Safety Assessment Methods Of Corroded Submarine Pipeline

Submarine pipeline is the lifeline of offshore oil.However,ever since the submarine pipeline has been put into operation,it has brought a nonnegligible and serious threat to economic property,personnel safety and ecological environment.According to the statistics of the accident,corrosion is one of the main reasons for submarine pipeline failure.In this paper,a variety of analytical methods and tools are used to assess the safety of corroded submarine pipeline,in order to ensure the safe operation of submarine pipeline.The paper puts forward some improvement measures and suggestions for exsting problems about assessment safety methods of corroded submarine pipline,including three aspects:the first,the failure probability model of submarine pipeline is established by the data of submarine pipeline accidents at home and abroad;the second,the residual strength model of single and double corroded pipeline is established repectively by ANSYS software;the third,the residual life model of corroded submarine pipeline is established by BP neural network.Based on the data of the domestic and foreign submarine pipeline accidents,the fault tree of submarine pipeline failure is established after the cause of accidents and other risks are classified.And the failure probability of the fault tree caused by corrosion is analyzed.By the expert scoring method based on AHP and fuzzy mathematics method,the failure probability calculation model is obtained.In order to convenience and simplification,the paper also proposes a 3 scale analytic hierarchy process,and verifies its feasibility in solving this problem.Based on the plastic failure criterion and using ANSYS software,the residual strength model of 3D corroded submarine pipeline is established by nonlinear method,and the failure pressure of pipeline under different conditions is obtained.In the case of single corrosion,the main parameters affecting the failure pressure are the relative depth d/t,the relative length L/d and the relative circumferential angle?/?.The simulation results show that the influence of the relative circumferential angle can be ignored when analyzing the general engineering problems.Based on the theory of stiffened plate and the 1stOpt software,the formula for calculating the failure pressure of corroded pipeline is obtained.In the case of double corrosion,there is little interaction between double ring corrosion.Correspondingly,the axial double corrosion interaction is obvious.When L_d<120mm,there is the logarithmic relationship between failure pressure and axial spacing.When L_d>120mm,the interaction disappears.The BP neural network is constructed by the parameters which influence the corrosion of submarine pipeline,and a good network model is trained by MATLAB to predict the remaining life of submarine pipeline.Futherly,the BP neural network is improved by genetic algorithm,and the prediction model with higher accuracy is obtained.