Process Control Basics
Process control is essential in modern manufacturing. The control system is the eyes, ears, and nervous system of the plant. It senses, decides, and directs the activities of the pumps, valves, motors, and other equipment. The control system handles many routine tasks, freeing up the operator to oversee the operation and handle new situations that arise. Without process control, it would be nearly impossible to efficiently produce commodities like pulp and paper, gasoline, plastic, and pharmaceuticals.
Most people learn process control through hands-on plant experience, accompanied by a healthy dose of self-study. This is because textbooks generally address the mathematics of process dynamics and control, but often miss the practical aspects. This easy-to-read book fills the gap by focusing on practical real-world knowledge of process control systems, providing clear and concise examples, and providing practical advice for handling day-to-day maintenance and documentation.
The author begins by discussing control terminology, principles, and applications, the information one needs to form a basic understanding of process control. He then explains the differences between discrete, continuous, and batch control, as well as the different control systems, programming languages, and documentation needed for each. To complete the foundation, the author addresses the management of control systems including discussions about maintenance, change management, communications, and documentation. Finally, one chapter introduces advanced control topics such as advanced regulatory control, multivariable control, and neural networks.
Whether you are a student of process control, a technician or engineer expanding their skills, or someone in operations, maintenance, sales, support, or management who wants to develop a basic understanding of process control, this book is for you.
Table of Contents:
Acknowledgments xiii
Preface xvii
About the Author xix
Chapter 1 What Is Process Control? 1
1.1 What Is a Process? 1
1.2 What Is Control? 2
1.3 Why Do We Need Process Control? 4
1.4 How to Use This Book 7
Chapter 2 Basic Measurements 9
2.1 General Principles of Measurement 9
2.2 Pressure Measurement 9
2.3 How Level Sensors Sense 18
2.4 How Flow Sensors Sense 24
2.5 Temperature Sensors 31
2.6 Range, Span, and Calibration 36
Chapter 3 Control System Basics 41
3.1 Closed Loop versus Open Loop Control 41
3.2 Single Loop Controller 43
3.3 Logic Control, Sequential and Batch Control 44
3.4 PLC 46
3.5 DCS 53
3.6 Hybrid Controllers 56
3.7 Embedded Controllers 56
Chapter 4 Communications 59
4.1 Binary Communications 59
4.2 Analog Communications 61
4.3 Digital Communications 64
4.4 Converting Between Signal Types 66
4.5 Displaying Information 68
4.6 Retaining Data History 71
Chapter 5 Final Control Elements 73
5.1 Control Valves 74
5.2 Dampers 82
5.3 Actuators 83
5.4 Switches and Positioners 85
5.5 Variable Speed Drives 86
5.6 Heaters 88
5.7 Other Final Control Elements 89
5.8 Regulators 89
5.9 Limiting Elements 89
Chapter 6 Continuous Control 93
6.1 Control Terminology 93
6.2 On-Off Control of Continuous Processes 94
6.3 PID 95
6.4 Selectors, Overrides, and Interlocks 109
6.5 Alarms, Messages, and Reports 111
Chapter 7 Logic Control 115
7.1 Binary Logic Control 116
7.2 How Binary Logic Control Works 116
7.3 Binary Logic Diagramming 121
7.4 Implementation of Binary Logic Control 124
Chapter 8 Control System Documentation 129
8.1 Process Flow Diagrams 129
8.2 P&ID Drawings 130
8.3 Instrument Index 132
8.4 Instrument Specifications 133
8.5 Piping Diagrams 134
8.6 Control Narratives 134
8.7 Loop Diagrams 136
8.8 Logic Diagrams 136
8.9 Control Loop Diagrams 136
8.10 Network Diagrams 137
8.11 Factory and Site Acceptance Tests 138
Chapter 9 Practical Considerations 141
9.1 Materials 141
9.2 Power Supply 142
9.3 Instrument Location 144
9.4 Accuracy 144
9.5 Protecting the Instrument 146
9.6 Maintenance and Reliability Considerations 147
9.7 Management of Change 148
9.8 Cybersecurity 149
Chapter 10 Advanced Sensors and Analyzers 151
10.1 Sensors for Process Fluids 151
10.2 Physical and Mechanical Sensors 156
10.3 Analyzers 158
10.4 Combining Measurements: Virtual Sensors 160
Chapter 11 Beyond the Basics of Process Control 163
11.1 Advanced Regulatory Control 163
11.2 Model Predictive Control 169
11.3 Artificial Intelligence in Process Control 171
11.4 Safety Instrumented Systems 173
11.5 Diagnostics and Analytics 173
11.6 Alarm Management 174
References 175
Abbreviations/Acronyms 177
Bibliography 181
Index 187
About the Author :
George Buckbee, PE, is a veteran of the process control industry. An experienced author and instructor, he has over 30 years of practical experience improving process performance in a wide array of process industries including oil and gas, pulp and paper, pharmaceuticals, and consumer products.
Buckbee's career includes direct industry experience at Procter & Gamble and Sanofi Pasteur, before entering the software development and control system consulting business at ExperTune. Currently head of performance solutions at Neles, he manages global digital solutions for valve monitoring, and the ExperTune family of products and services.He is the coauthor (along with Joseph Alford) of Automation Applications in Bio-Pharmaceuticals, published by ISA. He wrote several chapters in The Instrument Engineer's Handbook and authored Mastering Cascade Control and Mastering Split-Range Control. He has also written dozens of articles and white papers on control system performance.
Buckbee holds a BS in chemical engineering from Washington University, and an MS in chemical engineering from the University of California, Santa Barbara. He was selected as an ISA Fellow in 2011, and he is a member of the ISA Publications Department.
