ASTM D7110-14
(Test Method)Standard Test Method for Determining the Viscosity-Temperature Relationship of Used and Soot-Containing Engine Oils at Low Temperatures
Standard Test Method for Determining the Viscosity-Temperature Relationship of Used and Soot-Containing Engine Oils at Low Temperatures
SIGNIFICANCE AND USE
5.1 Significance of Low Temperature, Low Shear Rate, Engine Oil Rheology—The low-temperature, low-shear viscometric behavior of an engine oil, whether new, used, or sooted, determines whether the oil will flow to the sump inlet screen, then to the oil pump, then to the sites in the engine requiring lubrication in sufficient quantity to prevent engine damage immediately or ultimately after cold temperature starting. Two forms of flow problems have been identified,3 flow-limited and air-binding behavior. The first form of flow restriction, flow-limited behavior, is associated with the oil's viscosity; the second, air-binding behavior, is associated with gelation.
5.2 Significance of the Test Method—The temperature-scanning technique employed by this test method was designed to determine the susceptibility of the engine oil to flow-limited and air-binding response to slow cooling conditions by providing continuous information on the rheological condition of the oil over the temperature range of use.3,4,5 In this way, both viscometric and gelation response are obtained in one test.
Note 1: This test method is one of three related to pumpability related problems. Measurement of low-temperature viscosity by the two other pumpability test methods, D3829 and D4684, hold the sample in a quiescent state and generate the apparent viscosity of the sample at shear rates ranging up to 15 s-1 and shear stresses up to 525 Pa at a previously selected temperature. Such difference in test parameters (shear rate, shear stress, sample motion, temperature scanning, and so forth) can lead to differences in the measured apparent viscosity among these methods with some test oils, particularly when other rheological factors associated with gelation are present. In addition, the three methods differ considerably in cooling rates.
5.3 Gelation Index and Gelation Index Temperature—This test method has been further developed to yield parameters called the Gelation Index and Gelation Ind...
SCOPE
1.1 This test method covers how to measure the apparent viscosity of used and soot-containing engine oils at low temperatures.
1.2 A shear rate of approximately 0.2 s-1 is produced at shear stresses below 200 Pa. Apparent viscosity is measured continuously as the sample is cooled at a rate of 3°C per hour over the range of −5 °C to −40 °C.
1.3 The measurements resulting from this test method are viscosity, the maximum rate of viscosity increase (Gelation Index) and the temperature at which the Gelation Index occurs.
1.4 Applicability to petroleum products other than engine oils has not been determined in preparing this test method.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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: D7110 − 14
StandardTest Method for
Determining the Viscosity-Temperature Relationship of Used
and Soot-Containing Engine Oils at Low Temperatures
This standard is issued under the fixed designation D7110; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 3. Terminology
1.1 This test method covers how to measure the apparent 3.1 Definitions:
viscosity of used and soot-containing engine oils at low
3.1.1 apparent viscosity, n—theviscosityobtainedbyuseof
temperatures.
this test method.
-1
3.1.1.1 Discussion—See3.1.7fordefinitionofviscosityand
1.2 A shear rate of approximately 0.2 s is produced at
units.
shear stresses below 200 Pa. Apparent viscosity is measured
continuously as the sample is cooled at a rate of 3°C per hour
3.1.2 digital contact thermometer (DCT), n—an electronic
over the range of −5°C to −40°C.
device consisting of a digital display and associated tempera-
ture sensing probe.
1.3 The measurements resulting from this test method are
viscosity, the maximum rate of viscosity increase (Gelation
3.1.2.1 Discussion—This device consists of a temperature
Index)andthetemperatureatwhichtheGelationIndexoccurs.
sensor connected to a measuring instrument; this instrument
1.4 Applicability to petroleum products other than engine
measures the temperature-dependent quantity of the sensor,
oils has not been determined in preparing this test method.
computes the temperature from the measured quantity, and
providesadigitaloutput,ordisplayofthetemperature,orboth.
1.5 The values stated in SI units are to be regarded as
This device is sometimes referred to a digital thermometer.
standard. No other units of measurement are included in this
standard.
