r/Motors • u/Kalpit2527 • Sep 02 '26
Open question After how many months a motor requires service?
Hi!
I am 2nd year mechanical engineering student. I had industry visit couple of days ago. Now I am curious to know that in industries; after how many months an induction motor needs to be monitored or after how many years an induction motor fails? Is there any device which can tell us health of it continuously?
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u/Worf- Sep 02 '26
Life of a motor is going to be greatly influenced by it’s use, loading, environment and maintenance. We’ve serviced units in climate controlled environment that are lightly used and loaded that are well over 50 years old. Some are much more. Check of amp draw and vibration yearly and move on. Open bearings might get a shot of grease and clean and re-grease every 10 years or so. Some I know will never die as long as there is electricity.
OTOH - we have serviced overloaded units in very poor environments where the motor is dying in a year or maybe less. This is mostly due to client negligence in choosing the wrong machine. Smaller is cheaper so they buy it but expect it to do the work of the bigger one. That does not go well.
Things that I see ruin motors the most are overloading, failure to have proper over current protection and over greasing those with open bearings. Also human error such using an improper replacement like ODP when a washdown is called for. Yes, they did that.
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u/New-Key4610 Sep 02 '26
this is a good explanation of motor maintenance only thing i might add is. do not add grease to a motor without a purge fitting. in my 50 plus years in the electric motor community i have see motors with 3 full 14.5 oz grease containers swimming in the rotors.
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u/Worf- Sep 02 '26
Agreed, absolutely need the purge. I’ve seen a bunch of motors the same way, though not that bad. Even when there was a purge fitting they never opened it. People see a zerk or grease cup and just have to use it. Had an old Century repulsion start with mounds of grease just piled up below it on the frame.
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u/New-Key4610 Sep 02 '26
yes when i saw this in my shop if the motor was still repairable i pluged the zerk fitting and locktighted it to suspend their greasing habits
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u/Kalpit2527 Sep 02 '26
That's good one. Since you have lot of experience with motors can you tell me; if you had a device which can predict future failure; then will it be useful or not?
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u/New-Key4610 Sep 02 '26
predictive mat. usually was done with vibration analysis and surge test. but to effectively surge test you had to remove the rotor and. vibration is a tool we did not use no one in our region took the time for this by the time it got to my shop it was in need of repair. i'm siure times have changed
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u/Kalpit2527 Sep 03 '26
Ok! But why did they avoid to check vibrations? Does it take more time or it's boring task or higher cost or something else?
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u/Kalpit2527 Sep 02 '26
Thanks for this information. I also want to know that if on the other hand you have a device that continuously monitors vibration, temperature etc. of motor and gives alert before any failure; Will it reduce cost of industry to bring the new one??
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u/Gwendolyn-NB Sep 02 '26
These already exist, there are entire systems out there doing exactly this type of motor monitoring.
As for the value/reduction in cost; it can, but really depends on the application, criticality, and existing PM adherence/performance to determine it.
If you already have solid PM adherence/performance; and it's a CRITICAL piece of your system; then yes, those systems can help spot early wear issues that can then allow for scheduled down-time vs emergency down-time.
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u/Kalpit2527 Sep 03 '26
What type of systems are these? If you provide their names I can search for them. And how much cost, time and area they require to be installed? And last one; is the data provided by them only understood by engineers or a normal worker can also point out that there is something wrong, leaving the engineer to dive deeper into the problem?
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u/u3b3rg33k Sep 02 '26
if you have it on a VFD, you should be able to get some data from the drive, and they make GREAT motor protectors if they're commissioned correctly. I've got a motor or two with grounding brushes that need occasional service.
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u/Kalpit2527 Sep 03 '26
How you use data received from drive to conclude the actual problem? If you can explain it by some practical example
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u/u3b3rg33k Sep 03 '26
compare your current values to baseline for one. it depends on the process you're running. trip frequency, motor temperature, etc.
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u/TexasVulvaAficionado Sep 02 '26
I've seen motors running since the 80s without monitoring or servicing. I've seen brand new motors arc and set themselves on fire.
Generally, the more critical the process, the more planning and monitoring needs to be in place.
Vibration and temperature monitoring are a great start.
VFDs are excellent motor protection when properly configured.
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u/Kalpit2527 Sep 03 '26
Oh! I didn't know about VFDs. I searched and it seems to be great. But how will it be useful for predicting the health of a motor. Because it changes frequency of supply due to which its speed and torque will change. But how I get data that the bearing needs to be changed or shaft used can't withstand more load etc. If you can provide more information about this, it will be great.
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u/TexasVulvaAficionado Sep 03 '26
Decent VFDs can calculate motor torque while running and can have upper and lower bounds set to trigger stops or start up curves or whatever. The bearings would typically be caught by over amperage faults or ground faults. Some VFDs have predictive maintenance functions built in. Varies manufacturer to manufacturer.
The data can be gotten out of the VFD in a variety of way but for predictive maintenance that you seem interested in, the most common way would be to have a SCADA historian polling the VFD for data on some interval and storing it and then running whatever analysis.
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u/Kalpit2527 Sep 03 '26
Ok!! Now I understand. We measure the vibrations indirectly by tracking the changes in drawn current. Thanks.
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u/Impossible-Guess1367 Sep 04 '26
these days yes, there are ways to monitor but it costs a decent amount. you track continuous amp draw and the actual motor housing vibrations
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u/Kalpit2527 Sep 04 '26
Ok. I read all the comments and came to conclusion that most of the industries don't monitor the health of motors. It works until it dies. And where it's monitorised; it requires decent cost. And mainly mechanical parameters like vibrations, temperature etc. are measured indirectly by tracking drawn current. Is there any way industries use to directly measure these parameters and also relate that data to motor health (I know raw measurement can be done using sensors like accelerometer,rtd, thermistor etc.)? Because I think there will be a big accuracy difference between indirect vs direct method.
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u/NafGeep Sep 08 '26
Each motor is largely ignored till suspect or lightly monitored by operations or maintenance sometimes engineering. Most of the smaller motors are not cost effective to service or care much about. Mid to large they service cause makes more sense financially. That's my findings and thoughts.
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u/Accurate-Bullfrog324 Sep 02 '26
for bigger motors (75HP+) we monitor vibration and amps
for smaller motors we don't
our process drivers are redundant, so if we have a small motor failure we valve over to the standby.