For those who have a periodic thermal imaging program, to what extent do you expect the motor (not MCC) to be thermally imaged?
Some recommended equipment guide lists list the motor as a separate item to be thermally imaged. The answer I've received from several "experts" have
Some expect that the peckerhead should be removed and the motor started up and the connections imaged. This in addition to imaging the outer surface
Others believe these connections to be a low risk item and not worthwhile. They further contend that by disturbing the leads, it adds additional risk by potentially causing the lead connections to be shorted against the box casing.
At first glance, its hard to argue against either recommendation. But I would appreciate your thoughts on this.
We open every peckerhead annually to get a thermal image of the leads. it is amazing how many bad connections we have found the first time through a plant. This stems from maintenance personnel not being properly trained on motor terminations to motor shops that...well...SUCK. Usually after the first time through removing the peckerhead is more for an inspection for abrasion. Occasionally we will find a lead that has worked itself loose.
Scanning new installations is a priority as well, better to catch the problem during the warranty period.
When scanning the peckerhead it only takes a few seconds more to look at the entire motor. Having a thermal scan of a motor bearing is nice when I find a problem with vibration. I can back up my claim most times when a bearing is failing if it appears hotter than normal.
st. louis mo
I don't think there is much risk in removing the peckerhead cover. The motor leads should be capable of being moved around slightly without much risk. If moving the leads around slightly exposes a problem, it's probably better that you find it in controlled conditions.
I agree with jim2f that following construction is an excellent time to find problems. I'm always NOT surprised with how many construction problems show up at start-up.
I'm starting to form the opinion that if you scan right after construction and then one year after, that you will find a majority of connection problems. After that, I might suggest opening the peckerhead less often unless the motor is in highly critical service.
May be my question will look silly but hope you will reply.
You guys are talking about taking a thermal images of Motor Termination. Per my knowledge for thermal imaging the requirement states that the equipment shall be running with minimum 40% load. So how can you take images of running motors? I mean you are opening the terminal box when it is running? How we can comply with NFPA 70E with Motor Thermal Imaging?
My intention is learning here only.
Thanks for your great clarifying questions. Opening terminal boxes while the motor is in operations is NOT recommended. You can, however, power down and open quickly thereafter and, typically, still see any residual thermal signature of a fault. Or you can open it, power up (with appropriate safety precautions) and view it. Signatures will usually show up with less than 40% load but they will be very subtle so use a very narrow span setting and don't ignore anything.
I would agree that findings in the terminal box are not unusual. Also look at bearings (should be close to casing temperature, see attached problem), overall casing temperature (should be less than rating minus 20C) which can indicate internal air flow blockage, and coupling patterns (vary based on type).
IR is not a substitute for good Motor Circuit Analysis (MCA) testing or vibration testing, but it is a great way to quickly look at many motors and flag anything that needs further investigation.
Thanks for input Therm and John
At our facility, we CANNOT open peckerhead while operating. Only after shutting down, tagout, opening cover, tagout, setting up barrier controls,start sequence.
So you can see the manpower involved to perform PERIODIC inspection.
After taking all your ideas and discussing with Electricians and owners of equipment, I think we've come up with some guidance that will work for us here locally.
Again appreciate all your comments and views.
By the way, years ago was called to investigate a "burnt" odor reported on one of our main feed pumps. Apparently it was subtle, others did not smell anything out of ordinary. We did tag out procedure and opened peckerhead to see one of the phases clearly hotter than the other leads. Problem was we couldn't determine exact location since entire wrapped connection was hot.
In this case, we stopped motor to let it cool for a few hours. Then watched IR at startup. It was amazing. The heat profile clearly identified exact source (it was the motor lead crimp) which showed itself within 5 seconds of start.
At that point, Thermal Imaging proved itself to management and workers better than any pulpit preaching from me