Spie Press BookPractical Applications of Infrared Thermal Sensing and Imaging Equipment, Third Edition
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The second edition of this text was published in 1999, and since that time many improvements have taken place in instrumentation performance and versatility. This third edition reviews these many changes and how they impact the way thermographers operate, deploy, calibrate, and test the new instruments. In addition, the instruments that have been made essentially obsolete are reviewed as part of the historical evolution of the technology.
The purposes of this text are to:
- 1.1 Overview of This Text 3
- 1.2 Reasons for Using IR Instruments 3
- 1.3 Advantages of Noncontact Thermal Measurement 4
- 1.4 Some Historical Background 5
- 1.5 Evolution of IR Cameras 6
- 2.1 Heat Transfer and Radiation Exchange Basics 9
- 2.1.1 Heat and temperature 9
- 2.1.2 Converting temperature units 9
- 2.1.3 Three modes of heat transfer 10
- 2.1.4 Conduction 10
- 2.1.5 Convection 11
- 2.1.6 Radiation 12
- 2.1.7 Radiation exchange at the target surface 13
- 2.1.8 Specular and diffuse surfaces 14
- 2.1.9 Transient heat exchange 14
- 2.2 Infrared Measurement Problem 15
- 2.2.1 Noncontact thermal measurements 16
- 2.2.2 Target surface 16
- 2.2.3 Transmitting medium 20
- 2.2.4 Measuring instrument 22
- 2.3 Thermal Scanning and Imaging Instruments 25
- 2.3.1 Line scanning 25
- 2.3.2 Two-dimensional opto-mechanical scanning 26
- 2.3.3 Infrared focal plane array (IRFPA) cameras 27
- 2.3.4 IRFPA detectors 28
- 2.3.5 Pyroelectric vidicon thermal imagers 29
- 3.1 Radiation Thermometers (Point-Sensing Instruments) 33
- 3.2 Infrared Cameras - Qualitative and Quantitative 37
- 3.2.1 Performance parameters of quantitative cameras 39
- 126.96.36.199 Total field of view (TFOV) and instantaneous field of view (IFOV) 40
- 188.8.131.52 Temperature sensitivity: MRTD or MRT 40
- 184.108.40.206 Imaging spatial resolution and instantaneous FOV 41
- 220.127.116.11 Measurement spatial resolution (IFOVmeas or MFOV) for opto-mechanically scanned imagers 43
- 18.104.22.168 Measurement spatial resolution (IFOVmeas or MFOV) for FPA imagers 45
- 22.214.171.124 Speed of response and frame repetition rate 45
- 3.2.2 Performance parameters of qualitative cameras 46
- 3.3 Thermal Imaging Software 46
- 3.4 Thermal Image Fusion Techniques 48
- 4.1 Introduction and Classification of Instruments 49
- 4.2 Instrument Manufacturers 50
- 4.3 Discussion of Instruments 50
- 4.3.1 Point sensors (radiation thermometers) 50
- 126.96.36.199 Infrared thermocouples and probes 50
- 188.8.131.52 Portable hand-held instruments 51
- 184.108.40.206 On-line monitoring and control 52
- 220.127.116.11 Special instruments 52
- 4.3.2 Line scanners 53
- 4.3.3 Infrared cameras (thermal imagers) 54
- 18.104.22.168 Cameras, nonmeasuring (thermal viewers) 54
- 22.214.171.124 Cameras, measuring (thermographic imagers) 55
- 126.96.36.199 Performance comparisons of FPA measuring cameras 56
- 4.4 Thermal Imaging Diagnostic Software 57
- 4.4.1 Quantitative thermal measurements of targets 58
- 4.4.2 Detailed processing and image diagnostics 59
- 4.4.3 Image recording, storage, and recovery 59
- 4.4.4 Image comparison 60
- 4.4.5 Thermal image fusion 60
- 4.4.6 Report and database preparation 61
- 5.1 Introduction: The Thermal Behavior of the Target 63
- 5.1.1 Emissivity difference 64
- 5.1.2 Reflectance difference 64
- 5.1.3 Transmittance difference 64
- 5.1.4 Geometric difference 64
- 5.1.5 Mass transport difference 65
- 5.1.6 Phase-change difference 65
- 5.1.7 Thermal capacitance difference 65
