How can I prevent lubrication problems of after stern tube bearing in shaft alignment design?


Shaft fatigue and shaft alignment

With the development of large ships, there has been an increasing number of shaft alignment related damage cases in recent years. Most of the cases are related to the lack of lubrication in the stern tube bearings, resulting in shaft fatigue or wiping damages. Based on this situation DNV GL has updated the shaft alignment related parts of the Rules. Based on this method, the minimum rotational speed giving hydrodynamic lubrication will be calculated. With this function the results calculated in Nauticus Shaft Alignment will not only satisfy for the static condition but also the running conditions. Accordingly, damages related to improper shaft alignment can be avoided in the design phase rather than ending with delays in delivery and potential repairs and off-hire.

In addition, Nauticus Shaft Alignment  provides a direct analysis function to calculate the oil film pressure and distribution inside the after stern tube bearing of the marine propulsion system. The method is based on DNV GL Maritime Advisory’s research and published on SNAME conference 2009 (performance of stern tube bearings under different lubrication and operating conditions). It calculates the minimum oil film thickness and maximum pressure and can be used as supplement to the minimum rotational speed result.

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