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54 comments
Anonymous Poster #1

Sudden Bearing Failure

01/01/2012 5:31 PM

Hello guys,

I need your opinion on one of our catastrophic bearing failure. We had tapered roller bearing installed on one of the vertical agitator. Condition Monitoring didn't report any issue when conducted survey 10 days ago however, this morning, it seized up suddenly. We found strong grease burnt up smell when opened but unable to determine exact failure mode. Locking ring was found extremely tight, I looked up all other parameters, everything was fine and nothing went wrong which could have instigated that failure. Any comments, experiences,??? Greasing was done properly, accordingly to lubrication guy however, I am still trying to find out more.

Thanks

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#1

Re: Sudden Bearing Failure

01/01/2012 5:56 PM

Need a pic of the agitator and the bearing.
Seen a lot of bearing failures in stirers due to bad design.
Del

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Anonymous Poster #1
#2
In reply to #1

Re: Sudden Bearing Failure

01/01/2012 6:49 PM
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Anonymous Poster #1
#5
In reply to #2

Re: Sudden Bearing Failure

01/01/2012 6:51 PM
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#6
In reply to #2

Re: Sudden Bearing Failure

01/01/2012 6:51 PM

Clean it off, degrease it...

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#15
In reply to #2

Re: Sudden Bearing Failure

01/03/2012 12:39 AM

Clean off all the grease and provide clear photos of the raceways, damaged rollers, undamaged rollers and their debris including the small bits.

There will be a story in there.

Meanwhile find out exactly how this was lubricated and how frequently it was really lubricated during its service life.

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#3

Re: Sudden Bearing Failure

01/01/2012 6:49 PM

1st. Was the seal blown out the last time the bearing was greased?

2nd. Was the shaft turning while being greased or was it idle and only one side of the bearing being filled with grease?

3rd. Was the Zerk and tip of the grease gun cleaned to avoid "injecting" foreign material into the bearing?

4th. Was the grease confirmed as the same type and rating as the bearing was originally shipped?

5th. Do you use a monitoring system that takes online (running at normal speeds and temperature's) bearing temperature's? If not you need a portable gun for weekly/monthly record taking. This will give you warning when a bearing is beginning the failure process.

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#4

Re: Sudden Bearing Failure

01/01/2012 6:50 PM

Which bearing?( diagram ) What is being processed, exactly(chemical composition)? Do you have an ultrasonic detector? Do you have the bearing specs? What's the model and Brand of the mixer? What is the weight of the load being mixed ? Is the mixer well grounded? I have heard of chemical reaction causing bearing failure, have you recently changed product? Do you have life expectancy calc on bearing from manufacturer? Have you run radial load calc on bearing?

Bearing damage analysis...

http://www.timken.com/en-us/products/maintdiag/Documents/6347.pdf

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#7

Re: Sudden Bearing Failure

01/01/2012 8:39 PM

"vertical agitator" - interesting problem you have there.

It might be useful for these folks if you can get them a diagram of the agitator, its direction of motion relative to the bearing, frequency of motion, mass, dimensions and range of motion. IE; How big and how variable are the loads on the bearing?

I assume you found no evidence of lubricant leaking?

What kind of temperature change does the bearing and race go through?

You refer to a "locking ring." Is this locking ring also the component that seals the lubricant in the bearing housing?

Also; depending on the coefficient of thermal expansion, the forces and clearances in the assembly is going to change during operation.

The bottom line? --- Call the manufacturer - not the supplier. It is understandable that the manufacturer will want to protect their interests; but if they should want to know if there is a fault in design and are probably the most expert in finding a solution to your problem.

If it does end up being the guy with the grease gun that is to blame; make sure his level of training was where it needed to be. Often times human factor failures involve more than just the guy doing the work. Was he set up for success or left to flap in the wind?

Gavilan

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#8

Re: Sudden Bearing Failure

01/02/2012 9:55 AM

I find something very similar looking in Electro Motive generator bearings from time to time when;

1- improper grease is used and/or mixed.

2- over-greasing has taken place

This is only an example as we all know, but for instance above are typical "as found" conditions and also a cap with the proper amount of the correct grease applied. In the instance of the Electromotive AB-20-6 Generator Bearing (spherical/roller), the proper amounts of the proper grease (in this case ESSO UNIREX 2) are EXACTLY;

Cover 482 grams

Bearing 368.6 grams

Cap 283.5 grams

Regardless of what your "lubrication guy" spouts off, you should look further into the manufacturers specified lubrication procedures.

