Turbine trip due to high vibration

[SA07]

Hi
During an annual maintenance, our turbine was dismantled, cleaned, balanced. The alternator rotor was removed from the stator for maintenance.
After start up, the turbine is tripping due to “DE journal high vibration X “. Several attempts were made.
On barring gear, all vibrations are good.
The turbo-alternator was synchronized with grid on 24.01.22/ 22.00 to 25.01.22/ 04.00.
Steam Turbine: 44450 kW 4600 rpm
Alternator :three-phase, four pole 60133kVA 11kV
What may be the cause of this high vibration?

 

[pierreick]

Hi,
Did you calibrate or replace the vibrations sensors and /or electronic parts?
Pierre

 

[SA07]

No vibration sensors or electronic parts were replaced.

 

[JJPellin]

I am sure you have already reviewed the detailed characteristics of the vibration. Review dominant frequencies, shaft centerline, polar and Bode plots. These are the possibilities that occurred to me:

The balance shop did a poor job and the turbine rotor has a severe imbalance.
Internal rubs at the nozzle ring, tip seals, inter-stage laby seals, high pressure packing, low pressure packing or bearing housing laby seals
Coupling assembly error
Bearing assembly error

Of these, I would lean toward a rub as the root cause.

Johnny Pellin