3.1.3 Newtonian oil, n—an oil that, at a given temperature,
exhibits a constant viscosity at all shear rates or shear stresses.
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.1.4 non-Newtonian oil, n—an oil that, at a given
responsibility of the user of this standard to establish appro-
temperature,exhibitsaviscositythatvarieswithshearstressor
priate safety and health practices and determine the applica-
shear rate.
bility of regulatory limitations prior to use.
3.1.5 shear rate, n—velocity gradient perpendicular to the
2. Referenced Documents direction of flow.
3.1.5.1 Discussion—The SI unit for shear rate is the recip-
2.1 ASTM Standards:
-1
rocal second (1/s; also s ).
D341Practice for Viscosity-Temperature Charts for Liquid
Petroleum Products
3.1.6 shear stress, n—force per unit area in the direction of
D3829Test Method for Predicting the Borderline Pumping
flow.
Temperature of Engine Oil
3.1.6.1 Discussion—TheSIunitforshearstressisthepascal
D4684Test Method for Determination of Yield Stress and
(Pa).
Apparent Viscosity of Engine Oils at Low Temperature
3.1.7 viscosity, n—thatpropertyofafluidwhichresistsflow.
D4057Practice for Manual Sampling of Petroleum and
3.1.7.1 Discussion—Viscosity is defined as the ratio of the
Petroleum Products
applied shear stress (force causing flow) and the shear rate
(resultant velocity of flow per unit distance from a stationary
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
surface wet by the fluid). Mathematically expressed:
Subcommittee D02.07 on Flow Properties.
viscosity 5 shearstress/shearrateor, symbolically, η 5 τ/γ˙ (1)
Current edition approved Dec. 1, 2014. Published January 2015. Originally
approved in 2005. Last previous edition approved in 2011 as D7110–05a (2011).
in which the symbols in the second portion of Eq 1 are
DOI: 10.1520/D7110-14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or defined by 3.1.5 and 3.1.6. The SI unit for viscosity used
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
herein is millipascal seconds (mPa·s).
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.2 Definitions of Terms Specific to This Standard:
*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
D7110 − 14
3.2.1 air-binding oils, n—those engine oils whose border- 3.2.10 Gelation Index reference oils, n—non-Newtonian
linepumpingtemperaturesaredeterminedbyacombinationof oils chosen to give certain levels of Gelation Index as a check
gelation and viscous flow. on instrument performance.
3.2.2 borderline pumping temperature, n—that temperature 3.2.11 Gelation Index Temperature, n—the temperature in
at which an engine oil may have such poor flow characteristics degrees Celsius at which the Gelation Index occurs.
that the engine oil pump may not be capable of supplying
3.2.12 pre-treatment sample heating bath, n—a water or air
sufficient lubricant to the engine.
bath to heat the samples for 1.5 h at 90°C 6 2°C before
3.2.3 calibration oil, n—Newtonianoilsdevelopedandused testing.
to calibrate the viscometer drive module over the viscosity
3.2.13 programmable liquid cold bath, n—a liquid bath
range required for this test method.
having a temperature controller capable of being programmed
3.2.3.1 Discussion—These calibration oils are specially
to run the calibration and the analysis portions of the test
blended to give sufficient sensitivity and range for the special
method.
viscometer head used.
3.2.14 temperature controller, n—a programmable device
3.2.4 computer-programmed automated analysis, n—use of
which, when properly programmed, ramps the temperature
techniques for acquiring analog data, converting these to
upward or downward at a chosen rate or series of steps while
digital values and using this information to automatically
simultaneously controlling temperature excursions.
record and analyze torque output from the viscometer drive
3.2.14.1 calibration program, n—a program to run the
module and to render this information into tabular data and
required series of temperatures at which the torque values
plotted relationships.
necessary to calibrate the viscometer drive module are col-
3.2.4.1 analog-to-digital (A-D) converter, n—a device for
lected and analyzed.
converting continuously produced electrical signals into dis-
3.2.14.2 test program, n—a program to run the test oil
crete numerical values capable of being analyzed by computer
analysis at 1°C/h temperature decrease.
technology.
