Is it possible to have bearing fault without harmonics, see atachment

bpfo.rtf (66 Kb, 98 downloads)

Yes it is possible. Do you have a PeakVue reading? A higher resolution around that peak may show more. Display in acceleration G's to increase amplitude of higher orders. Longer waveform may show modulation or beat.

I agree with Bill that it is possible.
But just to make sure, are you confident that you have the correct RPM in the database? You might try looking at the spectrum in Log units. Sometimes that will bring things out of the floor so that you can see that harmonics are present after all.

The questions I would be asking are:
1) What does the historical data show?
2) Has the peak been there before (see waterfall)
3) Is the bearing in oil? If so what is the quality of the oil?
4) Is the bearing greased? If so has it been overgreased?
5) Is the temperature increasing?
6) Is there something close that could be exciting/transmitting this frequency?
Seems to me that the trend has not increased that much and the average is around 3 mm/s anyway. May be due to calcification or particles in the lubricant, both of which could give you a single peak.
Hope this helps

An envelope spectrum that has only the BPFO characterist frequency ( this includes a PeakVue spectrum) is usually a symptom of outer race wear, >80% probability, but it can also be a symptom of outer race spalls, < 10% probability, or misalignment of the outer race, <5% probability, or a defect of surface processing + strong radial tension, < 10% probability. The wear can be the result of rolling element skidding which can be caused by lubrication and load issues.

See:

http://vibrotek.com/article.php?article=articles/new94vi/index.htm

With this being a "roll" applicaton (but not always limited to "rolls") and a C3 fit bearing, my guess would be that the rollers are not rolling when they come into the load zone and are being forced to accelerate from 0 to max speed, and this is causing what I refer to as a "slide defect".......... The slide is something like a "smooth" worn area, sort of like the bottom area of a kids play slide or the bottom of a snow ski ramp. The area will be worn extremely smooth but will be several thousandths deep from the continious sliding of the rollers striking the same area.

Usually there is the fundamental peak (fairly large in amplitude) and MAYBE 1 or 2 extremely small harmonics.

OMOAICBTW

To All,
thanks for your replies and comments, to answer a few of the Q's you asked, (1)I do have radial Peakvue and the D.end has low level bpfo with harmonics. (2) Rpm is 1700 in Database and 1706 on spectrum (3) bearing is greased, under greased if anything, I've had issues with our greaser in the past (4) this roller is surrounded by others of the same configuration
For now i will continue to monitor for any changes.

Duncan,
thanks for the link, i've had time to come back and read the article,
Ralph,
thanks for the explanation in laymans terms that a beginner like me can understand

Jonesy,

Do you have headphones that you can have the lubricator listen to the bearing with while he is lubing it? If so, I would get together with him and have him listen while you monitor and you will both see the change as a bearing is lubed. UVLM makes a headphone lubing unit that has hollow accelerometer (I guess it's an accel) that you connect to the grease finning coupling and listen to the bearing as you lube it. The look on a lubricators face the first time he hears it is priceless and it is a good learning experience for anyone.

You can also get headphones and an adapter for your CSI unit.

One of the shortcomings for the uvlm unit is you won't hear much if you have remote lube lines.

I would guess that you have an out of round bearing housing but I disagreed with Ralph once before about a roll bearing...

G,day Danny,
I dont have headphones, but i have measured in live mode while being greased, this was after the greaser reckons he'd greased the unit but i was sure he hadnt, the difference it made had the same effect as i assume the head phones would.
to all, if i have this smoothly worn outer race, mentioned earlier in the thread, would the next sign of increased wear be looseness?

quote:

if i have this smoothly worn outer race, mentioned earlier in the thread, would the next sign of increased wear be looseness?

Not necessarily.