FORWARD Stockton Infrared Thermographic Services, Inc. (SITS) has been performing infrared surveys of electrical switchgear for about 10 years. Due to the marketing efforts of our company and many others, the word is getting out. By now, almost everyone in electrical maintenance has seen an article about how infrared thermography (IR) has saved a piece of electrical switchgear from an imminent explosion. In fact, on a daily basis, most practicing infrared thermographers find big problems on the electrical systems that they are checking. At least weekly, IR contractors (because they more often look at previously uninspected switchgear) discover a problem that if left unattended would cause a world-class failure, explosion and fire. An example of one of these is shown in figures 1 & 2, where the warmest bolt was 909 degrees F. This is the very nature of electrical thermography. Albeit slower than we in this industry wanted or expected, IR predictive/preventive maintenance (P/PM) is becoming a regular part of the maintenance of electrical equipment.
Thermographers, who challenge themselves to explore new markets, develop new techniques and improve the body of infrared knowledge, reap the financial and intellectual profits. The beauty of infrared is that the opportunities seem to be limitless. Here are two examples: Part I is about an improvement of technique over the current on-roof method of finding water that is entrained in the insulation of roofs. Part II is about a new method for inspecting the concrete reinforcing in CMU (block) walls.
(PART I) ROOF MOISTURE SURVEYS
ABOUT ROOFS AND ROOF MOISTURE SURVEYS Everything wears out. Roofs are no exception. The ravages of sun, wind, rain, snow, hail, ice, chemicals, leakage and time will eventually cause every roof to fail. Just like electrical switchgear, it must be maintained. To the owner of a building, a roof warranty might seem to be the answer, however roof warranties are written by roof manufacturers. They are designed not to protect the owner of the roof, but instead to limit the liability of those writing the warranty. Vaguely written roof warranties, which do not define words like "regular" or "routine" or "maintenance" will come back to haunt the owner. Roof owners should have some kind of agreement with their roofer or roofing consultant to inspect the roof at least once a year.
Waterproofing problems manifest themselves in two ways: leakage and entrained water contamination. Leakage is pretty simple, although the leak inside the building rarely directly relates to the exact spot on the roof where there is a hole, which you already know if you ever tried to track one down. Since most types of insulation absorb a certain amount of water, it is harder to find the contamination because the roof may not develop a leak (in the building) until the insulation has absorbed all the water that it can hold. There are basically three tools that owners can use to find the subsurface water. Nuclear gauges-which count neutrons, capacitance meters-which measure resistance, and infrared-which measures heat. Both nuclear gauges and capacitance meters allow a technician to take a (sample) reading on a 5' X 5' or 10' X 10' grid on the roof. When plotted on a roof plan, these measurements are used to extrapolate where the water is. They work well of roofs that do not gain or lose much solar energy and therefore do not lend themselves to infrared. Some roofs and insulation types or combinations do not even absorb water.
For roofs that do absorb water, infrared is the preferred method. Here is how it works. During the day, the sun radiates energy onto the roof of the building and into the roof substrate, then at night, the roof radiates the heat back into outer space. This is called radiational cooling. Higher mass (wet) areas retain heat longer than the lower mass (dry) areas and therefore radiate heat for a longer period of time, because it takes longer to cool. Infrared cameras can detect the heat and "see" the higher mass (wet areas), during this "window" of uneven heat dissipation.
ON-ROOF INFRARED SURVEYING
To perform an on-roof survey, you need a crew of three to four people. You need one experienced thermographer, one thermographer's helper and one building owners' representative for access and security. Hopefully he/she will know the history of the roof. Also, it is a good idea to have a roofer or roof consultant there. If questionable areas are found, he can first use his (non-destructive) nuclear or capacitance meter to test them, and if needed, take core samples and competently repair them. You need access to the roof and plenty of time to collect data. Depending on how many problems are found (very dependent), a crew can survey ~200,000 square feet of building roof each night. Usually, areas that contain subsurface moisture are outlined with marking paint directly on the roof and marked on a drawing. Infrared images are stored on videotape and/or on-board flashcards. The next day, after thermograms are printed, at least one of the crew goes back on the roof to take visual photographs of the areas that are considered to contain subsurface moisture. The report includes infrared and visual imagery (example shown in figures 3 & 4), the roof plan marked with areas of suspect moisture contamination and a videotape of the entire survey. That would characterize an on-roof survey correctly performed.
