1、Designation: D7721 17Standard Practice forDetermining the Effect of Fluid Selection on HydraulicSystem or Component Efficiency1This standard is issued under the fixed designation D7721; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers all hydraulic fluids.1.2 This practice is applicable to both laboratory and field
3、evaluations.1.3 This practice provides guidelines for conducting hy-draulic fluid evaluations. It does not prescribe a specificefficiency test methodology.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard doe
4、s not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.6 This international standard was
5、developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced
6、 Documents2.1 ASTM Standards:2D4174 Practice for Cleaning, Flushing, and Purification ofPetroleum Fluid Hydraulic SystemsD4175 Terminology Relating to Petroleum Products, LiquidFuels, and Lubricants2.2 ISO Standards:3ISO 4391 Hydraulic fluid powerPumps, motors and inte-gral transmissionsParameter de
7、finitions and letter sym-bolsISO 4392 Hydraulic fluid powerDetermination of charac-teristics of motorsISO 4409 Hydraulic fluid powerPositive displacementpumpsMethods of testing and presenting basic steadystate performanceISO 5598 Fluid power systems determined from electric powermeter readings or ca
8、lculated from the mass of fuel consumedand the lower heating value of the fuel.3.2.6 fit for use, nproduct, system, or service that issuitable for its intended use.3.2.7 fuel rate, nthe rate at which fuel is consumed in L/h,normalized to the fuel density at 15 C.3.2.8 grade, ndesignation given a mat
9、erial by a manufac-turer so that it is always reproduced to the same specificationsestablished by standards organizations such as ASTM or ISO.3.2.9 hydraulic fluid, nliquid used in hydraulic systemsfor lubrication and transmission of power.3.2.10 hydraulic system, nfluid power system that is anarran
10、gement of interconnected components which generates,transmits, controls, and converts fluid power energy.3.2.11 motor hydromechanical effciency, nratio of theactual torque output of the motor to the theoretical torqueoutput of the motor.3.2.12 motor overall effciency, nratio of the mechanicaloutput
11、power to the power transferred from the liquid at itspassage through the motor.3.2.13 motor volumetric effciency, nratio of the theoreti-cal inlet flow rate to the effective inlet flow rate.3.2.14 outlier, nresult far enough in magnitude from otherresults to be considered not part of the set.3.2.14.
12、1 DiscussionFor purposes of this practice, classifi-cation of a result as an outlier shall be justified by statisticalcriteria in comparison with the valid data points.3.2.15 pump hydromechanical effciency, nratio of thetheoretical input torque of the pump to the actual torque inputof the pump.3.2.1
13、6 pump overall effciency, nratio of the power trans-ferred to the liquid, at its passage through the pump, to themechanical input power.3.2.17 pump volumetric effciency, nratio of the effectiveoutput flow rate to the theoretical output flow rate.3.2.18 reference oil, noil of known performance charac
14、-teristics used as a basis for comparison.3.2.18.1 DiscussionFor purposes of this practice, the ref-erence oil may be a hydraulic fluid of any suitable composition.3.2.19 test oil, nany oil subjected to evaluation in anestablished procedure.3.2.19.1 DiscussionFor purposes of this practice, the testo
15、il may be a hydraulic fluid of any suitable composition.3.3 Definitions of Terms Specific to This Standard:3.3.1 design of experiment, DOE, nstatistical arrangementin which an experimental program is to be conducted and theselection of the levels (versions) of one or more factors orfactor combinatio
16、ns to be included in the experiment.3.3.2 duty cycle, ntime interval devoted to starting,running, stopping, and idling when a device is in use and thetime spent operating at different levels of speed, displacementvolume, torque, and pressure.3.3.3 effciency improvement, na positive change in one orm
17、ore parameters measured in a system or component that maybe defined as a reduction in fuel consumption, electrical powerdraw, or temperature, an increase in work produced or flowrate, or any combination of these or other parameters.3.3.3.1 DiscussionThis improvement is expressed as apercent increase
18、 that is obtained by dividing the test oilperformance by the reference oil performance and multiplyingby 100 or, if appropriate, for example, temperature, then actualvalues can be reported.3.3.4 power factor, nin AC electrical circuits, the ratio ofactual electric power dissipated by the circuit to
