1、Designation: D2878 95 (Reapproved 2009)Standard Test Method forEstimating Apparent Vapor Pressures and MolecularWeights of Lubricating Oils1This standard is issued under the fixed designation D2878; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se 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 a calculation procedure forconverting data obtained by Test Method
3、 D972 to apparentvapor pressures and molecular weights. It has been demon-strated to be applicable to petroleum-based and synthetic esterlubricating oils,2at temperatures of 395 to 535K (250 to500F). However, its applicability to lubricating greases hasnot been established.NOTE 1Most lubricants boil
4、 over a fairly wide temperature range, afact recognized in discussion of their vapor pressures. For example, theapparent vapor pressure over the range 0 to 0.1 % evaporated may be asmuch as 100 times that over the range 4.9 to 5.0 % evaporated.1.2 The values stated in SI units are to be regarded as
5、thestandard. In cases in which materials, products, or equipmentare available in inch-pound units only, SI units are omitted.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 app
6、ro-priate safety and health practices and determine the applica-bility or regulatory limitations prior to use. For specificwarning statements, see 6.2, 7.1, 8.2, and Annex A2.2. Referenced Documents2.1 ASTM Standards:3A240/A240M Specification for Chromium and Chromium-Nickel Stainless Steel Plate, S
7、heet, and Strip for PressureVessels and for General ApplicationsD92 Test Method for Flash and Fire Points by ClevelandOpen Cup TesterD972 Test Method for Evaporation Loss of LubricatingGreases and OilsD2503 Test Method for Relative Molecular Mass (Molecu-lar Weight) of Hydrocarbons by Thermoelectric
8、 Measure-ment of Vapor PressureD2595 Test Method for Evaporation Loss of LubricatingGreases Over Wide-Temperature RangeD2883 Test Method for Reaction Threshold Temperature ofLiquid and Solid MaterialsE1 Specification for ASTM Liquid-in-Glass ThermometersE659 Test Method for Autoignition Temperature
9、of LiquidChemicals3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 apparent vapor pressure (p), nthe time-averagedvalue of the vapor pressure from the start to the end of theevaporation test.3.1.1.1 DiscussionWhile this may include some effects ofdifferences in nonideality of t
10、he vapor, heat of vaporization,surface tension, and viscosity between the m-terphenyl and thelubricating oil, these factors have been demonstrated to benegligible. Unless stated, this average shall cover the range 0 to5 6 1%.3.1.2 cell constant (k), nthe ratio of the amount ofm-terphenyl or lubricat
11、ing oil carried off per unit volume of gasto that predicted by Daltons law.k 5 22.41 PW /VpM (1)where:k = call constantP = ambient atmospheric pressure, torrW = mass of lubricant evaporated, gV = volume of gas passed through all litres at 273K and101.3 kPa (760 torr)p = apparent vapor pressure, torr
12、M = mole average molecular weight of lubricant vapor,g/mole1This test method is under the jurisdiction of Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.11 onEngineering Sciences of High Performance Fluids and Solids.Current edition approved Oc
13、t. 1, 2009. Published November 2009. Originallyapproved in 1970. Last previous edition approved in 2005 as D287895(2005).DOI: 10.1520/D2878-95R09.2Coburn, J. F., “Lubricant Vapor Pressure Derived from Evaporation Loss,”Transactions, American Society of Lubricating Engineers, ASLTA, Vol 12, 1969,pp.
14、129134.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive,
15、PO Box C700, West Conshohocken, PA 19428-2959, United States.T = test temperature, KIt has been empirically determined that for m-terphenyl in airk 5 0.1266 2 12.60/ T 2 273! (2)and that the cell constant is independent of the compositionof the lubricant.3.1.3 Test Method D972 is normally run with a
16、ir, whichmay cause changes in easily oxidized fluids. In such cases, useof common reactive gas nitrogen and recalibration to obtain aslightly different cell constant (k8) is mandatory.4. Summary of Test Method4.1 The test is run at the selected temperature for a sufficienttime to give the selected a
17、mount of evaporation, which is 5 61 % unless otherwise specified. This evaporation rate is com-pared with a standard value for pure m-terphenyl to yield theapparent vapor pressure and molecular weight of the lubricat-ing oil as defined in Section 3.5. Significance and Use5.1 The vapor pressure of a
18、substance as determined bymeasurement of evaporation reflects a property of the bulksample. Little weight is given by the procedure to the presenceof low concentrations of volatile impurities.5.2 Vapor pressure, per se, is a thermodynamic property thatis dependent only upon composition and temperatu
19、re for stablesystems. In the present method, composition changes occurduring the course of the test so that the contribution of minoramounts of volatile impurities is minimized.6. Apparatus6.1 Evaporation Cell, as described in Annex A1.6.2 Air Supply System, capable of supplying to the cell therequi
20、red flow of air free of entrained particles (WarningCompressed gas under high pressure. Use with extreme cautionin the presence of combustible material, since the autoignitiontemperatures of most organic compounds in air are drasticallyreduced at elevated pressures. See Annex A2.1.). A 410-mm(16-in.