HOW MOST ON-ROOF INFRARED THERMOGRAPHY IS DONE TODAY
Most roofs never see an infrared survey. The ones that do by and large are done by roofers or roof consultants not infrared thermographers. I recently presented a short course on infrared thermography at a large plant maintenance and engineering show. On my way to work the booth with our salesmen, I made it a point to go to all the roofing companies' booths and talk with the reps. Not to my surprise - every roofing company, every roof consultant and every roof manufacturer offered infrared thermography as a service of their company. A full 85% of these companies have their own infrared cameras. The other 15% have a contractor of some type to perform surveys.
The quality of infrared surveys & reports that are currently being performed on roofs is seriously sub-standard due to the fact that infrared thermographers, who are trained and paid to perform surveys and make reports, in most cases, do not do the work. Instead, the vast majority of roof surveys are performed by roofers who do infrared as a sideline.
The reasons that the quality is low is that:
Some roofer-thermographers frankly, do not know how or when to perform a proper roof moisture survey. They are never trained.
* Often, the large roofing (and engineering) companies have one camera in the company or region, and it is shipped to whatever office might need it, with written 'instructions' on its operation! * Some use IR cameras that were never designed to produce soft or hard copy of the images. * Some use IR cameras that are not capable of measuring slight enough differences in temperature so that discernible hard copy can be printed of the areas of suspect contamination. * Many think that since IR "pictures" won't turn out anyway, that instead painted marks on the roof or photographs will suffice. * Many do not even think that a "thermographic" report is necessary, because it is really not the end product which is to fix the roof.
WHAT IS WRONG WITH THE TYPICAL NIGHT UP ON THE ROOF
Let's go scanning:
First we need an IR camera - any kind will do - because no one will ever see the images anyway.
Now we need a guy who knows the roof - this is really important! When we see that bright spot out there - he can save us a lot of time by telling us that it is an uninsulated patch that was applied two years ago or confirm our suspicion that an area has "had problems" or "has leaks".
We need some meters lots of them.
We need something to dig a hole in the roof to verify what we are seeing - because many of the warm areas are going to be either reflections, heavy flood coat, heavy ballast, the effects of heat-producing equipment on the underside of the roof, or old patches under the latest roof. We could even have water trapped/sandwiched between two good roofs.
We need a photocopied fire plan of the plant, which is the best that the owner can supply, as our roof plan. Somebody is going to have to draw in those forty-two air conditioning units on this thing.
We will find some warm blobs. If our building owner's rep cannot explain why they should be there and after metering it and punching a hole and finding water we got ourselves a finding. Tomorrow we will climb back on the roof if its not raining and take a photo. Hey let's take a photo of the core sample!
The problem with the typical roof survey is that it is performed by people, which have something other than infrared that they are really selling. They do not do infrared surveys for a living; they are not performing the survey for the sake of the report, so they do not see the necessity of keeping up with the latest equipment or techniques. The thermographic end product is not their end product. As a result, the quality of the work is sub-standard and of course, the reaction to the report is displeasure. The true agenda is to sell roofing, consulting services and/or roof repairs. Infrared thermography is a means-to-an-end and not an end in and of itself. Because of this fact, IR is sometimes given away as a loss leader, which are seldom great products.
WHY DON'T THERMOGRAPHERS DO ROOFS?
There are several reasons that IR thermographers have failed to take advantage of this tremendous potential market.
It is difficult to schedule, perform and write a report for a Roof Moisture Survey. Even if a company is getting good money for a survey, roof surveys are often difficult jobs, even for a professional thermographer. Even with the image quality, portability, handy image storage capabilities, improved software and computerized reporting systems of the latest IR cameras, the logistical considerations of the job and thermal dynamics of a roof structure make it a tough job to perform well. Also, there are many different types of roofs, membranes, fastening systems, substrates and insulations that are used to construct the roof system, which have to be considered.
Because it is sometimes used as a loss leader, the prices for IR on roofs are held artificially low, making roof jobs unattractive to infrared companies. No one can blame an engineer for buying roof infrared from a roofer when:
He does not know the quality difference between products.
