Motor bearing get high temp

The most obvious reason is a bearing failure. Possibly a cracked ball, bent race or galled bearing. To my knowledge grease is intended as a way to keep contaminants out of a bearing, not to reduce friction.

Other possibilities are changes in external loads so that the friction is higher at this particular bearing. Possibly the high temperatures are causing a local hot spot type breakdown of your motor's insulation near this bearing or some additional heat source on the bearing. (Da boss says we can run the steam line here boys.) But I'm just an electrical engineer that knows nothing about your system. You might consider buying a thermal imaging camera (FLIR) to identify the heat source on this bearing if the mechanical disassembly to inspect the bearing is to costly to do without data to support disassembly.

I agree with Redfred that bearing failure is most likely the cause, however grease and any lubricants purpose is not primarily to keep contaminant out (although they will for a limited time depending on the sealing system and the amount of lubricant in the bearing) but mainly to separate the metal surfaces under load and hence they will keep the temperature down. If some kind of damage occurs i.e. due to fatigue or overloading the damage particles will reduce the performance of the lubricant to separate the metallic (rolling/running) surfaces and extra heat is generated. Also an accelleration of the damage will take place from this moment. Water intrusion was also mentioned and this will reduce the viscosity of the grease and hence reduce its ability to separate those metallic surfaces under load etc.....

So, advice that was given to replace the bearing (or the motor if already too late), is prudent.

Dutchy

I'm with Milo. However, I tend to lean more toward vibration. You are going to have to tear it apart to see.

1. LACK OF GREASE.

2. IF RECENTLY GRREASED, PENETRATION OF CONTAMINANTS WITH GREASE.

3.WATER ENTRANCE.

REGARDS

IRSHAD

"1. Lack of grease" (p.s. please stop shouting)

This is also a problem as many bearing seals are suitable to keep contamination out but not neccesarily to keep the grease in.

check quantinty 0f grease , luck of grease, v belt tension more thanrequired, bearing nutlocking too tihgt ,bearing housing wear, check Axial reading,check,bearing seal if its good condition is to Protect dust, water ,or foreing partical.

The problem has probably already been identified but I will add one other possibility.

If a bearing is over-greased it will run at an elevated temperature for a period of time. If it pushes out the excess before heat damage occurs, things will return to normal providing the seals were not damaged by the event.

Too much grease in the bearing could be one reason.

depending on how quickly it went from 60 to 80, you should shake a leg replacing the motor unless you can absorb the down time to replace the bearing. If it went up in a few days, you're headed for smoke and blown circuit breakers, frozen bearing, failure of this and down-line equipment (depending on what the thing pumps). One of my nightmares that wakes me in the dark of night was an E-2 coming into the shop to advise us a motor was running "kind of hot." It always ran hot--ten or twenty degrees higher than the others on similar motors, so we wondered for a moment why he'd never noticed that before and returned to our mid-Atlantic torpor. Next thing I remember was the fire party being called away because the motor was now pumping more smoke and fire than freon and the boatswain's mates whose berthing compartment was around the air conditioning mechanical space became concerned. I could have lost a stripe or two, but for some reason they blamed the E-2 for not communicating the problem effectively. Think of yourself as the E-2 in this story, or the guy who sees the canary fall off his swing with its tongue hanging out and little X's where its eyes used to be. The bird's not looking a little sickly. He looks dead. Something needs to be done quickly. Paint your face blue, set your hair on fire, and get together with the chief of engineering asap.

Here are some more reasons.

1. Bearing fit in housing too tight. No space for bearing expansion.

2. Bearing housing wear, allows bearing outer race to spin within housing.

3. Too much grease or not enough.

4. Mixing greases using depreciates grease lubricating properties.

By the way, being a vertical motor, which bearing is getting hot, the thrust bearing or guide bearing?

I'm leaning toward overgreasing, or an increased load on the bearing. Is it a close coupled pump, or driveshaft? For that matter,is it a pump bearing or motor bearing? You said "sudden" increase in bearing temperature. You didn't mention any increase in noise or vibration, which would definately be present with a failing bearing.

cheers

Rick

There is one possibility that has not been mentioned. If this is a replacement motor it is possible that is a horizontal service motor and not vertical. Check the model ID on the name tag.

