ASTM D5481-96
(Test Method)Standard Test Method for Measuring Apparent Viscosity at High-Temperature and High-Shear Rate by Multicell Capillary Viscometer
Standard Test Method for Measuring Apparent Viscosity at High-Temperature and High-Shear Rate by Multicell Capillary Viscometer
SCOPE
1.1 This test method covers the laboratory determination of high-temperature high-shear (HTHS) viscosity of engine oils at a temperature of 150°C using a multicell capillary viscometer containing pressure, temperature, and timing instrumentation. The shear rate for this test method corresponds to an apparent shear rate at the wall of 1.4 million reciprocal seconds (1.4 10 6 s1). This shear rate has been found to decrease the discrepancy between this test method and other high-temperature high-shear test methods3 used for engine oil specifications. Viscosities are determined directly from calibrations that have been established with Newtonian oils with viscosities from 2 to 5 mPa·s at 150°C.
1.2 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: D 5481 – 96 An American National Standard
Standard Test Method for
Measuring Apparent Viscosity at High-Temperature and
High-Shear Rate by Multicell Capillary Viscometer
This standard is issued under the fixed designation D 5481; 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.
INTRODUCTION
Several different configurations of capillary viscometers have been successfully used for measuring
the viscosity of engine oils at the high shear rates and high temperatures that occur in engines. See Test
Method D 4624. This test method covers the use of a single apparatus at a single temperature and
single shear rate to achieve greater uniformity and improved precision.
1. Scope Rate and High Temperature by Tapered Bearing Simula-
tor
1.1 This test method covers the laboratory determination of
D 4741 Test Method for Measuring Viscosity at High Tem-
high-temperature high-shear (HTHS) viscosity of engine oils at
perature and High Shear Rate by Tapered Plug Viscom-
a temperature of 150°C using a multicell capillary viscometer
eter
containing pressure, temperature, and timing instrumentation.
The shear rate for this test method corresponds to an apparent
3. Terminology
shear rate at the wall of 1.4 million reciprocal seconds
6 −1 3
3.1 Definitions:
(1.4 3 10 s ). This shear rate has been found to decrease the
3.1.1 apparent shear rate at the wall—shear rate at the wall
discrepancy between this test method and other high-
of the capillary calculated for a Newtonian fluid, as follows:
temperature high-shear test methods used for engine oil
specifications. Viscosities are determined directly from calibra-
S 5 4V/pR t (1)
a
tions that have been established with Newtonian oils with
where:
viscosities from 2 to 5 mPa·s at 150°C.
−1
S 5 apparent shear rate at the wall, s ,
a
1.2 This standard does not purport to address all of the
V 5 volume, mm ,
safety concerns, if any, associated with its use. It is the
R 5 capillary radius, mm, and
responsibility of the user of this standard to establish appro-
t 5 measured flow time, s.
priate safety and health practices and determine the applica-
3.1.1.1 Discussion—The actual shear rate at the wall will
bility of regulatory limitations prior to use.
differ for a non-Newtonian fluid.
3.1.2 apparent viscosity—the determined viscosity obtained
2. Referenced Documents
by this test method.
2.1 ASTM Standards:
3.1.3 density—mass per unit volume.
D 4624 Test Method for Measuring Apparent Viscosity by
3.1.3.1 Discussion—In the SI, the unit of density is the
Capillary Viscometer at High Shear Rate and High Tem-
kilogram per metre cubed (kg/m ); the gram per cubic centi-
perature
3 3 −3 3
metre (g/cm ) is often used. One kg/m is 10 g/cm .
D 4683 Test Method for Measuring Viscosity at High Shear
3.1.4 kinematic viscosity—the ratio of the viscosity to the
density of the fluid.
3.1.4.1 Discussion—Kinematic viscosity is a measure of a
fluid’s resistance to flow under the force of gravity. In the SI,
This test method is under the jurisdiction of ASTM Committee D-2 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
the unit of kinematic viscosity is the metre squared per second
D02.07.0B on High Temperature Rheology of Non-Newtonian Fluids.
(m /s); for practical use, a submultiple (millimetre squared per
Current edition approved Apr. 10, 1996. Published June 1996. Originally
second, mm /s) is more convenient. The centistoke (cSt) is 1
published as D 5481 – 93. Last previous edition D 5481 – 93.
Manning, R. E., and Lloyd, W. A., “Multicell High Temperature High-Shear mm /s and is often used.
Capillary Viscometer,” SAE Paper 861562. Available from Society of Automotive
3.1.5 Newtonian oil or fluid—an oil or fluid that exhibits a
Engineers, 400 Commonwealth Dr., Warrendale, PA 15096.
constant viscosity at all shear rates or shear stresses.
Girshick, F., “Non-Newtonian Fluid Dynamics in High Temperature High
Shear Capillary Viscometers,” SAE Paper 922288. Available from Society of
Automotive Engineers, 400 Commonwealth Dr., Warrendale, PA 15096.
Annual Book of ASTM Standards, Vol 05.02.