He cannot find an IR company to bid on the survey.
He has some level of trust in his roofer to start with. They may really be an excellent roofing company.
It is easier for an infrared thermographer to make a living doing electrical IR. This is the case. Electrical IR is proven, accepted, graphic and fairly well understood by the engineering community as important in the short term. It is much easier to sell an electrical survey.
Roof problems are not emergencies, therefore roof surveys are not deemed as important. Unless water drips onto the final product line or into the switchgear panels, it is not an emergency. Buckets can be placed under the leaking area for a quick fix. Roofers are painfully aware of this fact, and roof P/PM programs often suffer as a result of inadequate funding.
WHAT TO DO ABOUT IMPROVING THE QUALITY?
In order to perform a really good infrared survey, you need to have a good working knowledge and experience about roofs and about infrared thermography. While there may be a couple of infrared companies that have well trained roof consultants working for them, and there may be a couple of roofing companies with really well-trained infrared thermographers, they are few and far between. Even if there are a few they can't possibly perform IR on 1/1000th of all the roofs.
We are doing a lot of aerial roof work for roofing companies and roof consultants. They let us know what they want in an infrared report. They want high quality infrared thermograms and visual photographs that their customers can understand. They want scaled, accurate drawings of the heat they can figure out what is causing it. The answer for roofers is to hire excellent thermographers. The answer for infrared thermographers is to perform excellent surveys, make excellent reports and let the roof experts work over the data. Many of these guys are actually very good at roofing.
Infrared thermographers are not (and should not profess to be) experts on every single thing that they inspect, but there is always someone out there that can get to the true problem, if given a well prepared thermographic report. The same holds true for roof surveys. WE ARE NOT A ROOFING COMPANIES; WE ARE INFRARED COMPANIES!
HOW AND WHAT HAPPENED WHEN WE WENT TO THE AERIAL PLATFORM
We have been performing infrared roof moisture surveys for eight years and for the past three years, we have been using aerial infrared almost exclusively for our roof clients. Aerial IR started for SITS, when I attended IR/INFO in January, 1996 and saw the presentation "Aerial Infrared Remote Sensing - Selected Applications", by Lawrence R. Davis, Davis Aviation. After the presentation, I found the author and told him that I was interested in hiring his company to do all of our roof moisture surveys. I told him then; that I thought his market was working for infrared thermographers that were having the same problems I was, surveying roofs. After seeing his paper, I knew that hiring a company that could do the roof a lot better than we could, was the right thing for our clients and our company.
Literally overnight, we started producing Qualitative Aerial Infrared Roof Moisture Surveys that were far, far superior to our previous reports.
To get this new service 'off the ground', I went first to all my roof clients who, to my surprise resisted, sighting every conceivable reason not to do aerial IR. They were happy with my on-roof method it had worked before and they were quite creative with reasons why not to change. I answered all their objections with the exception of painting the roof. I showed them scaled AutoCAD drawings, and explained that this way was superior. But, they liked being able to climb up on the roof, walk the repairman up to a marked area, step down firmly and hear the unmistakable squishy sounds that are moisture contamination. The only valid reason that they could come up with for staying with the old method was the marking. So, I told the hard liners that after we flew the roof, I would take the AutoCADs and my trusty marking device up on the roof and mark the wet areas. Problem solved. It was great flying over jobs that we had done previously, which had not yet been repaired. I could see all those warm blobs - in seconds - that we had struggled for nights and days to document.
Next, I went to all my electrical clients, sat down with them and played an aerial video. Many of these people did the surveys because they trusted me when I told them this was the proper way to maintain the roof. Some of them, I had never approached because I did not want to do their roof. Some had roofs that were heavily ballasted, had multiple levels, many patches, and some so dangerous looking, that we hated to go on them to check the air conditioning and dust handling equipment.
Then I started calling on companies that we had never done business with. I found that sometimes they were more interested in our other services, so not only did we get aerial work, we also picked up some electrical and other contracts as a direct result of marketing aerial infrared.
