The sudden rise of high-pressure rotor vibration of a 300 MW air-cooled unit manufactured from Dongfang Steam Turbine Works

and being equipped in one thermal power plant

has been analysed from the typical fault properties of steam flow excited vibration.It is believed that the cause leading to sudden rise of vibration is the steam flow excited force

which makes the steady-state of bearing no.2 to be change

resulting in stability reduction of the rotor.Some corresponding disposal measures have been given

after implementation

the problem of vibration fault has been resolved.