Failure analysis of an operator shaft in a marine flow control valve

摘要

An operator shaft in a marine flow control valve installed in 1997 in a power plant failed during operation in 2009. We conducted a failure analysis on the damaged operator shaft. The results indicated that deep pits caused by pitting corrosion and intergranular corrosion acted as a notch. From the pits, corrosion fatigue by torsional stress progressed in a transgranulary into the matrix. Therefore, the operator shaft failed before the end of its normal usage life.