Sam,

An excellent distinction between PdM and VA. PdM often leads to VA but they are not the same.

Bill F.,

If you really have a question about how the TA wall chart was developed why don't you ask someone at TA? They're really not that hard to find and I'm surprised that, given your level of concern, you haven't already done it.

I don't think that I said I was concerned about the wall chart. People keep talking about a codified structure for bearing failure. From where does it come?

Danny and Bill K write as if it is from TA. Is this so?

Okay Bill, you are concerned about the CONTENTS of the wall chart. There have been two sources cited already, ask them.

It's been around a long time. From discussions going back some twenty-five years it was a topic and talked about, but has it ever been formally adopted? I think not globably but apparently TA adopted it. Anything wrong with that; why should there be. I think it has served some in learning or helped the novice and possibly to a large degree. Regardless, I think it did contribute or has contributed.

I don't think failure modes are quite so simple nor do all fit a single power curve that represents a failure curve.

Has a paper been presented to a 'governing body' that could put ISO specs to it - I think not.

The stages of failure for rolling element bearings has been mentioned a few times in various posts to this forum. This may seem like fact to some. It looks like a theory (of categorization) to me. What one would like is for it to be a scientific theory that has been tested and can continue to be tested.

Can a un-founded theory cause harm? Well, I believe a witch will float when bound and tossed in a river. That would be a theory, but it would be difficult to test today. Although, I believe it has done some harm in the past.

As a theory, the stages of failure, does simplify the understanding of failure. Is this theory based on logical deduction from data and science, which can be repeated, or did someone just write it down as a theory stated as a fact? All I have asked is some help to source this.

One might ask themselves why it is a part of their belief system. To be able to simply categorize failures does lead to a simpler understanding from which one might develop technologies to help diagnose failures better than pervious technologies. If anyone on the board had asked this before, I suppose we would have an answer as to the origin of this theory on failures.

Merely being in existence for a long time does not make a theory a scientific theory, and in not way does it make it fact. The lack of support evidence gives me no reason to believe this theory, not that I have any contrary theories to offer or defend - I am not ready to accept such a theory on blind faith.

This message has been edited. Last edited by: William_C._Foiles,

Bill - there you go again, stirring up trouble. Just because the belief system system ignores the mechanics of bearing failure is no reason not to believe in it, is it?

73, Duncan

quote:

All I have asked is some help to source this.

Bill,
A couple of people have given you a name to call and talk to. Jim Berry. I am sure others can call for you but the bottom line is you know what questions you want answered. Asking third hand is not very efficient.

Jim may just tell you this is how they divided up the failures so a novice can understand it. He may tell you they spend 75 years at MIT researching it. But as I said you have the questions you want answers to.

Call and ask,

(From their website)

Technical Associates Of Charlotte
704-333-9011

Aubrey

quote:

A couple of people have given you a name to call and talk to

As stated previously, this is not the way theories gain acceptance. Some science is protected for national security reasons. I don't suppose this is.

quote:

Jim may just tell you this is how they divided up the failures so a novice can understand it.

Similar sentiments have been mentioned previously. If this is just a fairy tale, I can accept that. Just be up front with it.

If the good folks at MIT spend 7.5 years researching it, there would be numerous papers in the open literature. If they spend 0.75 man years there would be a couple of papers out there or on the way, assuming they found anything. The way these things work, is one university spends much time and resources in a particular area they are often joined by other universities, unless there are barriers such as money or national security. One university throws off graduates that go to other universities and continue (often) the research they did as a student; it helps get tenure. The former student should have a few papers left in their dissertation, which just happens to be on what they worked.

There appears to be no support for this 'theory,' other than emotional.

I don't think they (TA) state it as fact. But then again I don't have that info.

The first time I came in contact with the chart was in 1998 at a chemical plant where I was working on their problem equipment that no one could solve over the years. They specifically told me that they did not want me involved in their PdM vibrtion route program. After I was there six months (I enjoyed a lot of success and they kept giving me more problem areas) I was standing in the PdM guys office. He had a TA chart on the wall and I studied it for some time. From there I found a number of things I disagreed with and pointed those out to the PdM guy when he returned. He was level 3 certified + had an alignment cert too. Worst PdM program I ever saw though and was using Entek w/full blown package. He was poor at best.

This is my opinion of the chart: it is an item for sale to generate revenue.

In addition: it may be a good thing for the novice but if one were to take it as an authority it could do harm (unsure to any degree).

I also think for one to become good in this craft it will require a lot of work and dedication. Taking courses are good but don't expect to go to a class for a week and become qualified or three coursed and be qualified. I can easily see were a cert 1 or a no cert may be much better than a cert or level 3 VA guy/gal. I've certainly seen some pitiful level 3 cert guys claiming to be vibration guys.

Get all the education you can; can all you get. Then performing VA for 10 years may make you a master at the craft. It took me longer. Still with respect to where I am, I believe I can honestly say that I have a way to go to catch up with Bill Foiles. Another of my opinions is the acedemics may reside high in an individual and he/she may not achieve without the practicle field experience.

I hope my rambling hasn't generated any confusion.

Dan Ambre used to work for TA. He uses the four levels of failure in his Vibration Fault Guide. He has a much better breakdown of the progression (my opinion).

