I've got to say, I just love to world of Reliability. It’s exciting to become involved with companies as they begin the journey toward reliability-centered maintenance and away from the old conventional wisdom of run-to-failure. I've worked in maintenance for over 25 years now, and it has been quite an adventure. In my current role I have the pleasure of being able to help people along the knowledge path, and it’s very rewarding.
One of the more amusing aspects of what I get to do is seeing how people respond to learning about all of the tools they have at their disposal to help them keep their equipment running. Sometimes though I get to see responses on the other end of the spectrum; when folks learn that there are more limitations to the technology they have than they realized. One of those instances comes when in Level I we reveal that infrared isn't the primary test method for electric motors. You should see the stares I get. Usually folks look at me, thinking “Umm, this is a course on infrared thermography and you’re telling us that this isn't the best time to use it?” Well, that’s not quite the case.
As we state in Level I Thermographic Applications, generally speaking when it comes to electric motors, IR isn't the primary test method for the discovery of failure modes. The types of conditions that lead to motor failure can be picked up in their infancy with other technologies. Electric Motor Testing (EMT) for example is the best way to discover turn-to-turn shorts in motor stator windings. They’re discovered because of their impact on winding impedance balance. Sure, I can see stator faults thermally, but not until they have reached a stage where they are producing sufficient heat to be detected on the motor case. EMT can find that sooner. Vibration analysis can find mechanical issues in a motor much sooner than they impact the motor thermally. Same with airborne ultrasound; I can hear a bad bearing ultrasonically much earlier in its failure than I could see it with a thermal imager. But that doesn't mean infrared isn't useful on motors.
Many fledgling reliability programs start out with one or two technologies. Often IR is one of the first implemented. When it’s all you have, obviously you want to do all you can with it. If you can’t apply EMT or Vibe to a motor, you obviously should scan it thermally. Using techniques like thermal mapping or trending of the motor condition will reveal thermal anomalies much sooner than quarterly route inspections would. Or if your program consists of Vibration Analysis and IR, thermography is an excellent tool for correlation of your vibe findings. Viewing a potential failure from two perspectives is certainly advantageous, and can ultimately lead to discover of failure modes sooner than the application of a single technology.
So is scanning motors worth it? The answer is a resounding “Yes!” Infrared isn't, in my opinion, the primary technology for determining faults in motors but it certainly has its place in the tool box and should be applied along with other reliability measure for overall motor health.