FLIR thermal imaging cameras reveal what’s behind the flames
Petroval uses both cooled and uncooled thermal imaging cameras from FLIR Systems for technical audits
A wide variety of industries relies on furnaces
and boilers for manufacturing processes. But furnace and boiler
equipment is prone to failures from a variety of mechanisms. These
include coking that plugs the inside of tubes and impedes product flow,
slag build-up on the outside of tubes, clinker damage, under- and
over-heating, flame impingement on tubes due to burner misalignment, and
product leaks that ignite and cause serious damage to the equipment.
These failures cause not only quality problems;
they can also shut down an entire process line. FLIR thermal imaging
cameras can detect most of these equipment problems during operation,
and at an early stage so failures can be prevented. This allows an
orderly shutdown and component replacement, thereby reducing maintenance
costs and production losses
The French company Petroval was one of the first to
recognize the potential of thermal imaging for technical inspections of
industrial installations. “Before thermal imaging cameras were
introduced there simply was no thorough way of finding failures during
operation”, explains Jean-François Tournieux, project leader at
Petroval. “Using FLIR thermal imaging cameras is a great non-destructive
method to find such failures even during operation – and accurately
determine at what production speed it is still safe to operate.”
Petroval inspected this crude distillation unit furnace.
The Normandy, France, based company is owned by
TOTAL and Eurecat and was founded in 1990. In addition to the head
office in Le Havre, Petroval also has an office in Houston, Texas, since
2003, and will open an office in Singapore in 2011. Petroval provides
services in more than 50 countries around the world; in fact more than
80% of the work is done outside of France
Cooled and uncooled
Currently Petroval uses three thermal imaging
cameras from FLIR; one with a cooled detector and two with an uncooled
detector. The cooled thermal imaging camera is the FLIR Agema 550 with
heat shield and flame filter. This camera is mainly used for inspections
of the inside of the furnace. The two uncooled thermal imaging cameras
are the FLIR ThermaCAM P50F, which also contains a flame filter, and the
FLIR P640, which is mainly used for insulation inspection from the
According to Petroval's technicians all three
cameras are great tools for his purpose. “The FLIR Agema 550 is very
accurate and sensitive. The FLIR ThermaCAM P50F is not as sensitive to
small temperature differences, but because it has an uncooled detector
it is maintenance free and it takes less time to start up, for a cooled
camera usually has to run the cooling system for about five minutes
before it can be used. And the third one, the FLIR P640 is the perfect
tool for both insulation inspection and for detecting faults in
The inspection with a thermal imaging camera from FLIR revealed a hot area due to flame impingement on the tubes at start up.
FLIR P640: maintenance free and perfect for predictive maintenance
The FLIR P640 thermal imaging camera has an
uncooled microbolometer detector that produces thermal images of 640 x
480 pixels. The FLIR P640 has some very useful built-in features that
make it ideal for predictive maintenance, such as a laser pointer,
Picture in Picture and FLIR Thermal Fusion to merge the visual and the
thermal image. “The FLIR P640 thermal imaging camera is very quick and
easy to use. It’s great: even from a distance of fifty to a hundred
meters you can still detect small hot spots that indicate insulation
FLIR GF309: state of the art
The FLIR Agema 550 and the FLIR ThermaCAM P50F
are both ‘older’ models that are not currently marketed by FLIR Systems.
Today, the FLIR GF309 is the state of the art technology currently used
for furnace inspections. In addition, this new model is a dual use
thermal imaging camera that can not only be used for high temperature
industrial furnace applications, but for thermal inspections of
mechanical or electrical components as well. That makes these cameras
ideal for monitoring all types of furnaces, heaters and boilers,
particularly in the chemical, petrochemical and utility industries
The FLIR Agema 550 contains a cooled Platinum
Silicide (PtSi) focal plane array (FPA) detector. Platinum Silicide has
been waived as a detector material because the PtSi detectors are less
sensitive then indium antimonide (InSb) detectors, which form the heart
of the new FLIR GF309 thermal imaging camera. This choice also allowed
FLIR to market dual use thermal imaging cameras with better
performances, because InSb detectors are more stable and more sensitive
than PtSi or BB uncooled microbolometers.
The InSb detector in the FLIR GF309 thermal
imaging camera produces images with a resolution of 320 x 240 pixels.
Both the detector and filter are cooled with a small Stirling cycle
cooler to near cryogenic temperatures to improve quantitative
sensitivity. It has been built to withstand temperatures above 300°C,
which allows temperature measurements up to 1500°C, and visual
inspection of internal furnace and boiler components that would
otherwise be obscured by flame, combustion gases, and dust. The camera
produces real-time video images, but individual video frames can be
captured as still images. The images can be viewed through a
high-resolution viewfinder, and on a 4.3”, 800x480-pixel color LCD
display. Custom-built to see through flames, the GF309 also features a
detachable heat-shield designed to reflect heat away from the camera and
camera operator, providing increased protection.
Hot spots on these ducts indicate faulty insulation.
The FLIR GF309thermal imaging camera has a
flame filter, a spectral waveband filter that allows only thermal
radiation with certain wavelength to pass through to the detector.
