Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

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A.2.9 Transient Heat Exchange The discussions of the three types of heat exchange in sections A.2.4, A.2.5, and A.2.6 deal with steady-state heat exchange for reasons of simplicity and easier understanding. Two fixed temperatures are assumed to exist at the two points between which the heat flows. In many applications, however, temperatures are in transition, so that the values shown for energy radiated from a target surface are the instantaneous values from the moment that measurements are made. There are numerous instances where existing transient thermal conditions are exploited in order to use thermography to reveal material or structural characteristics in test articles. Charlie Chong/ Fion Zhang
The thermogram of the outside surface of an insulated vessel carrying heated liquid, for example, should be relatively isothermal and somewhat warmer than the ambient air. Insulation voids or defects will cause warm anomalies to appear on the thermogram, allowing the thermographer to pinpoint areas of defective or damaged insulation. Here a passive approach can be taken because the transient heat flow (or it is a steady state heat flow?) from the liquid through the insulation to the outside air produces the desired characteristic thermal pattern on the product surface. Similarly, water saturated areas on flat roofs will retain solar heat well into the night; long after the dry sections have radiated their stored heat to the cold night sky, the saturated sections will continue to radiate and exhibit distinct anomalies to the thermographer. When there is no heat flow through the material or the test article to be evaluated, an active, or thermal injection, approach is used to generate a transient heat flow. Comment: In general steady state heat flow always lead to thermal equilibrium, for IRT, transient heat flows are exploited to reveal abnormalities. Charlie Chong/ Fion Zhang
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Infrared Thermal Testing Reading VI
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6.1 Basic Elements An in-house prog
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6.1.4 Responsibilities This section
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IR Viewing Window - Opaque Polymer
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6.1.8 Acceptance Criteria All surve
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6.1.9 Reporting Criteria A rigid pr
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6.1.10 Qualification of Personnel P
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EPRI Licensed Material Basic Elemen
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Page 25 and 26: 7. TRAINING AND CERTIFICATION This
Page 27 and 28: Recommended training and certificat
Page 29 and 30: ■ Level II A Level II infrared th
Page 31 and 32: The experience and education recomm
Page 33 and 34: B. Spatial Resolution • the conce
Page 35 and 36: D. Equipment Operation • Be able
Page 37 and 38: The PdM basic examination is more s
Page 39 and 40: Appendix-A The Science Of Thermogra
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Page 43 and 44: A.2.1 Heat and Temperature What is
Page 45 and 46: To convert changes in temperature o
Page 47 and 48: A.2.3 The Three Modes of Heat Trans
Page 49 and 50: The Fourier Conduction Law: Q/A Q =
Page 51 and 52: A.2.5 Convection Convective heat tr
Page 53 and 54: Figure A-2 Convective Heat Flow Cha
Page 55 and 56: A.2.6 Radiation Radiative heat tran
Page 57 and 58: A.2.7 Radiation Exchange at the Tar
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Page 61 and 62: Figure A-4 Radiative Heat Flow W ε
Page 63 and 64: A.2.8 Specular and Diffuse Surfaces
Page 65 and 66: Specular or Diffuse Surfaces Diffus
Page 67 and 68: Specular and Diffuse Surfaces Confu
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Page 75 and 76: Steady-state conduction Steady stat
Page 77 and 78: A.3 The Basic Physics of Infrared R
Page 79 and 80: A.3.1 Some Historical Background Th
Page 81 and 82: A.3.3 The Target Surface The chart
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Page 87 and 88: Two physical laws define the radian
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Page 91 and 92: Figure A-7 Spectral Distribution of
Page 93 and 94: Figure A-8 shows that the instrumen
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Page 101 and 102: Figure A-10 illustrates the spectra
Page 103 and 104: Figure A-10 Infrared Transmission o
Page 105 and 106: Figure A-11 Infrared Spectral Trans
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Page 111 and 112: Figure A-12 Characteristics of IR T
Page 113 and 114: The characteristics of the window m
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Page 117 and 118: IR Lenses - Fresnel Len Charlie Cho
Page 119 and 120: Figure A-13 Components of an Infrar
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All infrared detector-transducers e
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Figure A-14 Typical Infrared Radiat
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Germanium Len Charlie Chong/ Fion Z
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Thermopile Detector Charlie Chong/
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The IR Detectors Infrared detectors
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Figure A-15 Spectral Sensitivity of
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The Mercury- Cadmium-telluride (Hgc
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The Mercury- Cadmium-Telluride (HgC
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Point-sensing instruments for measu
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A.3.6.1 Line Scanning The purpose o
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A.3.6.2 Two-Dimensional Scanning Th
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Opto-mechanical Scanner A typical c
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Electronic scanning Electronic scan
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Figure A-18 Schematic of a Typical
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Applications for infrared FPAs incl
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Staring Charlie Chong/ Fion Zhang
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A.4.1 Point-Sensing Instruments For
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Temperature sensitivity is also cal
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EXAM score! thermal resolution (≠
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NETD - Noise Equivalent Temperature
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Figure A-19 Instrument Speed of Res
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Figure A-20 Fields of View of Infra
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Figure A-20 Fields of View of Infra
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The output requirements are totally
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Spectrally selective instruments em
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Figure A-21 Spectral Filtering for
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Figure A-22 shows a similar solutio
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A.4.2 Scanners and Imagers.Qualitat
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• Total field of view (TFOV): the
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Despite some manufacturers’ claim
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A.4.3.1 Temperature Sensitivity, Mi
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Figure A-23 Test Setup for MRTD Mea
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A.4.3.2 Spot Size (FOV) , Instantan
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■ A standard 4 bar (slit) resolut
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Both MRTD and MTF are functions of
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Charlie Chong/ Fion Zhang
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IFOVmeas: The slit width at which t
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FPA Charlie Chong/ Fion Zhang http:
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FPA Charlie Chong/ Fion Zhang
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A.4.3.3 Speed of Response and Frame
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A.4.4 Thermal Imaging Software In o
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The newest field-portable instrumen
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Appendix B Measuring Emissivity, Re
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Figure B-1 Target Radiosity Charlie
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The reference emitter technique wor
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1. Apply the reference emitter (E)
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B.2.2 Reflective Emissivity Techniq
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Figure B-3 Using the Reflective Emi
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Figure B-4 Using the Transmittance
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Appendix C Quick Reference Charts A
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MTF Determination Using An Ir Image
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Measuring And Setting Effective Emi
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Classification Of Faults (Guideline
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Reading: Four Emissivity: Understan
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Figure 1 shows a typical three-phas
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Figure IR1: Corresponding infrared
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Thermal radiation and properties of
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The thermal nature of materials. Ma
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So in plain English, when the therm
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Figure 2: Stainless steel block. (a
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Observed with our thermal imager (w
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Can you see my eye glasses in the i
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How can the thermal imager’s read
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When we remove the block from the o
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In this experiment we see that the
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Charlie Chong/ Fion Zhang http://ww
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Using a narrow band filter to measu
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Emissivity, the variable’s variab
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Emissivity and electrical equipment
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In manufacturing processes, steel o
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In this case, we have another power
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Figure IR1: Corresponding infrared
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Figure 7: Measuring the loads on a
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Summary Predictive maintenance PDM
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It is much like most endeavors in l
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Good Luck Charlie Chong/ Fion Zhang
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Charlie https://www.yumpu.com/en/br
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