We just changed out a 3600 RPM RO water pump due to the impeller rubbing on the casing. After the change out, the pump immediately began vibrating at 1.3 IPS in all directions at run speed. Before the change out, the 1 X amplitude was less than .15 IPS. The mechanics who did the installation say the alignment went well and is in spec. Any other thoughts on where this coud be coming from?

0730PU16,_Follow_Up_Vib_Analysis,_08-29-07,_MDK.doc (137 Kb, 67 downloads)

Mark,

If I were you... just to be certain I would re-check the alignment (with a laser unit if possible). Did they use a laser unit or dial indicators? If they used dials, ask this question: "What was the Bar Sag measurement?".

Can you upload some pics? So we can see what this unitlooks like.

Regards,
DanV

What is your setup? Is the spectra showing 3600 or 60 Hz? Could it be 60 Hz and electrical? Cable problem or loop?

And if laser was used; was calibration checked? If dials; all tight and SAG checks made? Run-outs on shaft and coupling?

They used a vibra-lign laser aligner. This pump is scheduled to have the alignment re-checked tonight. I don't have a photo to load, but it is a standard Goulds pump set up, feeding a reverse osmosis water filter. Thanks for the reply, Dan.

Sam, the setup is a Ludeca Vibescanner, 3200 lines of resolution. The spectra is showing a dominant frequency of 3581 cpm, and the vibration is all coming from the pump. The motor looks good. As Dan V suggested, we are re-checking the alignment tonight. Thanks, Sam.

Mark,
The symptoms indicate pump rotor unbalance. Possible causes are unbalanced impeller, eccentric impeller shaft mounting, bent shaft, or coupling hub unbalance.

Walt

Mark,
Looks like unbalance of pump rotor
Regards
Syed Ibrahim

quote:

Originally posted by Mark K:
We just changed out a 3600 RPM RO water pump due to the impeller rubbing on the casing. After the change out, the pump immediately began vibrating at 1.3 IPS in all directions at run speed. Before the change out, the 1 X amplitude was less than .15 IPS. The mechanics who did the installation say the alignment went well and is in spec. Any other thoughts on where this coud be coming from?

Check if the pump pulled a piece of wood which is touching the impeller during pump operation.

Mark,

As pointed out above imbalance and misalignment - are possible causes which have to be confirmed or ruled out. Axial vibes are kind of high, so phase difference across the coupling may help to diagnose angular misalignment.

One more thing to check out is anchoring bolts tightness despite the fact that no TS harmonics are present. The system still can be linear. Check also pump shaft runout.

Originally posted August 30, 2007. Wonder if it is still running with this high vibration after nearly 4 months?

please get the shaft run out readings near impeller area before assembling new impeller from the mechanics.check phase difference 180 deg across bearing blocks in the same direction if pump is simply supported type.Since the impeller has severely rubbed the casing chances of excessive stress on shaft leading to bend cannot be ruled out.Since vertical readings also show high values, also check support bolts for looseness.
Bye