D 2878 – 95_RDI4NZGTOTU_

DesignationD287895 AnAmerican National Standard Standard Test for Estimating Apparent Vapor Pressures and Molecular Weights of Lubricating Oils 1 This standard is issued under the fixed designation D2878; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A superscript epsilon e indicates an editorial change since the last revision or reapproval. 1. Scope 1.1 This test provides a calculation procedure for converting data obtained by Test D972 to apparent vapor pressures and molecular weights. It has been demon- strated to be applicable to petroleum-based and synthetic ester lubricating oils, 2 at temperatures of 395 to 535K 250 to 500F. However, its applicability to lubricating greases has not been established. NOTE 1Most lubricants boil over a fairly wide temperature range, a fact recognized in discussion of their vapor pressures. For example, the apparent vapor pressure over the range 0 to 0.1 evaporated may be as much as 100 times that over the range 4.9 to 5.0 evaporated. 3 1.2 The values stated in SI units are to be regarded as the standard. In cases in which materials, products, or equipment are available in inch-pound units only, SI units are omitted. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bilityorregulatorylimitationspriortouse.Forspecifichazard statements, see Note 3, Note 4, and Note 6. 2. Referenced Documents 2.1 ASTMStandards A240 Specification for Heat-Resisting Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels 3 D92 Test for Flash and Fire Points by Cleveland Open Cup 4 D972 Test for Evaporation Loss of Lubricating Greases and Oils 4 D2503 Test for Molecular Weight Relative Mo- lecular Mass of Hydrocarbons by Thermoelectric Mea- surement of Vapor Pressure 4 D2595 Test for Evaporation Loss of Lubricating Greases over Wide Temperature Range 4 D2883 TestforReactionThresholdTemperatureof Liquid and Solid Materials 5 E1 Specification forASTM Thermometers 6 E659 Test forAutoignition Temperature of Liquid Chemicals 7 3. Terminology 3.1 DefinitionsofTermsSpecifictoThisStandard 3.1.1 apparent vapor pressure p, nthe time-averaged value of the vapor pressure from the start to the end of the evaporation test. 3.1.1.1 DiscussionWhilethismayincludesomeeffectsof differences in nonideality of the vapor, heat of vaporization, surfacetension,andviscositybetweenthem-terphenylandthe lubricating oil, these factors have been demonstrated to be negligible. 7 Unless stated, this average shall cover the range 0 to 5 6 1. 3.1.2 cell constant k, nthe ratio of the amount of m-terphenylorlubricatingoilcarriedoffperunitvolumeofgas to that predicted by Daltons law. k 5 22.41PW/VpM 1 where k 5 call constant P 5 ambient atmospheric pressure, torr W 5 mass of lubricant evaporated, g V 5 volume of gas passed through all litres at 273K and 101.3 kPa 760 torr p 5 apparent vapor pressure, torr M 5 mole average molecular weight of lubricant vapor, g/mole T 5 test temperature, K Ithasbeenempiricallydeterminedthat-terphenylinair k 5 0.1266 2 12.60/T 2 273 2 and that the cell constant is independent of the composition of the lubricant. 7 Test D972 is normally run with air, which may cause changes in easily oxidized fluids. In such cases, use of 1 This test is under the jurisdiction of Committee D-2 on Petroleum ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.11on Engineering Sciences of High Perance Fluids and Solids. Current edition approved Jan. 15, 1995. Published March 1995. Originally published as D287870. Last previous edition D287893. 2 Coburn, J. F., “Lubricant Vapor Pressure Derived from Evaporation Loss,” Transactions,AmericanSocietyofLubricatingEngineers,ASLTA,Vol12,1969,pp. 129134. 3 AnnualBookofASTMStandards, Vol 01.03. 4 AnnualBookofASTMStandards, Vol 05.01. 5 AnnualBookofASTMStandards, Vol 05.02. 6 AnnualBookofASTMStandards, Vol 14.03. 7 AnnualBookofASTMStandards, Vol 14.02. 1 AMERICAN SOCIETY FOR TESTINGAND MATERIALS 100 Barr Harbor Dr., West Conshohocken, PA19428 Reprinted from theAnnual Book ofASTM Standards. CopyrightASTM NOTICEThisstandardhaseitherbeensupersededandreplacedbyanewversionor discontinued.ContactASTMInternationalwww.astm.orgforthelatestination. common reactive gas nitrogen and recalibration to obtain a slightly different cell constant k8 is mandatory. 4. Summary of Test 4.1 Thetestisrunattheselectedtemperatureforasufficient time to give the selected amount of evaporation, which is 5 6 1 unless otherwise specified. This evaporation rate is compared with a standard value for pure m-terphenyl to yield the apparent vapor pressure and molecular weight of the lubricating oil as defined in Section 3. 