ASTM D2878-95(2000)e1
(Test Method)Standard Test Method for Estimating Apparent Vapor Pressures and Molecular Weights of Lubricating Oils
Standard Test Method for Estimating Apparent Vapor Pressures and Molecular Weights of Lubricating Oils
SCOPE
1.1 This test method provides a calculation procedure for converting data obtained by Test Method D 972 to apparent vapor pressures and molecular weights. It has been demonstrated to be applicable to petroleum-based and synthetic ester lubricating oils, at temperatures of 395 to 535K (250 to 500oF). However, its applicability to lubricating greases has not been established.
Note 1--Most 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.
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 appropriate safety and health practices and determine the applicability or regulatory limitations prior to use. For specific hazard statements, see 6.2, 7.1, and 8.2.
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An American National Standard
e1
Designation:D2878–95 (Reapproved 2000)
Standard Test Method for
Estimating Apparent Vapor Pressures and Molecular
Weights of Lubricating Oils
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.
e NOTE—Warning notes were placed in the text editorially in November 2000.
1. Scope D2503 Test Method for Molecular Weight (Relative Mo-
lecular Mass) of Hydrocarbons by Thermoelectric Mea-
1.1 This test method provides a calculation procedure for
surement of Vapor Pressure
converting data obtained by Test Method D972 to apparent
D2595 Test Method for Evaporation Loss of Lubricating
vapor pressures and molecular weights. It has been demon-
Greases over Wide Temperature Range
strated to be applicable to petroleum-based and synthetic ester
2 D2883 TestMethodforReactionThresholdTemperatureof
lubricating oils, at temperatures of 395 to 535K (250 to
Liquid and Solid Materials
500°F). However, its applicability to lubricating greases has
E1 Specification for ASTM Thermometers
not been established.
E659 Test Method forAutoignition Temperature of Liquid
NOTE 1—Most lubricants boil over a fairly wide temperature range, a 6
Chemicals
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
3. Terminology
much as 100 times that over the range 4.9 to 5.0% evaporated.
3.1 Definitions of Terms Specific to This Standard:
1.2 The values stated in SI units are to be regarded as the
3.1.1 apparent vapor pressure (p), n—the time-averaged
standard. In cases in which materials, products, or equipment
value of the vapor pressure from the start to the end of the
are available in inch-pound units only, SI units are omitted.
evaporation test.
1.3 This standard does not purport to address all of the
3.1.1.1 Discussion—Whilethismayincludesomeeffectsof
safety concerns, if any, associated with its use. It is the
differences in nonideality of the vapor, heat of vaporization,
responsibility of the user of this standard to establish appro-
surface tension, and viscosity between the m-terphenyl and the
priate safety and health practices and determine the applica-
lubricating oil, these factors have been demonstrated to be
bility or regulatory limitations prior to use.Forspecifichazard 6
negligible. Unless stated, this average shall cover the range 0
statements, see 6.2, 7.1, and 8.2.
to 5 61%.
3.1.2 cell constant (k), n—the ratio of the amount of
2. Referenced Documents
m-terphenylorlubricatingoilcarriedoffperunitvolumeofgas
2.1 ASTM Standards:
to that predicted by Dalton’s law.
A240/A240M Specification for Heat-Resisting Chromium
k 522.41 PW/VpM (1)
and Chromium-Nickel Stainless Steel Plate, Sheet, and
Strip for Pressure Vessels
where:
D92 Test Method for Flash and Fire Points by Cleveland
k = call constant
Open Cup
P = ambient atmospheric pressure, torr
D972 Test Method for Evaporation Loss of Lubricating
W = mass of lubricant evaporated, g
Greases and Oils V = volume of gas passed through all litres at 273K and
101.3 kPa (760 torr)
p = apparent vapor pressure, torr
1 M = mole average molecular weight of lubricant vapor,
This test method is under the jurisdiction of Committee D02 on Petroleum
ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.11on g/mole
Engineering Sciences of High Performance Fluids and Solids.
T = test temperature, K
Current edition approved Jan. 15, 1995. Published March 1995. Originally
Ithasbeenempiricallydeterminedthatfor m-terphenylinair
published as D2878–70. Last previous edition D2878–93.
Coburn, J. F., “Lubricant Vapor Pressure Derived from Evaporation Loss,”
Transactions,AmericanSocietyofLubricatingEngineers,ASLTA,Vol12,1969,pp.
129–134.
3 5
Annual Book of ASTM Standards, Vol 01.03. Annual Book of ASTM Standards, Vol 14.03.
4 6
Annual Book of ASTM Standards, Vol 05.01. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D2878
k 50.1266 212.60/~ T 2273! (2) questions arise, carry out the procedure using m-terphenyl
(Warning—Harmful or fatal if swallowed. SeeA2.2.) of good
and that the cell constant is independent of the composition
commercial quality. The following two points shall be deter-
of the lubricant.
mined:
3.1.3 Test Method D972 is normally run with air, which
Temperature Evaporation to Conform
may cause changes in easily oxidized fluids. In such cases, use
K °F Time, h to Eq 2, g
of common reactive gas nitrogen and recalibration to obtain a
slightly different cell constant (k8) is mandatory.
