Designation:D7739−11(Reapproved2020)AnAmericanNationalStandardStandardPracticeforThermalOxidativeStabilityMeasurementviaQuartzCrystalMicrobalance1ThisstandardisissuedunderthefixeddesignationD7739;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thislaboratorypracticecoversthequantitativedetermi-nationofsurfacedepositsproducedduringthethermaloxida-tionofgasturbinefuelsbymonitoringtheoscillationfre-quencyofaquartzcrystalduringthermalexposure.Inthispractice,“thermaloxidativestability”referstothetendencyofafueltoresistsurfacedepositformationduringheating.1.2ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesgiveninparenthesesareforinformationonly.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.1.4Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorldTradeOrganizationTechnicalBarrierstoTrade(TBT)Committee.2.SummaryofPractice2.1Aquartzcrystal,fittedwithgoldelectrodes,isfullyimmersedintestfuelcontainedwithinareactor.Anoscillatorcircuit,connectedtothecrystal,suppliesenergytoexcitethequartzcrystalandmonitorsitsresonantfrequency(nominally5MHz)overtimeviaacomputerinterface.Thereactorisequippedwithamagneticstirbar,pressuregauge/transducer,oxygensensor(notrecommendedforcertaintestconditions,see4.11),andthermocoupletomonitorandcontroltestconditions.Priortotesting,thefuelisbubbledwiththetestgasfor30mintoequilibrate.Afterequilibration,thereactorvesselisisolatedandraisedtotestte...