THE DIFFERENCES BETWEEN ON-ROOF AND AERIAL INFRARED
The cameras that we use to use for on-roof surveys were not of sufficient thermal or spatial resolution to obtain good imagery from our minimum flight altitudes of 1000 feet AGL (above ground level). Most modern infrared cameras have 256 X 256 pixels, a total of 65,536 pixels. The infrared cameras that we use for Aerial IR have 512 X 512 pixels, which total 262,144 pixels. We use a specially modified Cessna 182 to perform the surveys. A helicopter will work, however high operating costs, vibrations, and slow ferrying speeds make a fixed-wing the best option for us.
Very little time is required to obtain the infrared data, once the aircraft is over the building. Usually, a 200,000 square foot building is imaged in less than 5 minutes. This will include multiple passes over the building from varying altitudes, attitudes, speeds and angles. This spring we surveyed a two million square foot tire manufacturing plant in less than 20 minutes over the building! The imagery is recorded on digital videotape and/or captured directly onto a computer. The visual photographs are taken earlier in the day or the next day.
When the thermographer returns to the office, the image processing begins. The visual photographs are developed and the thermograms are saved on the computer. The infrared images and digital or "scanned-in" photographic images are used to make an edited videotape of the passes over the building. Both visual and infrared images are used to do the analysis by overlaying the infrared images "over" the AutoCAD, to draw in the areas of suspected moisture contamination. The result is a report where visual, infrared and AutoCAD components (printed and video) are well matched and lined-up.
The same laws of physics apply to both aerial IR and on-roof IR. We need a dry roof surface, low winds, no rain and few clouds on the night of the survey. Of course the "window" when the roof is radiating heat differently from wet and dry areas, has to be longer in order to do an on-roof survey. One very big advantage to aerial is angle of view. We used to climb up rickety ladders with $80K cameras to get as high above and as close as possible, to a 90 degree angle over a particular area, to avoid reflections and image a larger area. Aerial has the advantage of looking straight down over the target, and access to multiple levels is never a problem. The drawing dimensions are close to perfect, which is a big problem with on-roof.
There are three distinct advantages that on-roof surveys have over aerial.
* If you are on the roof, you can look underneath rooftop equipment with marginal results. * If you take along a roofer or roof consultant, he can verify wetness (or lack of wetness) before the report is prepared. * You can mark suspect areas of the roof with paint, then and there.
Aerial infrared has every other advantage over on-roof.
There is no comparison. Image quality* is superior by every standard (examples shown, figures 5-8).
*By image quality I am referring to the overall usable quality of the imagery. Last summer, we were performing some on the ground infrared wall work in Florida. We found ourselves within 100 miles or so of a roof job which needed to be done right away. The airplane was 800 miles away. Since we were doing on-ground work, we had the cart and decided to try the Mitsubishi 600 up on the roof. Of course, the resolution on the 5' X 5' wet sections that we were imaging was better, due to the fact that we were only a few feet from the roof. However, the quality of the imagery (to see an outline of heat from the moisture contamination) was inferior to what an aerial shot of the same sections would have been.
Angle of view allows for accurate marking of areas of suspect roof moisture contamination on AutoCAD drawings and later, if needed, directly on the roof.
Visual images, infrared images and AutoCAD drawings are lined-up.
Improved reporting allows the end user to understand the report much easier.
We can wait for the PERFECT NIGHT and survey lots of roofs under ideal conditions.
Instead of tying up four people for a night to perform a survey, we can use an airplane crew of two, and do 50 times as much data collection. Then, while it rains or snows, we can process the data not in a hurry on a freezing cold night but at our own pace in the office.
If we do not like the image we are getting from a roof, we can come back at different times of the night in order to catch the "window" at just the right time.
SPEED OF DATA COLLECTION
Instead of 200,000 square feet in a night, as much as ten million square feet can be imaged in a night.
Since there are a limited number of perfect nights in a year, a company needs to survey as many square feet of roofing as possible on these perfect nights.
SAFE AND NON-DESTRUCTIVE
Unless something falls off the plane nobody will ever get hurt, and a hole will not be cut in a roof while performing an aerial survey.
BELIEVE IN WHAT YOU DO
The only reason an infrared thermographer ever has to lay down a meter or cut a hole in a roof is if he does not trust the infrared. At that moment, he stops being an infrared thermographer, and starts being a roof consultant. OUR JOB is to excellent at what WE do. Leave the touching to others! Do you wiggle that high voltage wire to make sure it is loose? Of course not. You have learned to trust IR, make reports and let somebody else take the connection apart.
