Failure analysis of a gas turbine compressor

During the shut down period, a 32 MW gas turbine experienced a severe failure accompanied by a loud noise near its second natural frequency at 4200 rpm. After opening the turbine casing, it was revealed that the disks of stages 16 and 17 of the compressor had been fractured and all of the stationary and rotary blades of stages 14–18 of the compressor had been detached from the dovetail region of the disks. The degree of damage was such that repairing the compressor was not economical, and thus, the compressor was no longer able to be used. Diagnostic work was carried out using different finite element models and fractography analysis. Analysis showed that multiple cracks had been initiated in the interface of the disks and shaft by the fretting fatigue mechanism and had been propagated by fatigue mechanism. Finally, unexpected and/or excessive forces or impact loads had led to the final brittle fracture of the disks. Some recommendations are proposed for preventing similar failures in the future.