ASTM D6896-03(2007)
(Test Method)Standard Test Method for Determination of Yield Stress and Apparent Viscosity of Used Engine Oils at Low Temperature
Standard Test Method for Determination of Yield Stress and Apparent Viscosity of Used Engine Oils at Low Temperature
SIGNIFICANCE AND USE
When an engine oil is cooled, the rate and duration of cooling can affect its yield stress and viscosity. In this laboratory test, used engine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relatively rapid cooling to the final test temperature. As in other low temperature rheological tests such as Test Methods D 3829, D 4684, and D 5133, a preheating condition is required to ensure that all residual waxes are solubilized in the oil prior to the cooldown (that is, remove thermal memory). However, it is also known that highly sooted used diesel engine oils can experience a soot agglomerization phenomenon when heated under quiescent conditions. The current method uses a separate preheat and agitation step to break up any soot agglomerization that may have occurred prior to cooldown. The viscosity of highly sooted diesel engine oils as measured in this test method have been correlated to pressurization times in a motored engine test (1).
Cooling Profiles:
For oils to be tested at -20°C and -25°C, Table X1.1 applies. The cooling profile described in Table X1.1 is based on the viscosity properties of the ASTM Pumpability Reference Oils (PRO). This series of oils includes oils with normal low-temperature flow properties and oils that have been associated with low-temperature pumpability problems (2-7).
SCOPE
1.1 This test method covers the measurement of the yield stress and viscosity of engine oils after cooling at controlled rates over a period of 43 or 45 h to a final test temperature of -20 or -25°C. The viscosity measurements are made at a shear stress of 525 Pa over a shear rate of 0.4 to 15 s-1. This test method is suitable for measurement of viscosities ranging from 4000 mPa·s to >400 000 mPa·s, and is suitable for yield stress measurements of 7 Pa to >350 Pa.
1.2 This test method is applicable for used diesel oils. The applicability and precision to other used or unused engine oils or to petroleum products other than engine oils has not been determined.
1.3 This test method uses the millipascal second (mPa·s) as the unit of viscosity. For information, the equivalent centipoise unit is shown in parentheses.
1.4 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: D6896 − 03(Reapproved 2007)
Standard Test Method for
Determination of Yield Stress and Apparent Viscosity of
1
Used Engine Oils at Low Temperature
This standard is issued under the fixed designation D6896; 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. Terminology
1.1 This test method covers the measurement of the yield 3.1 Definitions:
stress and viscosity of engine oils after cooling at controlled
3.1.1 apparent viscosity—the determined viscosity obtained
rates over a period of 43 or 45 h to a final test temperature of
by use of this test method.
-20 or -25°C. The viscosity measurements are made at a shear
3.1.2 Newtonian oil or fluid—an oil or fluid that at a given
-1
stress of 525 Pa over a shear rate of 0.4 to 15 s . This test
temperature exhibits a constant viscosity at all shear rates or
method is suitable for measurement of viscosities ranging from
shear stresses.
4000 mPa·s to >400 000 mPa·s, and is suitable for yield stress
3.1.3 non-Newtonian oil or fluid—an oil or fluid that at a
measurements of 7 Pa to >350 Pa.
given temperature exhibits a viscosity that varies with chang-
1.2 This test method is applicable for used diesel oils. The
ing shear stress or shear rate.
applicability and precision to other used or unused engine oils
3.1.4 shear rate—the velocity gradient in fluid flow. For a
or to petroleum products other than engine oils has not been
Newtonian fluid in a concentric cylinder rotary viscometer in
determined.
which the shear stress is measured at the inner cylinder surface
1.3 This test method uses the millipascal second (mPa·s) as
(such as the apparatus described in 6.1), and ignoring any end
the unit of viscosity. For information, the equivalent centipoise
effects, the shear rate is given as follows:
unit is shown in parentheses.
2
2 Ω R
~ !
s
1.4 This standard does not purport to address all of the G 5 (1)
r 2 2
R 2 R
s r
safety concerns, if any, associated with its use. It is the
2
4 π R
~ !
s
responsibility of the user of this standard to establish appro-
5 (2)
2 2
t R 2 R
~ !
s r
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
where:
G = shear rate at the surface of the rotor in reciprocal
r
2. Referenced Documents
-1
seconds, s ,
2
2.1 ASTM Standards: Ω = angular velocity, rad/s,
R = stator radius, mm,
D3829 Test Method for Predicting the Borderline Pumping
s
R = rotor radius, mm, and
Temperature of Engine Oil r
t = time for one revolution of the rotor, s.
D4684 Test Method for Determination of Yield Stress and
Apparent Viscosity of Engine Oils at Low Temperature
For the specific apparatus described in 6.1,
D5133 Test Method for Low Temperature, Low Shear Rate,
G 5 63/t (3)
r
Viscosity/Temperature Dependence of Lubricating Oils
3.1.5 shear stress—the motivating force per unit area for
Using a Temperature-Scanning Technique
fluid flow. For the rotary viscometer being described, the rotor
surface is the area under shear or the shear area.
26
1 T 5 9.81 M ~R 1R ! 310 (4)
This test method is under the jurisdiction of ASTM Committee D02 on r o t
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
TT
r
9
D02.07 on Flow Properties.
S 5 310 (5)
r 2
2 π R h
~ !
r
Current edition approved Nov. 1, 2007. Published January 2008. Originally
ϵ1
approved in 2003. Last previous edition approved in 2003 as D6896–03 . DOI:
where:
10.1520/D6896-03R07.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
T = torque applied to rotor, N·m,
r
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
M = applied mass, g,
Standards volume information, refer to the standard’s Document Summary page on
R = radius of the shaft, mm,
o
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6896 − 03 (2007)
in this test method have been correlated to pressurization times
R = radius of the string, mm,
t
3
in a motored engine test (1).
S = shear stress at the rotor surface, Pa, and
r
h = height of the rotor, mm.
5.2 Cooling Profiles:
For the dimensions given in 6.1.1, 5.2.1 For oils to be tested at -20°C and -25°C, Table X1.1
applies.ThecoolingprofiledescribedinTableX1.1isbasedon
26
T 5 31.7 M 310 (6)
r
the viscosity properties of the ASTM Pumpability Reference
S 5 3.5 M (7)
r
Oils (PRO). This series of oils includes oils with normal
3.1.6 viscosity—the ratio between the applied shear stress
low-temperature flow properties and o
...
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