ASTM D6080-97(2007)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6080 – 97 (Reapproved 2007)
Standard Practice for
Defining the Viscosity Characteristics of Hydraulic Fluids
This standard is issued under the fixed designation D6080; 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 D2983 Test Method for Low-Temperature Viscosity of
Lubricants Measured by Brookfield Viscometer
1.1 This practice covers all hydraulic fluids based either on
D5621 Test Method for Sonic Shear Stability of Hydraulic
petroleum, synthetic, or naturally-occurring base stocks. It is
Fluids
not intended for water-containing hydraulic fluids.
E29 Practice for Using Significant Digits in Test Data to
1.2 For determination of viscosities at low temperature, this
Determine Conformance with Specifications
practice uses millipascal·second (mPa·s) as the unit of viscos-
2.2 Society of Automotive Engineers (SAE) Standards:
ity. For reference, 1 mPa·s is equivalent to 1 centipoise (cP).
J300 Engine Oil Viscosity Classification
For determination of viscosities at high temperature, this
J306 Axle and Manual Transmission Lubricant Viscosity
practiceusesmillimetresquaredpersecond(mm /s)astheunit
Classification
of kinematic viscosity. For reference, 1 mm /s is equivalent to
1 centistoke (cSt).
3. Terminology
1.3 Thispracticeisapplicabletofluidsranginginkinematic
3.1 Definitions:
viscosityfromabout4to150mm /sasmeasuredatareference
3.1.1 density—the mass per unit volume.
temperature of 40°C and to temperatures from−50 to+16°C
3.1.2 hydraulic fluid—a fluid used in hydraulic systems for
for a fluid viscosity of 750 mPa·s.
transmitting power.
NOTE 1—Fluids of lesser or greater viscosity than the range described
3.1.3 in-service viscosity—the viscosity of fluid during
in1.3areseldomusedashydraulicfluids.Anymathematicalextrapolation
operation of a hydraulic pump or circuit components.
of the system to either higher or lower viscosity grades may not be
3.1.4 kinematic viscosity—the ratio of the viscosity to the
appropriate. Any need to expand the system should be evaluated on its
density of a liquid.
own merit.
3.1.4.1 Discussion—Kinematicviscosityisameasureofthe
2. Referenced Documents
resistance to flow of a liquid under gravity.
3.1.5 Newtonian fluid—a fluid that at a given temperature
2.1 ASTM Standards:
exhibits a constant viscosity at all shear rates or shear stresses.
D445 Test Method for Kinematic Viscosity of Transparent
3.1.6 non-Newtonian fluid—a fluid that exhibits a viscosity
and Opaque Liquids (and Calculation of Dynamic Viscos-
that varies with changing shear stress or shear rate.
ity)
3.1.7 shear degradation—the decrease in molecular weight
D2270 Practice for Calculating Viscosity Index from Kine-
of a polymeric thickener (VI improver) as a result of exposure
matic Viscosity at 40 and 100°C
to high shear stress.
D2422 Classification of Industrial Fluid Lubricants by Vis-
3.1.8 shear rate—the velocity gradient in fluid flow.
cosity System
3.1.9 shear stability—the resistance of a polymer-thickened
fluid to shear degradation.
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
3.1.10 shear stress—the motivating force per unit area for
ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.N0.10
on Specifications. fluid flow.
Current edition approved Nov. 1, 2007. Published January 2008. Originally
3.1.11 viscosity—the ratio between the applied shear stress
approved in 1997. Last previous edition approved in 2002 as D6080–97(2002).
and shear rate.
DOI: 10.1520/D6080-97R07.
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 Available from Society of Automotive Engineers (SAE), 400 Commonwealth
the ASTM website. Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6080 – 97 (2007)
3.1.11.1 Discussion—Viscosity is sometimes called the co- 6. Procedure
efficient of dynamic viscosity. This coefficient is a measure of
6.1 The low temperature viscosity grade of a fluid is based
the resistance to flow of the liquid.
on the viscosity of new oil measured using a Brookfield
3.1.12 viscosity index (VI)—an arbitrary number used to viscometer, Test Method D2983.
characterize the variation of the kinematic viscosity of a fluid 6.1.1 Theviscosityshallbeinterpolatedfrommeasurements
with temperature. at three temperatures spanning the temperature at which the
viscosity is 750 mPa·s. A smooth graph of these data (log
viscosity versus temperature) determines the temperature at
4. Summary of Practice
which the oil has a viscosity of 750 mPa·s.
4.1 High VI hydraulic fluids often contain high molecular
6.1.2 The lower viscosity limit for Test Method D2983 is
weight thickeners, called viscosity index (VI) improvers,
currently stated to be 1000 mPa·s.This equipment limitation is
whichimpartnon-Newtoniancharacteristicstothefluid.These
shown in Table1 of that test method. Newer equipment is
polymers may shear degrade with use, and reduce the in-
available which permits measurement of lower viscosities and
service viscosity of the fluids.
