ANSI ASME MFC-6-2013 Measurement of Fluid Flow in Pipes Using Vortex Flowmeters《使用涡街流量计的管道内流量测定》.pdf

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1、AN AMERICAN NATIONAL STANDARD ASME MFC-62013Revision and Redesignation of ASME MFC-6M1998 (R2005)Measurement of Fluid Flow in Pipes Using Vortex FlowmetersMFC-62013Measurement of Fluid Flow in Pipes Using Vortex FlowmetersAN AMERICAN NATIONAL STANDARDRevision and Redesignation of ASME MFC-6M1998 (R2

2、005)Two Park Avenue New York, NY 10016 USADate of Issuance: July 31, 2013This Standard will be revised when the Society approves the issuance of a new edition.ASME issues written replies to inquiries concerning interpretations of technical aspects of this Standard. Periodically certain actions of th

3、e ASME MFC Committee may be published as Cases. Cases and interpretations are published on the ASME Web site under the Committee Pages at http:/cstools.asme.org/ as they are issued.Errata to codes and standards may be posted on the ASME Web site under the Committee Pages to provide correc-tions to i

4、ncorrectly published items, or to correct typographical or grammatical errors in codes and standards. Such errata shall be used on the date posted.The Committee Pages can be found at http:/cstools.asme.org/. There is an option available to automatically receive an e-mail notification when errata are

5、 posted to a particular code or standard. This option can be found on the appro-priate Committee Page after selecting “Errata” in the “Publication Information” section.ASME is the registered trademark of The American Society of Mechanical Engineers.This code or standard was developed under procedure

6、s accredited as meeting the criteria for American National Standards. The Standards Committee that approved the code or standard was balanced to assure that individuals from competent and concerned interests have had an opportunity to participate. The proposed code or standard was made available for

7、 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 device, or activity.ASME does not take any position with respect

8、 to the validity of any patent rights asserted in connection with any items mentioned in this document, and does not undertake to insure anyone utilizing a standard against liability for infringement of any applicable letters patent, nor assumes any such liability. Users of a code or standard are ex

9、pressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, is entirely their own responsibility.Participation by federal agency representative(s) or person(s) affiliated with industry is not to be interpreted as government or industry e

10、ndorsement of this code or standard.ASME accepts responsibility for only those interpretations of this document issued in accordance with the established ASME procedures and policies, which precludes the issuance of interpretations by individuals.No part of this document may be reproduced in any for

11、m,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 2013 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.iiiCONTENTSForew

12、ord ivCommittee Roster vCorrespondence With the MFC Committee vi1 Scope . 12 References and Related Documents . 13 Terminology and Symbols 14 Principle of Measurement . 25 Flowmeter Descriptions . 46 Application Considerations . 57 Installation . 78 Operation 89 Calibration 8Figures4-1 Vortex Format

13、ion . 49.2-1 Example of a K-Factor Curve . 9Tables3.3-1 Symbols . 33.3-2 Subscripts 39.1-1 Number of Pulses Needed to Achieve a Given Calibration Uncertainty 9Nonmandatory AppendicesA Period Jitter and Its Effect on Calibration 11B Bibliography . 12ivFOREWORDThis Standard has been prepared by Subcom

14、mittee 6, Vortex Shedding Flowmeters, of the ASME Standards Committee for Measurement of Fluid Flow in Closed Conduits (MFC). It is one of a series of standards covering a variety of devices that measure the flow of fluids in closed conduits. The vortex shedding principle has become an accepted basi

15、s for fluid flow measurement. Flowmeters based on this principle are available for measuring the flow of fluids ranging from cryogenic liquids to steam and high-pressure gases. Vortex shedding flowmeters are also referred to as vortex meters. Their designs are proprietary, and therefore, their desig

16、n details and associated uncer-tainty bands cannot be covered in this Standard. However, these devices have in common the shedding of alternating pairs of vortices from some obstruction in the meter.This Standard contains the relevant terminology, test procedures, list of specifications, application

17、 notes, and equa-tions with which to determine the expected performance characteristics.This revision was approved by the American National Standards Institute on February 19, 2013.vASME MFC COMMITTEEMeasurement of Fluid Flow in Closed Conduits(The following is the roster of the Committee at the tim

18、e of approval of this Standard.)STANDARDS COMMITTEE OFFICERSR. J. DeBoom, ChairZ. D. Husain, Vice ChairD. C. Wyatt, Vice ChairC. J. Gomez, SecretarySTANDARDS COMMITTEE PERSONNELC. J. Blechinger, Honorary Member, Consultant G. E. Mattingly, The Catholic University of AmericaR. M. Bough, Rolls-Royce C

