ASTM E126-2013a 6616 Standard Test Method for Inspection Calibration and Verification of ASTM Hydrometers《检验 校准和鉴定ASTM比重计的标准试验方法》.pdf

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1、Designation: E126 13aStandard Test Method forInspection, Calibration, and Verification of ASTMHydrometers1This standard is issued under the fixed designation E126; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re

2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method describes the principl

3、es, apparatus, andprocedures for the inspection, calibration, and verification ofASTM glass hydrometers. This test method is applicable toASTM hydrometers and may be used for other generalhydrometers of the constant-mass, variable-displacement type.1.2 The values stated in inch-pound units are to be

4、 regardedas the standard. The values given in parentheses are mathemati-cal conversions to SI units that are provided for informationonly and are not considered standard. The metric equivalents ofinch-pound units may be approximate.1.3 This standard does not purport to address all of thesafety conce

5、rns, 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.2. Referenced Documents2.1 ASTM Standards:2D1265 Practice for Sampling Liquefied Pe

6、troleum (LP)Gases, Manual MethodD1298 Test Method for Density, Relative Density, or APIGravity of Crude Petroleum and Liquid Petroleum Prod-ucts by Hydrometer MethodD1657 Test Method for Density or Relative Density of LightHydrocarbons by Pressure HydrometerE1 Specification for ASTM Liquid-in-Glass

7、ThermometersE77 Test Method for Inspection and Verification of Ther-mometersE100 Specification for ASTM HydrometersE344 Terminology Relating to Thermometry and Hydrom-etryE2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids3. Terminology3.1 DefinitionsThe defi

8、nitions given in Terminology E344apply.3.2 Definitions of Terms Specific to This Standard:3.2.1 API gravity, na relative index of density for petro-leum products developed by the American Petroleum Institute.API gravity is defined as:API Gravity,deg 5 141.5/rel. density 60/60 F!# 2 131.5 (1)Values o

9、f API gravity are typically expressed in degrees API,that is, 39.60 API.3.2.2 comparator, nin this test method, a glass or othertransparent cylinder to contain a liquid in which hydrometersmay be compared. Examples of suitable comparators are givenin Appendix X1.3.2.3 density, nmass of a unit volume

10、 of material.3.2.3.1 DiscussionUnits of density in hydrometers includekg/l (kilograms per liter), kg/m3(kilograms per cubic meter),and g/l (grams per liter); each typically expressed as mass pervolume at a specified temperature, that is, kg/m3at 15 C. Asof this writing, only the kg/m3at 15 C scale i

11、s offered inASTM hydrometers (see Specification E100).3.2.4 relative density (formerly specific gravity), nratio ofthe mass of a given volume of material at a stated temperatureto the mass of an equal volume of gas-free distilled water at thesame or different temperature. Both reference temperatures

12、shall be explicitly stated.3.2.4.1 DiscussionCommon reference temperatures in-clude 60 F/60 F, 20 C/20 C, 20 C/4 C. The historic term,specific gravity, may still be found.3.2.5 specific gravity, nhistoric term, replaced by relativedensity.3.2.6 thermo-hydrometer, nglass hydrometer having athermomete

13、r combined with a hydrometer in one instrument.1This test method is under the jurisdiction of ASTM Committee E20 onTemperature Measurement and is the direct responsibility of Subcommittee E20.05on Liquid-in-Glass Thermometers and Hydrometers.Current edition approved Nov. 1, 2013. Published December

14、2013. Originallyapproved in 1959. Last previous edition approved in 2013 as E126 13. DOI:10.1520/E0126-13a.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 to the stand

15、ards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.7 verification, nconfirmation, by provision of objec-tive evidence, that the instrument fulfills specified require-ments.3.2.7.1 Discuss

16、ionIn this test method, if the hydrometerbears an ASTM designation, the requirements for the maxi-mum scale error and dimensions for the hydrometers given inSpecification E100 apply.3.2.8 Other descriptions of terms relating to thermometersare included in Test Method E77. Any definitions of measure-

17、ment uncertainty used in this standard are from TerminologyE3444. Significance and Use4.1 The purpose of this test method is to establish a commonmethod by which manufacturers, calibration laboratories, andusers of hydrometers may inspect, verify, or calibrate them.4.2 The goal is to provide a stand

18、ard method that is simple,easily understood, and will produce reliable results.5. Apparatus5.1 Graduated Metal Scales, of the conventional type, forchecking linear dimensions. If more convenient, metal tem-plates on which lines are ruled at suitable distances fromreference points corresponding to th

