Vibration measurement tooth engagement

A client in the fertilizer industry asked us for advice concerning a strange noise he had noticed somewhere near the drivetrain of a drum.

Observations after measurement:

Vibration measurements and the accompanying headphones allowed us to locate the noise at the pinion and the pinion bearings.

The pinion bearing at the non-clutch side showed the clearest result.

The following chart shows the measurement on the bearing block at the non-clutch side.

The bottom graph shows the time signal. We can clearly see the irregular rise and fall associated with little throbs. The top graph shows a spectrum where the frequency of 1330cpm stands out. When on site, we agreed that this is most likely the frequency with which the pinion engages the gear ring.

This assumption was confirmed by the data we received via email: the gear ring has 150 teeth and the pinion has 23 teeth (23*58cpm = 1330cpm). We are dealing with an inconstant, bad engagement of the pinion. Possible causes are excessive bearing play or a slanting axle. When we inspect the bearing block at the clutch side, we notice that there is a deviation in the distance between bearing block and clutch. Probably the gear ring pulls the pinion along slightly. This automatically adjusts the pinion and therefore there is no vibration. Then the pinion ‘falls’ back, resulting in engagement phenomena.

Advice:

We advise:

- Maintenance of the alignment between pinion axle and gear casing.

- Maintenance of the height of the bearing block on the free side.

- Maintenance of the bearing play.

After adjustments the tooth play both left and right should be checked.

Conclusion:

By performing a vibration measurement the cause of the strange noise became clear. Since the cause is now known, proactive maintenance can be scheduled. By improving the alignment/positioning of the bearing blocks, the life span will improve considerably. Considering the low cost of such parts, this investigation has saved a lot of money.