1、Designation: D 5483 05An American National StandardStandard Test Method forOxidation Induction Time of Lubricating Greases byPressure Differential Scanning Calorimetry1This standard is issued under the fixed designation D 5483; the number immediately following the designation indicates the year ofor
2、iginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of oxidationinduct
3、ion time of lubricating greases subjected to oxygen at3.5 MPa (500 psig) and temperatures between 155 and 210C.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety c
4、oncerns, 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. Referenced Documents2.1 ASTM Standards:2E 473 Terminology Relating to Therma
5、l Analysis and Rhe-ology3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 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.3.1.2 oxidation in
6、duction time (OIT), n the period of timefrom the first exposure to an oxidizing atmosphere until theextrapolated onset time.3.1.3 pressure differential scanning calorimeter, (PDSC),na differential scanning calorimeter, as defined in Terminol-ogy E 473, that is capable of maintaining the test sample
7、at acontrolled, elevated pressure.3.1.4 thermal curve, na graph of sample heat flow versustime.4. Summary of Test Method4.1 A small quantity of grease is weighed into a sample panand placed in a test cell. The cell is heated to a specifiedtemperature and then pressurized with oxygen. The cell is hel
8、dat a regulated temperature and pressure until an exothermicreaction occurs. The extrapolated onset time is measured andreported as the oxidation induction time for the grease underthe specified test temperature.4.2 A kinetic equation incorporated with this test methodcan estimate oxidation inductio
9、n times at other temperatures.5. Significance and Use5.1 Oxidation induction time, as determined under theconditions of this test method, can be used as an indication ofoxidation stability.3This test method can be used for researchand development, quality control and specification purposes.However,
10、no correlation has been determined between theresults of this test method and service performance.6. Apparatus6.1 Pressure Differential Scanning Calorimeter (PDSC),equipped with the following items (see Fig. 1).4NOTE 1At the time that the round robin data for this test method wasgenerated, only TA I
11、nstruments4manufactured equipment that met therequirements of 5.1. Subsequently, other companies have manufacturedequipment meeting these requirements. Their use is permitted providedtheir performance is consistent with the repeatability and reproducibilitydescribed in Section 10.6.1.1 Sample Enclos
12、ure, with capability to 3.5 MPa (500psig) at 210C and pressure gauge graduated at intervals of 200kPa (28.6 psi) or less.6.2 Thermal Analyzer.6.3 Aluminum Sample Solid Fat Index (SFI), pan (see Note2).1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubrican
13、ts and is the direct responsibility of SubcommitteeD02.09 on Oxidation.Current edition approved Dec. 15, 2005. Published January 2006. Originallyapproved in 1993. Last previous edition approved in 2002 as D 548302e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
14、 Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Rhee, In-Sik, “Development of a New Oxidation Stability Test Method forGreases Using a Pressure Differential Scanning Calorimeter (PDSC),” NLGIS
15、pokesman, Vol 55, No. 4, July 1991, pp. 123132.4The sole source of supply of the apparatus known to the committee at this timeis TA Instruments, Inc., 109 Lukens Drive, New Castle, DE 19720. If you are awareof alternative suppliers, please provide this information to ASTM InternationalHeadquarters.
16、Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.4 Oxidation Stability Software.6.5 Calibration Software.6.6 F
17、lowmeter, with a capacity of at least 200 mL/min.6.7 Sample Encapsulation Press.NOTE 2It has been found that grease samples can be prepared withmore consistent surface areas using SFI pans as compared to flat bottompans, resulting in better reproducibility.NOTE 3See Fig. 1 for a diagram of a typical
18、 test unit.7. Reagents and Materials7.1 Oxygen, extra dry, of not less than 99.5 % purity byvolume. (WarningOxidizer. Gas under pressure. In additionto other precautions, use stainless steel or copper tubing whichis compatible with oxygen, and pressure gauges which aredesignated for use with oxygen.