19、e maximum and minimumvalues of the specified dimensions may be used.5.2 Micrometers, of the conventional type, for checkingdiameters.5.3 Polariscope, for viewing strain patterns in the glassdeveloped during the manufacturing of the hydrometer.5.4 Comparators, for the calibration and verification ofh

20、ydrometers. Suitable types are described in Appendix X1.5.5 Equipment, for checking the thermometer portion ofthermohydrometers as described in Test Method E77.5.6 Thermometer(s), for use in pressure hydrometer cylin-der comparator, ASTM 12C (-20/102 C, 0.2 divisions),ASTM 12F (-5/215 F, 0.5 divisio

21、ns), 136C (-20/60C, 0.2divisions), or ASTM 136F (-5/140F, 0.5 divisions) found inASTM E1 or ASTM S12C (-20/102 C, 0.2 divisions), orASTM S12F (-5/215 F, 0.5 divisions) found in SpecificationE2251.6. Reference Standards6.1 Standard HydrometersStandard hydrometers shallhave similar dimensions and shap

22、e to the instruments to becalibrated, (when possible), and shall have dimensions andshapes similar to the instruments to be calibrated.NOTE 1The relative density (specific gravity) of liquids used incalibrating hydrometers may be obtained by hydrostatic weighing insteadof by the use of reference sta

23、ndards as described above. Details of thehydrostatic weighing apparatus can be found in the Dictionary of AppliedPhysics3or Density of Solids and Liquids.46.2 Standards shall be calibrated by either a national me-trology body (such as the National Institute of Standards andTechnology) or other labor

24、atory competent to calibrate instru-ments of such precision. The calibration report shall providetraceability to a national metrology body and shall contain astatement of measurement uncertainty. It is desirable that thecorrections be stated to one-tenth of a scale division.6.3 Standards shall be vi

25、sually inspected every six monthsor prior to use, whichever is longer.6.3.1 Visual inspection shall include, but is not limited to,looking for evidence of scratches, etching, scale slippage,deposits on the glass, and discoloration. The presence of any ofthese defects is an indication that the standa

26、rd may requirere-calibration or replacement.6.3.2 Experience has shown that the indications of hydrom-eters may show drift with continued use. A procedure shall bein place to demonstrate continued validity of the calibrationresults for the standard hydrometer. Such a procedure mayinclude: periodic r

27、e-calibration of the standard hydrometers;measurements of hydrometers retained by the testing labora-tory for use as check standards; or checks of one standardhydrometer against another.7. Procedure7.1 Inspection:7.1.1 Inspect the hydrometer carefully to be certain there areno cracks, fissures, deep

28、 scratches, rough areas, or otherobvious damage to the glass. Reject the hydrometer if any ofthese defects are present.7.1.2 Using a polariscope, inspect the hydrometer for strainin the glass, especially at the stem/body junction. If the strainappears severe and will compromise the integrity of theh

29、ydrometer, reject the instrument. This is particularly impor-tant for thermohydrometers. See Test Method E77, 6.1.4 formore details.7.1.3 Inspect the hydrometer carefully for loose pieces ofballast or other foreign material within the instrument. Ifpresent, reject the instrument.7.1.4 Inspect the pa

30、per scale within the hydrometer stem.The paper scale shall be straight and without twist.7.1.5 Inspect for the presence of a scale slippage indicator.Typically, this is a thin strand of red glass, fused to the insidetop of the stem, and terminating at the first major graduation ofthe hydrometer scal

31、e; however, other schemes are permitted,such as etching a line on the glass corresponding to a referenceline printed on the scale. If a permitted scale slippage indicatoris damaged, incorrectly positioned, or not present, reject theinstrument. See Specification E100 for more details.NOTE 2Hydrometer

32、s that do not carry an ASTM designation maynot be required to have a scale slippage indicator. In such cases, acautionary note on the report would be appropriate.7.2 Dimensional Inspection:7.2.1 Check the linear dimensions and diameters for com-pliance with Specification E100 requirements by compari

33、ngthe hydrometer with the appropriate device described in 5.1and 5.2.7.2.2 Inspect the hydrometers for correctness of graduationspacing. API and Baum hydrometers are graduated with equal3Dictionary of Applied Physics, MacMillan and Co., London, Vol 3, p. 439.4“Density of Solids and Liquids,” Nationa

34、l Institute of Standards andTechnology, Circular No. 487.E126 13a2spacing. The interval between graduations of density andrelative density (specific gravity) hydrometers is smaller nearthe bottom of the scale. The proper spacing shall be obtainedfrom the following formula:l 5 L 3d2/d 3 d 2 d1!/d22 d

