ASTM D6896-03e1

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).3  
Cooling Profiles:
5.2.1 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 mPas 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 (mPas) 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.

General Information

• Status: Historical
• Publication Date: 09-Mar-2003
• ICS: 17.060 - Measurement of volume, mass, density, viscosity
• ICS: 43.060.40 - Fuel systems
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.07 - Flow Properties

Relations

• Replaced By: ASTM D6896-03(2007) - Standard Test Method for Determination of Yield Stress and Apparent Viscosity of Used Engine Oils at Low Temperature
• Effective Date: 01-Nov-2007

Standards Content (Sample)

An American National Standard
e1
Designation: D 6896 – 03
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 D 6896; 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 (e) indicates an editorial change since the last revision or reapproval.
1
e NOTE—Table X1.3 was corrected editorially in August 2004.
1. Scope 3.1.1 apparent viscosity—the determined viscosity obtained
by use of this test method.
1.1 This test method covers the measurement of the yield
3.1.2 Newtonian oil or fluid—an oil or fluid that at a given
stress and viscosity of engine oils after cooling at controlled
temperature exhibits a constant viscosity at all shear rates or
rates over a period of 43 or 45 h to a final test temperature of
shear stresses.
-20 or -25°C. The viscosity measurements are made at a shear
-1
3.1.3 non-Newtonian oil or fluid—an oil or fluid that at a
stress of 525 Pa over a shear rate of 0.4 to 15 s . This test
given temperature exhibits a viscosity that varies with chang-
method is suitable for measurement of viscosities ranging from
ing shear stress or shear rate.
4000 mPa·s to >400 000 mPa·s, and is suitable for yield stress
3.1.4 shear rate—the velocity gradient in fluid flow. For a
measurements of 7 Pa to >350 Pa.
Newtonian fluid in a concentric cylinder rotary viscometer in
1.2 This test method is applicable for used diesel oils. The
which the shear stress is measured at the inner cylinder surface
applicability and precision to other used or unused engine oils
(such as the apparatus described in 6.1), and ignoring any end
or to petroleum products other than engine oils has not been
effects, the shear rate is given as follows:
determined.
2
1.3 This test method uses the millipascal second (mPa·s) as
2~V!R
s
G 5 (1)
r
2 2
the unit of viscosity. For information, the equivalent centipoise
R 2 R
s r
unit is shown in parentheses.
2
4~p!R
s
1.4 This standard does not purport to address all of the
5 (2)
2 2
t ~R 2 R !
s r
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
where:
priate safety and health practices and determine the applica-
G = shear rate at the surface of the rotor in reciprocal
r
bility of regulatory limitations prior to use. -1
seconds, s ,
V = angular velocity, rad/s,
2. Referenced Documents
R = stator radius, mm,
s
2.1 ASTM Standards:
R = rotor radius, mm, and
r
D 3829 Test Method for Predicting the Borderline Pumping
t = time for one revolution of the rotor, s.
2
Temperature of Engine Oil
For the specific apparatus described in 6.1,
D 4684 Test Method for Determination of Yield Stress and
G 5 63/t (3)
r
2
Apparent Viscosity of Engine Oils at Low Temperature
3.1.5 shear stress—the motivating force per unit area for
D 5133 Test Method for Low Temperature, Low Shear
fluid flow. For the rotary viscometer being described, the rotor
Rate, Viscosity/Temperature Dependence of Lubricating
2
surface is the area under shear or the shear area.
Oils Using a Temperature-Scanning Technique
26
T 5 9.81 M ~R 1 R ! 3 10 (4)
r o t
3. Terminology
TT
r
9
S 5 3 10 (5)
3.1 Definitions:
r
2
2~p!R h
r
where:
1
T = torque applied to rotor, N·m,
This test method is under the jurisdiction of ASTM Committee D02 on
r
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee M = applied mass, g,
D02.07 on Flow Properties.
R = radius of the shaft, mm,
o
Current edition approved March 10, 2003. Published May 2003.
R = radius of the string, mm,
2
t
Annual Book of ASTM Standards, Vol 05.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6896–03
in this test method have been correlated to pressurization times
S = shear stress at the rotor surface, Pa, and
r
3
in a motored engine test (1).
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
26
T 5 31.7 M 3 10 (6)
r applies. The cooling profile described in Table X1.1 is based on
S 5 3.5 M (7) the viscosity properties of the ASTM Pumpability Reference
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 oils that have been
and rate of shear, sometimes called the coefficient of dynamic
associated with low-temperature pumpability problems (2-7).
viscosity. This value is thus a measure of the resistance to flow
of the liquid. The SI unit of viscosity is the pascal second Pa·s.
6. Apparatus
A centipoise (cP) is one millipascal second mPa·s. 4
6.1 Mini-Rotary Viscometer , an apparatus that consist
...