- 5.1.8 Induced heating difference 65
- 5.1.9 Energy conversion difference 65
- 5.1.10 Direct heat transfer difference 65
- 5.1.11 Learning about the target environment 66
- 5.2 Preparation of Equipment for Operation 66
- 5.2.1 Calibration and radiation reference sources 66
- 188.8.131.52 Checking calibration 67
- 184.108.40.206 Transfer calibration 67
- 5.2.2 Equipment checklist 68
- 5.2.3 Equipment checkout and calibration 68
- 5.2.4 Batteries 68
- 5.3 Avoiding Common Mistakes in Instrument Operation 68
- 5.3.1 Start-up procedure 69
- 5.3.2 Memorizing the default values 69
- 5.3.3 Setting the correct emissivity 69
- 5.3.4 Filling the IFOVmeas for accurate temperature measurements 70
- 5.3.5 Aiming normal to the target surface 71
- 5.3.6 Recognizing and avoiding reflections from external sources 71
- 5.3.7 Avoiding radiant heat damage to the instrument 72
- 5.3.8 Using IR transmitting windows 72
- 5.4 The Importance of Operator Training 72
- 5.4.1 Training programs and certification 72
- 7.1 Introduction 79
- 7.2 Electrical Findings 80
- 7.2.1 High electrical resistance 80
- 7.2.2 Short circuits 80
- 7.2.3 Open circuits 82
- 7.2.4 Inductive currents 83
- 7.2.5 Energized grounds 83
- 7.2.6 Condition guidelines 84
- 7.3 Mechanical Findings 85
- 7.3.1 Friction 85
- 7.3.2 Valve or pipe blockage/leakage 86
- 7.3.3 Insulation within the plant or facility 87
- 7.4 Miscellaneous Applications 87
- 7.4.1 Rebar location 88
- 7.4.2 Condenser air in-leakage 88
- 7.4.3 Containment spray ring headers 88
- 7.4.4 Hydrogen igniters 88
- 7.4.5 Effluent thermal plumes 89
- 7.4.6 Gas leak detection 89
- 7.4.7 Seal failures 89
- 8.1 Introduction 91
- 8.2 Measuring Insulating Properties 92
- 8.3 Considering the Total Structure 92
- 8.4 Industrial Roof Moisture Detection 93
- 8.5 Subsurface Leaks and Anomalies 94
- 8.6 Thermal Image Fusion Benefit 96
- 8.7 Thermographic Inspection of Our Aging Infrastructure 96
- 9.1 Materials Testing - IR Nondestructive Testing 97
- 9.2 Failure Modes and Establishment of Acceptance Criteria 99
- 9.3 Selecting the Right IR Imaging System 99
- 9.4 Pulsed Heat Injection Applications 101
- 9.4.1 New signal-based technique simplifies image interpretation 103
- 9.4.2 Case study: Boiler tube corrosion thinning assessment 103
- 9.5 Infrastructure NDT 106
- 10.1 Evolution of Noncontact Process Control 107
- 10.2 Full Image Process Monitoring 109
- 10.3 Product Monitoring of Semiconductors 110
- 10.4 Steel Wire Drawing Machine Monitoring 110
- 10.5 Glass Products Monitoring (Spectral Considerations) 112
- 10.6 Full Image Process Control 112
- 10.7 Closing the Loop - Examples 114
- 11.1 Introduction 117
- 11.2 Comparing Thermal Imagers with Image Intensifiers 118
- 11.3 Homeland Security and other Nonmilitary Applications 118
- 11.3.1 Aerial-, ground-, and sea-based search and rescue 118
- 11.3.2 Firefighting and first response 118
- 11.3.3 Space and airborne reconnaissance 119
- 11.3.4 Police surveillance and crime detection and security 119
- 11.3.5 Driver's aid night vision 120
- 11.3.6 New thermal image fusion applications 121
- 11.3.7 New military applications 121
- 12.1 Introduction 123
- 12.2 Thermography as a Diagnostic Aid in the Early Detection of Breast Cancer 123
- 12.3 Veterinary Medicine 124
- 12.4 Biological and Threat Assessment Applications 124
The mapping of infrared (IR) energy radiated from the surface of natural and manufactured objects makes it possible to detect and recognize objects in the dark and under adverse weather and atmospheric conditions. Quantification of this energy allows users (thermographers) to determine the temperature and thermal behavior of objects.
