For a typical arrangement of a two-stroke diesel engine installation, the engine is directly coupled to the propeller by one or more intermediate shafts and the propeller shaft. Usually these systems have two stern tube bearings and one or more intermediate bearings. Insufficiently loaded bearings may be damaged. For improving the reliability it is essential to arrange the bearings of the shafting system in such a way, that all bearings are well loaded but the interaction between them is as small as possible. The influence of the shaft arrangement on the main bearings has also to be considered. The load distribution is influenced by the stiffness of the shafting system, the weight, the initial bearing offset and the draught of the vessel, which leads to a static deformation of the ship hull. By rotating the crankshaft the vertical bending stiffness of the crankshaft changes and due to this there is a variation of static main bearing load over one revolution. Practical methods to check and validate the alignment in a given installation are web deflection and jack load measurements, sometimes also strain gauge measurements. This paper introduces a program package developed by Wärtsilä which provides a three-dimensional model of the shafting for the calculation of coupled vibrations, alignment and whirling in such a ship propulsion plant. It is used for new alignment as well as for reverse offset calculations based on measured web deflection, jack load and bending moment. This is useful to define countermeasures in case of a bad alignment. The analysis of measured data is sometimes nearly impossible without such an analysis. This paper shows some aspects for new alignment and an example for the practical use of reverse offset calculation.
The importance of alignment for an engine builder
2007
10 Seiten, 18 Bilder, 2 Tabellen, 6 Quellen
Conference paper
Storage medium
English
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