## MaintenanceForums

Dear Specialists

we are facing a high vibration in 1X for seal oil pump. this pump has DE & NDE 6310Z, P= 22 KW

On the FFT, the horizontal 1X vibration is dominant and represents about 90% of the global value. We notice that the amplitude on the NDE side in a radial direction is more than twice the amplitude on the same side but at 90Β° angle.

- On the velocity waveform, we observe a purely sinusoidal curve with high amplitude.

- Presence of the inner race ( BPFI ) and outer race ( BPFO ) fault frequencies of the motor bearings, these measurements are detected at high frequencies and  (Demodulation technique) but it's lower amplitude.

We have done a 4 stroke greasing but nothing changes ( we added 6grm each side)

We did an impact test for a similar pump and found that it equals around 56Hz which is close to the rotation frequency of the motor.

I'm not sure but I thought that the outer race was spinning in its housing.

A bearing failure excited by the natural frequency can cause a high vibration.

really we need your expertise in order to resolve or identify what's happing exactly.

Anis

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Tags: 1X, BPFO, High Vibration, BPFI

Can you provide some form of sketch or explanation about the orientation of the transducers?  Your problem statement refers to a vertical pump but then you state "horizontal 1X vibration is dominant".  It would be helpful to know what is horizontal vs. vertical since this is a vertical pump.  Very often transducers are termed horizontal that are coincident with discharge piping.

Hi John,

This pump is vertical position, the orientation are RX, RY and RA radial ( RX mean horizontal and Ry mean vertical for me ).

MOB : RX, RY and RA

MIB : RX, RY and RA

the high vibration was detected in MOB Rx.

thanks

Anis

You totally missed my point!  Vertical pumps are often stiffer in one direction due to the external piping, the discharge line for instance.  A transducer is often mounted in-line with that piping and the other of course at 90 deg.  I do not know what X or Y mean (horizontal or vertical) with respect to your pump.

In the attached graphic note that the "Y" is in line with the piping.

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Last edited by Registered Member
@Registered Member posted:

You totally missed my point!  Vertical pumps are often stiffer in one direction due to the external piping, the discharge line for instance.  A transducer is often mounted in-line with that piping and the other of course at 90 deg.  I do not know what X or Y mean (horizontal or vertical) with respect to your pump.

In the attached graphic note that the "Y" is in line with the piping.

Hi John,

i got your point. let me show you our pump, as attached, this is emerged pump with oil filter in discharge.

We have 3 pumps were installed with same design ( copy past ), but we don't have this issue.

what do you think ? is it excessive clearance between outer race and housing ?

Regards

Anis

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Images (1)

So H is taken 90 degrees to piping and V is taken inline with discharge pipe?

Is this a new installation or existing?

How does the base plate anchor inside the housing? I see a square plate, is the pit/housing also square?

Highly unlikely an outer race fault would create this level of vibration, acceleration values would be high if bearing was bad

Any recent maintenance activities? Pipe strain, mounting plate not properly anchored, assembly errors

What type of coupling?

Is pump flow and pressure normal?

Directional vibration from H to V can indicate pipe strain/soft foot/natural frequency issue. The ratio of vibration from H to V is 3:1, another indication of excitation. You state the natural frequency is close to run speed, rule of thumb you want the natural frequency to be 20-30% away from running speed.

In my opinion, other sources of vibration with this design: worn lower pump bearing/something stuck in impeller/damaged impeller/not operating on pump curve/locked coupling/bent shaft

Dave