1、Butterfly Valves: Torque, Head Loss, and Cavitation AnalysisAWWA MANUAL M49Second EditionCopyright 2012 American Water Works Association. All Rights Reserved.Manual of Water Supply Practices M49, Second EditionButterfly Valves: Torque, Head Loss, and Cavitation AnalysisCopyright 2001, 2012, American
2、 Water Works AssociationAll rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information or retrieval system, except in the form of brief excerpts or quotations for review purpo
3、ses, without the written permission of the publisher.DisclaimerThe authors, contributors, editors, and publisher do not assume responsibility for the validity of the content or any consequences of its use. In no event will AWWA be liable for direct, indirect, special, incidental, or consequential da
4、mages arising out of the use of information presented in this book. In particular, AWWA will not be responsible for any costs, including, but not limited to, those incurred as a result of lost revenue. In no event shall AWWAs liability exceed the amount paid for the purchase of this book.AWWA Public
5、ations Manager: Gay Porter De NileonProject Manager/Copy Editor: Melissa ValentineProduction Editor: Cheryl ArmstrongManuals Specialist: Molly BeachLibrary of Congress Cataloging-in-Publication DataBosserman, Bayard E.Butterfly valves : torque, head loss, and cavitation analysis / Bayard E. Bosserma
6、n, Amzad Ali, Irving M. Schuraytz. - 2nd ed.p. cm. - (AWWA manual ; M49)Includes bibliographical references and index.ISBN 978-1-58321-879-2 (alk. paper)1. Water-pipes-Valves. 2. Butterfly valves. 3. Water-pipes-Hydrodynamics. I. Ali, Amzad. II. Schuraytz, Irving M. III. Title. TD491.B67 2012621.84-
7、dc232012010349Printed on recycled paperAmerican Water Works Association6666 West Quincy AvenueDenver, CO 80235-3098ISBN 978-1-58321-879-2Copyright 2012 American Water Works Association. All Rights Reserved.ContentsList of Figures, vList of Tables, viiForeword, ixAcknowledgments, xiChapter 1 Introduc
8、tion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Scope, 2Discussion of Torque Calculations, 2Uncertainty and Diameter Assumptions, 3Discussion of Head Loss, Choking, and Cavitation, 4Butterfly
9、 Valve Design, 5System Conditions, 7Nomenclature, 8References, 13Chapter 2 Valve Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Definitions, 15Torque Components, 20Seating Torque, 24Packing a
10、nd Hub Torque, 26Bearing Torque, 28Center of Gravity Torque, 30Hydrostatic Torque, 31Dynamic Torque, 33Shaft Offset or Eccentricity Torque, 36Other Components of Torque, 39System Characteristics, 44System Analysis and Example Calculations, 45Constant Head Source Methodology, 46Constant Head SourceEx
11、ample, 48Variable Head Source Methodology, 52References, 53Chapter 3 Valve Head Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55Definitions, 55Head Loss Calculations, 57Reducer Installations, 58Energy Cal
12、culations, 59References, 60Chapter 4 Valve Cavitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61Definitions, 61Predicting Cavitation, 62Methods for Reducing Cavitation, 66References, 66iiiCopyright 2012
13、American Water Works Association. All Rights Reserved.Chapter 5 Valve Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67Testing Requirements, 67Flow Test Procedure, 69Seating/Unseating Torque Tes
14、t Procedure, 73References, 75Chapter 6 Valve Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Actuator Sizing, 77Extended Bonnet Installation, 78Effects of Pipe Installations, 80Typical Range of Coeffic
15、ients, 81Cautions, 84Summary, 85References, 86Index, 87List of Manuals, 91ivCopyright 2012 American Water Works Association. All Rights Reserved.vFiguresFigure 1-1 Typical butterfly valve flow, differential pressure, cavitation, and choking graphical explanation . . . . . . . . . . . . . . . . . . .
16、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Figure 1-2 Typical butterfly valve construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Figure 1-3 Free discharge and reservoir inlet installations of butterfly valves . .
17、 . . . . .7Figure 2-1 Valve disc, port, and pipe diameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Figure 2-2 Constant and variable head source graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Figure 2-3 Basic dis
18、c design geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Figure 2-4 Horizontal valve shaft in a horizontal pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Figure 2-5 Seat-side and shaft-side
19、 flow orientations with single- and double-offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21Figure 2-6 Active torque sign convention, positive value tends to close the valve . . . . . . . . . . .
20、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Figure 2-7 Dynamic torque (Td) and bearing torque (Tb) during valve closure . . . . .23Figure 2-8 Multiple-pump installation . . . . . . . . . . . . . . . .
21、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Figure 2-9 Seating torque (Ts) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Figure 2-10 Packing and hub seal torque (Tp) .
