ASTM D6080-97(2002)
(Practice)Standard Practice for Defining the Viscosity Characteristics of Hydraulic Fluids
Standard Practice for Defining the Viscosity Characteristics of Hydraulic Fluids
SIGNIFICANCE AND USE
The purpose of this practice is to establish viscosity designations derived from viscosities measured by test methods which have a meaningful relationship to hydraulic fluid performance. This permits lubricant suppliers, lubricant users, and equipment designers to have a uniform and common basis for designating, specifying, or selecting the viscosity characteristics of hydraulic fluids.
This practice is not intended to be a replacement for Classification D 2422. Rather, it is an enhancement intended to provide a better description of the viscosity characteristics of lubricants used as hydraulic fluids.
This practice implies no evaluation of hydraulic oil quality other than its viscosity and shear stability under the conditions specified.
While it is not intended for other functional fluids, this practice may be useful in high-shear-stress applications where viscosity index (VI) improvers are used to extend the useful operating temperature range of the fluid.
This practice does not apply to other lubricants for which viscosity classification systems already exist, for example, SAE J300 for automotive engine oils and SAE J306 for axle and manual transmission lubricants.
SCOPE
1.1 This practice is applicable to all hydraulic fluids based either on petroleum, synthetic, or naturally-occurring base stocks. It is not intended for water-containing hydraulic fluids.
1.2 For determination of viscosities at low temperature, this practice uses millipascalsecond (mPa·s) as the unit of viscosity. For reference, 1 mPa·s is equivalent to 1 centipoise (cP). For determination of viscosities at high temperature, this practice uses millimetre squared per second (mm2/s) as the unit of kinematic viscosity. For reference, 1 mm2/s is equivalent to 1 centistoke (cSt).
1.3 This practice is applicable to fluids ranging in kinematic viscosity from about 4 to 150 mm2/s as measured at a reference temperature of 40°C and to temperatures from -50 to +16°C for a fluid viscosity of 750 mPa·s.
Note 1—Fluids of lesser or greater viscosity than the range described in are seldom used as hydraulic fluids. Any mathematical extrapolation of the system to either higher or lower viscosity grades may not be appropriate. Any need to expand the system should be evaluated on its own merit.
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An American National Standard
Designation: D 6080 – 97 (Reapproved 2002)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 Society of Automotive Engineers (SAE) Standards:
J300 Engine Oil Viscosity Classification
1.1 This practice is applicable to all hydraulic fluids based
J306 Axle and Manual Transmission Lubricant Viscosity
either on petroleum, synthetic, or naturally-occurring base
Classification
stocks. It is not intended for water-containing hydraulic fluids.
1.2 For determination of viscosities at low temperature, this
3. Terminology
practice uses millipascal·second (mPa·s) as the unit of viscos-
3.1 Definitions:
ity. For reference, 1 mPa·s is equivalent to 1 centipoise (cP).
3.1.1 viscosity—the ratio between the applied shear stress
For determination of viscosities at high temperature, this
2 and shear rate.
practiceusesmillimetresquaredpersecond(mm /s)astheunit
3.1.1.1 Discussion—Viscosity is sometimes called the coef-
of kinematic viscosity. For reference, 1 mm /s is equivalent to
ficientofdynamicviscosity.Thiscoefficientisameasureofthe
1 centistoke (cSt).
resistance to flow of the liquid.
1.3 Thispracticeisapplicabletofluidsranginginkinematic
2 3.1.2 kinematic viscosity—the ratio of the viscosity to the
viscosityfromabout4to150mm /sasmeasuredatareference
density of a liquid.
temperature of 40°C and to temperatures from−50 to+16°C
3.1.2.1 Discussion—Kinematicviscosityisameasureofthe
for a fluid viscosity of 750 mPa·s.
resistance to flow of a liquid under gravity.
NOTE 1—Fluids of lesser or greater viscosity than the range described
3.1.3 shear stress—the motivating force per unit area for
in1.3areseldomusedashydraulicfluids.Anymathematicalextrapolation
fluid flow.
of the system to either higher or lower viscosity grades may not be
3.1.4 shear rate—the velocity gradient in fluid flow.
appropriate. Any need to expand the system should be evaluated on its
3.1.5 Newtonian fluid—a fluid that at a given temperature
own merit.
exhibits a constant viscosity at all shear rates or shear stresses.
