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NESICA – Project

HUSKROUA/1702/6.1/0014

THERMAL CAMERA TRAINING – 2021 Jenuary 22

1. How to choose an IR camera (criterions)

2. IR camera Resolution adapted to the application

3. How to operate an IR camera for an accurate infrared image

4. How to best present thermal inspection results

5. Question and answer session

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1. How to choose an IR camera (criterions)

Infrared thermography, how work an thermal camera Thermography it is a new science discipline that deals with the analysis of the distribution of the temperature field on the object

surface in a contactless manner. The role of the thermography is the analysis of the infrared energy emitted from an object. Our

eyes are detectors that are designed to detect electromagnetic radiation in the visible light spectrum. All other forms of

electromagnetic radiation, such as infrared, are invisible to the human eye so we need an instrument to see it. The

thermographic measurement system can display the temperature field of the measured object, but only on its surface.The

existence of infrared was discovered in 1800 by astronomer Sir Frederick William Herschel. Both visible light and infrared is

part of the electromagnetic spectrum. Infrared has a longer wavelength (8-15 μm) and lower frequency than visible light (0,4-

0,7 μm). Infrared thermography is the science of detecting infrared energy emitted from an object, converting it to an apparent

temperature, and displaying the result as an infrared/blending infrared-visible image that is captured by a thermal camera.

Fig. 1 Spectrum of electromagnetic wave used în thermography inspections

visible light

direct - long wave infrared

PIP – visible and infrared image

reflected - long wave infrared

shaining surface

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The primary source of infrared radiation is heat or thermal radiation. Any object that has a temperature Tobject above absolute

zero (-273.15 degrees Celsius or 0 Kelvin) emits radiation in the infrared region, known as a heat signature. Even objects that

we think of as being very cold, such as ice cubes, emit infrared radiation. We experience infrared radiation every day. The heat

that we feel from sunlight, a fire or a radiator is all infrared long wave. The warmer the object, the more infrared radiation it

emits.

ambobjectrradiation TTSP

Where Pradiation is the thermal flux emitted by radiation by irradiative surface S; αr - radiation coefficient; Tamb – room

temperature.

An infrared camera (also known as a thermal imager) detects and measures the infrared energy emitted of the objects

surfaces. The camera converts that infrared data into an electronic image that shows the apparent surface temperature of the

object being measured. An infrared camera contains an optical system that focuses infrared energy onto a special detector chip

(sensor array) that contains thousands of IR detector pixels arranged in a grid. Each pixel in the sensor array reacts to the

infrared energy focused on it and produces an electronic signal. The camera processor takes the signal from each pixel and

applies a mathematical calculation to it to create a colour map of the apparent temperature of the object. For each temperature

value is assigned a different colour (palette colour). The resulting matrix of colours is sent to memory and to the camera’s

display as a temperature picture (thermal image) of that object. When you locate an anomaly, you can quickly drill down and

see the apparent temperatures of the exact points in question and determine whether they’re within the normal range.

IR-Fusion® technology combines a visible light image with an infrared thermal image with pixel-for-pixel alignment. You can

vary the intensity of the visible light image and the infrared image to more clearly see the problem in the infrared image or

locate it within the visible light image. Thermal imaging technology has become one of the most valuable diagnostic tools for

industrial applications. By detecting anomalies that are usually invisible to the naked eye, thermal imaging allows corrective

action to be taken before costly system failures occur.

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Beyond basic thermal imaging capabilities, you can find infrared cameras with a wide range of additional features that

automate functions, allow voice annotations, enhance resolution, record and stream video of the images, and support analysis

and reporting.

Fig. 2 How work an infrared camera

With an infrared thermometer you are able to measure the temperature at one single spot. Thermal imaging cameras can

measure temperatures on the entire image. An infrared camera with an low image resolution of 60 x 60 pixels it is equal to

using 3.600 IR thermometers at the same time. If we look at a top model, which has an image resolution of 640 x 480 pixels,

this means 307.200 pixels or using 307.200 infrared thermometers at the same time.

visible light

Infrared energy

Display visible and infrared

image in an colour palette

Matrix with infrared

sensors

Emmiting object

μP+

convertor

and

memory

Electronic

signal Digital

signal

Germanium

lens

Energy to Temperature colour palette

Infrared camera

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1.1. Seven criterions to choose an IR camera and accessories