3.2.14.3 hold program, n—a program to reach and hold the
3.2.5 critical pumpability temperature, n—the temperature
programmable liquid cold bath at −5°C.
at which an oil reaches a viscosity believed to be critical to
3.2.15 test cell, n—the combination of the rotor and stator.
limiting pumpability of the oil (see 3.2.6).
Critical elements of the test cell are sketched in Fig. 1.
3.2.6 critical pumpability viscosity, n—thatapparentviscos-
ity believed to cause pumpability problems in an engine.
3.2.7 flow-limited oils, n—those oils whose borderline
pumping temperatures are determined by viscous flow.
3.2.8 gelation, n—a rheological condition of an oil charac-
terized by a marked increase in flow resistance over and above
the normal exponential increase of viscosity with decreasing
temperature, particularly at lower shear stresses and tempera-
tures.
3.2.8.1 Discussion—Gelation has been attributed to a pro-
cessofnucleationandcrystallizationofoilcomponentsandthe
consequent formation of a gel-like mass.
3.2.9 Gelation Index, n—the maximum value of the incre-
mental ratio:
2@ log log η 2 log log η #/ log T 2 log T (2)
~ ! ~ ! ~ !
1 2 1 2
in which η is dynamic viscosity and T is temperature in
Kelvin over the temperature range scanned when the incre-
mental decrease in temperature is 1°K.
3.2.9.1 Discussion—The technique of deriving Gelation In-
dex was first developed and practiced by collecting informa-
tion from a strip-chart recording and applying the empirical
MacCoull-Walther-Wright equation. For further information,
see Appendix1 of Viscosity-Temperature Charts D341.
Symposium on Low Temperature Lubricant Rheology Measurement and Rel-
evance to Engine Operation,ASTMSTP1143,Ed.RobertB.Rhodes,ASTM,1992.
Selby, T. W., “The Use of the Scanning Brookfield Technique to Study the
Critical Degree of Gelation of Lubricants at Low Temperatures,” SAE Paper
910746, Society of Automotive Engineers, 1991. FIG. 1 Test Cell
D7110 − 14
3.2.15.1 rotor, n—a titanium rotor sized to give a compro- andair-bindingresponsetoslowcoolingconditionsbyprovid-
mise of sensitivity and range to the determination of viscosity ing continuous information on the rheological condition of the
3,4,5
and gelation using this test method. oil over the temperature range of use. In this way, both
viscometric and gelation response are obtained in one test.
3.2.15.2 stator, n—a precision-bore borosilicate glass tube,
NOTE1—Thistestmethodisoneofthreerelatedtopumpabilityrelated
to which a measured amount of oil is added for the test and
problems. Measurement of low-temperature viscosity by the two other
within which the specially-made rotor turns.
pumpability test methods, D3829 and D4684, hold the sample in a
3.2.15.2.1 stator collar, n—aclampforthestatorwhichalso
quiescent state and generate the apparent viscosity of the sample at shear
-1
rates ranging up to 15 s and shear stresses up to 525Pa at a previously
positions it on the test cell alignment device.
selected temperature. Such difference in test parameters (shear rate, shear
3.2.15.3 test cell alignment device, n—a special device used
stress, sample motion, temperature scanning, and so forth) can lead to
to support the viscometer drive module while maintaining the
differences in the measured apparent viscosity among these methods with
stator and the rotor coaxial and vertical in regard to the some test oils, particularly when other rheological factors associated with
gelation are present. In addition, the three methods differ considerably in
viscometerdriveshaft.Laterdesignsadmitdrygasintothecell
cooling rates.
to prevent moisture and frost buildup.
