Transient Refiner Vibration

[jmack]

I presently am working on a refiner vibration (Two 5000hp synchronous motors facing each other 1200 rpm), that has a vibration under load with the following FFT characteristics:

1200 cpm - 0.0168 ips
2400 cpm - 0.0372 ips
3600 cpm - 0.0116 ips

2138 cpm - 0.3524 ips
4276 cpm - 0.0434 ips
6414 cpm - 0.1419 ips
8552 cpm - 0.0575 ips
10690 cpm - 0.0646 ips

Under no load the refiner vibration looks like:

1200 cpm - 0.0134 ips
2400 cpm - 0.0285 ips
3600 cpm - 0.0048 ips

With no peaks at 2138 cpm, nor harmonics of 2138 cpm.

I have looked at the bearing frequencies for this and FTF's are at 560 cpm, and 200 cpm for the tapered roller bearings and thrust bearing respectively. All other bearing frequencies are above 3200 cpm.

The frequency at 2138 has also changed inversly proportional to the cross conveyor speed anywhere from 2260 cpm to around 2100 cpm, the cross conveyor is single flute and feeds a single flute feed conveyor which rotates at 750 cpm and feeds the refiner.

We are presently preparing to look at phase analysis and a shaker test on the refiner structure as well as looking at controls and electrical components.

Anyone seen anything similar in the past?

MacK.