ASTM D7721-11
(Practice)Standard Practice for Determining the Effect of Fluid Selection on Hydraulic System or Component Efficiency
Standard Practice for Determining the Effect of Fluid Selection on Hydraulic System or Component Efficiency
SIGNIFICANCE AND USE
The purpose of a hydraulic fluid is to cool and lubricate fluid power components, as well as transmit power. Several standard test methods are available to measure the lubrication performance of hydraulic fluids. This practice provides uniform guidelines for comparing fluids in terms of their power-transmitting abilities as reflected in their effect on hydraulic system or component efficiency.
General—Energy efficiency benefits of hydraulic fluids are the differences between two large numbers. Consequently, it is essential to ensure that the differences observed are statistically valid (within defined confidence limits, typically 95%) and that proper precautions to ensure the necessary experimental controls have been put in place to compare the energy efficiency performance of two or more different hydraulic fluids under identical operating conditions.
Practical advantages of enhanced hydraulic system efficiency may include increased productivity (faster machine cycle time), reduced power consumption (electricity or fuel), and reduced environmental impact (lowered emissions).
This practice implies no evaluation of hydraulic fluid quality other than its effect on hydraulic system efficiency.
SCOPE
1.1 This practice covers all hydraulic fluids.
1.2 This practice is applicable to both laboratory and field evaluations.
1.3 This practice gives overall guidelines for conducting science-based evaluations. It does not prescribe a specific efficiency test methodology.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7721 − 11
Standard Practice for
Determining the Effect of Fluid Selection on Hydraulic
System or Component Efficiency
This standard is issued under the fixed designation D7721; 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 practice covers all hydraulic fluids. 3.1 For additional definitions related to petroleum products
and lubricants, please refer to Terminology D4175. For addi-
1.2 This practice is applicable to both laboratory and field
tional definitions related to fluid power systems and
evaluations.
components, please refer to ISO 5598.
1.3 This practice gives overall guidelines for conducting
3.2 Definitions:
science-based evaluations. It does not prescribe a specific
3.2.1 component, n—of a hydraulic system, an individual
efficiency test methodology.
unit, excluding piping, comprising one or more parts designed
1.4 The values stated in SI units are to be regarded as
to be a functional part of a fluid power system, for example,
standard. No other units of measurement are included in this
cylinder, motor, valve, or filter.
standard.
3.2.2 critical parts, n—those components used in the test
1.5 This standard does not purport to address all of the
that are known to affect test severity.
safety concerns, if any, associated with its use. It is the
3.2.3 fit for use, n—product, system, or service that is
responsibility of the user of this standard to establish appro-
suitable for its intended use.
priate safety and health practices and determine the applica-
3.2.4 grade, n—designation given a material by a manufac-
bility of regulatory limitations prior to use.
turer so that it is always reproduced to the same specifications
established by the manufacturer.
2. Referenced Documents
3.2.5 hydraulic fluid, n—liquid used in hydraulic systems
2.1 ASTM Standards:
for lubrication and transmission of power.
D4174 Practice for Cleaning, Flushing, and Purification of
3.2.6 hydraulic system, n—fluid power system that is an
Petroleum Fluid Hydraulic Systems
arrangement of interconnected components which generates,
D4175 Terminology Relating to Petroleum, Petroleum
transmits, controls and converts fluid power energy.
Products, and Lubricants
3.2.7 hydromechanical motor effıciency, n—ratio of the
2.2 ISO Standards:
actual torque to the derived torque.
ISO 4391 Hydraulic fluid power—Pumps, motors and inte-
gral transmissions—parameter definitions and letter sym- 3.2.8 hydromechanical pump effıciency, n—ratio of the de-
bols rived displacement to absorbed hydraulic torque.
ISO 5598 Fluid power systems & components - Vocabulary
3.2.9 motor overall effıciency, n—ratio of the mechanical
ISO 8426 Hydraulic fluid power—Positive displacement
output power to the power transferred from the liquid at its
pumps and motors—Determination of derived capacity
passage through the motor.
3.2.10 motor volumetric effıciency, n—ratio of the derived
inlet flow rate to the effective outlet flow rate.
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
3.2.11 outlier, n—result far enough in magnitude from other
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.N0 on Hydraulic Fluids. results to be considered not part of the set.
Current edition approved June 1, 2011. Published September 2011.
3.2.11.1 Discussion—For purposes of this practice, classifi-
DOI:10.1520/D7721–11.
cation of a result as an outlier shall be justified by statistical
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
criteria in comparison with the valid data points.
