1、Designation: D4178 82 (Reapproved 2017)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 numb
2、er 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 calibration technique based on thepreparation of standards of known water content. This tech-nique is applicable to
3、the production of standards between20 cm3/m3and 2000 cm3/m3water.1.2 The values stated in SI units are to be regarded asstandard.1.2.1 ExceptionThe values given in parentheses are forinformation only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its
4、 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 princi
5、ples 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. Summary of Practice22.1 The practice is based on the principle that ice h
6、as avapor pressure of 0.611 kPa at 0 C. Therefore, when a carriergas at a constant gauge pressure of 207 kPa (30 psig) is passedthrough a molecular sieve saturated with water and held at0 C, the total pressure is equal to 207 kPa plus 98 kPa (oneatmosphere) and the water concentration of the gas lea
7、ving themolecular sieve is 0.611/(207 + 98) 106ppm or 2000 ppmvolume water, regardless of 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 0 C.2.1.2 By blend
8、ing different volumes of the wet carrier gaswith dried carrier gas, gas standards of known 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 inten
9、ded to provide a method to cali-brate moisture analyzers used on-stream or in the laboratory.4. Apparatus4.1 Ice Bath Primary Standard Moisture ApparatusFig. 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-t
10、ype spring gauge of testgauge quality, 100 mm to 250 mm in diameter, with a scalerange from 0 kPa to 400 kPa (0 psi to 60 psi), maximumintermediate graduations 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
11、 mole sieve with water.5.1.1 Cover in beaker enough mole sieve to fill the wet molesieve container. Add water to cover 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.NOTE 1The useful lifetime
12、 of the wet mole sieve is not known. It isrecommended that the procedure described in 5.1.1 and 5.1.2 be followedprior 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 fl
13、ow and the diluent flow needle values.6.3 Turn on the carrier gas supply (nitrogen or air) andadjust the regulator to 207 kPa (30 psig).1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee
14、D02.D0 on Hydrocarbons for Chemical and Special Uses.Current edition approved Oct. 1, 2017. Published November 2017. Originallyapproved in 1982. Last previous edition approved in 2012 as D4178 82 (2012).DOI: 10.1520/D4178-82R17.2For a more complete discussion of this procedure, see Mator, R. T., “Tr
15、aceMoisture 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 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-
16、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 Technica
17、l Barriers to Trade (TBT) Committee.16.4 Open the diluent flow needle valve to obtain a carriergas flow of 1 Lmin, 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 0 C.6.6 After 1 h, attach the moisture analyzer to be c
18、alibratedand 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 apparatus andcheck that there is no flow through the system.6.9 Adjust the wet flow needle valve to obtain a flow of40 cm3/min, as
19、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 equilibra
20、te (10 min to 15 min).6.12 The analyzer should read the calculated value of400 ppm for a carrier gas pressure of 207 kPa gauge. If it doesnot, adjust the necessary analyzer controls to obtain the correctreading.6.13 Turn off both the wet flow and the diluent flow needlesvalves.6.14 Attach a bubble m
21、eter to the exit of the apparatus andcheck that there is no flow through the system.6.15 Adjust the wet flow needle valve to obtain a flow of10 cm3/min using a bubble meter, and then adjust the diluentflow needle valve to obtain a total flow of 1 Lmin. Use a wettest meter to check the total flow.6.1
22、6 After the analyzer equilibrates (10 min to 15 min),check to see that it reads the correct calculated value of20 cm3/m3plus the blank moisture content found in 6.6 for207 kPa gauge carrier gas supply.6.17 When the analyzer reads correctly at the 400 ppm levelbut is not within 62 ppm of the 20 ppm p
23、lus the blankmoisture content value, then the sensor may be bad and needsreplacing.7. Calculation7.1 Calculate water concentration in saturated gas (wetflow) as follows:PH2O0C 5 0.611 kPa (1)Ptotal5 A kPa198 kPa gaugeA kPa 5 carrier gas pressure should be 207 kPa62 kPa!CH2O5PH2O!106!Ptotal50.611!106
24、!2071985 2000 cm3/m3where:PH2O0C = vapor pressure of water at 0 C,Ptotal= total pressure applied to the water on themolecular sieve, andCH2O=cm3/m3volume moisture in wet flow.7.2 Calculate water concentration in blended gas (total flow)as follows:CTH2O5 wet flow! CH2O!total flow1ppm H2O blank (2)whe
25、re:CH2O=cm3/m3moisture in wet flow,CTH2O=cm3/m3moisture in total flow, andtotal flow = wet flow plus diluent flow.8. Keywords8.1 calibration; carrier gas; moisture analyzer; water contentFIG. 1 Schematic of Ice Bath “Primary Standard” Moisture ApparatusD4178 82 (2017)2ASTM International takes no pos
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