Infrared thermography is a useful inspection tool to help
locate problems in steam reformers while the units are online
and fired. There are three main areas in a reformer that can be
efficiently inspected with thermography. While there are common
and codified inspection and diagnostic practices used in the
industry today, some of these practices are unknowingly wrong
and may have a large impact on the data collected over the
Before explaining how thermographers can inspect steam
reformers, it is necessary to address what these units are,
along with their main purpose in chemical and petrochemical plants. Steam reformer
furnaces are used for hydrogen production. A hydrocarbon feedstock is mixed with steam and
heated in the presence of a catalyst to produce crude hydrogen,
which is then purified. The most common hydrocarbon feed is natural gas, but
propane, butane or liquefied petroleum gas (LPG) are also
Steam reforming takes place in a steam reformer furnace. The
furnace is usually a large refractory-lined box with gas
burners, heating many catalyst-filled tubes that carry the feed
(natural gas) and steam. Depending on the design, the
reformers firebox or cell may contain only a single row
of tubes (Figs. 1 and 2) or
it may contain multiple rows (Figs. 3 and
4), making it more difficult to obtain
accurate temperature data.
1. A horseshoe-type
design with one row of tubes
2. Side view of a
horseshoe design reformer.
3. Single firebox-type
design with multiple rows of
tubes in one firebox/cell.
4. Side view of single
firebox/cell design reformer.
Refractory and insulation problems
The most obvious use of thermography on a steam reformer
furnace is to consider refractory and insulation problems.
Because of the high temperatures inside the reformer, the steel
shell is lined internally with refractory material to prevent
burn through, efficiency loss and structural failure.
When inspecting the refractory on a reformer, the key is to
notice large differences in temperature. Many variations in
temperature and thermal patterns will undoubtedly be found
throughout various sections of the reformer, so knowing the construction, process flow, heat
transfer principles and emissivity variables is very important
in determining whether an indication is relevant or
Refractory furnaces are usually painted with a metallic
silver paint (Fig. 5). Emissivity is an
important issue when it comes to temperature accuracy. While
many inexperienced thermographers and inspectors take
emissivity for granted, temperature accuracy is an important
aspect of reformer refractory inspection, as it assists design
and plant engineers in troubleshooting safety and efficiency
5. Low-emissivity silver
paint common on reformers.
The low emissivity of the paint not only poses a temperature
measurement problem, but it also poses a relevant indication
determination challenge. Surrounding a reformer is a melee of
hot flanges, piping, and vessels that can easily be reflected
off the surface of the paint, resulting in false indications.
Plant inspectors using spot radiometers often misinterpret
reflection problems as true indications. Also, changes in paint
surface conditions due to scrapes, scuffs and charring can
result in emissivity changes and can show a Δ T >
40°C, easily confusing an inexperienced thermographer and
leading to data misinterpretation.
With reformers, the most common areas for refractory
problems are at the peepholes (Fig. 6),
burners, manways and penthouse roof flooring, although it is
not uncommon to find problems in other areas.
6. Thermal image of
refractory failure located
around a peephole.
Burner firing efficiency
Because the main driving force behind steam reforming is
heat, a reformer has many burners (usually natural gas burners)
that fire directly into the fire box. A reformer is usually
fired from either the top or sides or sometimes both.
The way a burner fires is crucial to the reformer efficiency
and to the service life of the refractory and catalyst tubes.
Ideally, the flame will fire inside the box, but not impinge on
When inspecting inside a reformer with thermography, a
3.9-micron filter is used to see through the gas flames.
Although the flames will not be visible during the inspection,
the flames thermal pattern from the surrounding tubes,
walls and burner tiles can be observed.
Performing a thermographic survey of the burners and burner
tiles can help determine whether the injectors used are
functioning properly, if the burner is firing and if the burner
tiles are overheating (Figs. 7 and
8). Proper burner firing is important to
maximize the efficiency and service life of the reformer and
7. Thermal image
showing flame impingement
on burner tiles due to
improper or defective burner
8. Thermal image
displaying replacement of a
new design burner injector
tip, solving the flame
impingement problem of
the burner tiles.
