Bearing Overheat

I'd look for "effects of vibration on bearings" on the net.

There are 14,000,000 articles written by bearing "people".

Asking the forum for single anecdotal, personal experiences of causes will not yield good results.

Here's one: Sound and Vibration in Rolling Bearings.pdf

YOU are doing the analysis and I have provided you with a source you requested. Good luck.

Now, go to work.

There can be many causes...

http://www.applied.com/site.cfm/CausesofBearingFailure.cfm

I'd add mixing grease types together into that...be consistent, don't mix

Yes, vibration can cause or contribute to overheating. It imparts kinetic energy to the bearing, which converts to and dissipates as heat.

I find it more helpful if you also tell us the type of bearing....Plain, ball, roller and and and.....

Though I personally feel that most bearings don't like vibration much, though I bet that there are bearings around that can handle vibration better than others....though I am far from being an expert.....

If I was you, I would ask a bearing specialist company for help and advice.

Also, posting Anon is VERY unfriendly.........and unlikely to help you much either.....

Dear Anon, Yours is an astute question, in my opinion, as we often speak of bearing failure due to (misalignment, unbalance, etc.) vibration in the rotating component supported by the bearing component(s). The failure mode 'vibration' does cause overheated bearings; however, the relationship between 'vibration' and bearing temp is nonlinear. Moreover, said relationship will differ depending on vibration frequency(s). With that said, a high bearing temp does not imply 'excessive' vibration above 'normal limits' unless one defines 'limits' by vibration frequency. For example, I've seen 2xRPM frequency vibration (typical of misaligned shaft components) cause heating at a slower rate over time than, say, multiple frequency, vibration. Vibration causes heat due to increased friction energy as 'tangent load forces' induce diminished 'tangent lube-gap' between rotating bearing surfaces. Should metal-to-metal contact then occur within the rotating bearing assembly, frictional forces lead to component deformation, increased friction, and more heat.

I thank you all for the replies,

Simply, my real main question was, how can vibration become the cause of overheating?

In an FMEA, by stating that overheating is caused by vibration, you are also implying that their relation is that of a sequential event, and not a parallel one. Which means that one cannot happen before the other and both cannot be happening at the same time.

If one were to try and scratch a window glass with a knife, aren't noise, vibration and heat be generated, all at the same time, as a product of the friction??

If you were to say that "misalignment causes vibration" or "unbalance is one of the failure cause of vibration", i don't really feel the need to question it. But how can one become so sure in saying that vibration is causing overheating and implying that they are not a parallel event that are actually caused by the same cause?

Regards,

That's where the concept of "causation" comes in to play, and that's why an SME needs to be consulted to verify your assumptions. Implication and inference are fine as you gather your data, but your fault tree has to accommodate all the different conditions, regardless of their source or their outcome.

For example, your conditional "...overheating is caused by vibration..." is not the only event that must be considered, you also need to examine the validity of "...vibration leads to overheating...". In fact you may discover that both events are independent of each other, but the sequence in which they occur is important.

For example, a pump may develop vibration because a piece of the impeller broke away and destroyed the balance, then the ensuing shaft vibration causes a normally smooth running bearing to start vibrating and the additional friction causes the bearing to overheat. Neither did the vibration cause the overheating, nor did the overheating cause the vibration, they were both the result of an independent event, a classic "chicken and egg" problem.

That's where an SME can help you see the interaction of all the parts of the puzzle and how they play together, something that a generic project manager is incapable of on his/her own.

We had a case in our plant, it was after regreasing of the bearing (roller bearing), when the equipment (crusher) started running, the bearing temperature (bearing #4) increases to 90 degrees celcius. I causes panic to the operation staff. We held a meeting trying to find the cause of the problem... but then just after two days of the equipment running, the temperature went back to normal around 70 degrees celcius on its own without maintenance team having to do anything.

The maintenance team said it was a normal thing and that it happens frequently like that, after greasing, the temperature went high for two days and then it goes down on its own...

Is it really normal something like this to happen? Why is it happening like this?

Overgreasing until the excess is expelled. There is such a thing as "too much of a good thing".

Please explain, how can you verify that is not undergreasing, which also causes overheating?

An undergreased bearing starts out hot and usually gets hotter as what little grease there is runs out/breaks down as the temperature continuous to increase; i.e., the lubricant wedge is too small/nonexistent for the load being imposed.

An overgreased bearing has the extra drag of the excess lubricant throughout the bearing contact surface, and this extra drag will cause friction which results in a rise in temperature until the grease starts to run out.

The type of bearing plays a role in the retention of grease. From this article:

"...since the ball-and-cage assembly of this arrangement does not have to force its way through a solid fill of grease, bearing heating is kept to a minimum. In fact, it was observed that a maximum temperature rise of only 20° F occurred 20 minutes after the grease reservoir was filled. It returned to 5° F rise two hours later. In contrast, the double-shield arrangement caused a temperature rise of more than 100° F (at 90° F ambient temperature the resulting temperature was 190° F) and maintained this 100° F rise for more than a week..."

Sine you did not provide a time frame for your observations I suggest that you talk to your bearing supplier/expert to see if you are really having a problem, or just perceiving one due to lack of understanding/information.

It's an S.K.F roller bearing. Time frame: operated first time around 2 years ago..

Here's 1380 pages of SKF Roller Bearings including some really good info on lubrication. It's time to RTFM (Read The Fine Manual), the free consulting portion of your 20 question session has ended.

Just browsing through and came across this.

Vibration is an effect of a failure in some part of the system whether it is misalignment, bearing faults, poor lubrication, etc...

I could rant, but choose not to