With Remaining Life Prediction Method Of Corrosion Defects In Pipelines

Long-distanced pipeline is the most econoimic and express means of transportation of oil nowadays. With the development of oil industry, the length of pipeline is increasing at a great speed. Pipelines are buried underground for decades, they can unavoidably be corroded due to the corrosive environments around them. This problem becomes worse in pipelines that have a long serving time. Corrosion of pipeline has a great effect on the safety and economic benefits of pipeline administrators. Launching a research of the remaining life of corrosive pipeline will improve the ability to predict the potential dangerous sections, which is meaningful to reliable management and taking predictable maintenance measures of pipeline.Based on extensive collecting information and investigation in oil field, the writer analyses the corrosion types, mechanisms and crrosion effect factors of long-distance transportation pipeline. The aim of predicting the remaining life of pipeline is to avoid blind maintenance and save maintenance costs. The basic thought of predicting the remaining life of pipeline, key points that affect the prediction, the emphasis should be laid during prediction and predicting solutions are described. The relative remaining strength of the prediction of the remaining life of pipeline is analysed, pointing out the prediction shoule be based on meeting the remaining strength's needs. This paper analyses the internal pressure along the pipeline. From the explosion equation the allowed minimum residual wall thick is determined. The prediction models based on corrosion rate and extreme value theory are constructed. The corrosion rate can be decided by gray theory, indoor buried sample measures, multiple corrosion inspection data, or on-scene buried sample measures. Fully depending on the on-spot corrosion inspection data, and from the point of view of convenience and suitability, the models of prediction of the remaining life of pipeline are developed, based on two corrosion inspection data and three or more corrosion inspection data. Considering many random factors that affect the determination of minimumresidual wall thick, the minimum value should have a range, so that the remaining life of corrosive pipeline should also have a range. The reliability or probability of specific remaining life can be calculated by the model of interference between residual wall thickness and allowed minimum residual wall thickness. The remaining life prediction model based on electrochemical corrosion-rate is analysed. In the end, the computer program for predicting the remaining life of corrosion pipeline is developed.