19、the product ofthe root mean square values of current and voltage. In DCelectrical circuits, it is the energy consumed (watts) versus theproduct of input voltage (volts) times input current (amps).3.3.4.1 DiscussionThe power factor is the dimensionlessratio of energy used compared to the energy flowi
20、ng throughthe wires.3.3.5 system overall effciency, nin fluid power systems,the ratio of the output power of the system to the input powerof the system.3.3.5.1 DiscussionFor integral transmissions and open-loop hydraulic circuits that drive a hydraulic motor, systemoverall efficiency is the ratio of
21、 the output mechanical power atthe hydraulic motor shaft to the input mechanical power at thepump shaft. Methods ISO 4391 and ISO 4409 provide addi-tional details for determining system efficiency in circuits withboost pumps.4. Summary of Practice4.1 The purpose of this practice is to define minimum
22、technical requirements for conducting energy efficiency perfor-mance comparisons of two or more hydraulic fluids in con-trolled laboratory or field evaluations.4.2 Controls and considerations based on both technicalfactors and practical experience are included.4.3 Requirements for test planning, tes
23、ting conduct, anddata analysis and reporting are described.5. Significance and Use5.1 The purpose of a hydraulic fluid is to cool and lubricatefluid power components, as well as transmit power. Thispractice provides uniform guidelines for comparing fluids interms of their power-transmitting abilitie
24、s as reflected in theireffect on hydraulic system or component efficiency. Standardtest methods ISO 4409 and ISO 4392 provide specifications forevaluating the steady state performance of hydraulic pumpsand motors but do not address technical requirements specificto hydraulic fluid testing.5.2 Differ
25、ences in fluid performance may be relativelysmall. Consequently, it is essential that the necessary experi-mental controls are implemented to ensure consistency inoperating conditions and duty cycle when comparing theenergy efficiency of different hydraulic fluid formulations.5.3 Practical advantage
26、s of enhanced hydraulic system ef-ficiency may include increased productivity (faster machineD7721 172cycle time), reduced power consumption (electricity or fuel),and reduced environmental impact (lowered emissions).5.4 This practice implies no evaluation of hydraulic fluidquality other than its eff
27、ect on hydraulic system efficiency.6. Procedure6.1 ProtocolA successful outcome is dependent on anevaluation of goals and methods at the outset along with anassessment of potential sources of error. Such an evaluationrequires a clearly defined test protocol that shall include: (1)statistical design
28、of experiment and analysis, (2) fluid orderevaluation, (3) equipment selection, (4) analysis and mitigationof the test variables, and (5) appropriate data collectionmethods. This ensures that both the reference and test oils areevaluated in exactly the same way, thus ensuring a validcomparison is ma
29、de.6.1.1 Site Coordinator/Personnel TrainingBecause of thecomplexity of field trials, it is recommended that a designatedsite coordinator be used to ensure any questions or concernsfrom site personnel are addressed and that test protocols arebeing followed.6.2 Statistical Design of Experiment (DOE)A
30、 statisticalDOE system shall be used to account for any test variabilityand ensure any differences observed are significant to 95 %confidence limits.6.3 Test ControlThere are a number of test variables thatcan significantly influence efficiency measurements and shallbe controlled.6.3.1 Fluid OrderTo
31、 account for the potential impact ofmachine drift/bias and lubricant carryover effects, it is highlyrecommended that the efficiency of the reference fluid (A) beevaluated before and after each test fluid (B) evaluation.Alternating the reference fluid and test fluid in an ABA orABAB test sequence is
32、satisfactory. When operator or testequipment variables may have a significant impact on the testoutcome, the operators and test equipment should also bealternated in a systematic manner.6.3.2 Carryover ControlHydraulic systems may retain asignificant amount of residual fluid after they have beendrai
33、ned. This residual fluid can create cross-contamination.The level of cross-contamination between test fluids shall bekept to a minimum. In preparation for the evaluation of eachfluid, the hydraulic system should be filled, flushed, anddrained of the test fluid at least once. Practice D4174 providess
34、pecific recommendations to facilitate this process. The cross-contamination level in the test fluid ideally should not exceed10 % in field trials and 1 % in laboratory evaluations. Theamount of cross-contamination should be determined using anappropriate test method such as elemental analysis, massb