19、)7.2 Indium, of not less than 99.9 % purity by mass.8. Calibration8.1 Sample Temperature Calibration:8.1.1 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 pr
20、essure cell. Seal an empty pan in the samemanner and place it on the reference platform. Set the cellcover in place and close the cell.8.1.2 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 th
21、e inlet valve on thecell and allow the pressure to slowly build up in the cell. Thisshould require approximately 2 min. Using the outlet valve,adjust the oxygen purge rate through the flowmeter to 100 610 mL/min. The open position of these valves should remainfixed during the test.8.1.3 Set the ther
22、mal analyzer to heat from ambient tem-perature (approximately 22C) to 180C) at a programmed rateof 10C/min. After completion of the run, measure the meltingtemperature of the indium. If the melting temperature differsfrom 157.4 6 0.2C (see Note 4), correct the difference byusing either the hardware
23、or software calibration proceduredescribed in the manufacturers instruction manual. If thehardware calibration procedure is used, the temperature cor-rection should be performed under 3.5 MPa (500 psig) oxygenpressure with a 100 mL/min purge rate. A typical meltingcalibration curve is shown in Fig.
24、2.NOTE 4The melting temperature of indium is 156.6C at atmosphericpressure, but has been found to be elevated to 157.4C under theconditions of this test method, 3.5 MPa (500 psig) of oxygen.58.2 Temperature Controller Calibration:8.2.1 Remove both the sample pan and the reference panfrom the cell, t
25、hen close the cell. Slowly pressurize the cellwith 3.5 6 0.2 MPa (500 6 25 psig) oxygen and adjust thepurge rate to 100 6 10 mL/min using the cell outlet valve.Select the desired test temperature (either 210, 180, or 155C).8.2.2 Program the cell to maintain the selected test tempera-ture. If, after
26、10 min, the displayed cell temperature differs bymore than 60.2C from the selected temperature, slowly adjustthe temperature controller until they agree. After making anadjustment, wait at least 5 min to make certain that thetemperature is stable before continuing.8.2.3 Some of the newest instrument
27、s do not need this stepdue to their automatic calibration system. Therefore, thecontrol thermocouple calibaration should be performed accord-ing to the instruments manual.8.3 Cell Base Pressure Gauge CalibrationThe calibrationshould be conducted using a calibrated pressure transducer ora previously
28、calibrated gauge according to the pressure cellmanufacturers instructions.9. Procedure9.1 Before starting a test, the control thermocouple calibra-tion shall be conducted at the test temperature (either 210, 180,or 155C) according to 8.2.1 and 8.2.2. When the test tempera-ture is not known, the cali
29、bration should be conducted at210C. Ignore this step if the instrument already has anautomatic temperature controller calibration system.9.2 Weigh 2.0 6 0.1 mg of grease into a sample pan. Spreadthe sample evenly upon the flat portion. Do not spill any of thesample into the trough portion of the pan
30、 (See Fig. 3).NOTE 5Examples of suitable and poor sample on pan patterns areshown in Fig. 3.9.3 Place the uncovered pan containing the sample onto theplatform of the cell according to the PDSC manufacturersinstructions for placing the sample pan. Place an empty pan ofthe same configuration onto the
31、cell platform according to thePDSC manufacturers instructions for placing the referencepan. Close the cell and the pressure release valve.9.4 Beginning at ambient temperature (approximately22C), program the sample temperature to increase at a rate of100C/min to the test temperature.9.5 Allow the sam
32、ple to equilibrate at the test temperaturefor 2 min.NOTE 6This step did not appear in the test method which was used inthe round robin to generate the precision statement. The round robin testmethod used the software of a PDSC manufacturer to determine whenequilibration at test temperatures occurred
33、. Step 9.5 removes this depen-dence on one PDSC manufacturer and is not expected to significantly5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1007.FIG. 1 PDSC Test UnitD5483052affect the measured OIT since this step prece
34、des the pressurization of thetest cell with oxygen.9.6 Open the oxygen valve and slowly pressurize the cell to3.5 6 0.2 MPa (500 6 25 psig). This should require approxi-mately 2 min to reach maximum pressure. The oxidationinduction time is measured from the time when the oxygenvalve is opened.9.7 As