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
3.2.12 pump overall effıciency, n—ratio of the power trans-
the ASTM website.
ferred to the liquid, at its passage through the pump, to the
Available from International Organization for Standardization (ISO), 1, ch. de
la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org. mechanical input power.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7721 − 11
3.2.13 pump volumetric effıciency, n—ratio of the effective it is essential to ensure that the differences observed are
output flow rate to the derived output flow rate. statistically valid (within defined confidence limits, typically
95%) and that proper precautions to ensure the necessary
3.2.14 reference oil, n—oil of known performance charac-
experimental controls have been put in place to compare the
teristics used as a basis for comparison.
energyefficiencyperformanceoftwoormoredifferenthydrau-
3.2.14.1 Discussion—For purposes of this practice, the ref-
lic fluids under identical operating conditions.
erenceoilmaybeahydraulicfluidofanysuitablecomposition.
5.3 Practical advantages of enhanced hydraulic system ef-
3.2.15 test oil, n—any oil subjected to evaluation in an
ficiency may include increased productivity (faster machine
established procedure.
cycle time), reduced power consumption (electricity or fuel),
3.2.15.1 Discussion—For purposes of this practice, the test
and reduced environmental impact (lowered emissions).
oil may be a hydraulic fluid of any suitable composition.
5.4 This practice implies no evaluation of hydraulic fluid
3.3 Definitions of Terms Specific to This Standard:
quality other than its effect on hydraulic system efficiency.
3.3.1 design of experiment, DOE, n—statistical arrangement
in which an experimental program is to be conducted and the
6. Procedure
selection of the levels (versions) of one or more factors or
factor combinations to be included in the experiment.
6.1 Protocol—A successful outcome is dependent on an
3.3.2 duty cycle, n—time interval devoted to starting, evaluation of goals and methods at the outset along with an
running, stopping, and idling when a device is used for assessment of potential sources of error. Such an evaluation
intermittentdutyandthetimespentoperatingatdifferentlevels requires a clearly defined test protocol that shall include: (1)
of rated capacity. statistical design of experiment and analysis, (2) fluid order
evaluation,(3)equipmentselection,(4)analysisandmitigation
3.3.3 effıciency improvement, n—difference in system or
of the test variables, and (5) appropriate data collection
component behavior between two fluids and this difference can
methods. This ensures that both the reference and test oils are
be defined as an improvement in fuel consumption, work
evaluated in exactly the same way thus ensuring a valid
produced, electrical power draw, flow rate, temperature
comparison is made.
reduction, and so forth.
6.1.1 Site Coordinator/Personnel Training—Because of the
3.3.3.1 Discussion—This improvement is expressed as a
complexity of field trials, it is recommended that a designated
percent increase that is obtained by dividing the test oil
site coordinator be used to ensure any questions or concerns
performance by the reference oil performance and multiplying
from site personnel are addressed and that test protocols are
by 100 or, if appropriate, for example, temperature, then actual
being followed.
values can be reported.
6.2 Statistical Design of Experiment (DOE)—A statistical
3.3.4 power factor, n—in electrical circuits, the ratio of
DOE system shall be used to account for any test variability
energy consumed (watts) versus the product of input voltage
and ensure any differences observed are significant to 95%
(volts) times input current (amps).
confidence limits.
3.3.4.1 Discussion—The power factor is the dimensionless
ratio of energy used compared to the energy flowing through
6.3 Test Control—There are a number of test variables that
the wires.
can significantly influence efficiency measurements and shall
be controlled.
4. Summary of Practice
6.3.1 Fluid Order—To account for the potential impact of
4.1 The purpose of this practice is to define minimum
machine drift/bias and lubricant carryover effects, it is highly
technical requirements needed statistically to validate energy
recommended that the efficiency of the reference fluid (A) be
efficiency performance comparisons of two or more hydraulic
evaluated before and after each test fluid (B) evaluation.
fluids in controlled laboratory or field evaluations.
Alternating the reference fluid and test fluid in an ABA or
ABAB test sequence is satisfactory. When operator or test
4.2 Controls and considerations based on both technical
equipment variables may have a significant impact on the test
factors and practical experience are included.
outcome, the operators and test equipment should also be
4.3 Requirements for test planning, testing conduct, and
alternated in a systematic manner.
data analysis and reporting are described.
6.3.2 Carryover Control—Hydraulic systems may retain a
significant amount of residual fluid after they have been
5. Significance and Use
drained. This residual fluid can create cross-contamination.