Tim

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#19
In reply to #8

Re: Sudden Bearing Failure

01/03/2012 5:18 AM

GA.

Exactly what I was going to mention "over greasing". You got there first I believe (apologies to anyone else I may have overlooked!)

Many people do not realise that over-greasing is FAR worse than under-greasing and causes a dramatic temperature rise and possible burnt grease smell, leading to bearing failure.

In the early 60's (I think or earlier, but before I joined in '63), the RN realised this and blocked off all grease nipples on most motors (all that I remember about anyway!) and reduced bearing failures dramatically.....to an almost unimportant level.

A properly packed with grease new bearing MUST have an air space to stop the grease continually "working!" We used to fill the grease holder/bearing cover plate (?) full and then we removed about a third. It worked for us, but err on the side of an air hole of between 33 and 50%.

My tip, remove all grease nipples and securely plug the holes....Train your Guys with proper bearing replacement and lubrication procedures.....and remember that cleanliness is next to Godliness!!!

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Anonymous Poster #2
#20
In reply to #19

Re: Sudden Bearing Failure

01/03/2012 5:33 AM

what stops the bearing from pushing the grease into the air gap and running dry ?

does a change to a low grease level inside the rolling contact area cause heat rise > then melt some grease and gains lubrication that way ?

thanks for views

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Anonymous Poster #4
#21
In reply to #20

Re: Sudden Bearing Failure

01/03/2012 5:54 AM

You may never understand how this works........!!!

BUT!!

You should read all the posts through again, it may improve your understanding.

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Anonymous Poster #2
#22
In reply to #21

Re: Sudden Bearing Failure

01/03/2012 6:09 AM

wow . that makes you sound immaculately close to the international specification for a True W@nker

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#27
In reply to #22

Re: Sudden Bearing Failure

01/03/2012 9:10 AM

Typically the bearing is 100% packed with the proper type of grease, now as the grease works some will migrate. Naturally it needs somewhere to go, for this see Andy's comments. Its very close to what we do when our scale is not available.

Some equipment manufacturers specify a number of "shots" to be added. This you need to be careful with these days as there are many different grease guns available and one "shot" amount can differ greatly.

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#28
In reply to #22

Re: Sudden Bearing Failure

01/03/2012 9:26 AM

Someone who uses such words on CR4 has usually heard them addressed to himself very often already! I am personally of the opinion, even though its not my fight here in any way, that such name calling demonstrates a diminished or childish mentality....

Anonymity here is a similar demonstration too!!

Furthermore the spelling you used is incorrect (you having only probably heard it, therefore completely understandable!!), so I looked it up for you in an online dictionary, to make sure I got it right too.

(Interestingly its apparently a "Brits" only word, the CR4 spelling checker did not know it either):-

wanker
Pronunciation: /ˈwaŋkə/
noun
British vulgar slang

a contemptible person (used as a generalized term of abuse).

It could also be used for anyone reading a blog with really good information already in it, but the person concerned cannot seemingly understand any of the info supplied!! Thanks for reminding us of it!

I hope this assists you further with the future use of that word! as now you can even spell it properly!!!

Good day to you......

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#29
In reply to #28

Re: Sudden Bearing Failure

01/03/2012 9:37 AM

Amen...

Have a good day Andy, now that you got that off your chest.

Tim

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#37
In reply to #29

Re: Sudden Bearing Failure

01/03/2012 2:38 PM
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#41
In reply to #8

Re: Sudden Bearing Failure

01/03/2012 5:01 PM

Not sure if Tim is right, I'm the Electrician, but GA from me if he's keeping EMD Generators and D79's going he knows what he's talking about with greasing, worse that GE752's with failure because of improper greasing, all grease fittings removed decades ago. What was that on Tim: an old DC-DC Rig with a room full of Generators? I have heard they hardly use D79's in TD's because of the high failure in the vertical ordination.

One vote against a GA, what is this the Iowa Caucus? Ron all we Texans love you regardless but stay off CR4

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#53
In reply to #41

Re: Sudden Bearing Failure

01/05/2012 5:49 PM

752's are preferred vertical or horizontal in drilling applications. That was an AB-20-6 generator cap in the photos (2200+/- KW).

Roughly 1000 hours service with that black gunk and already .007bearing clearance!

"Lube guys" and un knowing electricians keep me in buisness...

I always leave the rigs with the proper Maintenance Instructions in hand, but they rarely listen to or believe them...