35、 soon as the pressure has equilibrated, check the cellpurge rate and adjust to 100 6 10 mL/min with the outletvalve.9.8 After a duration of 120 min from the time when theoxygen valve was opened, close the oxygen valve and slowlyrelease the cell pressure by opening the cell pressure releasevalve. In
36、the case of a sample for which the approximateoxidation induction time is known, the test can be stopped afterthe oxidation exotherm has occurred.9.9 Plot the thermal curve and measure the extrapolatedonset time for the oxidation exotherm. Report this time, to thenearest tenth of one minute, as the
37、oxidation induction time forthe sample. If more than one oxidation exotherm is observed,record the oxidation induction time for the largest exotherm(See Fig. 4).NOTE 7A typical thermal curve is shown in Fig. 4.9.10 If the induction time is less than 10 min, rerun the testat the next lower temperatur
38、e, starting at 9.2. Allow the cell tocool to ambient temperature before running the test at the nextlower temperature.9.11 After the oxidation induction time requirement speci-fied in 9.10 is satisfied, perform a duplicate test.9.12 If the difference between the two results is greater thanthe 95% de
39、terminability limit stated in the Precision and Biassection of this test method (Section 12), then reject the resultsand determine two more oxidation induction times for thegrease by returning to 9.2. Otherwise, average the oxidationinduction times of both runs.10. Calculation of Induction Times for
40、 OtherTemperatures10.1 After an oxidation induction time has been determinedfor a particular grease, a value can be estimated for othertemperatures using the following equation:t 5 A exp 17 500/T! (1)where:t = estimated oxidation induction time, min,A = oxidation coefficient of the grease, andT = te
41、mperature, K (for desired temperature).The oxidation coefficient (A) is constant for a given greaseand is calculated by (Eq 1) using the oxidation induction timereported in 9.1.2, thus,A 5 oxidation induction time/exp17 500/test temperature, K!.(2)The estimated oxidation induction time can be used a
42、s aguide for choosing appropriate alternative test temperatures fora grease. The estimated oxidation induction time is not a partof the report for this test method.11. Report11.1 Report the following information:11.1.1 Report, to the nearest tenth of one minute, theaverage value calculated in 9.12 a
43、s the oxidation inductiontime (OIT) for the sample.11.1.2 Report the test temperature.FIG. 2 CalibrationFIG. 3 Sample Preparation on SFI PanD548305312. Precision and Bias612.1 The precision of this test method as determined by thestatistical examination of interlaboratory test results involvingeleve
44、n samples, five laboratories, three test temperatures (155,180, and 210C), and oxidation induction times of from 9.0 to45.3 minutes is as follows.12.1.1 Determinability The difference between the pair ofdeterminations averaged to obtain a test result would, in thelong run, in the normal and correct
45、operation of the testmethod, exceed the following value in only one case in twenty:Determinability 5 0.59=m (3)where:m = the mean of the two determinations12.1.2 Repeatability The difference between successiveresults (each the mean of a pair of determinations) obtained bythe same operator with the s
46、ame apparatus under constantoperating conditions on identical material, would in the longrun, in the normal and correct operation of the test method,exceed the following value in only one case in twenty:Repeatability 5 0.42=m (4)where:m = is the mean of the two results12.1.3 ReproducibilityThe diffe
47、rence between two inde-pendent results (each the mean of a pair of determinations)obtained by different operators working in different laborato-ries would, in the long run, exceed the following value onlyone case in twenty:Reproducibility 5 0.71=m (5)where:m = the mean of the two test results.12.2 B
48、iasThe procedure in this test method has no biasbecause the value of oxidation induction time can be definedonly in terms of a test method.13. Keywords13.1 differential scanning calorimetry; lubricating grease;OIT; onset temperature; oxidation; oxidation coefficient; oxi-dation induction time; PDSC;
49、 thermal analysis6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1314.FIG. 4 Typical PDSC Thermal CurveD5483054APPENDIX(Nonmandatory Information)X1. PDSC ROUND ROBIN DATAX1.1 See Table X1.1 for PDSC Round Robin data.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and t
