| Currently, as the exploration and production of ocean oil and gas are developed to thedeep water, the positioning system is paid more attention. The mooring assisted dynamicpositioning system, which combines the advantages of the mooring system and dynamicsystem, would be more popular in the future.During the work condition, the mooring-assisted dynamic positioning system mayhave some failure modes, such as the control system breaking down, the thruster systemfailure, which will lead to serious position loss, or even dangers to the structure’s life.Therefore, a failure mode and effect analysis (FMEA) should be conducted to provide acomprehensive analysis to establish the important failure modes with regard to stationkeeping of the mooring-assisted dynamic positioning system.With a semi-submersible platform, this thesis is dedicated to explore the failure modeand effects analysis of the mooring-assisted dynamic positioning system. So there are fourparts in this paper.(1) Research on the mooring-assisted dynamic positioning system’s positioningcapability.In this part the the system’s positioning capability was calculated, and the results ofthe maiximum environment loads of the platform were worked out. The calculationfigures that, under the designed surrounding loads, the mooring-assisted dynamicpositioning system has the capability to stand the designed environment laods in everydirection. (2) Research on the failure modes of the mooring-assisted dynamic positioningsystemUnder the designed environmental condition, the numerical time domain simulationof the three failure modes were conducted in the thesis, and the comparisons betweenfailure modes and intact modes were making to evaluate the impact of different failuremodes and test whether the system was meeting the design requirement.(3) Research on the change of the thruster layout to affect the impact of thrusterfailure modesBased on tbe old system, the two new thruster systems were designed. This part willanalyse the effects of thruster failure modes on the platform’s offset and power utilizationof the three different thruster layout.(4) Research on the effect of the change of the forbidden angle of the thruster toreduce the impact of thruster failure modesIn this thesis, due to different thruster failure modes, changing the forbidden angleaccordingly and then taking numerical analysis and evaluating the influence of thesemethods to the whole positioning system.By time domain simulation, the paper does a comparison on many failure modes ofthe mooring-assisted dynamic positioning system for the deep water platform. Theresearch results in this paper will give a reference to the design and construction themooring-assisted dynamic positioning system in the future and the work is beneficial toimprove the technology of designing the mooring-assisted dynamic positioning system. |
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