Analysis of a failed Detroit Diesel series 149 generator

•A two-stroke diesel generator failed after only nine months in service.•Significant damage to turbocharger and components from one cylinder were discovered.•Investigation revealed evidence of exhaust valve erosion–corrosion (‘guttering’).•Engine temperature logs corroborate valve guttering as the cause of failure.

Several components of a diesel generator failed dramatically after only nine months in service. Operators noticed the generator, a two-stroke Detroit Diesel model 16V149TIB, producing abnormal noises and smoke. Upon inspection the piston crown, cylinder head, fuel injector, and exhaust valves from the No. 1 cylinder were found to be extremely damaged, as was the exhaust turbine from the turbocharger assembly. Examinations of the recovered parts were conducted through visual and chemical analysis, fractography, and metallography. Various fracture mechanisms, such as thermal cracking, intergranular fracture, and high-cycle fatigue, were observed for the different materials and parts involved. It was determined that the damage sustained by the engine could be explained as the result of severe and undetected erosion–corrosion (‘guttering’) of one of the No. 1 cylinder exhaust valves, which caused the valve head to fracture and enter the combustion chamber. Possible causes of this valve guttering are discussed, and recommendations are offered to help avoid similar catastrophic failures in the future.