5.1 The purpose of a hydraulic fluid is to cool and lubricate
The level of cross-contamination between test fluids shall be
fluid power components, as well as transmit power. Several
kept to a minimum. In preparation for the evaluation of each
standard test methods are available to measure the lubrication
fluid, the hydraulic system should be filled, flushed, and
performance of hydraulic fluids. This practice provides uni-
drained of the test fluid at least once. Practice D4174 provides
form guidelines for comparing fluids in terms of their power-
specific recommendations to facilitate this process. The cross-
transmitting abilities as reflected in their effect on hydraulic
contamination level in the test fluid ideally should not exceed
system or component efficiency.
10% in field trials and 1% in laboratory evaluations. the
5.2 General—Energy efficiency benefits of hydraulic fluids amount of cross-contamination should be determined using an
are the differences between two large numbers. Consequently, appropriate test method such as elemental analysis, mass
D7721 − 11
balance,infraredspectroscopy,orviscosity.Thisinformationis 6.3.10 Electronic (Controlled for Power Factor)—In sys-
to be included with the test results. tems drawing power from a common source such as plant
6.3.2.1 Flushing Requirements for Surface Active Fluids equipment, changes in load separate from the test equipment
(for example, Friction Modified)—If any of the fluids under can affect electrical quality. In systems that may be affected,
evaluation contain surface-active friction-reducing materials comparable power quality (for example, amps, watts, and
(for example, friction modifiers), then extra precautions to power factor) shall be included in the test protocol.
minimize carryover effects may be required. One of these
6.3.11 An accurate location to measure electrical power
precautions shall be to use a flush oil that is capable of
consumption is between the motor and motor starter.
removing such surface-active additives.
6.3.12 Fuel Measurement—Fuel gauges on commercial hy-
6.3.3 Environmental Conditions (for example, Temperature,
draulic machines are designed to indicate when fuel replenish-
Humidity, and Precipitation)—It is important to minimize the
ment is necessary. Consequently, fuel gauge accuracy is
effect of differences in environmental conditions such as
insufficient for efficiency studies. Fuel levels may be more
ambient temperature during the conduct of a field test. This
accurately controlled by being careful to refuel on a level
mayincludetestingonlyduringdefinedperiodsofthedayover
surface and using a dipstick, or by determining the weight of
multiple days, or on multiple days under similar weather
fuel added to the tank.
conditions, or collecting temperature data for subsequent
6.4 Subject Equipment Selection—The equipment selected
analysis or correction during data analysis.
should be both fit for use (that is, representative of the type to
6.3.4 Oil Temperature—Oil temperature can have a signifi-
which the testing will be applied) and having all critical parts
cant influence on fluid performance and, therefore, should be
maintained in good working order.
monitored to account for its influence on efficiency. Oil
temperatures shall be measured as accurately as possible both 6.4.1 Breaking in of Equipment—To reduce mechanical
in the reservoir and at the pump. variability in new equipment, it is recommended that appro-
6.3.5 Oil Viscosity—Oil viscosity can have a significant priate equipment break-in procedures shall be followed until
influence on fluid efficiency and, therefore, should be moni- stable conditions are obtained.
tored from start to end of test to account for its influence on
6.5 Equipment Selection/Matching—Efficiency tests may be
efficiency.
run in a single hydraulic system or in matched hydraulic
6.3.6 Oil Pressure—Oil pressure has a strong influence on
systems of identical design that have been constructed using
hydraulic pump efficiency. It is important to ensure that the
components of the same make and model. In either case, in the
equipment is operating at comparable pressures during identi-
test plan, any variations in the operating conditions or differ-
cal test operations between oils under test. If pressure changes
ences in the relative efficiency of the different hydraulic units
as a result of factors other than the work load (that is, leakage,
need to be addressed. For example, data runs in matched
pump wear) occur, the results will not be valid.
hydraulic systems may need to be alternated to ensure consis-
6.3.7 Operator Differences—It is usually preferable in mo-
tent results as described in 6.3.1.
bile equipment to test reference and candidate oils using the
same operator. When not possible, procedures should be
6.6 Data Collection Equipment Selection—Instrumentation
included to minimize the effects of any differences, for for measuring rotational frequency, flow rate, pressure,
example, account for differences in DOE—randomized testing temperature, and torque are routinely required in hydraulic
and machine evaluation. efficiency tests. It is essential to ensure that the sensitivity and
6.3.8 Operating Conditions (Speed, Load, Duty Cycle)— precision of measurements are sufficient to detect performance
The test procedure should define as specifically as practical differences, if they exist. Table 1 lists the typical systematic
such variables as speed of operation, sequence of steps, and meas
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