5. Significance and Use 5.1 The vapor pressure of a substance as determined by measurement of evaporation reflects a property of the bulk sample.Littleweightisgivenbytheproceduretothepresence of low concentrations of volatile impurities. 5.2 Vaporpressure,perse,isathermodynamicpropertythat isdependentonlyuponcompositionandtemperatureforstable systems. In the present , composition changes occur during the course of the test so that the contribution of minor amounts of volatile impurities is minimized. 6. Apparatus 6.1 EvaporationCell, as described inAnnexA1. 6.2 AirSupplySystem, capable of supplying to the cell the requiredflowofairfreeofentrainedparticlesWarningSee Note 2. A 410-mm 16-in. length of 1-in. diameter pipe packedwithglasswoolhasbeenfoundsatisfactoryforfiltering the air. NOTE 2WarningCompressed gas under high pressure. Use with extreme caution in the presence of combustible material, since the autoignitiontemperaturesofmostorganiccompoundsinairaredrastically reduced at elevated pressures. SeeAnnexA2.1. 6.3 OilBath, as described inAnnexA1. NOTE 3Other constant-temperature baths may be used if the exit air passing over the grease sample is at the test temperature 60.5K 1F. 6.4 ThermometersASTM thermometers graduated in either Celsius or Fahrenheit degrees and having a range from5 to 400C 20 to 760F and coning to the requirements for Thermometers 3C or 3F, respectively, as described in Specification E1. 6.5 Flowmeter 8 A rotameter calibrated to deliver air at a rate of 2.583 6 0.02 g/min between 289 and 302K 60 and 85F 2 L/min at standard temperature and pressure. It shall befurnishedwithaneedlveandmountedasshowninFig. 1. 6.6 OilSampleCup, as described in Fig. 1 andA1.1.2. 7. Calibration of Equipment 7.1 ItisassumedthatequipmentconingtoTest D972 in design and installation needs no calibration. If questions arise, carry out the procedure using m-terphenyl WarningSee Note 4 of good commercial quality. 9 The following two points shall be determined Temperature Evaporation to Con to Eq 2, gK F Time, h 395 250 22 0.267 6 0.027 420 300 6.5 0.503 6 0.050 If the data do not fall within the above ranges, check flow rate and temperature. If these are correct, prepare a substitute equation fork8 similar to Eq 2 and use it in Section 10. When useofnonreactivegasisrequired,thiscalibrationisnecessary asstandardcellconstantsarenotvalidforgasesotherthanair. NOTE 4WarningHarmful or fatal if swallowed. SeeA2.2. 7.2 IftheapparatusspecifiedinTestD2595istobe used, it shall be calibrated as described in 7.1. 8. Procedure 8.1 Weigh the clean test specimen cup and hood to the nearest1mg.Transfer,bymeansofapipet,10.00 6 0.05gof test specimen to the cup. Assemble the cup and hood, being careful not to splash oil on the underside of the hood. Weigh the assembly and record the net test specimen weight to the nearest 1 mg. 8.2 With cover in place, but without the hood and test specimen cup attached, allow the evaporation cell to acquire the temperature of the bath controlled to 60.5K 61F at which the test is to be made by immersing the cell in it, as showninFig.1.Allowthecelltoremaininthebathatleast 1 2 hbeforebeginningthetest.Duringthisperiod,allowcleanair WarningSee Note 2 to flow through the cell at the prescribed rate, 2.583 6 0.02 g/min 2 L/min at standard temperature and pressure, as indicated by the rotameter.Then remove the cover, thread and weighed hood and sample cup into place, and replace the cover. Tighten the three knurled cover-tightening screws securely to prevent air leakage under the cover. Pass clean air through the cell for the required period. NOTE 5WarningDonotperthistestwithairattemperaturesin exces of the autoignition temperature of the test specimen as determined by Test E659 or Test D2883, or both. 8.3 Attheendofthetestperiod,removetheassembledtest specimen cup and hood from the cell, and allow to cool to room temperature. Determine the net weight of the sample to the nearest 1 mg. 9. Determination of Molecular Weight andApparent Vapor Pressure 9.1 If a value of M is already available from Test D2503 or equivalent, 9.2-9.4 and 10.1 may be omitted, even though this value is for the whole lubricant instead of the part vaporized, as the calculation is not very sensitive to M error. 9.2 Conduct a test on the sample in accordance with the procedure in Section 7, at 477K 400F. The proper test time to evaporate 5 0.500 g may be estimated from the flash point of the lubricant as measured byTest D92, from Table 1. NOTE 6The need for a run at 477K 400F is, created by lack of exact values for the first two constants in Eq 3, Eq 4, and Eq 5 for other temperatures. 