New tech with a question

Hi all,

So first post here. I am still new to VA, so bare with my likely poorly explained questions. Using 2130's and MHM 5.51 at work, to carry out work on a coal plant. I confidently collect and analyse, but looking here to broaden my knowledge. One question I thought to start with, was with early stage bearing faults. I have noticed now and then whilst analysing given pulleys with early stage faults in Peakvue. The levels will be very low and have not become noticeable as a peak and harmonics on the Velocity spectrum. Yet they may appear as sidebands on an excitation frequency in the velocity spectrum. Could anyone please explain this to me??


Original Post
Hi Luke,

I guess you better post it to vibration/alignment/balance board here.

I truly not got your point of question, but I'm Russian this is my diagnose.

Did you asking why early stage of rolling bearing defects almost not visible in Velocity spectrum and level in PeakVue is low? Then they talked about stress waves.

Kind Regards,

Konstantin Lavrov

Thanks for your response.I am asking why you can see a fault in Peakvue and its almost not visible in Velocity.But more in regards to what I saw once again today. The pulley that I was analysing, showed a peak and harmonics for an outer race fault in the peakvue. But not in the velocity. Yet I did find a peak maybe from a closely located gearbox and it had sidebands exactly matching the bearing fault in the peakvue. This outer race frequency was not related to the gearbox in any way. Hope you can make sense of that.



Not sure I make complete sense of what you are after but is it possible that vibration from the nearby gearbox is transmitting to the pulley in question. You need to remember that peakvue can be very sensitive so its possible you are picking up transmitted gear frequency that just happens to match your pulley bearing outer race fault.

I work on paper machines and this is a common occurence wear nearby rolls, gears and pulleys can transmit vibration to eachother which matches bearing frequencies.

I hope this is what you meant????
Sinski thanks for your help. I was going to post the spectrum but cant remember for the life of me the pulley. Will do so when it rears its head again. I am pretty sure its not a transfer of vibrations from closely located assets. But rather a forcing frequency within the bearing. Will ask again when I can provide more.
if the frequencies in question don't show up in the velocity spectrum at all or the time domain, I usually get them to grease it and see what happens.No greasing doesn't fix defects but it usually helps the peakVue. You can probably do an acceleration spectrum and see noise over 1000 HZ with sidebands of bearing defect.If this is there I would probably recommend they change the bearing when time permits.If it's ONLY in peakVue grease it see what happens. Also things depend on how critical this machine is and how fast the bearing turns.
When I take data I have my 2130 set so I can see what I'm collecting. If something peaks (no pun intended) my curiosity in PeakVue I go into manual analyze and take a high frequency data point so I have something to compare when I'm back at the computer. I also do a speed detection point to determine real speed for analysis.
Hi Luke, as Sinsk points out Peakvue can be very sensitive - with+ the correct settings if I can add that. So sensitive in fact that you don't want to make a changeout decision based on it alone (in most cases) Sinsk will know that paper machine dryer bearings or the like might show cracked inner races very well in Peakvue but they are almost always there in accel or vel as well. Maybe not so clear. So treat Peakvue with caution it is not the be all and end all it is purported to be. Needs to be handled with care. There are too many people out there that hang their hat on Peakvue. It should be considered in conjunction with normal acceleration spectra. rgds.

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