GAS TURBINES AXIAL COMPRESSOR NDE BY EDDY CURRENT PROBES TO DETECT CORROSION PITTING

摘要

Corrosion Pitting is a failure mode that appears in several cases in which there is a combination of Gas Turbines poor Inlet Filtration system (or wrong maintenance of it) and a particularly aggressive environment, characterized by presence of sulfides and chlorides. The corrosion pitting spots can cause crack initiation on the axial compressor blades and, with operation, go on propagating by HCF failure mechanism. This paper describes the application of a new type of Eddy Current probe, suitable to detect those very small spots on the first stage blades, avoiding to disassembly the gas turbine casings, in the very early stage of the corrosion phenomena. A specific experience on some LNG plants is reported.