ASTM D4425-19

Standard Test Method for Oil Separation from Lubricating Grease by Centrifuging (Koppers Method)

SIGNIFICANCE AND USE
5.1 This test method is useful in evaluating the degree to which a grease would separate into fluid and solid components when subjected to high centrifugal forces. Flexible shaft couplings, universal joints, and rolling element thrust bearings are examples of machinery which subject lubricating greases to large and prolonged centrifugal forces. This test method has been found to give results that correlate well with results from actual service. The test method may be run at other conditions with agreement between parties but the precision noted in this test method will no longer apply.3
SCOPE
1.1 This test method covers a procedure for determining the tendency of lubricating grease to separate oil when subjected to high centrifugal forces.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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.  
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.

General Information

• Status: Published
• Publication Date: 31-May-2019
• ICS: 75.100 - Lubricants, industrial oils and related products
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.G0.03 - Physical Tests

Relations

• Replaces: ASTM D4425-09(2014) - Standard Test Method for Oil Separation from Lubricating Grease by Centrifuging (Koppers Method)
• Effective Date: 01-Jun-2019
• Refers: ASTM D217-19a - Standard Test Methods for Cone Penetration of Lubricating Grease
• Effective Date: 01-Jul-2019
• Refers: ASTM D217-19 - Standard Test Methods for Cone Penetration of Lubricating Grease
• Effective Date: 01-May-2019
• Refers: ASTM D217-16 - Standard Test Methods for Cone Penetration of Lubricating Grease
• Effective Date: 01-Oct-2016
• Refers: ASTM D217-10 - Standard Test Methods for Cone Penetration of Lubricating Grease
• Effective Date: 01-May-2010
• Refers: ASTM D217-02(2007) - Standard Test Methods for Cone Penetration of Lubricating Grease
• Effective Date: 01-Nov-2007
• Refers: ASTM D217-02 - Standard Test Methods for Cone Penetration of Lubricating Grease
• Effective Date: 10-Dec-2002
• Referred By: ASTM F2489-06(2022) - Standard Guide for Instrument and Precision Bearing Lubricants-Part 2 Greases
• Effective Date: 01-Jun-2019
• Referred By: ASTM D6185-11(2017) - Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases
• Effective Date: 01-Jun-2019

Overview

ASTM D4425-19 outlines the Standard Test Method for Oil Separation from Lubricating Grease by Centrifuging (Koppers Method). Developed by ASTM International, this test method is crucial for evaluating the tendency of lubricating grease to separate into oil and solid components when exposed to high centrifugal forces. This procedure is especially important for industries relying on machinery subjected to significant and prolonged centrifugal forces, such as flexible shaft couplings, universal joints, and rolling element thrust bearings. The results achieved using this method have demonstrated good correlation with actual service performance, making it a reliable approach for assessing the oil separation characteristics of lubricating greases.

Key Topics

• Purpose of the Test Method

  • Measures oil separation from lubricating greases under controlled centrifugal force
  • Provides an indicator for the grease stability in high-force environments

• Relevance to Equipment

  • Ensures grease suitability for applications where centrifugal forces are significant
  • Helps in selecting and quality-controlling greases for critical mechanical systems

• Test Parameters

  • Grease samples are subjected to a specified centrifugal force (G value)
  • Standard testing temperature is maintained at 50°C, with centrifugal acceleration at a G value of 36,000
  • Results reflect the resistance of the grease to oil separation, expressed as the K36 ratio

• Precision and Repeatability

  • Defined repeatability and reproducibility criteria ensure consistency of results when performed under standard conditions
  • Variations from prescribed procedures may impact precision

• Safety and Regulatory Considerations

  • Users are responsible for addressing safety, health, and environmental protocols during testing
  • Compliance with regulatory limitations is required

Applications

• Machinery Maintenance and Reliability

  • Selection and validation of lubricating greases for rotating and high-speed machinery
  • Prevents premature equipment failure by assessing grease stability under real-world operational stresses

• Quality Control in Lubricant Manufacturing

  • Batch testing during grease production to ensure consistent oil separation characteristics
  • Facilitates development of greases designed for high-performance or specialized applications

• Research and Development

  • Comparative evaluation of formulated greases for specific application requirements
  • Supports the optimization of grease formulations to reduce oil separation and improve service life

• Performance Benchmarking

  • Provides a standardized metric for comparing different lubricants, aiding both manufacturers and end-users in product selection

Related Standards

• ASTM D217 - Test Methods for Cone Penetration of Lubricating Grease, often referenced for defining grease consistency
• ASTM D6184 - Standard Test Method for Oil Separation from Lubricating Grease (Statically), which addresses oil separation under static conditions for comparative purposes
• ISO 6743-9 - International classification of lubricants and related products, assisting in harmonization with ASTM D4425-19 for global applications

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Keywords: ASTM D4425, oil separation, lubricating grease, centrifuging, Koppers Method, grease stability, centrifugal force, machinery lubrication, lubricant testing, mechanical equipment maintenance, grease quality control, high-speed rotation, industrial standards.