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#42
In reply to #8

Re: Sudden Bearing Failure

01/03/2012 5:04 PM

2X post sorry,

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#9

Re: Sudden Bearing Failure

01/02/2012 10:52 AM

Was it a new installation, or had it or similar agitators been running for some time and found to be reliable until this problem?

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#10

Re: Sudden Bearing Failure

01/02/2012 8:34 PM

Looking at the picture, I don't see a locking washer on the locking ring. This tabbed washer is bent into a keyway to keep the locking ring in place to keep the proper pre-load on the bearing. Maybe the locking ring was moved by shaft rotation and over tightened the bearing. Tapered bearings are real fussy about that.

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#11

Re: Sudden Bearing Failure

01/02/2012 11:03 PM

has the bearing preload been affected by any changes ?

if there is axial expansion in the shaft due to heat , the bearing might tighten up

what controls alignment and preload ?

was that the top bearing or bottom one ?

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#12

Re: Sudden Bearing Failure

01/02/2012 11:35 PM

First of all let me tell you one thing that, MMS will not give you any prior indication of failure because you have taper roller bearing; basically a antifriction bearing.

If you see the API 670 (for machinary protection) it does not cover antifriction bearing because you can not measure oil film temperature here, which you can in case or hydrodynamic bearing. At the most you can measure bearing surface temperature. (Refer API 610 10th or 11th edition where it is mentiioned that bearing surface temperature shall not exceed 93°C or something. this is just for your referance).

so try & find out which temperature your probe is measuring?

now coming back to your problem. It could be due to following;

1. Use of non standard (mixed grade or lower grade) grease.

2. Quantity of grease (over greased or low greased)

Sometime when we say bearing is properly greased it could be over greased. The over-packing and over-greasing of bearings accounts for more failures than any other factor. Excess grease in a bearing cavity increases internal friction, which in turn raises the bearing temperature above the dropping point of the grease. This causes oil separation and eventually lack of lubrication. From your Pics it seems that bearing is over greased & also you stated that you smell grease burning smell.

I will suggest you to check

1) Grease type (whether it is recommended grease or not)

2) Check whether proper amount of thicker is added in that

3) Quantity of grease

4) along with 1 to 3 checkes please check agitator shaft is properly aligned or not

5) bearing lubricant seal if failed or not.

I think your problem is more pointing towards temperature rise, type of grease & quantity of grease.

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Anonymous Poster #2
#17
In reply to #12

Re: Sudden Bearing Failure

01/03/2012 1:49 AM

sorry for diverging away from the OP but can you give a bit more information , or point me to links for information about bearing failure from overgreasing , and how to assess calculation of correct grease levels.

horizontal shaft with cylindrical roller and sphericals is my field of application

thanks

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#13

Re: Sudden Bearing Failure

01/02/2012 11:49 PM

Not my area of expertise, but engineer hubby says "too much pre-load".

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#14

Re: Sudden Bearing Failure

01/03/2012 12:21 AM

What is the grease that was installed?

Do you have a bearing # or part #? Paul

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#16

Re: Sudden Bearing Failure

01/03/2012 12:43 AM

Was force applied THROUGH the bearing to install it?

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Anonymous Poster #3
#18

Re: Sudden Bearing Failure

01/03/2012 5:18 AM

Dear AP#1:

There is a lot you have not told us. Who is "I"? Who is "we"? Who did the installation of the tapered roller bearing? I am not asking you to reveal your identity, but to tell us who these people are relative to each other. "You" do not seem to have engineering expertise, at least with regard to bearings, but you are interested, as if in management. Was it an outside vendor who installed the bearing, or a different department of the same company? It sounds like some people are trying to cover their asses and you are trying to uncover the mess. Can you find someone available who can deal with the technical analysis for "you" or "we", so that you can do "your" thing? Do "you" have a maintenance department, or are you the maintenance department? When "we" could not determine "exact failure mode", was that your responsibility, or are you trying to find out whose responsibility it was? This is not a negative criticism of your post, but it is an explanation of why it is hard to provide the "more" that you seem to want us to provide. The view of this problem is highly dependent on one's viewpoint. I feel anonymous myself from this point

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#23

Re: Sudden Bearing Failure

01/03/2012 7:15 AM

Most everyone has hit on one or more items that could cause this to happen. I would suggest that you contact your bearing supplier and or the bearing manufacture and find the cause. I like everyone else, could speculate as to the cause but, with out having the bearing in my hand I would not do that. I can not see what your seeing.

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#24

Re: Sudden Bearing Failure

01/03/2012 7:20 AM

What information is provided to you for condition monitoring? I am not sure about the agitation application, but you may want to look into the service grade (tolerance) of the bearing.

