INFRARED IMAGING TECHNIQUES
Thomas Kremser, Altheus Infrared, Inc.
An infrared thermographer could be described as
an individual who uses thermal imaging cameras to detect anomalies, based on
heating or cooling. Every object on
earth gives off, or radiates heat, which can be captured through the lens of
the infrared camera and is converted to a heat-map picture. The thermographer is the person who captures
the heat-map photo, usually in an effort to detect the cause of a heat-related
problem. He is essentially an industrial
photographer who uses specialized equipment that allows him to take infrared
photographs and measures temperatures by means of a camera.
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| Guide Sensmart C Seires |
For instance, in an industrial application where
the thermographer is scanning electrical components, his job is to look at each
electrical panel or motor control center bucket, comparing similar components within
the bucket, looking for hot spots that otherwise should not be there - loose
connections, blown fuses, failed overload heaters, etc.. Once an anomaly is detected, he then captures
an infrared photo and a visual photo of the anomaly and documents all relevant
information related to it. The data can
then be presented to someone (a supervisor, manager, engineer), so that they
can evaluate the problem and determine the course of action for repair.
Documentation
While today's infrared cameras are amazing, a good
quality infrared photo is not always guaranteed. Using a high resolution infrared camera will
provide the tools to get started, but one should approach the subject like that
of a photographer. It is extremely
important to select the right lens, to properly frame the scene, obtain a sharp
focus and to sufficiently control the gain and contrast of the image being
recorded.
Gather as much relevant and supportive data as
possible during your survey. Many of
today's infrared cameras include visual photo capabilities, live video capture
and some even include microphones for adding audio comments. Having these components are helpful and
important, but they should not be relied upon exclusively. A good practice is to create a worksheet that
will allow you to record all of the information required to allow the repair
technician to locate the component, order the correct parts and gather the
proper tools and knowledge to make a quality repair.
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| Sample template for recording electrical scan data. Compact format allows for several problems per page. Reminder boxes helps avoid forgetting to document information. Custom forms may be created for different types of scans. |
The worksheet should include a place to log the
infrared photo number and possibly the visual photo number, if grabbed
separately. It should also include a
place for equipment ID numbers as well.
In addition, it is very helpful to document all of the data required to
be able to get the repair technician to the component in which you
scanned. From experience, as well as
from feedback from the repair technicians, I tend to work from large to small
or from general (i.e. building name or number, floor or level, area, etc.) to
more specific (i.e. MCC room name, MCC number, panel name, etc.). It is also helpful to include a section in
the worksheet for a quick description of the problem.
Details can be added later in the report, but a
rough description of the anomaly will allow you to differentiate between
several similar problems (infrared scans of motor control centers, for instance, can
often lead to multiple very similar problems with only subtle differences).
Framing the subject
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Infrared photo taken with Guide Sensmart's camera 640x480 infrared camera with 35mm lens.
Note the use of clouds in the background to minimize the contrast between the hot spot and the background.
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However, by simply moving around, one can
generate better detail from the infrared photo.
Clouds, for instance help make a warmer background than the cold of deep
space. A different position can help
eliminate solar reflections off of reflective materials. It can help make sense of a cluttered photo
(as in the case of the pole mounted Potential Transformers shown).
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| Moving around to the side, the pole is now in the background of the hot spot, allowing the thermographer to have even more control over the amount of contrast in the image. Also, by changing perspective, the hot spot is easier to identify. |
Use the best equipment available to you for the
best quality photos. This includes not
only the best IR camera, but appropriate lenses, digital cameras and other data
gathering tools (such as a strobe light for rotating equipment or a moisture
meter for roof & stucco scans, for instance). If you run an infrared service company, every
photo presented to a customer is a reflection of your skills.
Consider the lens and/or the distance to the
subject. Lens choice and/or the distance
you are from the subject you are photographing should be considered. By using a wide angle lens (or, if that is
not an option, a greater distance) you can put the subject of the infrared
photo in better perspective with the surroundings.