Standards Content (Sample)

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.
Designation: D4425 − 19
Standard Test Method for
Oil Separation from Lubricating Grease by Centrifuging
(Koppers Method)
This standard is issued under the fixed designation D4425; 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* 3.1.2 thickener, n—in lubricating grease, a substance com-
posed of finely-divided particles dispersed in a liquid to form
1.1 This test method covers a procedure for determining the
the products’s structure.
tendencyoflubricatinggreasetoseparateoilwhensubjectedto
high centrifugal forces. 3.1.2.1 Discussion—Thickeners can be fibers (such as vari-
ous metallic soaps) or plates or spheres (such as certain
1.2 The values stated in SI units are to be regarded as
non-soapthickeners),whichareinsolubleor,atmost,onlyvery
standard. No other units of measurement are included in this
slightly soluble in the liquid lubricant. The general require-
standard.
ments are that the solid particles be extremely small, uniformly
1.3 This standard does not purport to address all of the
dispersed, and capable of forming a relatively stable, gel-like
safety concerns, if any, associated with its use. It is the
structure with the liquid lubricant.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.2 Symbols:
mine the applicability of regulatory limitations prior to use.
a = distance from top of grease surface to tube mouth
1.4 This international standard was developed in accor-
(mm).
dance with internationally recognized principles on standard-
b = height of liquid column in an inverted test tube (mm).
ization established in the Decision on Principles for the
d = test tube inside diameter (mm).
Development of International Standards, Guides and Recom-
H = accumulated test time at a given reading (h).
mendations issued by the World Trade Organization Technical
K36 = resistance to centrifugal separation (V/H).
Barriers to Trade (TBT) Committee.
r = measured at the maximum radius of rotation (mm).
rpm = rotational speed (r/min).
2. Referenced Documents
V = volume of separated oil, as a percentage of the
2.1 ASTM Standards:
original grease volume (%).
D217 Test Methods for Cone Penetration of Lubricating
V = grease volume in a test tube (cm ).
g
Grease
V = volume of separated oil (cm ).
o
V = test tube total volume (cm ).
t
3. Terminology
A = angle of rotor, between the test tube axis and axis of
rotation (degrees).
3.1 Definitions:
ω = rotational speed (rad/s).
3.1.1 lubricating grease, n—a semi-fluid to solid product of
G = relative centrifugal acceleration.
a dispersion of a thickener in a liquid lubricant.
3.1.1.1 Discussion—The dispersion of the thickener forms a
3.3 The relative effect of centrifugal forces, when related to
two-phase system and immobilizes the liquid lubricant by
the gravitational standard acceleration (9.81 m⁄s ), is noted
surface tension and other physical forces. Other ingredients are
with the symbol G. It can be calculated as follows:
commonly included to impart special properties. D217
24 2
G 5 1.02 310 3r 3ω (1)
or
This test method is under the jurisdiction of Committee D02 on Petroleum
26 2
G 5 1.12 310 3r 3rpm¯ (2)
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.G0.03 on Physical Tests.
CurrenteditionapprovedJune1,2019.PublishedJuly2019.Originallyapproved 4. Summary of Test Method
in 1984. Last previous edition approved in 2014 as D4425 – 09 (2014). DOI:
10.1520/D4425-19. 4.1 Pairs of centrifuge tubes are charged with grease
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
samples and are placed in the centrifuge. The grease samples
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
