ASTM D8185-2018 5625 Standard Guide for In-Service Lubricant Viscosity Measurement.pdf

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1、Designation: D8185 18Standard Guide forIn-Service Lubricant Viscosity Measurement1This standard is issued under the fixed designation D8185; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in par

2、entheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 Significance and Determination of ViscosityThe pur-pose of this guide is to provide sufficient knowledge for aperson with some technical background

3、in lubrication orcondition monitoring from which they can determine the bestchoice for measuring viscosity of an in-service oil. Suchinformation from this guide should enable the user to engage inproductive discussions with colleagues, service providers,managers, and service personnel about obtainin

4、g and usinginformation on and from viscosity. There are a number ofdifferent approaches to viscometric measurement, and thisguide is intended to be a helpful resource in selecting the mostappropriate viscometric approach to gain information for thein-service fluid.1.2 The values stated in either SI

5、units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does

6、 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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This internationa

7、l standard was 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) Committe

8、e.2. Referenced Documents2.1 ASTM Standards:2D445 Test Method for Kinematic Viscosity of Transparentand Opaque Liquids (and Calculation of Dynamic Viscos-ity)D446 Specifications and Operating Instructions for GlassCapillary Kinematic ViscometersD2983 Test Method for Low-Temperature Viscosity of Au-t

9、omatic Transmission Fluids, Hydraulic Fluids, and Lubri-cants using a Rotational ViscometerD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4378 Practice for In-Service Monitoring of Mineral Tur-bine Oils for Steam, Gas, and Combined Cycle TurbinesD4683 Test Method for Measuring

10、 Viscosity of New andUsed Engine Oils at High Shear Rate and High Tempera-ture by Tapered Bearing Simulator Viscometer at 150 CD5133 Test Method for Low Temperature, Low Shear Rate,Viscosity/Temperature Dependence of Lubricating OilsUsing a Temperature-Scanning TechniqueD5293 Test Method for Apparen

11、t Viscosity of Engine Oilsand Base Stocks Between 10 C and 35 C UsingCold-Cranking SimulatorD5478 Test Methods for Viscosity of Materials by a FallingNeedle ViscometerD6224 Practice for In-Service Monitoring of Lubricating Oilfor Auxiliary Power Plant EquipmentD6299 Practice for Applying Statistical

12、 Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6304 Test Method for Determination of Water in Petro-leum Products, Lubricating Oils, and Additives by Cou-lometric Karl Fischer TitrationD6616 Test Method for Measuring Viscosity at High ShearRate

13、 by Tapered Bearing Simulator Viscometer at 100 CD6896 Test Method for Determination of Yield Stress andApparent Viscosity of Used Engine Oils at Low Tempera-tureD7042 Test Method for Dynamic Viscosity and Density ofLiquids by Stabinger Viscometer (and the Calculation ofKinematic Viscosity)D7110 Tes

14、t Method for Determining the Viscosity-Temperature Relationship of Used and Soot-ContainingEngine Oils at Low TemperaturesD7279 Test Method for Kinematic Viscosity of Transparentand Opaque Liquids by Automated Houillon Viscometer1This guide is under the jurisdiction of ASTM Committee D02 on Petroleu

15、mProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.96 on In-Service Lubricant Testing and Condition Monitoring Services.Current edition approved April 1, 2018. Published June 2018. DOI: 10.1520/D8185-18.2For referenced ASTM standards, visit the ASTM website

16、, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesTh

17、is international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (

18、TBT) Committee.1D7483 Test Method for Determination of Dynamic Viscosityand Derived Kinematic Viscosity of Liquids by Oscillat-ing Piston ViscometerD8092 Test Method for Field Determination of KinematicViscosity Using a Microchannel Viscometer2.2 SAE AIR Standard:3SAE AIR 5704 Field Viscosity Test f

19、or Thickened AircraftAnti-icing Fluids3. Definitions and Terms3.1 What is Viscosity?3.1.1 Viscosity is commonly recognized as the ease ordifficulty with which a fluid flowsthat is, its fluidity. Often itis very evident that temperature has a strong effect onfluidityviscosity always increases with de

