Designation:D971−20StandardTestMethodforInterfacialTensionofInsulatingLiquidsAgainstWaterbytheRingMethod1ThisstandardisissuedunderthefixeddesignationD971;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thistestmethodcoversthemeasurementoftheinter-facialtensionbetweeninsulatingliquidthathasarelativedensity(specificgravity)lessthanwaterandwater,undernon-equilibriumconditions.1.2Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.See7.2foraspecificwarningstatement.1.3Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorldTradeOrganizationTechnicalBarrierstoTrade(TBT)Committee.2.ReferencedDocuments2.1ASTMStandards:2D923PracticesforSamplingElectricalInsulatingLiquids3.SummaryofTestMethod3.1InterfacialTensionisdeterminedbymeasuringtheforcenecessarytodetachaplanarringofplatinumwirefromthesurfaceoftheliquidofhighersurfacetension,thatis,upwardfromthewaterinsulatingliquidinterface.Tocalculatetheinterfacialtension,theforcesomeasurediscorrectedbyanempiricallydeterminedfactorwhichdependsupontheforceapplied,thedensitiesofboththeinsulatingliquidandwater,andthedimensionsofthering.Measurementsaremadeunderrigidlystandardizednonequilibriumconditionsinwhichthemeasurementiscompletedwithin60safterformationoftheinterface.4.SignificanceandUse4.1Interfacialtensionmeasurementsonelectricalinsulatingliquidsprovideasensitivemeansofdetectin...