1. IR image quality depending on the application:

- Required resolution for teaching applications, large area 160x120 pixels;

- Required resolution for Buildings, Industrial Energy Efficiency Applications, large area, max. 320x240 pixels;

- Required resolution for Scientific Research, small area investigations 640x480 pixels (optical)+4x digital

2. Image Focusing system quality (focal lenght)

- Fixed focus for measurements în range 0,2 – 1 m (base class)

- Manual focusing system (IR-Optiflex) for large distances and flexibility;

- Autofocus system (Laser Sharp - the operator identifies the target with a laser beam and the system measure the distance

and adjust control focal lenght) with standard lens 0,15 – 30 m (100-200 m with 2x or 4x zoom lens)

Difficult location to inspect Ordinary focusing system (manual) Focusing system Laser Sharp

Focused on the fence Focused on the target

Fig. 3 Focusing system

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- Multifocal system – the system adjust focal length taking into account the positions of objects placed at short and long

distance (4 points) too result best infrared images.

Fig. 4 Manual focus infrared image versus Multifocal system infrared image

3. Temperature range ( in °C), in which we want to measure.

If we divide temperature ranges into groups, we have:

- up to 250° C base class

- up to 650° C middle class

- up to 1200° C professional grade

We recomand:

- Buildings Efficiency -20 °C – 250 °C

- Industrial Energy Efficiency -20 – 650 (or 1500) °C

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4. Angle of view and Distance to Spot ratio (D:S)

This parameters are closely related to the focal length. The larger the focal length, the smaller the angle of view is. The

angle of view is inversely proportional to the distance from the measured object.

Fig. 5 Angle of view and focal length: IR image TI560 professional camera with standard lens (HxV 34° x 24°) and wide angle lens (HxV 48° x 34°)

Benefits with wide angle lens:

- When working in a tight space, see a larger target from a close distance;

- For building diagnostics, save time with roofing and industrial building inspections by viewing a much larger area at a time;

- For electrical inspections, see an entire bank of switchgear cabinets in tight quarters or see a wider view when looking

through IR Windows.

We can fundamentally change the distance value by a series of lenses and improve thermogram quality. However, for some

applications, you need to capture images of objects that would be very difficult to get close enough to without entering a

danger zone, climbing a ladder or maybe even using a lift or a helicopter. For these applications, the new Fluke 2x and 4x

telephoto infrared lenses magnify your view so you can see a lot more detail from the ground or from a safe distance.

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.

Fig.6 2x, 4x telefoto Fluke interchageable lenses for TI300 to TI560 series (

For example, if your infrared camera with a standard lens has a Distance:Spot ratio of 764:1, then you could stand at 764

cm from an object and see a minimum spot size with diameter of 1 cm. With the same camera and a 2x telephoto lens your

D:S is 1530:1 (15.3 m for a 1 cm spot). These capabilities make Fluke telephoto lenses a great choice for a wide range of

applications including power generation, power transmission line, and power distribution; chemical and oil and gas

manufacturing; metals refinement; building inspection or any large industrial or commercial operation.

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Fig.7 Captured image from the ground with standard lens and 2x, 4x telefoto Fluke interchageable lenses (TI560 infrared camera)

The Fluke 4x telephoto lens is excellent for capturing thermal profiles of small targets from a much greater distance. Benefits

with wide angle lens:

- See far more detail when you view your target magnified 4 times more than a standard lens;

- Identify a potential issue in your equipment, even when your target is as tiny and distant as a failed splice

on a high electrical line or failing refractory on a tall stack;

- Benefit from extra stability for your 4x telephoto lens or telephoto lens with our patent pending lens attachment system that

holds the lens securely in place.

Image captured from the same location with a

TiX560 infrared camera

and a Fluke 2x telephoto infrared lens

This shot of the Space Needle in Seattle,

Washington (height 184 m) was captured from the

ground with a

Fluke TiX560 infrared camera and a standard lens

Image captured with a TiX560 infrared camera from the same

location, with a Fluke 4x telephoto infrared lens

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Fig.8 Captured images from the ground for a dangerous place (m.t. distribution line) with a standard lens and 2x telefoto Fluke lenses (TI560 infrared camera)

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5. Easy-to-use smart interface with a minimum number of buttons (8)

Fig.9 Fluke TI401 PRO interface

6. Software with advanced image processing possibilities Choice of color palettes to highlight problem areas, possibility to describe the thermal field (by a line, rectangle,

polygon), temperature calculation Min., Max., Average values.

