The shaft vibration of bearing no.8 for one ultra-supercritical unit has been nearing to shutdown value

the shaft vibration of bearing no 5

6 and 7 as well as the vertical vibration of bearing pedestal no.3

all have been surpassing the alarm values

and large fluctuation of vibration has occurred in operation.Through test

diagnosis

and analysis

it shows that the main causes leading to vibration are non-balancing of the excitor's rotor mass

and deterioration in connection situation of the coupling between the low-pressure cylinder and the generator under large load condition

as well as resonance vibration between the bearing pedestal no.3 and its foundation structure.For this

through carrying out dynamic balancing of the excitor's rotor

and additionally installing counter-balance bolt

the vibration of said unit has been lowered into a qualified range.