About the Authors xiiiPreface xvAcknowledgments xvii1 Introduction to Loop Checking 11.1 The Opportunity 11.2 Loop Checking: Introduction 31.2.1 Defining the Loop 31.2.2 Elements of the Loop 41.2.3 Sensor/Transmitter 41.2.4 Controller 51.2.5 Final Control Element 51.2.6 Other Loop Types 61.2.7 Loop Checking 71.2.7.1 Process Overview 71.2.7.2 Technology Improvements 81.3 Process Control Example 81.3.1 Measurement 81.3.2 Control System 81.3.3 Final Control Element 91.4 Other Loop Checking Considerations 101.4.1 Keeping Score 101.4.1.1 Loop Variability 101.4.1.2 Standard Deviation 101.4.1.3 Heading Variability 121.4.2 Loop Nonlinearities and Dead Time: The Bad Guys 131.5 Control Loop Design Guidelines 17References 17Review Questions 182 The Factory Acceptance Test 192.1 Documentation 192.2 Test Planning 202.3 Performing the FAT 202.3.1 Hardware and I/O Check 202.3.1.1 Section 1: Introduction 212.3.1.2 Section 2: Test Method Instructions 212.3.1.3 Section 3: Bill of Materials (BOM) 212.3.1.4 Section 4: System Components 212.3.1.5 Section 5: Grounding and Wire Shielding 222.3.1.6 Section 6: Alternating and Direct Current (AC/DC) Power 222.3.1.7 Section 7: I/O Check (Optional) 222.3.2 Loop Checking 222.3.2.1 Section 1: Introduction 242.3.2.2 Section 2: Test Method Instructions 242.3.2.3 Section 3: Base-Level Analog and Discrete Elements 242.3.2.4 Section 4: Basic Regulatory Control Loop Elements 252.3.2.5 Section 5: Discrete Element Control (Motor Starts and Stops, On-Off/Open-CloseDevices) 262.3.2.6 Section 6: Display Testing 272.3.2.7 Section 7: Test Results 282.4 Process Simulation 282.5 Process Control Example 302.5.1 Documentation 302.5.2 Test Plan 302.5.3 Test Equipment 302.5.4 Test Methods 302.5.5 Checklists 31References 36Review Questions 373 Start-Up 393.1 Documentation 393.2 Loop Check Test Plan 403.3 Checking the Loop 403.3.1 Traditional Instruments (Non-Smart) 403.3.2 Smart Instruments 423.3.3 Smart Commissioning 423.4 Process Control Example 453.4.1 Documentation 453.4.2 Test Plan 453.4.2.1 Traditional Instruments (Non-Smart) 453.4.2.2 Smart Instruments 473.5 Example Forms 47References 50Review Questions 504 Performance Benchmarking 514.1 Designing the Test 514.1.1 Documentation 514.1.2 Interview Key Personnel 524.1.3 Loop Check Planning 524.2 Performing the Test 534.2.1 TheWalk-Through 534.2.2 Setting Up for the Loop Check 554.2.3 Connecting to the Process Signals 564.2.4 Running the As-Found Loop Time-Series Test 584.2.5 Running the Open-Loop Check or Bump Test 604.3 Analyzing and Reporting the Test Results 614.3.1 As-Found Data Collection Analysis 614.3.2 Bump Test Analysis 624.3.3 Loop Tuning 644.3.4 Reporting the Test Results 664.3.5 Fix, Tune, and Re-Run the Loop Check 674.3.6 Next Step 674.4 Process Control Example 674.4.1 Designing the Test 674.4.1.1 Documentation 674.4.1.2 Interviews 684.4.1.3 Monitoring Variables 694.4.2 Performing the Test 694.4.2.1 TheWalk-Through 694.4.2.2 Setting Up for the Test 704.4.2.3 Running the As-Found Time-Series Test 704.4.2.4 Running the As-Found Bump Test 704.4.3 Analyzing and Reporting the Test Results 704.4.3.1 As-Found Data Collection Analysis 704.4.3.2 Bump Test Analysis 704.4.3.3 Reporting the Test Results 74References 74Review Questions 755 Sustaining Performance 775.1 Maintenance Strategies 775.2 Operator Efficiency 785.3 Where to Start? 785.4 Selecting the Loop Performance Program Scope 785.5 Loop Performance Monitoring and Analyzing 795.5.1 Transmitters 795.5.1.1 Traditional Transmitters 795.5.1.2 Smart Transmitters 805.5.2 Controller PID Algorithm 825.5.2.1 Incorrect Mode 835.5.2.2 Limited Control 835.5.2.3 Uncertain Input 835.5.2.4 Large Variability 845.5.2.5 Economic Assessment 845.5.3 Final Control Device 845.5.4 Traditional Valves 855.5.5 Smart Valves 865.6 Performance Reporting 875.7 Loop Performance Program Architecture 885.7.1 Traditional Control System 895.7.2 Smart Field Devices and Loop Performance Software 895.7.3 Online Device Monitoring 905.7.4 Integrated Performance and Control System 905.8 Loop Performance Program Summary 92References 92Further Information 92Review Questions 936 Loop Checking Existing Installations 956.1 Why Loop Checks Are Essential for Calibrations 956.1.1 Example 966.2 Simulating Signals and Processes 986.3 Common Problems with Existing Installations 99References 99Appendix A Tuning 101A.1 Author’s Note 101A.2 Loop Classification by Control Function 101A.2.1 Controlled Variable 101A.2.2 Manipulated Variable 102A.2.3 Indicated Variable 102A.2.4 Set Point 104A.3 Control Algorithms 104A.3.1 Basic Algorithms 104A.3.2 The PID Algorithm 104A.3.2.1 Proportional 105A.3.2.2 Integral 106A.3.2.3 Derivative 109A.3.2.4 Complete PID Response 110A.4 Loop Tuning 111A.4.1 Tuning Criteria or “How DoWe Know When It’s Tuned?” 111A.4.1.1 Informal Methods 111A.4.1.2 Mathematical Criteria: Minimization of Index 112A.4.1.3 What’s Really Important 112A.5 Tuning Methods 112A.5.1 Experience-Based Tuning 113A.5.2 The Ziegler–Nichols Tuning Method: Open-Loop (Reaction Rate) 113A.5.3 The Ziegler–Nichols Tuning Method: Closed-Loop (Ultimate Period) 114A.5.4 Controllability of Processes 115A.5.5 Flow Loops 115Reference 115Appendix B Answers to Review Questions 117Chapter 1 117Chapter 2 118Chapter 3 119Chapter 4 119Chapter 5 120Abbreviations 121Bibliography 123Index 125