I have TA's Advanced Vibration Diagnostic and Reduction Techniques that includes part of their diagnostic chart. I haven't obtained much help from this manual. Maybe in conjuction with a class it would be better.

I also have Dan Ambre's wall chart. Dan's chart doesn't have the four stages of failure, but I have found good help using it.

quote:

Merely being in existence for a long time does not make a theory a scientific theory, and in no way does it make it fact.

I agree with Bill on this. Much of what is often accepted as "factual" in vibration analysis is simply based on experience, and is mostly anecdotal, not empirical.

What is stated by those "who should know" is often just accepted, with very little verification. There is a great deal that we could all learn by a little careful, low-level research, done on our own. But no one takes the time, or spends what little $ would be needed.

I have many ideas for simple, applied research to many topics in the vibration analysis realm, and I have the space, and the money, but I haven't taken the time.

I agree with Bill also, but, for individuals who are either placed in or choose this line of work, you have to start somewhere. I've been to three TA classes and I can't remember ever being told to accept their tactics and beliefs as the gospel truth. They provide a very good service for those of us trying to "learn the ropes". You have to take everything with a grain of salt.....and don't trust the chart to answer all of your questions directly, but rather use it as a guide to help start the learning process.

So we won't duplicate efforts, where have you already looked?

The TA wall chart that references the stages of wear is based on Chapter 6 of their Intermediate VA Course (not really sure of the level, I got the text when I bought the wall chart).

To paraphrase this copyrighted text it is based on research and in-plant testing and cites rigorously conducted lab tests.

He references a table called Typical Stages of Bearing Degradation (Reference 16) which he attributes to (and uses by permission of) Charles Berggren.

If you want more specifics, call Jim Berry or Charles Berggren. That sounds Swedish so maybe SKF or FAG. Or buy a wall chart. If you do buy the wall chart, spend the extra money on the 150 or so pages of text that explain the chart.

Good luck and let us know how your research comes out.

Thanks to the responses I think I know how to categorize the stages of failure theory.

As for people starting off like Billy, the body of knowledge spelled out in the ISO standards (someone will remember the numbers - I am at home) would be a good start. Learning how to push the buttons is fun, but it is not the serious part of vibration analysis. I find it very helpful understanding much of the theory, but I am more comfortable with that than many would be.

Still there is some theory to understand. Some can be found in standard text books, and other can be obtained through some of the courses offered by various entities. I have had the good fortune to work with many very good people as well as the mis-fortune of those not so good, but lessons can be take from almost anyone. I have worked with people who fake it and learned this is not what I care to do - it is surprising how seldom one hears, "I don't know." "I don't know" doesn't mean that I cant figure it out given the proper resources and effort.

The stages of failure sounds like one of those times where "I don't know" could be applied instead of resolving the worlds bearing problems with a simple categorization.

I believe that I shall spend my money on something more useful to me.

Well, I dont think I'll be getting into the practise of quoting stages of failure in my reports. Seems to be a general concensus that the chart is full of artist impressions that can be used as a guide for the beginner to identify a range of faults....and the real world situation of load, speed, design etc will dictate the remaining life and how long till the fault develops to the next "stage"

Thanks all.

Jonesy.

quote:

Originally posted by William_C._Foiles:
One might ask themselves why it is a part of their belief system...

I am not ready to accept such a theory on blind faith.

Bill,

I have come to believe "the theory" after dismantling a significant number (dozens, certainly; hundreds, maybe?) of brgs over the past 12 years and relating the damage found to the signatures seen. It has been extremely rare that a brg exhibiting stage 3 (per the artist's rendition) symptoms did not have visible defects. I have never disassembled a brg exhibiting stage 4 symptoms (raised floor) that didn't either have damage to multiple surfaces, severe damage to a single surface, or cage failure.

Is that good enough to feel reasonably confident that an analyst can, in most cases apply the examples with very good success and not just be blindly faithful? In my mind, yeah.

Maybe you could produce something that puts the TA chart to shame. Who knows, you may revolutionize our trade. TIA.

Michael S,

I am sure your testimonial will be appreciated in some circles. This occurred on a Tuesday; than must be the church day of the 4 stages.

So Islam's holy day is Friday, Jewish is Saturday and Christian, everyday and again on Sunday as the first day of the week as He arose. Now Tuesday for chart day; does this require grain, wine and oil? Any special paper or just the stuff provided at the side of the stall?

I heard a lot of good practical suggestions about the use and purpose of the 4 stages concept. Like anything it is for each person to use or ignore as they see fit. Asking questions is certainly a good thing. But I didn’t notice anything in this thread resembling religion, faith, blind acceptance etc.

One comment. I have the 1994 T.A. Illustrated Vibration Diagnostics Chart including a description of the 4 stages of failure. The one complaint that springs to mind is that the stage 2 and 3 description of sidebands around natural frequencies

quote:

T.A. Chart 1994
“Stage 2... sidebands may appear above and below natural frequency peak at end of stage 2……
Stage 3….more defect frequencies appear and number of sidebands grow, both around these and bearing component natural frequencies…”

Seems like someone got confused when they wrote that. We expect to see harmonics of defect frequency with sidebands around those harmonics, and the whole pattern peaking in the vicinity of natural frequencies. But I have no idea what is meant by a sideband around a natural frequency.

This message has been edited. Last edited by: electricpete,

I think it is the bearing's natural frequency they refer to --------- or ;-P