Propeller root cavitation problems can be among the most complex to solve. In this region, along with tip vortex dynamics, rigorous mathematical analysis is currently of little assistance for design or analysis purposes. In some cases, when scant attention has been paid to the propeller design environment or where ship layout difficulties have arisen and high shaft angles or a poor choice of advance angle have resulted, erosion problems can occur which are difficult to resolve.

The severe action of the conrod caused failure of the bottom end arrangement. Here can be seen that at least one of the cap bolts has failed and that the cap has several hammer blow indentations.

This led to failure of both the effect unit and also through loss of lubrication the adjacent unit mounted on the same pin. Shown below are the two bearing shells. In addition damage is shown to the pin in the form of a deep indentation. This alone would have cuased the crankshaft to be scrapped as too great a reduction in diameter would have been required to restore the running surface. There was also a raised section on the opposite side caused by transfer of material either from the shell or con rod.  Several fractures occured as well as material seperation.

Course of events
The ship was alongside in port when the main engine was started, and the oil mist detector gave a warning alarm. When opening up the crank case a hot crankpin bearing was found. The crankshaft was found to be seriously damaged in way of one crankpin, causing the vessel to be put off hire for more than a month before resuming operation.

Infomarine On-Line Technical Library

File	Description	File size
CASUALTY_INF-NO5DECEMBER_2007[1].pdf	Probable cause : The main medium speed diesel engine is elastically mounted by using rubber mounts. Thus all cooling water, fuel oil and lubricat- Information from DNV to the maritime industry No. 5 December 2007	89 Kb