Vibration analysis gear damage

Situation

At a customer in the waste-to-energy sector, machines are periodically measured with vibration measurements.

During a periodic tour, a deviation was found on a fin fan.

This fan is responsible for cooling finished steam back to condensate.

The fan is driven by a motor + gearbox. The challenge in a vibration analysis on these gearboxes lies in the accessibility, the varying and slow speed and the large mass, which results in low vibration amplitudes.

Measurements and advice

In the vibration measurements, an anomaly was identified that could be linked to an intervention phenomenon. Since production is only stopped once a year for maintenance, this phenomenon was followed up:

We first see a slow evolution in the measurements. The last measurement shows a stronger/clearer change. When analysing the time signal we see: 

Impacts can be seen on the speed of the layshaft and the output speed.

In view of the increase, the customer was advised to change the cabinet during the upcoming maintenance stop. From the measurements, a serious fault / tooth fracture was suspected.

Feedback

After overhauling the gearbox, we received the photo below from the overhaul company:

Results:

Measuring the machine costs +/- €150/year. This low cost is feasible as the machines in the larger group have been measured for quite some time.

The benefit of this measurement is that the maintenance action can be carried out during the planned downtime. (No loss of production)
If this machine suddenly fails, there is an unplanned production stop. The cost of this is more than 1000 times the measurement cost.