Designation:D7624−18StandardTestMethodforConditionMonitoringofNitrationinIn-ServicePetroleumandHydrocarbon-BasedLubricantsbyTrendAnalysisUsingFourierTransformInfrared(FT-IR)Spectrometry1ThisstandardisissuedunderthefixeddesignationD7624;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope*1.1Thistestmethodcoversmonitoringnitrationingasolineandnaturalgasengineoilsaswellasinothertypesoflubricantswherenitrationby-productsmayformduetothecombustionprocessorotherroutesofformationofnitrationcompounds.1.2ThistestmethodusesFT-IRspectroscopyformonitor-ingbuild-upofnitrationby-productsinin-servicepetroleumandhydrocarbon-basedlubricantsasaresultofnormalma-chineryoperation.Nitrationlevelsingasolineandnaturalgasengineoilsriseascombustionby-productsreactwiththeoilasaresultofexhaustgasrecirculationorablow-by.Thistestmethodisdesignedasafast,simplespectroscopiccheckformonitoringofnitrationinin-servicepetroleumandhydrocarbon-basedlubricantswiththeobjectiveofhelpingdiagnosetheoperationalconditionofthemachinebasedonmeasuringthelevelofnitrationintheoil.1.3AcquisitionofFT-IRspectraldataformeasuringnitra-tioninin-serviceoilandlubricantsamplesisdescribedinPracticeD7418.Inthistestmethod,measurementanddatainterpretationparametersfornitrationusingbothdirecttrendanalysisanddifferential(spectralsubtraction)trendanalysisarepresented.1.4Thistestmethodisbasedontrendingofspectralchangesassociatedwithnitrationinin-servicepetroleumandhydrocarbon-basedlubricants.Fordirecttrendanalysis,valuesarerecordeddirectlyfromabsorptionspectraandreportedinunitsof100*absorbanceper0.1mmpathlength(orequiva-lentlyabsorbanceunitspercentimetre).Fordifferentialtrendanalysis,valuesarerecordedfromthedifferentialspectra(spectrumobtainedbysubtractionofthespectrumofthereferenceoilfromthatofthein-serviceoil)andreport...
