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AN AMERICAN NATIO NAL STANDARD Measurement of Fluid Flow in Closed Conduits Tracer s ASME MFC-13M–2006 --,,,,,,,,,,,,--,,,,,,,--- ASME MFC-13M–2006 Measurement of Fluid Flow in Closed Conduits Tracer s AN AMERICAN NATIONAL STANDARD Three Park Avenue New York, NY 10016 --,,,,,,,,,,,,--,,,,,,,--- Date of Issuance February 12, 2007 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 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. 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The American Society of Mechanical Engineers Three Park Avenue, New York, NY 10016-5990 Copyright 2007 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 and Field of Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 2Symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 3Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 4 of Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 5Choice of Tracer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 6Measuring Length and Adequate Mixing Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 7Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 8Extensions of the s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 9Practical Application Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Table 1Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Nonmandatory Appendices ATypical Tracer Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 BMixing Distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 iii --,,,,,,,,,,,,--,,,,,,,--- FOREWORD This Standard defines the use of tracer dilution s in the measurement of single-phase fluid gas or liquid flows in closed conduits. This of measurement is applicable only to single-phase homogeneous fluid mixtures. This Standard was developed to fill the need for a generalized reference based on fundamental principles to measure fluid flow using tracer s. ISO standards issued in 1977 addressed tracer s for gas flows; these were withdrawn in 2001, leaving a void on this subject. An Internet search on this subject will find a large number of documents, standards, references, consultants, and manufacturers. Most of the papers, standards, and products are for very specific applications and provide detailed guidance only for those needs. This Standard defines the terms and principles needed for intelligent consideration of tracer s for any application. ASME MFC-13M–2006 was approved by the American National Standards Institute on September 29, 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 R. J. DeBoom, Chair Z. D. Husain, 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-13M–2006 MEASUREMENT OF FLUID FLOW IN CLOSED CONDUITS TRACER S 1SCOPE AND FIELD OF APPLICATION For steady-state flow of fluid in a closed conduit, the only conserved parameter is the mass rate of flow, qm. If the mass density is known, the volume rate of flow, qv, can be deduced. Theaccuracyofflowratemeasurementwiththetracer s is a function of how well the injected tracer materialmixeswiththeflowingfluid.Itisalsoafunction of the accuracy and precision of the sensing devices, and the tracer s techniques used. The following two tracer s are used a The dilution is based on a constant rate of tracer injection, and the concentration of tracer found in the downstream conduit is a measure of the relative flow rates. b The transit time determines the flow rate by measuring the time it takes the tracer material to travel between two detector points or between the injec- tion point and a detector point in the conduit. The advantages and disadvantages of these two meth- ods are reviewed in section 4. A wide variety of tracer materials may be used radioactive or nonradioactive, mineral or organic materials, etc. The choice of tracer depends on the pur- pose of the measurement and environmental concerns section 5. The uncertainty of the measurements depends completely on the accuracy of the s used section 7. Some typical tracer fluids are listed in Nonmandatory Appendix A. 2SYMBOLS See Table 1. 3UNITS Calculations for mass and volumetric flow rates in this document are expressed in terms of ratios of lengths and in other nondimensional parameters, as shown in Table 1. Hence, no dimensional units are defined for those terms. 4 OF USE 4.1 Dilution In the dilution , a measured quantity of tracer fluid of known composition is injected into the flowing 1 stream at the injection point. At the detection location, the mixtureis analyzed forcomposition. Asimple calcu- lation provides the flow of the main stream. If the mass of the tracer stream is known, then the result is in mass units. 4.1.1 Advantages of the Dilution a It is not necessary to know the geometrical charac- teristics of the conduit. b It is not necessary that the flowing conditions of the fluid p, T be the same between the two measuring cross sections. c It is not necessary to know the time of injection. d It is inherently a mass flow measurement. 