FAILURE OF A CPP AT NO LOAD

2006-11-14

FAILURE OF A CPP AT NO LOAD

~by Herbert Roeser, TransMarine Propulsion Systems, Inc.

Synopsis

It is often assumed that failure of a mechanical system can occur only under loaded or overload conditions. This assumption is correct if one only considers a non-dynamic condition. In addition to the static loading most mechanical systems are also subjected to dynamic loading due to the fact that they are considered to be finite stiff structures and not infinite stiff structures.

In regards to the marine propulsion systems, one is mainly dealing with two principal sources of excitation, the main engine and the propeller and they are linked by an elastic shaft system. In addition, the whole propulsion system is supported in a flexible hull structure. The forms of vibration possible in these propulsion systems are very diverse but similar techniques are used to analyze the system behavior for each respective form of vibration. This paper shows that if certain operating parameters have not been considered and analyzed at the design stage of the vessel, it can lead to expensive failures when the vessel is in service.

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