ASTM D942-23a

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D942 − 23 D942 − 23a
Designation: 142/23
Standard Test Method for
Oxidation Stability of Lubricating Greases by the Oxygen
1,2
Pressure Vessel Method
This standard is issued under the fixed designation D942; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method determines resistance of lubricating greases to oxidation when stored statically in an oxygen atmosphere in
a sealed system at an elevated temperature under conditions of test.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.2.1 Exception—Pressure measurement appears in kPa with psi provided for information only.
1.2.2 Exception—In Fig. A1.1, A1.1, and Appendix X1, all dimensions are in millimeters, with inches provided in parentheses for
information only.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific hazard statements see Sections 6 and 7.
1.4 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:
A240/A240M Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and
for General Applications
D525 Test Method for Oxidation Stability of Gasoline (Induction Period Method)
E1 Specification for ASTM Liquid-in-Glass Thermometers
E2877 Guide for Digital Contact Thermometers
This test method is under the jurisdiction of ASTM International Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility
of ASTM Subcommittee D02.09.0E on Oxidation of Greases. The technically equivalent standard as referenced is under the jurisdiction of the Energy Institute Subcommittee
SC-C-6.
Current edition approved Nov. 1, 2023Dec. 1, 2023. Published November 2023December 2023. Originally approved in 1947. Last previous edition approved in 20192023
as D942 – 19.D942 – 23. DOI: 10.1520/D0942-23.10.1520/D0942-23A.
This test method has been developed through the cooperative effort between ASTM and the Energy Institute, London. ASTM and IP standards were approved by ASTM
and EI technical committees as being technically equivalent but that does not imply both standards are identical.
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
D942 − 23a
2.2 Other Standards:
IP Specification for Standard IP Thermometers
BS 970:1983 Part I, Section S
3. Summary of Test Method
3.1 The sample of grease is oxidized in a pressure vessel heated to 100 °C (212 °F) and filled with oxygen at 750 kPa (109 psi).
Pressure is observed and recorded at stated intervals. The degree of oxidation after a given period of time is determined by the
corresponding decrease in oxygen pressure.
NOTE 1—The pressure vessel has been referred to as “a bomb” in previous issues of this test method.
NOTE 2—The accepted unit of pressure is the pascal (Pa) for ASTM methods and will be parenthetically included after the conventional pound-force per
square inch (psi) value. The Energy Institute uses the bar as a pressure measurement. Conversion of units may be obtained as follows:
To convert from pound-force per square inch (psi) to pascal (Pa) multiply by 6.894757 × 10 .
To convert from pound-force per square inch (psi) to bar multiply by 0.06894757.
To convert from bar to pascal (Pa) multiply by 10 .
4. Significance and Use
4.1 This test method measures the net change in pressure resulting from consumption of oxygen by oxidation and gain in pressure
due to formation of volatile oxidation by-products. This test method may be used for quality control to indicate batch-to-batch
uniformity. It predicts neither the stability of greases under dynamic service conditions, nor the stability of greases stored in
containers for long periods, nor the stability of films of greases on bearings and motor-parts. It should not be used to estimate the
relative oxidation resistance of different grease types.
5. Apparatus
5.1 Oxidation Pressure Vessel, Sample Dish, Dish Holder, Pressure Gauge and Oil Bath as described in detail in the Annex.
NOTE 3—Other constant-temperature baths may be used if they are equivalent in heat capacity and thermal gradient characteristics to the oil bath described
in the Annex and can be shown to maintain the pressure vessel at the prescribed test temperature. The Quantum® dry bath apparatus has been determined
to be a suitable alternative. Refer to the instrument manufacturer’s manual for operating procedures.