21、) length of 1-in. diameter pipe packed with glass woolhas been found satisfactory for filtering the air.6.3 Oil Bath, as described in Annex A1.NOTE 2Other constant-temperature baths may be used if the exit airpassing over the grease sample is at the test temperature (60.5K (1F).6.4 ThermometersASTM
22、thermometers graduated in ei-ther Celsius or Fahrenheit degrees and having a range from 5to 400C (20 to 760F) and conforming to the requirements forThermometers 3C or 3F, respectively, as described in Specifi-cation E1.6.5 Flowmeter4A rotameter calibrated to deliver air at arate of 2.583 6 0.02 g/mi
23、n between 289 and 302K (60 and85F) (2 L/min at standard temperature and pressure). It shallbe furnished with a needle valve and mounted as shown in Fig.1.6.6 Oil Sample Cup, as described in Fig. 1 and A1.1.2.7. Calibration of Equipment7.1 It is assumed that equipment conforming to Test MethodD972 in
24、 design and installation needs no calibration. Ifquestions arise, carry out the procedure using m-terphenyl(WarningHarmful or fatal if swallowed. See A2.2.) of goodcommercial quality.5The following two points shall be deter-mined:Temperature Evaporation to Conformto Eq 2, gK F Time, h395 250 22 0.26
25、7 6 0.027420 300 6.5 0.503 6 0.050If the data do not fall within the above ranges, check flowrate and temperature. If these are correct, prepare a substituteequation for k8 similar to Eq 2 and use it in Section 10. Whenuse of nonreactive gas is required, this calibration is necessaryas standard cell
26、 constants are not valid for gases other than air.7.2 If the apparatus specified in Test Method D2595 is to beused, it shall be calibrated as described in 7.1.8. Procedure8.1 Weigh the clean test specimen cup and hood to thenearest 1 mg. Transfer, by means of a pipet, 10.00 6 0.05 g oftest specimen
27、to the cup. Assemble the cup and hood, beingcareful not to splash oil on the underside of the hood. Weighthe assembly and record the net test specimen weight to thenearest 1 mg.8.2 With cover in place, but without the hood and testspecimen cup attached, allow the evaporation cell to acquirethe tempe
28、rature of the bath (controlled to 60.5K (61F) atwhich the test is to be made by immersing the cell in it, asshown in Fig. 1. Allow the cell to remain in the bath at least12h before beginning the test. During this period, allow clean air(WarningCompressed gas under high pressure. Use withextreme caut
29、ion in the presence of combustible material, sincethe autoignition temperatures of most organic compounds in airare drastically reduced at elevated pressures. SeeAnnexA2.1.)to flow through the cell at the prescribed rate, 2.583 6 0.02g/min (2 L/min at standard temperature and pressure), asindicated
30、by the rotameter. Then remove the cover, thread andweighed hood and sample cup into place, and replace the cover.Tighten the three knurled cover-tightening screws securely toprevent air leakage under the cover. Pass clean air through thecell for the required period. (WarningDo not perform thistest w
31、ith air at temperatures in excess of the autoignitiontemperature of the test specimen as determined by Test MethodE659 or Test Method D2883, or both.)8.3 At the end of the test period, remove the assembled testspecimen cup and hood from the cell, and allow to cool toroom temperature. Determine the n
32、et weight of the sample tothe nearest 1 mg.4The sole source of supply of the apparatus known to the committee at this timeis Flowrater meter, Fisher and Porter Co., Hatboro, PA. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments
33、 will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.5The sole source of supply of the apparatus known to the committee at this timeis Santowax, M., Monsanto Chemical Co., St. Louis, MO. If you are aware ofalternative suppliers, please provide
34、this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.D2878 95 (2009)29. Determination of Molecular Weight and ApparentVapor Pressure9.1 If a value of M is already available from T
35、est MethodD2503 or equivalent, 9.2-9.4 and 10.1 may be omitted, eventhough this value is for the whole lubricant instead of the partvaporized, as the calculation is not very sensitive to M error.9.2 Conduct a test on the sample in accordance with theprocedure in Section 7, at 477K (400F). The proper
36、 test timeto evaporate 5 % (0.500 g) may be estimated from the flashpoint of the lubricant as measured by Test Method D92, fromTable 1.NOTE 3The need for a run at 477K (400F) is, created by lack ofexact values for the first two constants in Eq 3, Eq 4, and Eq 5 for othertemperatures.9.3 For syntheti
37、c and redistilled petroleum oils, the varia-tion of W/t with W is not great, and the 5 % point shall beapproximated by linear interpolation of two points taken atdifferent W values. For single-distilled petroleum or unknownoils, three points shall be plotted, representing the estimatedtime and also
38、half and twice that time. These readings may allbe obtained on one sample by stop and start operation of theapparatus.FIG. 1 Evaporation Test CellD2878 95 (2009)39.4 When a single data point that does not fall within the 56 1 % evaporated range is used (as is often justifiable onsynthetic oils) or t
39、he evaporation is measured at some otherlevel of W, this fact shall be reported in Section 11.9.5 The test for apparent vapor pressure is conducted inaccordance with Section 8 for the estimated time at the selectedtemperature. If the 5 6 1 % criterion is not met, proceed as in9.3.10. Calculations10.