Reformer catalyst tubes
This part of the inspection is one of mystery, controversy
and misconceptions. The main problem with inspecting reformer
tubes is attempting to determine the tube surfaces actual
temperature. It is common knowledge that the most effective way
to use thermography to ascertain temperature accuracy is via
means of reference. This usually means using a contact
thermometer or a known emitter.
The problem with reformer tubes is that obtaining reference
temperatures is easier said than done. Depending on how many
tubes and rows there are in the reformer, obtaining reference
temperatures to cover all tube areas is usually impractical.
One controversial issue is how to take the best reference
temperatures. Some argue that embedded thermocouples are best,
while others vow that a gold-cup pyrometer is better for the
job. Some folks even fabricate their own reference coupon from
the same tube material.
It may be surprising to learn that although temperature
accuracy is extremely important with reformer tubeswith
the industry rule of thumb being that every 20°C rise above
the maximum design temperature of a tube halves the tube
lifetemperature accuracy is not required to identify and
diagnose most tube problems.
Single-point infrared pyrometers
Almost every petrochemical plant uses a portable,
handheld spot infrared pyrometer to trend and monitor tube
temperatures (Fig. 9). The main reason plant
engineers and operators use these devices is because they are
relatively inexpensive and easy to use. They are also very
accurate and stable; they are almost never used properly by
plant engineers and operators. Users have the notion that all
they have to do is aim, pull the trigger and get a temperature.
Many fail to understand that these instruments are infrared
thermometers and are susceptible to the same errors as thermal
imagers and other infrared thermometers.
9. Single-point (spot)
Spot-infrared pyrometers are very useful to plant personnel and
do help tremendously in trending reformer tube
temperatures. However, knowing the equipment limitations and
basic infrared theory is extremely important and definitely
required before anyone uses these devices to monitor reformer
Application and equipment training programs specifically
geared to the plant operator and engineer on the proper use of
spot-infrared pyrometers are important (Fig.
10). From observing a wide array of training programs
across a variety of companies, it has been determined that
temperature consistency within 1°C to 6°C has been
achieved from operator to operator, where previously it was an
average of 20+°C (Fig. 11).
Fig. 10. Plant
and inspectors approach
a reformer for hands-on
11. Plant operators
and inspectors applying
the knowledge learned
On some reformers, temperature accuracy cannot be achieved on
certain tubes using spot-infrared pyrometers, mainly because of
spot size limitations. That is why it is better to be
consistent and precise rather than accurate when it comes to
operators and plant inspectors trending reformer tube
temperatures on a frequent basis. With a consistent and precise
temperature trend, inspector error, calibration drifts and
minute variations in tube temperatures can quickly be
identified. If problems can be identified quickly, then
corrective measures can be taken and there will be much less
chance for an actual tube problem to go unnoticed.
Accuracy can come later on, during troubleshooting or
diagnostics of problems found during routine trending and
monitoring. This approach is usually recommended because
achieving temperature accuracy for most reformer tubes can be
an expensive and a time-consuming job. This makes it
impractical and unfeasible for most routine tube monitoring
programs by operators and plant inspectors.
Although spot-infrared pyrometers are invaluable and
extremely cost-effective tools, they should be used regularly
by plant personnel to grasp the temperature trends of their
reformer tubes.Complete thermographic survey using a
radiometric imager should always be performed. This is because
an imager will be able to locate and diagnose tube problems,
while a spot-infrared pyrometer cannot. The pyrometer can only
give a temperature measurement at the point it is aimed. To
locate and diagnose tube problems, a complete thermal pattern
and profile of all relevant tubes should be viewed.
Thermographic imaging survey
With reformer tubes, operators are looking for overheating
problems. Some common problems that can be found with
12. Side view of
reformer tubes in a certain
row showing normal
13. Same reformer
as Fig. 12, but a different
row showing flame
impingement problems due
to damaged burners.
