h(0.133 kPa h).4.2 Gauge,a well-type manometer such as the MeriamModel 30EB25(see Note 1).NOTE1A high-vacuum gauge of the McLeod M
11、anostat type pressuretransducer or a 0 bar to 2 bar(absolute)gauge may be included in themanifold system to determine how well the system has been evacuated.4.2.1 Alternatively,an electronic pressure gauge may beused in place of a manometer.4.3 Pump,high-vacuum,two-stage,capable of pumpingdown to a
12、pressure of 1.33 104kPa(0.1 m).5.Reagents and Materials5.1 Blend Components,high-purity,as required dependingon the composition of the proposed blend.5.2 Nitrogen,high purity,as required,for purging and forbalance gas,where applicable.6.Procedure6.1 Connect the blend cylinder to the manifold at posi
13、tion A(see Fig.1 for valve and position designations).Open valves 1,2,3,and 6 and evacuate the manifold system thoroughly.Valves 4 and 5 are closed.NOTE2AMcLeod Manostat type gauge may be used at various timesduring the procedure to determine how well the system has beenevacuated and to indicate if
14、there are leaks present.Otherwise,a steady1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts,Liquid Fuels,and Lubricants and is the direct responsibility of Subcom-mittee D02.04.0A on Preparation of Standard Hydrocarbon Blends.Current edition approved Oct.1,2015.Publ
15、ished December 2015.Originallyapproved in 1981.Last previous edition approved in 2010 as D4051 10.DOI:10.1520/D4051-10R15.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 state condition of the manometer or electronic pressure gauge readin
16、g canbe taken as an indication that an acceptable vacuum has been attained.6.1.1 When a good vacuum less than 0.01 kPa(0.1 mm Hg)is reached,connect one or more blend component cylinders tothe manifold at positions B or C,or both.Close valve 2 andopen valves 4 and 5,thereby evacuating the connecting linesup to the blend component cylinder valves.When a goodvacuum is again reached,close valves 4 and 5 and open theblend component cylinder valves.Ensure that the pressure ofany blend component delive