Robust desktop and mobile phone software is an important aspect of thermal inspection workflows. Thermography software

can help enhance and clarify images, add analysis and share professional-looking reports in applications spanning mechanical,

electrical, electronic equipment, building diagnostics and more. It’s important to note that analyzing thermographic imagery

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accurately requires special training to consider emissivity of objects and other factors that can influence temperature

measurements by infrared cameras.

Good thermal imaging software fully utilizes the radiometric data supplied by the camera’s sensor to get the most out of

the image or video.

When evaluating software to use with an infrared camera, experts recommend you check that the software includes

these important features:

1. Multiple image or video formats - Process and export images in multiple file formats such a .jpg, .tiff, .bmp, .gif or .avi as

well as proprietary formats that can tap more data for advanced analyses. Fluke infrared cameras can save in .is2 format, for

instance, for further image processing and analysis in SmartView® software, and images can be exported from this software to

many commonly used file formats. You may also choose to export the temperature data from the image to CSV or XLS format

for further analysis.

2. Edit and manipulate images - Adjust level and span, change emissivity, add markers, highlight boxes, reference images,

color alarms.

3. Combine visible light and infrared images - Adjust and blend visible and infrared images in order to better locate

potential problem areas. This is the IR Fusion® feature in Fluke software.

4. Live viewing and sharing of infrared images or video - View streaming data from your camera on your smartphone or

computer. This is available via the Fluke Connect® mobile app on some models, for example. Share images in real-time across

the internet for viewing by remote team members.

5. Remotely control your infrared camera - Some software lets you activate auto focus or capture images and other functions

without touching the camera, which can be valuable in potentially hazardous areas or tricky applications.

6. Create templated or custom reports - Best-in-class software adds options for building and customizing reports to export in

.pdf or .docx formats for sharing.

7. 3-dimensional analysis - A capability of better software programs for thermal image analysis, viewing infrared images from

different perspectives helps eliminate false positives and supports the identification of additional problem areas. Fluke’s 3D

analysis capability is called 3D-IR®.

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Fig. 10 SmartView 4.0 software for analisys thermal image în is2. format

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8. Side-by-side comparison - Important to predictive maintenance, side-by-side comparisons of images taken at different times

are included in the Fluke Connect software platform’s Asset Health dashboard.

9. Change color palette - Control colors in the image to make heat or cold easily apparent or view as grayscale.

10. Annotations - Add audio, text, and additional visible light images to help add all necessary information about an

application.

11. Categorize and catalog images - Tools to categorize, tag or catalog thermal images and associate with equipment. This

feature is built into Fluke Connect Assets software.

7. Extended connectivity: USB C, Wi-Fi, LAN, i-Phone In addition, the user can import images directly from an infrared camera’s memory or a removable memory device such as an

SD or Micro SD.

Fig.11 Fluke Connect software connect infrared camera to mobile, PC, LAN to transfer synchronized radiometric data between team members

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2. IR camera Resolution adapted to the application

2.1. Thermal images taken in favorable conditions, inside, enough light Low level IR camera (Ti25, 160x120=19.200 pixels)

Fig. 12 Door air infiltration (Picture in picture PIP, full infrared, Ironbow palette)

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Fig. 13 Cold room energy losses from an air gap (Picture in picture PIP, blending image 30%infrared-70%visible, High contrast palette)

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Medium level IR camera (FLXP320P, 320x240 =76.800 pixels = 19.200 x4)

Fig. 14 Roof room thermal insulation void – water infiltration (Picture in picture PIP, blending image 50%infrared-50%visible, Blue-red palette)

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2.2. Thermal images taken in unfavorable conditions, outside, low level light Medium level IR camera (320x240=76.800 pixels)

Fig. 15 Thermal wall insulation - energy losses, external view from an open terrace (Picture in picture PIP, full infrared image, Blue-red palette)

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High level (Professional) IR camera (TI401P, 640x480 pixels for research applications, distance=30 m)

Fig. 16 Building energy losses, external view for the university dormitory C1(Picture in picture PIP, blending image 50%infrared-50%visible, Rainbow X palette)

