Failure Pressure Analysis And Calculation Of Submarine Pipeline Considering Corrosion Effect

Submarine pipeline is an important transportation carrier for the development of marine oil and gas resources.The submarine pipeline has been used in the complex marine environment for a long time,so the risk of pipeline corrosion is inevitable.The corrosion defects make the wall thickness of the pipeline thinned locally,the bearing capacity of the pipeline decreased,and the pipeline is prone to leakage,fracture and other failure accidents.Once the oil and gas leakage accident occurs in the submarine pipeline,it will not only affect the transportation of oil and gas and bring serious economic losses to the country and society,but also cause serious secondary disasters to the local marine ecological environment.Therefore,the failure pressure analysis of submarine pipelines with corrosion defects has always been one of the main problems in the transportation safety of oil and gas pipelines.Therefore,this paper studies the failure process and failure pressure calculation and evaluation of submarine pipelines with corrosion defects.The specific research contents and results are as follows:(1)Based on the results of full-scale blasting test of existing corroded pipelines,a nonlinear finite element model of submarine pipelines with corroded defects is established,and the feasibility and correctness of the finite element model are verified based on the experimental data.(2)The calculation formula of failure pressure of single corrosion defect Pipeline Considering the circumferential width of corrosion defect is established.The geometric size of corrosion defects is one of the main reasons that affect the calculation of pipeline failure pressure.The axial length and radial depth of defects have a great influence on the pipeline failure pressure.The circumferential width of defects has a small influence on the pipeline failure pressure,but it can not be ignored.In this regard,the system analyzes the influence of the geometrical dimensions of corrosion defects on the failure pressure of pipelines with different strength grades,and establishes a new calculation formula for pipeline failure pressure,which improves the accuracy of calculation results.(3)The influence of geometric dimension of corrosion defect on failure pressure and interaction between defects of double corrosion defect pipeline is analyzed.The failure process of the axial short corrosion defect and the axial long corrosion defect pipeline is different.With the change of the axial length of the defect,the critical distance of the disappearance of the interaction between the defects changes.The radial depth of the corrosion defect can affect the interaction between the defects.With the increase of the radial depth,the stronger the interaction between the defects,the greater the impact on the failure pressure of the pipeline.(4)This paper studies the influence of complex "?" overlapping corrosion defects on the interaction between defects,and establishes the failure pressure calculation formula of "ten" overlapping corrosion defects considering multiple corrosion effects.Based on the concept of relative coefficient,the influence of geometric size of overlapping defects on the interaction between defects and the failure pressure of pipeline is analyzed.It is determined that the axial length ratio and depth ratio of corrosion defects have great influence on the failure pressure of pipeline.With the increase of depth ratio,the failure pressure of pipeline decreases linearly.