A novel liquid pipeline internal corrosion direct evaluation technology and the application on the water pipeline

It is impossible to conduct internal corrosion inspections on water pipelines due to the small diameter and low pressure. Therefore, a novel internal corrosion direct evaluation method should be established to determine the internal corrosion status of water pipelines. In this paper, the CN shale gas backflow liquid pipeline is taken as the research object, and the water sample composition and corrosion rate are tested. Based on this, the main controlling factors for corrosion are determined via the grey relational analysis method. Combined with corrosion product analysis, the internal corrosion mechanism is clarified. The non -contact magnetic detection technology is applied to detect magnetic anomaly pipe segments. Combined with water samples corrosion testing results and geographical feature points along the target pipeline, the internal corrosion sensitive pipe segment is determined and excavated for inspection. Finally, the internal corrosion status of the target water pipeline is assessed. The results show the synergistic corrosion of SRB, O2, and Cl- occurs in the pipeline, where the SRB content is the main controlling factor. The defect depths of the excavated corrosion -sensitive pipe segments are 0.40 mm - 1.47 mm, and the corresponding corrosion rate is 0.078 mm/a - 0.490 mm/a. The residual strength of the CN pipeline meets the strength requirement, and the reevaluation cycle is 4 years, which should be repaired for use.