In our facility, we are in a state of change in regards to the procedures and methods for removing non-hinged panels on electrical cabinets for the purpose of thermal imaging inspection. The primary concern is the risk of access covers entering the live circuits.

I dont know where we will end up yet as the electrical community is evaluating commercial standards and how it applies to our current procedures (we are not a commercial facilty but often adhere to the same principles).

I suspect that we may get to a point for many cabinets that the effort and manpower to perform tagout procedures will simply outweigh the benefit of performing the inspection.

I appreciate your thoughts and experience on this
Jim Powers

Two good options to consider:
1. Hinge some of the presently non-hinged panels
2. Use IR windows or viewports. While there are still no clear guidelines for these devices, many are pushing ahead, based on reasonable professional assessments, and getting excellent results

A third option, but a distant third in my opinion, is to rely exclusively on airborne ultrasonic detection. I'd favor the use of both ultrasound and IR but don't like to only rely on one or the other.

John
Thanks for the response.
We are looking into both those options you mention but because of our infrastructure - nothing will happen quickly.

I guess I was just wondering if other companies are finding a need to address the recent changes to safety concerns (arc flash in particular) as we are.

Thanks again
Jim P

John:

ivibr8--what voltage and what arc class are you concerned about? Are you referring to panels or switch gear?


John--how is ultrasound a substitute for IR? How can you rely on it to find resistive type faults?

Many, but not all, resistive problems exhibit micro-arcing and, as a result, produce detectable ultrasonic activity. As I said, I'd far prefer using it WITH infrared, but sometimes exceptions are necessary.

John, I have a hard time buying this concept on low voltage equipment. I guess it is possible. We have all seen heat damaged components on 480V and lower equipment. However, I believe that the ingredients for an arc to form are different for those to form simple heating. An arc requires a loss of metal to metal contact so that electricity jumps through the air. Thus, there must be looseness and movement. Without movement, the arc will extinguish. Alternatively, the presence of heating due to oxidation, contamination or reduced contact surface does not requirement movement and should not be expected to produce an arc. This type of problem should not be detectable by ultrasound.

So, I suppose an arc is possible, but I also expect it will be a small percentage of the problems identified through IR. I think the use of ultrasound would miss the vast majority of electrical problems.

I think that often, what people claim is arcing, on their 480V or 208V equipment, is actually the movement of internal components in the magnetic field, within the breaker. The next time you think you have one of these, take a spectrum of the ultrasound. I will bet you will see nothing but 60 Hz harmonics. That would be buzzing in the magnetic field.

The concept of a sustained low voltage arc, that is troubling. Perhaps others can weigh in on whether a low voltage arc can be sustained to the point that it is detectable by ultrasound in a reliable manner.

In the past, I have attempted to use ultrasound in the manner John suggests and concluded it was not an effective technique. Perhaps others can take their ultrasound instruments on their infrared surveys and try to prove or disprove the concept.

This message has been edited. Last edited by: Testtech,

I very much appreciate your opinion and experience. I agree we need to learn more by our careful observations. I've always been amazed at the amount of melted metal that can be found in a seemingly tight connection and have assumed it began with micro-fretting that then moved on to active melting (and probably arcing). I'd value the feedback of others with experience.