Continuous shafting vibration fluctuation occurred on several large scale nuclear steam turbine generator units after being put into operation

with large fluctuation range and long period. It was speculated as Morton Effect which happened due to jamming of sealing pad in steam turbine generator unit

according to theoretical analysis and maintenance records. A simplified model was established to fit the vibration data

and the vibration components corresponding to the initial unbalanced mass and thermal variables were calculated. Analysis shows that

because the proportion of vibration component corresponding to thermal variable was small

the shaft system stability of the unit was not affected. By this new method

the vibration component corresponding to the initial unbalance mass of the rotor was quickly calculated and the vibration amplitude can be effectively reduced through the dynamic balance test. The correctness of the model has been verified by the field engineering practice in a nuclear power station.