Annual Book of ASTM Standards, Vol 05.03.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 5481
3.1.6 non-Newtonian oil or fluid—an oil or fluid that exhib- to determine the viscosity corresponding to the measured
its a viscosity that varies with changing shear rate or shear pressure.
stress. 4.2 Each viscometric cell is calibrated by establishing the
3.1.7 shear rate—the spatial gradient of velocity in laminar relationship between pressure and flow rate for a series of
flow; the derivative of velocity with respect to distance in a Newtonian oils of known viscosity.
direction perpendicular to the direction of flow.
5. Significance and Use
3.1.7.1 Discussion—The derived unit of shear rate is veloc-
5.1 Viscosity is an important property of fluid lubricants.
ity divided by length. With the time in seconds and with
The viscosity of all fluids varies with temperature. Many
consistent units of length, shear rate becomes reciprocal
−1
common petroleum lubricants are non-Newtonian: their vis-
seconds, or s .
cosity also varies with shear rate. The usefulness of the
3.1.8 shear stress—force per area of fluid in the direction of
viscosity of lubricants is greatest when the viscosity is mea-
flow.
sured at or near the conditions of shear rate and temperature
3.1.8.1 Discussion—In a capillary viscometer, the signifi-
that the lubricants will experience in service.
cant shear stress is the shear stress at the wall, that is, the total
5.2 The conditions of shear rate and temperature of this test
force acting on the cross section of the capillary divided by the
method are thought to be representative of those in the bearing
area of the inside surface of the capillary. The shear stress at the
of automotive engines in severe service.
wall does not depend on the fluid properties (that is, Newtonian
5.3 Many equipment manufacturers and lubricant specifica-
or non-Newtonian). The SI unit for shear stress is the pascal
tions require a minimum high-temperature high-shear viscosity
(Pa). Mathematically, the shear stress at the wall of a capillary
6 −1
at 150°C and 10 s . The shear rate in capillary viscometers
viscometer is as follows:
varies across the radius of the capillary. The apparent shear rate
Z 5 PR/2L (2)
at the wall for this test method is increased to compensate for
the variable shear rate.
where:
Z 5 shear stress, Pa, 5.4 This test was evaluated in an ASTM cooperative pro-
P 5 pressure drop, Pa,
gram.
R 5 capillary radius, and
6. Apparatus
L 5 capillary length in consistent units.
3.1.9 viscosity—the ratio between shear stress and shear rate 6.1 High-Temperature High-Shear (HTHS)
at the same location.
Viscomete, consisting of several viscometer cells in a
3.1.9.1 Discussion—Viscosity is sometimes called the coef- temperature-controlled block and including means for control-
ficient of viscosity, or the dynamic viscosity. It is a measure of
ling and measuring temperature and applied pressure and for
a fluid’s resistance to flow. In the SI, the unit of viscosity is a
timing the flow of a predetermined volume of test oil. Each
pascal second (Pa·s); for practical use a submultiple (millipas-
viscometric cell contains a precision glass capillary and means
cal second, mPa·s) is more convenient. The centipoise (cP) is
for adjusting the test oil volume to the predetermined value.
1 mPa·s and is often used.
6.1.1 The HTHS viscometer has the following typical di-
3.2 Definitions of Terms Specific to This Standard:
mensions and specifications:
3.2.1 calibrations oils—those oils used for establishing the
Diameter of capillary 0.15 mm
Length of capillary 15 to 18 mm
instrument’s reference framework of apparent viscosity versus
Temperature control 150 6 0.1°C
pressure drop from which the apparent viscosities of the test
Pressure range 350 to 3500 KPa (50 to 500 psi)
oils are determined.
Pressure control 61%
Sample volume 7 6 1mL
3.2.1.1 Discussion—Calibration oils, which are Newtonian
fluids, are available commercially or can be blended by the
6.1.2 The thermometer for measuring the temperature of the
user.
block is a pre-set digital resistance thermometer. The accuracy
3.2.2 test oil—any oil for which the apparent viscosity is to
of this thermometer may be checked by means of a special
be determined by the test method.
thermowell and calibrated thermometer whose accuracy is
3.2.3 viscometric cell—that part of the viscometer compris-
60.1°C or better. See manufacturer’s recommendations for
ing all parts which may be wet by the test sample, including
procedure.
exit tube, working capillary, fill tube, pressure/exhaust connec-
7. Reagents and Materials
tion, plug valve, and fill reservoir.
7.1 Newtonian Oils, having certified viscosities of 2 to 7
4. Summary of Test Method
mPa·s at 150°C. See Table 1.
7.2 Non-Newtonian Reference Sample, having a certified
4.1 The viscosity of the test oil in any of the viscometric
6 −1
cells is obtained by determining the pressure required to viscosity at 150°C and 10 s .
achieve a flow rate corresponding to an apparent shear rate at 7.3 Carbon Dioxide or Nitrogen Cylinder, with reducer
6 −1
the wall of 1.4 3 10 s . The calibration of each cell is used valve having a maximum pressure of at least 500 psi (3500 Pa).
