Dear all,

There is a ID Fan motor outboard bearing and its running speed is about 960 rpm.

Recently, we observes there is a significant PeakVue vibration increase and a broadband random frequency component growing up. However, it is not related to the bearing fault frequency.

Attached please find the vibration spectrum for your reference.

Is it related to lack of lubricantion and we heard some 'sa sa' noise around the bearing house.

thanks and regards

kk

IDF6A.doc (46 Kb, 47 downloads) spectrum

Why not put your data collector into live mode and add some grease to the bearing in question. if the vibrations levels change you will have probably answered the question.

Remember when trying to determine what you see in the results, first eliminate what it is not!

Keep it simple!

Hooch

yes i did it from another bearing which have similar problem. Although, the PeakVue vibration will reduce significant after the grease injection, the vibration level will be increase after one or two week later.

is it have another problem ?

First of all some questions: What is the peak waveform amplitude? What do you see in the autocorrelated waveform (no periodicity, cage frequency, or something else). How is the sensor mounted (flat magnet on a clean smooth flat surface)?
If the autocorrelated waveform shows no periodic content or cage frequency and harmonics it is probably a lube problem. The energy is coming from the friction generated from the metal to metal contact. If it is a lube problem and the high amplitude drops off a couple weeks then comes back it could be the wrong grease for the bearing. I have some fan bearings that I have this problem with. Are the bearings roller or ball? Since it has increased over time it would be a good idea to see if any lube practices has changed in the last few months and monitor for any bearing defects to appear.

Jim highlights an interesting point with the lube,the load rating may be wrong for the application.I would try to find out what has changed since the previous survey. Ask everybody that has anything to do with this machine.
Check the machine is running the exact same configurations, ie: speed, load amps etc.

I would be looking for some looseness within the bearing. This has a tendancy to push/ extrude grease very quickly raising the noise floor and giving indications of lack of lube.

What does the axial reading results look like?