A N A M E R I C A N N A T I O N A L S T A N D A R D ASME MFC 5 1–2011 (Revision and Partition of ANSI/ASME MFC 5M–1985) Measurement of Liquid Flow in Closed Conduits Using Transit Time Ultrasonic Flow[.]
ASME MFC-5.1–2011 (Revision and Partition of ANSI/ASME MFC-5M–1985) Measurement of Liquid Flow in Closed Conduits Using Transit-Time Ultrasonic Flowmeters A N A M E R I C A N N AT I O N A L STA N DA R D Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS ASME MFC-5.1–2011 (Revision and Partition of ANSI/ASME MFC-5M–1985) Measurement of Liquid Flow in Closed Conduits Using Transit-Time Ultrasonic Flowmeters A N A M E R I C A N N AT I O N A L S TA N D A R D Three Park Avenue • New York, NY • 10016 USA Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS Date of Issuance: June 17, 2011 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 document 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 at http://cstools.asme.org 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 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 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 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 assume any such liability Users of a code or standard are expressly 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 endorsement 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 form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher The American Society of Mechanical Engineers Three Park Avenue, New York, NY 10016-5990 Copyright © 2011 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All rights reserved Printed in U.S.A Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS CONTENTS Foreword Committee Roster Correspondence With the MFC Committee iv v vi General General Ultrasonic Flowmeter Descriptions Transit-Time Flowmeter Descriptions Uncertainty Sources and Uncertainty Reduction Installation and Selection Guidelines 10 Calibration, Verification, and Diagnostics 11 Figures 3-1 Wetted Transducer Configurations 3-2 Protected Configuration With Both an External Mount and a Wetted Smooth Bore 3-3 Acoustic Path Configurations 4-1 A Typical Cross Path Ultrasonic Flowmeter Configuration Tables 1-1 Symbols 1-2 Subscripts 3 iii Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS FOREWORD The need for a standard describing measurement of liquid measurement of liquid flows by means of transit-time ultrasonic flowmeters has been recognized for many years The ASME Standards Committee MFC, Measurement of Fluid Flow in Closed Conduits, developed a standard, ANSI/ASME MFC-5M–1985 to address this need Subsequently, it was decided to revise and partition ANSI/ASME MFC-5M into three standards to assist the readers in understanding the three technologies: transit time, cross-correlation, and scattering (Doppler) This Standard applies to ultrasonic flowmeters that base their operation on the measurement of transit time of acoustic signals This Standard concerns the volume flow-rate measurement of a single-phase liquid with steady flow or flow varying only slowly with time in a completely filled closed conduit The next standard planned in this series, Measurement of Liquids Using Cross-Correlation Ultrasonic Flowmeters (ASME MFC-5.2M), will apply to ultrasonic flowmeters that base their operation on the cross-correlation of modulated acoustic signals It will be concerned with the volume flow-rate measurement of a single-phase or multiphase liquid with steady flow or flow varying only slowly with time in a completely filled closed conduit The last standard planned for this series, Measurement of Liquids Using Scattering (Doppler) Ultrasonic Flowmeters (ASME MFC-5.3M), will apply to ultrasonic flowmeters that base their operation on the scattering (Doppler) of acoustic signals It will be concerned with the volume flow-rate measurement of two-phase liquid with steady flow or flow varying only slowly with time in a completely filled closed conduit Suggestions for improvement of this Standard are welcome They should be sent to The American Society of Mechanical Engineers; Attn: Secretary, MFC Standards Committee; Three Park Avenue; New York, NY 10016-5990 This Standard was approved as an American National Standard on January 28, 2011 iv Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS 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 R J DeBoom, Chair Z D Husain, Vice Chair D C Wyatt, Vice Chair C J Gomez, Secretary STANDARDS COMMITTEE PERSONNEL C J Blechinger, Honorary Member, Consultant R M Bough, Rolls-Royce Corp M S Carter, Flow Systems, Inc G P Corpron, Honorary Member, Consultant R J DeBoom, Consultant D Faber, Contributing Member, Badger Meter, Inc C J Gomez, The American Society of Mechanical Engineers F D Goodson, Emerson Process Management/Daniel Division Z D Husain, Chevron Corp C G Langford, Honorary Member, Consultant T O Maginnis, Consultant W M Mattar, Invensys/Foxboro Co G E Mattingly, The Catholic University of America R W Miller, Honorary Member, R W Miller & Associates, Inc A Quraishi, American Gas Association W Seidl, Colorado Engineering Experiment Station, Inc D W Spitzer, Contributing Member, Spitzer and Boyes LLC R N Steven, Colorado Engineering Experiment Station, Inc T M Kegel, Alternate, Colorado Engineering Experiment Station, Inc J H Vignos, Honorary Member, Consultant D E Wiklund, Emerson Process Management/Rosemount Division J D Wright, Contributing