Impact of Thruster Failure On Mooring-assisted Dynamic Positioning System

Zhang, Feng (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wang, Lei (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Yan, Fang (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)

OnePetro 

ABSTRACT:

This paper is concerned with the effect of one thruster failure on the mooring-assisted dynamic positioning system of a semi-submersible platform. The mooring-assisted dynamic positioning system is composed of a class-3 dynamic positioning system and a catenary mooring system. By numerical simulations, the impacts of different thruster failure modes on the offset and power consumption of the platform are calculated and compared. Finally, some feasible ways are proposed to reduce the failure impact so as to improve positioning accuracy and reduce power consumption.



INTRODUCTION


Dynamic positioning system is widely used on the semi-submersibles in the exploration of ocean resources. Although it can help semi-submersibles to resist worse sea conditions and maintain a given position without the limitation of the water depth, they may lose its function when some failure modes happen. So as to improve the positioning accuracy and reduce energy consumption, mooring-assisted dynamic positioning system is developed on the basis of dynamic positioning system. Generally, the mooring-assisted dynamic positioning system is composed of a dynamic positioning system and a mooring system, in which the dynamic positioning system controls the vessel’s position and heading and the mooring system helps to resist parts of the external forces and reduce fuel consumption. According to some rules of classification society (DNV-OS-E301), the mooring-assisted dynamic positioning system is designed to have enough redundancy when the system failure, which may lead to serious economic consequences or even dangers to life. The study on mooring-assisted dynamic positioning system was first carried out in the 1970s based on model tests of dynamic positioning system. Sargent and Morgan (1974) proposed that the mooring-assisted dynamic positioning system would enhance the positioning accuracy and reduce cost. In the 1990s, NTNU has conducted a series of model tests of mooring-assisted dynamic positioning system.