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#25

Re: Sudden Bearing Failure

01/03/2012 8:14 AM

the evidence is always there. Describe the details of the failure. What did YOU see on arrival or was this reported to you. What are the operating times of the unit. By aqgitator describe it's support structure, size etc. Do you have any pictures. On thing we know as, the unit was stopped the bearing did not go to catastropic limits. Instead there was a time quotient. Describe the greasing system used. Is there a pressure relief on the system. When was it recently greased.

All the best ... WyEtte

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#26

Re: Sudden Bearing Failure

01/03/2012 8:18 AM

Hi (Anonymous): I consider the information provided it´s not sufficient to help you quickly. It would be useful to know additional data like: bearing running hours, bearing & shaft arrangement, bearing model, kind of grease, shaft RPM´s, kind of instrumentation used to monitor the condition, is it the first time this configuration fail and in special it would be better if you attach a picture of the bearing damaged. I like to find out this kind of failures, so if you can add more information we can work together.

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#30

Re: Sudden Bearing Failure

01/03/2012 9:55 AM

I have read posters #1 to #26 and almost all are right on. My advise is to invest in an ultrasound detection device such as UE or SDT with the grease attachment , take the training and grease your bearings according to need it may be one pump or three but more than likely 1/3 of a pump. 40 years in maintenance and most bearing problems I solved by cleaning out and greasing according to MFG. instructions. Never over grease unless you want maintenance overtime. If you do make the jump to Ultra Sound Detection start a program of trending your equipment but only if you wish to save on down time and maintenance expenses.

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#31

Re: Sudden Bearing Failure

01/03/2012 11:22 AM

Any chances of contamination of grease? Can the agitator get overloaded? What is the agitator handling?

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#32

Re: Sudden Bearing Failure

01/03/2012 11:32 AM

Andy and Tim are correct with the type and amount of lube. If condition monitoring fail to show up any anomalies you may have had particle contamination form above (seal failure) as verticals are bad about that and hard to detect on autopsies. We use Ultrasonics for lube and monitoring but even that is difficult on slow moving bearings.

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#33

Re: Sudden Bearing Failure

01/03/2012 12:38 PM

Too much grease causing overheating.

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#34
In reply to #33

Re: Sudden Bearing Failure

01/03/2012 12:41 PM

And so it seems...

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#35

Re: Sudden Bearing Failure

01/03/2012 12:46 PM

"Locking ring was found extremely tight"

The lock ring should not be extremely tight. Too much thrust between cup and cone will cause them to over heat. Either the lock ring was set too tight during the replacement or the keeper that holds the lock ring fast was not set properly and the lock ring tighten up.

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#36
In reply to #35

Re: Sudden Bearing Failure

01/03/2012 1:05 PM

ozzb,

Possibly, but how can you be sure with the information given?

Either way, other posters have asked for some things that would make a fair analysis a bit easier;

A- Drawing

B- Detailed photos of the parts after dis-assembly and cleaning

C- Specific equipment

D- Specific application

I wouldnt compleatly dis-agree with you, but it only seems that this is a guess at this time with the information given isnt it?

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#48
In reply to #36

Re: Sudden Bearing Failure

01/04/2012 7:54 AM

You are right it is a little hard to diagnose something with out hand on inspection.

Years of experience the lock ring should not be extremely tight. The thrust force placed on this type bearing by the lock ring can seize the bearing up. Have seen the results of over tighten lock rings or where they have come loose and tighten on the own. Though I can't smell the burnt grease. The picture they look similar to the ones I've taken a part to repair.

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#38
In reply to #35

Re: Sudden Bearing Failure

01/03/2012 2:41 PM

"Locking ring was found extremely tight"

That might even be part of the effect of overheating with too much grease......possibly?

Just a possible thought.....

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#39
In reply to #38

Re: Sudden Bearing Failure

01/03/2012 2:52 PM

Andy,

Yea I was going to mention metal relocation during failure and its affects on the assembly (including the locking ring) but this thread is full of people with enough experience to realize that.

As a matter of fact I am certain oz is as well.

Its all purely speculation until a proper failure analysis is done anyway.

Actually the only thing we all know for sure is that the equipment got hot and it now stinks like burnt grease

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#40
In reply to #39

Re: Sudden Bearing Failure

01/03/2012 3:04 PM

I think Andy Germany filled it with grinding compound.

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#49
In reply to #40

Re: Sudden Bearing Failure

01/04/2012 9:17 AM

....of course, that's how I run-in my bearings quickly!!!...they also run-out quickly too......