Member, NIST D C Wyatt, Wyatt Engineering SUBCOMMITTEE — ULTRASONIC FLOWMETERS P I Moore, Chevron Corp B K Rao, Consultant W Roeber, Racine Federated, Inc R Schaefer, Siemens Industry, Inc D M Standiford, Emerson Process Management/Micro Motion Division J S Trofatter, ADS, LLC S Y Tung, City of Houston, Public Works and Engineering K J Zanker, Letton-Hall Group R J DeBoom, Chair, Consultant G P Corpron, Consultant P G Espina, G E Energy Services R H Fritz, Regency Gas Service B Funck, Flexim Labs, LLC F D Goodson, Emerson Process Management/Daniel Division M J Keilty, Endress + Hauser Flowtec AG W M Mattar, Invensys/Foxboro Co v Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS CORRESPONDENCE WITH THE MFC COMMITTEE General ASME Standards are developed and maintained with the intent to represent the consensus of concerned interests As such, users of this Standard may interact with the Committee by requesting interpretations, proposing revisions, and attending Committee meetings Correspondence should be addressed to: Secretary, MFC Standards Committee The American Society of Mechanical Engineers Three Park Avenue New York, NY 10016-5990 http://go.asme.org/Inquiry Proposing Revisions Revisions are made periodically to the Standard to incorporate changes that appear necessary or desirable, as demonstrated by the experience gained from the application of the Standard Approved revisions will be published periodically The Committee welcomes proposals for revisions to this Standard Such proposals should be as specific as possible, citing the paragraph number(s), the proposed wording, and a detailed description of the reasons for the proposal, including any pertinent documentation Proposing a Case Cases may be issued for the purpose of providing alternative rules when justified, to permit early implementation of an approved revision when the need is urgent, or to provide rules not covered by existing provisions Cases are effective immediately upon ASME approval and shall be posted on the ASME Committee Web page Requests for Cases shall provide a Statement of Need and Background Information The request should identify the Standard, the paragraph, figure or table number(s), and be written as a Question and Reply in the same format as existing Cases Requests for Cases should also indicate the applicable edition(s) of the Standard to which the proposed Case applies Interpretations Upon request, the MFC Committee will render an interpretation of any requirement of the Standard Interpretations can only be rendered in response to a written request sent to the Secretary of the MFC Standards Committee The request for interpretation should be clear and unambiguous It is further recommended that the inquirer submit his/her request in the following format: Subject: Edition: Question: Cite the applicable paragraph number(s) and the topic of the inquiry Cite the applicable edition of the Standard for which the interpretation is being requested Phrase the question as a request for an interpretation of a specific requirement suitable for general understanding and use, not as a request for an approval of a proprietary design or situation The inquirer may also include any plans or drawings that are necessary to explain the question; however, they should not contain proprietary names or information Requests that are not in this format may be rewritten in the appropriate format 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 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 “endorse” any item, construction, proprietary device, or activity Attending Committee Meetings The MFC Standards Committee regularly holds meetings that are open to the public Persons wishing to attend any meeting should contact the Secretary of the MFC Standards Committee vi Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS ASME MFC-5.1–2011 MEASUREMENT OF LIQUID FLOW IN CLOSED CONDUITS USING TRANSIT-TIME ULTRASONIC FLOWMETERS GENERAL in the measurement section Common transit-time path types are axial, diametrical, and chordal 1.1 Scope axial flow velocity: component of liquid flow velocity, Vax, at a point in the measurement section that is parallel to the measurement section’s axis This Standard applies to ultrasonic flowmeters that base their operation on the measurement of transit time of acoustic signals This Standard concerns the volume flow-rate measurement of a single-phase liquid with steady flow or flow varying only slowly with time in a completely filled closed conduit calibration: experimental determination of the relationship between the quantity being measured and the device that measures it, usually by comparison with a traceable reference standard; also including the act of adjusting the output of a device to bring it to a desired value, within a specified tolerance, for a particular value of the input 1.2 Purpose This Standard provides (a) a description of the operating principles employed by the transit-time ultrasonic flowmeters (b) a guideline to expected performance characteristics of transit-time ultrasonic flowmeters (c) a description of calibration, verification, and diagnostic procedures (d) a description of potential uncertainty sources and their reduction (e) a common set of terminology, symbols, definitions, and specifications NOTE: This document is written with calibration defined as the determination of difference from a