19、orp. R. W. Miller, Honorary Member, R. W. Miller however, they should not contain proprietary names or information.Requests that are not in this format will be rewritten in this format by the Committee prior to being answered, which may inadvertently change the intent of the original request.ASME pr

20、ocedures provide for reconsideration of any interpretation when or if additional information that might affect an interpretation is available. Further, persons aggrieved by an interpretation may appeal to the cognizant ASME Committee or Subcommittee. ASME does not “approve,” “certify,” “rate,” or “e

21、ndorse” any item, construc-tion, proprietary device, or activity.Attending Committee Meetings. The MFC Standards Committee regularly holds meetings, which are open to the public. Persons wishing to attend any meeting should contact the Secretary of the MFC Standards Committee.ASME MFC-620131MeasureM

22、ent of fluid flow in PiPes using Vortex flowMeters1 sCoPeThis Standard (a) describes the use of vortex flowmeters, including their physical components, principle of operation, instal-lation, performance, influence factors, and calibration in a closed conduit running full for the measurement of volu-

23、metric flow rate and volume flow total of single-phase liquids or gases, including vapors such as steam (b) describes the use of vortex flowmeters in combi-nation with one or more other process measurements for the inferential measurement of mass flow rate, mass flow total, base volumetric flow rate

24、, base volume total, and heat flow metering(c) is limited to full-bore flowmeters and does not include the special case of insertion-type flowmeters2 referenCes and related doCuMents Unless otherwise indicated, the latest issue of a refer-enced standard shall apply.ASME MFC-1M, Glossary of Terms Use

25、d in the Measurement of Fluid Flow in PipesPublisher: The American Society of Mechanical Engineers (ASME), Two Park Avenue, New York, NY 10016-5990; Order Department: 22 Law Drive, P.O. Box 2900, Fairfield, NJ 07007-2900 (www.asme.org)IEC 60529, Degrees of Protection Provided by Enclosures (IP Code)

26、Publisher: International Electrotechnical Commission (IEC), 3, rue de Varemb, Case Postale 131, CH-1211 Genve 20, Switzerland/Suisse (www.iec.ch)3 terMinologY and sYMBols 3.1 definitions from asMe MfC-1M used in this standardFor the purposes of this Standard, the following defi-nitions are particula

27、rly useful in describing the charac-teristics of vortex shedding flowmeters. ASME MFC-1M provides a more extensive collection of definitions and symbols pertaining to the measurement of fluid flow in closed conduits. cavitation: the implosion of vapor bubbles formed after flashing when the local pre

28、ssure rises above the vapor pressure of the liquid.flashing: the formation of vapor bubbles in a liquid when the local pressure falls to or below the vapor pressure of the liquid, often due to local lowering of pressure because of an increase in the liquid velocity.K factor: in pulses per unit volum

29、e, the ratio of the meter output in number of pulses to the corresponding total volume of fluid passing through the meter during a measured period. Variations in the K factor may be pre-sented as a function of either the meter bore Reynolds number or the flow rate of a specific fluid at a specific s

30、et of thermodynamic conditions (see Fig. 9.2-1).lowest local pressure: the lowest pressure found in the meter. This is the pressure of concern regarding flashing and cavitation. Some of the pressure is recovered down-stream of the meter.meter bore Reynolds number: a dimensionless ratio of iner-tial

31、to viscous forces that is used as a correlating param-eter that combines the effects of viscosity, density, and pipeline velocity. It is defined asReDDU=mmeter factor: the reciprocal of the mean K factor.pressure loss: the difference between the upstream pres-sure and the pressure downstream of the

32、meter after recovery.random error: a component of the error of measurement that, in the course of a number of measurements of the same measurand, varies in an unpredictable way.NOTE: It is not possible to correct for random error.random uncertainty: a component of uncertainty associ-ated with a rand

33、om error. Its effect on mean values can be reduced by taking many measurements.rangeability: flowmeter rangeability is the ratio of the maxi-mum to minimum flow rates or Reynolds number in the range over which the meter meets a specified uncertainty.response time: for a step change in flow rate, res

34、ponse time is the time needed for the indicated flow rate to ASME MFC-620132differ from the true flow rate by a prescribed amount (e.g., 10%).systematic error: a component of the error of measure-ment that, in the course of a number of measurements of the same measurand, remains constant or varies i

35、n a predictable way.NOTE: Systematic errors and their causes may be known or unknown.systematic uncertainty: the error associated with sys-tematic error, i.e., the error that cannot be reduced by increasing the number of measurements under identical conditions. Also known as bias.3.2 definitions spe

