1、AN AMERICAN NATIONAL STANDARD ASME MFC-162014(Revision of ASME MFC-162007)Measurement of Liquid Flow in Closed Conduits With Electromagnetic FlowmetersASME MFC-162014(Revision of ASME MFC-162007)Measurement ofLiquid Flow in ClosedConduits WithElectromagneticFlowmetersAN AMERICAN NATIONAL STANDARDTwo
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11、o 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 EngineersTwo Park Avenue, New York, NY 10016-5990Copyright 2014 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERS
12、All rights reservedPrinted in U.S.A.CONTENTSForeword ivCommittee Roster . vCorrespondence With the MFC Committee . vi1 Scope 12 References 13 Definitions and Symbols . 14 Theory and Measurement Technique 15 Flowmeter Descriptions 46 Application Considerations . 47 Equipment Markings. 78 Calibration
13、7Figures4-1 Industrial Electromagnetic Flowmeters 24.2-1 Examples of Electromagnetic Field (Bo) Variation With Time . 34.3-1 Examples of Electrodes for an Electromagnetic Flowmeter . 36.4-1 Electromagnetic Flowmeter System . 5Table3.2-1 Symbols . 2Nonmandatory AppendicesA Added Details Regarding The
14、ory and Measurement Technique 9B Liner Material Guidelines 11C Manufacturer-Specified Accuracy . 13D Calculation Examples 15E Bibliography . 16iiiFOREWORDThis Standard was prepared by Subcommittee 16 of the ASME Committee on the Measurementof Liquid Flow in Closed Conduits. The chair of the subcommi
15、ttee is indebted to the manyindividuals who contributed to this document.Electromagnetic flowmeters were introduced to the process industries in the mid 1950s. Theyquickly became accepted flowmeters for difficult applications. Subsequent improvements in tech-nology and reductions in cost have transf
16、ormed these flowmeters into one of the leading contend-ers for general use in water-based and other electrically conducting liquid applications.Due to differences in design of the various electromagnetic flowmeters in the marketplace, thisStandard cannot address detailed performance limitations in s
17、pecific applications. It covers issuesthat are common to all meters, including application considerations.The flow industry has been changing from the use of the names “primary” and “secondary”to “sensor” and “transmitter.” Previous editions of ASME MFC-16 did use primary and secondaryin their figur
18、es and text. This new edition uses the sensor and transmitter terminology.Suggestions for improvement of this Standard will be welcomed. They should be sent to TheAmerican Society of Mechanical Engineers; Attn: Secretary, MFC Standards Committee; Two ParkAvenue; New York, NY 10016-5990.This revision
19、 was approved an an American National Standard on January 28, 2014.ivASME 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 ChairD. C. Wyat
20、t, Vice ChairC. J. Gomez, SecretarySTANDARDS COMMITTEE PERSONNELC. J. Blechinger, Honorary Member, ConsultantR. M. Bough, Rolls-Royce Corp.M. S. Carter, Flow Systems, Inc.R. J. DeBoom, ConsultantD. Faber, Contributing Member, Badger Meter, Inc.C. J. Gomez, The American Society of Mechanical Engineer
21、sF. D. Goodson, Emerson Process Management DanielZ. D. Husain, Chevron Corp.C. G. Langford, Honorary Member, ConsultantW. M. Mattar, Invensys/Foxboro Co.SUBCOMMITTEE 16 ELECTROMAGNETIC FLOWMETERSR. J. DeBoom, Chair, ConsultantC. A. Diederichs, Emerson Process Management RosemountM. J. Keilty, Endres
22、s + Hauser Flowtec AGM. M. Lloyd, The Dow Chemical Co.W. M. Mattar, Invensys/Foxboro Co.R. W. Miller, Contributing Member, R. W. Miller however, they shouldnot contain proprietary names or information.Requests that are not in this format may be rewritten in the appropriate format by the Committeepri
23、or to 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 aninterpretation may appeal to th
