The blade of axial induced draft fan in a 600 MW unit fractured.To find out the reasons

particular investigations on blade fracture failure site

operation files and history data of the axial induced draft fan were performed.The physical and chemical tests and fracture analysis for the blade were implemented.The centrifugal stress and the vibration characteristics of the blade were analyzed using the finite element method.The results show that

the physical and chemical performance of the blade material satisfied the requirement

the static strength and vibration characteristics of the blade met the design standard

the major reason for the blade fracture was poor quality or improper process of the coating

which made micro cracks exist on the blade surface before or during the unit operation

thus high cycle fatigue fracture occurred under the action of centrifugal stress and flow stress.