22、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Figure 2-11 Bearing torque (Tb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Figure 2-12 Center of gravity
23、torque (Tcg) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Figure 2-13 Hydrostatic torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Figure
24、 2-14 Dynamic torque (Td) for a symmetrical disc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Figure 2-15 Dynamic torque coefficient (Ct) graph for butterfly valves with symmetrical and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25、 . . . . . . . . . . . . . . . . . . .35Figure 2-16 Dynamic torque (Td) for a butterfly valve with symmetric and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35Figure 2-17 T
26、otal opening torque (Tto) for a 20-in. (500 mm) to 30-in. (750 mm) butterfly valve with symmetric and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36Figure 2-18 Total opening torque (Tto) for a 78-in. (2,000 mm) to 96-in. (2,400 mm) butterfly valve with symmetric and off
27、set . . . . . . . . . . . . . . . . . . . . . .36Figure 2-19 Total closing torque (Ttc) for a 20-in. (500 mm) to 30-in. (750 mm) butterfly valve with symmetric and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37Figure 2-20 Total closing torque (Ttc) for a 78-in. (2,000 m
28、m) to 96-in.(2,400 mm) butterfly valve with symmetric and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38Figure 2-21 Shaft offset or eccentricity torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38Figure 2-22 Bearing
29、 torque caused by disc and shaft(s) weight orientation angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Figure 2-23 Center of gravity torque pipe angle definition . . .
30、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Figure 2-24 Valve shaft and pipe orientation from vertical axis for center of gravity torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31、. . 42Figure 2-25 Valve shaft and pipe orientation from vertical axis for hydrostatic and bearing torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45Figure 2-26 Relationship between velocity and head loss in
32、 butterfly valves . . . . . . . . .46Figure 2-27 Example torque calculation summary graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51Figure 3-1 Reducer geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33、 . . . . . . . . . . . . .59Figure 4-1 Cavitation zone downstream of a butterfly valve disc . . . . . . . . . . . . . . . . . . . . . . .62Figure 4-2 Typical cavitation index levels and acceleration readings . . . . . . . . . . . . . . . .63Copyright 2012 American Water Works Association. All Rights
34、 Reserved.viFigure 4-3 Flow rate and acceleration readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64Figure 4-4 Typical cavitation index values for a 6-in. (150-mm) butterfly valve . . .65Figure 5-1 Basic flow test system . . . . . . . . . . . . . .
35、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68Figure 5-2 Butterfly valve test installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69Figure 6-1 Typical actuator torque characteristi
36、cs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79Figure 6-2 Actuator sizing characteristics graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79Figure 6-3 Vertical elbow upstream of a butterfly valve . . . . . . . . .
37、. . . . . . . . . . . . . . . . . . . . . . . . . .81Figure 6-4 Typical butterfly valve inherent flow characteristic . . . . . . . . . . . . . . . . . . . . . . . . .81Figure 6-5 Typical butterfly valve symmetric, shaft side, and seat side Ct. . . . . . . . . .84Figure 6-6 Typical butterfly valve sy
38、mmetric low, mean, and high Ct. . . . . . . . . . . . . . . .84Figure 6-7 Typical butterfly valve single-offset shaft side low, mean, and high Ct. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
39、 . . . . . .85Figure 6-8 Typical butterfly valve single-offset seat side low, mean, and high Ct. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85Copyright 2012 American Water Works
40、Association. All Rights Reserved.viiTablesTable 1-1 Torque component category 2Table 1-2 Nomenclature, terms, and symbols 8Table 1-3 Conversion of units13Table 2-1 Calculation data for constant head source example51Table 6-1 Typical bearing friction coefficients.82Table 6-2 Typical packing coefficie
41、nts .82Table 6-3 Typical seating coefficients .82Table 6-4 Typical full open flow coefficients, CVand KV.83Copyright 2012 American Water Works Association. All Rights Reserved.This page intentionally blank.Copyright 2012 American Water Works Association. All Rights Reserved.PrefaceThe purpose of thi
42、s manual is to present a recommended method for calculating oper-ating torque, head loss, and cavitation for butterfly valves typically used in water works service. It is a discussion of recommended practice, not an American Water Works Association (AWWA) standard. The text provides guidance on gene
43、rally avail-able methods for using butterfly valves as well as their cavitation, flow, and torque characteristics. Questions about specific situations or applicability of specific valves and values should be directed to the manufacturers or suppliers. Information in this manual is useful for technic
44、ians and engineers who want a basic understanding of the calculations associated with the use and specification of butterfly valves. The valve torque, flow, and cavitation coefficients given are typical but generic values covering a variety of products. Actual flow, cavitation, or torque coefficient
45、s for a particular man-ufacturers valve should be used in calculations for a specific valve and application to obtain the highest calculation accuracy. The history of this manual is related to that of American National Standards Institute ANSI/AWWA C504, Standard for Rubber-Seated Butterfly Valves.
46、Until the 1994 edition, ANSI/AWWA C504 included Appendix A, which described a recom-mended method of calculating torques for butterfly valves. This appendix was deleted from the 1994 and subsequent editions of the standard for several reasons. The AWWA Standards Council directed that standards docum
47、ents should not contain appendixes; appendix text should either be moved to the main body of the standard or be made into a separate, stand-alone document. Members of the committee for ANSI/AWWA C504 at the time were concerned that the existing text of Appendix A no longer represented the current st
48、ate of knowledge concerning methods for calculating torques for butterfly valves. In 1993, a subcommittee was established to rewrite Appendix A as a separate manual incorporating the state-of-the-art theory for calculating torque and head-loss values for butterfly valves. This second edition of the
49、manual expanded the intro-duction and some equations, added torque sign conventions, added double offset disc design variables and calculations, added equations for eccentricity torque, added met-ric units and equivalents, consolidated the nomenclature, and corrected some errors. Manual M49 refers to AWWA standards available for purchase from the AWWA Bookstore. Manufacturers graciously provided valve illustrations and other documen-tation. AWWA does not endorse any manufacturers products, and the names of the manufacturers have been removed from the
