ASTM E126-2005a Standard Test Method for Inspection Calibration and Verification of ASTM Hydrometers《流体比重计检验和鉴定的标准试验方法》.pdf

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1、Designation: E 126 05aStandard Test Method forInspection, Calibration, and Verification of ASTMHydrometers1This standard is issued under the fixed designation E 126; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last

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

3、, 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.NOTE 1 User must determine the applicability of this

4、method forhydrometers other than ASTM hydrometers. Method studies were com-pleted for ASTM hydrometers only and the precision and bias statementswere developed using ASTM hydrometers only. References to other typesof hydrometers are for user information only.1.2 The values stated in inch-pound units

5、 are to be 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 thesa

6、fety 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.2. Referenced Documents2.1 ASTM Standards:2D 1265 Practice for Sampling L

7、iquefied Petroleum (LP)GasesManual MethodD 1298 Test Method for Density, Relative Density (SpecificGravity), or API Gravity of Crude Petroleum and LiquidPetroleum Products by Hydrometer MethodD 1657 Test Method for Density or Relative Density ofLight Hydrocarbons by Pressure HydrometerE 1 Specificat

8、ion for ASTM Liquid-in-Glass ThermometersE77 Test Method for Inspection and Verification of Ther-mometersE 100 Specification for ASTM HydrometersE 344 Terminology Relating to Thermometry and Hydrom-etryE 2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids3. Te

9、rminology3.1 Definitions:3.1.1 The definitions given in Terminology E 344 apply.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/

10、rel. density 60/60 F!# 2 131.5 (1)Values ofAPI gravity are typically expressed in degreesAPI, that is, 39.60API.3.2.2 comparator, n in this test method, a device tocontain liquid, in which the readings of the test hydrometermay be evaluated against the values observed on the referencestandard. Examp

11、les of suitable comparators are given in theAppendix.3.2.3 density, nmass of a unit volume of material.3.2.3.1 DiscussionUnits of density in hydrometers in-clude kg/l (kilograms per liter), kg/m3(kilograms per cubicmeter), and g/l (grams per liter); each typically expressed asmass per volume at a sp

12、ecified temperature, that is, kg/m3at 15C. As of this writing, only the kg/m3at 15 C scale is offeredin ASTM hydrometers (see Specification E 100).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

13、 of gas-free distilled water at thesame or different temperature. Both reference temperaturesshall be explicitly stated.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 a

14、nd Hydrometers.Current edition approved Nov. 1, 2005. Published December 2005. Originallyapproved in 1959. Last previous edition approved in 2005 as E 126 05.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of A

15、STMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.4.1 DiscussionCommon reference temperatures in-clude 60 F/60 F, 20 C/20 C, 20 C/4 C.

16、 The historic term,specific gravity, may still be found.3.2.5 specific gravity, n obsolete term, replaced by rela-tive density.3.2.6 thermo-hydrometer, nglass hydrometer having athermometer combined with a hydrometer in one instrument.3.2.7 verification, nconfirmation, by examination of evi-dence, t

17、hat the instrument fulfills specified requirements.3.2.7.1 DiscussionIn this test method, the requirementsfor the maximum scale error and dimensions for the hydrom-eters given in Specification E 100 apply.3.2.8 Other descriptions of terms relating to thermometersare included in Test Method E77.4. Si

18、gnificance and Use4.1 The purpose of this test method is to establish a commonmethod by which manufacturers and users of ASTM hydrom-eters inspect, verify, or calibrate their hydrometers.4.2 The goal is to provide a standard method that is simple,easily understood, and will produce reliable results.

19、5. Apparatus5.1 Graduated Metal Scales, of the conventional type, forchecking linear dimensions. If more convenient, metal tem-plates may be used on which lines are ruled at suitabledistances from reference points corresponding to the maximumand minimum values of the specified dimensions.5.2 Microme

20、ters, of the conventional type, for checkingdiameters.5.3 Comparators, for the calibration and verification ofhydrometers. Suitable types are described in the Appendix.5.4 Equipment, for checking the thermometer portion ofthermo-hydrometers is described in Test Method E77.5.5 Thermometer(s), for use

21、 in pressure hydrometer cylin-der comparator, ASTM 12C (-20/102 C, 0.2 divisions) orASTM 12F (-5/215 F, 0.5 divisions) found in ASTM E1 orASTM S12C (-20/102 C, 0.2 divisions) or ASTM S12F(-5/215 F, 0.5 divisions) found in Specification E 2251.6. Reference Standards6.1 Standard HydrometersStandard hy

22、drometers shallhave similar dimensions and shape to the instruments to betested, and shall have the same or smaller graduation interval.NOTE 2The relative density (specific gravity) of liquids used intesting hydrometers may be obtained by hydrostatic weighing instead ofby the use of reference standa

23、rds 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 laborato

24、ry competent to test instrumentsof such precision. The calibration report shall provide trace-ability 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 visually i

25、nspected 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. Evidence of any of theeffects warrants re-calibration.6.3.2 Experience has s

