ASTM_D_7821_-_12.pdf

Designation:D782112Standard 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 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 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 method 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 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-priate safety and health 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 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 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 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.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 percent 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 ambient environmentis allowed to equilibrate.A reading is taken by pressing abutton,and the unit of measure and concentration are directlyread from a digital display.5.Apparatus5.1 RefractometerArefractometer is an optical instrumentused to measure the physical properties of a solution.Refrac-tometers suitable for use in this test method shall possess 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/D7821-12.2Available 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,3362 Walden Avenue,Depew,NY 14043-2437.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 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 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 WavelengthMeasurements shall be takenat,or referenced to,a wavelength of 589 nm(6 5 nm).5.1.6 Reference TemperatureAll measurements