reference and the adjustment to align within a specified tolerance This is common U.S usage It is understood that in other parts of the world some countries and groups define calibration as only the determination of difference from a reference A second term used is calibration adjustment, which is to align within a specified tolerance cross-flow velocity: component of liquid flow velocity at a point in the measurement section that is perpendicular to the measurement section’s axis 1.3 Terminology and Symbols measurement section: section of conduit in which the volumetric flow rate is sensed by the acoustic signals The measurement section is bounded at both ends by planes perpendicular to the axis of the section and located at the extreme upstream and downstream transducer positions The measurement section is usually circular in cross section; however, it may be square, rectangular, elliptical, or some other shape (a) Paragraph 1.3.1 lists definitions from ASME MFC-1M used in this Standard (b) Paragraph 1.3.2 lists definitions specific to this Standard (c) Table 1-1 lists symbols used in this Standard (d) Table 1-2 lists subscripts used in this Standard 1.3.1 Definitions From ASME MFC-1M nonrefractive system: an ultrasonic flowmeter system in which the acoustic path crosses the transducer/process liquid interfaces at a right angle to the boundary surface accuracy: closeness of agreement between a measured quantity value and a true quantity value of a measurand NOTES: (1) The concept “measurement accuracy” is not a quantity and is not given a numerical quantity value A measurement is said to be more accurate when it provides a smaller measurement error (2) The term “measurement accuracy” is sometimes understood as closeness of agreement between measured quantity values that are being attributed to the measurand “Measurement accuracy” should not be mistaken for “measurement precision.” refractive system: an ultrasonic flowmeter in which the acoustic path crosses the conduit boundary/process liquid interfaces at other than a right angle transit time, t: time required for an acoustic signal to traverse an acoustic path uncertainty: parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used acoustic path: path that the acoustic signals follow as they propagate through the measurement section There may be one (single path) or more (multipath) acoustic paths NOTES: (1) Measurement uncertainty is often comprised of many components: Some of these may be evaluated by Type A evaluation Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS ASME MFC-5.1–2011 of measurement uncertainty from the statistical distribution of the quantity values from series of measurements and can be characterized by standard deviations The other components, which may be evaluated by Type B evaluation of measurement uncertainty, can also be characterized by experimental standard deviations derived from probability density functions based on experience or other information (2) In general, for a given set of information, it is understood that the measurement uncertainty is associated with a stated quantity value attributed to the measurand A modification of the value of this measurand may result in a modification of the associated uncertainty (3) If the result of a measurement depends on the values of quantities other than the measurand, the uncertainty of the measured values of these quantities contribute to the uncertainty of the result of the measurement device consists of a measurement section, transducers, and acoustic paths The measurement section may be a whole spool piece, or an existing section of conduit to which transducers are installed in the field The secondary device comprises the electronic equipment required to operate the transducers, make the measurements, process the measured data, and display or record the results The processing section, in addition to estimating the flow rate from the measurement, should be capable of rejecting invalid measurements, noise, etc The indicated flow rate may be the result of one or more individual flow velocity determinations Most meters have outputs available, either as standard features or as optional equipment Displays may show flow rate, integrated flow volume, and flow direction, and may be analog or digital Signal outputs usually include one or more of the following: current, voltage, digital, and a pulse rate proportional to flow These outputs may or may not be electrically isolated Flowmeters may also include alarms and diagnostic aids velocity profile correction factor, S: dimensionless factor based on measured knowledge of the velocity profile used to adjust the meter output verification: experimental determination of the relationship between the quantity being measured and the device that measures it, usually by comparison with a traceable reference standard 1.3.2 Definitions Specific to This Standard diagnostics: comparison of internal direct and derived measurement values to allow the user to ascertain the condition of the operation of the ultrasonic flowmeter The ultrasonic transit-time flowmeter is a sampling device that measure discrete path velocities of one or more pairs of transducers Each pair of transducers is located a known distance, L, apart such that one is upstream of the other (see Fig 3-1) The upstream and downstream transducers send and receive pulses of ultrasound