ASME MFC-12M-2006 利用多端组合普雷斯顿管主要部件测量封闭管道中的液体流量.pdf

AN AMERICAN NATIO NAL STANDARD Measurement of Fluid Flow in Closed Conduits Using Multiport Averaging Pitot Primary Elements ASME MFC-12M–2006 --,,,,,,,,,,,,--,,,,,,,--- ASME MFC-12M–2006 Measurement of Fluid Flow in Closed Conduits Using Multiport Averaging Pitot Primary Elements AN AMERICAN NATIONAL STANDARD Three Park Avenue New York, NY 10016 --,,,,,,,,,,,,--,,,,,,,--- Date of Issuance October 9, 2006 This Standard will be revised when the society approves the issuance of a new edition. There will be no addenda issued to this edition. ASME issues written replies to inquiries concerning interpretations of technical aspects of this Standard. Interpretations are published on the ASME website under the Committee Pages at http//www.asme.org/codes/ as they are issued. ASME is the registered trademark of The American Society of Mechanical Engineers. This code or standard was developed under procedures accredited as meeting the criteria for American National Standards. 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The American Society of Mechanical Engineers Three Park Avenue, New York, NY 10016-5990 Copyright 2006 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All rights reserved Printed in U.S.A. --,,,,,,,,,,,,--,,,,,,,--- CONTENTS Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iv Committee Roster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v Correspondence With the MFC Committee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vi 1Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 2Terms and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 3References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 4Operating Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 5Flow Equations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 6Unit Construction Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 7Installation Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 8Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 9Flow Coefficient. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 10 Flow Rate Measurement Uncertainty. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Figures 1APT Showing Total and Reference Pressure Sensed on the Strut . . . . . . . . . . . . . . . . . . . . .4 2APT Showing Total Pressure Sensed on the Strut and Reference Pressure Sensed at the Pipe Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Tables 1Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Nonmandatory Appendices ATypical Cross Sections of Multiport Averaging Pitot Primary Elements . . . . . . . . . . . . . .9 BMultiport Averaging Pitot Primary Element Flow Theory . . . . . . . . . . . . . . . . . . . . . . . . . . .10 iii --,,,,,,,,,,,,--,,,,,,,--- FOREWORD Multiport averaging pitot primary elements cover a family of head-class devices that make use of the Bernoulli principal to measure the flow of liquids and gases. This Standard tries to clarify differences between the construction and operation of these devices and other head-class devices, such as orifice meters, Venturi meters, and nozzles. Due to differences in the design of multiport averaging pitot primary elements, this Standard cannot address detailed perance characteristics in specific applications. It does cover issues that are common to such devices. Suggestions for improvements to this Standard are encouraged and should be sent to Secretary, ASME MFC Committee, the American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990. ASME MFC-12M–2006 was approved by the American National Standard Institute on March 21, 2006. iv --,,,,,,,,,,,,--,,,,,,,--- ASME MFC COMMITTEE Measurement of Fluid Flow in Closed Conduits The following is the roster of the Committee at the time of approval of this Standard. STANDARDS COMMITTEE OFFICERS Z. D. Husain, Chair R. J. DeBoom, Vice Chair A. L. Guzman, Secretary STANDARDS COMMITTEE PERSONNEL C. J. Blechinger, Member Emeritus, Consultant R. M. Bough, Rolls-Royce G. P. Corpron, Consultant R. J. DeBoom, Consultant D. Faber, Corresponding Member, Badger Meter, Inc. R. H. Fritz, Corresponding Member, Lonestar Measurement however, they should not contain proprietary names or ination. Requests that are not in this at will be rewritten in this at by the Committee prior to being answered, which may inadvertently change the intent of the original request. ASME procedures provide for reconsideration of any interpretation when or if additional ination 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 “endorse” any item, construction, proprietary device, or activity. Attending Committee Meetings. The MFC 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. vi --,,,,,,,,,,,,--,,,,,,,--- ASME MFC-12M–2006 MEASUREMENT OF FLUID FLOW IN CLOSED CONDUITS USING MULTIPORT AVERAGING PITOT PRIMARY ELEMENTS 1SCOPE This Standard, provides ination on the use of multiport averaging Pitot head-type devices used to measure liquids and gases. The Standard applies when the conduits are full and the flow a has a fully developed profile b remains subsonic throughout the measurement section c is steady or varies only slowly with time d is considered single-phase A differential pressure transmitter or other pressure measuring device, known as a secondary element, must be used with a multiport averaging Pitot primary ele- ment to produce a flow rate measurement. Although multiport averaging Pitot primary elements are sometimes used in noncircular conduits, such appli- cations are beyond the scope of this Standard. 2TERMS AND DEFINITIONS The terminology and symbols Table 1 used in this Standard are in accordance with ASME MFC-1M. Some items from ASME MFC-1M are listed in para. 2.2.1 for easier reference. Terminology not defined in ASME MFC-1M, but used in this Standard, are defined in para. 2.2.2. 