Aeration Control System Design

Preface xi

Acknowledgments xiii

List of Figures xv

List of Tables xxi

1 Introduction 1

1.1 Basic Concepts and Objectives 2

1.2 Safety 9

1.3 The Importance of an Integrated Approach 10

1.4 Importance of Operator Involvement 13

1.5 The Benefits of Successful Aeration Process Automation 14

Example Problems 19

2 Initial System Assessment 21

2.1 Define Current Operations 24

2.2 Evaluate Process and Equipment 37

2.3 Benchmark Performance 40

2.4 Estimate Potential Energy Savings and Performance Improvement 42

2.5 Prepare Report 45

Example Problems 47

3 Aeration Processes 49

3.1 Process Fundamentals 49

3.2 Loading Variations and Their Implications 68

3.3 Process Limitations and Their Impact on Control Systems 70

Example Problems 74

4 Mechanical and Diffused Aeration Systems 77

4.1 Oxygen Transfer Basics 78

4.2 Types of Aerators 87

4.3 Savings Determinations 106

Example Problems 111

5 Blowers and Blower Control 113

5.1 Common Application and Selection Concerns 114

5.2 Positive Displacement Blowers and Control Characteristics 134

5.3 Dynamic Blowers 143

Example Problems 157

6 Piping Systems 161

6.1 Design Considerations 162

6.2 Pressure Drop 178

6.3 Control Valve Selection 182

Example Problems 187

7 Instrumentation 191

7.1 Common Characteristics and Electrical Design Considerations 192

7.2 Pressure 202

7.3 Temperature 205

7.4 Flow 209

7.5 Analytic Instruments 216

7.6 Motor Monitoring and Electrical Measurements 224

7.7 Miscellaneous 226

Example Problems 230

8 Final Control Elements 233

8.1 Valve Operators 234

8.2 Guide Vanes 238

8.3 Motor Basics 239

8.4 Motor Control 247

8.5 Variable Frequency Drives 251

Example Problems 259

9 Control Loops and Algorithms 261

9.1 Control Fundamentals 264

9.2 Dissolved Oxygen Control 280

9.3 Aeration Basin Air Flow Control 287

9.4 Pressure Control 288

9.5 Most-Open-Valve Control 291

9.6 Blower Control and Coordination 293

9.7 Control Loop Timing Considerations 302

9.8 Miscellaneous Controls 303

Example Problems 305

10 Control Components 309

10.1 Programmable Logic Controllers 310

10.2 Distributed Control Systems 323

10.3 Human Machine Interfaces 323

10.4 Control Panel Design Considerations 328

Example Problems 330

11 Documentation 333

11.1 Specification Considerations 335

11.2 Data Lists 338

11.3 Process and Instrumentation Diagrams 341

11.4 Ladder and Loop Diagrams 342

11.5 One-Line Diagrams 344

11.6 Installation Drawings 345

11.7 Loop Descriptions 347

11.8 Operation and Maintenance Manuals 348

Example Problems 349

12 Commissioning 351

12.1 Inspection 354

12.2 Testing 357

12.3 Tuning 361

12.4 Training 365

12.5 Measurement and Verification of Results 368

Example Problems 369

13 Summary 371

13.1 Review of Integrated Design Procedure 371

13.2 Potential Problem Areas 374

13.3 Benefits 375

Example Problems 375

Appendix A: Example Problem Solutions 377

Appendix B: List of Equations and Variables 447

Bibliography 485

Index 487