Execute reliable loop checks aligned with current ISA standards
Verifying control loop functionality requires a systematic methodology and knowledge of current standards. Loop Checking: A Technician’s Guide, now in its Second Edition, delivers practical procedures for technicians responsible for control loop maintenance and performance across diverse process industries. Written by professionals with over 80 years of combined experience in industrial process controls, this guide provides standard methodology for executing loop checks.
In addition to traditional loop checking, which is covered in the ANSI/ISA-62382-2026/IEC 62382:2024 standard, this edition covers factory acceptance testing, wiring verification, performance benchmarking, and sustaining long-term performance. Each chapter includes questions with explained answers to reinforce understanding. The guide applies to new and existing analog, distributed, and digital control systems across multiple industries.
Key topics include:
- Standard methodology for loop checking aligned with ANSI/ISA-62382-2012 requirements for automation systems in process industry applications
- Factory acceptance testing procedures covering sensors, transmitters, controllers, and final control element verification and validation
- Wiring verification techniques that ensure all control loop components are correctly connected and functioning as designed
- Performance benchmarking methods for establishing baseline measurements and ongoing monitoring programs for control loop optimization
- Chapter questions with explained answers to reinforce practical understanding of loop checking concepts and procedures
Industrial technicians, instrument supervisors, maintenance engineers, and reliability professionals will find this guide directly applicable to their daily responsibilities. Whether commissioning new systems or maintaining existing installations, Loop Checking provides the standards-aligned procedures needed for effective control loop verification.
Table of Contents:
About the Authors xiii
Preface xv
Acknowledgments xvii
1 Introduction to Loop Checking 1
1.1 The Opportunity 1
1.2 Loop Checking: Introduction 3
1.2.1 Defining the Loop 3
1.2.2 Elements of the Loop 4
1.2.3 Sensor/Transmitter 4
1.2.4 Controller 5
1.2.5 Final Control Element 5
1.2.6 Other Loop Types 6
1.2.7 Loop Checking 7
1.2.7.1 Process Overview 7
1.2.7.2 Technology Improvements 8
1.3 Process Control Example 8
1.3.1 Measurement 8
1.3.2 Control System 8
1.3.3 Final Control Element 9
1.4 Other Loop Checking Considerations 10
1.4.1 Keeping Score 10
1.4.1.1 Loop Variability 10
1.4.1.2 Standard Deviation 10
1.4.1.3 Heading Variability 12
1.4.2 Loop Nonlinearities and Dead Time: The Bad Guys 13
1.5 Control Loop Design Guidelines 17
References 17
Review Questions 18
2 The Factory Acceptance Test 19
2.1 Documentation 19
2.2 Test Planning 20
2.3 Performing the FAT 20
2.3.1 Hardware and I/O Check 20
2.3.1.1 Section 1: Introduction 21
2.3.1.2 Section 2: Test Method Instructions 21
2.3.1.3 Section 3: Bill of Materials (BOM) 21
2.3.1.4 Section 4: System Components 21
2.3.1.5 Section 5: Grounding and Wire Shielding 22
2.3.1.6 Section 6: Alternating and Direct Current (AC/DC) Power 22
2.3.1.7 Section 7: I/O Check (Optional) 22
2.3.2 Loop Checking 22
2.3.2.1 Section 1: Introduction 24
2.3.2.2 Section 2: Test Method Instructions 24
2.3.2.3 Section 3: Base-Level Analog and Discrete Elements 24
2.3.2.4 Section 4: Basic Regulatory Control Loop Elements 25
2.3.2.5 Section 5: Discrete Element Control (Motor Starts and Stops, On-Off/Open-Close
Devices) 26
2.3.2.6 Section 6: Display Testing 27
2.3.2.7 Section 7: Test Results 28
2.4 Process Simulation 28
2.5 Process Control Example 30
2.5.1 Documentation 30
2.5.2 Test Plan 30
2.5.3 Test Equipment 30
2.5.4 Test Methods 30
2.5.5 Checklists 31
References 36
Review Questions 37
3 Start-Up 39
3.1 Documentation 39
3.2 Loop Check Test Plan 40
3.3 Checking the Loop 40
3.3.1 Traditional Instruments (Non-Smart) 40
3.3.2 Smart Instruments 42
3.3.3 Smart Commissioning 42
3.4 Process Control Example 45
3.4.1 Documentation 45
3.4.2 Test Plan 45
