Dear memebers
I am looking for guide lines for acceptable vibration levels for vertical pellet dryers after balancing (just overhauled, no load condition) and alarm and danger levels at full load condition. The dryer speed is 410 rpm, motor driven (15 kW, 1750 rpm) via fan belts. The motor is mounted on the side of the dryer, so dryer vibration is dominating on the motor. Bearings are roller bearings, plummer block mounted, but no access to the plummer blocks, thus vibration is taken on the body of the dryer. Vibration is normally dominated by 1X-vibration. Change in 1X-vibration driven by deposits in the dryer which require rebalancing. At the moment I am using standard severity charts for bearing cap vibration as a guidline. Any recommendations/experience will be wellcome. Thanks in advance.

Dian,

as with all vibration sampling you have considered the transmission path. The further from the bearing you get the lower the detected figure will be fhen the bearings give-up.

You have an ideal situation here to identify "brand new" healthy condition. Assuming that you have eliiminated all post-maintenance faults, you now have a benchmark to work from and possibly the normal operating condition from the historical data. If this is fact then you would be better looking at the statistincal determination of alert and alarm.

Trends, spectral band alarms and spectral envelope are all usefull tools and when customised to the specific application can be more effective than "guidance" figures.

I would also give thought to installing remote sensors with flying lead connections for data collection.

All for now,
CE