5.3 Gelation Index and Gelation Index Temperature—This
3.2.16 test oil, n—any oil for which apparent viscosity is to
test method has been further developed to yield parameters
be determined using the procedure described by this test
calledtheGelationIndexandGelationIndexTemperature.The
method.
first parameter is a measure of the maximum rate of torque
3.2.17 viscometer drive module, n—the rotor drive and
increasecausedbytherheologicalresponseoftheoilastheoil
torque-sensing component of a rotational viscometer.
is cooled slowly. The second parameter is the temperature at
3.2.18 viscometer module support, n—a part of the test cell
which the Gelation Index occurs.
alignment device supporting the viscometer drive module.
6. Apparatus
4. Summary of Test Method
6.1 Test Cell—Shown in Fig. 1, consisting of a matched
4.1 Usedandsootedengineoilsareanalyzedusingaspecial
rotor and a stator of the following critical dimensions:
rotational viscometer with analog or digital output to a com-
6.1.1 Rotor Dimensions—Critical length is 65.5mm 6
puter program.Aspecially made glass stator/metal rotor cell is
0.1mm and critical diameter is 18.40mm 6 0.02mm.
attached to the viscometer and subjected to a programmed
6.1.2 Stator Dimensions—Critical diameter is 22.05mm
temperature change for both calibration and sample analysis.
(60.02mm) at whatever length will satisfy the immersion
Following calibration of the rotor-stator set, an approximately
depth when the upper oil level is a minimum of 15mm below
20mL test sample of a test lubricating oil is poured into the
the cooling liquid level over the entire temperature range.
stator and preheated for 1.5h to 2.0h at 90°C in an oven or
6.2 Viscometer Drive Modules—Rotational viscometer
water bath. Shortly after completing the preheating step, the
drive modules capable of producing an analog signal to an
room-temperature rotor is put into the stator containing the
analog-to-digital converter or other analog signal data proces-
heated oil and coupled to a torque-sensing viscometer head
sor such as a strip-chart recorder.
using an adapter to automatically center the rotor in the stator
6.2.1 With the rotor and stator described in 6.1.1 and 6.1.2,
during test. A programmable low-temperature bath is used to
the viscometer drive module must be capable of measuring to
cool the cell at a specified rate of 3°C⁄h from −5°C to the
at least 90000mPa·s (cP).
temperature at which the maximum torque recordable is
6.3 Test Cell Alignment Device—Simultaneously maintains
exceeded when using a speed of 0.3r⁄min for the rotor. After
averticalaxialalignmentandreasonablyconsistentpositioning
the desired information has been collected, the computer
of the rotor in the stator to give repeatable torque readout from
program generates the desired viscometric and rheological
test to test when setting up the apparatus for analysis.
values from the recorded data.
6.3.1 Viscometer Support—Supports the viscometer drive
5. Significance and Use
module and aligns it vertically.
6.3.2 Stator Collar—Clampsthestatorandsupportsitwhen
5.1 Significance of Low Temperature, Low Shear Rate,
the stator collar is attached to the viscometer support.
Engine Oil Rheology—The low-temperature, low-shear visco-
metricbehaviorofanengineoil,whethernew,used,orsooted,
6.4 Ameansofprovidingadrygasatmosphereoverthetop
determines whether the oil will flow to the sump inlet screen,
of the test sample is necessary to prevent condensation and
then to the oil pump, then to the sites in the engine requiring
freezing of water on the oil surface.
lubrication in sufficient quantity to prevent engine damage
6.5 Programmable Liquid Cooling Bath—Liquid bath ca-
immediately or ultimately after cold temperature starting. Two
pable of running either the calibration or the testing program
formsofflowproblemshavebeenidentified, flow-limitedand
with temperature control of 60.1°C over the temperature
air-binding behavior. The first form of flow restriction, flow-
range desired at 1°C⁄h.
limited behavior, is associated with the oil’s viscosity; the
second, air-binding behavior, is associated with gelation.
Shaub,H.,“AHistoryofASTMAccomplishmentsinLowTemperatureEngine
5.2 Significance of the Test Method—The temperature-
Oil Rheology,” Symposium on Low Temperature Lubricant Rheology Measurement
scanningtechniqueemployedbythis
...
