Designation:D91−02(Reapproved2019)StandardTestMethodforPrecipitationNumberofLubricatingOils1,2ThisstandardisissuedunderthefixeddesignationD91;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thistestmethodcoversthedeterminationofthepre-cipitationnumberofsteamcylinderstocksandblackoils,andcanbeusedforotherlubricatingoils.1.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.1.4Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendationsissuedbytheWorldTradeOrganizationTechnicalBarrierstoTrade(TBT)Committee.2.ReferencedDocuments2.1ASTMStandards:3D4057PracticeforManualSamplingofPetroleumandPetroleumProductsD4177PracticeforAutomaticSamplingofPetroleumandPetroleumProducts3.Terminology3.1DefinitionsofTermsSpecifictoThisStandard:3.1.1ASTMprecipitationnumber,oflubricatingoils,n—thenumberofmillilitresofprecipitateformedwhen10mLoflubricatingoilaremixedwith90mLofASTMprecipitationnaphtha,andcentrifugedundertheconditionsofthetest.4.SignificanceandUse4.1Fullyrefinedpetroleumoilsnormallycontainnonaphtha-insolublematerial.Semirefinedorblackoilsfre-quentlycontainsomenaphtha-insolublematerial(sometimesreferredtoasasphaltenes).Thistestmeasurestheamountofnaphtha-insolublematerialintheoil.Thisquantityisreportedastheprecipitationnumber.5.Apparatus5.1...
