1、Designation: D7821 12 (Reapproved 2018)Standard 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 cas
2、e of revision, the 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-base
3、d diesel exhaust fluid (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 me
4、thod is designed solely 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
5、values stated in SI 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-pr
6、iate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelo
7、pment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ISO Standard:2ISO 22241 Diesel enginesNOx reduction agent AUS 323. Terminology3.1 Definitions of Terms Specific to This Standard:
8、3.1.1 American Petroleum Institute (API), na nonprofittrade 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
9、 22241.3.1.2 diesel exhaust fluid, DEF, npreparation 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
10、 the velocity of light inair, to its velocity in the 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
11、.3.1.5 biuret, nchemical compound which appears as acharacteristic 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 percen
12、t by weight of urea is used to measure the concen-tration 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 am
13、bient environmentis allowed to equilibrate. A reading is taken by pressing abutton, and the unit of measure and concentration are directlyread from a digital display.1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and Related Fluids and is the direct responsibilit
14、y of SubcommitteeD15.25 on Diesel Exhaust Fluid.Current edition approved Sept. 1, 2018. Published September 2018. Originallyapproved in 2012. Last previous edition approved in 2012 as D782112. DOI:10.1520/D782112R18.2Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Flo
15、or, New York, NY 10036, http:/www.ansi.org.3Sources for DEF refractometers used to establish the precision and bias of thismethod: MISCO Refractometer, 6275 Cochran Road, Solon, OH 44139, andReichert Technologies, 3362 Walden Avenue, Suite 100, Depew, NY 14043.Copyright ASTM International, 100 Barr
16、Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 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 Recommen
17、dations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. 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 possess thefollowing char
18、acteristics:5.1.1 Unit of MeasureThe unit of measure for all DEFreadings shall be urea percent by weight and this shall beclearly identified on the refractometer.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
19、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 equalto or better than the precision statement in Section 9 of this testmethod as determined through ASTM interlaboratory testing.5.1.5 Reference Wav
20、elengthMeasurements shall be takenat, or referenced to, a wavelength of 589 nm (65 nm).5.1.6 Reference TemperatureAll measurements shall bereferenced to a reference temperature of 20 C.5.1.7 Temperature RangeThe refractometer shall be ca-pable of reading samples from 10 to 45 C.5.1.8 Automatic Tempe
21、rature CompensationThe refracto-meter shall provide automatic temperature compensation spe-cific to aqueous urea solutions over the temperature rangedefined 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
22、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 for minimizing sources of errorin a measurement system. The refractometer should be zero setto distilled water before use.6.2 Inspect the refract
23、ometer measuring surface to insurethat it is free of residue from a previous test. Clean the samplesurface and sample well with distilled water and tissue ifneeded.6.3 The exact procedure for zero setting a refractometervaries based on the type and make of instrument. Consult theuser manual for spec
24、ific instructions on zero setting each makeof refractometer.6.4 For the most accurate readings, the refractometer, thecalibration fluid, and the ambient temperature should be in anequilibrium state of temperature. If there is a temperaturedisparity, allow some time for the temperatures to equalizebe
25、fore taking a reading. The equilibrium state is a singletemperature value between the range of 10 to 45 C.7. Procedure7.1 Obtaining a Test Sample:7.1.1 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
26、anoriginal sample container. The sample container should only beopened long enough to remove a sample and should beimmediately sealed.7.1.3 A clean disposable plastic pipette should be used totransfer a sample to the refractometer and the pipette thenimmediately discarded.7.2 Measuring the Sample:7.
27、2.1 The refractometer and ambient environment should bebetween 10 to 45 C.7.2.2 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 ifneeded.7.2.3 Transfer a few drops of DEF sam
28、ple and completelycover the measuring surface of the refractometer.7.2.4 Allow adequate time for the temperature of therefractometer, fluid, and ambient environment to equilibrate.7.2.5 Initiate the reading. The exact procedure for initiatinga reading varies based on the type and make of instrument.
29、Consult the user manual for specific instructions on initiating areading for each make of refractometer.7.2.6 Record the reading on the refractometer 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 fiv
30、e values fluctuate by more than 0.5 %, allowa little more time for the temperature to equilibrate and retestthe sample.7.2.9 Clean measurement surfaces to remove all sampleresidue. Follow the manufacturers guidelines for cleaning theinstrument.8. Report8.1 Report the following information:8.1.1 The
31、sample identification for DEF analyzed (whichmay include such information as product name, lot number,production date, location, type of container, size, 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
32、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 of interlaboratory results according toround robin testing is as follows:9.1.1 RepeatabilityThe difference between two test resultsobtained by the same
33、operator with the same apparatus underconstant operating conditions on identical test material would,in the long run, in the normal and correct operation of the testmethod.9.1.2 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in differ
34、ent laboratories on identical test material would, inthe long run, in the normal and correct operation of the testmethod.D7821 12 (2018)29.2 BiasThe results of bias determination will be availableas part of the interlaboratory study and will be available withinone year of completion of the study.9.2
35、.1 Biuret ContentA maximum limit of +0.3 % m/mbiuret concentration in DEF is required by ISO 22241. Thisfield-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 pr
36、ecision and bias of the test instruments.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
37、 standard are expressly advised that 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 year
38、s andif not revised, either reapproved 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 committ
39、ee, which you may attend. If you feel 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
40、-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). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 12 (2018)3