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: D7110 − 05a (Reapproved 2011) D7110 − 14
Standard Test Method for
Determining the Viscosity-Temperature Relationship of Used
and Soot-Containing Engine Oils at Low Temperatures
This standard is issued under the fixed designation D7110; 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 how to measure the apparent viscosity of used and soot-containing engine oils at low temperatures.
-1
1.2 A shear rate of approximately 0.2 s is produced at shear stresses below 200 Pa. Apparent viscosity is measured
continuously as the sample is cooled at a rate of 3°C per hour over the range of −5−5 °C to −40°C.−40 °C.
1.3 The measurements resulting from this test method are viscosity, the maximum rate of viscosity increase (Gelation Index)
and the temperature at which the Gelation Index occurs.
1.4 Applicability to petroleum products other than engine oils has not been determined in preparing this test method.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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:
D341 Practice for Viscosity-Temperature Charts for Liquid Petroleum Products
D3829 Test Method for Predicting the Borderline Pumping Temperature of Engine Oil
D4684 Test Method for Determination of Yield Stress and Apparent Viscosity of Engine Oils at Low Temperature
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
3. Terminology
3.1 Definitions:
3.1.1 apparent viscosity, n—the viscosity obtained by use of this test method.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.07 on Flow Properties.
Current edition approved Jan. 1, 2011Dec. 1, 2014. Published February 2011 January 2015. Originally approved in 2005. Last previous edition approved in 20052011 as
D7110D7110 – 05a (2011).–05a. DOI: 10.1520/D7110-05AR11.10.1520/D7110-14.
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—
See 3.1.63.1.7 for definition of viscosity and units.
3.1.2 digital contact thermometer (DCT), n—an electronic device consisting of a digital display and associated temperature
sensing probe.
3.1.2.1 Discussion—
This device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperature-
dependent quantity of the sensor, computes the temperature from the measured quantity, and provides a digital output, or display
of the temperature, or both. This device is sometimes referred to a digital thermometer.
*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
D7110 − 14
3.1.3 Newtonian oil, n—an oil that, at a given temperature, exhibits a constant viscosity at all shear rates or shear stresses.
3.1.4 non-Newtonian oil, n—an oil that, at a given temperature, exhibits a viscosity that varies with shear stress or shear rate.
3.1.5 shear rate, n—velocity gradient perpendicular to the direction of flow.
3.1.5.1 Discussion—
-1
The SI unit for shear rate is the reciprocal second (1/s; also s ).
3.1.6 shear stress, n—force per unit area in the direction of flow.
3.1.6.1 Discussion—
The SI unit for shear stress is the pascal (Pa).
3.1.7 viscosity, n—that property of a fluid which resists flow.
3.1.7.1 Discussion—
Viscosity is defined as the ratio of the applied shear stress (force causing flow) and the shear rate (resultant velocity of flow per
unit distance from a stationary surface wet by the fluid). Mathematically expressed:
viscosity 5 shear stress/shear rate or, symbolically, η5 τ/G (1)
viscosity5shear stress/shear rate or,symbolically,η5τ/γ˙ (1)
in which the symbols in the second portion of Eq 1 are defined by 3.1.43.1.5 and 3.1.53.1.6. The SI unit for viscosity used
herein is millipascal seconds (mPa·s).
3.2 Definitions of Terms Specific to This Standard:
3.2.1 air-binding oils, n—those engine oils whose borderline pumping temperatures are determined by a combination of gelation
and viscous flow.
3.2.2 borderline pumping temperature, n—that temperature at which an engine oil may have such poor flow characteristics that
the engine oil pump may not be capable of supplying sufficient lubricant to the engine.
3.2.3 calibration oil, n—Newtonian oils developed and used to calibrate the viscometer drive module over the viscosity range
required for this test method.
3.2.3.1 Discussion—
These calibration oils are specially blended to give sufficient sensitivity and range for the special viscometer head used.
3.2.4 computer-programmed automated analysis, n—use of techniques for acquiring analog data, converting these to digital
values and using this information to automatically record and analyze torque output from the viscometer drive module and to
render this information into tabular data and plotted relationships.
