Our plant has a cryogenic turbine for air separator.These days we found the vibration of the turbine shaft had larger fluctuation range.from 0.20mils to 0.40mils.we checked the machine with CSI2120.What happened in our machine?

TURBIN.RTF (20 Kb, 63 downloads) turbine vibration

wenjie lu,

0.48 x SS is typically caused by Oil Whirl in journal bearings. Make sure you do not have a shaft critical speed (balance resonance) near that frequency or you will have Oil Whip, that can destroy a bearing very fast.

Check your bearing lube oil temperatue and viscosity. Sometimes a change in either one can minimize or eliminate Oil Whirl. Other fixes are more involved and may include changing bearing clearance, bearing modification, or bearing design (Tilt-Pad type is better).

Walt

Walt has given very sound adivse. A tilting pad only exposing ~35% or less doesn't allow the 38-48% to occur.

Checking to ensure the correct cSt @ temp is in keeping with someone can grab the wrong can. Check and make sure you have the right oil in the system. Wouldn't be the first time someone put in the wrong oil.

Thanks for your help.
We added some new oil ten days ago.We have sent a oil sample to analyse.

Apart from the suggestion above, is there a possibility of rubbing ? Presence of subsynchronous and multiple harmonics hints that ?