24、e 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 Standards Committee regularly holds meetings thatare open to the public. Persons wishing to attend any mee
25、ting should contact the Secretary ofthe MFC Standards Committee. Future Committee meeting dates and locations can be found onthe Committee Page at go.asme.org/MFCcommittee.viASME MFC-162014MEASUREMENT OF LIQUID FLOW IN CLOSED CONDUITS WITHELECTROMAGNETIC FLOWMETERS1 SCOPEThis Standard is applicable
26、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 (pulsed-DC) togenerate a magnetic field in electrically conductive andelec
27、trically homogeneous liquids or slurries flowing ina completely filled, closed conduit.This Standard does not cover the following:insertion-type electromagnetic flowmeterselectromagnetic flowmeters used in surgical, thera-peutic, or other health and medical applicationsapplications of industrial flo
28、wmeters involvingnonconductive liquidshighly conductive liquids (e.g., liquid metals)2 REFERENCESThe following document forms a part of this Standardto the extent specified herein. The latest edition shallapply.ISO 13359, Measurement of conductive liquid flow inclosed conduits Flanged electromagneti
29、cflowmeters Overall lengthPublisher: International Organization forStandardization (ISO) Central Secretariat, 1, ch. de laVoie-Creuse, Case postale 56, CH-1211, Geneve 20,Switzerland/Suisse3 DEFINITIONS AND SYMBOLS3.1 Definitionsaccuracy of measurement: closeness of the agreementbetween the result o
30、f a measurement and a true valueof the measurand.NOTE: Accuracy is a qualitative concept; for the quantitativeconcept, see uncertainty.calibration: the experimental determination of the rela-tionship between the quantity being measured and thedevice that measures it, usually by comparison with astan
31、dard, then (typically) correcting the output of thatdevice to bring it to the desired value, within a specifiedtolerance, for a particular value of the input.1flowmeter sensor: includes the flow tube, process connec-tions, electromagnetic coils, and electrodes. Flowmetersensor is also known by other
32、 names, e.g., flowmetersensor device, sensor device, and sensor.flowmeter transmitter: includes the electronic transmitter,measurement of the emfv, and, in most cases, the powerfor the electromagnet coils of the flowmeter sensor.meterfactor: the number determined by liquid calibrationthat enables th
33、e output flow signal to be related to thevolumetric flow rate under defined reference conditions;often expressed as the reciprocal of mean K-factor.uncertainty (of measurement): parameter, associated withthe result of a measurement, that characterizes the dis-persion of the values that could reasona
34、bly be attributedto the measurand.verification: provision of objective evidence that a givenitem fulfills requirements.EXAMPLE: Use of independent flow calibration to confirm thatperformance properties and/or legal requirements of a measuringsystem are met.3.2 SymbolsSee Table 3.2-1.4 THEORY AND MEA
35、SUREMENT TECHNIQUEIndustrial electromagnetic flowmeters are composedof the following basic components (see Fig. 4-1):(a) a nonmagnetic tube with a nonconductive innersurface(b) a magnetic field passing through the tube andperpendicular to the axis of the tube at the center of theflow tube(c) a minim
36、um of two electrodes on opposite sidesof the tube in a cross-sectional plane passing throughthe center of the flow tube, the straight line betweenthese two electrodes being perpendicular to the mag-netic field at the center of the flow tube4.1 Flow-Related Electromotive ForceFaradays law of inductio
37、n applied to this physicalconfiguration predicts the generation of an electromo-tive force (a voltage) between the electrodes when aASME MFC-162014Table 3.2-1 SymbolsDimensionsQuantity Note (1) SI Units U.S. Customary UnitsC A dimensionless parameter that depends on the specific design of the . . .
