1、Designation: D2878 10Standard 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 case of revision, th
2、e 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 D972 to apparentv
3、apor 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 over a fairly wid
4、e 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 thestandard. In ca
5、ses in which materials, products, or equipmentare available in inch-pound units only, SI units are omitted.1.3 WARNINGMercury has been designated by manyregulatory agencies as a hazardous material that can causecentral nervous system, kidney and liver damage. Mercury, orits vapor, may be hazardous t
6、o health and corrosive tomaterials. Caution should be taken when handling mercury andmercury containing products. See the applicable product Ma-terial Safety Data Sheet (MSDS) for details and EPAswebsitehttp:/www.epa.gov/mercury/faq.htmfor addi-tional information. Users should be aware that selling
7、mercuryor mercury containing products into your state or country maybe prohibited by law.1.4 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 practice
8、s 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, Sheet, and Strip for PressureVessels
9、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 Measure-ment of Vapor PressureD2595
10、 Test Method for Evaporation Loss of LubricatingGreases Over Wide-Temperature RangeD2883 Test Method for Reaction Threshold Temperature ofLiquid and Solid MaterialsE659 Test Method for Autoignition Temperature of LiquidChemicals3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 a
11、pparent 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 the vapor, heat of vaporization,surface tension, and viscosity between the m-terphenyl and
12、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 lubricating oil carried off per unit volume of gasto that predicted by Daltons law.k 5 22.41 PW /V
13、pM (1)where:1This 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 Oct. 1, 2010. Published October 2010. Originallya
14、pproved in 1970. Last previous edition approved in 2009 as D287895(2009).DOI: 10.1520/D2878-10.2Coburn, J. F., “Lubricant Vapor Pressure Derived from Evaporation Loss,”Transactions, American Society of Lubricating Engineers, ASLTA, Vol 12 , 1969,pp. 129134.3For referenced ASTM standards, visit the A
15、STM 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, PO Box C700, West Conshohocken, PA 19428-2959, Uni
16、ted States.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, torrM = mole average molecular weight of lubricant vapor,g/moleT = test temperature, KIt has be
17、en 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 air, whichmay cause changes in easily oxidized fluids. In such cases, useof common reactive ga
18、s 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 amount of evaporation, which is 5 61 % unless otherwise specified. This evaporation rate is co
19、m-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 substance as determined bymeasurement of evaporation reflects a property of the bulksample. L
20、ittle 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 temperature for stablesystems. In the present method, composition changes occurduring the course of th
21、e 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 therequired flow of air free of entrained particles (WarningCompressed gas under high pressure. Use w
22、ith 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.) length of 1-in. diameter pipe packed with glass woolhas been found satisfactory for filteri
23、ng 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 Temperature Measuring DevicesResistance thermom-eters, thermocouples, or liquid-in-glass thermometers cali-bra
24、ted to accuracy within 60.5C (61.0F) may be used. Theuse of mercury-in-glass thermometers of equal accuracy ispermitted, although it is discouraged.6.5 Flowmeter4A rotameter calibrated to deliver air at arate of 2.583 6 0.02 g/min between 289 and 302K (60 and85F) (2 L/min at standard temperature and
25、 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 design and installation needs no calibration. Ifquestions arise, carry
26、 out the procedure using m-terphenyl(WarningHarmful or fatal if swallowed. See A2.2.) of goodcommercial quality. The following two points shall be deter-mined:Temperature Evaporation to Conformto Eq 2, gK F Time, h395 250 22 0.267 6 0.027420 300 6.5 0.503 6 0.050If the data do not fall within the ab
27、ove 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 constants are not valid for gases other than air.7.2 If the apparatus
28、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 to the cup. Assemble the cup and hood, beingcareful not to splash oil o
29、n 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 temperature of the bath (controlled to 60.5K (61F) atwhich the test is to be
30、 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 caution in the presence of combustible material, sincethe autoignition temp
31、eratures of most organic compounds in airare drastically reduced at elevated pressures. See Annex A2.1.)to flow through the cell at the prescribed rate, 2.583 6 0.02g/min (2 L/min at standard temperature and pressure), asindicated by the rotameter. Then remove the cover, thread andweighed hood and s
32、ample 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 with air at temperatures in excess of the autoignitiontemperature of t
33、he test specimen as determined by Test MethodE659 or Test Method D2883, or both.)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 In
34、ternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.D2878 1028.3 At the end of the test period, remove the assembled testspecimen cup and hood from the cell, and allow to cool toroom temperature. Determine
35、 the net weight of the sample tothe nearest 1 mg.9. Determination of Molecular Weight and ApparentVapor Pressure9.1 If a value of M is already available from Test 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
36、, 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 test timeto evaporate 5 % (0.500 g) may be estimated from the flashpoint of the lubricant as measured by Test Method D92, fromTable 1.FIG. 1
37、 Evaporation Test CellD2878 103NOTE 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 synthetic and redistilled petroleum oils, the varia-tion of W/t with W is not great, and the 5 % point shall bea
38、pproximated 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 half and twice that time. These readings may allbe obtained on one sample by stop and start operation of
39、 theapparatus.9.4 When a single data point that does not fall within the 56 1 % evaporated range is used (as is often justifiable onsynthetic oils) or the 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
40、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. Calculations10.1 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
41、 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 greateraccuracy 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
42、 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 thestandard 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 shal
43、l 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, as 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
44、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(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 =
45、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 = apparent 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
46、 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 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(_
47、_ F), and Molecular Weight=_, calculated as polyolester,” “.diester,” or “.petroleum,” as appropriate.11.3 If the results are obtained as indicated in 8.2 or 9.4,they shall be reported as “Apparent Vapor Pressure=_torrat_ _ C (_ _ F) and 0 to _ _ percent evaporated.” Themolecular weight shall be rep
48、orted only if the test wasconducted at 477K (400F) or a separate test at this tempera-ture was made.TABLE 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
49、 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 table may be extended by means of equation:Estimated Hours = 0.9 log10.0095(F 1.8T + 460)(3)TABLE 2 Standard Cell ConstantsTemperatureCell Constant2KF394 250 0.02247422 300 0.04204450 350 0.05540477 400 0.06483505 450 0.07229533 500 0.07814D2878 10412. Precision and Bias12.1 No independent precision statement can be issued atthis time. However, the statement in Test Meth
