1、Measurement of Liquid Flow in Closed Conduits With Electromagnetic FlowmetersAN AMERICAN NATIONAL STANDARDASME MFC-162007Revision of ASME MFC-16M1995 (R2006)Copyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or networking permitted without license from
2、 IHS-,-,-ASME MFC-162007Revision of ASME MFC-16M1995 (R2006)Measurement ofLiquid Flow inClosed ConduitsWithElectromagneticFlowmetersAN AMERICAN NATIONAL STANDARDThree Park Avenue New York, NY 10016Copyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or n
3、etworking permitted without license from IHS-,-,-Date of Issuance: August 6, 2007This Standard will be revised when the Society approves the issuance of a new edition. There willbe no addenda issued to this edition.ASME issues written replies to inquiries concerning interpretations of technical aspe
4、cts of thisStandard. Periodically certain actions of the ASME MFC Committee may be published as Cases.Cases and interpretations are published on the ASME Web site under the Committee Pages athttp:/cstools.asme.org as they are issued.ASME is the registered trademark of The American Society of Mechani
5、cal Engineers.This code or standard was developed under procedures accredited as meeting the criteria for American NationalStandards. The Standards Committee that approved the code or standard was balanced to assure that individuals fromcompetent and concerned interests have had an opportunity to pa
6、rticipate. The proposed code or standard was madeavailable for public review and comment that provides an opportunity for additional public input from industry, academia,regulatory agencies, and the public-at-large.ASME does not “approve,” “rate,” or “endorse” any item, construction, proprietary dev
7、ice, or activity.ASME does not take any position with respect to the validity of any patent rights asserted in connection with anyitems mentioned in this document, and does not undertake to insure anyone utilizing a standard against liability forinfringement of any applicable letters patent, nor ass
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10、.No part of this document may be reproduced in any form,in an electronic retrieval system or otherwise,without the prior written permission of the publisher.The American Society of Mechanical EngineersThree Park Avenue, New York, NY 10016-5990Copyright 2007 byTHE AMERICAN SOCIETY OF MECHANICAL ENGIN
11、EERSAll rights reservedPrinted in the U.S.A.Copyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-CONTENTSForeword ivCommittee Roster . vCorrespondence With the MFC Committee . vi1 Scope 12 References 1
12、3 Definitions and Symbols. 14 Theory and Measurement Technique 25 Flowmeter Descriptions 46 Application Considerations 47 Equipment Markings 78 Calibration 7Figures1 Basic Components of an Electromagnetic Flowmeter 32 Electromagnetic Flowmeter System . 33 Examples of Electromagnetic Field (Bo) Varia
13、tion With Time 34 Examples of Electrodes for an Electromagnetic Flowmeter 3Table1 Symbols . 2Nonmandatory AppendicesA Additional Details Regarding Theory and Measurement Technique 9B Items of Potential Interest to Users . 10C Liner Material Guidelines 12D Accuracy Specifications for Electromagnetic
14、Flowmeters 13E Calculation Examples 14F Additional References . 15iiiCopyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-FOREWORDThis Standard was prepared by Subcommittee 16 of the ASME Committee on
15、the Measurementof Liquid Flow in Closed Conduits. The chair of the subcommittee is indebted to the manyindividuals who contributed to this document.Electromagnetic flowmeters were introduced to the process industries in the mid 1950s.Theyquickly became an accepted flowmeter for difficult application
16、s. Subsequent improvements intechnology and reductions in cost have transformed this flowmeter into one of the leadingcontenders for general use in water based and other electrically conducting liquid applications.Due to differences in design of the various electromagnetic flowmeters in the marketpl
17、ace, thisStandard cannot address detailed performance limitations in specific applications. It covers issuesthat are common to all meters, including application considerations.Suggestions for improvements to this Standard are encouraged. They should be sent to: Secre-tary, ASME MFC Committee, the Am
18、erican Society of Mechanical Engineers, Three Park Avenue,New York, NY 10016-5990.ASME MFC-162007 was approved by the American National Standards Institute (ANSI) onMarch 26, 2007.ivCopyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or networking permi
