To clear the faults occurred on a 600MW unit

such as large amplitude vibration and random fluctuation of high pressure rotor with critical speed and load

periodic fluctuation and amplitude increase of shaft bearing vibration that behind the generator rotor

diagnosis and trouble-shooting of vibration was conducted.Results show that

reasons causing the vibration are:non-smooth expansion of high pressure cylinder and carbon deposition on oil damper

dynamic and static friction between slip ring and carbon brush

and thermal unbalance of the generator rotor etc.Measurements like replacing the gaskets

increasing the pressure of bearing box from-450 Pa to-180 Pa

regulating the installation compactness of carbon brush and the field high-speed dynamic balance

can eliminate the vibration problems

and make the shaft system run normally.