ASTM D4425-09(2014)
(Test Method)Standard Test Method for Oil Separation from Lubricating Grease by Centrifuging (Koppers Method)
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D4425 − 09 (Reapproved 2014)
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 slightly soluble in the liquid lubricant. The general require-
ments are that the solid particles be extremely small, uniformly
1.1 This test method covers a procedure for determining the
dispersed, and capable of forming a relatively stable, gel-like
tendencyoflubricatinggreasetoseparateoilwhensubjectedto
structure with the liquid lubricant.
high centrifugal forces.
3.2 Symbols:
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
a = distance from top of grease surface to tube mouth
standard.
(mm).
1.3 This standard does not purport to address all of the
b = height of liquid column in an inverted test tube (mm).
d = test tube inside diameter (mm).
safety concerns, if any, associated with its use. It is the
H = accumulated test time at a given reading (h).
responsibility of the user of this standard to establish appro-
K36 = resistance to centrifugal separation (V/H).
priate safety and health practices and determine the applica-
r = measured at the maximum radius of rotation (mm).
bility of regulatory limitations prior to use.
rpm = rotational speed (r/min).
V = volume of separated oil, as a percentage of the
2. Referenced Documents
original grease volume (%).
2.1 ASTM Standards:
V = grease volume in a test tube (cm ).
g
D217 Test Methods for Cone Penetration of Lubricating
V = volume of separated oil (cm ).
o
Grease
V = test tube total volume (cm ).
t
A = angle of rotor, between the test tube axis and axis of
3. Terminology
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 thickener in a liquid lubricant.
3.3 The relative effect of centrifugal forces, when related to
3.1.1.1 Discussion—The dispersion of the thickener forms a
the gravitational standard acceleration (9.81 m/s ), is noted
two-phase system and immobilizes the liquid lubricant by
with the symbol G. It can be calculated as follows:
surface tension and other physical forces. Other ingredients are
24 2
G 5 1.02 310 3r 3ω (1)
commonly included to impart special properties. D217
or
3.1.2 thickener, n—in lubricating grease, a substance com-
26 2
G 5 1.12 310 3r 3rpm¯ (2)
posed of finely-divided particles dispersed in a liquid to form
the products’s structure.
4. Summary of Test Method
3.1.2.1 Discussion—Thickeners can be fibers (such as vari-
4.1 Pairs of centrifuge tubes are charged with grease
ous metallic soaps) or plates or spheres (such as certain
samples and are placed in the centrifuge. The grease samples
non-soapthickeners),whichareinsolubleor,atmost,onlyvery
are subjected to a centrifugal force equivalent to a G value of
36 000, at 50°C 6 1°C, for specific periods of time. The
This test method is under the jurisdiction of Committee D02 on Petroleum
resistance of the grease to separate the oil is then defined as a
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
ratioofthepercentofoilseparatedtothetotalnumberofhours
mittee D02.G0.03 on Physical Tests.
of testing.
Current edition approved Oct. 1, 2014. Published November 2014. Originally
approved in 1984. Last previous edition approved in 2009 as D4425 – 09. DOI:
5. Significance and Use
10.1520/D4425-09R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.1 This test method is useful in evaluating the degree to
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
which a grease would separate into fluid and solid components
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. when subjected to high centrifugal forces. Flexible shaft
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4425 − 09 (2014)
couplings, universal joints, and rolling element thrust bearings 9.1.1 Determinethetotalvolume, V,incubiccentimetres,of
areexamplesofmachinerywhichsubjectlubricatinggreasesto each tube by filling with water and then pouring into a
large and prolonged centrifugal forces. This test method has graduated cylinder and measuring.
been found to give results that correlate well with results from 9.1.2 Measure the inside diameter, d, in millimetres with a
actual service. The test method may be run at other conditions vernier caliper.
with agreement between parties but the precision noted in this
9.2 Take grease samples from the container without includ-
test method will no longer apply.
ing any free oil found on the grease surface.