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| Infrared photo taken with Guide Sensmart's camera, 640x480 infrared camera with wide angle lens. Note the hot spot is only a small point in the lower right; but, by capturing the entire battery in the photo, determining which cable is at fault is now easy. |
Conversely, a longer focal length lens will allow
the customer to see more detail without putting the thermographer in harm's
way. It will also allow the subject of
the scan to fill the image, providing the detail needed for the most accurate
temperature measurement and diagnosis.
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| Infrared photo taken with Guide Sensmart's infrared camera with close-up lens. Zooming in to the subject will allow the repair technician to see exactly what to expect and to see if more than one component is affected. |
Image Quality
Be careful to not allow the hot spot to be too
saturated with too much of one color.
This may mask other potential problems within the photo. Saturating the photo with too much of one
color may impress upon the recipient that the hot spot demands immediate action,
but, it may actually be covering-up the source or potential cause of the
heating. If the camera cannot
automatically reduce the amount of saturation in the photo, switch to manual
mode and control it yourself.
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With the bad cable saturated in white, the likely cause of the heating cannot be determined.
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Reduce the amount of saturation within the image,
but also consider choosing a palette that will make it easy to pinpoint the
problem and to understand the specific heating within the problem. This may mean working on the thermal imaging
camera in a familiar palette, and then editing the image in the infrared
software in a different palette.
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Reducing the amount of contrast in the photo will
eliminate saturation and allow the engineer or repair technician to see the
source of the heating. Changing color
palettes may enhance the problem and allow the viewer to see more detail
surrounding the hot spot.
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Visual Photos &
Reports
Consider the final report when grabbing your photographs. Many infrared cameras now include built-in
visual cameras. If you plan on using the
visual photo from your infrared camera, make sure that the image is clear, well
lit, and that it conveys the information the infrared photo may be missing such
as perspective, tag information or other visual clues to help locate the hot
spot.
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Given enough ambient light and a good quality built-in visual camera...
the built-in visual photo may be all that is needed for a quality visual photo.
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Save time and create meaningful reports by using
the built-in features of your camera and software. Some cameras such as the TP-9 and Eas-IR9,
capture both the infrared and the visual photos simultaneously. A good clear visual photo with the infrared
image overlaid can be very effective in helping determine the location of the
hot spot, even when it is not obvious to the naked eye.
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| Using the software to overlay the thermal image on the visual photo in the report can be very effective when the hot spot is somewhere on a large surface with no reference points. |
Some infrared cameras incorporate a light built
into the camera, as in the TP-9 and Eas-IR9, to brighten the photo; however, a
light is no substitute for a flash when it comes to documenting moving
components. A separate digital camera
with a flash will capture clear photos of moving equipment such as couplings
and universal joints... turning a hot streak on an infrared photo into an
undeniable issue.
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| Using a camera with a flash in certain instances provide the next level of information for the repair technician. A streak detected on an orange peel coupling is verified with a digital camera. Other information such as the size, type and model of the component can also be gathered for the repair technician within the visual photo. |
Conclusion
Always approach thermal imaging with an eye of a
photographer to get the highest quality photo.
Record the data with a mind toward the repair technician to help him
make the most informed decisions about repairing the anomaly. Present the report in a manner that ensures
your work is respected and professional.
And always use the best equipment for the job.
Thomas
Kremser, President, Altheus Infrared, Inc.
Thomas is
the owner of Altheus Infrared, Inc., a full service Infrared and Ultrasound
inspection service company providing surveys of nearly every industrial
application. Thomas remains a full-time
thermographer since 1995. Altheus
Infrared uses Guide Thermal Imaging Cameras almost exclusively, including the
TP-9, EasIR-9, TP-8, IR-928, with multiple lenses and extended temperature ranges to meet nearly any application.
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