20、creasing tempera-ture and vice versa.3.1.2 Afluids viscosity arises from the degree of its internalmolecular resistance to motion and a fluid flows only undersufficient force whether that force is gravity or some othersource. Stirring, pumping, causing fluid to flow in a pipe orlubricating a machine

21、 are all examples of shearapplying aforce to cause a fluid to move. For a simple example, considerfilling a glass of water and a separate glass full of thick usedoil, and stir each glassful at the same velocity (shear rate) withan identical spoon held in the same manner. The thicker usedoil will req

22、uire more force to move the spoon than the water,which is consistent with the used oil having a higher viscositythan the water.3.1.3 Isaac Newton defined viscosity originally as the ratioof the force moving the fluid over the rate at which the fluidmoves in response to that force. Fig. 1 helps to vi

23、sualize thisrelationship. The edges of the two plates are shown with fluidbetween. As predicted from Newtons law regarding viscousflow, when the upper plate is moved under a steady force overthe stationary bottom plate, this produces a linear sheargradient through the fluid as shown. Depending on th

24、e viscos-ity of the fluid between the plates, the ratio of the force per area(technically named shear-stress and indicated in Eq 1 by )causing motion of the upper plate at the shear gradient (termedshear rate and indicated by u/y) is given by Newtons law as: 5 u/y (1)3.1.4 Fig. 1 is, of course, a ve

25、ry simple example of fluidflow to clearly show the relationship in Eq 1. However, fluidflow can and does take many much more complex patterns offlow in the process of lubrication and hydraulic service. All ofthese patterns are expressed by Eq 1 if the fluid is Newtonianin behavior. However, many flu

26、ids and lubricants have flowpatterns called “non-Newtonian” and these important lubri-cants will be discussed further on in this guide.3.2 Two Frequently Used Forms of Viscosity Measurementthat Produce Different Values:3.2.1 In the early years of measuring the viscosity oflubricants, most viscometri

27、c measurements of fluids were doneusing glass capillary viscometers, and these are still usedwidely today. However, in the mid-1930s, rotational viscom-etry was commercially introduced and has since becomewidely used, particularly in high shear rate viscometry, whichwas introduced particularly for v

28、iscometric information onnon-Newtonian oils.3.2.2 However, regarding information on Newtonian oils(which are non-shear rate susceptible), capillary and rotationalviscometersat the same temperature, produce different vis-cometric values for a very simple reason. The reason is thatgravimetric viscomet

29、ry is also a function of the density of thefluid that causes the fluid to flow through the capillary. Thus,the rate at which the fluid flows through the capillary is notonly dependent on a fluids viscosity but also on its density.This form of viscometry has been termed “kinematic viscos-ity.” It was

30、 formerly measured and reported in units ofcentiStokes, cSt. This unit became obsolete in 1976 whenworldwide System International, SI, unit of mm2/s wasintroduced, (for information = 1.0 cSt = 1.0 mm2/s).3.2.3 True viscosity is called “dynamic viscosity” and wasformerly measured in the units of cent

31、ipoise, cP. This unitbecame obsolete in 1976 when the worldwide SystemInternational, SI, the unit of mPas was introduced, (forinformation 1.0 cP = 1.0 mPas).3.2.4 With Newtonian fluids, the two viscosity values dif-fered from one another as shown by Eq 2 in which is thekinematic viscosity, is the tr

32、ue, dynamic viscosity and is thefluids density at the temperature of measurement. 5 (2)Both gravimetric capillary and rotational approaches tomeasuring viscosity have remained popular and, over time,other viscometric instruments have become available.3.2.5 However, when selecting a viscosity-measuri

33、ng tech-nique for an in-service fluid or lubricant, it is criticallyimportant to clearly understand which unit of measurement haspreviously been used to characterize its viscositythat is,whether it is dynamic or kinematic viscosity. Conversion bydensity according to Eq 2 above may be required to ach

34、ieve thedesired unit of measurement. To repeat, viscosity data must bein identical units before comparison, otherwise incorrect con-clusions and false expectations of responses to conditions mayresult in poor choice of lubricants with a waste of time, effort,and resources or may even result in choic

35、es harmful to thedevice using the fluid or those depending on it.3.2.6 However, there is another very important factor in themeasurement of viscosity, and that is whether the fluid isNewtonian or non-Newtonian and that subject is opened in thefollowing section.3Available from SAE International (SAE)