2. Referenced Documents
3.1.6 non-Newtonian fluid—a fluid that exhibits a viscosity
that varies with changing shear stress or shear rate.
2.1 ASTM Standards:
3.1.7 density—the mass per unit volume.
D445 Test Method for Kinematic Viscosity of Transparent
3.1.8 hydraulic fluid—a fluid used in hydraulic systems for
and Opaque Liquids (and the Calculation of Dynamic
transmitting power.
Viscosity)
3.1.9 viscosity index (VI)—an arbitrary number used to
D2270 Practice for CalculatingViscosity Index from Kine-
characterize the variation of the kinematic viscosity of a fluid
matic Viscosity at 40 and 100°C
with temperature.
D2422 Classification of Industrial Fluid Lubricants by
3.1.10 shear degradation—the decrease in molecular
Viscosity System
weight of a polymeric thickener (VI improver) as a result of
D2983 Test Method for Low-Temperature Viscosity of
exposure to high shear stress.
Lubricants Measured by Brookfield Viscometer
3.1.11 in-service viscosity—the viscosity of fluid during
D5621 Test Method for Sonic Shear Stability of Hydraulic
operation of a hydraulic pump or circuit components.
Fluids
3.1.12 shear stability—the resistance of a polymer-
E29 Practice for Using Significant Digits in Test Data to
thickened fluid to shear degradation.
Determine Conformance with Specifications
4. Summary of Practice
4.1 High VI hydraulic fluids often contain high molecular
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
weight thickeners, called viscosity index (VI) improvers,
ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.N0on
whichimpartnon-Newtoniancharacteristicstothefluid.These
Hydraulic Fluids.
Current edition approved Dec. 10, 2002. Published March 2003. Originally
approved in 1997. Last previous edition approved in 1997 as D6080–97.
Annual Book of ASTM Standards, Vol 05.01.
3 5
Annual Book of ASTM Standards, Vol 05.03. Available from Society of Automotive Engineers, 400 Commonwealth Dr.,
Annual Book of ASTM Standards, Vol 14.02. Warrendale, PA 15096.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 6080 – 97 (2002)
TABLE 1 Low Temperature Viscosity Grades for Hydraulic Fluid
polymers may shear degrade with use, and reduce the in-
Classifications
service viscosity of the fluids.
Temperature,° C, for Brookfield Viscosity
4.2 This practice provides uniform guidelines for character-
A
of 750 mPa·s
Viscosity Grade
izing oils in terms of both their high and low temperature
min max
viscosities before and after exposure to high shear stress.
L5 . −50
4.2.1 Sincetheperformanceoffluidsattemperatureshigher
L7 −49 −42
than 40°C is determined in the worst case, that is, most severe
L10 −41 −33
situation, by the sheared oil viscosity, the viscosity and
L15 −32 −23
L22 −22 −15
viscosity index used to characterize fluids in this practice are
L32 −14 − 8
those of the sheared fluid.
L46 −7 −2
4.2.2 Thispracticeclassifiesoilsatlowtemperaturebytheir L68 − 1 4
L100 5 10
new oil properties. Low temperature viscosities do not de-
L150 11 16
crease greatly, if at all, with polymer shear degradation.
A
The temperature range for a given L-grade is approximately equivalent to that
Furthermore, this approach ensures that the fluid will be
for an ISO grade of the same numerical designation and having a viscosity index
properly classified under the worst-case conditions, that is,
of 100, that is, the temperature range for the L10 grade is approximately the same
as that for an ISO VG 10 grade with a viscosity index of 100.
when the fluid is new.
4.3 This practice may be used with either Newtonian or
non-Newtonian hydraulic fluids. This provides the user with a
Method D2983 is currently being revised with a lower
more reasonable basis to compare fluids than previous prac-
viscosity limit of 500 mPa·s.
tices.
6.1.3 The temperature determined in 6.1.1 shall be rounded
to a whole number in accordance with Practice E29.