19、tted without license from IHS-,-,-ASME MFC COMMITTEEMeasurement of Fluid Flow in Closed Conduits(The following is the roster of the Committee at the time of approval of this Standard.)STANDARDS COMMITTEE OFFICERSR. J. DeBoom, ChairZ. D. Husain, Vice ChairC. J. Gomez, SecretarySTANDARDS COMMITTEE PER
20、SONNELC. J. Blechinger, Member Emeritus, ConsultantR. M. Bough, Rolls-RoyceG. P. Corpron, ConsultantR. J. DeBoom, ConsultantR. H. Fritz, Corresponding Member, Lonestar Measurement however, they shouldnot contain proprietary names or information.Requests that are not in this format will be rewritten
21、in this format by the Committee priorto being answered, which may inadvertently change the intent of the original request.ASME procedures provide for reconsideration of any interpretation when or if additionalinformation that might affect an interpretation is available. Further, persons aggrieved by
22、 aninterpretation may appeal to the cognizant ASME Committee or Subcommittee. ASME does not“approve,” “certify,” “rate,” or “endorse” any item, construction, proprietary device, or activity.Attending Committee Meetings. The MFC Committee regularly holds meetings, which are opento the public. Persons
23、 wishing to attend any meeting should contact the Secretary of theMFC Standards Committee.viCopyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-ASME MFC-162007MEASUREMENT OF LIQUID FLOW IN CLOSED COND
24、UITS WITHELECTROMAGNETIC FLOWMETERS1 SCOPEThis Standard is applicable to industrial electromag-netic flowmeters and their application in the measure-ment of liquid flow. The electromagnetic flowmeterscovered by this Standard utilize an alternating electricalcurrent (AC) or pulsed direct-current (pul
25、sed-DC) togenerate a magnetic field in electrically conductive andelectrically-homogeneous liquids or slurries flowing ina completely filled, closed conduit.This Standard specifically does not cover insertion-type electromagnetic flowmeters, meters used to mea-sure flow in partially filled pipe, or
26、those used in surgi-cal, therapeutic, or other health and medicalapplications. It also does not cover applications of indus-trial flowmeters involving nonconductive liquids orhighly conductive liquids (e.g., liquid metals).2 REFERENCESAll references are to the latest published edition ofthese standa
27、rds. The following is a list of publicationsreferenced in this Standard.ASME B16 Series, Standards for Valves, Fittings,Flanges, and GasketsASME MFC-1M, Glossary of Terms Used in theMeasurement of Fluid Flow in PipesPublisher: The American Society of MechanicalEngineers (ASME), Three Park Avenue, Ne
28、w York,NY 10016-5990; Order Department: 22 Law Drive,P.O. Box 2300, Fairfield, NJ 07007-2300ISO 13359, Measurement of Conductive Liquid Flow inClosed Conduits Flanged ElectromagneticFlowmeters Overall LengthPublisher: International Organization for Standardiza-tion (ISO), 1, ch. de la Voie-Creuse, C
29、ase postale 56,CH-1211, Geneve 20, Switzerland/Suisse3 DEFINITIONS AND SYMBOLS(a) Paragraph 3.1 lists definitions from ASMEMFC-1M used in ASME MFC-16.(b) Paragraph 3.2 lists definitions specific to thisStandard.(c) Paragraph 3.3 lists symbols used in this Standard(see Table 1).13.1 Definitions From
30、ASME MFC-1Maccuracy: the degree of freedom from error; the degreeof conformity of the indicated value to the true valueof the measured quantity.precision: the closeness of agreement between the resultsobtained by applying the experimental procedure sev-eral times under prescribed conditions. The sma
31、ller therandom part of the experimental errors that affect theresults, the more precise is the procedure.rangeability (turndown): flowmeter rangeability is theratio of the maximum to minimum flow rates or Reyn-olds number in the range over which the meter meetsa specified uncertainty (accuracy).repe
32、atability: the closeness of agreement among a seriesof results obtained with the same method on identicaltest material, under the same conditions (same operator,same apparatus, same laboratory, and short intervals oftime).uncertainty (of measurement): the range within which thetrue value of the meas
33、ured quantity can be expected tolie with a specified probability and confidence level.3.2 Definitions for ASME MFC-16bias: the systematic errors (i.e., those that cannot bereduced by increasing the number of measurementstaken under fixed flow conditions).flowmeterprimary: includes the flowtube, proc
