ASTM D6185-97(2008)
(Practice)Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases
Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases
SIGNIFICANCE AND USE
The compatibility of greases can be important for users of grease-lubricated equipment. It is well known that the mixing of two greases can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur. A mixture of incompatible greases most often softens, sometimes excessively. Occasionally, it can harden. In extreme cases, the thickener and liquid lubricant will completely separate. Bleeding can be so severe that the mixed grease will run out of an operating bearing. Excessive syneresis can occur, forming pools of liquid lubricant separated from the grease. Dropping points can be reduced to the extent that grease or separated oil runs out of bearings at elevated operating temperatures. Such events can lead to catastrophic lubrication failures.
Because of such occurrences, equipment manufacturers recommend completely cleaning the grease from equipment before installing a different grease. Service recommendations for grease-lubricated equipment frequently specify the caveat–do not mix greases under any circumstances. Despite this admonition, grease mixing will occur and, at times, cannot be avoided. In such instances, it would be useful to know whether the mixing of two greases could lead to inadequate lubrication with disastrous consequences. Equipment users most often do not have the resources to evaluate grease compatibility and must rely on their suppliers. Mixing of greases is a highly imprudent practice. Grease and equipment manufacturers alike recognize such practices will occur despite all warnings to the contrary. Thus, both users and suppliers have a need to know the compatibility characteristics of the greases in question.
There are two approaches to evaluating the compatibility of grease mixtures. One is to determine whether such mixtures meet the same specification requirements as the constituent components. This approach is not addressed by this practice. Instead, this practice takes a specifi...
SCOPE
1.1 This practice covers a protocol for evaluating the compatibility of one or three binary mixtures of lubricating greases by comparing their properties or performance relative to those of the neat greases comprising the mixture.
1.2 Three properties are evaluated in a primary testing protocol using standard test methods: (1) dropping point by Test Method D 566 (or Test Method D 2265); (2) shear stability by Test Methods D 217, 100 000–stroke worked penetration; and (3) storage stability at elevated-temperature by change in 60-stroke penetration (Test Method D 217). For compatible mixtures (those passing all primary testing), a secondary (nonmandatory) testing scheme is suggested when circumstances indicate the need for additional testing.
1.3 Sequential or concurrent testing is continued until the first failure. If any mixture fails any of the primary tests, the greases are incompatible. If all mixtures pass the three primary tests, the greases are considered compatible.
1.4 This practice applies only to lubricating greases having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those greases within a specified range of properties, greases outside that range cannot be tested for compatibility by that test method. An exception to this would be when the tested property of the neat, constituent greases is within the specified range, but the tested property of a mixture is outside the range because of incompatibility.
1.5 This practice does not purport to cover all test methods that could be employed.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and practices and det...
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Designation:D6185–97 (Reapproved 2008)
Standard Practice for
Evaluating Compatibility of Binary Mixtures of Lubricating
Greases
This standard is issued under the fixed designation D6185; 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 practices and determine the applicability of regulatory limita-
tions prior to use. For specific safety information, see 7.2.3.
1.1 This practice covers a protocol for evaluating the
compatibility of one or three binary mixtures of lubricating
2. Referenced Documents
greases by comparing their properties or performance relative
2.1 ASTM Standards:
to those of the neat greases comprising the mixture.
D217 Test Methods for Cone Penetration of Lubricating
1.2 Three properties are evaluated in a primary testing
Grease
protocol using standard test methods: (1) dropping point by
D566 Test Method for Dropping Point of Lubricating
Test Method D566 (or Test Method D2265); (2) shear stability
Grease
by Test Methods D217, 100 000–stroke worked penetration;
D972 Test Method for Evaporation Loss of Lubricating
and (3) storage stability at elevated-temperature by change in
Greases and Oils
60-stroke penetration (Test Method D217). For compatible
D1092 Test Method for Measuring Apparent Viscosity of
mixtures (those passing all primary testing), a secondary
Lubricating Greases
(nonmandatory) testing scheme is suggested when circum-
D1263 Test Method for Leakage Tendencies ofAutomotive
stances indicate the need for additional testing.
