Very large correlation Horizontal/Vertical 1

[Jurryb]

We have pump running at 5900 rpm. Bearing with tilt pads.
The DE and NDE bearing housing horizontal vibration are very high. NDE -6 mm/sec RMS and DE- 16 mm/sec. Regarding vertical vibration DE- 2 mm/sec, NDE- 2 mm/sec. The axial is NDE – 2,3mm/sec. The spectrum of both the DE Horizontal and NDE horizontal shows that the dominating amplitude is 1x.
The full spectrum is, mm/s RMS:
DE- H 1x – 13,2 2x – 0,2 3x – 1,52 4x - 0,6 5x -0,2 6x – 0,12
DE –V 1x – 2,0 2x – 0,3 3x – 0,1 4x - 0,04 5x -0,12 6x – 0,12
NDE- H 1x – 5,4 2x – 0,3 3x – 1,0 4x - 0,7 5x -0,16 6x – 0,2
NDE –V 1x – 1,6 2x – 0,6 3x – 0,3 4x - 0,13 5x -0,03 6x – 0,11

This is not unbalance. Correlation Horizontal/Vertical is more then 2 (13,2/2,0=6,6)! .

Likely this is resonance.

My question is, what is the failure in our pump?

Thanks.

 

[TPL]

You will have to provide more information.

Firstly, how old is this pump? Is it brand new or has it been in service for several years?

Secondly, when was this 'problem' first noticed - has it always been like this or did it develop immediately after some maintenance had been carried out?

Has the rotor been balanced recently? If so, how was this done in a workshop? At what speed and to what specification?

 

[Jurryb]

"Firstly, how old is this pump?" - 12 years old

"Is it brand new or has it been in service for several years?" - in service 12 years


" when was this 'problem' first noticed - has it always been like this or did it develop immediately after some maintenance had been carried out?" - after maintenance, pump rotor and bearing pads was changed.
To repair the pump vibrations were such, as
Horizontal, NDE -4,7 mm/sec RMS and DE- 7,3 mm/sec. Regarding vertical vibration NDE- 3,7 mm/sec, DE- 2,6 mm/sec.


"Has the rotor been balanced recently? If so, how was this done in a workshop? At what speed and to what specification?" - rotor as spare parts, was balanced at the factory, which produced this pump

 

[TPL]

Well, it could be resonance but, if all you have done is change the rotor and bearings, what else has changed to allow the resonance to show itself now?

It would help if you could carry out vibration measurements during a shutdown.

When was the rotor factory balanced and how was it stored since it was last balanced - best practice is to store spare rotors vertically and check balance before use. Storing them horizontally allows then to develop a bend under their own weight.

It would be worth putting a dial gauge on both ends of the shaft and turning it slowly by hand to see if the shaft is physically bent.

The difference between H and V vibration, especially at the DE is one symptom of alignment problems - was realignment carried out? Have any vibration changes taken place on the driver?

It would help if you coudl carry out vibration measurments during a shutdown