Check with your Oiler, the motor is most likely over lubricated and this has caused a bearing failure or the heat is coming from the grease packed in the motor windings..... Contact Noria for motor lubrication instructions..........

Could it be possible the bearing was over greaesd and the seal on either the bearing or the shaft is not compadible with the grease. The seal may be heating other than the actual bearing overheating. Just a possibility?

I suspect one or more of 3 things may have changed.

1)- that the viscosity of the fluid being pumped may have changed.

2)- one of the lines has a restriction

3)- friction on the spinning assembly has increased the work load on the pump resulting in a higher operating temperature! Examples of this would be lack of lubrication causing bearing failure or seal failure causing lubrication to be flushed out of bearing.

The first 2 reasons can be lack of sufficient grease and misalignment of the shaft due to a reason (deflection due to an external effect or wrong assembling after a maintenance etc.)

But probably you already checked those.

It seems to me that the key word is "sudden"; it points to failure of the bearing grease seal.

Sekrob40

In general, there are very few reasons for sudden increase in brg temp...

1. Inadequate quantity of Lubricant...

Excess (If it is grease lubricated, then the temperature will rise up and stay at a level...But if the lubricant escaped through vent holes or seals, then continuous increasing trend until it settles down or brg. seize) first to check...

Lesser (This will result in removal of lubricating qualities of grease due to higher temperature and will lead to metal to metal contact...obviously brg.seize)

2. Any change in the quality of lubricant...(this can happen after maintenance if a wrong lubricant is filled)

3. Any change in the Process (such as, pumping media temperature, load conditions etc.,)

If you specify the arrangement of bearings and which one is increasing, then we can discuss further possibilities.

Motor overheats

1. Dirt blocking ventilation 1. Clean motor

while running openings

2. Unbalanced supply 2. Check for faulty connections. Voltage

voltage on all three lines should be balanced

within 1%. Excessive single phase loads

3. Faulty connection 3. Clean, tighten, or replace

4. High or low voltage 4. Check voltage at motor, should not be

more than 10% above or below rated

5. Grease may be dirty or not the right viscosity.

5. Change grease out or go to a higher viscosity in grease.

A possibility is that the bearing temperature has not increased in temperature but could be due to noise invading your temperature measuring device. Check power supply earthing and isolation.

Regards

Calthorpe

A) Check and make sure the pump spins freely.

B) Has the bearing ever been replaced? If so, is it the proper bearing?

C)Check the motor bearing with a vibration analyzer.

D) Make sure the bearing is properly lubricated.

Stray current going through bearing

Your pump is getting an air bubble inside the pump cavity. If it has a bleeder, try bleeding if not drill and tap and install a pet cock. The bubble is due to air in the system, its just not moving through

DP/////

You stated that your application was a vertical drive pump. Has anyone considered a pump problem? Having a pump problem could apply excessive thrust loading to the motor bearing. Also depending upon the bearing thrust load configuration your motor has, if the pump is not applying enough down thrust to the motor bearing, you could be causing the thrust bearing to not load properly and cause skidding, which would atribute to increased bearing heating. Doing a good failure analysis you need to investigate the complete unit, Motor, couplings, drive shaft and the driven unit. Only a thought to consider.

The 2 most common causes would be Loss of Lubricant or Contaminents in the Bearing.

Other causes could be too much lubricant. Excessive bearing preload for angular contact or deep groove bearings, or loss of preload for angular contact.

I am assuming that the fits on the inner & outer races were proper to begin with & that the RPM is within specification for the bearing type & lubricant. Paul Morgan

Sometimes on older VFD's there are stray currents that conduct through the bearings into the frame of the motor to ground and damage the bearings.

Quite true, this scenario might be difficult to ascertain from visual inspection of the bearing and motor. While I'm not saying that this cannot explain the higher temperature in one bearing, it does make me wonder why only one bearing. I would anticipate a failure mode from stray currents would affect both bearings supporting the rotor, if not more.

Dealing with shaft currents, I have always understood that you would need to insulate only one bearing (journal or housing) in order to stop the possibilities of circulating currents passing through your bearing. Electric current will flow through the path of least resistance. Normally if your motor has only one shaft/coupling it would require only one bearing to be insulated. If you have a double shafted motor then you have 2 separate possibilities for circulating currents to flow, so you would need to insulate both bearings. So where I am coming to, from my understandings, it is very possible for only one bearing to be effected by stray currents.