Infrared thermal sensing and imaging instruments make it possible to measure and map surface temperature and thermal distribution passively and nonintrusively. In addition to the passive measurement of temperature distribution, thermographers have learned to use active or "thermal injection" techniques to study and evaluate the structural integrity of materials and fabricated bonds.
The purposes of this text are:
- To familiarize potential users of commercial IR sensing and imaging instruments with IR measurement and analysis basics;
- To provide the practical information needed for users to select the instrument most appropriate for their application;
- To describe how to perform valid and successful measurements in a variety of applications;
- To serve as a reference to help thermographers examine the validity of new applications.
This text is presented in two parts.
Part I begins with a review of temperature, heat, and heat transfer, with emphasis on radiative heat transfer and its relationship to IR radiation and measurement basics. Physical laws (equations) are presented in terms of their practical importance to the measurement mission.
This is followed by a review and discussion of the characteristics and performance parameters of IR sensing and imaging instruments, including a review of thermal imaging diagnostic software. Adiscussion of equipment operation follows, including guidelines for making successful measurements.
Part I concludes with a section on training and training programs, highlighting the importance of formal operator training and certification.
The second edition of this text was published in 1999, and since that time many improvements have taken place in instrumentation performance and versatility. For example, the almost total replacement of opto-mechanically scanned imagers with focal plane array (FPA)-based "staring" imagers has reduced the size, increased the ruggedness, and improved the spatial resolution of IR cameras, all of which have changed thermographers' expectations of camera performance.
Thus, this third edition reviews these many changes and how they impact the way thermographers operate, deploy, calibrate, and test the new instruments. In addition, the instruments that have been made essentially obsolete are reviewed as part of the historical evolution of the technology.
Part II introduces typical applications for thermal sensing and imaging instruments. Several chapters present various applications areas and discuss typical solutions to measurement problems.
The applications are grouped into logical categories following the guidelines established by SPIE's evolving Thermosense series of meetings, held annually since 1978.
In an attempt to classify these applications into logical categories by industry and discipline, the Thermosense symposia usually devote at least one session to each of the following categories:
1. Plant Condition Monitoring and Predictive Maintenance
2. Buildings and Infrastructure
3. Materials Evaluation - Infrared Nondestructive Testing
4. Process Monitoring and Control
5. Night Vision, Security, and Surveillance
6. Life Sciences Thermography
7. Research and Development (R&D)
The first six classifications are self-explanatory; the seventh is a catch-all to include the introduction of new instrumentation or experimental techniques. Papers on subjects classified as "R&D" one year will often be included in one of the other classifications in subsequent years as the instrumentation or techniques mature.
Although these classifications have evolved somewhat over the years, they represent reasonable subdivisions. Therefore, the chapters in Part II are organized in general accordance with these classifications.
To assist the user in instrument selection, Appendix A contains a tabulation of currently available instruments by category and manufacturer, including a digest of performance characteristics and features. Appendix B is a current index of manufacturers' websites, addresses, and phone numbers.
The text also includes quick reference charts and tables to aid the user in on-site measurements (Appendix C) and a glossary of IR/thermography terms (Appendix D).
I would like to acknowledge the contributions of the following organizations for providing data and background for this text:
American Risk Consultants Corp.
General Motors Powertrain
Goodyear Corp. Barnes Engineering Div.
Electric Power Research Institute
FLIR Systems, Inc.
Infrared Thermal Imaging, Inc.
ISI Group, division of Mine Safety Appliances
Linear Laboratories, Safetytek Corp.
Magnavox Electro-optical Systems
Mine Safety Appliances Corp.
Quantum Focus Instruments
Raytek, Inc., a Fluke company
SI Termografia Infrarroja
Thermal Wave Imaging, Inc.
I would like to express my thanks to Rob Spring, P.E., of Snell Infrared, for his dedication to training in our technology, and for applying his instructor's eye to the expert review of this third edition.
I would also like to express my thanks to Paul Zayicek of Electric Power Research Institute's NDE Center for his professionalism, his vigorous promotion of IR thermography, his many contributions to the body of knowledge in thermography, and for reviewing the second edition of this text (1999).
Finally, I would like to express my appreciation to Ron Lucier of FLIR Systems Inc. for his careful and conscientious review of the first edition of this text (1993), and for his many contributions to the first and subsequent editions.
Boynton Beach, Florida