36、cific to this standard linearity: linearity relates to the variations of the K factor over a specified range, defined either by ReDor qvof a specific fluid at specific thermodynamic conditions (see Fig. 9.2-1). In equation form, it is defined as%maxminmlinearityean5233KKK2100The upper and lower limi

37、ts of the linear range are specified by the manufacturer.Strouhal number: a dimensionless parameter that relates the measured vortex shedding frequency to the fluid velocity and the bluff body characteristic dimension. It is given bySt53fdUIn practice, the K factor, which is not dimension-less, repl

38、aces the Strouhal number as the significant parameter.uncertainty: an estimate characterizing the range of val-ues within which the true value of a measurement lies.3.3 symbols used in this standardSee Tables 3.3-1 and 3.3-2.4 PrinCiPle of MeasureMentWhen a bluff body is placed in a pipe in which fl

39、uid is flowing, a boundary layer forms and grows along the surface of the bluff body. Due to insufficient momentum and an adverse pressure gradient, separation occurs and an inherently unstable shear layer is formed. This shear layer rolls up into vortices that shed alternately from the sides of the

40、 body and propagate downstream. This series of vortices is called a von Karmanlike vor-tex sheet (see Fig. 4-1). The frequency at which vortices are shed is directly proportional to the fluid velocity. Since the shedding process is repeatable, it can be used to measure flow. Vortex shedding can be o

41、bserved in the ripple of a flag downstream from a flagpole.Sensors are used to detect shedding vortices, i.e., to convert the pressure or velocity variations associated with the vortices to electrical signals. One cycle of the shedding frequency corresponds to the generation of two vortices, one fro

42、m one side of the bluff body, fol-lowed by another from the bluff bodys other side. The electrical signal generated by a flowmeters vortex sen-sor varies at the shedding frequency, f, one cycle of which corresponds to the shedding of a pair of vortices. The Strouhal number, St, relates the frequency

43、, f, of generated vortices, the bluff body characteristic dimen-sion, d, and the fluid velocity, U.U53fdStFor certain bluff body shapes, the Strouhal number remains essentially constant within a large range of Reynolds numbers. This means that the Strouhal number is independent of density, pressure,

44、 viscosity, and other physical parameters. Given this situation, the flow veloc-ity is directly proportional to the frequency at which the vortices are being shed, i.e., the vortex pulse rate. U 5 3 f The constant, , is equal to d/St, and the volumetric flow rate at flowing conditions, i.e., the vol

45、ume flow rate, is given byqv5 A 3 U 5 (A 3 d)/St 3 f The K factor for a vortex shedding flowmeter is related to the Strouhal number byK 5 St/(A 3 d) 5 f/qv Henceqv5 f/K When the density at flowing temperature and pres-sure is known, the mass flow rate, qmsee eq. (1), and the volumetric flow rate at

46、base conditions, i.e., the standard volume flow rate, qvsee eq. (2), can be determined.qm5 f3 (f/K) (1)v5 (f/b) 3 f/K (2)If it is assumed that the flow rate can be considered constant over the time it takes a vortex pair to shed, i.e., over one cycle of period , then the amount of fluid vol-ume that

47、 flows through the meter during one cycle isqv 3 5 (f 3 )/K 5 1/K and the total flow over N cycles isQv 5 N/K ASME MFC-620133table 3.3-1 symbolsSymbol Quantity Dimension SI UnitsA Cross-sectional area of meter bore L2m2c1,c2Empirical constant Dimensionless . . .D Diameter of meter body L md Width of

48、 bluff body normal to the flow L mf Vortex shedding frequency (VSF) T21HzK K factor L23m23N Number of vortex pulses Dimensionless . . .QmTotalized mass flow M kgQvTotalized volume flow L3m3qmMass flow rate MT21kg/sqvVolume flow rate L3T21m3/sP Pressure ML21T22PaReReynolds number Dimensionless . . .S

49、t Strouhal number Dimensionless . . .T TemperatureKU Average fluid velocity in meter bore LT21m/saLinear thermal expansion . . . . . .mDynamic velocity of the fluid ML21T21Pas; Ns/m2; or kg/(ms)Fluid density ML23kg/m3GENERAL NOTE: Fundamental dimensions: L 5 length; M 5 mass; T 5 time; 5 temperature.table 3.3-2 subscriptsSubscript Description b Base conditionsD Unobstructed diameter of meter bore (see Table 3.3-1)dminMinimum downstream valuef Flowing conditionsflow Flowing fluid conditionsi The ith measurementm Mass unitmax Maximum valueme