This is a Single stage Cebtrifugal condensate pump. We faced high vibration in this pump and the predominant frequency of vibration is 11.3X of the pump running speed. This is no matching with bearing fault frequency.

We have done a bump test too but could not notice any natural frequency in the vicinity.

Last year a similar pattern was noticed and the bearings were replaced. After replacing the bearings vibratiion levels came down, but when the removed bearing were inspected nothing abnormal could be noticed.

What could be source of this frequency?

How about "Soft Foot" issue? Soft Foot issue is when uneven pump base plate and non machined bed plate induce pump vibration when holding down bolts are tightened.

This is a common problem that many plants encounter. Fixing this is not easy and can be done by laser alignment.

Rgds Brighton

Anbhazhakan
Could you post some spectrums and waveforms on this problem or email them to
info@alertanalytical.com we will look at this.
Seems like your missing something here.

Mark

Please find attached the spectrums taken on this equipment. We could see harmonics of this frequency too.

This message has been edited. Last edited by: M Anbu,

Spectrums.doc (94 Kb, 49 downloads) Spectrum of the equipment

Anbhazhakan, I havn't seen this before. It doesn't look like resonance. It is too defined. It would be interesting to find out the cause.
Good luck
Joe Mc Cormack

Hi Anbhazhakan. Thanks for the spectra - I am assuming that two of these are incorrectly labled? They can't all be "vertical" surely?

Maximum Vibration was noticed in vertical direction, hence I have attached spectrums of DE & NDE Vertical only.

After replacing the bearings vibrations came down ( Reduced from 10mm/s to 5 mm/s ), but still the predominant frequncy is the same with harmonics.

I hope in case of Resonance and flow induced vibrations there cannot be harmonics.

What else can generate high frequency vibration in a pump?

Regards