395 250 22 0.267 6 0.027
420 300 6.5 0.503 6 0.050
4. Summary of Test Method
If the data do not fall within the above ranges, check flow
4.1 Thetestisrunattheselectedtemperatureforasufficient
rate and temperature. If these are correct, prepare a substitute
time to give the selected amount of evaporation, which is 5 6
equation for k8 similar to Eq 2 and use it in Section 10. When
1% unless otherwise specified. This evaporation rate is com-
use of nonreactive gas is required, this calibration is necessary
pared with a standard value for pure m-terphenyl to yield the
as standard cell constants are not valid for gases other than air.
apparent vapor pressure and molecular weight of the lubricat-
7.2 IftheapparatusspecifiedinTestMethodD2595istobe
ing oil as defined in Section 3.
used, it shall be calibrated as described in 7.1.
5. Significance and Use
8. Procedure
5.1 The vapor pressure of a substance as determined by
8.1 Weigh the clean test specimen cup and hood to the
measurement of evaporation reflects a property of the bulk
nearest 1 mg. Transfer, by means of a pipet, 10.00 6 0.05 g of
sample. Little weight is given by the procedure to the presence
test specimen to the cup. Assemble the cup and hood, being
of low concentrations of volatile impurities.
careful not to splash oil on the underside of the hood. Weigh
5.2 Vaporpressure, per se,isathermodynamicpropertythat
the assembly and record the net test specimen weight to the
isdependentonlyuponcompositionandtemperatureforstable
nearest 1 mg.
systems. In the present method, composition changes occur
8.2 With cover in place, but without the hood and test
during the course of the test so that the contribution of minor
specimen cup attached, allow the evaporation cell to acquire
amounts of volatile impurities is minimized.
the temperature of the bath (controlled to 60.5K (61°F)) at
which the test is to be made by immersing the cell in it, as
6. Apparatus
shown in Fig. 1.Allow the cell to remain in the bath at least ⁄2
6.1 Evaporation Cell, as described in Annex A1.
h before beginning the test. During this period, allow clean air
6.2 Air Supply System, capable of supplying to the cell the
(Warning—Compressed gas under high pressure. Use with
required flow of air free of entrained particles (Warning—
extreme caution in the presence of combustible material, since
Compressedgasunderhighpressure.Usewithextremecaution
theautoignitiontemperaturesofmostorganiccompoundsinair
in the presence of combustible material, since the autoignition
are drastically reduced at elevated pressures. SeeAnnexA2.1.)
temperatures of most organic compounds in air are drastically
to flow through the cell at the prescribed rate, 2.583 6 0.02
reduced at elevated pressures. See Annex A2.1.). A 410-mm
g/min (2 L/min at standard temperature and pressure), as
(16-in.) length of 1-in. diameter pipe packed with glass wool
indicated by the rotameter. Then remove the cover, thread and
has been found satisfactory for filtering the air.
weighedhoodandsamplecupintoplace,andreplacethecover.
6.3 Oil Bath, as described in Annex A1.
Tighten the three knurled cover-tightening screws securely to
prevent air leakage under the cover. Pass clean air through the
NOTE 2—Other constant-temperature baths may be used if the exit air
passing over the grease sample is at the test temperature (60.5K (1°F)).
cell for the required period. (Warning—Do not perform this
test with air at temperatures in excess of the autoignition
6.4 Thermometers—ASTM thermometers graduated in ei-
temperatureofthetestspecimenasdeterminedbyTestMethod
therCelsiusorFahrenheitdegreesandhavingarangefrom−5
E659 or Test Method D2883, or both.)
to400°C(20to760°F)andconformingtotherequirementsfor
8.3 At the end of the test period, remove the assembled test
Thermometers 3C or 3F, respectively, as described in Specifi-
specimen cup and hood from the cell, and allow to cool to
cation E1.
room temperature. Determine the net weight of the sample to
6.5 Flowmeter —A rotameter calibrated to deliver air at a
the nearest 1 mg.
rate of 2.583 6 0.02 g/min between 289 and 302K (60 and
85°F) (2 L/min at standard temperature and pressure). It shall
9. Determination of Molecular Weight and Apparent
befurnishedwithaneedlevalveandmountedasshowninFig.
Vapor Pressure
1.
9.1 If a value of M is already available from Test Method
6.6 Oil Sample Cup, as described in Fig. 1 and A1.1.2.
D2503 or equivalent, 9.2-9.4 and 10.1 may be omitted, even
7. Calibration of Equipment
though this value is for the whole lubricant instead of the part
vaporized, as the calculation is not very sensitive to M error.
7.1 ItisassumedthatequipmentconformingtoTestMethod
9.2 Conduct a test on the sample in accordance with the
D972 in design and installation needs no calibration. If
procedure in Section 7, at 477K (400°F). The proper test time
The Flowrater meter manufactured by Fisher and Porter Co., Hatboro, PA, has
been found satisfactory. Santowax,M.,MonsantoChemicalCo.,St.Louis,MO,hasprovedsatisfactory.
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