Vertical Pump and Motor vibration

[tolk]

After we set a vertical pump and motor, upon startup, the pump had vibrations exceeding the recommended alarm limits. When the pump base bolts are loosened, the vibration falls within the acceptable alarm limits. What could be causing the high vibration when the pump base bolts are tightened down?

 

[electricpete]

resonance is one possibility. You may have detuned the resonance when you loosened the bolts.

What frequency is the vibration?

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(2B)+(2B)' ?

 

[drawoh]

tolk,

Are you sure it is the pump that vibrated, and not the structure it is attached to?

JHG

 

[JJPellin]

What style of pump are you referring to? Some vertical pumps state specifically in the instructions that they are not supposed to be bolted down to the foundation. Doing so could cause a distortion within the pump and result in internal misalignments and vibration. I have also had vertical pumps where pipe strain was the source of the vibration. Our standard method of evaluating pipe strain does not work with some vertical pumps. But, the piping alignment can be checked. If you break the suction and discharge piping loose, the flanges should remain in good alignment. You should be able to put the bolts into the two flanges with no more force that you can apply with your hand. If you have to pull the pipes into alignment with mechanical assistance (come-along), then the piping alignment is not good enough.

Johnny Pellin

 

[electricpete]

Good point by Johnny Pellin

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(2B)+(2B)' ?