Wheel Bearing Greases
1.3 Sequential or concurrent testing is continued until the
D1264 Test Method for Determining the Water Washout
first failure. If any mixture fails any of the primary tests, the
Characteristics of Lubricating Greases
greases are incompatible. If all mixtures pass the three primary
D1403 Test Methods for Cone Penetration of Lubricating
tests, the greases are considered compatible.
Grease Using One-Quarter and One-Half Scale Cone
1.4 This practice applies only to lubricating greases having
Equipment
characteristics suitable for evaluation by the suggested test
D1478 Test Method for Low-Temperature Torque of Ball
methods. If the scope of a specific test method limits testing to
Bearing Grease
those greases within a specified range of properties, greases
D1742 Test Method for Oil Separation from Lubricating
outsidethatrangecannotbetestedforcompatibilitybythattest
Grease During Storage
method. An exception to this would be when the tested
D1743 Test Method for Determining Corrosion Preventive
property of the neat, constituent greases is within the specified
Properties of Lubricating Greases
range, but the tested property of a mixture is outside the range
D1831 TestMethodforRollStabilityofLubricatingGrease
because of incompatibility.
D2265 Test Method for Dropping Point of Lubricating
1.5 This practice does not purport to cover all test methods
Grease Over Wide Temperature Range
that could be employed.
D2266 Test Method for Wear Preventive Characteristics of
1.6 The values stated in SI units are to be regarded as
Lubricating Grease (Four-Ball Method)
standard. No other units of measurement are included in this
D2509 Test Method for Measurement of Load-Carrying
standard.
Capacity of Lubricating Grease (Timken Method)
1.7 This standard does not purport to address all the safety
D2595 Test Method for Evaporation Loss of Lubricating
concerns, if any, associated with its use. It is the responsibility
Greases Over Wide-Temperature Range
of the user of this standard to establish appropriate safety and
D2596 Test Method for Measurement of Extreme-Pressure
Properties of Lubricating Grease (Four-Ball Method)
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.G0.01
on Chemical and General Laboratory Tests. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2008. Published September 2008. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
´1
approved in 1997. Last previous edition approved in 2002 as D6185–97(2002) .
Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D6185-97R08.
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6185–97 (2008)
D3336 Test Method for Life of Lubricating Greases in Ball 3.1.5.1 Discussion—Syneresis is a form of bleeding caused
Bearings at Elevated Temperatures byphysicalorchemicalchangesofthethickness.Separationof
free oil or the formation of cracks that occur in lubricating
D3337 Test Method for Determining Life and Torque of
greases during storage in containers is most often due to
Lubricating Greases in Small Ball Bearings
syneresis.
D3527 Test Method for Life Performance of Automotive
3.1.6 thickener, n—in a lubricating grease, a substance
Wheel Bearing Grease
composed of finely divided particles dispersed in a liquid
D4049 Test Method for Determining the Resistance of
lubricant to form the product’s structure.
Lubricating Grease to Water Spray
3.1.6.1 Discussion—The thickener can be fibers (such as
D4170 Test Method for Fretting Wear Protection by Lubri-
various metallic soaps) or plates or spheres (such as certain
cating Greases
non-stop thickeners) which are insoluble or, at most, only very
D4175 Terminology Relating to Petroleum, Petroleum
slightly soluble in the liquid lubricant. The general require-
Products, and Lubricants
ments are that the solid particles be extremely small, uniformly
D4290 Test Method for Determining the Leakage Tenden-
dispersed, and capable of forming a relatively stable, gel-like
cies ofAutomotive Wheel Bearing Grease UnderAcceler-
structure with the liquid lubricant. D217
ated Conditions
3.2 Definitions of Terms Specific to This Standard:
D4425 Test Method for Oil Separation from Lubricating
3.2.1 compatibility, n— of lubricating greases, the charac-
Grease by Centrifuging (Koppers Method)
teristic of lubricating greases to be mixed together without
D4693 Test Method for Low-Temperature Torque of
significant degradation of properties or performance.
