Newly installed Motor Driven Between Bearing pump is vibrating heavly.
Pump Speed=3000 RPM
1.Pump Driving end brg Horizontal vib=26 mm/s
2.Pump Driving end brg Vertical vib= 4.2 mm/s
3.Pump Non-Driving end brg Horizontal vib=25 mm/s
4.Pump Non-Driving end brg Vertical vib= 4.9 mm/s
5.Motor Max Vib=3.4mm/s
6.Alignment is checked by Laser Kit and is within limits.
7.Pump Driving end brg Horizontal & Vertical phase difference is 140 Deg.
8.Pump Non-Driving end brg Horizontal & Vertical phase difference is 37 Deg.
9.Pump Axial maximum vibration=3.8 mm/s
10.Pump Driving & Non-Driving end Bearing Axial vibration is in Phase.
11.All vibration contributed by1X.

Please Comment, What could be the reason of vibration.

quote:

Newly installed Motor Driven Between Bearing pump

Did you check pump mounting. There may be loosened bolt. Since horizontal vibration is extremely high in comparison with vertical vib. level.

Hi bpcl,
woow your horizontal is very high :-)
Ok, please check the natural frequency on horizontal direction..to clarify there is no resonance.
The ratio between Hor/ver more then 3 times.
Your phase difference between NDE & DE is very big (140), normally it's 90 +/- 30 degree.
Looseness or feet weakness problem can be suspected.
Once again, you should check the connecting between pump and piping, is there any excessive stress when installed.

Rahardi
rahardi@softhome.net

Hi bPcl
Check for piping strain problem(excessive tension in one of the piping connections)this cause directional vibration on the pump

Hi bPcl
Some manufacturer gives horizontal locking arrangement in multistage pumps in the barral. Same can be checked. This will help

You may run the motor solo and check the vibration.If ok then the problem is in the pump. Be sure that pump is properly balanced.Check the alignment by rim and face method.Laser alignment tools may sometimes give erroneous data.Probable cause of high horizontal vibration is unbalance.

Regards
Anis

pl check out vibrations of motor..
is the whole assembly of motor & pump installedon same base frame?
I might suggest to strengthenPumpbase frame in horizontal directionthis will sure reduce vibrations.
Most importantly u must check forImpeller unbalance

Check pump for resonance. With the pump shut down, measure the horizontal vibration. I know that sounds silly to check it when it isn't running but it is important to look for vibration that might be coming from near by equipment.

Check the resonant frequencies by hitting the pump with a dead blow hammer or soft face hammer (with the unit shut down) and look for any peaks in the spectrum around 3000 CPM.

Plz check runout of the pump at different place.I think shaft is bend. If bend is there u will get high horizontal vibration

Since this is a new pump it may be a bad impeller.

Run the pump dry. If the vibration goes away it is "Hydraulic unbalance". This means the pump casting was uneven so when it is pumping there is more fluid on one side that the other.

Machining trues up the OD but not the internal cast surfaces.

I have case like this. Shaft is bent (new shaft and length is 1.5 meters).

Hi bpcl!
Finally, have you identified the reason of high vibration?
Please Comment,do you removed the reason of high vibration, and in what way?

Multistage pumps( 9 stage) are having Unbalance problem. Horizontal Vibration is directional and shows 1 X RPM problem. The Time wave form also sinusoidal. When the Shaft and impeller taken to a Balancing M/c it shows unbalance in two planes. Now we can not weld on impeller. Removing mass from impeller is not possible because impeller thickness is not there. Please suggest how to balance.

quote:

Originally posted by bpcl:
Newly installed Motor Driven Between Bearing pump is vibrating heavly.
Pump Speed=3000 RPM
1.Pump Driving end brg Horizontal vib=26 mm/s
2.Pump Driving end brg Vertical vib= 4.2 mm/s
3.Pump Non-Driving end brg Horizontal vib=25 mm/s
4.Pump Non-Driving end brg Vertical vib= 4.9 mm/s
5.Motor Max Vib=3.4mm/s
6.Alignment is checked by Laser Kit and is within limits.
7.Pump Driving end brg Horizontal & Vertical phase difference is 140 Deg.
8.Pump Non-Driving end brg Horizontal & Vertical phase difference is 37 Deg.
9.Pump Axial maximum vibration=3.8 mm/s
10.Pump Driving & Non-Driving end Bearing Axial vibration is in Phase.
11.All vibration contributed by1X.

Please Comment, What could be the reason of vibration.

BPCL - its pure case of structural resonance. It can be solved with systematic phase readings and some of the adjustement on all system components. After all directionsla vibrations are easily solved with lot of data on mode shape.

A pump I monitor has same kind of directional vibration with its highest vibration in the horizontal direction. The strange thing is that the outstanding peak is asynchronous (1.247 times TS) on both the inboard and outboard of the multistage pump. This peak has all the attributes of resonance but the fact that it is asynchronous is confusing. The amplitude is 13mm/sec (RMS)and it increases within hours from a starting amplitude of 1.06mm/s (RMS).

I will appreciate any information on how to handle this problem.

Dear BPCL,

As per the data given by you, motor bearings seams to be OK as the vertical component is low. Main reason for this type of vibration is the imbalnce of the impeller. Please make sure that they are well balanced. Also check the intermidiate bushes or bearings if it is multi stage.

It would be helpful if you could provide the data on motor power, rotor lenght, rotor diameter and weight.

Jagath.

Dear Bpcl,
I hope, there is softfoot / Inadequate area contact between pump base foot and baseframe problem in your pump. for confirmation, just take a reading in each foot and note the diffrences.

Hi
Please check runout of the shaft. it shouldnot be 0.03mm/100mm dia shaft. Take coastdown for resonance.

pure 1x.. in phase.. likely resonance or unbalance. i will go for unbalance. unbalance not necessary mass unbalance. it may well due to unbalance magnitude attributed by bent rotor

BPCL,
I would have to agree this very much sounds like Resonance (due to the highly directional vibration). However, you cannot rule out rotor eccentricity. I agree with those who recommend conducting an impact natural frequency test with the machine stopped. I would recommend you use a 2 channel analyzer connecting a force hammer to one channel and an accelerometer to the other channel. Then, measure the Frequency Response Function (FRF) in the horizontal direction that can be measured by so many analyzers of today. Performing an FRF can conclusively confirm if resonance exists (by looking for a major phase change at the 1 X RPM frequency approaching 180 degrees; also by looking at the Imaginary spectrum if measuring Accelerance (g/lb or g/N); and by confirming you have a Coherence of approximately 0.95 or greater at this particular frequency).

I likewise would have to agree hydraulic unbalance cannot be ruled out.

Have you conducted any natural frequency tests yet? If so, please let us know what your results were.

Thanks,
Jim Berry, Technical Associates