Test Method D2983 is currently being revised with a lower
4.2 This practice provides uniform guidelines for character-
viscosity limit of 500 mPa·s.
izing oils in terms of both their high and low temperature
6.1.3 The temperature determined in 6.1.1 shall be rounded
viscosities before and after exposure to high shear stress.
to a whole number in accordance with Practice E29.
6.1.4 The low temperature viscosity grade is determined by
4.2.1 Sincetheperformanceoffluidsattemperatureshigher
matchingthetemperaturedeterminedin6.1.3withtherequire-
than 40°C is determined in the worst case, that is, most severe
ments shown in Table 1.
situation, by the sheared oil viscosity, the viscosity and
6.2 The high temperature viscosity designation of a fluid is
viscosity index used to characterize fluids in this practice are
the 40°C kinematic viscosity (Test Method D445) of a fluid
those of the sheared fluid.
which has been sheared using Test Method D5621.
4.2.2 Thispracticeclassifiesoilsatlowtemperaturebytheir
6.2.1 The kinematic viscosity determined in 6.2 shall be
new oil properties. Low temperature viscosities do not de-
rounded to a whole number in accordance with Practice E29.
crease greatly, if at all, with polymer shear degradation.
6.2.2 For a fluid known to contain no polymeric compo-
Furthermore, this approach ensures that the fluid will be
nents which will shear degrade, the high temperature viscosity
properly classified under the worst-case conditions, that is,
designation is the 40°C kinematic viscosity (Test Method
when the fluid is new.
D445) of the new fluid, rounded per 6.2.1.
4.3 This practice may be used with either Newtonian or
6.2.3 If the 40°C kinematic viscosity from 6.2.1 fails to
non-Newtonian hydraulic fluids. This provides the user with a
meet the same designation consistently (for example, it varies
more reasonable basis to compare fluids than previous prac-
becauseofspreadinbasestockorcomponentspecifications,or
tices.
variability in kinematic viscosity or shear stability measure-
ments),thelowerdesignationmustbeusedtoensureconform-
5. Significance and Use
ance with 6.5 below.
6.3 The viscosity index designation of the fluid is based on
5.1 The purpose of this practice is to establish viscosity
the viscosity index as determined using Practice D2270 on
designations derived from viscosities measured by test meth-
fluid which has been sheared using Test Method D5621.
ods which have a meaningful relationship to hydraulic fluid
6.3.1 Theviscosityindexdeterminedin6.3shallberounded
performance. This permits lubricant suppliers, lubricant users,
to the nearest ten units in accordance with Practice E29. This
and equipment designers to have a uniform and common basis
value is the viscosity index designation.
for designating, specifying, or selecting the viscosity charac-
teristics of hydraulic fluids.
TABLE 1 Low Temperature Viscosity Grades for Hydraulic Fluid
5.2 This practice is not intended to be a replacement for
Classifications
Classification D2422. Rather, it is an enhancement intended to
Temperature,° C, for Brookfield Viscosity
provide a better description of the viscosity characteristics of
A
of 750 mPa·s
Viscosity Grade
lubricants used as hydraulic fluids.
min max
5.3 This practice implies no evaluation of hydraulic oil
L5 . −50
quality other than its viscosity and shear stability under the
L7 −49 −42
conditions specified. L10 −41 −33
L15 −32 −23
5.4 While it is not intended for other functional fluids, this
L22 −22 −15
practice may be useful in high-shear-stress applications where L32 −14 − 8
L46 −7 −2
viscosity index (VI) improvers are used to extend the useful
L68 − 1 4
operating temperature range of the fluid.
L100 5 10
L150 11 16
5.5 This practice does not apply to other lubricants for
A
The temperature range for a given L-grade is approximately equivalent to that
which viscosity classification systems already exist, for ex-
for an ISO grade of the same numerical designation and having a viscosity index
ample,SAEJ300forautomotiveengineoilsandSAEJ306for
of 100, that is, the temperature range for the L10 grade is approximately the same
axle and manual transmission lubricants. as that for an ISO VG 10 grade with a viscosity index of 100.
D6080 – 97 (2007)
6.3.2 For fluids which do not contain polymeric compo- 7.2 The low temperature grade determined in 6.1, Lyy,
nents, the viscosity index is determined on the new fluid using definesthelowestrecommendedfluidtemperatureatwhichthe
PracticeD2270.Theviscosityindexdesignationforthefluidis fluidmaybeusedinequipmentwithastart-up,underloadlimit
established by rounding this viscosity index to the nearest ten of 750 mPa·s, max.
units in accordance with Practice E29.
