control valves
CONTROL VALVE HANDBOOK Third Edition FISHER CONTROLS INTERNATIONAL, INC Marshalltown, Iowa 50158 U.S.A. Cernay 68700 France Sao Paulo 05424 Brazil Singapore 128461 ii Copyright 1965, 1998, 1999, Reprinted in 1999 and 2001. Fisher Controls International, Inc. All Rights Reserved. Fisher, ENVIRO-SEAL and FIELDVUE are marks owned by Fisher Controls International, Inc., a business of Emerson Process Management. The Emerson logo is a trademark and service mark of Emerson Electric Co. All other marks are the property of their respective owners. Printed in U.S.A. iii Preface to Third Edition Control valves are an increasingly vital component of modern manufacturing around the world. Well–selected and maintained control valves increase efficiency, safety, profitability, and ecology. The Control Valve Handbook has been a primary reference for more than 30 years. This third edition is a complete revision and update that includes vital information on control valve performance and the latest technologies. D Chapter 1 offers an introduction to control valves including definitions for common control valve and instrumentation terminology. D Chapter 2 develops the vital topic of control valve performance. D Chapter 3 covers valve and actuator types. D Chapter 4 describes digital valve controllers, analog positioners, boosters, and other control valve accessories. D Chapter 5 is a comprehensive guide to selecting the best control valve for an application. D Chapter 6 covers the selection and use of special control valves. D Chapter 7 covers desuperheaters, steam conditioning valves, and turbine bypass systems. D Chapter 8 offers typical control valve installation and maintenance proce- dures. D Chapter 9 includes information on control valve standards and approval agencies throughout the world. D Chapter 10 offers useful tables of engineering reference data. D Chapter 11 includes piping reference data. D Chapter 12 is a handy resource for common conversions. The Control Valve Handbook is both a textbook and a reference on the strongest link in the control loop: the control valve and its accessories. This book includes exten- sive and proven knowledge from leading experts in the process control field includ- ing contributions from the ISA and the Crane Company. iv v Table of Contents Chapter 1. Introduction to Control Valves 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Is A Control Valve? 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Process Control Terminology 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sliding-Stem Control Valve Terminology 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rotary-Shaft Control Valve Terminology 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Valve Functions and Characteristics Terminology 16. . . . . . . . . . . . . Other Process Control Terminology 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 2. Control Valve Performance 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Process Variability 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dead Band 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Actuator-Positioner Design 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Response Time 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Type And Characterization 31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Sizing 36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Economic Results 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary 39. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 3. Valve and Actuator Types 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Valves 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Globe Valves 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single-Port Valve Bodies 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Balanced-Plug Cage-Style Valve Bodies 43. . . . . . . . . . . . . . . . . . . . . . High Capacity, Cage-Guided Valve Bodies 44. . . . . . . . . . . . . . . . . . . . Port-Guided Single-Port Valve Bodies 44. . . . . . . . . . . . . . . . . . . . . . . . . Double-Ported Valve Bodies 44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Three-Way Valve Bodies 45. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table of Contents vi Rotary Valves 45. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Butterfly Valve Bodies 45. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V-Notch Ball Control Valve Bodies 46. . . . . . . . . . . . . . . . . . . . . . . . . . . . Eccentric-Disk Control Valve Bodies 47. . . . . . . . . . . . . . . . . . . . . . . . . . Eccentric-Plug Control Valve Bodies 47. . . . . . . . . . . . . . . . . . . . . . . . . . Control Valve End Connections 48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Screwed Pipe Threads 48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bolted Gasketed Flanges 48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Welding End Connections 49. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Body Bonnets 49. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extension Bonnets 50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bellows Seal Bonnets 51. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Valve Packing 52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PTFE V-Ring 52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laminated and Filament Graphite 52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . USA Regulatory Requirements for Fugitive Emissions 53. . . . . . . . . . . . . Characterization of Cage-Guided Valve Bodies 56. . . . . . . . . . . . . . . . . . . . . . Characterized Valve Plugs 58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Plug Guiding 59. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Restricted-Capacity Control Valve Trim 60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Actuators 60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diaphragm Actuators 61. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Piston Actuators 61. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electrohydraulic Actuators 63. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manual Actuators 63. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rack and Pinion Actuators 64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electric Actuators 64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 4. Control Valve Accessories 65. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Positioners 65. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other Control Valve Accessories 67. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Limit Switches 69. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solenoid Valve Manifold 69. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Supply Pressure Regulator 70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pneumatic Lock-Up Systems 70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fail-Safe Systems for Piston Actuators 70. . . . . . . . . . . . . . . . . . . . . . . . . . Electro-Pneumatic Transducers 70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electro-Pneumatic Valve Positioners 72. . . . . . . . . . . . . . . . . . . . . . . . . . . . PC Diagnostic Software 72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 5. Control Valve Selection 73. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Body Materials 74. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Designations for the High Nickel Alloys 75. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure-Temperature Ratings for Standard Class 76. . . . . . . . . . . . . . . . . . . ASTM A216 Grade WCC Valves 76. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table of Contents vii ASTM A217 Grade WC9 Valves 77. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM A217 Grade C5 Valves 78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM A351 Grade CF3 Valves 79. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM A351 Grade CF8M and ASTM A479 Grade UNS S31700 Valves 80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure-Temperature Ratings for ASTM A216 Cast Iron Valves 82. . . . . . . Pressure-Temperature Ratings for ASTM B61 and B62 Cast Bronze Valves 83. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class Designation and PN Numbers 83. . . . . . . . . . . . . . . . . . . . . . . . . . . . Face–to Face Dimensions for Flanged Globe–Style Control Valves 85. . . . . Face–to–Face Dimensions for Buttweld–End Globe–Style Control Valves 87. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Face–to–Face Dimensions for Socket Weld–End Globe–Style Control Valves 88. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Face-to-Face Dimensions for Screwed-End Globe-Style Control Valves 89. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Face-to-Centerline Dimensions for Raised Face Globe-Style Angle Control Valves 89. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Face-to-Face Dimensions for Separable Flanged Globe-Style Control Valves 89. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Face-to-Face Dimensions for Flangeless, Partial-Ball Control Valves 90. . . Face-to-Face Dimensions for Single Flange (Lug-Type) and Flangeless (Wafer-Type) Butterfly Control Valves 90. . . . . . . . . . . . . . . . . . . . Face-to-Face Dimensions for High Pressure Butterfly Valves with Offset Design 91. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wear & Galling Resistance Chart Of Material Combinations 91. . . . . . . . . . . Control Valve Seat Leakage Classifications 92. . . . . . . . . . . . . . . . . . . . . . . . . Class VI Maximum Seat Leakage Allowable 93. . . . . . . . . . . . . . . . . . . . . . . . Typical Valve Trim Material Temperature Limits 93. . . . . . . . . . . . . . . . . . . . . . Service Temperature Limitations for Elastomers 94. . . . . . . . . . . . . . . . . . . . . Ambient Temperature Corrosion Information 95. . . . . . . . . . . . . . . . . . . . . . . Elastomer Information 100. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fluid Compatibility 103. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Valve Flow Characteristics 107. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flow Characteristics 107. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Selection of Flow Characteristic 108. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Sizing 109. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sizing Valves for Liquids 109. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Abbreviations and Terminology 111. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equation Constants 112. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determining Fp, the Piping Geometry Factor 113. . . . . . . . . . . . . . . . . . . . . . . Determining qmax (the Maximum Flow Rate) or DPmax (the Allowable Sizing Pressure Drop) 114. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determining qmax (the Maximum Flow Rate) 114. . . . . . . . . . . . . . . . . . . . . Determining DPmax (the Allowable Sizing Pressure Drop) 114. . . . . . . . . . . Liquid Sizing Sample Problem 116. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sizing Valves for Compressible Fluids 118. . . . . . . . . . . . . . . . . . . . . . . . . . . . Table of Contents viii Determining xTP, the Pressure Drop Ratio Factor 120. . . . . . . . . . . . . . . . . . . Compressible Fluid Sizing Sample Problem No. 1 120. . . . . . . . . . . . . . . . Compressible Fluid Sizing Sample Problem No. 2 122. . . . . . . . . . . . . . . . Representative Sizing Coefficients for Single–Ported Globe Style Valve Bodies 125. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Representative Sizing Coefficients for Rotary Shaft Valves 126. . . . . . . . . . Actuator Sizing 128. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Globe Valves 128. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Unbalance Force 128. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Typical Unbalance Areas of Control Valves 128. . . . . . . . . . . . . . . . B. Force to Provide Seat Load 129. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Packing Friction 130. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Typical Packing Friction Values 131. . . . . . . . . . . . . . . . . . . . . . . . . . D. Additional Forces 131. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Actuator Force Calculations 132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rotary Actuator Sizing 132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Torque Equations 132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Breakout Torque 132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dynamic Torque 132. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Typical Rotary Shaft Valve Torque Factors 133. . . . . . . . . . . . . . . . . . . . . . . . . V–Notch Ball Valve with Composition Seal 133. . . . . . . . . . . . . . . . . . . . . . . . . High Performance Butterfly Valve with Composition Seal 133. . . . . . . . . . . . . Maximum Rotation 133. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-Destructive Test Procedures 133. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Magnetic Particle (Surface) Examination 134. . . . . . . . . . . . . . . . . . . . . . . . Liquid Penetrant (Surface) Examination 134. . . . . . . . . . . . . . . . . . . . . . . . . Radiographic (Volumetric) Examination 134. . . . . . . . . . . . . . . . . . . . . . . . . Ultrasonic (Volumetric) Examination 135. . . . . . . . . . . . . . . . . . . . . . . . . . . . Cavitation and Flashing 135. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Choked Flow Causes Flashing and Cavitation 135. . . . . . . . . . . . . . . . . . . Valve Selection for Flashing Service 136. . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Selection for Cavitation Service 137. . . . . . . . . . . . . . . . . . . . . . . . . . Noise Prediction 138. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aerodynamic 138. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydrodynamic 139. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Noise Control 139. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Noise Summary 142. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Packing Selection 143. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Packing Selection Guidelines for Sliding–Stem Valves 144. . . . . . . . . . . . . . . Packing Selection Guidelines for Rotary Valves 145. . . . . . . . . . . . . . . . . . . . Chapter 6. Special Control Valves 147. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High Capacity Control Valves 147. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low Flow Control Valves 148. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High-Temperature Control Valves 148. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cryogenic Service Valves 149. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table of Contents ix Customized Characteristics and Noise Abatement Trims 150. . . . . . . . . . . . . Control Valves for Nuclear Service in the USA 150. . . . . . . . . . . . . . . . . . . . . . Valves Subject to Sulfide Stress Cracking 151. . . . . . . . . . . . . . . . . . . . . . . . . Chapter 7. Steam Conditioning Valves 153. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Understanding Desuperheating 153. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Technical Aspects of Desuperheating 154. . . . . . . . . . . . . . . . . . . . . . . . . . Typical Desuperheater Designs 156. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fixed Geometry Nozzle Design 156. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Variable Geometry Nozzle Design 157. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self-Contained Design 157. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steam Atomized Design 158. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geometry-Assisted Wafer Design 159. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Understanding Steam Conditioning Valves 159. . . . . . . . . . . . . . . . . . . . . . . . Steam Conditioning Valve Designs 160. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Feedforward Design 160. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manifold Design 161. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure-Reduction-Only Design 163. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Understanding Turbine Bypass Systems 164. . . . . . . . . . . . . . . . . . . . . . . . . . Turbine Bypass System Components 164. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turbine Bypass Valves 165. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turbine Bypass Water Control Valves 165. . . . . . . . . . . . . . . . . . . . . . . . . . Electro-Hydraulic System 165. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 8. Installation and Maintenance 167. . . . . . . . . . . . . . . . . . . . . . . . . . . Proper Storage and Protection 167. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Proper Installation Techniques 168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Read the Instruction Manual 168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Be Sure the Pipeline Is Clean 168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inspect the Control Valve 168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use Good Piping Practices 168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Valve Maintenance 169. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reactive Maintenance 169. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preventive Maintenance 170. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Predictive Maintenance 170. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Actuator Diaphragm 171. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stem Packing 171. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Seat Rings 172. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Grinding Metal Seats 172. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Replacing Seat Rings 172. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bench Set 173. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 9. Standards and Approvals 175. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Valve Standards 175. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . American Petroleum Institute (API) 175. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table of Contents x American Society of Mechanical Engineers (ASME) 175. . . . . . . . . . . . . . European Committee for Standardization (CEN) 176. . . . . . . . . . . . . . . . . European Industrial Valve Standards 176. . . . . . . . . . . . . . . . . . . . . . . . European Material Standards 176. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . European Flange Standards 177. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fluid Controls Institute (FCI) 177. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Instrument Society of America (ISA) 177. . . . . . . . . . . . . . . . . . . . . . . . . . . . International Electrotechnical Commission (IEC) 178. . . . . . . . . . . . . . . . . International Standards Organization (ISO) 179. . . . . . . . . . . . . . . . . . . . . . Manufacturers Standardization Society (MSS) 179. . . . . . . . . . . . . . . . . . . NACE International 179. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Product Approvals for Hazardous (Classified) Locations 179. . . . . . . . . . . . . References 179. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Canadian Standards Association (CSA) Standards 179. . . . . . . . . . . . European Committee for Electrotechnical Standardization (CENELEC) Standards 179. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Instrument Society of America (ISA) Standards 179. . . . . . . . . . . . . . . . International Electrotechnical Commission (IEC) Standards 179. . . . . National Electrical Manufacturer’s Association (NEMA) Standards 179. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . National Fire Protection Association (NFPA) Standards 179. . . . . . . . . North American Approvals 179. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Approval Agencies 179. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Protection 180. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nomenclature 180. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hazardous Location Classification 180. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temperature Code 181. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NEMA Enclosure Rating 182. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Locations 182. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hazardous (Classified) Locations 182. . . . . . . . . . . . . . . . . . . . . . . . . . . CSA Enclosure Ratings 183. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intrinsically Safe Apparatus 183. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Entity Concept 183. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CSA System Parameter Concept 184. . . . . . . . . . . . . . . . . . . . . . . . . . . Loop Schematic (Control Drawing) 184. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of Protection Techniques 184. . . . . . . . . . . . . . . . . . . . . . . . . . Explosion–proof Technique 184. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Advantages of this Technique 184. . . . . . . . . . . . . . . . . . . . . . . . . . . . Disadvantages of this Technique 185. . . . . . . . . . . . . . . . . . . . . . . . . Installation Requirements 185. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intrinsically Safe Technique 185. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Advantages of this Technique 185. . . . . . . . . . . . . . . . . . . . . . . . . . . . Disadvantages of this Technique 185. . . . . . . . . . . . . . . . . . . . . . . . . Dust Ignition–proof Technique 185. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non–Incendive Technique 185. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Advantages of this Technique 186. . . . . . . . . . . . . . . . . . . . . . . . . . . . Disadvantages of this Technique 186. . . . . . . . . . . . . . . . . . . . . . . . . [...]... the process variable and then provides an appropriate output signal to the final control element Control Loop: (See Closed Loop.) Control Range: The range of valve travel over which a control valve can maintain the installed valve gain between the normalized values of 0.5 and 2.0 Control Valve: (See Control Valve Assembly.) Control Valve Assembly: Includes all components normally mounted on the valve:... control industries is the control valve The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point Many people who talk about control valves or valves are really referring to a control valve assembly The control valve assembly typically consists... Introduction to Control Valves of additional valve accessories, which can include positioners, transducers, supply pressure regulators, manual operators, snubbers, or limit switches Other chapters of this handbook supply more detail about each of these control valve assembly components Whether it is called a valve, control valve or a control valve assembly, is not as important as recognizing that the control. .. part of the control loop It is not accurate to say that the control valve is the most important part of the loop It is useful to think of a control loop as an instrumentation chain Like any other chain, the whole chain is only as good as its weakest link It is important to ensure that the control valve is not the weakest link Following are definitions for process control, sliding-stem control valve,... point A controller then processes this information and de- cides what must be done to get the process variable back to where it should be after a load disturbance occurs When all the measuring, comparing, and calculating are done, some type of final control element must implement the strategy selected by the controller The most common final control element in the process control industries is the control. .. the output signal Dead band is the name given to a general phenomenon that can apply to any device For the valve Chapter 1 Introduction to Control Valves vice, the most common final control element in the process control industries is the control valve assembly The control valve manipulates a flowing fluid, such as gasses, steam, water, or chemical compounds, to compensate for the load disturbance and... Full: The flow-controlling member of rotary-shaft control valves using a complete sphere with a flow passage through it The flow passage equals or matches the pipe diameter 13 Chapter 1 Introduction to Control Valves W4920/IL SEGMENTED BALL VALVE W6957/IL CONVENTIONAL DISK BUTTERFLY VALVE W6213/IL W5477/IL ECCENTRIC DISK VALVE CONTOURED DISK BUTTERFLY VALVE Figure 1-14 Typical Rotary-Shaft Control Valve... BUTTERFLY VALVE Figure 1-14 Typical Rotary-Shaft Control Valve Constructions 14 Chapter 1 Introduction to Control Valves Ball, Segmented: The flow–controlling member of rotary shaft control valves using a partial sphere with a flow passage through it Ball, V-notch: The most common type of segmented ball control valve The V-notch ball includes a polished or plated partial-sphere surface that rotates against... Therefore, pressure down- Chapter 1 Introduction to Control Valves stream of the valve vena contracta recovers to a high percentage of its inlet value Straight-through flow valves, such as rotary-shaft ball valves, are typically high-recovery valves a valve having a more streamlined flowpath Although individual designs vary, conventional globe-style valves generally have low pressure recovery capability... Process Control Terminology: Quick Opening Characteristic.) Rangeability: The ratio of the largest flow coefficient (Cv) to the smallest flow coefficient (Cv) within which the deviation from the specified flow characteristic does not exceed the stated limits A control valve that still does a 17 Chapter 1 Introduction to Control Valves good job of controlling when flow increases to 100 times the minimum controllable . set point. Many people who talk about control valves or valves are really referring to a control valve assembly. The control valve assembly typically consists. information on control valve performance and the latest technologies. D Chapter 1 offers an introduction to control valves including definitions for common control