There are a great number of things you need to remember as a thermographer: the general rules of thumb about conditions, remembering to check imager settings, not forgetting to remove the lens cap. Maybe that last one only applies to me, although I hope I’m not the only one…
One thing that is supremely important is awareness of your surroundings. Obviously, situational awareness is linked to safety. Think about the hazards you could encounter in the facilities you typically inspect. Trips, slips and falls come to mind as do other workers, both on foot as well as on motorized apparatus of one kind or another.; Then there’s the machinery that moves in its operation, like cranes or palletizers. Chemical hazard areas, hot surfaces, the list goes on and on. In fact, this list is so comprehensive as to warrant deeper discussion in a future tech tip.
What I was thinking about in authoring this piece though was the impact your surroundings could have on your inspection efforts. Recently I had an opportunity to spend some time with a customer/colleague I’ve known for a number of years. As with many of us who love this technology, he was bursting at the seams to share a recent find with me and the conditions around it that had him scratching his head for a moment.
This particular fellow happens to work for a large utility provider and was performing an inspection at a generation station. His task was to inspect an outdoor overhead bus that was not enclosed in a bus duct but was exposed. It was a breezy day, but the bus was somewhat shielded from the convective action of the winds. He was imaging from the ground, and right at a junction between pieces of the bus where a bolted connection was located, he detected a thermal pattern that was quite odd. It appeared to be varying from warm to cool, emanating out from the mechanical junction point in both directions along all three phases of bus. He showed me a video, and it was pretty mind-blowing. Imagine those expanding and collapsing graphics showing varying volume in an audio application. It looked like that, only more irregular. So odd in fact, that he recorded video with the intent to show it to others to get their input.
Now mind you, this man was not permanently assigned to this site, but he was being accompanied by someone who was assigned there daily. When he showed the video to the host employee, he cocked his head at first too, and then asked precisely where this was. Together they walked back out to the spot, shot the bus again, only to see the same pattern. The host employee turned around and looked much higher into the sky than the bus was, but in the opposite direction. Pointing he asked, “do you think it’s maybe that?”
Behind and above them was the exhaust stack of the boiler for the generator. The wind was making the exhaust gas pattern very erratic, so the reflection of it on the bus looked to be kind of shimmering, which was part of why it didn’t immediately come to mind as a reflection because they are so often quite regular in appearance. As you should recall from Level I, the high reflectivity of the bus material is what makes it especially susceptible to displaying thermal reflections. In this particular case, we had one specific source for our odd appearing signature, but there are many other potential sources. Anything really that’s a different temperature than the reflective surface or ambient; clouds if you’re outside, other people, furnaces, kilns or even colder surfaces such as chilled water pipes.
Always be aware of your surroundings, for safety’s sake of course, but also take that extra look around when you find something out of the ordinary. The answer might be right behind you.