We are facing one vibration issue in one of 660 MW turbo machinery. The vibration peak and phase datas are attached for your reference.
The problem what we are facing is while performing balancing the FSNL vibration readings are drstically reduced however the full load vibration datas are further increased compared to before balancing datas. We have taken 3 trials.
First trial we have added the weights in LP rotor- B both side( bearing plane 5 & bearing plane 6) We added 885 grams in bearing 5 at 270 degree from the key phasor and 445 grams in bearing 6 at 90 degree.
The vibration levels are increased however the phase angles are nearly same and hence correction weights are calculated and shifted. This trial we run the unit only up to FSNL speed and we have not increased the load.
Second trail weights are added in LP rotor -B. Bearing 5 & 6 ( 322 grams@340 degree in bearing 5 and 258 grams@110 degree in bearing 6). This time vibration in full speed no load are reduced upto satisfactory limits and loaded the unit. However the full load vibration levels are increased in generator Front bearing -7. The load vibrations in beairng 5 & 6 are acceptable level.
Third trial was taken by adding weights in generator coupling 344 grams@350 degree. This time again FSNL vibrations are reduced in generator however the load vibrations are further increased.
So gentlemens your advice in this regard is highly appreciated.
We would like to know that the by shifting the weights in generator coupling alone will improve the vibration levels or not.
Why this much changes in vibration levels between no load to full load vibration.
Thanks and regards