After several months of lobbying for it, you finally got approval for a testing firm to come in and conduct an infrared survey of your electrical distribution panels. The results were much worse than you expected.
The survey showed most, not just a few, of the bolted connections are bad. You asked the plant engineer to schedule some downtime for repair. He responded with, “We know those connections are good, because we have PMs that require tightening them. Your thermography results are wrong.”
How do you resolve this conflict?
Theoretically, it is possible for thermography results to be wrong. But not if a qualified thermographer conducts the survey and analyzes the results.
The existence of the fastener tightening program is evidence in favor of the thermography results because this maintenance practice actually degrades connections. If they come loose, fasteners should be replaced rather than restretched. The clamping power of a bolt is achieved by stretching the bolt to its elastic limit, and you get that only once (doing it again produces about 50% of the original clamping power).
To conclusively resolve this conflict, perform AC resistance or conductivity tests across a sample of connections the thermography identified as bad.
