Thermography - Understanding our thermal world

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Thermography - Understanding our thermal world

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Agenda

• Thermography
• What, Why and Where
• Applications
• How a Thermal Imager works
• How Does an Imager Measure Temperature
• Thermography Physics and Heat Transfer
• Resolving detail and capturing a good image
• Additional training support
• Imager hands-on
• Questions?

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What is Thermography?

• It is the science of seeing temperatures by
  measuring the radiation emitted from a given
  surface and converting this data to a
  corresponding digital, or visual image
• Infrared radiation is emitted by all objects
  based on their temperature
• The amount of radiation increases with
  temperature
• We are only measuring the surface temperature

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Why use Thermal Imaging?

• Hot or cold areas, or thermal anomalies, often
  are a strong indicator of equipment health.
• Allows maintenance personnel to become more
  proactive and less reactive.
• Thermal Imaging works well to inspect
• Electrical Equipment
• Mechanical Equipment
• Heating/Cooling Equipment
• Building Envelope
• Electronic circuits and boards
• Medical/Health screening
• Other!

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Temperature Measurements

• Fast, safe and accurate non-contact measurements
  can be obtained from objects even if the are
• moving or very hot
• difficult to reach
• expensive to shut-down
• dangerous to contact
• contaminated or altered if contacted

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Downtime is expensive

• Industry Sector Revenue/Hour
• Chemicals 704,101
• Construction and Engineering 389,601
• Electronics 477,366
• Energy 2,817,846
• Food/beverage processing 804,192
• Manufacturing 1,610,654
• Metals/natural resources 580,588
• Pharmaceuticals 1,082,252
• Utilities 643,250

Source Jacksonville Power Authority
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Power Transmission Distribution applications
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Substation transformers
Note temperature difference
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Substation transformers
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Transformer Cooling
Some cooling tubes appear to be plugged
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Oil cooled transformer
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Pad-mount transformers
Look for consistent temperatures across all
elbows
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Transformers elbows
Look for problems in both internal and external
connections
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Hot bushing
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Pole transformer
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Pole transformer connection
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Utility Connection
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Utility connection
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Electrical panels and circuits

• Overloaded systems or excessive current
• Loose or corroded connections
• Component failures
• Wiring mistakes
• Under-specified components
• Power quality problems like phase unbalance,
  overload or harmonic distortion
• Insulation failures

Image shown here is Picture-In-Picture (PIP) mode
where center ¼ of image is IR surrounded by ¾
visible
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Thermography helped distinguish between loose
connection and overloaded circuit

• Courtesy of Snell Infrared

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IR inspection windows

• IR windows provide faster, safer equipment
  inspections
• High-voltage Switchgear
• Medium-voltage Switchgear
• Dry-Type Transformers
• Motor Control Centers
• Other areas where Arc Flash Hazard exists

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Breaker Panel

Two lighting breakers are 35F above ambient
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In the beginning

• In 1800, Sir William Herschel discovered that by
  passing sunlight through a glass prism and
  measuring the temperature of the colors, the
  temperature increased from the violet to the red
  part of the spectrum.
• He decided to measure the areas just beyond the
  red portion and this was the highest temperature
  of all!
• He found these calorific rays, which existed
  beyond visible light, were reflected, refracted,
  absorbed and transmitted just like visible light
• These rays were re-named infrared radiation
  prefix means below

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Infrared Radiation

• Infrared radiation is electromagnetic radiation
  with wavelengths longer than visible light but
  shorter than microwaves
• Infrared radiation is radiated heat that cannot
  be seen by our eyes but can be sensed by our skin
• All objects, whatever their temperature, emit
  infrared radiation
• The intensity of infrared radiation depends on
  the temperature and a surface property termed
  emissivity
• When an object reaches approximately
  644?C(1200?F) visible light is emitted

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Infrared spectrum
Visible light
Ultra- violet
Gamma- rays

Infrared
µwave
Radio
X-rays
Long-wave 8-14µ
Mid-wave 2-6µ
IR atmospheric transmission bands
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jumping forward

• Honeywell was a major supplier of military
  infrared systems in the 80s but the detectors
  required cooling to -340F
• Received 12 million of top-secret contracts to
  developed a long-wave infrared detector array
  technology that required no cooling
• First to develop the microbolometer
• Sold large infrared products division in 1989
• Military declassified the use of microbolometer
  technology in 1992
• Licensed microbolometer technology to other
  manufacturers

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Microbolometer Technology

• VOx is deposited onto tiny platelets
• Incoming target radiation heats the VOx causing a
  change in electrical resistance which is read by
  measuring the resulting change in bias current.
• Sensors can detect temperature change as slight
  as 0.05 C

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How do we get a picture?

• Each of the thousands of elements, or pixels,
  contain an accurate temperature value. The
  Imager, through the use of a complex set of
  algorithms, assign specific colors that
  correspond exactly with the temperature value
  found at the specific X Y coordinate.

• Some cameras save a simple picture which does not
  actually contain any measurements. 
• Fully radiometric cameras store the actual
  temperature measurements which can be brought
  into a PC later for analysis.