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#43

Re: Sudden Bearing Failure

01/03/2012 7:53 PM

I have just skimmed this and to date it seems to about greasing and wanking, so apologies if someone has covered the following;

Agitator infers a reversing motion, as Del commented, #1, this may be design issue.

Rolling bearings do not like oscillating action, particularly where a rolling element does not complete a full revolution of its diameter and/or roll past the seat of the adjacent roller.

What you will get is scalloping wear and oval elements.

And shortly afterward; 'sudden catastrophic failure".

Symptomatic is de-lamination (flaking) of the ring surfaces - which 'tightens' the pre-load when migration occurs.

Bearings selected for such duty should have more numerous, smaller diameter rolling elements."Full complement" needle rollers in CV joints are a good example of 'oscillating design approach'.

An oscillating rolling bearing is also near impossible to adjust for wear, as the pre-load will vary throughout the arc.

The maintenance schedule is "replace in x hrs" - not 'keep on greasing'.

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#44
In reply to #43

Re: Sudden Bearing Failure

01/03/2012 8:10 PM

re your first paragraph , it should be noted that the standard recommends a low irritant white petroleum jelly used while wanking due to the results of previous testing with synthetic grease leading to catastrophic failures of the wear elements.

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#45
In reply to #44

Re: Sudden Bearing Failure

01/03/2012 8:31 PM

In your case, see the "food grade" section.

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#46

Re: Sudden Bearing Failure

01/04/2012 2:14 AM

Who could have guessed that bearing failure could be so entertaining - even informative -- I wonder what is happening to that bearing now...

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#47
In reply to #46

Re: Sudden Bearing Failure

01/04/2012 2:24 AM

It is booked to go on tour with Dalai lama and Eckhart Tolle .

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#50

Re: Sudden Bearing Failure

01/04/2012 9:41 AM

This has nothing to do with your vertical roller bearing failure, however is a good lesson in Ultrasonic condition monitoring. I found it 4 months after this "new motor" was put in service. It is fine particle intrusion (alunina) through the seal. The MFG. said this was "False Burnelling". It was not a run to failure as it was picked up easily with a UE Systems 9000 gun on 30KHz. The grease looked good until you rubbed it between your fingers.

Autopsy- BC24 /151 System Belt Conveyor

10 HP Toshiba, 215T frame, 1750 RPM, Premium Efficiency, Mill and Chemical Duty

In service 5 months, PdG scheduled change-out, UE anomaly report Level III

Manufactured 6/2010, Return for warranty exchange (FE)

As Found:

· Clean, Sealed J-box, Meggers 539GΩ, looks like it just came off the shelf.

· Shaft turns smooth but doesn't roll freely (Characteristic of sealed bearings)

Autopsy Findings:

· Sealed bearings, 6308 TOYO brand

· Outboard bearing cavity has some ore intrusion from heavy ore dust environment and cooling fan proximity. Drive end bearing tight, clean, like new.

· Outboard bearing loose. Tight fit in housing and on shaft.

· Windings clean no dust or grease.

Root Cause: False burnelling may be indicated by the uniform spacing and elliptical radial pattern. Extreme case, but evidence from references points that direction. No exact case match found. Requested further investigation from supplier upon return.

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#51

Re: Sudden Bearing Failure

01/05/2012 1:34 PM

Is 3rd harmonic current thru bearing out of question?

This is only thinkable if there is a VFD, motor coupling is not conducting, shafts not earthed etc.

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#52
In reply to #51

Re: Sudden Bearing Failure

01/05/2012 5:11 PM

actually welded repairs carried out to machinery can cause bearing damage if simple rules are not followed too

earth clamp not to be fitted to one part of a machine while weld repairs being done to another , or full welding current can pass through a bearing .

excavator slew bearings or drive motors , rock saw drive motors , bucket wheel / conveyor chain drives , concrete agitator drums .....

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#54

Re: Sudden Bearing Failure

04/25/2012 6:40 AM

In the 80's I encountered many problems with counterfit bearings from the NTN Toyo brand, Switched to mayor german brands like SKF. The production loss was far greater then tiny profit on those toyo bearings. Where ever we used pregreased double sealed 2RS bearings. Mounting new bearings is crucial, just try to avoid hammering them on with a sledge hammer, we heated them up with induction and slipped them on.

Alignment of drives is always a problem. Very good tools available since 20 years to get it easier and done. And at times take in account you need greater roller clearance, the C3 type.....

Sure don't overgrease. But lubrication seldom is root cause unless dry or packed stiff.

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