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.

• The spectrum taken...