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High axial vibration in a centrifugal fan

Hello all,

Do we observe high axial vibration (and more than radial vibrations) in all centrifugal fans ?

I have a case where overhung centrifugal fan driven by motor and coupled with belt drive. Following overall velocities (10-1000 Hz RMS) recorded,

Axial: 15 mm/s, Horizontal: 12 mm/s, Vertical: 8 mm/s

I have also attached spectra (freq vs RMS velocity). What are the possible faults; to me looks like looseness.

Similar cases (high axial vibration for centrifugal fans) reported earlier in this forum. I was wondering whether its machine configuration, fan operation, or common design issues (in once case it was a weak bearing block).



Images (2)
  • Centrifgual_fan_axial_fft: Axial velocity spectrum
  • Centrifgual_fan_horizontal_fft: Horizontal vibration spectrum
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