Report is available from ASTM Headquarters. Request RR:D02-1378.
6 8
Calibration oils, suitable for this purpose, are available from Cannon Instru- A source of supply is Cannon Instrument Co., P.O. Box 16, State College, PA
ment Co., P. O. Box 16, State College, PA 16804. 16804.
D 5481
TABLE 1 Calibration Oils
the result is confirmed by a repeat run, look for the source of
Approximate the trouble, rectify it, and repeat the entire calibration proce-
Approximate Pressure for Test Method
A
Viscosity
Calibration Oil dure, if necessary. Some possible steps to find the source of the
(mPa·s) psi kPa
trouble are to check the system thoroughly for faults, including
foreign material in the capillary, verify the fidelity of the
HT39 2.0 225 1500
HT75 2.7 290 2000
operating procedure, and accuracy of temperature control, and
HT150 3.7 375 2500
readout.
HT240 5.0 480 3300
HT390 7.0 645 4500 9.3 Stability of Temperature Calibration—Check the cali-
A
bration of the temperature sensor at least once a year using a
Consult the supplier for specific values.
standardized thermometer inserted in the thermowell in the
aluminum block.
8. Sampling
8.1 A representative sample of test oil, free from suspended 10. Procedure
solid material and water, is necessary to obtain valid results.
10.1 Bring the viscometer to the test temperature and allow
When the sample is suspected to contain suspended material,
test temperature to stabilize for at least 30 min. Because the
filter with about 10-μm filter paper.
viscometer uses only a small amount of electrical power, it may
be desirable to leave the viscometer at test temperature unless
9. Calibration and Standardization
use is not anticipated for an extended period of time.
9.1 Calibration:
10.2 Flush the previous sample with 4 to 6 mL of the new
9.1.1 The volume and capillary diameter of each viscomet-
test sample. Open the plug valve. Warning: Always keep the
ric cell is provided by the manufacturer, and the flow time, t ,
o
plug valve closed except when charging or adjusting the
corresponding to an apparent shear rate at the wall of 1.4 3 10
volume of sample; NEVER turn on the pressure with the plug
−1
s is calculated by the manufacturer using the following
valve open. Inserta4to 6-mL test sample, and close the plug
equation:
valve. Turn on the pressure (it is not necessary to adjust the
6 3
pressure from the previous run) until the flush sample has
t 5 4V/1.4*10 pR (3)
o
passed through the capillary to waste. It is not necessary to
where symbols are defined as in 3.1.1.
achieve temperature equilibrium since no time measurement is
9.1.2 Using a minimum of four Newtonian calibration oils
being made. Turn off the pressure.
covering the viscosity range from 2 to 5 mPa·s (cP) at 150°C,
10.3 Chargea9to11-mL test sample into the viscometric
determine the relationship between pressure and flow rate. The
cell by opening the plug valve, inserting the test sample, and
pressure should be adjusted for each calibration oil such that
then closing the plug valve.
the flow time is within 620 % of the nominal flow time, t .
o
10.4 Repeat 10.2 and 10.3 for each of the viscometric cells.
Make three determinations for each oil in each cell.
10.5 Allow 15 min for the test sample to attain 150 6 0.1°C.
9.1.2.1 The following relationship can be used to express
10.6 After temperature equilibrium has been established,
the data:
ensure that the plug valve is closed on each cell and make
C t
measurement of efflux time and pressure as follows:
h5 C ·t·P 2 · 1 1 C · 1 2 (4)
F G F S DG
1 3
t t
o
10.6.1 From the calibration of the viscometric cell and the
expected viscosity of the sample (if known), estimate the
where:
required pressure to achieve the nominal flow time, t (see
o
h5 viscosity, mPa·s,
9.1.1). Table 2 provides a guide for setting pressure if the SAE
t 5 flow time, s,
viscosity grade is known. Adjust the pressure in the ballast tank
P 5 pressure, kPa or psi, and
C ,C ,C 5 coefficients specific to each viscometer cell. to this value within 61 %; allow approximately 10 s for this
1 2 3
pressure to stabilize.
9.1.2.2 Coefficient C is specific to the units in which
pressure is expressed, as well as to each cell. Coefficient C 10.6.2 Reset the timer to zero.
10.6.3 Open the plug valve and withdraw excess sample by
will be essentially constant over the relatively narrow range of
shear rates and viscosities of interest in measurement of the vacuum through the filling tube until no more liquid is being
high-temperature viscosity of automotive engine oil. In more withdrawn. Immediately close plug valve and immediately
general applications, C may not be constant for all values of proceed to 10.6.4.
Reynolds Number. 10.6.4 Turn on the run switch for the viscometric cell. Read
and record the pressure approximately 10 s after turning on the
9.1.2.3 Annex A1 describes the procedure for determining
coefficients C , C , and C . pressure switch.
1 2 3
9.2 Stability of Viscosity Calibration—Check the stability of
TABLE 2 Approximate Pressure for Test Method
the calibration by running a calibration oil
...
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