Failure Analysis of Inlet Guide Vanes

The common failure modes of variable inlet guide vanes (VIGVs or IGVs) on industrial gas turbines are reviewed. These mechanisms include corrosion, cracking, and wear of the IGVs, their bushings and thrust washers. A new mechanism for IGV failure is described through a case history and metallurgical examination. High-cycle fatigue cracking in multiple IGV’s was found at a location different from the expected cracking location. The failure is caused by a combination of wear loss and galling of the IGV metal shafts against the polymer bushings, combined with deterioration of the polymer matrix. Finite element analysis is used to verify the loading mode, maximum stress location, and crack propagation direction.