Flames emit much more thermal radiation at certain wavelengths than at
other wavelengths and at certain points in the spectrum a flame emits
hardly any thermal radiation at all. A flame filter is a spectral
waveband filter that only allows thermal radiation with those specific
wavelengths through. The flame filter incorporated in the design of the
FLIR GF309 restricts the spectral sensitivity to a range of 3.8μm -
The small grey area indicates the part of the spectrum where the combination of high camera sensitivity and low flame emissivity makes it possible to see through flames.
Because everything but that specific part of
the spectrum is filtered out, the thermal imaging camera can now see
through the flame and make temperature measurements straight through
even exceptionally hot flames. This makes thermal imaging cameras
equipped with such a filter ideal for furnace inspections.
Due to the built in flame filter the FLIR GF309 thermal imaging camera can see through flames and even measures the temperatures behind the flames.
Thermal imaging cameras from FLIR are a great
tool for predictive maintenance in furnace and boiler installations,
according to Tournieux. “If you use thermal imaging cameras you know in
advance what the weak points are. If certain tubes have flaws, for
instance, you can buy the replacement tubes in advance and minimise the
Finding the faults quickly with a thermal imaging camera
There’s a multitude of furnace faults you can
detect with a thermal imaging camera, Tournieux explains. “You can see
whether the refractory is damaged, whether the flames have the right
shape, and sometimes you can see dust deposits on tubes, which cause
poor heat transfer and typically lower the temperature of the product.
Refractory blocks can fall off, causing damage to burners and fired
tubes. You can also see burners that are not lit, or burners causing
flame impingement on the tubes. But we also look for oxidation
development. Oxidation is a bad sign, for eventually the oxidation will
peel off, leaving a weak spot. Temperature measurements with FLIR
thermal imaging cameras help to make sure the entire process is working
“Temperature measurements also reveal coking
that is taking place inside the tubes, usually due to excessive
temperatures, and locations where there are tube restrictions or
outright plugging”, continues Tournieux. “In some cases over-firing can
cause temperatures that exceed the tube metal design criteria, and
coupled with pressure inside a plugged tube may cause a rupture and
leak. These will show up on the camera’s image display, along with
actual temperatures of metal surfaces.”
A cabin furnace as seen from a distance of about 80 meters using the FLIR P640 thermal imaging camera.
Coke formation on an Ultrafiner Reactor Charge Heater.
FLIR thermal imaging cameras do more
According to Petroval's technicians point
temperature devices such as thermocouples provide too little information
of what is actually going on inside the furnace. “Inspection ports
provide a view of internal parts, but flames, combustion gases, and dust
obscure fired tubes and burners when the equipment is operating.
Temperature measuring devices like thermocouples can help discover some
problems, but they only measure a single-point. Thermal imaging cameras
from FLIR do more than measuring the temperature in one point.
Temperatures can be read from every single pixel in the 320 x 240 or 640 x 480 pixels thermal image.
“Using the FLIR Reporter software we can
analyse the recorded thermographic data to pick up the smallest thermal
details”, continues Tournieux.
Skin thermocouples or the welds that keep them in place can deteriorate over time. With a FLIR thermal imaging cameras that have been corrected for emissivity the temperature readings from the thermocouple can be validated.
The thermocouple probe is inserted in the furnace. Tournieux then uses the temperature reading to accurately correct the thermal imaging camera for emissivity.
One of the most important goals of furnace and
boiler inspections is validating temperature readings from
thermocouples, according to Tournieux. “Thermocouple contact measurement
devices or the welds that keep them in place can deteriorate over time
and the measurement data becomes less accurate. In many cases refineries
can operate at a much higher production capacity, but because of the
inaccuracy of thermocouple readings the production is kept within a safe
margin. Using our FLIR thermal imaging cameras we can find out if the
temperature readings from the thermocouple are correct. When we have
validated the thermocouple readings refineries are usually able to
safely increase production.”
“Before we had thermal imaging cameras from
FLIR there was no way to validate the temperature measurements of the
thermocouples”, continues Tournieux. “We didn’t know if it was safe to
improve the yield. Now we can very accurately say whether or not it is
safe to do so. Many of the refineries we visit are producing at 30,000
tons a day, for instance, and due to our inspection they would find out
that a production of 32,000 would also be safe.”
Years of experience
But anyone who thinks that performing furnace
inspections is just a matter of point and click will be disappointed,
according to Tournieux. “However important having the right thermal
imaging camera might be, there’s a lot more to it than that. The
operators here at Petroval have many years of experience in performing
thermal imaging inspections and analysing the data, but also with
industrial furnace and boiler installations.”
“To name an example: we use special probes that
we have made ourselves to make sure the thermal imaging camera is
accurate. We insert the probe in the furnace and hold it next to the
tube we want to look at. Inside the probe a thermocouple we know to be
accurate tells us the exact temperature on that location. We then change
the emissivity settings in order to make the temperature measured by
the thermal imaging camera match the temperature measured in the probe.
Because the emissivity is different for each material that is used we
have made a probe for just about every type of tube that is used in
industrial furnace installations.”
Inspection ports provide a view of internal parts, but flames, combustion gases, and ash obscure the equipment during operation. A FLIR thermal imaging cameras with a flame filter is not hindered by such obscurants.
FLIR thermal imaging cameras: the best method for furnace inspection
“But if you have the expertise and the right
equipment then using these thermal imaging cameras from FLIR really is
the best method for furnace inspection”, concludes Tournieux. “It’s a
great non-contact, non-destructive way to gather both qualitative
information and quantitative information that can help prevent or