Grease-Lubricated Wheel Bearings
3.2.1.1 Discussion—When a mixture of two greases has
D4950 Classification and Specification forAutomotive Ser-
properties or performance significantly inferior to both of the
vice Greases
neat, constituent greases, then the two greases are incompat-
D5706 Test Method for Determining Extreme Pressure
ible.Ifthepropertiesareinferiortothoseofoneneatgreasebut
Properties of Lubricating Greases Using a High-
not inferior to those of the other, then such is not necessarily
Frequency, Linear-Oscillation (SRV) Test Machine
considered an indication of incompatibility. To be considered
D5707 Test Method for Measuring Friction and Wear Prop- significantly inferior, the property of the mixture would be
worse than the poorer of the two neat greases by an amount
erties of Lubricating Grease Using a High-Frequency,
Linear-Oscillation (SRV) Test Machine exceeding the repeatability of the test method used to evaluate
the property (see pass and fail). Incompatibility most often is
2.2 Federal Standard:
manifested by a degradation in physical properties rather than
Federal Test Method 3467.1 (Standard 791C), Storage Sta-
4 in chemical properties, although, occurrence of the latter is not
bility of Lubricating Grease
unknown.
3.2.2 borderline compatibility, n—of lubricating greases,
3. Terminology
the characteristic of lubricating greases to be mixed together
3.1 Definitions:
with only slight degradation of properties or performance.
3.1.1 bleed (bleeding), n—of lubricating greases, the sepa-
3.2.2.1 Discussion—Slight degradation means that the
ration of a liquid lubricant from a lubricating grease for any
propertiesorperformanceofthemixtureispoorerthanthoseof
cause.
the two neat greases but by an amount less than the repeatabil-
3.1.2 lubricant, n—any material interposed between two
ity of the test method used to evaluate the property. (See
surfaces that reduces the friction or wear between them.
borderline pass.)
D4175
3.2.3 primary compatibility tests, n—of lubricating greases,
3.1.3 lubricating grease, n—a semifluid to solid product of
those test methods employed first to evaluate compatibility.
a dispersion of a thickener in a liquid lubricant.
3.2.3.1 Discussion—The test methods considered the most
3.1.3.1 Discussion—Thedispersionofthethickenerformsa significant in the evaluation of grease compatibility, insofar as
two-phase system and immobilizes the liquid lubricant by theyprovidethemostinformationwiththeleastexpenditureof
surface tension and other physical forces. Other ingredients testing resources, include tests for dropping point, consistency
imparting special properties are often included. D217 (usually softening) after shearing conditions, and consistency
change after storage at elevated temperatures.
3.1.4 spatulate, v—tomixorblendbyspreadingandfolding
with a flat thin, usually metal, tool. 3.2.4 secondary compatibility tests, n—of lubricating
greases, those test methods used to evaluate compatibility
3.1.5 syneresis, n—of lubricating greases, the separation of
when the primary compatibility tests are insufficient or incon-
liquid lubricant from a lubricating grease due to shrinkage or
clusive.
rearrangement of the structure.
3.2.4.1 Discussion—Such tests are driven by the critical
features of a given application. For example, if the application
subjects the grease to water contamination, water washout or
Withdrawn. The last approved version of this historical standard is referenced
water spray-off tests and, perhaps, corrosion tests would be
on www.astm.org.