35、1! (2)where:l = distance from the top line to any line, d, between the topand the bottom,L = distance between the top and the bottom graduations ofthe scale,d2= density value, or relative density (specific gravity), ofthe bottom line, andd1= density value, or relative density (specific gravity), oft

36、he top line.7.2.3 Check the scale of hydrometers graduated to readpercent of alcohol by weight or by volume by comparison withthe values for master scales given in the Standard Density andVolumetric Tables.57.3 Calibration:7.3.1 General Considerations:7.3.1.1 In general, each hydrometer shall be cal

37、ibrated at aminimum of three calibration points, spaced approximatelyequally across its range, nominally high, low and mid scale.For example, a hydrometer with a range of 9 to 21 API shallbe calibrated at (approximately) 10, 15, and 20 API.NOTE 3Certain ASTM hydrometers, notably ASTM 10H and 60H(89/

38、101 API) and 101H and 310H (0.600 to 0.650 relative density and500 to 650 kg/m3, respectively) have ranges which cannot be fullycalibrated due to fluid limitations. In these cases, the hydrometers may becalibrated at two calibration points.7.3.1.2 In order that readings shall be uniform andreproduci

39、ble, the hydrometer must be clean, dry, and at thetemperature of the liquid before immersing to take a reading. Itis particularly important that the stem be clean so that the liquidwill rise uniformly around the stem and merge into animperceptible film on the stem.7.3.1.3 CleanlinessThe readiness wi

40、th which propercleanliness can be obtained depends somewhat on the characterof the liquid. Certain liquids, such as mineral oils and strongalcoholic mixtures, adhere to the stem very readily. In suchcases, wiping with a lint-free cloth moistened with acetone oralcohol and drying immediately before e

41、ach reading is usuallysufficient. On the other hand, with weak aqueous solutions ofsugar, salts, acids, and alcohol, scrupulous cleaning of the stemis required. For such liquids, two methods for preparinginstruments for calibration are in common use. In one method,hydrometers are dipped in a mixture

42、 of one part concentratedsulfuric acid and two parts fuming sulfuric acid, thoroughlyrinsed with water, and dried by wiping with a clean cloth. In theother method, hydrometers are washed with soap and water,dried, and wiped with a cloth moistened with alcohol toremove any residual soap film. The ste

43、ms can usually be keptclean during the calibration by wiping with a lint-free clothmoistened with alcohol (preferably absolute) and drying beforeeach reading. (WarningEXTREME CAUTIONThe clean-ing process using concentrated sulfuric acid and fumingsulfuric acid is extremely hazardous. This process sh

44、ould onlybe carried out in a laboratory setting with appropriate equip-ment and trained personnel. The hydrometer must be drybefore being inserted in the acids. The reaction caused byintroducing a wet hydrometer into the acids may splash acidson the operator.)7.3.1.4 Influence of TemperatureFor a hy

45、drometer to in-dicate the density of a specified liquid correctly, it is essentialthat the liquid be homogenous and uniform in temperature. Incomparing two hydrometers having the same standard tem-perature and made of the same type of glass, the temperature ofthe liquid need not be considered since

46、the correction requireddue to variation from the standard temperature is the same forboth instruments. But the temperatures of the liquid, thehydrometers, and the surrounding atmosphere shall be nearlyequal during the comparison; otherwise, the temperature of theliquid will be changing, causing diff

47、erences in density. Theoperator shall allow enough time to achieve this equilibrium.To ensure homogeneity and temperature uniformity in theliquid, thorough mixing is required immediately before makingmeasurements.NOTE 4Equipment such as thermometers described in 5.6, or alter-native thermometric dev

48、ices of equal or better accuracy, may be used, ifdesired.7.3.1.5 Influence of Surface TensionWhen a hydrometer isfloated in a liquid, a small quantity of the liquid rises about thestem to form a meniscus. This liquid adhering to the stemabove the general level of the liquid in which the instrument i

49、sfloating has the same effect as adding to the mass of thehydrometer, thus increasing the depth of immersion.7.3.1.6 Because a hydrometer will indicate differently intwo liquids having the same density but different surfacetensions, and since surface tension is a specific property ofliquids, it is necessary to specify the liquid for which ahydrometer is intended. Although hydrometers of equivalentdimensions may be compared, without error, in a liquiddiffering in surface tension from the specified liquid, the resultsof comparisons of