Case – Bearing current flow 

A company in the energy industry noticed a strange sound on a vertical pump.

Observation during measurement

The machine was measured with a data collector, leading to the following results:

The machine shows increased peakvue values. These values indicate the presence of high-frequency vibrations.

Measuring point 2 has the highest value. The measurement is shown in the following graph, with an indication of the fault frequencies (outer ring) of bearing 6319.

The frequencies highlighted with the red ellipse are striking. They match the frequency of the housing.

Advice after measurement

We advise replacing the bearings of the motor at the next opportunity.

Observation after bearing replacement

Inner ring

Outer ring

Conclusion after bearing replacement

The bearings show clear traces of current flow.

Closer inspection of the motor revealed that an axle brush was installed. Due to a faulty assembly there was hardly any contact with the axle. This resulted in a situation where the built-up current could not be conducted from the axle, causing bearing current flow.

Case conclusion

Using vibration measurements we have been able to show the cause of the deviant sound.

A bearing damage analysis clearly showed the cause of the damage on the bearing. The machine has immediately been improved, thus preventing future damage by this cause.