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Comparison between the same thermal image taken with different infrared camera in difficult

conditions, high humidity, low light in the night (Buildings Applications)

60x60 pixels (fixed focus, D:S=120:1) 160x120 (manual focus, D:S=250:1) 640x480 (Laser-Sharp Auto focus, D:S=764:1, 34°x24°)

Fig. 17 Building energy losses, external view for the university dormitory C1(car distance=6m, building distance=30m, Rainbow palette)

Object Parameter Value

Max 13.7°C

S1 -0.1°C

R1:AvgTemp -0.1°C

R1:MaxTemp 2.2°C

R1:MinTemp -2.4°C

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60x60 pixels 160X120 pixels 640x480 pixels

Fig. 18 Building energy losses, external view for the university dormitory C, left wall (wall distance=22m, Rainbow palette)

Object Parameter Value

Max (person head) 17.8°C

R1:AvgTemp -3.2°C

R1:MaxTemp -2.1°C

R1:MinTemp -4.4°C

S1 -4.4°C

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60x60 pixels 160X120 pixels 640x480 pixels

Fig. 19 Building energy losses, external view for the university Body laboratory C (wall distance=12m, Rainbow palette)

Object Parameter Value

Max HVAC System 24.9°C

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Comparison between the same thermal image taken with different infrared camera in ideal conditions

(inside) 60x60 pixels 160X120 pixels 640x480 pixels

Fig. 20 Power Apparatus Laboratory, internal view (distance=8m, Rainbow palette)

Object Parameter Value

Max 49.6°C

S1 6.4°C

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3. How to operate an TI401PRO / TI580 IR camera

for an accurate infrared image

The quality of a thermal image is much more than just aesthetics. It is critical to pinpointing specific areas of concern. A simple

way to look at it is:

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IMAGE QUALITY = focus +correct chose of object emissivity+ optics + spatial resolution (pixels + field

of view)

3.1. Basic operations

3.1.1 FOCUS on image

Focus is essential to both image quality and temperature accuracy. Like photographic cameras, infrared cameras require

good focus for the best output. This output directly affects your analysis and decision making. An infrared image that is out of

focus is likely to display bad temperature calculation data as well. Focus directly affects the quality of your image as well as the

accuracy of the temperature measurement data that you capture with an infrared camera. Indeed, a blurry image can be worse

than no image. If your image is out of focus, your measurement could be off by 20 degrees or more. Thermal imagers

calculate temperature; they don't "measure" it. In thermography, how the energy is being conveyed (conduction, convection, or

radiation) has an impact on what an imager sees. Distinct lines between objects often can disappear, making focusing a

challenge.

Manual focus systems

With a manual focus system, you should be patient and focus on an area with sharp thermal contrast, if possible. Using a

manual focus system can often be intimidating for the new user, but once you get the hang of it, manual focus provides you

with great results.

Here are a few simple suggestions to help you learn to better focus manually:

- Start with a subject in a monochromatic color palette. The human eye most often can focus in black and white (gray

scale) or black and yellow (amber) more easily than in full-color scales;

- Look for a sharp edge that you can see in the field of view. When faced with a subject where there is no sharp edge, try

putting a sharp object like a pen, pencil, or a wooden pointer in the field of view and focus on that first;

- Hold the camera still, Practice!

Automatic focus system

When you use the Fluke IR-Optiflex™ focus system at distances of 1.2 meters and beyond, you have the flexibility to perform

scan significantly faster than you could with manual focus alone, with true point-and-shoot ease of use. At this distance you can

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achieve optimum image clarity and scanning convenience. To use the LaserSharp Auto Focus System:

1. Select Camera > LaserSharp Auto Focus > On.

2. Point the Imager at the target.

3. Pull and hold the Secondary Trigger.

4. Position the red laser dot on the target.

5. Release the Secondary Trigger.

The auto focus system automatically focuses on the object.

The blurriness of the image makes it more difficult to identify thermal anomalies This image is crisper and provides more detail because the focus is sharper

Fig. 21 Importance of focus system to take a correct infrared image

3.1.2 Understanding emissivity in thermal images

Emissivity (Ɛ) is the ratio of how well a material radiates infrared energy, compared to a perfect radiator. Emissivity values fall

between 0.0 and 1.0. An object that measures 1.0 is considered a perfect radiator and is called a "black body".

