Beyond
the Usual Applications for Infrared Thermography
UPTIME MAGAZINE ARTICLE of November, 2005
By: Gregory
R. Stockton, President
8472
Adams Farm Road
Randleman,
NC 27317
(800)
248-SCAN
Introduction
Think of
the world as a radiator…infrared thermographers do.
Thermal energy travels at the speed of light in all directions. An infrared (IR)
camera detects this [heat] energy and converts it into pictures or thermographs
of heat. One can learn a lot about the world by looking through the lens of an
infrared camera.
Infrared Predictive
Maintenance (IR/PM)
If you
are trying to maintain electro-mechanical equipment, you might be interested in
knowing that heat killsbut
you already know this! Ever had a piece of equipment burn up? Think back to all
those components that went into the dumpster last year, like fuses, switches, breakers,
motors, bearings, couplings and the like.
Unless the forklift operator ran over it, it probably died a death of heat.
Here’s the good news…it got hot first. Maybe it burned in a millisecond, but
chances are it happened over a much longer period of time and if you are
inclined to watch it with an infrared camera, it will let you know it is
failing. Now, just watching it is not remedial in any way and even if it is
adjusted it may still fail, because the damage is done. But the downtime is
what is so expensive these days, so you can get another component and change it
out before it fails at an inopportune time and cost real money.
Excess resistance
is usually what causes failures in electrical components and excess friction
with mechanical devices (see figures 1, 2).
The practical use of IR/PM then, in a nutshell is: seeing the thermal energy
emitted from all objects, knowing normality and reporting only abnormality in a
graphic, usable and easy-to-understand fashion, so that someone can act to fix
whatever is wrong. This works on heat emissions from all types of objects not
just electro-mechanical. There are many uses for infrared thermography
other than inspecting electrical switchgear and mechanical components.
Process Improvement
Use IR to
make your machines run just 10% faster with just 10% less waste and profits
will soar. If you can fix a problem at the beginning of the manufacturing
process, you will eliminate waste, eliminate product returns and promote
customer goodwill. Infrared surveys are very inexpensive compared to throwing
away product that you sent all the way to the end of the line before
discovering a flaw…or worse, sending a defective product to your valued
customer, only to have it returned at your expense. Even if it is not possible
to look directly inside a machine, the effects of the machine on the product
can almost always be seen
using
IR after it exits (see figure 3).
Figure 1) Fault on electrical lug connector.
Figure 2)
Overheated electric motor winding.
The key
to process improvement infrared is to get the machine designers, operators and
industrial engineers involved in the process. They usually know all about the
machine and the process. They just need to “see” in the infrared waveband.
On-line IR monitoring of manufacturing lines is becoming more popular as
manufactures seek more efficient methods of producing goods in a competitive
marketplace.
Figure 3)
Socks exiting a boarding machine.
Non-Destructive
Testing
IR/NDT is
used to find out characteristics of an object without damaging it. In general,
there are two ways to get information about what is going on inside any object:
1) Don’t
do anything, just watch the object radiate self-generated heat, or
2) create the conditions needed to see what you want to see.
Apply heat [or cold] to the object and monitor the results, or, apply heat to
the object and monitor what happens when then object cools, or, put a heat
source behind the object and watch what happens when the heat comes through it.
There are variations on these, like vibrating the object and looking for the
friction that a crack creates.
Research &
Development
R&D
applications are literally worth millions of dollars. Only a small percentage
of these techniques and applications are published, because they are tightly
held and legally protected secrets. Often it is not as simple looking at
something and seeing a defect (see figure 4).
Instead, these techniques have been developed over the course of years and
refined by scientific scrutiny at a cost of hundreds of thousands of dollars.
Figure 4) Typical R&D set-up and software.
Facilities
There are
four types of buildings by use: residential, commercial and industrial and
institutional. All types of buildings benefit from IR surveys of heat loss,
moisture and quality control.
