1、Designation: D7821 12Standard Test Method forField Test Determination of Urea Concentration in DieselExhaust Fluid (DEF)1This standard is issued under the fixed designation D7821; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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 technique for field testing theconcentration of aqueous urea-based diesel exhaust f
3、luid (DEF)prescribed for use in diesel engines equipped with selectivecatalytic reduction technology and is not intended to circum-vent or replace the more accurate determination of urea contentby refractive index laboratory method, described in ISO22241-2, Annex C.1.2 This test method is designed s
4、olely as a quantitative testto determine the concentration of urea in DEF and does notpurport to determine the quality of DEF nor to detect trace orother contaminants therein. Biuret content of DEF creates aknown bias in this test method. See section 9.2.1 for details.1.3 UnitsThe values stated in S
5、I units are to be regardedas the standard. No other units of measurement are included inthis standard.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 he
6、alth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ISO Standard:2ISO 22241 22241Diesel enginesNOx reduction agentAUS 323. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 American Petroleum Institute (API), na nonprofi
7、ttrade association that licenses diesel exhaust fluid (DEF)marketers to use the API Diesel Exhaust Fluid CertificationMark. A marketer may be licensed to use the API Mark if itsDEF is in compliance with the most recent and applicableedition of ISO 22241.3.1.2 diesel exhaust fluid, DEF, npreparation
8、of aqueousurea (NH2)2CO, containing 32.5 % by weight of technicallypure urea in high-purity water with quality characteristicsdefined by ISO 22241.3.1.3 refractive index, nfundamental physical property ofa substance that is related to the ratio of the velocity of light inair, to its velocity in the
9、substance under examination, at aspecified temperature and wavelength.3.1.4 refractometer, noptical instrument that measures therefractive index of a substance and can be used to characterizethe concentration or mixture ratio of various substances.3.1.5 biuret, nchemical compound which appears as ac
10、haracteristic impurity in aqueous urea solutions.3.1.6 AUS 32, nISO designation for DEF also known asNOx reduction agent AUS 32 (aqueous urea solution).4. Summary of Test Method4.1 A digital refractometer with a special scale specific tothe percent by weight of urea is used to measure the concen-tra
11、tion of a DEF sample.34.2 To determine DEF concentration, the refractometer shallfirst be zero set to distilled water. Next, a sample of DEF isplaced on the measuring surface of the refractometer and thetemperature of the instrument, fluid, and ambient environmentis allowed to equilibrate. A reading
12、 is taken by pressing abutton, and the unit of measure and concentration are directlyread from a digital display.5. Apparatus5.1 RefractometerA refractometer is an optical instrumentused to measure the physical properties of a solution. Refrac-tometers suitable for use in this test method shall poss
13、ess thefollowing characteristics:1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and Related Fluids and is the direct responsibility of SubcommitteeD15.25 on Diesel Exhaust Fluid.Current edition approved Oct. 1, 2012. Published November 2012. DOI:10.1520/D7821-12.
14、2Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.3Sources for DEF refractometers, used to establish the precision and bias of thismethod, MISCO Refractometer, 3401 Virginia Rd., Cleveland, OH 44122 andReichert Technologies
15、, 3362 Walden Avenue, Depew, NY 14043-2437.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.1.1 Unit of MeasureThe unit of measure for all DEFreadings shall be urea percent by weight and this shall beclearly identified on the refract
16、ometer.5.1.2 RangeThe refractometer shall have a minimummeasuring range of 0.0 to 37.0 percent by weight.5.1.3 ResolutionThe refractometer shall resolve readingsto 0.1 % urea by weight.5.1.4 Precision and BiasThe refractometer must be ca-pable of reading with a repeatability and reproducibility equa
17、lto or better than the precision statement in Section 9 of this testmethod as determined through ASTM interlaboratory testing.5.1.5 Reference WavelengthMeasurements shall be takenat, or referenced to, a wavelength of 589 nm (6 5 nm).5.1.6 Reference TemperatureAll measurements shall bereferenced to a
18、 reference temperature of 20C.5.1.7 Temperature RangeThe refractometer shall be ca-pable of reading samples from 10 to 45C.5.1.8 Automatic Temperature CompensationThe refracto-meter shall provide automatic temperature compensation spe-cific to aqueous urea solutions over the temperature rangedefined
19、 in 5.1.7.5.1.9 Digital DisplayThe refractometer shall be equippedwith a digital display capable of rendering a numeric represen-tation of urea concentration.5.1.10 Zero SetThe refractometer shall be capable ofbeing zero set to distilled water by the user.6. Calibration6.1 Calibration is essential f
20、or minimizing sources of errorin a measurement system. The refractometer should be zero setto distilled water before use.6.2 Inspect the refractometer measuring surface to insurethat it is free of residue from a previous test. Clean the samplesurface and sample well with distilled water and tissue i
21、fneeded.6.3 The exact procedure for zero setting a refractometervaries based on the type and make of instrument. Consult theuser manual for specific instructions on zero setting each makeof refractometer.6.4 For the most accurate readings, the refractometer, thecalibration fluid, and the ambient tem
22、perature should be in anequilibrium state of temperature. If there is a temperaturedisparity, allow some time for the temperatures to equalizebefore taking a reading. The equilibrium state is a singletemperature value between the range of 10 to 45 degrees C.7. Procedure7.1 Obtaining a Test Sample:7.
