ASME MFC-9M-1988 Measurement of Liquid Flow in Closed Conduits by Weighing Methods (Includes Errata December 1989)《在封闭导管中用称重法测量液体流量》.pdf

1、DECEMBER 1989ERRATAtoASMEIANSI MFC-9M-1988MEASUREMENT OF LIQUID FLOW IN CLOSED CONDUITSBY WEIGHING METHODSPage 3(1) In Table 1 for Symbol la, change Quantity fromDensity of air (at 20C and 1 bar) to read:Density of air(2) Delete asterisked footnote.THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS345 E8s

2、t 47th Street, New York, N.Y. 10017 K0126EAN AMERICAN NATIONAL STANDARDMeasurement of.Liquid Flow inClosed Conduits byWeighing MethodASME/ANSI MFC-9M-1988The American Society ofm Mechanical EngineersL.-_, 345 East 47th Street, New York, N.Y. 10017-Date of Issuance: February 28, 1989This Standard wil

3、l be revised when the Society approves the issuance of a new edition.There will be no addenda or written Interpretations of the requirements of this Standardissued to this edition. ASME Is the registered trademark of The American Society of Mechanical Engineers.This code or standard was developed un

4、der procedures accredited as meeting the criteria forAmerican National Standards. The Consensus Committee that approved the code or standard wasbalanced to assure that Individuals from competent and concerned interests have had an opportunityto participate. The proposed code or standard was made ava

5、ilable for public review and commentwhich provides an opportunity for additional public Input from Industry, academia regulatoryagencies, end the pUblic-at-large.ASME does nC?t “epProve,“ “rate,“o“endorse“ any Item, construction. proprietary device, oractivity. .ASME does not take any position with

6、respect to the validity of any patent rights asserted Inconnection with any Items mentioned in this document, and does not undertake to insure anyoneutilizing a stimdard against liability for infringement of any applicable Letters Patent, nor assume anysuch liability. Users of a code or standard are

7、 expressly advised that determination ofthe validity ofany such patent rights, and the risk ofInfringement of such rights, Is entirely their own responsibility.Participation by federal agency representatlve(s) or person(s) affiliated with Industry Is not to beInterpreted as government or Industry en

8、dorsement of this code or standard.ASME accepts responsibility for only those Interpretations Issued In accordance with governingASME procedures and policies which preclude the Issuance of Interpretations by Individualvolunteers.No part of this document may be reproduced In any form,In an electronic

9、 retrieval system or otherwise,without the prior written permission of the publisher.Copyright 1989 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll Rights ReservedPrinted In U.S.A.FOREWORD(This Foreword Is not part of ASME/ANSI MFC-9M-1988.1This Standard was prepared by the ASMECommittee on Measur

10、ement of Fluid Flow inClosed Conduits (MFC). Itis based on and closely parallels the International Organizationfor Standardization(ISO) InternationalStandard ISO 4185-1980, incorporating U.S. prac tices and terminology where they differ.This Standard was approved by the American National Standards I

11、nstitute (ANSI) as anAmerican National Standard on December 15, 1988.iiiASME STANDARDS COMMITTEE MFCMeasurement of Fluid Flow In Closed Conduits(The following Is the roster of the Comrrilttee at the time of approval of this Standard.)OFFICERSR. W. Miller, ChairmanW. F. Z. Lee, Vice ChairmanC. J. Gom

12、ez, SecretaryCOMMITTEE PERSONNELR. B. AbernethyN. A. AlstonH. P. BeanS. R. BeitlerM. BradnerE. E. BuxtonJ. S. CastorlnaG. P. CorpronD. G. DarbyR. H. DieckR. B. DowdellA. G. FerronR. L. GalleyD.HalmiZ. D. HusainB. T. JeffriesE. H. Jones, Jr.L. J. KempC. A. KemperD. R. KeyserC. P. KittredgeC. G. Langf

13、ordW. F. Z. LeeE. D. MannherzG. E. MattinglyR. W. MillerM. H. NovemberW. M. Reese, Jr.P. G. ScottH. E. SniderD. W. SpitzerD. A. SullivanR. G. TeyssandlerPERSONNEL OF SUBCOMMITTEE 14 - FLOW MEASUREMENT BY WEIGHING ANDVOLUMETRIC MEASUREMENTSG. E. Mattingly, ChairmanG. P. CorpronR. B. DowdellD. HalmlG.

14、 A. LenzR. W. MillerP. G. ScottR. G. TeyssandlervCONTENTSForeword . iiiStandards Committee Roster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v1 General 11.1 Scope and Field of Application 11.2 References. . . . . . . . . . . . . . . . . . . . . . . . . . . .

15、. . . . . . . . . . . . . . . . . . . . . . 11.3 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Principles. .

16、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.1 Statement of the Principles . 22.2 Accuracy of the Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Apparatus . . . . . 23.1 Diverter ! 1.1 23.2 Time

17、-Measuring Apparatus ;. 93.3 Weighing Tank. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.4 Weighing Device . 103.5 Auxiliary Measurements. . 104 Procedure ; . . . . 104.1 Static Weighing Method .; 104.2 Dynamic Weighing Method 104.3 Common Provisions . 1

18、15 Calculation of Flow Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115.1 Calculation of Mass Flow Rate 115.2 Calculation of Volume Flow Rate. . . . . . . . . . . . . . . . . . . . . . . 116 Uncertainties In the Measurement of Flow Rate . . . . . . . . .

