Study On The Online Monitoring Method Of Marine Shafting Alignment

The quality of propulsion shafting alignment has great influence on ensuring the normal operation of the main propulsion equipment and reducing harmful hull vibration. Excessive additional loads will appear if the shafting alignment does not satisfy the restricted conditions after installation, or the bearing’s offsets change owing to external factors when the shaft system operating.At present, the shafting alignment calculation method has been well developed, and it can determine the correct position of every bearing in accordance with the provisions of bearing loads, stress and slope etc. In order to verify the quality of shafting alignment, jack-up method is usually taken to measure the loads of intermediate bearing after the bearing has been adjusted.Based on the shaft testing platform, the method of online monitoring of the state of marine shafting alignment is studied in this paper. And the research work of the online shafting alignment monitoring system is presented in three parts. These are as follows:Firstly, Transfer Matrix method was chosen to analyze the state of shaft in this paper by comparation with other three kinds of shafting alignment calculation methods.. The online monitoring method of marine shafting alignment and the way of cross section selection are described in this paper.. MATLAB engineering calculation software is used to analyse the results simply and intuitively and to draw the state diagram of marine shafting.Secondly, the static bending moment of the shaft has been measured by strain electric method with the wireless telemetry system. Therefore the actual shaft state can be obtained. Moreover, the loads at tail bearing and intermediate bearing are measured by revised jack-up method which is used to verify the results of wireless telemetry.Finally, the impropriety of the alignment of shaft testing platform has been analyzed, and the modified method is offered to achieve status monitoring of the ship shafting system.In addition, the dynamic bending moment of shaft was analyzed in this paper. It can be concluded that it is feasibility to on-line monitor the state of shaft during operation. And it will be helpful and useful for the further studies of the dynamic alignment-of marine shafting system.