Vertical Motor High Vibration.

Hii All.

 I have a Vertical Motor where i'm facing high Vibration problems.

Fmax-1000Hz , 1600 LOR

Motor NDE- Hor-7.07 Ver- 4.77 and Axial- 0.91 mm/sec RMS.

Motor DE-Hor-4.07 Ver-2.50 and Axial-1.39 mm/sec RMS.

pump De-Hor-3.2 Ver-2.2 and Axial-1.01 mm/sec RMS.

But while taking data with 4000Hz and 6400LOR i could clear see the vibration going up to 10mm/sec RMS. and the acceleration value going to 58.22m/s^2 RMS.(Which was previously 1.54m/s^2 RMS while the Fmax was 1000HZ). I know that increasing Fmax will also increase Acceleration value as higher frequencies are more sensitive to acceleration but what i found in my vibration spectrum is bit complicated.

A high frequency Peak at 80587.5 CPM with amplitude of 5.39mm/sec RMS. And it has Running Speed Sidebands. But the running speed side band has amplitude of only 0.26mm/sec, whereas the 100 HZ side band has a Amplitude of 2.22mm/sec.

And some 2*(2*LF) and 4*(2*LF) also present.

But i'm assuming 74587.5 CPM as Center frequency because it has the matching hamonics.

I'm suspecting Rotor bar looseness and Severe Structural looseness.

Kindly help me solving This Pattern.


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Spectrum and TWF.
Original Post

First of all, 5.39 mm/s @ 80587 CPM is equivalent to around 49 m/s2 so high acceleration value at increased bandwidth is not a surprise. I have seen some motors which had RBPF / SSPF with some humming noise, but running without any damage for long time. 2*LF sidebands normally indicates stator looseness, but you need to monitor the trend / compare with similar equipment before taking any decision.


We had same experience of problem on CEP in our company, what i do to correct to situation is.

1. Re-tighten the base foot bolt of the pump to eliminate the structural looseness and check the support of the piping.

2. Try to uncouple and do motor solo run test with and without flange, check starting voltage current. 


Thanks for your Kind reply. I have solved this problem By tightening the Bolts of Motor face plate as i found some Movement there.

2-Try to uncouple and do motor solo run test with and without flange, check starting voltage current. - What will be the reasons if i will get high Starting Current. Possibly any Rotor Problems or any thing else??

I do check the starting current/normal current/voltage for further investigation on electrical problems because in our plant we had a problem on system voltage which affecting our motors. 

If any case you have a problem on your rotor or have doubt to rotor problem, do motor solo run.. 


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