19、 . . . . 11FigureslA Diagram of an Installation for Calibration by Weighing (StaticMethod, Supply by a Constant Level Head Tank) 41B Diagram of an Installation for Flow Rate Measure by Weighing(Used for a Hydraulic Machine Test; Static Method, Supplyby a Constant Level Head Tank) . 5lC Diagram of an

20、 Installation for Calibration by Weighing (StaticMethod, Direct Pumping Supply) . 6ID Diagram of an Installation for Calibration by Weighing (Dynamic Method,Supply by a Constant Level Head Tank) 72 Examples of Diverter Design 83 Operational Law of Diverter . 84 Time Metering for a Diverter, the Oper

21、ation Law of Which Is Identicalin Both Directions . 9viiTable1 Symbols 3AppendicesA Corrections on the Measurement of Filling Time. . . . . . 13B Density of Pure Water 17FigureAl Plotting of Results of DiverterTimrActuatorviii14ASME/ANSI MFC-9M-1988MEASUREMENT OF LIQUID FLOW IN CLOSED CONDUITS BY WE

22、IGHING METHOD1 GENERAL1.1 Scope and Field of ApplicationThis Standard specifies a methodofliquid flow ratemeasurement in closed conduits by measuring themass of liquid delivered into a weighing tank in aknown time interval. It deals in particular with themeasuring apparatus, procedure, and method fo

23、r cal culating the flow rate and the uncertainties associatedwith the measurement.The method described may be applied to anyliquid,provided thatits vapor pressure is such that anyescapeof liquid from the weighing tank by vaporization isnot sufficient to affect the required measurementaccuracy. Close

24、d weighing tanks and their applicationto the flow measurement ofliquids ofhighvapor pres sure are not considered in this Standard.This Standard considers only the measurementtechniques and does not address any possible haZardsinvolved in handling the liquid involved.Theoretically, there is no limit

25、to the application ofthis method, which is used generally in fixedlabortory installations only. However, for economic rea sons, typical hydraulic laboratories using this methodcan produce accurate flow rates of 500 kg/s (3300Ibm/sec) or less.Owing to its high potential accuracy, this method isoften

26、used as a primary method for calibration ofother methods or devices for mass flow rate measure ment or volumetric flow rate measurement, providedthat the density of the liquid is known accurately.It must be ensured that the pipeline is running fullwith no air or vapor pockets present in the measurin

27、gsection.1.2 ReferencesThe American Society ofMechanical EngineersANSIIASME MFC-IM (latest edition), Glossaryof Terms lJsed in the Measurement ofFIidFlow inPipesANSI/ASME MFC-2M (latest edition), Measure ment Uncertainty for Fluid Flow in Closed Conduits1International Organization ofLegal MetrologlR

28、ecommendation No.1, Cylindrical Weights From1 Gram to 10 Kilograms of Medium Accuracy ClassRecommendation No.2, Rectangular Bar WeightsFrom 5 Kilograms to 50 Kilograms of Medium Accu racy ClassRecommendation No.3, Metrological Regulationsfor Non-Automatic Weighing MachinesRecommendation No. 20, Weig

29、hts of AccuracyClasses 1 E2FIF2MIFrom50 Kilograms to 1 Milli gramRecommendation No. 28, Technical Regulationsfor Non-Automatic Weighing MachinesRecommendation No. 33, Conventional Value ofthe Result of Weighing in Air1.3 DefinitionsThe following definitions are given for terms usedin some special se

30、nse or for terms, the meaning ofwhich seems useful to emphasize. A more comprehen sive list of definitions and symbols applicable to themeasurement of fluid flow in closed conduits can.befound in ANSI/ASME MFC-IM and ANSI/ASMEMFC-2M.buoyancy correction - correction made to the read ings of a weighin

31、g device to compensate for the up ward thrust exerted by the atmosphere. on the liquidbeing weighed and on the reference weights used dur ing the calibration of the weighing machiIiediverter - device which diverts the flow either to theweighing tank or its bypass without changing the flowrate during

32、 the measurement interval .dynamic weighing - method inwhich the net mass ofliquid collected is deduced from weighing made whilefluid flow is being delivered into the weighing tank (adiverter is not required with this method) .flow stabilizer:“ structure forming part of thehydraulic system, ensuring

33、 astable flow rate in the1Available from the International Bureau of Legal Metrology, 11rue Turgot, 75009, Paris, France.ASMEIANSI MFC-9M-1988conduit being supplied with liquid; for example, aconstant level head tank, the level of liquid which iscontrolled by a weir of sufficient capacitystatic weig

34、hing - method in which the net mass ofliquid collected is deduced from tare and gross weigh ings made before and after the liquid has been divertedfor a measured time interval into the weighing tank1.4 SymbolsTable 1reproduces the symbols that are used in thisStandard.2 PRINCIPLES2.1 Statement of th

