Abstract: This paper systematically investigated the moving blade fracture in a fluid catalytic cracking unit flue gas turbine through comprehensive failure analysis approaches including material recertification, metallurgical analysis, scanning electron microscopy (SEM), strength calculation, and nondestructive testing (NDT). It is found from the analysis that the safety margin between the intrinsic frequency and the excitation frequency resonance of the moving blade is less than 10%; the machining accuracy is insufficient; and the minor fouling causes the rubbing of blade tip and so on. Aiming at the above problems, measures such as optimizing the design of highstrength twisted composite moving blades, enhancing shot peening hardening of the tenon teeth, eliminating stress concentration, performing finishing treatment on the shrouds, controlling the quality of raw material V and catalysts, and optimizing operational performance are taken to effectively ensure the longterm safe operation of the flue gas turbines.

Key words: flue gas turbine, moving blades, fracture, failure analysis