1、Designation: D7945 14Standard Test Method forDetermination of Dynamic Viscosity and Derived KinematicViscosity of Liquids by Constant Pressure Viscometer1This standard is issued under the fixed designation D7945; the number immediately following the designation indicates the year oforiginal adoption
2、 or, in the case of revision, 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. Scope1.1 This test method covers the measurement of dynamicviscosity and density for
3、the purpose of derivation of kinematicviscosity of petroleum liquids, both transparent and opaque.The kinematic viscosity, , in this test method is derived bydividing the dynamic viscosity, , by the density, , obtained atthe same test temperature.1.2 The result obtained from this test method is depe
4、ndentupon the behavior of the sample and is intended for applicationto liquids for which primarily the shear stress and shear rate areproportional (Newtonian flow behavior).1.3 The range of kinematic viscosity covered by this testmethod is from 0.5 mm2/s to 1000 mm2/s in the temperaturerange between
5、 40 C to 120 C; however the precision hasbeen determined only for fuels and oils in the range of 2.06mm2/s to 476 mm2/s at 40 C and 1.09 to 107 mm2/s at 100 C(as stated in Section 12 on Precision and Bias). The precisionhas only been determined for those materials, viscosity ranges,and temperatures
6、as indicated in Section 12 on Precision andBias. The test method can be applied to a wider range ofmaterials, viscosity, and temperature. For materials not listed inSection 12 on Precision and Bias, the precision and bias maynot be applicable.1.4 The values stated in SI units are to be regarded asst
7、andard. No other units of measurement are included in thisstandard.1.5 This standard does 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 ap
8、plica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D445 Test Method for Kinematic Viscosity of Transparentand Opaque Liquids (and Calculation of Dynamic Viscos-ity)D2162 Practice for Basic Calibration of Master Viscometersand Viscosity Oil StandardsD6300 P
9、ractice for Determination of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsD6708 Practice for Statistical Assessment and Improvementof Expected Agreement Between Two Test Methods thatPurport to Measure the Same Property of a Material2.2 ISO Standards:3ISO 5725 Ac
10、curacy (Trueness and Precision) of Measure-ment Methods and ResultsISO/IEC 17025 General Requirements for the Competenceof Testing and Calibration Laboratories3. Terminology3.1 Definitions:3.1.1 density (), nmass per unit volume.3.1.2 dynamic viscosity (), nthe ratio between the appliedshear stress
11、and rate of shear of a liquid.3.1.2.1 DiscussionIt is sometimes called the coefficient ofdynamic viscosity or, simply, viscosity. Thus, dynamic viscos-ity is a measure of the resistance to flow or to deformation ofa liquid under external shear forces.3.1.2.2 DiscussionThe term dynamic viscosity can
12、also beused in a different context to denote a frequency-dependentquantity in which shear stress and shear rate have a sinusoidaltime dependence.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSub
13、committee D02.07 on Flow Properties.Current edition approved Dec. 15, 2014. Published March 2015. DOI: 10.1520/D7945-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer
14、 to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1
15、3.1.3 kinematic viscosity (), nthe ratio of the dynamicviscosity () to the density () of a liquid.3.1.3.1 DiscussionFor gravity flow under a given hydro-static head, the pressure head of a liquid is proportional to itsdensity (). Therefore the kinematic viscosity () is a measureof the resistance to
16、flow of a liquid under gravity.4. Summary of Test Method4.1 A test specimen is introduced into the measuring cells,which are controlled at a specified and known temperature. Themeasuring cells consist of a horizontal capillary tube withoptical sensors and an oscillating U-tube densitometer. Thedynam
17、ic viscosity is determined from the flow time of the testspecimen along the capillary under a constant pressure ofcompressed air in conjunction with calculations. The density isdetermined by the oscillation frequency of the U-tube inconjunction with calculations. The kinematic viscosity iscalculated
18、 by dividing the dynamic viscosity by the density.5. Significance and Use5.1 Many petroleum products are used as lubricants and thecorrect operation of the equipment depends upon the appropri-ate viscosity of the liquid being used. In addition, the viscosityof many petroleum fuels is important for t