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How does it work?

• 19,200 detectors or more are fabricated into a
  two-dimensional array called a Focal Plane Array
  (FPA)
• Each individual detector measures the incoming
  radiation and converts this data to a thermogram,
  or visual image, which we use for detailed
  temperature analysis and documentation.

Its like having Thousands of infrared
thermometers in one instrument
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Distance to Spot Ratio DS
Distance to Spot Ratio is distance from
instrument to the object compared to the size of
the the spot being measured
1 ft.
30 feet
301
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Focal Plane Array Resolution

• 160 x 120 or 320 x 240 FPAs are most common
• 160 x 120 has 19,200 elements
• 320 x 240 has 76,800 elements
• Advantages and Disadvantages
• 320x240 arrays have four times as many pixels
• All other things being equal the imager with a
  320 x 240 FPA will have four times finer detail
• Imagers made with 160 by 120 arrays are usually
  less expensive
• Many parameters determine image quality other
  than array size, or pixel count
• Electronics
• Optics/Lenses
• Thermal sensitivity (NETD)

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Selecting the Detector Array SizeDepends on the
Application

• Target size needed in a single image
• Target distance
• Spatial resolution (spot size)
• Temperature measurement accuracy
• Budget

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Temperature

• Temperature is what we commonly think of as hot
  or cold
• It is a measure of the molecular vibration in an
  object relative to the molecular vibration in
  other objects
• Molecules vibrate faster in warmer objects and
  slower in cooler objects
• Faster moving objects transfer their energy when
  they come into contact with slower moving objects
  until they reach equilibrium
• Fahrenheit and Celsius are the most commonly used
  temperature scales
• They use the freezing and boiling points of water
  as reference points

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1st Law of Thermodynamics

• Defines the conservation of energy
• - Energy is neither created nor destroyed, just
  converted from one form to another. In a closed
  system, the energy entering the system equals
  the energy leaving the system.
• Example Hydro-electric power plant converts
  kinetic energy (water flow) into mechanical
  (turbines) and finally to electrical energy
  (generators).

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Heat Energy

• Energy exists in many forms
• Mechanical
• Electrical
• Chemical
• Nuclear
• Thermal (heat)
• It is energy that is absorbed or released as an
  object changes temperature
• Measured in Btus, 1 Btu heat energy needed to
  raise temp of one pound of water one degree F

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Heat Transfer

• Heat energy always moves from warmer to colder
  areas
• This allows us to see moisture or missing
  insulation
• Problems in electrical and mechanical
  applications are probably much hotter or worse
  than it appears on the surface!
• Heat transfer can be
• Steady state heat flow is constant with time
• Transient temperature is constantly and
  significantly changing

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Three Modes of Heat Transfer

• Radiation is the transmission of electromagnetic
  rays through space
• Each material that has a temperature above
  absolute zero (-460F) emits infrared radiation,
  
• Conduction is direct heat flow through matter
• Fun fact Notice how metal feels cold? We
  perceive this as cold as the metal takes energy
  away from your hand.
• Convection is the transport of heat within a gas
  or liquid
• Cold air drops so A/C vents are high
• Warm air rises so heating vents are usually down
  low

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Reflection, Absorption and Transmission

• What happens when IR radiation strikes a surface?

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Reflection, Absorption and Transmission

• When IR radiation strikes an object surfaceonly
  three things can happen
• Some can be reflected (?)
• Some can be absorbed as heat (?)
• Some can pass through the object (?)
• From 1st Law of Thermodynamics
• ? ? ? 1
• From Kirchhoffs Law emissivity (?)
  absorptivity (?) Therefore ? ? ? 1, for
  opaque surfaces ? 0

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Radiometric measurements Radiosity

• Radiation can be transmitted through a surface
• Our IR camera lens, for example
• Does not change the temperature of the surface!
• Radiation can be reflected off a surface
• Remember our glass window example?
• Does not change the temperature of the surface!
• Radiation can be absorbed and re-emitted
• Amount of energy absorbed re-emitted
• This is what we measure with our IR camera!
• Reflected Absorbed Transmitted 1
• Known as the RAT law
• Can also say RET1

Absorbed
Re-emitted
Transmitted
Reflected
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Radiometric measurements

• The camera sensor detects infrared radiation
• Only the emitted radiation tells us about surface
  temperature.
• Different surfaces absorb and emit radiation
  differently this is called emissivity
• Adjusting emissivity value and background temp
  improves accuracy.

