ASTM D2878-21

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Designation: D2878 − 10 (Reapproved 2016) D2878 − 21
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method covers a calculation procedure for converting data obtained by Test Method D972 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 K to 535 K (250 °F to 500 °F). 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 WARNING—Mercury has been designated by many regulatory agencies as a hazardous materialsubstance that can cause
central nervous system, kidney and liver damage. serious medical issues. Mercury, or its vapor, may has been demonstrated to be
hazardous to health and corrosive to materials. Caution should be taken Use caution when handling mercury and mercury
containing mercury-containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA’s
website—http://www.epa.gov/mercury/faq.htm—for additional information. Users should be aware (SDS) for additional informa-
tion. The potential exists that selling mercury or mercury containing products into your state or country may be prohibited by
law.mercury-containing products, or both, is prohibited by local or national law. Users must determine legality of sales in their
location.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability or regulatory limitations prior to use. For specific warning statements, see 6.2, 7.1, 8.2, and Annex A2.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
This test method is under the jurisdiction of Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.L0.07 on Engineering Sciences of High Performance Fluids and Solids (Formally D02.1100).
Current edition approved Jan. 1, 2016Dec. 1, 2021. Published February 2016February 2022. Originally approved in 1970. Last previous edition approved in 20102016
as D2878 – 10.D2878 – 10 (2016). DOI: 10.1520/D2878-10R16.10.1520/D2878-21.
Coburn, J. F., “Lubricant Vapor Pressure Derived from Evaporation Loss,” Transactions, American Society of Lubricating Engineers, ASLTA, Vol 12 , 1969, pp. 129–134.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2878 − 21
A240/A240M Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and
for General Applications
D92 Test Method for Flash and Fire Points by Cleveland Open Cup Tester
D972 Test Method for Evaporation Loss of Lubricating Greases and Oils
D2503 Test Method for Relative Molecular Mass (Molecular Weight) of Hydrocarbons by Thermoelectric Measurement of
Vapor Pressure
D2595 Test Method for Evaporation Loss of Lubricating Greases Over Wide-Temperature Range
D2883 Test Method for Reaction Threshold Temperature of Liquid and Solid Materials (Withdrawn 2016)
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
E659 Test Method for Autoignition Temperature of Chemicals
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.1.2 apparent vapor pressure (p), n—the time-averaged value of the vapor pressure from the start to the end of the evaporation
test.
3.1.2.1 Discussion—
While this may include some effects of differences in nonideality of the vapor, heat of vaporization, surface tension, and viscosity
between the m-terphenyl and the lubricating oil, these factors have been demonstrated to be negligible. Unless stated, this average
shall cover the range 00 % to 55 % 6 1 %.
3.1.3 cell constant (k), n—the ratio of the amount of m-terphenyl or lubricating oil carried off per unit volume of gas to that
predicted by Dalton’s law.
k 5 22.41 PW/VpM (1)
where:
k = call constant
P = ambient atmospheric pressure, torr
W = mass of lubricant evaporated, g
V = volume of gas passed through all litres at 273 K and 101.3 kPa (760 torr)
p = apparent vapor pressure, torr
M = mole average molecular weight of lubricant vapor, g/mole
T = test temperature, K
It has been empirically determined that for m-terphenyl in air
k 5 0.1266 2 12.60/~ T 2 273! (2)
and that the cell constant is independent of the composition of the lubricant.
3.1.4 Test Method D972 is normally run with air, which may cause changes in easily oxidized fluids. In such cases, use of common
reactive gas nitrogen and recalibration to obtain a slightly different cell constant (k') is mandatory.
4. Summary of Test Method
4.1 The test is run at the selected temperature for a sufficient 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. Little
weight is given by the procedure to the presence of low concentrations of volatile impurities.
The last approved version of this historical standard is referenced on www.astm.org.
D2878 − 21
5.2 Vapor pressure, per se, is a thermodynamic property that is dependent only upon composition and temperature for stable
systems. In the present method, 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 Evaporation Cell, as described in Annex A1.
6.2 Air Supply System, capable of supplying to the cell the required flow of air free of entrained particles (Warning—Compressed
gas under high pressure. Use with extreme caution in the presence of combustible material, since the autoignition temperatures of
most organic compounds in air are drastically reduced at elevated pressures. See Annex A2.1.). A 410 mm (16 in.) length of 1 in.
diameter pipe packed with glass wool has been found satisfactory for filtering the air.
6.3 Oil Bath, as described in Annex A1.
NOTE 2—Other constant-temperature baths may be used if the exit air passing over the grease sample is at the test temperature (60.5 K (1 °F)).
6.4 Temperature Measuring Devices—Resistance thermometers, thermocouples, or liquid-in-glass thermometers calibrated to
accuracy within 60.5 ºC (61.0 ºF) may be used. The use of mercury-in-glass thermometers of equal accuracy is permitted,
although it is discouraged.
6.5 Flowmeter —A rotameter calibrated to deliver air at a rate of 2.583 g ⁄min 6 0.02 g ⁄min between 289 K and 302 K (60 °F and
85 °F) (2 L ⁄min at standard temperature and pressure). It shall be 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 Equipment
7.1 It is assumed that equipment conforming to Test Method D972 in design and installation needs no calibration. If questions
arise, carry out the procedure using m-terphenyl (Warning—Harmful or fatal if swallowed. See A2.2.) of good commercial quality.
The following two points shall be determined:
Temperature Evaporation to Conform
K °F Time, h to Eq 2, g
395 250 22 0.267 ± 0.027
420 300 6.5 0.503 ± 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
for k' similar to Eq 2 and use it in Section 10. When use of nonreactive gas is required, this calibration is necessary as standard
cell constants are not valid for gases other than air.
7.2 If the apparatus specified in Test Method D2595 is to be used, it shall be calibrated as described in 7.1.
8. Procedure
8.1 Weigh the clean test specimen cup and hood to the nearest 1 mg. Transfer, by means of a pipet, 10.00 g 6 0.05 g of 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 60.5 K (61 °F)) at which the test is to be made by immersing the cell in it, as shown in Fig. 1. Allow
The sole source of supply of the apparatus known to the committee at this time is Flowrater meter, Fisher and Porter Co., Hatboro, PA. If you are aware of alternative
suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical
committee, which you may attend.
D2878 − 21
FIG. 1 Evaporation Test Cell
the cell to remain in the bath at least ⁄2 h before beginning the test. During this period, allow clean air (Warning—Compressed
gas under high pressure. Use with extreme caution in the presence of combustible material, since the autoignition temperatures of
most organic compounds in air are drastically reduced at elevated pressures. See Annex A2.1.) to flow through the cell at the
prescribed rate, 2.583 g ⁄min 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. Pas
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