35、alance, infrared spectroscopy, or viscosity. This information isto be included with the test results.6.3.2.1 Flushing Requirements for Surface Active Fluids(for Example, Friction Modified)If any of the fluids underevaluation contains surface-active friction-reducing materials(for example, friction m
36、odifiers), then extra precautions tominimize carryover effects may be required. One of theseprecautions shall be to use a flush oil that is capable ofremoving such surface-active additives.6.3.3 Environmental Conditions (for Field Trials)It isimportant to minimize the effect of differences in enviro
37、nmen-tal conditions such as ambient temperature during the conductof a field test. This may require testing only during definedperiods of the day over multiple days, or on multiple daysunder similar weather conditions. Record ambient temperature,atmospheric pressure, and sea level at the beginning o
38、f eachtest sequence.6.3.3.1 Precipitation shall be avoided as much as possibleduring testing as it is difficult to account for variation intraction.6.3.3.2 The recommended ambient temperature for machinetesting is 15 C to 30 C.6.3.4 Oil TemperatureOil temperature can have a signifi-cant influence on
39、 fluid performance and, therefore, should bemonitored to account for its influence on efficiency. Oiltemperatures shall be measured as accurately as possible bothin the reservoir and at the pump inlet.6.3.5 Oil ViscosityOil viscosity can have a significantinfluence on fluid efficiency and, therefore
40、, should be moni-tored from start to end of test to account for its influence onefficiency.6.3.6 Oil PressureOil pressure has a strong influence onhydraulic pump efficiency. It is important to ensure that theequipment is operating at comparable pressures during identi-cal test operations between oil
41、s under test. If pressure changesas a result of factors other than the work load (that is, leakage,pump wear) occur, the results will not be valid.6.3.7 Operator DifferencesIt is usually preferable in mo-bile equipment to test reference and candidate oils using thesame operator. When not possible, p
42、rocedures should beincluded to minimize the effects of any differences, forexample, account for differences in DOErandomized testingand machine evaluation.6.3.8 Operating Conditions (Speed, Load, Duty Cycle)The test procedure should define as specifically as practicalsuch variables as speed of opera
43、tion, sequence of steps, andload. Also, the duty cycle shall be defined to hold as consis-tently as possible between the test and reference oils. Wherepossible, standard duty cycles such as found in VDI 2198should be employed.6.3.9 Fuel QualityDifferences in fuel characteristics cancontribute to cha
44、nges in efficiencies during field testing. It ispreferable to conduct field evaluations using a single batch offuel. When this is not possible, comparable fuel quality shall beincluded in the test protocol.6.3.10 Electric Power QualityIn systems drawing powerfrom a common source such as plant equipm
45、ent, changes inload separate from the test equipment can affect electricalpower quality. In systems that may be affected, comparablepower quality (for example, amps, watts, and power factor)shall be included in the test protocol.6.3.11 The recommended location for measuring electricalpower consumpti
46、on is between the variable frequency drive (orstarter in an across-the-line application) and the electric motor.6.3.12 Fuel MeasurementFuel gauges on commercial hy-draulic machines are designed to indicate when fuel replenish-ment is necessary. Consequently, fuel gauge accuracy isD7721 173insufficie
47、nt for efficiency studies. Fuel levels may be deter-mined by using an auxiliary tank and weighing the amount offuel consumed or using fuel flow sensors.6.3.12.1 In high pressure common rail diesel engines, aportion of the fuel flow is recirculated to cool the system. Thefuel consumption rate may be
48、continuously measured using thesystem depicted in Fig. 1. This system measures the fuel sentto the injection pump and isolates the unused fuel returned tothe tank.6.3.12.2 The energy content of fuel is affected by tempera-ture due to the impact of thermal expansion on density. Fuelflow sensors must
49、be able to account for changes in fueltemperature and density as well as the volume of fuel con-sumed.6.4 Subject Equipment SelectionThe equipment selectedshould be both fit for use (that is, representative of the type towhich the testing will be applied) and having all critical partsmaintained in good working order.6.4.1 Breaking-in of EquipmentTo reduce mechanicalvariability in new equipment, it is recommended that appro-priate equipment break-in procedures shall be followed untilstable conditions are obtained.6.5 Equipment S
