Case 621G - Selective Catalytic Reduction (SCR) System

7-MAINTENANCE
SelectiveCatalyticReduction(SCR)system
WhatisSelectiveCatalyticReduction(SCR)?
Yourmachineisequippedwithadditionalcomponentstocomplywithnationalandlocalexhaustemissionsrequire-
ments.ThemaincomponentsoftheSCRsystemincludetheSCRcatalyst,theDEF/ADBLUE®injectionunit,the
DEF/ADBLUE®tank,theSupplyModule(SM),theDieselOxidationCatalyst(DOC),theCleanUpCatalyst(CUC)
andtheexhaustap.
HowdoesSelectiveCatalyticReduction(SCR)work?
Duringcombustion,harmfulNitrogenOxide(NO
x
)moleculesareformedintheexhaust.Byinjectingasolutioninto
theexhaustpriortoacatalyst,theNO
x
canbeconvertedtoharmlesselementalNitrogenandwater.Thishappens
whentheNO
x
moleculesreactinsidethecatalystwiththeheatgeneratedbytheengineandtheammoniainthe
DEF/ADBLUE®solution.TheDOCisusedtomaximizetheSCRcatalystefciencybymaintaininga50/50ratioof
NitricOxide(NO)andNitrogenDioxide(NO
2
)priortoexhaustgasesenteringtheSCRchamber.
NOTICE:prolongedidlingofthemachinewithnoloadformorethan6hwillcausedamagetotheSCRcatalyst.
Duringcoldengineoperationatlowenginecoolantandambientairtemperatures,watervaporwillbevisiblefromthe
exhaustwhentheengineoperates.Thiswatervaporwillresemblesteamorlightwhitesmokeandwilldissipateas
theengineandmachinecomponentswarmandisconsiderednormal.
NOTE:afterengineshutdown,theSCRsystemwillperformapurgecycle,whichpermitsthesupplymoduletocon-
tinuetorunforupto90seconds.Thisistobeconsiderednormalandrequiresnoactionfromtheoperator.
WhatisDEF/ADBLUE®?
DEF/ADBLUE®isanon-toxicaqueousureasolution(
32.5%)withaslightammoniaodorusedtochemically
reduceNOxemissionsfromheavy-dutydieselpow-
eredvehicles.DEF/ADBLUE®isneitherexplosivenor
harmfultotheenvironmentandisclassiedunderthe
minimum-riskcategoryoftransportableuids.
DEF/ADBLUE®qualityisdenedbyISO22241-1.The
AmericanPetroleumInstitute(API®)hasavoluntarycer-
ticationprogramforDEF/ADBLUE®.ToensureDEF/
ADBLUE®satisestherequirementsofISO22241,look
fortheAPI®DEF/ADBLUE®CerticationMark™when-
everyoupurchaseDEF/ADBLUE®.
APIDieselExhaustFluid(DEF)/AdBlue®Certication
MarkisaregisteredtrademarkofAPIintheUnitedStates
andorothercountries.
20101556A1
FindingDieselExhaustFluid(DEF)/AdBlue®
YourauthorizedequipmentdealerisfullyequippedtoaccommodateallyourDEF/ADBLUE®needs.
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