alternately, referred to as contra-propagating transmission, and the times of arrival are used in the calculation of average axial velocity, x At any given instant, the difference between the apparent speed of sound in a moving liquid and the speed of sound in that same liquid at rest is directly proportional to the liquid’s instantaneous velocity As a consequence, a measure of the average axial velocity of the liquid along a path can be obtained by transmitting an acoustic pulse along the path in both directions and subsequently measuring the transit-time difference The volumetric flow rate of a liquid flowing in a completely filled closed conduit is defined as the average velocity of the liquid over a cross section multiplied by the area of the cross section Thus, by measuring the average velocity of a liquid along one or more acoustic paths lines (not the area) and combining the measurements with knowledge of the cross-sectional area and the velocity profile over the cross section, it is possible to obtain an estimate of the volumetric flow rate of the liquid in the conduit Several techniques can be used to obtain a measure of the average effective speed of propagation of an acoustic pulse in a moving liquid in order to determine the average axial flow velocity along an acoustic path line Two approaches, time domain and frequency domain, are discussed here mode conversion: when an ultrasonic wave passes at an oblique angle between two materials of variant acoustic impedance, mode conversion can occur As an example, when a wedge-type transducer is coupled to the outside of a pipe, the longitudinal waves generated by the ultrasonic transducer produce both longitudinal and shear waves in the pipe wall ultrasonic transducer: a device designed to convert electrical signals into directed ultrasonic waves and vice versa, usually by inclusion of materials exhibiting the piezoelectric or piezomagnetic effects When employed for flow measurement, ultrasonic transducers are commonly referred to simply as “transducers.” The transducers transmit and receive acoustic energy They may be factory mounted or field mounted by clamping, threading, or bonding Transducers may be wetted by the liquid or be nonwetted Wetted transducers may be flush mounted, recessed, or protruding into the flow stream Some transducers may be removed while the line is in service, depending on the manufacturer’s design 1.3.3 Symbols Used in This Standard See Table 1-1 1.3.4 Subscripts Used in This Standard Table 1-2 See GENERAL ULTRASONIC FLOWMETER DESCRIPTIONS The ultrasonic flowmeter can be thought of as comprising a primary and secondary device The primary Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS TRANSIT-TIME FLOWMETER DESCRIPTIONS ASME MFC-5.1–2011 Table 1-1 Symbols Symbol Quantity Dimensions SI Units A c f L n Q S t v w Cross-sectional area Speed of sound Frequency Distance between the upstream and downstream transducers Number of paths Volume flow rate Velocity profile correction factor Time Flow velocity Weighting factor for acoustical path Unit vector normal to the wave front Angle between the pipe wall and the direction of acoustic propagation Angle between the pipe wall normal and the direction of acoustic propagation L2 LT −1 T −1 L L3T −1 T LT −1 m2 m/s s−1 m m3/s s m/s rad rad Table 1-2 Subscripts Subscript Symbol Description up dn fluid_up fluid_dn fluid_up/dn meas_up/dn Upstream transmission path Downstream transmission path Upstream transmission path through the fluid only Downstream transmission path through the fluid only Abbreviation including both directions, fluid_up and fluid_dn Total signal transmission path from transmit to receive in each direction p fluid_up/dn + t0 (i.e., tmeas_up/dn p tfluid_up/dn + t0) Path number Direction corresponding to the pipe axis Direction orthogonal to the pipe axis and in the plane formed by the acoustic path and pipe axis i x y Fig 3-1 Wetted Transducer Configurations Upstream transducer element L Intervening material V x y Downstream transducer element Measurement section Recessed Protruding Copyright ASME International Provided by IHS under license with ASME No reproduction or networking permitted without license from IHS ASME MFC-5.1–2011 3.1 Time Domain 3.2 Frequency Domain The basis of this technique is the direct measurement of the transit time of acoustic signals as they propagate between a transmitter and a receiver The velocity of propagation of the ultrasonic signal is the sum of the speed of sound, c, and the flow velocity in the direction of propagation Therefore the transit time upstream and downstream can be expressed as In a frequency difference measurement approach (often called “sing around“), the reception of an acoustic signal at the receiver is used as a reference for generating a subsequent acoustic signal at the transmitter Assuming no delays other than the propagation time of the acoustic pulses in the liquid, the frequency at which the pulses are generated or received is proportional to the reciprocal of their transit time Thus, assuming L 冕 c + v1 ⴛ dl tfluid_up/dn ≈ ƒfluid_up/dn p l tp0 then where p unit normal vector to the wave front 1 p flow velocity vector at location, l, on the path, L ƒfluid_dn It can be shown that the transit time upstream and downstream, assuming flow velocity in the x direction with zero flow velocity in the y and z directions, and assuming x