38、. . . . . .flowmeter (see section 4)D Inner diameter of the flow tube L m in.K Meter factor, typically determined by liquid flow calibration M1LT2I m3/s/volt ft3/sec/voltV Flow velocity LT1m/s ft/secBoAverage magnetic field between the electrodes MT2I1tesla . . .q Flow rate, volumetric L3T1m3/s ft3/
39、secemf Electromotive force ML2T3I1volt voltemfcElectrochemical electromotive force ML2T3I1volt voltemfvVelocity-related electromotive force ML2T3I1volt voltemftTransformer-related electromotive force ML2T3I1volt voltemfFElectromotive force per Faradays Law ML2T3I1volt voltNOTE:(1) Dimensions: M pmas
40、s, L plength, T ptime, I p current.Fig. 4-1 Industrial Electromagnetic FlowmetersDFlow tube withnonconductivelinerCoilElectrodeCoilVemfvemfvBo2ASME MFC-162014conductive liquid flows through the flow tube. Thiselectromotive force isemfvpCDBoV (4-1)whereBop magnetic field at the center of the flow tub
41、e,teslaC p a dimensionless parameter that depends onthe specific design of the flowmeterD p inner diameter of the flow tube, memfvp electromotive force, VV p flow velocity (average axial liquid velocity ina cross-sectional plane of the flow tube), m/sFor added details on the theory and measurementte
42、chniques related to electromagnetic flowmeters, seeNonmandatory Appendix A.4.2 Interfering Sources of Electromotive ForceIn addition to the above flow-related electromotiveforce, emfv, two other sources of electromotive force existin modern industrial electromagnetic flowmeters thatmay interfere wit
43、h the measurement of emfv. They arethe electrochemical electromotive force, emfc, and thesensor transformer electromotive force, emft. Since bothof these may be similar to or larger than emfvin magni-tude, using an alternating electromagnetic field andinterval sampling techniques avoids interference
44、 to theflow signal, emfv, from these other two sources.Figure 4.2-1 illustrates three basic methods for alternat-ing the electromagnetic field. For additional informationabout both emfcand emft, see NonmandatoryAppendix A.4.3 Types of ElectrodesAn alternating electromagnetic field generates analtern
45、ating emfv. The following types of electrodes areused with an alternating electromagnetic field:(a) wetted electrodes that protrude through the pipewall/liner into the flow stream see Fig. 4.3-1,illustration (a)(b) nonwetted (capacitive) electrodes located behindor within the tube wall/liner see Fig
46、. 4.3-1,illustration (b)4.4 Calculation of Volumetric Flow RateFrom eq. (4-1), the flow velocity is given byVpemfv/CDBoThe volumetric flow rate, q, is calculated byqpH9266D2V/4Combining these two equations,qpH9266D W emfv/4CBo3Fig. 4.2-1 Examples of Electromagnetic Field (Bo)Variation With Time(c) P
47、ulsed DC Field Varied in a Stepwise FashionWith a Duty Cycle Less Than 100%t (b) Pulsed DC Field Varied in a Stepwise FashionWith a Duty Cycle of 100%t (a) AC Field Varied in a Sinusoidal Fashiont Fig. 4.3-1 Examples of Electrodes for anElectromagnetic Flowmeter(a) WettedB(b) NonwettedBBecause the d
48、iameter, D, dimensionless parameter, C,and the magnetic field, Bo, are fixed in each individualmeter, these values can be grouped together in a singlefactor that is determined through calibration. Thus,qpK W emfvwhereK p meter factor, m3/s/VASME MFC-1620145 FLOWMETER DESCRIPTIONS5.1 Flowmeter Sensor
49、The flowmeter sensor must be designed and selectedto be an integral portion of the piping system (seepara. 6.4). It consists of the following:(a) a flow tube with a nonconductive inside surface(b) a means for integrating it into the pipeline(c) electromagnetic field coils(d) two or more sensing electrodes that may be wettedor nonwetted (see Fig. 4.3-1)(e) a housing to protect the coils and electrodes fromdamage and moistureIt may also include grounding electrodes or groundingrings, which are used to ground the process and theflowmeter senso
