1、Designation: D7945 14D7945 15Standard 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
2、adoption 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. Scope Scope*1.1 This test method covers the measurement of dynamic viscosity
3、and density for the purpose of derivation of kinematicviscosity of petroleum liquids, both transparent and opaque. The kinematic viscosity, , in this test method is derived by dividingthe dynamic viscosity, , by the density, , obtained at the same test temperature.1.2 The result obtained from this t
4、est method is dependent upon the behavior of the sample and is intended for application toliquids for which primarily the shear stress and shear rate are proportional (Newtonian flow behavior).1.3 The range of kinematic viscosity covered by this test method is from 0.5 mm2/s to 1000 mm2/s in the tem
5、perature rangebetween 40 C to 120 C; however the precision has been determined only for fuels and oils in the range of 2.06 mm2/s to 476mm2/s at 40 C and 1.09 to 107 mm2/s at 100 C (as stated in Section 12 on Precision and Bias). The precision has only beendetermined for those materials, viscosity r
6、anges, and temperatures as indicated in Section 12 on Precision and Bias. The testmethod can be applied to a wider range of materials, viscosity, and temperature. For materials not listed in Section 12 on Precisionand Bias, the precision and bias may not be applicable.1.4 The values stated in SI uni
7、ts 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 responsibilityof the user of this standard to establish appropriate safety and health pr
8、actices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)D2162 Practice for Basic Calibration of Master Viscometers and Vis
9、cosity Oil StandardsD6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and LubricantsD6708 Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purportto Measure the Same Property of a Material
10、2.2 ISO Standards:3ISO 5725 Accuracy (Trueness and Precision) of Measurement Methods and ResultsISO/IEC 17025 General Requirements for the Competence of Testing and Calibration Laboratories3. Terminology3.1 Definitions:3.1.1 density (), nmass per unit volume.3.1.2 dynamic viscosity (), nthe ratio be
11、tween the applied shear stress and rate of shear of a liquid.3.1.2.1 Discussion1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.07 on Flow Properties.Current edition approved Dec.
12、 15, 2014July 1, 2015. Published March 2015July 2015. Originally published in 2014. Last previous edition approved in 2014 as D7945 14.DOI: 10.1520/D7945-14.10.1520/D7945-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For A
13、nnual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only
14、 to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versio
15、nof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1It is sometimes called the coefficient of
16、 dynamic viscosity or, simply, viscosity. Thus, dynamic viscosity is a measure of theresistance to flow or to deformation of a liquid under external shear forces.3.1.2.2 DiscussionThe term dynamic viscosity can also be used in a different context to denote a frequency-dependent quantity in which she
17、ar stressand shear rate have a sinusoidal time dependence.3.1.3 kinematic viscosity (), nthe ratio of the dynamic viscosity () to the density () of a liquid.3.1.3.1 DiscussionFor gravity flow under a given hydrostatic head, the pressure head of a liquid is proportional to its density (). Therefore t
18、hekinematic viscosity () is a measure of the resistance to 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 with opt
19、ical sensors and an oscillating U-tube densitometer. The dynamicviscosity is determined from the flow time of the test specimen along the capillary under a constant pressure of compressed airin conjunction with calculations. The density is determined by the oscillation frequency of the U-tube in con
20、junction withcalculations. The kinematic viscosity is calculated by dividing the dynamic viscosity by the density.5. Significance and Use5.1 Many petroleum products are used as lubricants and the correct operation of the equipment depends upon the appropriateviscosity of the liquid being used. In ad
21、dition, the viscosity of many petroleum fuels is important for the estimation of optimumstorage, handling, and operational conditions. Thus, the accurate determination of viscosity is essential to many productspecifications.5.2 Density is a fundamental physical property that can be used in conjuncti
22、on with other properties to characterize both thelight and heavy fractions of petroleum and petroleum products and in this test method is used for the calculation from dynamicto kinematic viscosity.6. Apparatus6.1 Constant Pressure Viscometer:4,56.1.1 Viscosity MeasurementThe Constant Pressure visco
23、meter uses the Hagen-Poiseuille principle of capillary flow todetermine the viscosity.Alength of capillary tube is enclosed horizontally in a thermal block maintained at a constant temperatureby thermoelectric coolers/heaters. The test specimen is driven to flow along the tube by a constant and regu
24、lated pressure ofcompressed air. The transit time of the test sample as it flows past an array of optical detectors is measured. (See Fig. 1.) Thedynamic viscosity is proportional to the measured transit time.6.1.1.1 Pressure ControlApressure generating and regulating device able to maintain an air
25、pressure between 6.89 kPa to 68.9kPa (1 psi to 10 psi) used to drive a test specimen to flow along a capillary tube.6.1.2 Density MeasurementDensity is measured by a suitable method so to achieve the precision in kinematic viscosity asstated in the tables in Section 12. A U-shaped oscillating sample
26、 tube with a system for electronic excitation and frequencycounting as described in the manufacturers instructions is suitable. However, for this test method, the purpose of the density resultis for the calculation from dynamic to kinematic viscosity.6.1.3 Temperature ControlA thermal block surround
27、s the viscosity measuring cell so that both are at the same temperature.A thermoelectric heating and cooling system (see Fig. 1) ensures temperature stability of the block to be within 60.01 C fromthe set temperature.6.2 Autosampler, for use in sample introduction process. The autosampler shall be d
