ASTM_D_6186_-_08_2013.pdf

Designation:D618608(Reapproved 2013)Standard Test Method forOxidation Induction Time of Lubricating Oils by PressureDifferential Scanning Calorimetry(PDSC)1This standard is issued under the fixed designation D6186;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of oxidationinduction time of lubricating oils subjected to oxygen at 3.5MPa(500 psig)and temperatures between 130 and 210C.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.2.1 ExceptionPressure measurement appears in MPawith psig provided in parentheses for information only.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 extrapolated onset time,na time determined on athermal curve,as the intersection of the extrapolated baselineand a line tangent to the oxidation exotherm constructed at itsmaximum rate.2.1.2 oxidation induction time,(OIT),n a period of timeduring which the oxidation rate accelerates from zero to amaximum and which corresponds to the extrapolated onsettime.2.1.3 thermal curve,na graph of sample heat flow versustime.3.Summary of Test Method3.1 Asmall quantity of oil is weighed into a sample pan andplaced in a test cell.The cell is heated to a specifiedtemperature and then pressurized with oxygen.The cell is heldat a regulated temperature and pressure until an exothermicreaction occurs.The extrapolated onset time is measured andreported as the oxidation induction time for the lubricating oilat the specified test temperature.4.Significance and Use4.1 Oxidation induction time,as determined under theconditions of this test method,may be used as an indication ofoxidation stability.2This test method is faster than other oiloxidation tests and requires a very small amount of sample.Itmay be used for research and development,quality control,andspecification purposes.However,no correlation has beenestablished between the results of this test method and serviceperformance.5.Apparatus5.1 Pressure Differential Scanning Calorimeter(PDSC),equipped with the following items:5.1.1 Sample Enclosure,with capability to 3.5 6 0.2 MPa(500 6 25 psig)at 210C and pressure gauge graduated atintervals of 200 KPa(28.6 psig)or less.5.1.2 Thermal Analyzer.5.1.3 Aluminum Solid Fat Index(SFI)Sample PanSeeNote 1.5.1.4 Oxidation Stability Software.5.1.5 Calibration Software.5.1.6 Calibrated Flowmeter,with a capacity of at least 200mL/min and graduated in intervals of 5 mL or less.5.1.7 Sample Encapsulation Press.NOTE1It has been found that when oil samples are prepared with SFIpans which have more consistent surface areas than standard flat bottompans,reproducibility is improved.NOTE2Stainless steel or copper tubing is compatible with oxygen.NOTE3See Fig.1 for a diagram of a typical test unit.6.Reagents and Materials6.1 Oxygen,a minimum purity of 99.5%oxygen by vol-ume.(WarningOxidizer.Gas under pressure.)6.2 Indium,of not less than 99.9%indium by mass.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.09.0D on Oxidation of Lubricants.Current edition approved Dec.1,2013.Published December 2013.Originallyapproved in 1997.Last previous edition approved in 2008 as D6186 08.DOI:10.1520/D6186-08R13.2Rhee,In-Sik,“Development of New Oxidation Stability Test Method forLubricating Oils Using a Pressure Differential Scanning Calorimeter(PDSC),”NLGI Spokesman,Vol 65,No.3,June 2001,pp.1623.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.Calibration7.1 Sample Temperature Calibration:7.1.1 Weigh approximately 10 mg of indium into an alumi-num sample pan,insert a lid and crimp the lid to the pan usingthe encapsulation press.Place the crimped pan onto the sampleplatform in the pressure cell.Seal an empty pan in the samemanner and place it on the reference platform.Set the cellcover in place and close the cell.7.1.2 Open the oxygen cylinder valve slightly and set apressure of 3.5 6 0.2 MPa(500 6 25 psig)on the cell inlet linewith the pressure regulator.Partially open the inlet valve on thecell and allow the pressure to slowly build up in the cell.Thisrequires approximately 2 min.Using the outlet valve,adjustand maintain the oxygen purge rate through the flowmeter at100 6 10 mL/min.7.1.3 Set the thermal analyzer to heat from ambient tem-peratur