40、1 Calculation of Molecular Weight:10.1.1 Use the evaporation time, t, (in seconds) obtained in9.3 to evaporate 5 6 1%.10.1.2 Calculate the molecular weights of lubricants ingeneral as follows:log M 5 3.028 2 0.164 log 10 335 PW/t! (3)10.1.3 For lubricants of known composition, slightly greateraccura
41、cy is obtained with special equations:10.1.3.1 For polyol esters:log M 5 3.181 2 0.207 log 10 335 PW/t! (4)10.1.3.2 For dibasic esters:log M 5 3.089 2 0.190 log 10 335 PW/t! (5)10.1.3.3 For mineral oils:log M 5 2.848 2 0.106 log 10 335 PW/t! (6)10.1.4 The molecular weight equations all contain thest
42、andard value of k at 477K (400F) from Table 2. If a changegreater than 63 % in this value is caused by the calibration inSection 7, adjustments shall be made in the constant 10 335 bymultiplying it by the factor (k/k8).10.2 Calculation of Apparent Vapor Pressure:10.2.1 Use the molecular weight, M, a
43、s calculated in 10.1 orpredetermined in 9.1 to calculate the vapor pressure as follows:p 5 672 PW/tkM (7)where k is obtained from Table 2. Use Eq 2 to extend thistable. If a special equation was required in 7.1, use it ratherthan Table 2 or Eq 2.10.2.2 For the special case of lubricants run at 477K(
44、400F) for 6.5 h as required in several military aircraft engineoil specifications, with P = 760 torr:log p 5 1.164 log 10W! 2 1.255 (8)where 10 W = percent evaporated from a 10-g sample.10.2.3 These results may be converted to SI units by theequations:p8 5 133.32p and P8 5 133.32P (9)where:p8 = appa
45、rent vapor pressure, PaP8 = ambient atmospheric pressure, Pa11. Report11.1 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=_ torr at _ _ C (_ _ F), andMolecular Weight=_.”11.2 If the results are obtained
46、in accordance with 9.1, 9.2,9.3, and 9.5, and calculated by Eq 4, Eq 5, or Eq 6, they shallbe reported as “Apparent Vapor Pressure=_torr at _ _ C(_ _ F), and Molecular Weight=_, calculated as polyolester,” “.diester,” or “.petroleum,” as appropriate.11.3 If the results are obtained as indicated in 8
47、.2 or 9.4,they shall be reported as “Apparent Vapor Pressure=_torrat_ _ C (_ _ F) and 0 to _ _ percent evaporated.” Themolecular weight shall be reported only if the test wasconducted at 477K (400F) or a separate test at this tempera-ture was made.12. Precision12.1 No independent precision statement
48、 can be issued atthis time. However, the statement in Test Method D972 may beused as a guide. Applying the exponent 1.164 from Coburnspaper2to the Test Method D972 statement results in thefollowing criteria for apparent vapor pressure results:12.1.1 RepeatabilityThe difference between two test re-su
49、lts, obtained by the same operator with the same apparatusunder constant operating conditions on identical test material,would in the long run, in the normal and correct operation ofTABLE 1 Estimated Time to Evaporate 5 %, hAFlash 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 0.1505 450 72.9 24.3 8.1 2.7 0.9 0.3533 500 . 72.9 24.3 8.1 2.7 0.9561 550 . . 72.9 24.3 8.1 2.7589 600 . . . 72.9 24.3 8.1AThis