2.1 Symbols See Table 1. 2.2 Definitions 2.2.1 Definitions Found in ASME MFC-1M cavitation the implosion of vapor bubbles ed after flashing when the local pressure rises above the vapor pressure of the liquid. See also flashing. differential pressure device device inserted in a pipe to create a pressure differential whose measurement, together with a knowledge of the fluid conditions and of the geometry of the device and the pipe, enables the flow rate to be calculated. 1 flashing the ation 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. See also cavitation. primary device of a differential pressure device differential pressure device with its pressure tappings. rangeability flowmeter rangeability is the ratio of the maximum to minimum flowrates or Reynolds number in the range over which the primary element meets a specified uncertainty accuracy. reproducibility the closeness of agreement between results obtained when the conditions of measurement differ; for example, with respect to different test appara- tus, operators, facilities, time intervals, etc. Reynolds number a dimensionless parameter expressing the ratio between inertia and viscous forces. It is given by the ula Re p Vl v 1 where V p average spatial fluid velocity l p characteristic dimension of the system in which the flow occurs v p kinematic viscosity of the fluid NOTEWhenspecifying aReynoldsnumber,one shouldindicate thecharacteristicdimensiononwhichithasbeenbasede.g.,diam- eter of the pipe or width of the multiport averaging Pitot primary element. total pressure or total head also known as stagnation pressure; sum of the static pressure and the dynamic pressure. It characterizes the state of the fluid when its kinetic energy is completely transed into potential energy. 2.2.2 Definitions for MFC-12M APT or averaging Pitot tube common abbreviation for multiport averaging Pitot primary element. --,,,,,,,,,,,,--,,,,,,,--- ASME MFC-12M–2006MEASUREMENT OF FLUID FLOW IN CLOSED CONDUITS USING MULTIPORT AVERAGING PITOT PRIMARY ELEMENTS Table 1Symbols DimensionsSI SymbolQuantity[Note 1]Units DDiameter of the conduit [Note 2]Lm gLocal acceleration of gravity [Note 2]LT −2 m/s2 PAbsolute pressure [Note 2]ML−1T −2 Pa pDifferential pressure [Note 2]ML−1T −2 Pa qmMass flow rate [Note 2]MT −1 kg/s qvVolume flow rate [Note 2]L3T −1 m3/s ReReynolds number [Note 2]. . .. . . TAbsolute temperature [Note 2]K UMean axial velocity [Note 2]LT −1 m/s Expansibility [Note 2]. . .. . . Density [Note 2]ML−3kg/m3 AArea of conduit at measurement conditions [Note 3]L2m2 KFlow coefficient [Note 3]. . .. . . PgGage pressure [Note 3]ML−1T −2 Pa PtTotal pressure [Note 3]ML−1T −2 Pa PsLocal static pressure [Note 3]ML−1T −2 Pa zVertical elevation [Note 3]Lm qbVolume flow at base conditions [Notes 3 and 4]L3T −1 m3/s Absolute viscosity [Note 3]ML−1T −1 Pa.s NOTES 1 Dimensions M p mass,p temperature, L p length, T p time. 2 Symbols identical to ASME MFC-1M. 3 Symbols defined specifically for this Standard, ASME MFC-12M. 4 Subscript b is for base conditions. expansibilityexpansionfactordimensionlesscoefficient given by the ula p qm 4 KD22pf 2 where K is the flow coefficient of the APT and D is the pipe diameter. NOTES 1 This definition is similar to that given in MFC-1M. It has been modified to make it apply for APT applications. 2 Subscript f is for flowing conditions. in-situ the primary element is installed in the actual configuration and under actual flowing conditions in the conduit where it is to be used. linearity linearity refers to the constancy of the flow coefficient, K, over a range of Reynolds numbers or flow rates. This value is usually specified by maximum and minimum values of K defined over the range. The upper and lower limits of this range can be specified by the manufactureraseitheramaximumandminimumReyn- olds number range, flow rate range of a specified fluid, 2 or other meter design limitations such as pressure, tem- perature, or installation effects. NOTE This definition is similar to that given in MFC-1M. It has been modified to make it apply for APT applications. secondary device a device that receives a signal from the primary device and displays, records, and/or transmits it as a measure of the flow rate. velocity profiles distribution of axial vectors of the local fluid velocities over a cross-section of a conduit. 3REFERENCES Unless otherwise noted all references are to the latest published edition of these standards. The following is a list of publications referenced in this Standard. ASMEMFC-1M,GlossaryofTermsUsedintheMeasure- ment of Fluid Flow in Pipes ASME MFC-2M, Measurement Uncertainty for Fluid Flow in Closed Conduits ASME MFC-7M, Measurement of Gas Flow by Means of Critical Flow Venturi Nozzles --,,,,,,,,,,,,--,,,,,,,--- MEASUREMENT OF FLUID FLOW IN CLOSED CONDUITS USINGASME MFC-12M–2006 MULTIPORT AVERAGING PITOT PRIMARY ELEMENTS ASME MFC-8M, Connections for Pressure Signal Trans- missions Between Primary and Secondary Devices ASME MFC-9M, Measurement of Liquid Flow in Closed Conduits by Weighing ASME MFC-10M, for Establishing Installation Effects on Flowmeters Publisher The American Society of Mechanical Engineers ASME, Three Park Avenue, New York, NY 10016-5990; Order Department 22 Law Drive, P.O. Box 2300, Fairfield, NJ 07007-2300 ISO 4185, Measurement of Liquid Flow in Closed Conduits Weighing ISO 5168, Measurement of Fluid Flow uation of Uncertainties ISO 8316, Measurement of Liquid Flow in Closed Conduits by Collection of the Liquid in a Volumetric Tank Publisher International Organization for Standardiza- tionISO,1ruedeVarembe ,Case