34、ess connec-tions, electromagnetic coils, and electrodes. Flowmeterprimary is also known by other names such as: flow-meter primary device, primary device, primary etc.flowmeter secondary: includes the electronic transmitter,measurement of the emfv, and in most cases the powerfor the electromagnet co
35、ils of the flowmeter primary.linearity: linearity refers to the constancy of the meterfactor over a specified range, defined by either the pipeReynolds number or the flow rate.meter factor: the number, determined by liquid calibra-tion, that enables the output flow signal to be relatedto the volumet
36、ric flow rate under defined reference con-ditions.3.3 SymbolsSee Table 1.Copyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-ASME MFC-162007Table 1 SymbolsDimensionsQuantity Note (1) SI Unit USC Units
37、C A dimensionless parameter that depends on the specific design of the . . . . . . . . .flowmeter (see section 4) Note (2)D Inner diameter of the flowtube Note (3) L m in. (inch)K Meter factor, typically determined by liquid flow calibration Note (2) M1LT2I m3/s/volt ft3/s/voltV Average special velo
38、city Note (3) LT1m/s ft/sBoAverage magnetic field between the electrodes Note (2) MT2I1Tesla . . .q Flow rate, volumetric L3T1m3/s ft3/semf Electromotive force ML2T3I1volt VoltemfcElectrochemical electromotive force Note (2) ML2T3I1volt VoltemfvVelocity related electromotive force Note (2) ML2T3I1vo
39、lt VoltemftTransformer related electromotive force Note (2) ML2T3I1volt VoltemfFElectromotive force per Faradays Law ML2T3I1volt VoltW Indicates scalar product Dimensionless . . . . . .NOTES:(1) Dimensions: M pmass, L plength, T ptime, I pcurrent.(2) Symbols defined specifically for this Standard.(3
40、) Symbols identical to ASME MFC-1M.4 THEORY AND MEASUREMENT TECHNIQUEA partial sketch of an industrial electromagnetic flow-meter is shown in Fig. 1.Figure 2 shows a typical installation of the electromag-netic flowmeter.4.1 Flow-Related Electromotive ForceFaradays Law of Induction applied to this p
41、hysicalconfiguration predicts the generation of an electromo-tive force (a voltage) between the electrodes when aconductive liquid flows through the flowtube. This elec-tromotive force isemfvpC W D W BoW V (1)whereBop magnetic field at the center of the flowtube,TeslaC p a dimensionless parameter th
42、at depends onthe specific design of the flowmeter and toa limited extent on the velocity profile. Thevelocity profile sensitivity of C also dependson the specific design of the flowmeter (seeparas. 6.2.2 and 6.4.1.1).D p inner diameter of the flowtube, memfvp electromotive force, voltV p flow veloci
43、ty. The average axial liquid veloc-ity in a cross-sectional plane of the flowtube,m/s.For added details on the theory and measurementtechniques related to electromagnetic flowmeters seeNonmandatory Appendix A.24.2 Electrochemical Electromotive ForceIn addition to the flow-related electromotive force
44、,emfv, an electrochemical electromotive force, emfc,ispresent between the electrodes. The emfcis an electro-chemical emf produced in the flowmeter primary similarto that generated in a battery. It can be similar in magni-tude to emfvand changes slowly. In order to reduce emfc,which would be a measur
45、ement bias, an alternatingelectromagnetic field is used. There exist a number ofvariations of the basic AC and DC fields shown in thisStandard. See para. A-2.1 for additional information.This electrochemical voltage, which varies slowly intime, is substantially reduced in magnitude by utilizingan al
46、ternating electromagnetic field.The manner in which the electromagnetic field is var-ied includes the following:(a) AC field is varied in a sinusoidal fashion seeFig. 3, illustration (a)(b) DC field is varied in a stepwise fashion seeFig. 3, illustrations (b) and (c)4.3 Types of ElectrodesAn alterna
47、ting electromagnetic field generates analternating emfv. Two types of electrodes can be usedwith an alternating electromagnetic field(a) wetted electrodes that protrude through the pipewall/liner into the flow stream see Fig. 4,illustration (a)(b) nonwetted (capacitive) electrodes located behindor w
48、ithin the tube wall/liner see Fig. 4, illustration (b)4.4 Calculation of Volumetric Flow RateFrom eq. (1) the flow velocity is given byVpemfv/C W D W BoCopyright ASME International Provided by IHS under license with ASME Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-ASME MFC-162007Fig. 1 Basic Components of an ElectromagneticFlowmeterDVemfvCoilElectrodeBoFig. 2 Electromagnetic Flowmeter SystemUpstream DownstreamFlowmeter secondary(integral mount)Flowmeter primary3Fig. 3 Examples of Electromagnetic Field (Bo)Variation With Time(c) Pulsed-DC Excitation (Step
