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We have a problem of High Bearing Temperature of Motor Bearings immediately after greasing and this lasts sometimes for 2 to 3 Days after greasing. In Motors where we have high bearing temperature protection systems in place we have to sometimes By pass the Trip to avoid tripping of the Motor on account of this. Could someone guide me on how to overcome this problem.
Already we are taking sufficient care on the amount of grease that is pumped in and also on the greasing intervals so as to avoid over greasing.
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Hi Ramanathan,

I guess that you experienced burning your motors because of over lubrication. You might also using wrong grease for that motor. That is the common problem, over or under lubrication using the manual method. If you wish to eliminate that problem pls contact Memolub ( in your area or give me the complete specification of bearing, rpm, normal temp, etc. also grease you use.

What is your motor greasing procedure?

It sounds like a common over greasing situation. To much grease will cause your bearing temps to rise. My suggestion is to use a ultrasonic monitor when greasing your bearings. Many of my customers use the PdMa Corps grease gun attachment and are happy with how it works. There are numerous companies on the market that make this type of monitor. You might try doing a little searching in your local area and see if there is a local distributor of one.
Ramanathan, As you state that your are monitoring your procedures to prevent "Overgreasing", lets assume there is something else going on here. Can you give us specifications on the motors (model, S/N, speed, etc.)and what type and mfg of grease you are currently useing? And if you would, what are the motors doing?

Hi Ramanathan,
if you are confident that the initial greasing quantity is correct, then the next probable cause would be selection of grease what is the speed , what grease was recommended and what is the present grease used. and pl check the base oil viscosity of the grease being used.
Initial temperature raise is considered to be normal as the oil thats held in the soap Matrix of the grease needs temperature to bleed and this oil will then start providing a lubricating film which will reduce the temperature. the temperature rise till this is achieved is considered OK. But if it is alarmingly high then the motor needs to be stoped and allow the grease to cool down and again start. sounds primitive but has worked well in many places.
If you are by passing safety trip then you have to constantly moniter the bearing temperature and avoid running at very high temp, and this may cause bearing damages.
Collins David
I think it could be a wrong grease type used.

If you are sure that you have added the correct amount of grease, and the greasing invervals are the correct, other point you should check is the remotion of the old grease, when you add new grease.

I recommend the following steps.
1- Check the type of grease. Don't use grease for high temperatures if the manual of the motor doesn't recommend it.
2- Check de procedure of greasing, for the determine the best way to remove the old grease.
3- Consider any type of automation of the greasing, or change the lubrication for oil mist, if this is permited by the motor design.
There is one other possible problem. How long is the grease tube on the motor. You could be pumping "hard grease" into your bearing. If you have a grease tube or line going into the bearing, you may be pumpin in some old grease that is hard into your bearing. By introducing a foreign object into the bearing, you are damaging your bearings and causing a loss in bearing clearance, which will increase the temp. This may continue until the system works itself to a steady state.
Hi Ramanathan
The above info is good advice for greasing,
we have seen several large electric motor failures where the "normal" plant grease was being applied.
The bearings type that causes the failure is always the cylindrical roller and the grease is always a heavily tackified normal plant grease.
When we root caused the failure it appears the application of a heavily tackified grease to a large cylindrical roller bearing can sometimes cause the bearing rollers to roll the grease along in front of the rollers as a "bow wave" forcing the base oil out of the grease increasing the grease hardness up 1 or 2 NLGI grades. This causes the rollers to hang in the cage, VA indicates under lubrication, more grease is applied compounding the difficulty,
If this scenario occurs and you apply more grease and the problem worsens and the combination of grease type and bearing above are in use it can be impossible to prevent the failure,
If suspected, to remedy load the grease gun with the correct viscosity base oil gear or hydraulic lubricant and by applying carefully monitoring the compacted grease can be loosened and flushed out of the bearing and then the correct grease can be reapplied and the bearing monitored until it resettles back to normal wear.
We have not seen this with spherical rollers or ball bearing as the round shape tends to divide the grease ether side of the track where as the cylindrical roller tends to push the grease in front if a heavily tackified grease is applied. The correct grease is always an NLGI 1-1.5 and has a soft buttery consistency.
This scenario may be why you getting the temp increase.

Regards Rob S
We had the same problem with a pump bearing.Afetr investigation it was found that quantity of grease was high.As soon as we reduced the quantity bearing temperature reduced significantly.
Also you should follow the manufacturer recommendation for the right quantity and right type of grease.Before greasing yuo should clean the bearing off the previous grease.You may also check alignment.Dirty grease may cause also the same problem.
Approximately 60% of all bearing failures are due to over lubrication. Electric motors are one of the applications that "show" any kind of problems first. I have been supplying automated lubrication systems for over 20 years and these types of systems can cure almost all these types of issues because they supply a very small amount ( in the area of 0.0025 cubic inches per cycle) often, and I still do not connect electric motors because they can be very sensitive to excessive amounts of lube.

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