In view of the problem of the abnormal vibration of the high and medium pressure rotor No.1 bearing of a 350 MW steam turbine unit under operating conditions

it is analyzed that the shaft vibration at a fixed speed of 3 000 r/min and load is mainly based on the forced vibration of the fundamental frequency.The main reasons are bearing wear and looseness

the existence of steam flow induced vibration and rotor mass imbalance.The methods were proposed including improving bearing stability by adopting high and medium pressure rotor dynamic balance weight and adjusting bearing tightness and clearance

adjusting the valve sequence of high pressure regulating valve and changing the steam inlet method of the unit

that provide reference for similar problem of same type units.