4.2 Transit Time In the transit time , a quantity of tracer fluid is injected into the flowing stream. Two detection points are commonly used, with both far enough downstream to allow adequate mixing and far enough apart to achieve adequate precision in the time measurement. The flow of the mixed fluids should be continuous from the time of injection until the mixed fluid is detected at the second detection point. The time for the detected change in fluid properties is compared at the two points to provide the average velocity of the fluid mixture. The shape of the detected rise time, the length of the pulse, and the rate of decay are all used to estimate the degree of mixing and possible error. The cross section of the flow conduit at the detection points is used with the flow time to determine the volumetric flow rate at the seconddetectionpoint.Thetimerequiredfortracerfluid injectionisdeterminedbytheresponsetimeofthedetec- tor and the system geometry. 4.2.1 Advantages of the Transit Time a Itisnecessaryonlytodeterminethemodifiedfluid characteristic time distribution at two measuring cross sections separated by a known volume of pipe or conduit. b It is not necessary to know the volume, mass, or flow rates of the injected tracer. c Transit time is inherently a volumetric . d In some applications only one detection point is used, the injection point taking the place of the first detection point. --,,,,,,,,,,,,--,,,,,,,--- ASME MFC-13M–2006 Table 1Symbols SymbolDescriptionDimensionsSI UnitsU.S. Customary Units qvVolumetric flow rateL3T−1m3/sft3/sec qmMass flow rateMT−1kg/slbm/sec cVariation in percent concentration of tracer. . . f0Friction factor of a perfectly smooth conduit. . .. . .. . . para. 6.2.1.1 fFriction factor coefficient of resistance Moody. . .. . .. . . coefficient L/DRatio, conduit length to diameter, in the sameLL−1Not applicableNot applicable units of measure ReReynolds number. . .. . .. . . e The degree of fluid mixing is less critical in this . 4.2.2 Special Recommendation forthe Based on Transit Time Measurement.For this , it is preferable to have a conduit length of constant cross section between two measuring points, so that the flow parametersareapproximatelyconstantoverthemeasur- ing length. 5CHOICE OF TRACER 5.1 General a Different types of tracers may be used, but for satisfactory operation the tracer injected in the flowing fluid must satisfy the following requirements 1 it should mix well with the fluid in the conduit 2 the quantity used should result in negligible or known modifications of the flow rate of fluid in the flow stream 3 the instrument used to monitor the concentra- tionofthetracermusthavesufficientmeasurementaccu- racy, and be suitable for the fluids and environment 4 it should be chemically stable in the conditions of use 5 if the tracer material used is also present in the flow prior to injection of the tracer, it must be at a negligible or constant concentration b For the dilution , it is important that the tracer fluid does not react with the measured fluid, or withtheconduitwallmaterial,totheextentthatitaffects the measurement. c For transit time s, it is recommended that 1 the tracer concentration in the measuring cross sections can be determined at any time 2 to achieve greatest precision, the detector signal should be proportional to the tracer concentration and the detector response time be fast enough that time accuracy is not lost 2 5.2 Comparison Between the Different Tracers 5.2.1 Advantages of Radioactive Tracers See Table A-2 a If a tracer emitting gamma radiation with suffi- cient energy is permissible, the probes may be located outside the conduit. b Fortracerswithashorthalf-lifeandarechemically acceptable, any radioactive contamination disappears quickly. 5.2.2 Advantages of Nonradioactive Tracers a Nonradioactive tracers do not require consider- ation of the requirements and regulations for the owner- ship and handling of radioactive materials. b The substances generally remain stable with time. Delays between the supply and the use of the substance do not matter. 6MEASURING LENGTH AND ADEQUATE MIXING DISTANCE 6.1 Introduction Adequatemixingofthetracerwiththeflowingstream is required for accurate flow measurements. The mixing distanceisdefinedastheshortestdistancethatthemaxi- mum variation, c, in the mixture composition, as mea- sured over the cross section of the stream, is less than some predetermined value. This mixing distance is not one fixed value, but will vary with the allowable concentration variations the smaller the acceptable variation greater precision of measurement, the greater the mixing distance. The length of the available conduit may limit reduction of percent variation in concentration, c, below a certain value.Thisalsovarieswiththefluidflowpropertiesi.e., greater turbulence and flow disturbances aid mixing. A mult
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