A Case Study for the Resonance of Marine Propulsion Shaft System Excited by Diesel Engine

The propulsion system which applies diesel engine with reduction gear as prime mover generally installs elastic coupling between engine and intermediate shaft. This coupling can isolate the vibratory torque excited by diesel engine, or excess hydraulic variation of the propeller occurring due to external impact. Hence, diesel engine and the reduction gear can be operated safely by adapting the elastic coupling to the system. In this paper, a case is presented wherein the elastic coupling for a skimmer vessel was repeatedly damaged by unknown vibration origin during sea trial. The authors analyzed the possibilities and causes of the elastic coupling failure thru global vibration measurement and past incident investigation. Applied countermeasures are reviewed and an integrated flexible coupling design is presented.