Research on strength degradation of oil transmission pipeline by third-party damages

The integral strength of the pipeline is badly hurt by drilled holes. Whether the pipeline can work normally after being repaired is in concern. While it is hard to determine the strength degradation of the pipeline by field experiments, that is to say, what is the ultimate pressure that the damaged pipeline can bear after being repaired? Three segments of pipeline will be experimented in this paper; they were directly cut from pipelines. The first was cut from a pipeline which had been in service for about 30 years and the drilled holes had been repaired by welding hats; the second was cut from the same pipeline while the drilled holes had been repaired by welding sheet; the third was cut from a brand new pipeline. Hydraulic pressure tests were performed for these three segments respectively. The test method, test procedure and test results will be fully discussed. Furthermore, FEM analysis was performed for the first and the second segment and results were analyzed in this paper.