3.2.4.1 analog-to-digital (A-D) converter, n—a device for converting continuously produced electrical signals into discrete
numerical values capable of being analyzed by computer technology.
3.2.5 critical pumpability temperature, n—the temperature at which an oil reaches a viscosity believed to be critical to limiting
pumpability of the oil (see 3.2.6).
3.2.6 critical pumpability viscosity, n—that apparent viscosity believed to cause pumpability problems in an engine.
3.2.7 flow-limited oils, n—those oils whose borderline pumping temperatures are determined by viscous flow.
3.2.8 gelation, n—a rheological condition of an oil characterized by a marked increase in flow resistance over and above the
normal exponential increase of viscosity with decreasing temperature, particularly at lower shear stresses and temperatures.
3.2.8.1 Discussion—
Gelation has been attributed to a process of nucleation and crystallization of oil components and the consequent formation of a
gel-like mass.
3.2.9 Gelation Index, n—the maximum value of the incremental ratio:
Symposium on Low Temperature Lubricant Rheology Measurement and Relevance to Engine Operation, ASTM STP 1143, Ed. Robert B. Rhodes, ASTM, 1992.
D7110 − 14
2 log log η 2 log log η / log T 2 log T (2)
@~ ! ~ ! ~ !#
1 2 1 2
2@ log log η ! 2 ~log log η !#/~log T 2 log T ! (2)
~
1 2 1 2
in which η is dynamic viscosity and T is temperature in Kelvin over the temperature range scanned when the incremental
decrease in temperature is 1°K.1 °K.
3.2.9.1 Discussion—
The technique of deriving Gelation Index was first developed and practiced by collecting information from a strip-chart recording
and applying the empirical MacCoull-Walther-Wright equation. For further information, see Appendix 1 of Viscosity-Temperature
Charts D341.
3.2.10 Gelation Index reference oils, n—non-Newtonian oils chosen to give certain levels of Gelation Index as a check on
instrument performance.
3.2.11 Gelation Index Temperature, n—the temperature in degrees Celsius at which the Gelation Index occurs.
3.2.12 pre-treatment sample heating bath, n—a water or air bath to heat the samples for 1.5 h at 9090 °C 6 2°C2 °C before
testing.
3.2.13 programmable liquid cold bath, n—a liquid bath having a temperature controller capable of being programmed to run
the calibration and the analysis portions of the test method.
3.2.14 temperature controller, n—a programmable device which, when properly programmed, ramps the temperature upward
or downward at a chosen rate or series of steps while simultaneously controlling temperature excursions.
3.2.14.1 calibration program, n—a program to run the required series of temperatures at which the torque values necessary to
calibrate the viscometer drive module are collected and analyzed.
3.2.14.2 test program, n—a program to run the test oil analysis at 1°C/h temperature decrease.
3.2.14.3 hold program, n—a program to reach and hold the programmable liquid cold bath at −5°C.−5 °C.
3.2.15 test cell, n—the combination of the rotor and stator. Critical elements of the test cell are sketched in Fig. 1.
3.2.15.1 rotor, n—a titanium rotor sized to give a compromise of sensitivity and range to the determination of viscosity and
gelation using this test method.
3.2.15.2 stator, n—a precision-bore borosilicate glass tube, to which a measured amount of oil is added for the test and within
which the specially-made rotor turns.
3.2.15.2.1 stator collar, n—a clamp for the stator which also positions it on the test cell alignment device.
3.2.15.3 test cell alignment device, n—a special device used to support the viscometer drive module while maintaining the stator
and the rotor coaxial and vertical in regard to the viscometer driveshaft. Later designs admit dry gas into the cell to prevent
moisture and frost buildup.
3.2.16 test oil, n—any oil for which apparent viscosity is to be determined using the procedure described by this test method.
3.2.17 viscometer drive module, n—the rotor drive and torque-sensing component of a rotational viscometer.
3.2.18 viscometer module support, n—a part of the test cell alignment device supporting the viscometer drive module.