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Emissivity (e )

• Pronunciation "Emissiv"ity
• Definition scientific measurement of the ability
  for absorbed heat energy to radiate (leave) an
  object as compared to a black body at the same
  temperature
• a true black body radiates 100 of its absorbed
  energy (nothing is reflected or transmitted) so
  the e 1
• A perfect reflector would have an e 0
• Materials that are not black bodies only radiate
  a fraction of the radiation as a black body at
  the same temperature and wave length so the e is
  lt1

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Selecting the Correct Emissivity Value

• Rules of thumb
• Use 0.95 for all painted target surface
  independent of color
• If unpainted or un-corroded metal use 0.2 or
  lower
• Reliable measurements when emissivity is gt 0.6
• Known or controlled background temperature
• Apply tape or paint to increase emissivity
• Values for common materials are found in the
  imager owners manual, in the PC software,
  internet sources and on some Imagers
• If the target emissivity is unknown use the
  Imager to measure it
• Use the tape method

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Emissivity of Target Surfaces
Emissivity Values (samples)
Aluminum, polished 0.05 Platinum 0.08
Brick 0.85 Rubber 0.95
Bronze, polished 0.10 Snow 0.80
Bronze, porous 0.55 Steel, galvanized 0.28
Copper, oxidized 0.65 Steel, rolled 0.24
Copper, oxidized to black 0.88 Steel, rough 0.96
Skin 0.98 Tin 0.05
Nickel 0.05 Tungsten 0.05
Paint 0.94 Water 0.98
Paint, silver finish 0.31 Zinc, sheet 0.20
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Thermal Capacitance

• The amount of energy an object needs to absorb or
  release in order to change temperature
• Water heats and cools slowly because of its high
  heat capacity
• Air heats and cools rapidly because of its low
  heat capacity
• How quickly this change takes place depends on
  thermal capacitance and thermal conductivity
  not time.
• Which has the highest thermal capacitance?
• Copper
• Steel
• Brick
• Wood
• Water

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Be aware wind can effect temperature
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Wind Effects

• Wind can significantly reduce temperature of hot
  spot
• Rule of thumb
• 10mph can reduce ?T by up to 1/2
• 15mph can reduce ?T by up to 2/3
• Roof moisture inspection is very difficult in
  wind
• 0 3 Little or no drifting of smoke
• 4 7 Wind felt on face, leaves rustle, weather
  vane moves
• 8 12 Leaves in constant motion, small flags are
  extended
• 13 18 Wind raises dust and paper, small
  branches move
• 18 Thermally - go home!
• Beaufort wind scale gives more detail on
  estimating wind speed

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Parameters for a Good Image

• Composition
• Focus
• Level and Span
• Palette
• Distance
• IFOV/IFOVmeas
• System load
• Camera settings
• Calibration

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Qualitative vs. Quantitative Inspections

• Qualitative
• You dont need to know the temperature to see
  there is a problem
• Very intuitive
• Easy to see variations from the norm
• Quantitative
• Requires radiometric (temperature reading)
• Ability to compare to established limits
• Track even slight variations
• Must measure under known loading conditions

• Courtesy of Snell Infrared

• Courtesy of Snell Infrared

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Focus is CRITICAL

• IR imager focus is less sharp than a visible
  camera
• far more elements in a visible detector array
• Infrared images are naturally less sharp
• IR wave lengths are more than an order of
  magnitude longer
• visible light cameras generally measure reflected
  radiation not emitted IR imagers must measure
  emitted radiation to determine temperature
• sharp edges can exist between a black line and a
  white line but sharp edges can not exist between
  a hot line and a cold line
• Best focus is critical for accurate temperature
  measurements
• Anything but focus can be modified/optimized
  later with PC software

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Level and Span
Auto Scaled
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FOV, IFOV, IFOVmeas
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Measurement Accuracy

• Field of View (FOV) is total target area seen by
  imager
• Instantaneous Field of View (IFOV) is the
  smallest area which can be seen by the imager
  (Spatial Resolution or spot size)
• Measurement Instantaneous Field of View
  (IFOVmeas) is the smallest area an imager can
  measure and is usually 2-3 times smaller than
  IFOV
• Determined by number of system properties, not
  just the pixel resolution

115.9
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Checking calibration

• Routinely check basic calibration before each
  scan.
• Here are a few simple test you can perform
• Check the tear duct of a work partner (recommend
  the same person)
• Check an ice bath to verify camera performance at
  0º C
• Check boiling water to verify camera performance
  at 100º C
• Acquire a blackbody reference in one of your
  common temp ranges

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Early thermal imager
80s vintage portable thermal imager
Display
Cooling gas
Detector
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Selecting an IR Camera

• What is the application?
• How will it be used?
• Considerations
• Thermal Sensitivity
• Detector Size
• Ease of Use
• IR Fusion Technology
• Ruggedness reliability
• Screen Size
• Software
• Total Cost of Ownership

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What is IR-Fusion ?

• IR-Fusion links the Thermal Image with the Visual
  Image
• Easier to understand what you are looking at
• See the context
• Read any markers/labels/text
• No laser pointer needed
• Easier to report findings to others
• No need to also take a picture with a normal
  camera
• Helps you focus the Thermal Imager better
• The Thermal Imager is focused correctly when the
  Thermal and Visual images are completely aligned

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PC Software

• Software provides image
• archiving
• enhancement
• analysis
• annotation
• report generation

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Additional training and information

• Fluke Thermal Imaging Training Center
• www.fluke.com/titraining
• Hands-On Seminars
• The Snell Group
• Online Training
• Pre-Recorded Webinars from 39 to 79
• Level 1, 2 3 Thermography Training
• Application Specific Training
• www.snellgroup.com

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Thanks for attending!
Questions?