are subjected to a centrifugal force equivalent to a G value of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 36 000, at 50 °C 6 1 °C, for specific periods of time. The
*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
D4425 − 19
resistance of the grease to separate the oil is then defined as a 8.2 Examine the required number of tubes to be used for the
ratioofthepercentofoilseparatedtothetotalnumberofhours test, rejecting any with surface scratches or imperfections.
of testing.
9. Procedure
5. Significance and Use
9.1 For each grease, two centrifuge tubes are required. New
tubes must be used for each test and they must be handled with
5.1 This test method is useful in evaluating the degree to
care to avoid scratches.
which a grease would separate into fluid and solid components
9.1.1 Determinethetotalvolume, V,incubiccentimetres,of
when subjected to high centrifugal forces. Flexible shaft
each tube by filling with water and then pouring into a
couplings, universal joints, and rolling element thrust bearings
graduated cylinder and measuring.
areexamplesofmachinerywhichsubjectlubricatinggreasesto
9.1.2 Measure the inside diameter, d, in millimetres with a
large and prolonged centrifugal forces. This test method has
vernier caliper.
been found to give results that correlate well with results from
actual service. The test method may be run at other conditions
9.2 Take grease samples from the container without includ-
with agreement between parties but the precision noted in this
ing any free oil found on the grease surface.
test method will no longer apply.
9.3 Charge each tube with approximately 0.5 g of grease for
each cubic centimeter of tube capacity (example: 7 g of grease
6. Apparatus
in a tube of 14 cm ) taking care that the difference in mass of
6.1 High-Speed Centrifuge,capableofdevelopinga Gvalue
each does not exceed 0.3 g to minimize centrifuge imbalance.
of 36 000. Mount the unit on a flat level surface to allow
9.4 Place the tubes in diametrically opposite compartments
unrestricted air flow to the motor. This is essential for long
if all rotor compartments are not used. Always use even
motor life. The centrifuge should be equipped with:
numbers of tubes.
6.1.1 Fixed Angle Rotor, multiple place, which can sustain a
9.5 The centrifuge lid must always be closed when the rotor
G value of 36 000.
is turning. The rotor should never be touched while rotating.
6.1.2 Thermometer, preferably of a dial type, installed so
that the temperature in the vicinity (5 mm to 15 mm) of the
9.6 Operate the centrifuge at a G value of 1000 for 3 min to
rotor can be measured.
eliminate any trapped air bubbles in the grease charge.
6.1.3 Air Choke, installed at the air inlet of the centrifuge
9.7 Measure the distance, a, in millimetres from the top of
chamber, and used to control the temperature if the unit lacks
the test tube to the closest point on the grease surface as shown
an automatic temperature control. Some designs require outlet
in Fig. 1, and calculate the grease volume as in 10.1.
choking as well.
9.8 Replace the tubes in the rotor head, close the lid, and
6.1.4 Centrifuge Tubes, made of transparent material, ca-
bring the speed up to a relative acceleration, G, of 36 000.
pable of withstanding a G value of 36 000 for 100 h minimum
Consult manufacturer’s instructions for proper speed.
(Note 1).
9.9 At the end of the test interval, the rotor must come to a
NOTE 1—Polypropylene tubes were found to be the most durable.
complete stop before opening the lid.
6.2 Balance, having a capacity of about 100 g with a
minimum sensitivity of 0.1 g. 9.10 Measure the amount of oil separated as follows:
9.10.1 Cover the mouth of the tube with a piece of hard
7. Sampling rubber or plastic material and invert for 1 min to 2 min or u
...