4. Summary of Test Method
4.1 Used and sooted engine oils are analyzed using a special rotational viscometer with analog or digital output to a computer
program. A specially made glass stator/metal rotor cell is attached to the viscometer and subjected to a programmed temperature
change for both calibration and sample analysis. Following calibration of the rotor-stator set, an approximately 20-mL20 mL test
sample of a test lubricating oil is poured into the stator and preheated for 1.51.5 h to 2.0 h 2.0 h at 90°C90 °C in an oven or water
bath. Shortly after completing the preheating step, the room-temperature rotor is put into the stator containing the heated oil and
coupled to a torque-sensing viscometer head using an adapter to automatically center the rotor in the stator during test. A
programmable low-temperature bath is used to cool the cell at a specified rate of 3°C/h3 °C ⁄h from −5°C−5 °C to the temperature
at which the maximum torque recordable is exceeded when using a speed of 0.30.3 r ⁄ rpm min for the rotor. After the desired
information has been collected, the computer program generates the desired viscometric and rheological values from the recorded
data.
5. Significance and Use
5.1 Significance of Low Temperature, Low Shear Rate, Engine Oil Rheology—The low-temperature, low-shear viscometric
behavior of an engine oil, whether new, used, or sooted, determines whether the oil will flow to the sump inlet screen, then to the
Selby, T. W., “The Use of the Scanning Brookfield Technique to Study the Critical Degree of Gelation of Lubricants at Low Temperatures,” SAE Paper 910746, Society
of Automotive Engineers, 1991.
D7110 − 14
FIG. 1 Test Cell
oil pump, then to the sites in the engine requiring lubrication in sufficient quantity to prevent engine damage immediately or
ultimately after cold temperature starting. Two forms of flow problems have been identified, flow-limited and air-binding
behavior. The first form of flow restriction, flow-limited behavior, is associated with the oil’s viscosity; the second, air-binding
behavior, is associated with gelation.
5.2 Significance of the Test Method—The temperature-scanning technique employed by this test method was designed to
determine the susceptibility of the engine oil to flow-limited and air-binding response to slow cooling conditions by providing
3,4,5
continuous information on the rheological condition of the oil over the temperature range of use. In this way, both viscometric
and gelation response are obtained in one test.
NOTE 1—This test method is one of three related to pumpability related problems. Measurement of low-temperature viscosity by the two other
pumpability test methods, D3829 and D4684, hold the sample in a quiescent state and generate the apparent viscosity of the sample at shear rates ranging
-1
up to 15 s and shear stresses up to 525 Pa 525 Pa at a previously selected temperature. Such difference in test parameters (shear rate, shear stress, sample
motion, temperature scanning, and so forth) can lead to differences in the measured apparent viscosity among these methods with some test oils,
particularly when other rheological factors associated with gelation are present. In addition, the three methods differ considerably in cooling rates.
5.3 Gelation Index and Gelation Index Temperature—This test method has been further developed to yield parameters called
the Gelation Index and Gelation Index Temperature. The first parameter is a measure of the maximum rate of torque increase
caused by the rheological response of the oil as the oil is cooled slowly. The second parameter is the temperature at which the
Gelation Index occurs.
6. Apparatus
6.1 Test Cell—Shown in Fig. 1, consisting of a matched rotor and a stator of the following critical dimensions:
6.1.1 Rotor Dimensions—Critical length is 65.565.5 mm 6 0.1 mm 0.1 mm and critical diameter is 18.4018.40 mm 6 0.02
mm.0.02 mm.
6.1.2 Stator Dimensions—Critical diameter is 22.05 mm (60.02 mm) 22.05 mm (60.02 mm) at whatever length will satisfy the
immersion depth when the upper oil level is a minimum of 15 mm 15 mm below the cooling liquid level over the entire temperature
range.
Shaub, H., “A History of ASTM Accomplishments in Low Temperature Engine Oil Rheology,” Symposium on Low Temperature Lubricant Rheology Measurement and
Relevance to Engine Operation, ASTM STP 1143, Rhodes, R. B., ed., ASTM, 1992, pp. 1-19.
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