19、he estimation ofoptimum storage, handling, and operational conditions. Thus,the accurate determination of viscosity is essential to manyproduct specifications.5.2 Density is a fundamental physical property that can beused in conjunction with other properties to characterize boththe light and heavy f
20、ractions of petroleum and petroleumproducts and in this test method is used for the calculation fromdynamic to kinematic viscosity.6. Apparatus6.1 Constant Pressure Viscometer:4,56.1.1 Viscosity MeasurementThe Constant Pressure vis-cometer uses the Hagen-Poiseuille principle of capillary flowto dete
21、rmine the viscosity. A length of capillary tube isenclosed horizontally in a thermal block maintained at aconstant temperature by thermoelectric coolers/heaters. Thetest specimen is driven to flow along the tube by a constant andregulated pressure of compressed air. The transit time of thetest sampl
22、e as it flows past an array of optical detectors ismeasured. (See Fig. 1.) The dynamic viscosity is proportionalto the measured transit time.6.1.2 Density MeasurementDensity is measured by a suit-able method so to achieve the precision in kinematic viscosityas stated in the tables in Section 12. A U
23、-shaped oscillatingsample tube with a system for electronic excitation andfrequency counting as described in the manufacturers instruc-tions is suitable. However, for this test method, the purpose ofthe density result is for the calculation from dynamic tokinematic viscosity.6.1.3 Temperature Contro
24、lA thermal block surrounds theviscosity measuring cell so that both are at the same tempera-ture. A thermoelectric heating and cooling system (see Fig. 1)4The Constant Pressure viscometer is covered by a patent. Interested parties areinvited to submit information regarding the identification of an a
25、lternative to thispatented item to the ASTM International headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee, whichyou may attend.5The sole source of supply of the apparatus known to the committee at this timeis PhasePSL, 11168 Hammersmi
26、th Gate, Richmond, BC Canada. If you are awareof alternative suppliers, please provide this information to ASTM Internationalheadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.FIG. 1 Viscosity BlockD7945 142ensures
27、temperature stability of the block to be within60.01 C from the set temperature.6.2 Autosampler, for use in sample introduction process.The autosampler shall be designed to ensure the integrity of thetest specimen prior to and during the analysis and be equippedto transfer a representative volume of
28、 test specimen into themeasuring cells. The autosampler shall transfer the test speci-men from the sample vial to the measuring cells of theapparatus without interfering with the integrity of the testspecimen. The autosampler may have heating capability as ameans to lower the viscosity of the sample
29、 for filling themeasuring cells.6.3 Screen, with an aperture of 75 m, to remove particlesfrom samples that may contain them (see 8.2).7. Reagents and Materials7.1 Sample Solvent, completely miscible with the sample.7.1.1 For samples that are mutually soluble such as lightmiddle distillate test speci
30、men, the use of the same or similarmiddle distillates as solvent is suitable. If the solvent dries upwithout residues in an applicable time frame, the use of aseparate drying solvent is not required.7.1.2 For more viscous test specimen, an aromatic solventsuch as toluene is suitable.7.2 Drying Solve
31、nt, a volatile solvent miscible with thesample solvent (see 7.1).7.2.1 n-Pentane is suitable.7.3 Dry Air, for blowing and drying of the measuring cells.NOTE 1If the measuring cell temperature is below or near the dewpoint temperature of the ambient air, the use of an appropriate desiccatoris recomme
32、nded.8. Sampling, Test Specimens, and Test Units8.1 Sampling is defined as all the steps required to obtain analiquot, and to place the sample into the laboratory testcontainer. The laboratory test container shall be of sufficientvolume to mix the sample and obtain a homogeneous samplefor analysis.8
33、.2 Test SpecimenA volume of sample obtained from thelaboratory sample and delivered to the measuring cells. Thetest specimen is obtained as follows:8.2.1 Mix the sample, if required, to homogenize at roomtemperature into an open sample vial. If loss of volatilematerial can occur in an open container
34、, then mixing in closedcontainers, or at sub-ambient temperatures is recommended.8.2.2 Deliver the test specimen from a properly mixedlaboratory sample to the measuring cells using an autosampler.For waxy or other samples with a high pour point, beforedelivering the test specimen, heat the laborator