9.3 For synthetic and redistilled petroleum oils, the 8 The Flowrater meter manufactured by Fisher and Porter Co., Hatboro, PA, has been found satisfactory. 9 Santowax,M.,MonsantoChemicalCo.,St.Louis,MO,hasprovedsatisfactory. D2878 2 variationofW/twithWisnotgreat,andthe5pointshallbe approximated by linear interpolation of two points taken at different W values. For single-distilled petroleum or unknown oils, three points shall be plotted, representing the estimated time and also half and twice that time.These readings may all be obtained on one sample by stop and start operation of the apparatus. 9.4 When a single data point that does not fall within the 5 6 1 evaporated range is used as is often justifiable on synthetic oils or the evaporation is measured at some other level of W, this fact shall be reported in Section 11. 9.5 The test for apparent vapor pressure is conducted in accordancewithSection8fortheestimatedtimeattheselected temperature. If the 5 6 1 criterion is not met, proceed as in 9.3. 10. Calculations 10.1 CalculationofMolecularWeight 10.1.1 Use the evaporation time,t, in seconds obtained in 9.3 to evaporate 5 6 1. 10.1.2 Calculate the molecular weights of lubricants in general as follows FIG. 1 Evaporation Test Cell D2878 3 logM 5 3.028 2 0.164log 10 335PW/t 3 10.1.3 Forlubricantsofknowncomposition,slightlygreater accuracy is obtained with special equations 10.1.3.1 For polyol esters logM 5 3.181 2 0.207log 10 335PW/t 4 10.1.3.2 For dibasic esters logM 5 3.089 2 0.190log 10 335PW/t 5 10.1.3.3 For mineral oils logM 5 2.848 2 0.106log 10 335PW/t 6 10.1.4 The molecular weight equations all contain the standard value ofkat 477K 400F fromTable 2. If a change greater than 63 in this value is caused by the calibration in Section7,adjustmentsshallbemadeintheconstant10 335by multiplying it by the factor k/k8. 10.2 CalculationofApparentVaporPressure 10.2.1 Usethemolecularweight,M,ascalculatedin10.1or predeterminedin9.1tocalculatethevaporpressureasfollows p 5 672PW/tkM 7 where k is obtained from Table 2. Use Eq 2 to extend this table. If a special equation was required in 7.1, use it rather than Table 2 or Eq 2. 10.2.2 For the special case of lubricants run at 477K 400Ffor6.5hasrequiredinseveralmilitaryaircraftengine oil specifications, with P 5 760 torr logp 5 1.164log 10W 2 1.255 8 where 10 W 5 percent evaporated from a 10-g sample. 10.2.3 These results may be converted to SI units by the equations p8 5 133.32pandP8 5 133.32P 9 where p8 5 apparent vapor pressure, Pa P8 5 ambient atmospheric pressure, Pa 11. Report 11.1 If the results are obtained in accordance with 9.1, 9.2, 9.3, and 9.5, and calculated by Eq 3, they shall be reported as “Apparent Vapor Pressure 5 __ torr at __C __F, and Molecular Weight 5 __.” 11.2 If the results are obtained in accordance with 9.1, 9.2, 9.3, and 9.5, and calculated by Eq 4, Eq 5, or Eq 6, they shall be reported as “Apparent Vapor Pressure 5 __ torr at __C __F, and Molecular Weight 5 __, calculated as polyol ester,” “...diester,” or “...petroleum,” as appropriate. 11.3 Iftheresultsareobtainedasindicatedin9.4orNote5, they shall be reported as “Apparent Vapor Pressure 5 __ torr at__C __F and 0 to __ percent evaporated.” The molecular weight shall be reported only if the test was conducted at 477K 400F or a separate test at this temperature was made. 12. Precision 12.1 No independent precision statement can be issued at this time. However, the statement in Test D972 may be used as a guide. Applying the exponent 1.164 from Coburnspaper 2 totheTestD972statementresultsin the following criteria for apparent vapor pressure results 12.1.1 RepeatabilityThe difference between two test results,obtainedbythesameoperatorwiththesameapparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct operation of the test , exceed the following values only in one case in twenty 6 12.1.2 ReproducibilityThe difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test , exceed the following values only in one case in twenty 23 12.2 Similarly, from Test D2595, for use with that apparatus 12.2.1 RepeatabilityThe difference between two test results,obtainedbythesameoperatorwiththesameapparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct operation of the test , exceed the following values only in one case in twenty 23 TABLE 1 Estimated Time to Evaporate 5, h A Flash Point Test Temperature, K F K F 394 250 422 300 450 350 477 400 505 450 533 500 422 300 2.7 0.9 0.3 0.1 ... ... 450 350 8.1 2.7 0.9 0.3 0.1 ... 477 400 24.3 8.1 2.7 0.9 0.3 0.1 505 450 72.9 24.3 8.1 2.7 0.9 0.3 533 500 ... 72.9 24.3 8.1 2.7 0.9 561 550 ... ... 72.9 24.3 8.1 2.7 589 600 ... ... ... 72.9 24.3 8.1 A This table may be extended by means of equation Estima