Butterfly Valves: Torque, Head Loss, And Cavitation Analysis

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This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.Butterfly Valves:Torque, Head Loss,and Cavitation AnalysisAWWA MANUAL M49Second Edition Copyright 2012 American Water Works Association. All Rights Reserved.

This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.Manual of Water Supply Practices — M49, Second EditionButterfly Valves: Torque, Head Loss, and Cavitation AnalysisCopyright 2001, 2012, American Water Works AssociationAll rights reserved. No part of this publication may be reproduced 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, editors, and publisher do not assume responsibility for the validity of thecontent or any consequences of its use. In no event will AWWA be liable for direct, indirect, special,incidental, or consequential damages arising out of the use of information presented in this book. Inparticular, AWWA will not be responsible for any costs, including, but not limited to, those incurred asa result of lost revenue. In no event shall AWWA’s liability exceed the amount paid for the purchase ofthis book.AWWA Publications 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. Bosserman, Amzad Ali, IrvingM. 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 2012621.8'4--dc23 2012010349American Water Works Association6666 West Quincy AvenueDenver, CO 80235-3098ISBN 978-1-58321-879-2Printed on recycled paperCopyright 2012 American Water Works Association. All Rights Reserved.

This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.ContentsList of Figures, vList of Tables, viiForeword, ixAcknowledgments, xiChapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Scope, 2Discussion of Torque Calculations, 2Uncertainty and Diameter Assumptions, 3Discussion of Head Loss, Choking, and Cavitation, 4Butterfly Valve Design, 5System Conditions, 7Nomenclature, 8References, 13Chapter 2 Valve Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Definitions, 15Torque Components, 20Seating Torque, 24Packing and 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 Source—Example, 48Variable Head Source Methodology, 52References, 53 Chapter 3 Valve Head Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55Definitions, 55Head Loss Calculations, 57Reducer Installations, 58Energy Calculations, 59References, 60Chapter 4 Valve Cavitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Definitions, 61Predicting Cavitation, 62Methods for Reducing Cavitation, 66References, 66iiiCopyright 2012 American Water Works Association. All Rights Reserved.

This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.Chapter 5 Valve Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67Testing Requirements, 67Flow Test Procedure, 69Seating/Unseating Torque Test Procedure, 73References, 75Chapter 6 Valve Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Actuator Sizing, 77Extended Bonnet Installation, 78Effects of Pipe Installations, 80Typical Range of Coefficients, 81Cautions, 84Summary, 85References, 86Index, 87List of Manuals, 91 ivCopyright 2012 American Water Works Association. All Rights Reserved.

This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.FiguresFigure 1-1Figure 1-2Figure 1-3Figure 2-1Figure 2-2Figure 2-3Figure 2-4Figure 2-5Typical butterfly valve flow, differential pressure, cavitation, andchoking graphical explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Typical butterfly valve construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Free discharge and reservoir inlet installations of butterfly valves . . . . . . . 7Figure 2-26Figure 2-27Valve disc, port, and pipe diameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Constant and variable head source graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Basic disc design geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Horizontal valve shaft in a horizontal pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Seat-side and shaft-side flow orientations with single- anddouble-offset discs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Active torque sign convention, positive value tends to closethe valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Dynamic torque (Td) and bearing torque (Tb) during valve closure . . . . . 23Multiple-pump installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Seating torque (Ts) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Packing and hub seal torque (Tp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Bearing torque (Tb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Center of gravity torque (Tcg) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Hydrostatic torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Dynamic torque (Td) for a symmetrical disc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Dynamic torque coefficient (Ct) graph for butterfly valves withsymmetrical and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Dynamic torque (Td) for a butterfly valve with symmetric andoffset discs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Total opening torque (Tto) for a 20-in. (500 mm) to 30-in. (750 mm)butterfly valve with symmetric and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Total opening torque (Tto) for a 78-in. (2,000 mm) to 96-in.(2,400 mm) butterfly valve with symmetric and offset . . . . . . . . . . . . . . . . . . . . . . 36Total closing torque (Ttc) for a 20-in. (500 mm) to 30-in. (750 mm)butterfly valve with symmetric and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Total closing torque (Ttc) for a 78-in. (2,000 mm) to 96-in.(2,400 mm)butterfly valve with symmetric and offset discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Shaft offset or eccentricity torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Bearing torque caused by disc and shaft(s) weight orientationangles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Center of gravity torque pipe angle definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Valve shaft and pipe orientation from vertical axis for center ofgravity torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Valve shaft and pipe orientation from vertical axis for hydrostaticand bearing torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Relationship between velocity and head loss in butterfly valves . . . . . . . . . 46Example torque calculation summary graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51Figure 3-1Reducer geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Figure 4-1Figure 4-2Cavitation zone downstream of a butterfly valve disc . . . . . . . . . . . . . . . . . . . . . . . 62Typical cavitation index levels and acceleration readings . . . . . . . . . . . . . . . . 63Figure 2-6Figure 2-7Figure 2-8Figure 2-9Figure 2-10Figure 2-11Figure 2-12Figure 2-13Figure 2-14Figure 2-15Figure 2-16Figure 2-17 Figure 2-18Figure 2-19Figure 2-20Figure 2-21Figure 2-22Figure 2-23Figure 2-24Figure 2-25vCopyright 2012 American Water Works Association. All Rights Reserved.

