AWWA M33-2006 Flowmeters in Water Supply (Second Edition)《水供应流量计 第2版》.pdf

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1、Science and TechnologyAWWA unites the drinking water community by developing and distributing authoritative scientific and technologicalknowledge. Through its members, AWWA develops industry standards for products and processes that advance publichealth and safety. AWWA also provides quality improve

2、ment programs for water and wastewater utilities.Flowmeters in Water SupplyAWWA MANUAL M33Second EditionMANUAL OF WATER SUPPLY PRACTICESM33, Second EditionFlowmeters in Water SupplyCopyright 1999, 2006 American Water Works AssociationAll rights reserved. No part of this publication may be reproduced

3、 or transmitted in any form or by anymeans, electronic or mechanical, including photocopy, recording, or any information or retrieval system,except in the form of brief excerpts or quotations for review purposes, without the written permission ofthe publisher.DisclaimerThe authors, contributors, edi

4、tors, and publisher do not assume responsibility for the validity of thecontent or any consequences of their use. In no event will AWWA be liable for direct, indirect, special,incidential, or consequential damages arising out of the use of information presented in this book. Inparticular, AWWA will

5、not be responsible for any costs, including, but not limited to, those incurred asa result of lost revenue. In no event shall AWWAs liability exceed the amount paid for the purchase ofthis book.Project Manager/Senior Technical Editor: Melissa ChristensenProduced by Stone Hill GraphicsManual Coordina

6、tor: Beth BehnerLibrary of Congress Cataloging-in-Publication DataFlowmeters in water supply.-2nd ed.p. cm. - (AWWA manual ; M33)Includes index.ISBN 1-58321-452-61. Flow meters. 2. Water-supply-Measurement-Equipment and supply. 3. Watercurrent meters. 4. Waterworks. I. American Water Works Associati

7、on.TC177.F555 2006681.282006042943Printed in the United States of AmericaAmerican Water Works Association6666 West Quincy AvenueDenver, CO 80235-3098ISBN 1-58321-452-6Printed on recycled paperContentsiiiList of Figures, vList of Tables, viiForeword, ixAcknowledgments, xiChapter 1Characteristics of F

8、low. 1Fluid Parameters, 1Types of Flow, 2Flow Conditioning, 4Meter Coefficient of Discharge, 4Chapter 2Types of Flowmeters 7Turbine and Propeller Flowmeters, 9Orifice Plate Flowmeters, 12Venturi Flowmeters, 14Modified Venturis, 18Averaging Pitot Flowmeters, 20Variable Area Flowmeters, 22Magnetic Flo

9、wmeters, 24Insertable Averaging Magnetic Flowmeter, 28Transit-Time Ultrasonic Flowmeters, 30Vortex Flowmeters, 33Chapter 3Flowmeter Selection 37Selection Parameters, 37Meter Selection Considerations, 40Meter Selection Block Diagram, 41Chapter 4Instalation and Performance Isues. 43Piping Configuratio

10、n, 43Flow Straighteners, 44Fluid Condition, 44Flowmeter Considerations, 44Electrical Connections, 46Chapter 5 Communication, Information and Signal Outputs . . . . 47Methods of Communication, 47Multivariable Information, 48Bibliography, 51Index, need text, 53Manuals List, 55This page intentionally b

11、lank.Figuresv1-1 Velocity profiles, 32-1 Schematic of propeller flowmeter and picture of turbine flowmeter, 92-2 Troubleshooting procedures for turbine meter, 112-3 Schematic of an orifice plate flowmeter, 132-4 Schematic of one type of Venturi meter, 152-5 Troubleshooting guide for a differential-p

12、ressure transducer, 172-6 Location of pressure ports in Venturi meter and flow tube, 192-7 Schematic of an averaging Pitot flowmeter insertion tube, 202-8 Variable area flowmeter, 232-9 Schematic of a magnetic flowmeter, 252-10 Flowchart of troubleshooting steps for installation check of magnetic fl

13、owmeter, 262-11 Schematic of an insertable averaging magnetic flowmeter, 292-12 Schematic of a transit-time ultrasonic flowmeter, 312-13 Schematic of a vortex flowmeter, 332-14 Troubleshooting flowchart for vortex flowmeters, 353-1 Flowmeter selection block diagram, 414-1 Typical flow straighteners,

14、 45This page intentionally blank.Tablesvii2-1 Types of flowmeters for the water industry, 83-1 Selected flowmeter selection data, 42This page intentionally blank.ForewordixThis manual was prepared as an introduction to the most common large flow-meters currently used in water supply systems. This ma

15、nual provides informationabout the most common flowmeters used in water treatment and in custody-transferapplications. Information on other meters can be obtained from AWWA Manual M6Water MetersSelection, Installation, Testing, and Maintenance. The flowmeters dis-cussed in this manual include the Ve

