The calculation analysis and experimental study of blade fracture of a certain type of steam and static adjustable induced draft fan are carried out. Vibration signals and blade natural frequencies of fans at different speeds and openings are obtained through vibration tests and modal experiments. Performance curves of fans at different speeds are drawn according to the similarity theory

and the rotation-opening curves corresponding to the flow rate are obtained. The fan operation restricted zone is delimited by the stall line. The test results show that

when the rotation speed is constant

the amplitude of the blade passing frequency and its harmonic component increase with the stator blade opening. Combining with the modal experiment

it is found that the natural frequency of the blade and the blade passing frequency and its harmonic component coincide when the fan runs in the rotation speed range of 796～912 r/min

resulting in blade resonance. The fan should avoid running in the resonance speed range and avoid running in the speed restricted area.