7.2.1 Thelowtemperaturelimitisdeterminedbycomparing
the Lyy designation with the corresponding temperature in
NOTE 2—The guidelines for rounding viscosity in 6.2.1 and 6.2.2 and
Table 1.
viscosity index in 6.3.1 and 6.3.2 are specific to this practice and should
not be confused with the larger number of significant figures that can be
7.2.2 Example 1a—For an oil with the designation:
reportedwhenTestMethodsD445andD2270areusedforotherpurposes.
ISO VG 46
L32-40 ,
6.3.3 If the viscosity index fails to meet the same designa-
tion consistently, that is, it varies between the lower values for
the low temperature grade is defined by L32. Reference to
one designation and the higher values for the next lower
Table 1 indicates that this oil has a viscosity of 750 mPa·s at a
designation (for example, it varies because of spread in base
temperature between−8 and−14°C. Hence, in equipment
stock or component specifications, or variability in kinematic
which has a low temperature start-up viscosity limit of 750
viscosity or shear stability measurements), the lower designa-
mPa·s, the oil in this example may be used down to at
tion must be used to ensure conformance with 6.5 below.
least−8°C.
6.4 For the sake of uniformity of nomenclature in identify-
7.2.3 Example 2a—For an oil with the designation:
ing the viscosity characteristics of hydraulic fluids, the follow-
ISO VG 68
ing designation shall be used:
L46-57
ISO VG xx
the low temperature grade is defined by L46. Reference to
Lyy-zz (VI)
Table 1 indicates that this oil has a viscosity of 750 mPa·s at a
where xx is the new oil viscosity grade as determined by
temperaturebetween−2and−7°C.Hence,inequipmentwhich
Classification D2422 (Table 2); Lyy is the low temperature
hasalowtemperaturestart-upviscositylimitof750mPa·s,the
viscositygradeasdeterminedin6.1;zzisthehightemperature
oil in this example may be used down to at least−2°C.
sheared viscosity designation as determined in 6.2; and VI is
7.2.4 This practice is not quantitative when a manufacturer
the viscosity index designation as determined in 6.3.
specifieslowerorhigherstart-upviscositylimits.However,the
6.4.1 If the new oil viscosity does not meet a grade
process described in 6.1 can be used to determine low
described by Classification D2422, the ISO VG xx portion of
temperaturelimitationscorrespondingtoanystart-upviscosity.
the designation does not apply. In such cases, the Lyy-zz (VI)
7.3 The high temperature designation determined in6.2 and
designation may still be used, and the use of any other
the viscosity index determined in 6.3, zz (VI), can be used in
descriptors for the new oil is at the discretion of the fluid
combination with the data in Figs. 1-4 to estimate high
marketer.
temperature operating limits (Fig. 1 and Fig. 2) and optimum
6.4.2 Examples of use of this practice are shown inTable 3.
operating temperatures (Fig. 3 and Fig. 4) for the fluid.
6.5 An oil blender may use any manufacturing control that
7.3.1 Fig. 1 and Fig. 2 apply directly to equipment which
seems appropriate to his operation. However, it is the respon-
hasminimumoperatingkinematicviscositylimitsof10and13
sibility of the blender to ensure that all production fully meets
mm /s, respectively.
the requirements for the viscosity designation on the container.
7.3.1.1 FindthevaluezzonthehorizontalaxislabeledHigh
7. Interpretation of Results
Temperature Viscosity Designation.
7.1 The designation determined for a hydraulic fluid as 7.3.1.2 Read vertically from the point defined by 7.3.1.1 to
described in 6.4 may be used in combination with a manufac- the curve corresponding to the viscosity index, VI, interpolat-
turer’s viscosity recommendations for specific equipment to ing, if necessary.
estimate an acceptable temperature range over which that fluid
7.3.1.3 Read horizontally from the point defined by 7.3.1.2
may be used in that equipment.
to the vertical axis labeled Temperature, °C, for a Kinematic
Viscosity of 10 (or 13) mm /s. This is the upper temperature
limit for fluid operation.
TABLE 2 ISO Viscosity System for Hydraulic Fluids
7.3.1.4 Example 1b—FortheoilinExample1ain7.2.2,the
Kinematic Viscosity Limits,
Mid-Point
high temperature designation and VI are 40 and 150, respec-
Viscosity Grade 2
mm /s at 40°C
Viscosity,
Identification
tively. Assume that the equipment of interest has a recom-
mm /s at 40°C
min max
mendedkinematicviscosityminimumof13mm /s;hence,Fig.
ISO 5 4.6 4.14 5.06
2 should be used.As described in 7.3.1.1, find the value 40 on
ISO 7 6.8 6.12 7.48
ISO 10 10 9.00 11.0 the horizontal axis label
...