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In the real world, there are no perfect radiators, unfortunately no surface emits perfectly, and materials emissivity vary in a

infrared image. This is one complication (among several others) that makes it difficult to use infrared technology to conduct

quantitative inspections that require obtaining accurate temperature measurements. Emissivity varies by surface condition,

viewing angle, temperature and spectral wavelength. Most nonmetallic materials are efficient radiators of energy. Human

skin is close to a perfect radiator with an emissivity of 0.98. A polished copper surface is at the other end of the spectrum with a

value of 0.01 and an important factor of reflection. And, as shown in the images above, the apparent temperature we see on the

sculpture changes. In these images, we might recognize the cold areas as reflecting the clear sky and the warmer ones as those

of surrounding buildings or even ourselves. The reflections are actually “thermal lies,” because the truth about reflective

surfaces is that they are inefficient emitters. These thermal images are from two different angles of a stainless-steel sculpture

located outside on a city street. Looking at it with our naked eyes, we would probably assume that the object must all be the

same temperature—the same or close to the surrounding air temperature. The thermal images, however, tell a different story.

IR image affected by reflected energy from surrounding buildings (54,1°F) IR image affected by reflected energy from clear sky (46,3°F)

Fig.22 IR images affected by reflected energy

Most of the time it is quite easy to distinguish reflected radiation from emitted radiation because, like a mirror,

reflected radiation moves when we move relative to the surface.

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Most infrared cameras have the ability to change the emissivity setting, so if you know the emissivity value of the material

you’re inspecting, you can make an adjustment in the camera to get closer to the actual surface temperature.

Fig.23 Selection emissivity using direct adjustment or a table (TI401PRO-TIX580 series)

However, if the emissivity of the material is less than 0.60, you should not expect to be able to obtain an accurate

temperature reading using infrared, and even if it is higher than that, other factors may affect your temperature reading.

A simple illustration of this is this image of a hand with a ring on it. You can see a difference in the thermal image. The ring

appears to be much colder than the hand, yet the ring is a similar temperature to the hand. Therefore, although the two objects

are at the same temperature, they are radiating different amounts of infrared energy.

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Increasing thermography accuracy on reflective surfaces

When you need high level of accuracy in measuring temperature on low emissivity (highly reflective) surfaces you can apply a

small piece of electrician’s tape firmly to the surface (following proper safety practices). Set the emissivity on the thermal

imager to 0.95 and the background correction to the temperature of what would be reflected if the tape were a mirror.

Following this process you should be able to achieve a measurement accuracy of +/–2°C or 2% of the measurement.

Thermocouple 20 °C IR Thermometer 19,7 °C Infrared camera 19,5 °C (TI401 PRO)

Fig. 24 Experimental determination procedure of emissivity for an reflective object (window with unknown emissivity)

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3.1.3 Optics

The materials used for thermal imaging lenses determine how efficiently infrared energy is transmitted to the detector, and thus

directly impact the quality of your image. Losing too much infrared energy through the optics can lead to a loss of detail in the

image. Germanium is the most efficient available material for transmitting energy to the detector and is used with special

coatings in higher quality infrared camera lenses (more expensive). So is not recommended to touch the lens, use the cover lens

when infrared camera in not in use or in an area with dust. The maintenance of lens must be done with clean and soft

materials.

3.1.4 Detector resolution (pixels)

The number of detector pixels (detector resolution) on your infrared camera is a key factor in the quality of your images. Each

pixel detects the apparent temperature of its area of the target. The more detector pixels focused on the target, the more detail

you have in your image and accurate your measurement.

3.1.5 Field of View

Field of view (FOV) works hand in hand with detector resolution in determining image quality. FOV defines the area the

imager sees at any given moment. FOV requirements vary depending on the application. For example, a wider FOV is better

for inspecting a building or an up-close look at an electrical board. At long distances, smaller objects benefit from a camera

with a narrow FOV (with digital zoom 2x, 4x, 8x or equipped with 2x, 4x fotolenses).

3.1.6 Spatial Resolution

Because both detector resolution and FOV play a key role in infrared image detail, the spatial resolution—measured in mrads

(0,47 mrad for TI401 PRO the entry level for professional infrared camera) it is an important indicator, who takes into account

both mentioned indicators. Spatial resolution can be considered as a way of defining the smallest object size that can be

detected. The lower the value of the spatial resolution, the better is the details and image quality.

