ASTM D4178-1982(2005) Standard Practice for Calibrating Moisture Analyzers《湿度分析仪的标准》.pdf

1、Designation: D 4178 82 (Reapproved 2005)An American National StandardStandard Practice forCalibrating Moisture Analyzers1This standard is issued under the fixed designation D 4178; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th

2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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. T

3、his tech-nique is applicable to the production of standards between 20and 2000 cm3/m3water.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, ass

4、ociated 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 limitations prior to use.2. Summary of Practice22.1 The practice is based on the principle that ice has avapor pressure of 0

5、.611 kPa at 0C. Therefore, when a carriergas at a constant 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 i

6、s 0.611/(207 + 98) 3 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 0C.2.1.2 By blending different volumes of

7、 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 intended to provide a method

8、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-type spring gauge of test

9、gauge quality, 100 to 250 mm in diameter, with a scale rangefrom 0 to 400 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

10、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 of the wet mole sieve is not known

11、. 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 flow and the diluent flow needle valu

12、es.6.3 Turn on the carrier gas supply (nitrogen or air) andadjust the regulator to 207 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 equil

13、ibrate at 0C.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 apparatus andcheck that there is no flow through the system.6.9 Adj

14、ust the wet flow needle valve to obtain a flow of 40cm3/min, as measured with a bubble meter.1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.D0 onHydrocarbons for Chemical and Special Uses.Current

15、 edition approved Nov. 1, 2005. Published November 2005. Originallyapproved in 1982. Last previous edition approved in 1999 as D 4178 82 (1999).2For a more complete discussion of this procedure, see Mator, R. T., “TraceMoisture Analyzers and Their Calibration,” Proceedings of the 20th Annual ISAAnal

16、ysis Instrumentation Symposium, May 12-15, 1974, Pittsburgh, PA, “Session:Sampling and Calibration Systems,” 1974, p. 125.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.10 In a similar manner, adjust the diluent flow needlevalve t

17、o 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 for a carrier

18、 gas pressure of 207 kPa gauge. If it does not,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 meter to the exit of the apparatus andcheck that there is no flow through the system.6.15 Adjust

19、the wet flow needle valve to obtain a flow of 10cm3/min using a bubble meter, and then adjust the diluent flowneedle valve to obtain a total flow of 1 L/min. Use a wet testmeter to check the total flow.6.16 After the analyzer equilibrates (10 to 15 min), check tosee that it reads the correct calcula

20、ted value of 20 cm3/m3plusthe blank moisture content found in 6.6 for 207 kPa gaugecarrier gas supply.6.17 When the analyzer reads correctly at the 400-ppm levelbut is not within 62 ppm of the 20 ppm plus the blank moisturecontent value, then the sensor may be bad and needs replacing.7. Calculation7

21、.1 Calculate water concentration in saturated gas (wetflow) as follows:PH2O0C 5 0.611 kPa (1)Ptotal5 A kPa 1 98 kPa gageA kPa 5 carrier gas pressure should be 2076 2 kPa!CH2O5 PH2O!106!Ptotal50.611!106!207 1 985 2000 cm3/m3where:PH2O 0C = vapor pressure of water at 0C,Ptotal= total pressure applied

22、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 flow1 ppm H2O blank (2)where:CH2O=cm3/m3moisture in wet flow,CTH2O=cm3/m3moisture in total flow, andtotal flow = wet flow

23、plus diluent flow.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement o

24、f such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for

25、additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known t

26、o the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. 1 Schematic of Ice bath “Primary Standard” Moisture ApparatusD 4178 82 (2005)2