Study On Durability Of Pipeline Based On Route Sureveying Of Subsea Pipeline

With the continuous development of marine economy and port economy, subsea pipelines widely used in different industries. For instance, the sewage disposal in coastal ports and the oil and gas transmission in offshore oil industry. The durability research highlights its significance when it comes to ensuring the long-term and stable use of subsea pipelines.The pipelines need to meet the design requirements in terms of structure and strength for the sake of durability. Moreover, the external environment also plays an important role. Therefore, this thesis embarks from marine survey in pipe routing area, aiming to analyze the influence of sea conditions made on pipeline durability. At the same time, it also makes a further research on the two most common pipeline failure forms in specific sea conditions to put forward reasonable measures for improving pipeline durability.(1) Taking a specific pipeline routing survey project as an example, the author combines with his personal experiences to introduce the implementation methods concerning routing areas sea survey. Based on the survey results, the thesis attempts to analyze the geological hazards status, the tendency of sediment movement and its erosion and deposition, and the corrosive environment in routing areas as well as study the influence of the sea conditions in routing areas to the durability of the pipelines.(2) In-depth studies have been conducted on the two most common pipeline failure forms in sea, including corrosion failure and fatigue failure caused by pipeline suspension. This thesis analyzes the mechanism and causes of subsea pipelines corrosion, discusses deeply about the various reasons for pipeline corrosion as well as corresponding anti-corrosion measures and carries out fatigue analysis on mechanism of the production of vortex-induced vibration and spanning pipelines. Based on the DNV OS F101 method, the allowing span length of spanning pipelines under vortex-induced vibration and their remaining life are analyzed, and the measures and precautions for the subsea pipelines' spanning failure due to different causes are discussed.