16、nturi, modified Venturi, orifice plate, electromag-netic (mag), turbine and propeller, transit-time ultrasonic, vortex, averaging Pitot, andaveraging insertable electromagnetic (mag). The discussion of these meters coversbasic theory, installation, maintenance, and advantages and disadvantages. Gene

17、ralconcepts applicable to flowmeters are also discussed, including flow characteristics,installation and performance issues, communication, information and signal outputs,and flowmeter selection.The manual can be used as a bridge to other literature on flowmeters, to preparethe reader for further in

18、vestigations into instrumentation design and applications. Thecited references will provide excellent information sources. For additional information,the reader should acquire the relevant manuals from the meter manufacturers. Thesemanuals contain comprehensive information on meter specifications, t

19、heory, sizing,handling, installation, power and wiring, operation, maintenance, troubleshooting,and parts.While this manual attempts to include recommended practice in the use of flow-meters, it is not intended as an AWWA standard.This page intentionally blank.AcknowledgmentsxiThis edition of the ma

20、nual was developed by a task force of the AWWA StandardsCommittee on Rate Type Flowmeters. The members of the task force had the followingpersonnel at the time of revision:J.J. Darby, Marsh-McBirney Inc., Frederick, Md.Barry Safa, Psomas, San Diego, Calif.S.F. Sarrouh, Consolidated Environmental Tec

21、hnologies, Cleveland, OhioJohn Trofatter, Accusonic Technologies, Inc., West Wareham, Mass.This edition of the manual was also reviewed and approved by the AWWA Stan-dards Committee on Rate Type Flowmeters. The members of the committee at the timethis manual was approved included:Joseph J. Gemin, Ch

22、airGeneral Interest MembersJ.A. Casados, Inst. Mex. De Techno. Del Agua, Progreso, Mor., MexicoJ.J. Gemin, Earth Tech (Canada) Inc., Kitchener, Ont.M.D. Kyser, Professional Engineering Consultants, P.A., Tulsa, Okla.J.E. Lintz,*Standards Council Liaison, Mueller Co., Longwood, Fla.P.W. Moorman, Blac

23、k the flow becomes turbulent, the particles begin movingat the same velocity, except in the laminar sublayer at the walls. Reynolds numberswill be noted in textbooks and vendor literature as having some impact on meter accu-racy and the meter coefficient of discharge.Distorted Velocity ProfilesThese

24、 profiles occur downstream from fittings, valves, or other obstructions. Major dis-turbances to the velocity profile generally result in a skewed profile, swirl, or flow sepa-ration. A skewed profile means asymmetric higher velocities in some sections thanother sections of the profile. Swirl means t

25、hat the flow has random vortices with rota-tion along and/or normal to the flow direction. Crossflow may be a part of swirl; how-ever, it involves flow with velocity vectors nonparallel to the pipe axis. Flow separationoccurs when the fluid passes over a sharp edge or corner, which causes the flow t

26、o sepa-rate from the wall, possibly reattaching at a later point downstream. All the previouslymentioned conditions create what can be called distorted profiles that make accurateflow measurement difficult. This is because the average velocity is not uniform andsteady throughout the pipes cross-sect

27、ional area. The importance of this topic cannot beoverstated, but it should be noted that with all inferential flowmetering devices, thevelocity profiles, both upstream and downstream, can and do effect the flowmeter. Thispoints out the importance of upstream and downstream undisturbed lengths of pi

28、pe, orthe need for additional flow conditioning, or additional testing.FLOW CONDITIONING_When the required undisturbed pipe length is not available, flow conditioners may beused to attempt to straighten the velocity profile and return it to uniformity. This isan option provided the fluid being measu

29、red, such as finished water, does not containany solids or other material that can plug the conditioner and that the additional headloss can be tolerated. Such devices include tube bundles, vanes, and other proprietarydevices that are placed in the flow creating an obstruction. These flow conditione

30、rscause a quick return to the normal turbulent profile shown in Figure 1-1 by inducingpressure gradients and redirecting velocities normal to the main flow direction. How-ever, it is cautioned that these devices still do require some downstream straightlengths before the flowmeters. Consulting with

31、flowmeter and flow conditioner manu-facturers regarding applicability and installation data is highly recommended.METER COEFFICIENT OF DISCHARGE _The coefficient of discharge Cdis used to account for deviations from the true averagevelocity and the cross-sectional area of the pipe and is used primar

32、ily with differen-tial pressure meters. The ratio of actual rate of flow (determined by high-accuracyCHARACTERISTICS OF FLOW 5measurement) to the theoretical flow (calculated from a mathematical model pub-lished by the manufacturer) defines the meters discharge coefficient.A flow coefficient KCD(or

