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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 seperate item to be thermally imaged. The answer I've received from several "experts" have varied.
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 for uniformity.
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.

Regards
Jim Powers

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We open every peckerhead anually 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 personel 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.
RM
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.
RM
May be my question will look silly but hope u will reply.
You guys are talking about taking a thermal images of Motor Termination.and as per my knowledge for thermal imaging you required the equipment shall be running with minimum 40% load. So How you taking images of running motor?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 & regards
RM
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.

Attachments

Images (1)
  • Bearing_2Website
RM
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 aal your comments and views.

By the way, years ago was called to investigate a "burnt" odor reported on one of our main feed pumps. Apparantly it was subtle, others did not smell anything out of ordinary. We did tagout procedure and opened peckerhead to see one of the phases clearly hotter than the other leads. Problem was we couldnt 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, TI proved itself to management and workers better than any pulpit preaching from me

Jim Powers
RM
I "feel your pain" and appreciate your cautious (and I think correct) approach. Depending on the size of the box you may be able to install an infrared transparent window or viewport. I know some are doing this on larger terminal boxes. Clearly on smaller motors this is not an option.

I would warn readers that you can NOT reliable check leads with the cover in place, despite the fact that many continue to try it. Now, if you happen to see a hotspot on a closed cover, DO TAKE HEED as it is likely to be much hotter inside!

Also, if you are doing Motor Circuit Analysis (MCA) diagnostic work, a hot phase should show up during the online testing. If you are not yet using MCA, I would strongly suggest you consider it for both online and offline testing.
RM
When we used to do MCE testing, we found that visibly damaged bugs more often than not accompanied significant peckerhead resistive imbalances. On the other hand, infrared will find motor bug termination defects well before they reach the point of burning the tape. In my opinion, IR is a much more effective technique for finding peckerhead problems then micro-ohmmeter based methods. If you can get access, infrared is the best way to find bad peckerhead bugs. I have attached a couple of bad bugs found by MCE.

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RM
we are using IR windows/Viewports for HV/MV SwitchGear Inspection but they are looking so thin which are designed for switchgear only and its difficult to say that it can fullfill the Integrety of Motor Termination Box( which might be Ex-d,Ex e or Ex p and having arround 10 mm Terminal Cover thickness)
Any Example /pics of view ports on Motor terminal box can clear my view , so most appreciated any picture / photo regarding this.
thanks
RM
Sledder is right; often during investigation of variances in temperature of your leads at the MCC you can track it back to the peckerhead and high resistance. However, this is not the way to test a peckerhead, in this day and age we do the best we can sometimes. With facilities where NFPA 70E strict interpretation and LOTO procedures make it cheaper to burn up the motor than to open it for inspection, you may have to work with what you have. These variances may be subtle and more inexperienced technicians will only note that there is only a few degrees difference. The thermal profile of the equipment is often as important as local temperatures and many thermographers get hung up on temperature only. Of course it will vary on how much resistance there is in the poor connection as well as the length of the run and load conditions. I stress it should only be used as added information and not as proof of no anomalies found. I find it's often better to keep these little things under your hat because if you tell the client that's how you found the issue, they will automatically assume that you can find all of them that way and try modifying inspections to eliminate proper inspections. It is not an indication until you can prove it to be so, until then it’s an anomaly that requires further investigation.

Ty Keeth
Infrared Thermal Imaging, Inc.
www.itimaging.com
tkeeth@itimaging.com
RM
Probably its not very much essential to take thermal image of motor body because it will only tell you the body temperature which will be representing winding temperature. But if you know that bearings are the most sophisticated part of the motor and the very first effect comes on bearing. the winding gets effected when bearings gets damaged very badly. and thats the stage when you can easily identify a problem in motor without aid of any specialized system like ir thermography.

If you are running vibration analysis in parallel it will indicate you at very initial stage and your thermography of motor body will be just a scrap
RM

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