used for additional evaluation. Secondary compatibility tests
Available from Standardization Documents Order Desk, Bldg. 4, Section D,
700 Robbins Ave., Philadelphia, PA 19111–5094, Attn: NPODS. are suggested, but not required, by this practice.
D6185–97 (2008)
3.2.5 pass, n—in compatibility testing of grease mixtures, a avoided. In such instances, it would be useful to know whether
test result that is equal to or better than that of the poorer of the the mixing of two greases could lead to inadequate lubrication
two constituent greases. with disastrous consequences. Equipment users most often do
3.2.6 borderline pass, n— in compatibility testing of grease not have the resources to evaluate grease compatibility and
mixtures, a test result that is inferior to that of the poorer of the must rely on their suppliers. Mixing of greases is a highly
two constituent greases by an amount not exceeding the imprudent practice. Grease and equipment manufacturers alike
repeatability of the test method used for the evaluation. recognize such practices will occur despite all warnings to the
3.2.6.1 Discussion—Borderline pass, borderline fail, bor- contrary. Thus, both users and suppliers have a need to know
derline compatible, and borderline incompatible are synony- the compatibility characteristics of the greases in question.
mous terms. 5.2 There are two approaches to evaluating the compatibil-
3.2.7 fail, n—in compatibility testing of grease mixtures, a ity of grease mixtures. One is to determine whether such
test result that is inferior to that of the poorer of the two mixtures meet the same specification requirements as the
constituentgreasesbyanamountexceedingtherepeatabilityof constituent components.This approach is not addressed by this
the test method used for the evaluation. practice. Instead, this practice takes a specification-
3.2.8 50:50 mixture, n—a uniform blend of 50 mass % of independent approach; it describes the evaluation of compat-
each of two component greases. ibility on a relative basis using specific test methods.
3.2.9 10:90 mixture, n—a uniform blend of 10 mass % of 5.2.1 Three test methods are used because fewer are not
one grease with 90 mass % of a second grease. sufficiently definitive. For example, in one study, using
3.2.10 90:10 mixture, n—a uniform blend of 90 mass % of 100 000-stroke worked penetration for evaluation, 62 % of the
one grease with 10 mass % of a second grease. mixtures were judged to be compatible. In a high-temperature
storage stability study, covering a broader spectrum of grease
4. Summary of Practice 5
types, only one-third of the mixtures were compatible. These
4.1 Option 1—A 50:50 mixture of two greases to be
studies used different criteria to judge compatibility.
evaluated for compatibility is prepared by spatulating. This
5.2.2 Compatibility cannot be predicted with certainty from
mixture and the two neat, constituent greases are tested using
foreknowledge of grease composition. Generally, greases hav-
theprimarycompatibilitytests(droppingpoint,100 000-stroke
ing the same or similar thickener types will be compatible.
workedpenetration,andchangein60-strokepenetrationdueto
Uncommonly, even greases of the same type, although nor-
high-temperature storage). Depending on the performance of
mally compatible when mixed, can be incompatible because of
the mixture, relative to those of the constituent greases, 10:90
incompatible additive treatments. Thus, compatibility needs to
and 90:10 mixtures may need to be tested in addition. Alter-
be judged on a case-by-case basis.
natively, Option 2 can be used. Instead of testing mixtures in
5.3 Two constituent greases are blended in specific ratios.A
sequential order, 10:90 and 90:10 mixtures are tested at the
50:50mixturesimulatesaratiothatmightbeexperiencedwhen
same time the 50:50 mixture is evaluated. If all mixtures pass
one grease (Grease A) is installed in a bearing containing a
the primary compatibility tests, or if the application requires
previously installed, different grease (Grease B), and no
the evaluation of specific properties, secondary compatibility attemptismadetoflushoutGreaseBwithGreaseA.The10:90
tests can be employed for further evaluation. Such tests can be
and 90:10 ratios are intended to simulate ratios that might
run concurrently, if desired. occur when attempts are made to flush out Grease B with
Grease A.
5. Significance and Use
NOTE 1—Some companies evaluate 25:75 and 75:25 ratio mixtures
5.1 The compatibility of greases can be important for users
instead of 10:90 and 90:10 ratio mixtures. But, the latter two ratios, which
of grease-lubricated equipment. It is well known that the
are prescribed by this practice, are considered more representa
...
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