5. Significance and Use
6.1.4 The low temperature viscosity grade is determined by
5.1 The purpose of this practice is to establish viscosity
matchingthetemperaturedeterminedin6.1.3withtherequire-
designations derived from viscosities measured by test meth-
ments shown in Table 1.
ods which have a meaningful relationship to hydraulic fluid
6.2 The high temperature viscosity designation of a fluid is
performance. This permits lubricant suppliers, lubricant users,
the 40°C kinematic viscosity (Test Method D445) of a fluid
and equipment designers to have a uniform and common basis
which has been sheared using Test Method D5621.
for designating, specifying, or selecting the viscosity charac-
6.2.1 The kinematic viscosity determined in 6.2 shall be
teristics of hydraulic fluids.
rounded to a whole number in accordance with Practice E29.
5.2 This practice is not intended to be a replacement for
6.2.2 For a fluid known to contain no polymeric compo-
ClassificationD2422.Rather,itisanenhancementintendedto
nents which will shear degrade, the high temperature viscosity
provide a better description of the viscosity characteristics of
designation is the 40°C kinematic viscosity (Test Method
lubricants used as hydraulic fluids.
D445) of the new fluid, rounded per 6.2.1.
5.3 This practice implies no evaluation of hydraulic oil
6.2.3 If the 40°C kinematic viscosity from 6.2.1 fails to
quality other than its viscosity and shear stability under the
meet the same designation consistently (for example, it varies
conditions specified.
becauseofspreadinbasestockorcomponentspecifications,or
5.4 While it is not intended for other functional fluids, this
variability in kinematic viscosity or shear stability measure-
practice may be useful in high-shear-stress applications where
ments),thelowerdesignationmustbeusedtoensureconform-
viscosity index (VI) improvers are used to extend the useful
ance with 6.5 below.
operating temperature range of the fluid.
6.3 The viscosity index designation of the fluid is based on
5.5 This practice does not apply to other lubricants for
the viscosity index as determined using Practice D2270 on
which viscosity classification systems already exist, for ex-
fluid which has been sheared using Test Method D5621.
ample, SAE J300 for automotive engine oils and SAE J306 for
6.3.1 Theviscosityindexdeterminedin6.3shallberounded
axle and manual transmission lubricants.
to the nearest ten units in accordance with Practice E29. This
value is the viscosity index designation.
6. Procedure
6.3.2 For fluids which do not contain polymeric compo-
nents, the viscosity index is determined on the new fluid using
6.1 The low temperature viscosity grade of a fluid is based
Practice D2270. The viscosity index designation for the fluid
on the viscosity of new oil measured using a Brookfield
isestablishedbyroundingthisviscosityindextothenearestten
viscometer, Test Method D2983.
units in accordance with Practice E29.
6.1.1 Theviscosityshallbeinterpolatedfrommeasurements
at three temperatures spanning the temperature at which the
NOTE 2—The guidelines for rounding viscosity in 6.2.1 and 6.2.2 and
viscosity is 750 mPa·s. A smooth graph of these data (log
viscosity index in 6.3.1 and 6.3.2 are specific to this practice and should
viscosity versus temperature) determines the temperature at not be confused with the larger number of significant figures that can be
reported when Test Methods D445 and D2270 are used for other
which the oil has a viscosity of 750 mPa·s.
purposes.
6.1.2 The lower viscosity limit for Test Method D2983 is
currently stated to be 1000 mPa·s.This equipment limitation is 6.3.3 If the viscosity index fails to meet the same designa-
showninTable1ofthatmethod.Newerequipmentisavailable tion consistently, that is, it varies between the lower values for
which permits measurement of lower viscosities and Test one designation and the higher values for the next lower
D 6080 – 97 (2002)
designation (for example, it varies because of spread in base which has a low temperature start-up viscosity limit of 750
stock or component specifications, or variability in kinematic mPa·s, the oil in this example may be used down to at
viscosity or shear stability measurements), the lower designa- least−8°C.
tion must be used to ensure conformance with 6.5 below.