33、KCDfactor) is sometimes used that effectively combinesCd with the geometric and conversion parameters. The KCDfactor = Q /( ) where Qis in gallons per minute and P is in inches of water.PThis page intentionally blank.7AWWA MANUALM33Chapter 2Types of FlowmetersThe most common flowmeters currently use

34、d in the water industry are described inthis chapter. Table 2-1 lists several categories of flowmeters. This table also shows thetypical service sizes for each application. This manual describes the more commontypes of flowmeters used in water treatment and custody-transfer applications. Infor-matio

35、n on other meters can be obtained from AWWA manual of water supply prac-tices, M6, Water MetersSelection, Installation, Testing and Maintenance, and fromthe respective manufacturers. Table 2-1 lists various types of meters used in the waterindustry. Meters shown in bold letters are commonly used in

36、water treatment and cus-tody-transfer applications. (Custody transfer is a situation in which water is sold to awholesale service customer at one or more major points of delivery for resale to indi-vidual retail customers within the wholesale customers service area.) Criteria for theselection of flo

37、wmeters for various applications are provided in chapter 3.Meters described in this manual are highlighted in bold letters in Table 2-1.Displacement, multijet, singlejet, compound, and fire service meters are described inAWWA Manual M6. Several terms are used to describe flowmeter characteristics an

38、dare defined as follows:Accuracy. Accuracy is the degree to which a measured value matches theactual value. The term is typically expressed as a percentage variation of the mea-sured value from the actual value. A flowmeter that generates a measured valuebetween 99 percent and 101 percent of the act

39、ual value has an accuracy of 1 percent.This method of stating accuracy is commonly referred to as percent of reading.*Repeatability. Repeatability is a measure of the flowmeters ability todetermine identical rates of flow by moving back to a previously indicated rateafter deviating from it. Repeatab

40、ility is the maximum expected variation,expressed as a percentage, for the rate of flow. It is also represented as a percent-age such as 0.25 percent.*An alternate way of stating accuracy is percent of full scale. Only when the measured variable is at the full-scale value will this method of stating

41、 accuracy be equivalent to the percent of reading method. When accuracy is stated as percent of full scale, the error percentage is predicted to increase as the measured value decreases. Accuracy stated as a percent of full scale may be con-verted to accuracy as a percent of reading by the following

42、 example: if a flowmeter has an accu-racy of 0.5 percent of full scale, then that accuracy at 50 percent of scale will be (0.5%) (100/50) = 1% of measured value, and at 10 percent of scale, it will be (0.5%) (100/10) = 10% of mea-sured value. If accuracy is stated without indicating of reading or of

43、 full scale, it is normally assumed to be of full scale until the statement can be verified.8 FLOWMETERS IN WATER SUPPLYRangeability. Rangeability is the ratio of the maximum to minimum flowrates at which a flowmeter maintains its accuracy. It is commonly represented as aratio, such as 20:1.Size ran

44、ge. Size range is the flowmeter sizes that are commonly available fora particular type of flowmeter. Other sizes may be available by special request.Relative head loss. Head loss is the drop of pressure in the piping systemcaused by the flowmeter. Relative head loss is the head loss of a type of flo

45、wmetercompared with other flowmeters.In the discussion of different flowmeter types, a number of numerical values arepresented for accuracy, repeatability, and rangeability. These values have beenreported by one or more manufacturers of the meter type, based on their laboratorytesting. The authors o

46、f this document cannot make any warranty as to the accuracy ofthis data. It is included in the interest of providing useful background for the reader.In any application, for any meter type, it is incumbent on the user to determine whatTable 2-1 Types of flowmeters for the water industryUsual Size Ra

47、ngeType in. (mm)1. Displacement Metersa. Nutating disc1/22 (1350)b. Oscillating piston1/22 (1350)c. Rotary vane1/22 (1350)2. Nondisplacement Metersa. VelocityMultijet5/82 (1550)Magnetic pick-up turbine1/412 (6300)Mechanical register turbine3/420 (20400)Propeller 272 (501,800)Proportional 312 (80300)

48、Singlejet 11/26 (40150)b. Differential pressureFixed opening, variable differentialOrifice 1 ( 25)Venturi, flow nozzle, flow tube 1120 (253,000)Pitot tube unlimitedVariable opening, fixed differential1/1612 (1300)c. Electronic VelocityElectromagnetic (mag)1/10120 (21/23,000)Ultrasonic (transit-time)

49、1/4360 (69,000)Insertable electromagnetic (mag) (averaging) 4120 (1003,000)Vortex 110 (25250)d. Level measurementWeir, parshall flume (Suitable for open channel flow only)3. Compound Metersa. Standard compound 28 (50200)b. Fire service 312 (80300)TYPES OF FLOWMETERS 9their accuracy needs are, and whether their conditions of installation fall within therange represented by any manufacturers data, and for determining if their specificinstallation requirements may require add