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3. Case study
3.1 Fan motor bearing fault
Here's how a diagnosis was carried out on a motorized fan unit at an incineration plant in the Paris region, driven at 2,420 rpm by a 300 kW motor and pulley-belt transmission.
The values measured during a periodic inspection show that, on the motor bearing on the pulley side, the alarm threshold defined for the global indicator "RMS speed" standardized to 10/1,000 Hz has been exceeded. The value of this global indicator, measured in the horizontal radial direction, has risen from 3.9 to 12.2 mm/s since the last collection, whereas it remains more or less stable on the other fan bearings and on the vertical radial measurements of the bearing in question.
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Case study
Measurement precautions
Standardization
Association française de normalisation AFNOR
NFE 90 300 May 1978 Mechanical vibration of machines with a rotation frequency between 10 and 200 per second. Basis for the development of assessment standards.
International Organization for Standardization ISO
Notion of cepstrum
1. Definition
There are generally two definitions of cepstrum.
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The first, particularly appropriate for vibratory signals, defines it as the inverse Fourier transform of the decimal logarithm of its direct Fourier transform (complex spectrum):
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