35、e Principles2.1.1 Static Weighing. The principle of the flowrate measurement method by static weighing (forschematic diagrams oftypicinstallation, see Figs.lA, lB, and lC) is: .(a) to determine the initial mass of the tank plusany residual liquid;(b) to divert the flow into the weighing tank (until

36、itis consideredto contain a sufficient quantity to attainthe desired accuracy) by operation of the diverter,which actuates a timer to measure the filling time;(c) to determine the final mass ofthe tank plus theliquid collected in it.The flow rate is then derived from the mass col lected, the collect

37、ion time, and other data as discussedin Section 5 and Appendix A.2.1.2 Dynamic Weighing. The principle of theflow rate measurement method by dynamic weighing(see Fig. ID for a schematic diagram of a typical in-stallation) is: .(0) to let the liquid collect in the tank to a predeter mined initial mas

38、s, when the timer is then started;(b) to stop the timer when Ii predetermined finalmass of collected liquid is reached.The flow rate is then derived from the mass col lected, the collection time, andothrdata as discussedin Section 5 and Appendix A.2.1.3 Comparison of Instantaneous and MeanFlow Rate.

39、 It should, however, be emphasized thatonly the mean value offlow rate for the filling is givenbythe weighing method. Instantaneous values offlowrate as obtained on another instrument or meter intheflow circuit can be compared with the mean rate onlyif the flow is maintained stable during the measur

40、e ment interval by a flow-stabilizing system, or ifthe in-2MEASUREMENT OF LIQUID FLOW INCLOSED CONDUITS BY WEIGHING METHODstantaneous values are properly time.averaged duringthe whole filling period.2.2 Accuracy of the Method2.2.1 Overall Uncertainty on the WeighingMeasurement. The weighing method g

41、ives an abso lute measurement offlow which, in principle, requiresonly mass and time measurements. Provided that theprecautionslisted in para. 2.2.2 are taken, this methodmay be considered as one of the most accurate of allflow rate measuring methods, and for this reason it isoften used as a calibra

42、tion method. When the installa tion is carefully constructed, maintained, and used, anuncertainty of 0.1 % (with. 950/0 confidence limitsfor the random part of that uncertainty) can beachieved. .2.2.2 Requirements for Accurate Measure ments. The weighing method gives an accuratemeasurement of flow r

43、ate provided:(a) there is no leak in the flow circuit and there is nounmetered leakage flow across the diverter:(b) thereis no accumulation (or depletion) ofliquidiIi a part of the circuit by thermal contraction (or ex pansion), and there is no accumulation (or depletion)by change ofvapor or gas vol

44、ume contained unknow ingly in the flow circuit;(c) necessary corrections for the influence ofatmospheric buoyancy are made (this correction maybe made when calibrating the weighing apparatus);(d) the weighing device, the timer, and meansfor starting and stopping it achieve the necessaryaccuracy;(e)

45、the time required by thediverter for traversing issmall with respect to the filling time, the timer beingstarted and stopped while the diverter is crossing thehydraulic center line;(f) in the case ofthe dynamic weighing method, theeffects of the dynamic phenomena are sufficientlysmall.3 APPARATUS3.1

46、 DiverterThe diverter is a moving device used to direct flowalternately along its normal course or toward theweighing tank. Itcan be made up ofaconduit or mov ing gutter, or, better, by a baffle platepivoting arounda horizontal or vertical axis (see Fig. 2).The motion of the diverter should be suffi

47、cientlyfast (less than 0.1 s, for example) to reduce theMEASUREMENT OF LIQUID FLOW INCLOSED CONDUITS BY WEIGHING METHOD ASME/ANSI MFC-9M-1988TABLE 1 SYMBOLSDimension SI (Metrlcl U.S. (Customary)Symbol Quantity Note (1) Units Units8 Biasm Mass M kg Ibmqm Mass flow rateMr-1kg/s Ibm/secqv Volume flow r

48、ateL3r-1m3/s ft3/sect Time T s sectS5Two-tailed Students tV Volume L3“m3ft3URSSU96“Uncertainty at the 95% confidencelevelUADDUSBUncertainty at the 99% confidencelevelIDens,yof,liquid ., MC3kg/mIbm/ft31/1Density of air (at 20C and 1 bar“lML-3kg/m3Ibm/ft3QpDensity of standard weillhtsML-3kg/m3Ibm/ft3C

49、1 Standard deviation of the sample“1 bar = 106PaNOTE:(1) Fundamental dimensions: M = mass, L = length, T= time.“3ASME/ANSI MFC-9M-1988Constant level head tankOverflowPumpDevice undercalibrationMEASUREMENT OF LIQUID FLOW INCLOSED CONDUITS BY WEIGHING METHODFlow controlvalveSump- -FIG. 1A DIAGRAM OF AN INSTALLATION FOR CALIBRATION BY WEIGHING(Static Method,Suplyby a Cons1ant Level Head Tank)4MEASUREMENT OF LIQUlb FLOW INCLOSED CONDUITS BY WEIGHING METHODConstant level head tankOve