28、esigned to ensure the integrity of the testspecimen prior to and during the analysis and be equipped to transfer a representative volume of test specimen into the measuringcells. The autosampler shall transfer the test specimen from the sample vial to the measuring cells of the apparatus withoutinte
29、rfering with the integrity of the test specimen. The autosampler may have heating capability as a means to lower the viscosityof the sample for filling the measuring cells.4 The Constant Pressure viscometer is covered by a patent. Interested parties are invited to submit information regarding the id
30、entification of an alternative to this patenteditem to the ASTM International headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.5 The sole source of supply of the apparatus known to the committee at this time is P
31、hasePSL, 11168 Hammersmith Gate, Richmond, BC Canada. If you are aware ofalternative suppliers, please provide this information to ASTM International headquarters. Your comments will receive careful consideration at a meeting of the responsibletechnical committee,1 which you may attend.D7945 1526.3
32、Screen, with an aperture of 75 m, to remove particles from 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 light middle distillate test specimen, the use of the same or simila
33、r middledistillates as solvent is suitable. If the solvent dries up without residues in an applicable time frame, the use of a separate dryingsolvent is not required.7.1.2 For more viscous test specimen, an aromatic solvent such as toluene is suitable.7.2 Drying Solvent, a volatile solvent miscible
34、with the sample 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 dew point temperature of the ambient air, the use of an appropriate desiccator isrecommended.8. Sampling, Test Specime
35、ns, and Test Units8.1 Sampling is defined as all the steps required to obtain an aliquot, and to place the sample into the laboratory test container.The laboratory test container shall be of sufficient volume to mix the sample and obtain a homogeneous sample for analysis.8.2 Test SpecimenA volume of
36、 sample obtained from the laboratory sample and delivered to the measuring cells. The testspecimen is obtained as follows:8.2.1 Mix the sample, if required, to homogenize at room temperature into an open sample vial. If loss of volatile material canoccur in an open container, then mixing in closed c
37、ontainers, or at sub-ambient temperatures is recommended.8.2.2 Deliver the test specimen from a properly mixed laboratory sample to the measuring cells using an autosampler. For waxyor other samples with a high pour point, before delivering the test specimen, heat the laboratory sample to the desire
38、d testtemperature, which has to be high enough to dissolve the wax crystals.9. Calibration and Verification9.1 Use only a calibrated apparatus as described in section 6.1.1 and as shown in Fig. 1. The calibration shall be checked asdefined by the lab QA procedures using certified reference standards
39、 as described in 9.2. The recommended interval for viscosityand density calibration is once a year as a minimum or when lab QA procedures dictate. For the calibration procedure, follow theinstructions of the manufacturer of the apparatus.9.2 Certified Viscosity and Density Reference StandardsThese a
40、re for use as confirmatory checks on the procedure in thelaboratory. Certified viscosity and density reference standards shall be certified by a laboratory, which has shown to meet therequirements of ISO/IEC 17025 or a corresponding national standard by independent assessment. Viscosity standards sh
41、all betraceable to master viscometer procedures described in Test Method D2162. Density standards shall have a certified uncertaintyof the density values of 0.0001 g/cm3. The uncertainty of the reference standards shall be stated for each certified value (k = 2;95% confidence level). See ISO 5725.9.
42、2.1 Use certified reference standards appropriate to the desired measuring temperatures of viscosity and density measurementsfor both calibration and verification.FIG. 1 Viscosity BlockD7945 15310. Procedure10.1 Standard Procedure Using an Autosampler:10.1.1 Set the internal temperature control to t
43、he desired measuring temperature.10.1.2 Set the determinability limits to the values stated in Table 1 for the specific product and test temperature.10.1.2.1 For products not listed in the precision section, it is the responsibility of the user of this test method to establishreasonable determinabil
44、ity by a series of tests.10.1.3 Configure the cleaning and drying routines for the autosampler using sample solvent (see 7.1), drying solvent (see 7.2)and drying air (see 7.3) for sufficient cleaning efficiency of the product being tested.NOTE 2For specific information on proper configuration, follo
45、w the manufacturers instructions.10.1.4 Transfer a minimum of 25 mL of the test specimen into a sample vial. Cap or cover the vial as necessary.10.1.5 Load sample vial(s) onto vial tray or holder and analyze the test specimens.10.1.6 Rerun samples which exceed the determinability criteria establishe
46、d for the sample type being analyzed. (See Table 1.)10.1.6.1 If the two determined values of kinematic viscosity calculated from the flow time measurements exceed the stateddeterminability figure (see Table 1) for the product, repeat the measurements of flow times until the calculated kinematic visc
47、ositydeterminations agree with the stated determinability.NOTE 3When a sample is run or when the procedure is repeated, the dynamic viscosity and density are determined in calculating the kinematicviscosity.10.1.7 Press the “Run” or “Start” key. The apparatus measures the transit time of the test sp
48、ecimen through the capillary tubeas per 6.1.1 (and Fig. 1) and thereby calculates dynamic viscosity. The density of the test specimen is measured per 6.1.2, and thekinematic viscosity is calculated by dividing the dynamic viscosity by the density.11. Report of Results11.1 Report the result, expresse
49、d as kinematic viscosity in mm2/s to four significant figures, stating the temperature of the test.12. Precision and Bias12.1 Determinability, (d)Quantitative measure of the variability associated with the same operator in a given laboratory,obtaining successive determined values using the same apparatus for a series of operations leading to a single result. It is definedas that difference between two such single determined values as would be exceeded in the long run, in only one case in 20, in thenormal and correct operation of the test metho
