Failure analysis of a petrochemical plant reducing gear

This study aims to investigate the cause of failure of an 845 mm external diameter reducing gear that operated during 30 months in a petrochemical plant. The failure analysis procedure included material characterisation (microstructure, chemical composition and microhardness), fracture surface evaluation, and stress distribution by finite elements on critical regions of the gear. Fracture mechanics and fatigue crack growth were also used to develop a da/dN–ΔK curve and then determine the gear material crack growth resistance. Results indicate that the gear was not properly manufactured and failure occurred as a result of a fatigue process facilitated by a manufacturing defect.