26、hown that hydrometers may showdrift with continued use. A procedure shall be in place todemonstrate continued validity of the calibration results for thestandard hydrometer. Such a procedure may include: periodicre-calibration of the standard hydrometers; measurements ofhydrometers retained by the t

27、esting laboratory for use as checkstandards; or checks of one standard hydrometer againstanother.7. Procedure7.1 Visual Inspection:7.1.1 Inspect the hydrometer carefully to be certain there areno cracks, fissures, deep scratches, rough areas, or otherobvious damage to the glass. Reject the hydromete

28、r if any ofthese defects are present.7.1.2 Inspect the hydrometer carefully for loose pieces ofballast or other foreign material within the instrument. Ifpresent, reject the instrument.7.1.3 Inspect the paper scale within the hydrometer stem.The paper scale shall be straight and without twist.7.1.4

29、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 scale; however, other schemes are permitted,such as etching a line on the glass corresponding to a

30、referenceline printed on the scale. If a permitted scale slippage indicatoris damaged, incorrectly positioned, or not present, reject theinstrument. See Specification E 100 for more details.7.2 Dimensional Inspection:7.2.1 Check the linear dimensions and diameters for com-pliance with Specification

31、E 100 requirements by comparingthe 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 equalspacing. The interval between graduations of density andrelative density (specific gr

32、avity) hydrometers is smaller nearthe bottom of the scale. The proper spacing shall be obtainedfrom the following formula:l 5 L 3 d2/d 3 d 2 d1!/d22 d1! (2)where:l = distance from the top line to any line, d, between thetop and the bottom,L = distance between the top and the bottom graduationsof the

33、 scale,d2= density value, or relative density (specific gravity), ofthe bottom line, andd1= density value, or relative density (specific gravity), ofthe top line.3Dictionary of Applied Physics, MacMillan and Co., London, Vol 3, p. 439.4“Density of Solids and Liquids,” National Institute of Standards

34、 and Technol-ogy, Circular No. 487.E 126 05a27.2.3 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 General Considerations:7.3.1 In order that readings shal

35、l be uniform and reproduc-ible, the hydrometer must be clean, dry, and at the temperatureof the liquid before immersing to take a reading. It isparticularly important that the stem be clean so that the liquidwill rise uniformly around the stem and merge into animperceptible film on the stem.7.3.2 Cl

36、eanlinessThe readiness with which proper clean-liness can be obtained depends somewhat on the character ofthe 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

37、drying immediately before each 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 testing are in common use. In one method,hydrometers

38、are dipped in a mixture 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 resi

39、dual soap film. The stems can usually be keptclean during the testing 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 hazardo

40、us. This process should onlybe carried out in a laboratory setting with appropriate equip-ment and trained personnel. Hydrometer must be dry beforebeing inserted in the acids. The steam created by a wethydrometer may splash acids on the operator.)7.3.3 Influence of TemperatureFor a hydrometer to ind

41、i-cate the density or strength of a specified liquid correctly, it isessential that the liquid be uniform throughout and at thetemperature specified on the instrument. However, in compar-ing two hydrometers having the same standard temperature andmade of the same type of glass, the temperature of th

42、e liquidneed not be considered since the correction required due tovariation from the standard temperature is the same for bothinstruments. But the temperatures of the liquid, the hydrom-eters, and the surrounding atmosphere should be nearly equalduring the comparison; otherwise, the temperature of

43、the liquidwill be changing, causing differences in density. The operatorshall allow enough time to achieve this equilibrium. To ensurehomogeneity and uniformity in the liquid, thorough mixing isrequired immediately before making observations.NOTE 3Thermometers described in 5.5, or thermometers with

44、equiva-lent maximum permissible errors, may be used, if desired.7.3.4 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 instrum

45、ent isfloating has the same effect as adding to the mass of thehydrometer, thus increasing the depth of immersion.7.3.4.1 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

46、 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 dissimilar instruments in such a liquid shallbe correcte

47、d for the effect of the surface tension.7.3.4.2 In many liquids spontaneous changes in surfacetension occur due to the formation of surface films of impuri-ties, which may come from the apparatus, the liquid, or the air.Errors from this cause may be avoided by the use of liquids notsubject to such c

48、hanges. However, if the liquid used is differentin surface tension from the specified liquid, a correction isrequired when dissimilar instruments are compared, as men-tioned above. A second method of avoiding these errors is topurify the surface of the test liquid by causing an overflow ofthe liquid

49、 before making an observation.7.3.4.3 The necessity for such special manipulation is con-fined to the reading of hydrometers in liquids that are subjectto surface contamination, such as aqueous solutions or mix-tures of acids, alkalies, salts, sugar, and weak alcoholicmixtures. Oils, alcoholic mixtures of strength above 40% byvolume, and other liquids of relatively low surface tension arenot, in general, liable to surface contamination sufficient tocause appreciable changes in hydrometer readings.NOTE 4For further discussion of surface tens