9.3 Charge each tube with approximately 0.5 g of grease for
6. Apparatus
each cubic centimeter of tube capacity (example:7gof grease
6.1 High-Speed Centrifuge,capableofdevelopinga Gvalue
in a tube of 14 cm ) taking care that the difference in mass of
of 36 000. Mount the unit on a flat level surface to allow
each does not exceed 0.3 g to minimize centrifuge imbalance.
unrestricted air flow to the motor. This is essential for long
9.4 Place the tubes in diametrically opposite compartments
motor life. The centrifuge should be equipped with:
if all rotor compartments are not used. Always use even
6.1.1 Fixed Angle Rotor, multiple place, which can sustain a
numbers of tubes.
G value of 36 000.
6.1.2 Thermometer, preferably of a dial type, installed so 9.5 The centrifuge lid must always be closed when the rotor
that the temperature in the vicinity (5 to 15 mm) of the rotor is turning. The rotor should never be touched while rotating.
can be measured.
9.6 Operate the centrifuge at a G value of 1000 for 3 min to
6.1.3 Air Choke, installed at the air inlet of the centrifuge
eliminate any trapped air bubbles in the grease charge.
chamber, and used to control the temperature if the unit lacks
9.7 Measure the distance, a, in millimetres from the top of
an automatic temperature control. Some designs require outlet
the test tube to the closest point on the grease surface as shown
choking as well.
in Fig. 1, and calculate the grease volume as in 10.1.
6.1.4 Centrifuge Tubes, made of transparent material, ca-
pable of withstanding a G value of 36 000 for 100 h minimum 9.8 Replace the tubes in the rotor head, close the lid, and
(Note 1).
bring the speed up to a relative acceleration, G, of 36 000.
Consult manufacturer’s instructions for proper speed.
NOTE 1—Polypropylene tubes were found to be the most durable.
9.9 At the end of the test interval, the rotor must come to a
6.2 Balance, having a capacity of about 100 g with a
complete stop before opening the lid.
minimum sensitivity of 0.1 g.
9.10 Measure the amount of oil separated as follows:
7. Sampling 9.10.1 Cover the mouth of the tube with a piece of hard
rubber or plastic material and invert for 1 to 2 min or until all
7.1 The sample presented for analysis should be large
the oil flows to the top of the tube.
enough to make possible the selection of a representative
9.10.2 Measure the height, b, of the separated oil in
portion for testing. Each run will require approximately 0.5 g
millimetres, as shown in Fig. 2.
for each cubic centimetre of tube capacity . Examine for any
indication of non-homogeneity such as oil separation,
...
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 D4425 − 09 (Reapproved 2014)
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 and health practices and determine the applicability of regulatory
limitations prior to use.
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 thickener in a liquid lubricant.
This test method is under the jurisdiction of Committee D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.G0.03 on Physical Tests.
Current edition approved April 15, 2009Oct. 1, 2014. Published May 2009November 2014. Originally approved in 1984. Last previous edition approved in 20022009 as
D4425–97(2002).D4425 – 09. DOI: 10.1520/D4425-09.10.1520/D4425-09R14.
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.
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).
d = test tube inside diameter (mm).
H = accumulated test time at a given reading (h).
K36 = resistance to centrifugal separation (V/H).
*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 − 09 (2014)
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 m/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, at 50°C 6 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. 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.
6.1.2 Thermometer, preferably of a dial type, installed so that the temperature in the vicinity (5 to 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 36 000 for 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 with a minimum sensitivity of 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 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°C and 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.
8.2 Examine the required number of tubes to be used for the test, rejecting any with surface scratches or imperfections.
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 − 09 (2014)
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 of grease for each cubic centimeter of tube capacity (example: 7 g of grease in
a tube of 14 cm ) taking care that the difference in mass of each does not exceed 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 turning. The rotor should never be touched while rotat
...
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