Can thermography be used to locate reformer tube leaks?
Finding such a leak is somewhat tricky, but not impossible.
Although the leak may not be seen, there are some telltale
signs to look for. These include: localized flame impingement,
due to afterburning at a location where there is not supposed
to be any; and localized cooling of the refractory wall or an
adjacent tube, indicating that a surrounding tube is leaking
(Figs. 14 and 15).
14. Leaking tube
detected by cool band on
adjacent tube and localized
afterburning of hydrogen gas.
15. The same leaking
tube as Fig. 14, crimped
while online. This stopped the
afterburning and tube
overheating with no downtime
and no failures.
As mentioned earlier, there are various reformer designs.
This means that there are also various tube configurations. A
reformer can have vertical tubes or horizontal tubes. One such
example is the convection section within a horseshoe designed
reformer (Fig. 16).
16. Horizontal convection
section reformer tubes in a
horseshoe design reformer.
Pigtail-reformer tubes can also be inspected. Pigtail tubes
are the smaller tubes that are external to the furnace and
connect the reformer tube to the supply and exit manifolds
17. Location of multiple
reformer tube rows and
pigtail tube sections within
a single firebox reformer.
18. An overheated
pigtail tube section.
19. Another overheated
pigtail tube section.
A meaningful tube survey
Reformer tube inspection is sometimes said to be an art.
There is so much that can happen inside a reformer and not all
infrared equipment can effectively deliver useable data. To
conduct a meaningful thermographic survey or even a
spot-infrared pyrometer survey, know the equipment limitations.
Limitations are what make reformer tube inspections difficult.
Inspectors often run into problems because they do not identify
these issues. The biggest limitations are:
To achieve a meaningful reformer tube survey, first
determine the surveys desired result (Figs.
20 and 21). Then identify any
limitations before and during the survey, and know how to
correct or avoid them. Reformer tube inspections may seem
difficult and require thermographers who can think and adapt to
ever-changing conditions, but the information that is gathered
during a proper infrared survey is worth every penny to the
plant and every eye-stinging bead of sweat to the
20. Direct view of
reformer tubes from
peepholes give better
temperature accuracy, but it
is more difficult to diagnose
problems due to limited field
of view for a complete
21. The same reformer
tubes as Fig. 20, with a side
view from parallel peepholes
to give a complete thermal
profile making it easier to
However, this decreases
temperature accuracy due
to viewing angle.
Proper inspection and training
Steam reformer furnaces are high priority pieces of
equipment. A failure in any of the three areas discussed can
result in a loss in efficiency or even a total unscheduled
plant shutdown. Repairs can be very simple to very extensive,
requiring days and sometimes weeks of downtime. Proper and
regular thermographic inspection of a reformers three key
areas is essential to the operation and life of the unit.
No matter what infrared equipment is used, proper training
and experience are essential. Without proper training and
guidance, too many important factors are frequently taken for
granted or are unknown to the inspector. These unknowns may
lead to premature failures or a loss in total confidence in the
reliability and effectiveness of
infrared technology. HP
Sonny James is founder and owner of
Thermal Diagnostics and the NDE Institute of
Trinidad. Both are located in Trinidad and Tobago. He
is an American Society for Nondestructive Testing
(ASNT) nondestructive testing (NDT) Level III
certificate holder in various NDT methods (including
infrared) and is American Petroleum Institute (API)
510 certified. Further, he is accredited as an
American Welding Society (AWS) certified welding
Mr. James has over 20 years of experience
inspecting reformer and heater tubes and has
established tube inspection and monitoring training
programs for the petrochemical and chemical
industry. He is routinely called upon by plants
around the world to help troubleshoot reformer and
heater tube problems and to come up with solutions
for in-house temperature monitoring and accuracy
programs. Mr. James is considered as one of the few
specialists and experts in reformer and heater tube