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Read our primer articles on Vibration Analysis and Laser Alignment Tools.

hai friends,
i am facing problem in supply fan,motor side vibration found high&we change vibro pad as well as we corrected allignment but still vibration found high.we are using normal vibration meter wich contains velocity,acceleration,displacement read out.I given detail below kindly give suggetion& i am want to know due to variable frequency drive there any chance of vibration increase & if any further details about fan vibration please provide.
vibration before motor NDE(vertical-10mm/sec,axial 40mm/sec,horizontal-409mm/sec).
motor DE(vertical-29.4mm/sec,axial 31.5mm/sec,horizontal-4.2mm/sec),Fan DE(vertical-2.4mm/sec,axial 5.7mm/sec,horizontal-6.2mm/sec)
after action taken motor NDE(vertical-7.1mm/sec,axial 17.8mm/sec,horizontal-3.3mm/sec).
motor DE(vertical-14.9mm/sec,axial 17.5mm/sec,horizontal-4.9mm/sec),Fan DE(vertical-5.2mm/sec,axial 5.7mm/sec,horizontal-8.2mm/sec)
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Yoge,

I am not an expert in vibrations. there should be specialized forums for this question. You have to look to frequency spectrums and based on the frequency peaks, you can have a better idea of what is going on.

Base on the readings high axial readings you showed, it looks to me like misalignment, probably heavy angular misalignment. Check couplings are concentric and replace them if needed and check alignment using precision tools.

Hope this helps
Hi Yoge,

Is there a big difference in operating temperature and the temperature at which you perform the alignment?? This causes problems in hot gas fans. What types of couplings do you have?? gear couplings (Falk/rexnord lifelign)??? grid couplings (falk/rexnord steel flex)?? check the distance between couplings, it they are to close or too far severe vibration can occur.

What is the fan configuration?? motor->coupling->bearing->fan->bearing or motor->coupling->bearing->bearing->fan??

The vibration has been this high since the equipment was installed??? or this happens after a repair??

Another reason could be a bent shaft. to check this use a laser to align the equipment. dismount the laser and mount it on the opposite side of the shaft (180° angle) and check alignment. If there is a significant change in the alignment, a bent shaft could be the issue.

Mechanical looseness could be another reason for the vibration. Check all the fasteners from the fan and motor replace/re-tighten if necessary.

The last thing could be resonance, but this is kind of the last thing. Check if the vibration peaks occur at the rotating frequency or close to its multiples. For that you need a vibration analysis equipment.

Hope this helps.

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