Study On Detecting Antisepsis State Of Submarine Pipeline

It is known that hundreds of submarine pipelines are used in the world, which are undertaken the transmission of the rude oil, natural gas, seawater, freshwater and sewage. With the increase of the number of the pipelines and the life span, many accidents happened, therefore, many statistical analyses are carried out concerning to the operational process of pipelines. It is believed that the corrosion of the pipe is the critical factors influencing the reliability and the life span of the pipeline system.The overwhelming majority of long pipelines in China are adopted by the anti-corrosion coating and cathodic protection, which are supplemented each other. The intact anti-corrosion coating can enhance the efficiency of the cathodic protection, which in turn can provide cathodically protecting current to the damage points of the coating protected by the cathodic polarization. Thus one of these two aspects is unsuitable can make the anti-corrosion system failure.In this paper, based on the investigation of the cathodic protection electric field of the marine pipelines, the feasible appraisal method for the working condition of the anti-corrosion coating and cathodic protection of the submarine pipelines is obtained. Concerning the above mentioned aspects, the main work in the thesis is outlined as follows.Firstly, based on the literature review in this research field, the significance of the study is presented. Due to the consideration of the anti-corrosion system of the pipelines, a brief introduction of the corrosion and protection of the submarine pipelines is introduced in Chapter 1, which consists of the corrosion principle, the corrosion morphology, influencing factors; the type and assessing parameters of the anti-corrosion coating; and the principle and estimating parameters of the cathodic protection. Chapter 2 is the main part of the thesis, which the numerical simulation for the cathodic protecting electric field of the submarine pipelines is processed via using the boundary element method, and the inherent relationships of the electric field and sacrificial anodes working condition, and the ageing condition of anti-corrosion coating and other factors in the surroundings, are studied. Consequently, a complete cathodic protection electric field versus influencing factors database has been set up. Whereas Chapter 3 implements the projection from the environmental potential distribution to the coating damage rates, and the residual weight of sacrificial anodes to protection current density by applying the numerical samples calculated from the BP neural network. In the end, an appraisal approach is constructed on the basis of the anti-corrosion condition for the submarine pipelines measured from the environmental electric field, and the relevant software interface is developed.