Building Thermal and
Moisture Envelope
Inspecting
buildings for heat loss was one of the first commercial uses for infrared thermography. As we decide to become less dependent on
fossil fuels, IR will again be used as it was in the 1980’s to monitor the
energy efficiency of buildings. In very cold climates, poorly installed
insulation and vapor barriers can lead to condensation problems and the
degradation of the building itself. Badly designed, poorly constructed, poorly
maintained, leaky buildings are not energy efficient and often have moisture
and mold problems. In some cases, damage to the building is caused by
insufficient ventilation and/or an under-designed or over-designed HVAC system.
Preventive/predictive maintenance in buildings of all types is very uncommon.
First, all buildings should be kept dry during the construction process. Then,
all buildings should also be tested within a few months after construction or
major renovations to the structure, the thermal envelope, the moisture envelope
and the HVAC system.
Figure 5) Concrete block wall on a commercial building wall.
Building Quality
Control
Infrared thermography can be used as a building quality assurance
tool. Almost all building materials will retain heat energy and therefore can
be checked for quality of installation. Improper installation of insulation
and/or seals in buildings can be seen in the form of heat loss and air leaks.
Also, building components “inside” the walls, ceilings and floors are
recognizable because of their differences in mass. For example, infrared thermography can be used to determine the presence and
correct placement of grouted cells in concrete block walls (see figure 5). If the owner of a new block building
spends a little money checking their [low-bidder’s] work with infrared thermography, the contractor will be forced to build the
building per specifications or face the added direct cost of repairs and
resulting loss of schedule repercussions.
Roof Surveys
A well
prepared, graphic and accurate map of the infrared signatures of a roof can be
of tremendous benefit to a building roof owner at all stages of the roof’s
limited
life. Knowing where the subsurface moisture is located will help the roof owner
manage his assets.
Figure 6) Aerial photograph, aerial thermograph and CADD drawing of a
flat roof.
This form
of predictive maintenance works well on many types of flat and low-slope roofs.
Here are the basics: At night, areas of roof moisture are warmer, because the
accumulated heat (from daylight sunshine and heat) in the trapped water mass is
greater than in the dry, functioning insulation or roof substrate. After
sunset, as the roof’s structure cools down, the wet areas of roof insulation
and other materials maintain higher temperatures because of their higher mass,
allowing the infrared cameras to detect the sources of heat and record them for
later analysis. There are two ways to perform IR roof moisture surveys: on-roof
and aerial.
On-roof thermographers walk from roof to roof looking for
subsurface moisture patterns and when found, mark the extremities of these
areas on the roof with paint. Aerial IR is used when the owner wants to
document the wet areas with straight-down photos, IR and CADD drawings (see figure 6). The biggest advantage of aerial
infrared is not its use on roofs that have well-defined areas of moisture at
all, but those roofs that are the most difficult to image from any distance or
angle. I am referring to the roofs that, for instance, have a lot of ballast,
are covered with reflective coatings or ones that for whatever reason are impossible
to image from the roof. With high-resolution aerial imagery, slight nuances of
temperature can be seen from far enough away to recognize the pattern of heat.
Other Applications
There are
industry-specific applications, i.e., auto, steel, etc., and many more. The
point is that there are too many to list. With modern infrared cameras,
software and computers, infrared thermographers today
are almost never limited by the infrared equipment’s ability to measure
temperatures or discern differences in temperature. Rather, we are only limited
by our imagination. So, get an IR camera and look at the world in a different
wavelength. You will be amazed at what you see!
Gregory R. Stockton
is president of Stockton Infrared Thermographic Services, Inc. The North
Carolina-based Corporation operates seven application-specific divisions
performing many different infrared services in the US, Canada, Central and
South America. Mr. Stockton has been an infrared thermographer
since 1989 and has published fifteen white papers and numerous articles on
infrared thermography. Greg is the infrared editorial
board member for UPTIME Magazine and will publish a series of articles on the subject
of infrared thermography.