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: D4425 − 09 (Reapproved 2014) D4425 − 19
Standard Test Method for
Oil Separation from Lubricating Grease by Centrifuging
(Koppers Method)
This standard is issued under the fixed designation D4425; 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 procedure for determining the tendency of lubricating grease to separate oil when subjected to
high centrifugal forces.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
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:
D217 Test Methods for Cone Penetration of Lubricating Grease
3. Terminology
3.1 Definitions:
3.1.1 lubricating grease, n—a semi-fluid to solid product of a dispersion of a thickener in a liquid lubricant.
3.1.1.1 Discussion—
The dispersion of the thickener forms a two-phase system and immobilizes the liquid lubricant by surface tension and other
physical forces. Other ingredients are commonly included to impart special properties. D217
3.1.2 thickener, n—in lubricating grease, a substance composed of finely-divided particles dispersed in a liquid to form the
products’s structure.
3.1.2.1 Discussion—
Thickeners can be fibers (such as various metallic soaps) or plates or spheres (such as certain non-soap thickeners), which are
insoluble or, at most, only very slightly soluble in the liquid lubricant. The general requirements are that the solid particles be
extremely small, uniformly dispersed, and capable of forming a relatively stable, gel-like structure with the liquid lubricant.
3.2 Symbols:
a = distance from top of grease surface to tube mouth (mm).
b = height of liquid column in an inverted test tube (mm).
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.G0.03 on Physical Tests.
Current edition approved Oct. 1, 2014June 1, 2019. Published November 2014July 2019. Originally approved in 1984. Last previous edition approved in 20092014 as
D4425 – 09.D4425 – 09 (2014). DOI: 10.1520/D4425-09R14.10.1520/D4425-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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
D4425 − 19
d = test tube inside diameter (mm).
H = accumulated test time at a given reading (h).
K36 = resistance to centrifugal separation (V/H).
r = measured at the maximum radius of rotation (mm).
rpm = rotational speed (r/min).
V = volume of separated oil, as a percentage of the original grease volume (%).
V = grease volume in a test tube (cm ).
g
V = volume of separated oil (cm ).
o
V = test tube total volume (cm ).
t
A = angle of rotor, between the test tube axis and axis of rotation (degrees).
ω = rotational speed (rad/s).
G = relative centrifugal acceleration.
3.3 The relative effect of centrifugal forces, when related to the gravitational standard acceleration (9.81 (9.81 m m/s⁄s ), is
noted with the symbol G. It can be calculated as follows:
24 2
G 5 1.02 310 3r 3ω (1)
or
26 2
G 5 1.12 310 3r 3rpm¯ (2)
4. Summary of Test Method
4.1 Pairs of centrifuge tubes are charged with grease samples and are placed in the centrifuge. The grease samples are subjected
to a centrifugal force equivalent to a G value of 36 000,36 000, at 50°C50 °C 6 1°C,1 °C, for specific periods of time. The
resistance of the grease to separate the oil is then defined as a ratio of the percent of oil separated to the total number of hours of
testing.
5. Significance and Use
5.1 This test method is useful in evaluating the degree to which a grease would separate into fluid and solid components when
subjected to high centrifugal forces. Flexible shaft couplings, universal joints, and rolling element thrust bearings are examples of
machinery which subject lubricating greases to large and prolonged centrifugal forces. This test method has been found to give
results that correlate well with results from actual service. The test method may be run at other conditions with agreement between
parties but the precision noted in this test method will no longer apply.
6. Apparatus
6.1 High-Speed Centrifuge, capable of developing a G value of 36 000.36 000. Mount the unit on a flat level surface to allow
unrestricted air flow to the motor. This is essential for long motor life. The centrifuge should be equipped with:
6.1.1 Fixed Angle Rotor, multiple place, which can sustain a G value of 36 000.36 000.
6.1.2 Thermometer, preferably of a dial type, installed so that the temperature in the vicinity (5(5 mm to 15 mm) 15 mm) of the
rotor can be measured.
6.1.3 Air Choke, installed at the air inlet of the centrifuge chamber, and used to control the temperature if the unit lacks an
automatic temperature control. Some designs require outlet choking as well.
6.1.4 Centrifuge Tubes, made of transparent material, capable of withstanding a G value of 36 00036 000 for 100 h 100 h
minimum (Note 1).
NOTE 1—Polypropylene tubes were found to be the most durable.
6.2 Balance, having a capacity of about 100 g 100 g with a minimum sensitivity of 0.1 g. 0.1 g.
7. Sampling
7.1 The sample presented for analysis should be large enough to make possible the selection of a representative portion for
testing. Each run will require approximately 0.5 g 0.5 g for each cubic centimetre of tube capacity . Examine for any indication
of non-homogeneity such as oil separation, phase changes, or gross contamination. If any abnormal conditions are found, obtain
a new sample.
7.2 The sample temperature at time of loading is to be between 15°C15 °C and 35°C.35 °C.
8. Preparation of Apparatus
8.1 Inspect the centrifuge unit paying particular attention to the cleanliness of the rotor which will be unbalanced by any surface
deposits.
Detailed discussion is found in Calistrat, M. M., Grease Separation under Centrifugal Forces, ASME Paper 75-PTG-3. Presented at the Joint ASLE-ASME Lubrication
Conference, Oct. 21–23, 1975.
D4425 − 19
8.2 Examine the required number of tubes to be used for the test, rejecting any with surface scratches or imperfections.
9. Procedure
9.1 For each grease, two centrifuge tubes are required. New tubes must be used for each test and they must be handled with
care to avoid scratches.
9.1.1 Determine the total volume, V, in cubic centimetres, of each tube by filling with water and then pouring into a graduated
cylinder and measuring.
9.1.2 Measure the inside diameter, d, in millimetres with a vernier caliper.
9.2 Take grease samples from the container without including any free oil found on the grease surface.
9.3 Charge each tube with approximately 0.5 g 0.5 g of grease for each cubic centimeter of tube capacity (example: 7 g 7 g of
grease in a tube of 14 cm14 cm ) taking care that the difference in mass of each does not exceed 0.3 g 0.3 g to minimize centrifuge
imbalance.
9.4 Place the tubes in diametrically opposite compartments if all rotor compartments are not used. Always use even numbers
of tubes.
9.5 The centrifuge lid must always be closed when the rotor is t
...