hi all
one of our vertical hydro generator with sleeve bearings shows high vibration at upper guide bearing during start up and subsides after 10 to 12 hours. 1/2RPM vibration is more than 1RPM. what could be the reason?
regards
radhakrishnan

Do you know for sure it is 1/2 RPM exactly? Could well be oil whirl, between 0.4-0.5X. Can you attach a spectrum as well as an orbit plot?

Also, did this phenomenon start after some work was done on the generator, or by itself? Have you tried changing the oil temperature to see its effect on the vibration?

Regards,

Aditya