3.4.2.1 Traditional Instruments (Non-Smart) 45
3.4.2.2 Smart Instruments 47
3.5 Example Forms 47
References 50
Review Questions 50
4 Performance Benchmarking 51
4.1 Designing the Test 51
4.1.1 Documentation 51
4.1.2 Interview Key Personnel 52
4.1.3 Loop Check Planning 52
4.2 Performing the Test 53
4.2.1 TheWalk-Through 53
4.2.2 Setting Up for the Loop Check 55
4.2.3 Connecting to the Process Signals 56
4.2.4 Running the As-Found Loop Time-Series Test 58
4.2.5 Running the Open-Loop Check or Bump Test 60
4.3 Analyzing and Reporting the Test Results 61
4.3.1 As-Found Data Collection Analysis 61
4.3.2 Bump Test Analysis 62
4.3.3 Loop Tuning 64
4.3.4 Reporting the Test Results 66
4.3.5 Fix, Tune, and Re-Run the Loop Check 67
4.3.6 Next Step 67
4.4 Process Control Example 67
4.4.1 Designing the Test 67
4.4.1.1 Documentation 67
4.4.1.2 Interviews 68
4.4.1.3 Monitoring Variables 69
4.4.2 Performing the Test 69
4.4.2.1 TheWalk-Through 69
4.4.2.2 Setting Up for the Test 70
4.4.2.3 Running the As-Found Time-Series Test 70
4.4.2.4 Running the As-Found Bump Test 70
4.4.3 Analyzing and Reporting the Test Results 70
4.4.3.1 As-Found Data Collection Analysis 70
4.4.3.2 Bump Test Analysis 70
4.4.3.3 Reporting the Test Results 74
References 74
Review Questions 75
5 Sustaining Performance 77
5.1 Maintenance Strategies 77
5.2 Operator Efficiency 78
5.3 Where to Start? 78
5.4 Selecting the Loop Performance Program Scope 78
5.5 Loop Performance Monitoring and Analyzing 79
5.5.1 Transmitters 79
5.5.1.1 Traditional Transmitters 79
5.5.1.2 Smart Transmitters 80
5.5.2 Controller PID Algorithm 82
5.5.2.1 Incorrect Mode 83
5.5.2.2 Limited Control 83
5.5.2.3 Uncertain Input 83
5.5.2.4 Large Variability 84
5.5.2.5 Economic Assessment 84
5.5.3 Final Control Device 84
5.5.4 Traditional Valves 85
5.5.5 Smart Valves 86
5.6 Performance Reporting 87
5.7 Loop Performance Program Architecture 88
5.7.1 Traditional Control System 89
5.7.2 Smart Field Devices and Loop Performance Software 89
5.7.3 Online Device Monitoring 90
5.7.4 Integrated Performance and Control System 90
5.8 Loop Performance Program Summary 92
References 92
Further Information 92
Review Questions 93
6 Loop Checking Existing Installations 95
6.1 Why Loop Checks Are Essential for Calibrations 95
6.1.1 Example 96
6.2 Simulating Signals and Processes 98
6.3 Common Problems with Existing Installations 99
References 99
Appendix A Tuning 101
A.1 Author’s Note 101
A.2 Loop Classification by Control Function 101
A.2.1 Controlled Variable 101
A.2.2 Manipulated Variable 102
A.2.3 Indicated Variable 102
A.2.4 Set Point 104
A.3 Control Algorithms 104
A.3.1 Basic Algorithms 104
A.3.2 The PID Algorithm 104
A.3.2.1 Proportional 105
A.3.2.2 Integral 106
A.3.2.3 Derivative 109
A.3.2.4 Complete PID Response 110
A.4 Loop Tuning 111
A.4.1 Tuning Criteria or “How DoWe Know When It’s Tuned?” 111
A.4.1.1 Informal Methods 111
A.4.1.2 Mathematical Criteria: Minimization of Index 112
A.4.1.3 What’s Really Important 112
A.5 Tuning Methods 112
A.5.1 Experience-Based Tuning 113
A.5.2 The Ziegler–Nichols Tuning Method: Open-Loop (Reaction Rate) 113
A.5.3 The Ziegler–Nichols Tuning Method: Closed-Loop (Ultimate Period) 114
A.5.4 Controllability of Processes 115
A.5.5 Flow Loops 115
Reference 115
Appendix B Answers to Review Questions 117
Chapter 1 117
Chapter 2 118
Chapter 3 119
Chapter 4 119
Chapter 5 120
Abbreviations 121
Bibliography 123
Index 125
About the Author :
Harley M. Jeffery is a process control consultant and project manager with over 50 years of experience in industrial process controls. His career spans the design, implementation, testing, start-up, and ongoing improvement of analog, distributed, and digital control systems. He holds a BSIE from Louisiana State University and completed Monsanto’s Electrical and Instrument Engineering school in 1978.
Paul M. Franklin is currently a certified ISA instructor specializing in automation and instrumentation training for process industry professionals. His 33 years of experience in process automation includes pneumatic, electric, hydraulic, and electronic instrumentation and controls as well as PLC and DCS start-up, testing and programming.