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3.2. Color palettes influence

Infrared cameras provide a choice of color palettes—color schemes—on the camera and in software, that help quickly

distinguish thermal variations and patterns in an image. The color tones correspond to the apparent surface temperatures of the

target. The key is to select the palette that best shows the thermal differences for your specific application.

Some applications can be analyzed more effectively in a monochromatic palette such as grayscale or amber.

Applications where you are dealing with smaller differences in temperature are easier to see and analyze by showing an

image in a rich color palette such as rainbow, blue-red, ironbow, or a high contrast palette. Keep in mind that one color

palette may work better for on screen display and another may work better for printed reports.

Rainbow (recommended) Blue-red (recommended) Hot metal (not recommended)

Fig. 25 Color Palette for smaller differences in temperature

All Fluke thermal imagers, for example, include multiple palettes, ranging from three standard palettes to eight standard and

eight Ultra Contrast™ palettes. Standard palettes offer an equal, linear presentation of colors to provide the best detail. Ultra

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Contrast™ palettes offer a weighted presentation of colors that provides extra color contrast between the high and low

temperatures, which works best where there is high thermal contrast.

Technicians can select or change the palette in the camera and in the software as needed.

High contrast (recommended) ironbow (recommended) Amber (not recommended)

Fig. 26 Color Palette for smaller differences in temperature

3.3. Color Alarms

Some infrared cameras offer user-selectable high and/or low apparent temperature color alarms to quickly highlight areas that

are outside of the normal temperature range. On Fluke infrared cameras, when you scan the area with the color alarms activated

you see a visible light image of everything within the high and low parameters. Anything outside of those temperatures appears

in infrared. That feature gives you a quick indication of where issues might be so you can drill down into those areas.

High Alarm turns on/off the high-temperature color alarm. The high temperature color alarm shows a full visible image and

only shows infrared information on objects or areas that are above the set apparent temperature level.

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Low Alarm turns on/off the low-temperature (or dew point) color alarm. The low-temperature color alarm shows a full visible

image and only shows infrared information on objects or areas that are below the set apparent temperature level.

Area with temperature above 20 °C (in red) Area with temperature below 10 °C (in blue)

Fig. 26 Infrared image with options for High alarm and Low alarm and Spot markers (center)

User-definable spot markers

Spot markers provide real-time diagnostic benefits on the camera that were previously only available in software. Several Fluke

infrared cameras offer from one to three fixed temperature spot markers that you can position on the camera display to

highlight points of interest before saving the image.

To set the markers on a Fluke camera, go into the menu, select measurements, markers, and then the number of markers you

want. The first marker will drop into the screen so you can drag and drop it into position by using the touchscreen or arrow

keys.

Then you can repeat the positioning process for one or two more markers.

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3.4. Particular problems when inspect Buildings

3.4.1 Loss of thermal energy

It can be difficult to diagnose and solve building problems such as heat preservation, humidity/moisture invasion, roof moisture

damage, poor air conditioning system performance, structural damage and mold detection. The IR camera is a valuable tool for

these applications, enabling the building owner, architect and contractor to verify the building's performance, find potential

problems and seek effective solutions.

An exterior view of a building showing areas of

possible energy loss

An exterior view of a building with first floor warm and

serious problem of heat loss The same building with a thermo isolation system

Fig. 27 Buildings IR camera inspection

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Infrared inspections of buildings should be done in winter to obtain the best infrared images.

We require a minimum difference temperature between ambient and interior of 15 - 20 °C (maxim 5 °C at exterior).

3.4.2 Moisture and mold detection

Thermal imaging is a key to prevention of mold growth in buildings. The impact of mold on health is dependent upon the

concentration of spores in the immediate area and the allergic effect on an individual. Potential health problems associated with

mold exposure can take the form of allergic reactions or asthma. The problem is not limited to homes. Public and commercial

buildings with moisture accumulation due to condensation or leaks are a candidate for mold growth.

The best way to control mold growth is to control moisture. Mold can begin growth in as little as 24 hours. Roof leaks and

water pipe leaks are common sources of water accumulation that may cause mold growth.

Mold has closed public schools and caused communities to spend millions of dollars on environmental tests and remediation.

