False Brinelling

External vibration causing bearing fault damage.

Two redundant Sulzer wastewater pumps.

A damaged bearing, due to false brinelling.


Top plot: False brinelling level for two redundant Sulzer pumps, monitored for a period of three weeks.
Bottom plot: The Vibration RMS level for pump 2, monitored and plotted for half a day.

Forcing a machinery to vibrate when it is not operating can be very harmful to machine parts like shaft seals and bearings. These vibrations named “False Brinelling” typically come from surrounding machines through the piping system and/or the foundation. The EWA False Brinelling parameter is calculated on a 24-hour basis.

This case shows a false brinelling value of around 37% for pump 1 and 79% for pump 2 – quite high values for both pumps, but extreme high for pump 2.

Looking on the Vibration RMS value for pump 2 this has a level of 3 mm/s when the pump is operating, but as high a level as 15 mm/s when it is not operating. The course could be related to resonance or looseness.

The conclusion is that the false brinelling level is all too high. The installation should be inspected and modified.
The actual situation is very damaging for the motor bearings, and the bearing lifetime is short.