1、Designation:D417882(Reapproved 2012)Standard Practice forCalibrating Moisture Analyzers1This standard is issued under the fixed designation D4178;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 p
2、arentheses 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 calibration technique based on thepreparation of standards of known water content.This tech-nique is applicable to the producti
3、on of standards between 20and 2000 cm3/m3water.1.2 The values stated in SI units are to be regarded asstandard.The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the
4、 user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Summary of Practice22.1 The practice is based on the principle that ice has avapor pressure of 0.611 kPa at 0C.Therefore,when a carriergas at a const
5、ant gauge pressure of 207 kPa(30 psig)is passedthrough a molecular sieve saturated with water and held at 0C,the total pressure is equal to 207 kPa plus 98 kPa(oneatmosphere)and the water concentration of the gas leaving themolecular sieve is 0.611/(207+98)106ppm or 2000 ppmvolume water,regardless o
6、f flow.2.1.1 A carrier gas at a constant gauge pressure of 207 kPais passed through a molecular sieve drier and then routed overa molecular sieve support saturated with water and equilibratedat 0C.2.1.2 By blending different volumes of the wet carrier gaswith dried carrier gas,gas standards of known
7、 water concen-tration can be prepared.2.2 The moisture analyzer to be calibrated is then connectedto the source of the gas standard of known water concentration.3.Significance and Use3.1 This practice is intended to provide a method to cali-brate moisture analyzers used on-stream or in the laborator
8、y.4.Apparatus4.1 Ice Bath Primary Standard Moisture Apparatus Fig.1illustrates a typical system.4.2 Wet Test Meter,1-L divisions.4.3 Bubble Meter,graduated in cubic centimetres.4.4 Pressure GaugeA Bourdon-type spring gauge of testgauge quality,100 to 250 mm in diameter,with a scale rangefrom 0 to 40
9、0 kPa(0 to 60 psi),maximum intermediategraduations of 1.5 kPa(0.25 psi).4.5 Wet Mole Sieve 5A,60/80 mesh(other mesh sizes maybe used,except powder).5.Preparation of Apparatus5.1 Saturate mole sieve with water.5.1.1 Cover in beaker enough mole sieve to fill the wet molesieve container.Add water to co
10、ver mole sieve.Let standovernight.5.1.2 Drain the excess water by pouring the mole sieveslurry into a filtering funnel and letting all the free water drainout.NOTE1The useful lifetime of the wet mole sieve is not known.It isrecommended that the procedure described in 5.1.1 and 5.1.2 be followedprior
11、 to each calibration.6.Procedure6.1 Fill the ice bath bucket for the primary standard appa-ratus one third full of water;then add ice to bring the level tofull.6.2 Close the wet flow and the diluent flow needle values.6.3 Turn on the carrier gas supply(nitrogen or air)andadjust the regulator to 207
12、kPa(30 psig).6.4 Open the diluent flow needle valve to obtain a carriergas flow of 1 L/min,as measured with a wet test meter.6.5 Allow the apparatus to equilibrate for 1 h.This allowsthe wet mole sieve to equilibrate at 0C.1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumPr
13、oducts,Liquid Fuels,and Lubricants and is the direct responsibility of Subcom-mittee D02.D0 on Hydrocarbons for Chemical and Special Uses.Current edition approved April 15,2012.Published May 2012.Originallyapproved in 1982.Last previous edition approved in 2005 as D417882(2005).DOI:10.1520/D4178-82R
14、12.2For a more complete discussion of this procedure,see Mator,R.T.,“TraceMoisture Analyzers and Their Calibration,”Proceedings of the 20th Annual ISAAnalysis Instrumentation Symposium,May 12-15,1974,Pittsburgh,PA,“Session:Sampling and Calibration Systems,”1974,p.125.Copyright ASTM International,100
15、 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.6 After 1 h,attach the moisture analyzer to be calibratedand check that the blank moisture content of the carrier gas is6 ppm or less.6.7 Turn off the diluent flow,cm3/m3.6.8 Attach a bubble meter to the exit of the appa
16、ratus andcheck that there is no flow through the system.6.9 Adjust the wet flow needle valve to obtain a flow of 40cm3/min,as measured with a bubble meter.6.10 In a similar manner,adjust the diluent flow needlevalve to obtain a total flow of 200 cm3/min,as measured witha bubble meter.6.11 Connect the moisture analyzer to be calibrated to theexit of the“primary standard”moisture apparatus and allow itsprobe to equilibrate(10 to 15 min).6.12 The analyzer should read the calculated value of 400ppm
