Last year, the maintenance department acquired a thermographic camera. Larry, the senior electrician, performs all of the thermography. This particular camera was specified for its simplicity and ease of operation, thus as the plant engineer said, “Avoiding the need to send someone to school to learn how to use the thing.”
Over the past year, Larry found 62 hot connections in various panels. All of these were tightened during occasional short shutdowns for retooling, shift changes, and so forth. Yet in five different panels, operational interruptions were traced to connections that didn’t show up as hot during Larry’s scans. Half of the tightened ones also failed. Now doubting the technology, the plant manager wants a factual determination from you.
Panel connections create one of the greatest challenges to thermography, due to all the reflective metal present. Untrained and using an entry-level camera, Larry produced many false positives and missed actual problems. The technology is fantastic, it’s the implementation that’s bad.
The corrective measure was incorrect. It’s best to use a thermographic camera to identify suspect connections, and then conduct a low ohms test across each of those. Where a connection is bad, what you do depends upon the type of connection. For screw terminals, you can generally re-use the screws but not the lockwashers that go with them. For bolted connections, replace the hardware and torque to specifications.
