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Fundamentals of Process Third Edition by Paul W. Murrill, Ph.D.

® TABLE OF CONTENTS

Preface ...... 11

Unit 1: Introduction and Overview ...... 1 1-1. Course Coverage...... 3 1-2. Purpose...... 4 1-3. Audience and Prerequisites ...... 4 1-4. Study Material...... 4 1-5. Organization and Sequence ...... 4 1-6. Course Objectives ...... 5 1-7. Course Length...... 6 Unit 2: Basic Control Concepts...... 7 2-1. Control History ...... 9 2-2. The Variables Involved ...... 10 2-3. Typical Manual Control...... 11 2-4. Control ...... 12 2-5. Manual Feedforward Control...... 13 2-6. Automatic Feedforward Control ...... 14 2-7. Process Control and Process Management...... 15 Unit 3: Functional Structure of Feedback Control ...... 19 3-1. A Single Feedback Control Loop ...... 21 3-2. Block Diagrams ...... 22 3-3. The Functional Layout of a Feedback Loop ...... 23 3-4. Dynamic Components ...... 25 3-5. Mathematical Model of a Loop...... 26 3-6. Mathematical Notation (For Those Who Want It) ...... 27 Unit 4: Sensors and Transmission Systems ...... 31 4-1. The Sensor and the Transmitter ...... 33 4-2. Sensor Dynamics...... 34 4-3. Selection of Sensing Devices ...... 36 4-4. Accuracy and Precision ...... 36 4-5. Sensitivity, Repeatability, and Reproducibility ...... 38 4-6. Rangeability and Turndown...... 39 4-7. Measurement Uncertainty Analysis ...... 39 4-8. Transmission Systems ...... 40 4-9. Pneumatic Transmission ...... 41 4-10. Electrical Transmission Systems...... 42 4-11. Multiplexing ...... 43 4-12. Digital ...... 43 4-13. Smart Sensors ...... 44 Unit 5: Typical Measurements ...... 47 5-1. Pressure Sensors/Transmitters ...... 49 5-2. Pressure Transmitter Technologies ...... 50 5-3. Flow Sensors/Transmitters...... 52 5-4. Other Flowmeters ...... 55 5-5. Level Sensors/Transmitters ...... 57 5-6. Temperature Measurement Using Thermocouples...... 59 5-7. Other Temperature Measurements ...... 61 5-8. Analytical Measurements ...... 63

7 8 Table of Contents

Unit 6: Controllers...... 69 6-1. Controllers ...... 71 6-2. On-Off Control ...... 72 6-3. ...... 74 6-4. Reset Control ...... 77 6-5. Rate Control ...... 79 6-6. PID Control ...... 80 6-7. Summary ...... 81 Unit 7: Control Valves ...... 85 7-1. Control Valves, Actuators, and Positioners ...... 87 7-2. Linear-Stem Motion Control Valves ...... 89 7-3. Rotary Control Valves ...... 91 7-4. Ball Valves ...... 92 7-5. Characteristics ...... 94 7-6. Control Valve Selection and Sizing ...... 94 7-7. Control Valve Dynamic Performance ...... 96 7-8. Power Failure ...... 99 Unit 8: Process Dynamics ...... 101 8-1. First-Order Lags ...... 103 8-2. Time Constants ...... 106 8-3. Higher-Order Lags ...... 107 8-4. Dead Time ...... 110 8-5. Closed-Loop Response versus Open-Loop Response...... 113 8-6. Some Generalizations...... 115 Unit 9: Tuning Control Systems...... 119 9-1. What Is Good Control? ...... 121 9-2. The Tuning Concept...... 122 9-3. Closed-Loop Tuning Methods ...... 124 9-4. The Process Reaction Curve ...... 127 9-5. A Simple Open-Loop Method ...... 128 9-6. Integral Methods...... 131 9-7. The Need to Retune and Adaptive Tuning...... 132 9-8. Summary ...... 133 Unit 10: Cascade Control ...... 135 10-1. The Concept of Cascade Control ...... 137 10-2. Simple Applications ...... 138 10-3. More Complex Applications...... 143 10-4. Guiding Principles for Implementing Cascade Control ...... 147 10-5. More Examples ...... 151 10-6. Selection of Cascade Controller Modes and Tuning ...... 154 Unit 11: Feedforward and Multivariable Control...... 157 11-1. Feedforward Control ...... 159 11-2. A Feedforward Control Example...... 161 11-3. Steady-State or Dynamic Feedforward Control? ...... 163 11-4. General Feedforward Control...... 164 11-5. Combined Feedforward and Feedback Control...... 165 11-6. The Multivariable Control Problem...... 168 11-7. Implementing Multivariable Control ...... 169 Unit 12: Special-Purpose Concepts173 12-1. Computing Components ...... 175 Table of Contents 9

12-2. Ratio Control ...... 176 12-3. Applying Ratio Control ...... 178 12-4. Override Control...... 184 12-5. Selective Control ...... 186 12-6. Duplex or Split-range Control ...... 189 12-7. Auto-Selector or Cutback Control ...... 190 Unit 13: Dead Time Control ...... 195 13-1. Dead Time ...... 197 13-2. The Smith Predictor Algorithm ...... 200 13-3. A Smith Predictor Application ...... 203 13-4. The Moore Analytic Predictor ...... 205 13-5. The Dahlin Algorithm ...... 206 13-6. Summary ...... 207 Unit 14: Nonlinear Compensation and Adaptive Control ...... 209 14-1. Nonlinearities ...... 211 14-2. Valve Characteristics ...... 212 14-3. Process Characteristics...... 213 14-4. Adaptive Control ...... 216 14-5. Adaptive Gain Control ...... 218 14-6. Three-Mode On-line Tuning ...... 221 14-7. Model Reference Adaptive Control ...... 224 Unit 15: Modern Architecture ...... 227 15-1. Basic Components ...... 229 15-2. System Components...... 231 15-3. Direct Digital Control (DDC) Systems ...... 233 15-4. Supervisory Control Systems ...... 236 15-5. Control System Structure ...... 238 15-6. Distributed Control Systems (DCS) ...... 240 15-7. Single-Loop or Multi-loop Structures ...... 242 15-8. Sequential or Batch Control ...... 244 Unit 16: New Directions for Process Control...... 247 16-1. Process Control and Process Management...... 249 16-2. Specific Characteristics of Process Control ...... 250 16-3. Specific Characteristics of Process Management ...... 252 16-4. Computer-Integrated Manufacturing (CIM) ...... 253 16-5. Perspective on Statistical Process Control and Statistical Quality Control ...... 255 16-6. The Tools of Statistical Process Control ...... 256 16-7. Statistical Process Optimization ...... 260 16-8. Artificial Intelligence and Expert Systems ...... 260 16-9. Neural Networks ...... 261 Appendix A: Graphic Symbols for Process Measurement and Control . . . . . 265 Appendix B: Glossary of Standard Process Terminology . . 277 Appendix C: Solutions to All Exercises ...... 297 Other Books by Paul W. Murrill ...... 329 Index ...... 331