Infrared inspection is a fast, non-invasive method to discover moisture intrusion within the building envelope. Infrared

inspection does not directly detect the presence of mold, rather it may be used to find moisture where mold may develop. The

limitations to obtaining accurate infrared images pertain to the ability of the surface being scanned to emit heat energy.

Since the temperature difference between the wet and the dry wall are very slight, a sensitive infrared camera must be used.

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Fig. 28 Infrared images where Mold is associated with moisture and cold surfaces as result of bad building constructive structure (roof infiltration, pipe leak)

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Roof maintenance

Flat roof membranes are the waterproof barriers between the outside elements and the interior of buildings. They come in a

variety of materials and designs. They must be able to expand and contract, resist high winds and the effects of solar radiation

and withstand foot traffic. It is easy to see why roofs leak.

Normally there is little or no water within a flat roof assembly. When a leak develops, water enters the assembly and,

depending on the type of insulation system, is either absorbed by the insulation or runs to the cracks between the nonabsorbent

insulation. When water enters the roof assembly it is there for a long time, sometimes the life of the roof.

Infrared detection of water entry in roof structure is based on Thermal capacitance – that is physical property of a material's

ability to store heat. The materials in roof assemblies have relatively low thermal capacitance, especially when

compared to water. Water requires an important energy to raise its temperature and likewise must release a lot of energy to

cool.

The physics used for thermal roof inspections is that dry roof insulation heats up and cools down faster than wet roof insulation.

Infrared inspection goes beyond simply finding a leak by locating the extent of the moisture invasion of the insulation. To do

this we require solar heating of a sunny day. Then at night, after the sun goes down and the roof surface begins to cool, the dry

roof insulation cools faster than wet roof insulation.

Infrared inspections should be done in summer, under the right conditions to obtain the best infrared images. We

require a difference temperature between the day and night 20 °C. For best results at inspection is necessary: an roof clear

of snow, dirt and debris, little or no wind, an dry roof surface, no warm or cold air exhausting onto roof.

During the winter surveys are more difficult because the temperature differences are usually less than on summer surveys (5 °C

versus 20 °C). If the building is heated, the added heat flow from the building through wet insulation will help enhance the

winter thermal patterns.

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Fig. 28 Infrared images for roof water infiltrations (red area)

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4. How to best present thermal inspection results

Thermal imaging inspection reports are designed to communicate findings and produce action, such as a repair order or

further monitoring of equipment. Typically, a report includes both thermal and digital (visible light) images, and details such as

the date and time of the inspection, location of potential problems, and work order numbers. Most important, you should also

include a brief summary describing potential problems, their locations, and how critical they are.

The chief purpose of your report is to point out anomalies, but keep in mind that while you can easily see these anomalies, the

people reading your report may not be as well versed in thermography. So, it’s a good idea to use thermal imaging analysis and

reporting software to enhance those images to make the results more apparent to the untrained eye.

Three easy ways experienced thermographs enhance thermal images include:

- Adjusting level and span. Every thermal image will show a hot spot and a cold spot, which may or may not be

problematic. You can readjust the level (mid-point) and span (difference between minimum and maximum temperatures)

of your image to highlight the area of concern. That area may or may not be the hottest point in the image.

- Choosing the right colour palette. Subtle differences are easier to see with a monochromatic palette like grey scale or

amber. High contrast palettes can make it easier to quickly find obvious anomalies. You can change the palette in the

camera or in the software. Pay attention to the colours resulted at printer.

- Blending infrared and digital images. If your thermal imager has a built-in digital camera, it’s a good idea to set the

blend to 100 % thermal when you’re scanning the component. The digital camera will still be capturing the visible

image in the background. You can then blend the digital and infrared images in the software to a balance that best

highlights any anomalies you want to call attention to in your report.

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General location: Substation m.t./j.t., 12.06.2019 / 9:32

Equipment: Cell 2

Analyzed location: Current transformers

Defect description:

- Imperfect contact lower terminal current transformer-bar Al, phase R, temperature 112.2 ° C

relative to the temperature at the upper terminals of the current transformers with an average

value of 65-68 ° C.

Outdoor ambient temperature: 21 ° C

Local indoor ambient temperature: 29.3 ° C

Relative humidity: 55%

Defect severity level (for maintenance): Very severe (4)

Fig. 1.2

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