Torsional Vibrations on a Hopper Dredger Due to Transient Conditions

Abstract

Torsional vibrations are known to be a major threat to the drive line of every ship. While classification societies demand a thorough analysis of the regime behavior, the transient behavior is not studied. Transient loads involve among others starting/stopping the engine, engaging/disengaging clutches, altering the vessel’s speed and changing the pitch of the propeller. These high load changes are known to be a source of severe damage to gear boxes and flexible couplings. Further more, they tend to disturb the interaction between the mass-elastic system and the speed controller (governor instability). In this article, the different transient loads are described in detail for the specific case of a trailing suction hopper dredger. The focus lies on the engaging and disengaging behavior of the pump clutch. The different factors contributing to this transient load and their influence are explained without the use of a complex simulation model.