شیرهای پروانه‌ای - تجزیه و تحلیل گشتاور، افت فشار و کاویتاسیون - راهنمای شیوه‌های تأمین آب، M49

In this book water operators receive complete information about the versatile butterfly valve in drinking water service. Engineers and technicians will gain a basic understanding of calculations for operating torque, head loss, and cavitation. Coverage includes valve design, torque, head loss, cavitation, testing, noise, and vibration. Front Matter 1 List of Figures 3 List of Tables 5 Preface 6 Table of Contents 7 1. Introduction 9 1.1 Scope 10 1.2 Discussion of Torque Calculations 10 1.3 Uncertainty and Diameter Assumptions 11 1.4 Discussion of Head Loss, Choking, and Cavitation 12 1.5 Butterfly Valve Design 13 1.6 System Conditions 15 1.7 Nomenclature 16 References 21 2. Valve Torque 23 2.1 Definitions 23 2.1.1 Flow Coefficients, C_v and K or K_v 23 2.1.2 Torque Coefficients, C_t and C_t theta 25 2.1.3 Bearing Torque, T_b , and T_b theta 25 2.1.4 Bearing Coefficient of Friction, C_f 25 2.1.5 Seating and Unseating Torque, T_s and T_us 26 2.1.6 Differential Pressure, Delta P 26 2.1.7 Maximum System Flow Rate or Velocity, V_MAX 26 2.1.8 Disc Geometry 27 2.1.9 Shaft Orientation 27 2.1.10 Flow Direction through the Valve 27 2.1.11 Sign Conventions 27 2.2 Torque Components 28 2.3 Seating Torque 32 2.4 Packing and Hub Torque 34 2.5 Bearing Torque 36 2.6 Center of Gravity Torque 38 2.7 Hydrostatic Torque 39 2.8 Dynamic Torque 41 2.9 Shaft Offset or Eccentricity Torque 44 2.10 Other Components of Torque 47 2.10.1 Bearing Torque Caused by Disc and Shaft Assembly Weight, T_bw 47 2.10.2 Center of Gravity Torque for Installed Orientation, T_cg theta 49 2.10.3 Hydrostatic Torque for Installed Orientation, T_h 51 2.10.4 Buoyancy Torque 52 2.10.5 Thrust Bearing Torque 52 2.10.6 Upstream Flow Disturbances Flow and Asymmetric Flow Distributions 52 2.11 System Characteristics 52 2.12 System Analysis and Example Calculations 53 2.13 Constant Head Source Methodology 54 2.14 Constant Head Source - Example 56 2.15 Variable Head Source Methodology 60 References 61 3. Valve Head Loss 62 3.1 Definitions 62 3.2 Head Loss Calculations 64 3.3 Reducer Installations 65 3.4 Energy Calculatlons 66 3.4.1 Energy Calculation - Example 67 References 67 4. Valve Cavitation 68 4.1 Definitions 68 4.2 Predicting Cavitation 69 4.3 Methods for Reducing Cavitation 73 References 73 5. Valve Testing 74 5.1 Testing Requirements 74 5.2 Flow Test Procedure 76 5.3 Seating/Unseating Torque Test Procedure 80 References 82 6. Valve Applications 83 6.1 Actuator Sizing 83 6.1.1 Manual Actuator Sizing 83 6.1.2 Cylinder Actuator Sizing 84 6.1.3 Electric Actuator Sizing and Switch Settings 84 6.2 Extended Bonnet Installanon 84 6.3 Effects of Pipe Instalations 86 6.3.1 Flow and Pressure Direction 86 6.3.2 Upstream Elbow or Branch Tee 86 6.3.3 Upstream Valve 86 6.3.4 Free Inlet or Discharge 86 6.4 Typical Range of Coefficients 87 6.4.1 Bearing Friction 88 6.4.2 Packing Friction 88 6.4.3 Seating Coefficients 88 6.4.4 Flow Coefficients 89 6.4.5 Dynamic Torque Coefficients 89 6.5 Cautions 89 6.5.1 Actuator Removal 89 6.5.2 Throttling Flow 90 6.6 Summary 91 References 92 Index 93 A 93 B 93 C 94 D 95 E 96 F 96 H 98 I 98 L 98 M 98 N 99 O 99 P 99 R 100 S 100 T 101 U 102 V 102 W 103 Updated from the 2001 edition, this new manual has expanded equations for eccentricity torque, added torque sign conventions and double offset disc design variables. Water operators receive complete information about the versatile butterfly valve in drinking water service. Engineers and technicians will gain a basic understanding of calculations for operating torque, head loss, and cavitation. Coverage includes valve design, torque, head loss, cavitation, testing, noise, and vibration. (Replaces ISBN 9781583210413) Content: Front Matter • List of Figures • List of Tables • Preface • Table of Contents 1. Introduction 2. Valve Torque 3. Valve Head Loss 4. Valve Cavitation 5. Valve Testing 6. Valve Applications Index Covers recommended practices, calculations, and data for correctly specifying and using butterfly valves in any water piping system.