Analysis of a diesel generator crankshaft failure

This paper analyses a catastrophic crankshaft failure of a four-stroke 18 V diesel engine of a power plant for electrical generation when running at a nominal speed of 1500 rpm. The rated power of the engine was 1.5 MW, and before failure it had accumulated 20,000 h in service operating mainly at full load. The fracture occurred in the web between the 2nd journal and the 2nd crankpin. The mechanical properties of the crankshaft including tensile properties and surface hardness (HV1) were evaluated. Fractographic studies show that fatigue is the dominant mechanism of crankshaft failure, where the beach marks can be clearly identified. A thin and very hard zone was discovered in the template surface close to the fracture initiation point, which suggests that this was the origin of the fatigue fracture. A finite element model of the crankshaft has predicted that the most heavily loaded areas match the fractured zone.