Failure analysis of an axial compressor first row rotating blades

The application of frame-type gas turbine engines is increasing in power plants and in the gas and oil industries. Statistically, there has been an increased rate of a common failure on the first row compressor blades of these engines. Studies have shown that there is a fundamental problem on the first stage rotating blade, which causes an unexpected fracture in one blade. The separated blade can cause violent effect that will destroy the compressor rows entirely. This paper addresses categorized tests and analyses of the failure events of a frame-type gas turbine engine. The results showed that the source of initial cracks on the blade was corrosion and pitting on the surface of the blade feather, and crack propagation was controlled via a high cycle fatigue process. A chemical analysis from the crack origins revealed the presence of abnormal elements such as Cl, Na, F, and S. Because of humidity in the coastal area and the presence of NaCl and H2S in the atmosphere of plant sites, the partial presence of corrosive gas was sufficient to create pitting on the compressor blade surfaces. Hence, a large part of fatigue, including crack nucleation and initiation, were eliminated by the creation of surface pitting. The fatigue phenomenon entered the second stage of fatigue directly. When the crack reached critical size, the centrifugal force caused a final fracture in the blade feather. A finite element analysis showed high stress localized at 1/3rd the height of the blade, which is in good agreement with the high density pitted area on the blade pressure side.