This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.Figure 4-3Figure 4-4Flow rate and acceleration readings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Typical cavitation index values for a 6-in. (150-mm) butterfly valve . . . 65Figure 5-1Figure 5-2Basic flow test system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68Butterfly valve test installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Figure 6-1Figure 6-2Figure 6-3Figure 6-4Figure 6-5Figure 6-6Figure 6-7Typical actuator torque characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Actuator sizing characteristics graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Vertical elbow upstream of a butterfly valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Typical butterfly valve inherent flow characteristic . . . . . . . . . . . . . . . . . . . . . . . . . 81Typical butterfly valve symmetric, shaft side, and seat side CtU . . . . . . . . . . 84Typical butterfly valve symmetric low, mean, and high CtU . . . . . . . . . . . . . . . . 84Typical butterfly valve single-offset shaft side low, mean, andhigh CtU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Typical butterfly valve single-offset seat side low, mean, andhigh CtU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Figure 6-8 viCopyright 2012 American Water Works Association. All Rights Reserved.

This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.TablesTable 1-1Table 1-2Table 1-3Torque component category . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Nomenclature, terms, and symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Conversion of units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Table 2-1Calculation data for constant head source example. . . . . . . . . . . . . . . . 51Table 6-1Table 6-2Table 6-3Table 6-4Typical bearing friction coefficients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Typical packing coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Typical seating coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Typical full open flow coefficients, CV and KV . . . . . . . . . . . . . . . . . . . . . 83 viiCopyright 2012 American Water Works Association. All Rights Reserved.

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This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.PrefaceThe purpose of this manual is to present a recommended method for calculating operating torque, head loss, and cavitation for butterfly valves typically used in waterworks service. It is a discussion of recommended practice, not an American WaterWorks Association (AWWA) standard. The text provides guidance on generally available methods for using butterfly valves as well as their cavitation, flow, and torquecharacteristics. Questions about specific situations or applicability of specific valvesand values should be directed to the manufacturers or suppliers. Information in thismanual is useful for technicians and engineers who want a basic understanding of thecalculations associated with the use and specification of butterfly valves. The valvetorque, flow, and cavitation coefficients given are typical but generic values covering avariety of products. Actual flow, cavitation, or torque coefficients for a particular manufacturer’s valve should be used in calculations for a specific valve and application toobtain the highest calculation accuracy.The history of this manual is related to that of American National StandardsInstitute ANSI/AWWA C504, Standard for Rubber-Seated Butterfly Valves. Untilthe 1994 edition, ANSI/AWWA C504 included Appendix A, which described a recommended method of calculating torques for butterfly valves. This appendix was deletedfrom the 1994 and subsequent editions of the standard for several reasons. The AWWAStandards Council directed that standards documents should not contain appendixes;appendix text should either be moved to the main body of the standard or be made intoa separate, stand-alone document. Members of the committee for ANSI/AWWA C504at the time were concerned that the existing text of Appendix A no longer representedthe current state of knowledge concerning methods for calculating torques for butterflyvalves. In 1993, a subcommittee was established to rewrite Appendix A as a separatemanual incorporating the state-of-the-art theory for calculating torque and head-lossvalues for butterfly valves. This second edition of the manual expanded the introduction and some equations, added torque sign conventions, added double offset discdesign variables and calculations, added equations for eccentricity torque, added metric units and equivalents, consolidated the nomenclature, and corrected some errors.Manual M49 refers to AWWA standards available for purchase from the AWWABookstore. Manufacturers graciously provided valve illustrations and other documentation. AWWA does not endorse any manufacturer’s products, and the names of themanufacturers have been removed from the material provided. ixCopyright 2012 American Water Works Association. All Rights Reserved.

