After flow reformation of a supercritical 630 MW unit in a power plant

the abnormal phenomena of large vibration

large amplitude fluctuation and large low-frequency component are analyzed in the operation of sequence valve. By analyzing the spectroscopic characteristics of the vibration diagnosis system of the steam turbine

the failure are judged as the random vibration caused by the rough shaft surface

the light bearing load and the residual steam flow force. Through changing the position of vibration probe

increasing the bearing load and optimizing the valve open sequence and other methods

the vibration amplitude is eventually reduced to the acceptable range. This method in this study has certain referential significance for fault diagnosis and treatment of the same type units.