7.2.3 Example 2a—For an oil with the designation:
6.4 For the sake of uniformity of nomenclature in identify-
ISO VG 68
ing the viscosity characteristics of hydraulic fluids, the follow-
L46-57
ing designation shall be used:
the low temperature grade is defined by L46. Reference to
ISO VG xx
Table 1 indicates that this oil has a viscosity of 750 mPa·s at a
Lyy-zz (VI)
temperaturebetween−2and−7°C.Hence,inequipmentwhich
where xx is the new oil viscosity grade as determined by
hasalowtemperaturestart-upviscositylimitof750mPa·s,the
Classification D2422 (Table 2); Lyy is the low temperature
oil in this example may be used down to at least−2°C.
viscositygradeasdeterminedin6.1;zzisthehightemperature
7.2.4 This practice is not quantitative when a manufacturer
sheared viscosity designation as determined in 6.2; and VI is
specifieslowerorhigherstart-upviscositylimits.However,the
the viscosity index designation as determined in 6.3.
process described in 6.1 can be used to determine low
6.4.1 If the new oil viscosity does not meet a grade
temperaturelimitationscorrespondingtoanystart-upviscosity.
described by Classification D2422, the ISO VG xx portion of
7.3 The high temperature designation determined in 6.2 and
the designation does not apply. In such cases, the Lyy-zz (VI)
the viscosity index determined in 6.3, zz (VI), can be used in
designation may still be used, and the use of any other
combination with the data in Figs. 1-4 to estimate high
descriptors for the new oil is at the discretion of the fluid
temperature operating limits (Fig. 1 and Fig. 2) and optimum
marketer.
operating temperatures (Fig. 3 and Fig. 4) for the fluid.
6.4.2 Examples of use of this practice are shown inTable 3.
7.3.1 Fig. 1 and Fig. 2 apply directly to equipment which
6.5 An oil blender may use any manufacturing control that
hasminimumoperatingkinematicviscositylimitsof10and13
seems appropriate to his operation. However, it is the respon- 2
mm /s, respectively.
sibility of the blender to ensure that all production fully meets
7.3.1.1 FindthevaluezzonthehorizontalaxislabeledHigh
the requirements for the viscosity designation on the container.
Temperature Viscosity Designation.
7.3.1.2 Read vertically from the point defined by 7.3.1.1 to
7. Interpretation of Results
the curve corresponding to the viscosity index, VI, interpolat-
7.1 The designation determined for a hydraulic fluid as
ing, if necessary.
described in 6.4 may be used in combination with a manufac-
7.3.1.3 Read horizontally from the point defined by 7.3.1.2
turer’s viscosity recommendations for specific equipment to
to the vertical axis labeled Temperature, °C, for a Kinematic
estimate an acceptable temperature range over which that fluid
Viscosity of 10 (or 13) mm /s. This is the upper temperature
may be used in that equipment.
limit for fluid operation.
7.2 The low temperature grade determined in 6.1, Lyy,
7.3.1.4 Example 1b—For the oil in Example 1a in 7.2.2, the
definesthelowestrecommendedfluidtemperatureatwhichthe
high temperature designation and VI are 40 and 150, respec-
fluidmaybeusedinequipmentwithastart-up,underloadlimit
tively. Assume that the equipment of interest has a recom-
of 750 mPa·s, max.
mendedkinematicviscosityminimumof13mm /s;hence,Fig.
7.2.1 Thelowtemperaturelimitisdeterminedbycomparing
2 should be used.As described in 7.3.1.1, find the value 40 on
the Lyy designation with the corresponding temperature in
the horizontal axis labeled High Temperature Viscosity Desig-
Table 1.
nation. As described in 7.3.1.2, read vertically from 40 until
7.2.2 Example 1a—For an oil with the designation:
intersectingthecurvelabeledVI=150.Finally,asdescribedin
ISO VG 46
7.3.1.3, read horizontally to the vertical axis labeled Tempera-
L32-40 ,
ture, °C, for a Kinematic Viscosity of 13 mm /s. The value
the low temperature grade is defined by L32. Reference to
corresponding to a high temperature viscosity designation of
Table 1 indicates that this oil has a viscosity of 750 mPa·s at a
40 and a viscosity index of 150 is 75°C. Hence, in equipment
temperat
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