35、y sample to thedesired test temperature, which has to be high enough todissolve the wax crystals.9. Calibration and Verification9.1 Use only a calibrated apparatus as described in section6.1.1 and as shown in Fig. 1. The calibration shall be checkedas defined by the lab QA procedures using certified
36、 referencestandards as described in 9.2. The recommended interval forviscosity and density calibration is once a year as a minimumor when lab QA procedures dictate. For the calibrationprocedure, follow the instructions of the manufacturer of theapparatus.9.2 Certified Viscosity and Density Reference
37、 StandardsThese are for use as confirmatory checks on the procedure inthe laboratory. Certified viscosity and density reference stan-dards shall be certified by a laboratory, which has shown tomeet the requirements of ISO/IEC 17025 or a correspondingnational standard by independent assessment. Visco
38、sity stan-dards shall be traceable to master viscometer proceduresdescribed in Test Method D2162. Density standards shall havea certified uncertainty of the density values of 0.0001 g/cm3.The uncertainty of the reference standards shall be stated foreach certified value (k = 2; 95% confidence level)
39、. See ISO5725.10. Procedure10.1 Standard Procedure Using an Autosampler:10.1.1 Set the internal temperature control to the desiredmeasuring temperature.10.1.2 Set the determinability limits to the values stated inTable 1 for the specific product and test temperature.10.1.2.1 For products not listed
40、in the precision section, it isthe responsibility of the user of this test method to establishreasonable determinability by a series of tests.10.1.3 Configure the cleaning and drying routines for theautosampler using sample solvent (see 7.1), drying solvent (see7.2) and drying air (see 7.3) for suff
41、icient cleaning efficiency ofthe product being tested.NOTE 2For specific information on proper configuration, follow themanufacturers instructions.10.1.4 Transfer a minimum of 25 mL of the test specimeninto a sample vial. Cap or cover the vial as necessary.10.1.5 Load sample vial(s) onto vial tray o
42、r holder andanalyze the test specimens.10.1.6 Rerun samples which exceed the determinabilitycriteria established for the sample type being analyzed. (SeeTable 1.)10.1.6.1 If the two determined values of kinematic viscositycalculated from the flow time measurements exceed the stateddeterminability fi
43、gure (see Table 1) for the product, repeat themeasurements of flow times until the calculated kinematicviscosity determinations agree with the stated determinability.NOTE 3When a sample is run or when the procedure is repeated, thedynamic viscosity and density are determined in calculating the kinem
44、aticviscosity.11. Report of Results11.1 Report the result, expressed as kinematic viscosity inmm2/s to four significant figures, stating the temperature of thetest.12. Precision and Bias12.1 Determinability, (d)Quantitative measure of the vari-ability associated with the same operator in a given lab
45、oratory,obtaining successive determined values using the same appa-ratus for a series of operations leading to a single result. It isD7945 143defined as that difference between two such single determinedvalues as would be exceeded in the long run, in only one casein 20, in the normal and correct ope
46、ration of the test method.(See Table 1.)NOTE 4This test method covers the measurement of dynamic viscos-ity and density for the purpose of derivation of kinematic viscosity.Therefore determinability, repeatability and reproducibility are only statedfor kinematic viscosity.12.2 Repeatability (r)The d
47、ifference between successiveresults obtained by the same operator in the same laboratorywith the same apparatus under constant operating conditions onidentical test material would, in the long run, in the normal andcorrect operation of this test method, exceed the valuesindicated only in one case in
48、 twenty. (See Table 2.)12.3 Reproducibility (R)The difference between twosingle and independent results obtained by different operatorsworking in different laboratories on nominally identical testmaterial would, in the long run, in the normal and correctoperation of this test method, exceed the valu
49、es indicated onlyin one case in twenty. (See Table 3.)NOTE 5Repeatability and reproducibility were determined based onILS study comprised of the following samples:Distillate samples included kerosene, Regular Sulphur Diesel (RSD),Ultra Low Sulphur Diesel (ULSD), Biodiesel B100 (soy derived),Biodiesel B100 (tallow derived), Biodiesel B10 blend and Biodiesel B20blend with viscosities between 2.06 and 4.50 mm2/s at 40 C.Distillate sample included Biodiesel B100 at 1.09 mm2/s at 100 C.Base Oils included synthetic and semi-synthetic base oils with
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