36、, 400 Commonwealth Dr., Warrendale,PA 15096, http:/www.sae.org.FIG. 1 Depiction of Velocity Gradient in a Flowing FluidD8185 1823.3 Newtonian and Non-Newtonian Viscosity and Its Mea-surement:3.3.1 As noted earlier, Newtons definition of viscosity wasgiven in Eq 1, in which the ratio of shear stress

37、to shear rate isconstant for a fluid. Many simple fluids such as mineral oils areNewtonian. However, with some more complex fluids or whencertain additives are dissolved in some Newtonian fluids, theratio of shear stress to shear rate is not constant and these fluidsare called non-Newtonian. Today,

38、many lubricating oils arenon-Newtonian in behavior, and this fact also can affect theirability to lubricate or the energy required to overcome viscousresistance to flow.3.3.2 Non-Newtonian flow may take many forms in com-parison to Newtonian flow, two of which are shown in Fig. 2compared to Newtonia

39、n flow. Shear-thickening by lubricants israrely shown, however, shear-thinning is very commonlyencountered especially in lubricants. This shear-thinning isoften called “temporary viscosity loss” or TVL, since onlowering shear rate, the viscosity “lost” returns. The shear ratesproducing TVL are in th

40、e millions of units (called “reciprocalseconds,” denoted frequently by 1/s or s1). Such high valuesof shear rate are the normal operating level for most lubricationof automotive engines and other machinery. Temporary viscos-ity loss may reach levels of 30 % or more depending on thelubricant formulat

41、ion.3.3.3 The base mineral oils used to manufacture lubricantsare essentially Newtonian. For many years, one of the impor-tant additives used to formulate lubricants have been so-called“viscosity index (VI) modifiers.” These additives are com-posed of polymeric molecules which are dissolved in relat

42、ivelysmall amounts in the mineral oil base stock to impart desirableviscometric properties at both low and operating temperaturesat low shear rates.3.3.4 Conventional wisdom has held that on dissolution, thevolume of these VI modifiers increases greatly and thus impartan accompanying large viscosity

43、 increase to the base oil. Thepolymer volume increases when it is dissolved and is at highertemperature, thus giving a greater increase in viscosity than atlower temperature, but more recent investigations suggest thatthis phenomenon may occur only with certain polymericstructures, and that for diff

44、erent structures, there is a differentmechanism. Using much lower viscosity base oils, this resultsin formulations that at low shear rates have viscosities similarto those of non-polymer containing lubricants at operatingtemperatures. However, as noted above, much of this viscosityincrease is subjec

45、t to TVL.3.3.5 Unfortunately, there is another factor to be considered.At the shear rates and other, non-viscous forces applied inlubrication, the larger of these polymeric additives are vulner-able to mechanical rupture. This causes a significant andunrecoverable loss of lubricant viscosity, a so-c

46、alled “perma-nent viscosity loss” or PVL, depending on how vulnerable thedissolved macromolecules are to the forces and conditions towhich they are exposed during use. PVL may reach 20 % ormore during use of the lubricant.4. Measuring Viscosity4.1 Some viscosity measurement techniques are performeda

47、t specific shear rates and temperature conditions and aredesigned to simulate the conditions of the device beinglubricated, for example, the operating conditions of the lubri-cant serving an automotive engine. For the automotive engine,Test Method D5293, Test Method D4683, and Test MethodD6616 are e

48、xamples of viscosity measurement techniques thatfix shear rates, shear-stresses and temperatures to obtain theresultant viscosity.4.2 Measurement Consistency:4.2.1 The precision of the measurement method should bewell within that required for the changes that can occur withuse of the lubricant, othe

49、rwise inadequate information maygenerate needless or erroneous time, effort, and expensiveactions because of inadequate information from the viscomet-ric test method chosen. Thus, before choosing a viscometrictest, it is wise to review the repeatability, r, and thereproducibility, R, of viscosity measurement the particularviscometric method can provide.4.2.2 As well, programs such as the ASTM ProficiencyTesting Programs (PTP) for Petroleum Products and Lubricantscan provide valuable insights into a particular viscometricmethod, such as how we