5.2 Thermometer, having a range as shown below and conforming to the requirements as prescribed in Specification E1 or in the
Specifications for IP Standard Thermometers. Alternatively, digital contact thermometers such as PRTs (platinum resistance
thermometers), thermistors, or thermocouples in accordance with Specification E2877 of equal or better accuracy may be used:
Thermometer Number
Temperature Range ASTM IP
95 °C to 103 °C 22C 24C
204 °F to 218 °F 22F 24F
6. Material
6.1 Oxygen, of not less than 99.5 % purity.
6.2 (Warning—Since oxygen vigorously accelerates combustion, observe the following procedures: (1) Keep oil and grease
away from oxygen at high pressure. Keep oil and grease away from all regulators, gauges and control equipment. (2) Use oxygen
only with equipment conditioned for oxygen service by careful cleaning to remove oil and grease from area in contact with high
pressure oxygen. (3) Keep combustibles away from oxygen and eliminate ignition sources. (4) Keep surfaces clean to prevent
ignition or explosion, or both, upon contact with high pressure oxygen. (5) Always use a pressure regulator to deliver oxygen.
Release regulator tension before opening oxygen cylinder. (6) All equipment used must be suitable and recommended for oxygen
service. (7) Never attempt to transfer oxygen from cylinder in which it is received to any other cylinder prior to use. (8) Do not
drop oxygen cylinders. (9) Keep cylinder valve closed when not in use. (10) Stand away from valve when opening cylinder. (11)
Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR, U.K., http://www.energyinst.org.uk.
Available from British Standards Institute (BSI), 389 Chiswick High Rd., London W4 4AL, U.K., http://www.bsi-global.com.
D942 − 23a
Do not breathe or use technical grade oxygen for inhalation purposes. (12) See Compressed Gas Association Booklets G-4 and
G-4-1 for details of safe practice in the use of oxygen.)
6.3 n-Heptane—(Warning—Flammable. Harmful if inhaled. Keep away from heat, sparks, and open flame. Keep container
closed. Use with adequate ventilation. Avoid breathing vapor or spray mist. Avoid prolonged or repeated contact with skin.)
6.4 Cleaning Solution, capable of satisfactorily cleaning the glassware used in the test. The criterion for satisfactory cleaning shall
be a matching of the quality of that obtained with chromic acid cleaning solutions (fresh chromic acid, 6 h soaking period, rinsing
with distilled water and drying) or some other equivalently strong oxidizing non-chromium containing acid cleaning solutions on
used sample dishes. (Warning—Causes severe burns. A recognized carcinogen. Strong oxidizer; contact with organic material may
cause fire. Hygroscopic.) (Warning—Do not get in eyes, on skin, or on clothing. Avoid breathing vapor or mist. Keep container
closed. Use with adequate ventilation. Do not take internally.) For this comparison, visual appearance and mass loss on heating
the glassware under test conditions may be used. Detergent cleaning avoids the potential hazards and inconveniences related to
handling corrosive chromic acid solutions; this procedure remains the reference cleaning practice and as such may function as an
alternate to the preferred procedure, cleaning with detergent solutions.
7. Preparation of Apparatus
7.1 Clean the sample dishes from all contamination from previous runs and from dust settling from the air by washing them with
n-heptane and then with a cleaning solution. Follow the final cleaning operation by a thorough tap water rinse, a distilled water
rinse, and drying in an oven. Handle the clean dishes only with forceps. (Warning—Handle in well-ventilated area, preferably in
a hood. Keep away from heat, sparks, and open flame. Keep container closed when not in use.) (Warning—See 6.3, and avoid
skin contact, which may cause severe burns.)
7.2 If lacquer is found after a run, clean the inside of the oxidation pressure vessel and the metal supports for the pressure vessel
dishes by immersing in an appropriate solvent capable of removing the lacquer, such as gum solvent as specified in Test Method
D525, and scrubbing with a bristle brush followed by drying. Scrub further with water and a fine scouring powder until all the
lacquer deposits are removed. Follow the scouring operation by a thorough tap water rinse, a distilled water rinse, and drying in
an oven. Handle the clean metal supports only with forceps.
8. Procedure
8.1 Fill each of the five dishes with 4.00 g 6 0.01 g of grease. Distribute the samples in the dishes in a uniform layer with a smooth
level upper surface. Place the filled dishes on the five bottom shelves of the holder, leaving the top shelf to act as a cover to prevent
condensing volatile products from dropping into the grease samples. When assembling the pressure vessel, place a small ball of
glass wool in the bottom of the stem.
8.2 Place the dish holder in the pressure vessel
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