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Situation – High vibration (55 mm/s rms) on one of the critical drive units
prevented the paper machine from full-speed operation. The motor had been changed once, the universal joint shaft
twice, and the gearbox near the drive roll once. A paper machine consultant had studied
the case for 2 days, but was unable to give advice.
Solution – Bently Nevada Machinery Diagnostic Services (MDS) looked at the data gathered
by plant condition monitoring group and the paper machine consultant. After gathering some additional
data it was concluded that unbalance was the problem. Further investigation showed that too large of a key
had been used between the universal joint shaft and the gearbox and was the root cause of the high vibration.
Result – While at the site MDS balanced the machine by adjusting the size of the key.
The machine vibration level dropped to within normal limits, and the paper machine was able to increase
speed from 1050 to 1200 m/min. The MDS work was paid back in two hours.
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