CORROSION DEFECTS AND RELIABILITY ANALYSIS OFX80 STEEL MATERIAL OF LONG-DISTANCE OILANDGAS PIPELINE

摘要

People's life and industrial activities need to be realized by energy, and the exploitation of oil and gas by human beings has gradually shifted from land to ocean. The seabed has an extremely complex envi- ronment, and the pipeline is hit and even corroded by the waves for a long time. When corrosion occurs, the pipeline will not have the initial strength, result- ing in the loss of function of the pipeline and the pipeline laid on the seabed cannot assist the transpor- tation of oil and gas. When submarine oil and gas pipelines are corroded by seawater, the strength of the pipeline will be reduced. Therefore, it is particu- larly meaningful to study the highest bearing strength, probability of invalidity and principles of pipelines corroded by seawater. The statistical test method is used to draw samples non-directionally, and then the probability of failure and the remaining service life of the submarine pipeline after corrosion under internal pressure are calculated. According to the data distribution of the submarine oil and gaspipeline wall thickness, corroded length and rate, and cross-sectional diameter, the influence of corro-sion defect factors, operating pressure, working time and variation index on the failure probability of sub- marine oil and gas pipelines is analyzed. According to the calculation results, it can be known that the depth and length of corrosion defects and the in- crease of operating pressure will accelerate the fail- ure of the pipeline. When the corrosion depth in- creases, the probability of failure gradually increases, from the lowest value of7.0x10-6 to 2.2x10-2, and theincrease rate is relatively rapid. When the length of corrosion increases, the probability of failure gradu- ally increases from the lowest value of 4.0x 10-6 to 2.5x10-3. With the increase of the variation index of corrosion defect depth and length, operating pressure, ete., the probability of failure will increase. The longer the working time of the pipeline, the smaller the impact on the probability of failure.