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This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.AcknowledgmentsThe AWWA Standards Council Committee for Butterfly Valves developed thismanual. The members listed below served on the committee at the time the manualwas approved.B.E. Bosserman, Chair, Mission Viejo, Calif.User MembersA. Ali, ADA Consulting Ltd., Surrey, B.C.S. Carpenter, San Diego County Water Authority, Escondido, Calif.D.W. Coppes, Massachusetts Water Resources Authority, Southborough, Mass.I.M. Schuraytz, Southfield, Mich.D.C. Stone, Denver Water, Denver, Colo.S.Y. Tung, City of Houston, Houston, TexasGeneral Interest MembersM.D. Bennett, MWH, Cleveland, OhioB.E. Bosserman, Mission Viejo, Calif.M.L. Damoth, CH2M Hill, Redding, Calif.F.L. Hinker, Santa Rosa, N.M.M.C. Johnson, Utah State University, Water Research Lab, Logan, UtahT. Jordan, HDR Inc., Denver, Colo.T.J. McCandless,† American Water Works Association, Denver, Colo.W. Rahmeyer,* Utah State University, Water Research Lab, Logan, UtahR.A. Ward, Dufresne Group, Windsor, Vt.H.H. Wasserman, Wilton, Conn.G.E. Laverick, Underwriters Laboratories Inc., Northbrook, Ill. Producer MembersA. Abuelle, Mueller Company, Aurora, Ill.J.V. Ballun, Val-Matic Valve & Manufacturing Corp., Elmhurst, Ill.J.R. Dernovsek, Bray Controls, Houston, TexasL.W. Fleury,* Mueller Co., Cranston, R.I.Steven Flora, M&H Valve, Cedar Bluff, Ala.T.A. Hartman, Hartman Valve Corp., St. Louis, Mo.J.R. Holstrom,* Sub-committee chair, Val-Matic Valve & Manufacturing Corp.,Elmhurst, Ill.A.W. Libke, DeZURIK, Sartell, Minn.T.J. McAndrew, Rodney Hunt Company, Orange, Mass.* Alternate† LiaisonxiCopyright 2012 American Water Works Association. All Rights Reserved.

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This is a preview of "AWWA M49-2012". Click here to purchase the full version from the ANSI store.AWWA MANUALChapterM491IntroductionTorque, head loss, and cavitation are important considerations in the selection andsizing of butterfly valves in water systems. Butterfly valve components must be able towithstand the forces and torques generated during use, and the actuator must operateand seat the valve. The head loss developed across any valve adds to the energy costs ofa pumping system. Cavitation can damage a valve or adjacent piping if not controlled.The topics in this introductory chapter include an explanation of basic butterflyvalve design elements and their role in predicting torque, head loss, and cavitation.Valve torque is calculated to allow proper actuator sizing and to provide assurance that the valve components can withstand the internal forces produced by flowingwater and fluid pressure. Head loss characteristics must be known to predict torque,and system designers also use these data to calculate pump head requirements and toevaluate the energy costs associated with the head loss across the valve in pumpingapplications. Cavitation is analyzed to prevent undesirable sound and vibration and toprevent damage to the valve and adjacent piping.Torque, head loss, and cavitation vary with a valve’s angle of opening. Thesecharacteristics also depend on the geometry of the valve body and disc and on thecharacteristics of the system in which the

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