Since roofs cost several dollars per square foot to repair, knowing where the water is (it got there through a hole, tear, or leak around a penetration), is a very cost-effective means of planning the extent of repairs. Building owners have tremendous investments over their heads. Extending the life of the roof will save them a lot of money. Also, their motivation may be, for example, to use this information to plan budgets, look at a building before they buy it, or to put some teeth into a new roof warranty. That's right, a lot of our work is on new roofs. They get baseline information to compare at any time in the future, and catch any installation problems. This is real roof asset management!
(PART II) CHECKING THE PLACEMENT OF GROUTED CELLS IN SINGLE-WYTHE CMU WALLS
Another virtually unexplored application for infrared thermography is its use as a quality assurance tool for Concrete Masonry Unit (CMU) building walls. It is not hard to find these buildings. Your local schools, malls, strip shopping centers and retail buildings were probably built using this type of construction. CMU walls are erected fairly quickly. Due to their load bearing capabilities, relative low cost, fire ratings, versatility and a wide selection of decorative outer faces, they are popular as inside and outside walls in these types of buildings.
Heretofore, determining the placement of reinforcing grout in single-wythe (contiguous) CMU walls has been a painstaking and destructive undertaking. Usually, a test is performed because, by accident, missing cells are discovered when a wall penetration is retrofitted or change order is executed, requiring the wall to be opened. Often, a hammer or hammer drill is used to punch holes where the grouting is supposed to be. The test results are used to extrapolate to the extent of the problem. This method falls short, since the sample is so small (1/10,000th of the wall), that only outright fraud can be found, and excess grouting cannot be determined. This is where IR can help. It is quick, non-destructive and accurate.
HERE IS HOW IT IS DONE
As with roof IR, the sun does the energy loading. After sunset, wall areas that contain concrete are warmer (higher mass) because the heat from daylight sunshine radiates from these areas longer than areas with empty or insulated cells (lower mass). As the building structure cools down, we go to each wall section (buildings use a grid line system based usually on structural column lines) and stand far enough back to get a column on the left, and a column on the right in the image, for reference purposes. Of course, you want to catch the building when it is radiating the largest delta-T between the pilasters (concrete filled cells) and the rest of the wall.
The trick is timing.
The building goes through a heating and cooling cycle over the course of 24 hours. At dawn, the outside temperatures rise; the sun warms the air and more importantly shines directly on the walls. At this point the pilasters are cooler. At sunset, the outside temperatures fall and the pilasters are warmer (example shown in figure 9 & 10). Under ideal conditions, this lag time between the two different masses, allow us to see (depending on many factors) as much as a five Fahrenheit degree delta-T. Now, to an IR thermographer that is a significant delta-T. Just about any IR camera can detect where the concrete is. I can see it easily with my Hughes Probeye, however, that is the best case scenario. Many factors affect the absorption of energy into the wall and radiational cooling out of the wall. Lee R. Allen (AAIT Corporation) and I have been working on a methodology for years and we still have not figured out exactly when to look at a wall. The delta-T is usually no more than a degree or so and the window does not always last very long.
There are lots of other factors that affect the cooling and heating cycles:
* wind, * the weather (as nearly as we can figure for about the 60 hours prior), * moisture content in the wall itself, * the orientation of the building to the path of the sun during different seasons of the year, * what's going on thermally inside the building, * emissivity of the paint on the wall (and how dry the paint is). * and more
(PART III) CONCLUSIONS
To an infrared thermographer, the world is one big radiator. Energy and the transfer of energy is happening everywhere around you. We can explore the world with eyes that nobody else has. With our modern infrared cameras, software and computers, we are almost never limited by the camera's ability to measure temperatures or discern differences in temperature. Rather, we are limited by our knowledge of how hot the object that we are looking at should be. It is our industry's challenge to figure how to improve what we are doing, come up with new uses and techniques for gathering and disseminating infrared data effectively and efficiently.
Gregory R. Stockton
“R.A.I.” the Reliability.aiTMChatbot
You can ask "R.A.I." anything about maintenance, reliability, and asset management.