The Applied Research Of Submarine Pipeline Integrated Evaluation Technology

The inspection and risk assessment are important for evaluating reliability of submarine pipeline. The residual strength of pipelines corrupted must be evaluated so that the correct decisions can be making. All of these have important role in ensuring the safe and stable operation of submarine pipeline. This paper mainly content is using ANSYS software research corrosion the magnetic leakage field of corrosion based on 2-D and 3-D, evaluate the residual strength of submarine pipeline and analysis its stress state for risk assessment .The major contents are summarized as follows:1.The conclusions based on two-dimensional research of the magnetic leakage field of defects are as follows: The deeper of defects , the more of magnetic flux leakage signals; Through studying the distribution of magnetic flux leakage signals to judge the size of defect is reasonable, but still have great difficulty to achieve a accurately determination; The grearter of the lift-off value ,the less of the magnetic flux leakage signals are detected; Different shape defects have similar magnetic flux leakage signals, it is difficult to study defect shape and magnetic flux leakage signals relationship base on 2-D.2.Within three-dimensional method was used to study the magnetic leakage field of defect, we can get the major conclusions as follows:(1)The vector plot of 3-D leakage magnetic field can prove that the defects had a big impact on the magnetic leakage.The three dimensional shapes of defects have important influence on the intensity of magnetic flux leakage signal, The deeper of defects , the more of magnetic flux leakage signals.The strongest magnetic flux leakage signals is not took place in the center of defect, but in the both sides of the center.With the radius of defect change ,the trend of the magnetic flux leakage signal value in defect center point and maximum magnetic flux leakage signal value are different.(2)The article supplied the notion of minimum lift-off value, only when the lift-off value less than minimum value , the probe can detect valuable magnetic flux leakage signals; For smooth opening and the inner surface defect, the minimum lift-off value is related to defect opening area; For the defect which openings and the inner surface is not smooth, the minimum lift-off value is equal to the depth of defect; The three-dimensional shape of defect directly affect the of magnetic flux leakage signals, we can discriminate defect shape through the radial, axial and circumferential magnetic leakage field signal.3. Through the analysis of stress in corrosion pipeline,we found that under internal pressure ,the biggest radial and circumferential displacement of the pipeline take place in defect area ,but the biggest axial displacement take place in area around the defect on both sides,in other areas, the displacement is much smaller. The axial defect have more threaten on the safety of pipeline than the circumferential defect. Depth and width of the defect has greater impact on the stress of pipeline than length, the increases of their value will lead to the increase of stress; The results figure out by modified B31G method compared with ANSYS method is smaller; BZ26-2 submarine pipeline's qualitative and semi-quantitative risk assessment evaluation found that it is a medium risk pipeline.