23、1.1 Make a record of the sample identity.7.1.2 Great care should be taken to prevent contaminationwhen taking samples of DEF directly from a vehicle or anoriginal sample container. The sample container should only beopened long enough to remove a sample and should beimmediately sealed.7.1.3 A clean
24、disposable plastic pipette should be used totransfer a sample to the refractometer and the pipette thenimmediately discarded.7.2 Measuring the Sample:7.2.1 The refractometer and ambient environment should bebetween 10 to 45C.7.2.2 Inspect the refractometer measuring surface to insurethat it is free
25、of residue from a previous test. Clean the samplesurface and sample well with distilled water and tissue ifneeded.7.2.3 Transfer a few drops of DEF sample and completelycover the measuring surface of the refractometer.7.2.4 Allow adequate time for the temperature of therefractometer, fluid, and ambi
26、ent environment to equilibrate.7.2.5 Initiate the reading. The exact procedure for initiatinga reading varies based on the type and make of instrument.Consult the user manual for specific instructions on initiating areading for each make of refractometer.7.2.6 Record the reading on the refractometer
27、 digital displayto one decimal place in percent weight of urea.7.2.7 Take four more readings of the same sample andaverage the results.7.2.8 If the five values fluctuate by more than 0.5 %, allowa little more time for the temperature to equilibrate and retestthe sample.7.2.9 Clean measurement surfac
28、es to remove all sampleresidue. Follow the manufacturers guidelines for cleaning theinstrument.8. Report8.1 Report the following information:8.1.1 The sample identification for DEF analyzed (whichmay include such information as product name, lot number,production date, location, type of container, s
29、ize, or any otherinformation that may aid in its identification or origin).8.1.2 The date and time of the test,8.1.3 The name of the person completing the test, and8.1.4 The weight percent urea found.9. Precision and Bias9.1 The precision of this test method as determined bystatistical examination o
30、f interlaboratory results according toround robin testing4is as follows:9.1.1 RepeatabilityThe difference between two test resultsobtained by the same operator with the same apparatus underconstant operating conditions on identical test material would,in the long run, in the normal and correct opera
31、tion of the testmethod.9.1.2 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in different laboratories on identical test material would, inthe long run, in normal and correct operation of the testmethod.9.2 BiasThe results of bias dete
32、rmination will be availableas part of the interlaboratory study and will be available withinone year of completion of the study.9.2.1 Biuret ContentA maximum limit of +0.3 % m/mbiuret concentration in DEF is required by ISO 22241. This4Supporting data have been filed at ASTM International Headquarte
33、rs and maybe obtained by requesting Research Report RR: DXXXX.D7821 122field-test method does not address biuret content and therefore,even when testing DEF which conforms to the ISO biuretspecification, results may be biased by +0.3%. This bias isadditive to any precision and bias of the test instr
34、uments.10. Keywords10.1 DEF; diesel exhaust fluid; refractometry; SCR; selec-tive catalytic reduction; ureaASTM 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 th
35、at determination of the validity of any such patent rights, and the riskof infringement of 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 reappr
36、oved or withdrawn. Your comments are invited either for revision of this standard or for 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 f
37、eel that your comments have not received a fair hearing you shouldmake your views known to 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 re
38、prints (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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D7821 123
