Direct Assessment Methodology of Internal Corrosion in a Submarine Multiphase Flow Pipeline

A submarine multiphase flow mixture transport pipeline could not be detected by internal inspection within more than 20 years after its service due to pipeline structure. In order to understand the internal corrosion status of the pipeline, internal corrosion evaluation of submarine pipeline was carried out according to NACE SP0116-2016 standard. According to the actual working conditions of the submarine pipeline, appropriate multiphase flow model and corrosion prediction model were selected to form a model suitable for the evaluation of the corrosion in multiphase flow submarine pipeline. High-risk positions and corrosion rates of the submarine pipeline were predicted by this model. At the same time, the internal corrosion rates of the submarine pipeline were obtained through indoor simulation experiments to verify the reliability of the evaluation results. The re-evaluation period of the pipeline was determined by calculating the remaining strength and remaining life of the pipeline based on the predicted wall thickness loss. Based on the evaluation results, suggestions for pipeline integrity management measures were proposed to improve the safety of submarine pipelines.