Failure investigation of gear teeth fracture of seawater pump in a diesel engine

Abstract A failure investigation has been conducted on a transmission gear of a seawater pump used in a marine diesel engine. The fracture of the gear teeth took place in a test lab, when the engine ran about 100 h. The condition monitoring and fault diagnosis system (CMFDS) equipped on the engine captured some useful information, which was crucial clues to diagnose and locate the fault. The faulty gear was made from 17CrNiMo6 steel, and the tooth surface was carburized and quenched. The fault of gear fracture had never happened before in this type of seawater pump. By analysing the operation historical data of the engine, the possible source of the fault was proposed. After the machine was disassembled, the microstructure and chemical composition of the fractured teeth were examined. Then, mechanism of the gear engagement was analyzed through multibody dynamics simulation. Finally, the root causes for the failure were discussed based on above investigation, and the corresponding improvement measures were put forward.