Buried Steel Gas Pipeline External Corrosion Direct Assessment And Suitability Evaluation Research

Pipeline is more and more widely used for its advantages such as large capacity,high efficiency, low cost, fully enclosed, strong environmental adaptability and easymanagement for transporting gas. However, because the steel gas pipeline was buried inthe complex environment for a long time, and according to the problems such as theincreasing of service year of the pipeline, the destruction of the pipeline external coating, andthen leads to the corrosion of steel pipeline body itself, which could produces potentialsafety hazard. The safety of the gas pipeline transportation relates to the security ofpeople’s life and property, the economic efficiency of an enterprise, the steadydevelopment of national economy as well as the stability and harmony of the society. Soin order to ensure the gas pipeline runs safely, the research and analysis of the majorfactors that cause external corrosion of the buried steel gas pipeline, creating the modelof pipeline external corrosion direct assessment, evaluating the applicability ofcorrosion points is urgently needed．Based on the study of large quantity of documents at home and abroad, in thescientific and operational conditions, in order to comprehensively grasp the main factors influencingthe pipeline external corrosion, The author participated in field-testing for buried steel gaspipeline and collected test data. Through the analysis of the data, the system of pipelineexternal corrosion direct assessment model is more perfectly constructed. The main determinedfactors affecting the pipeline external corrosion was damage degree of anticorrosivecoating, pipeline operating life, soil resistivity, soil PH, pipe-to-soil potential and so on.In the system of pipeline external corrosion direct assessment model, there aremany factors that were fuzzy uncertainly. In order to be able to accurately describe theseuncertainty factors, and then introducing mathematical thought and method. SPSS19.0software was employed to reinforce the main influencing factors of correlation analysis,variance analysis and the analysis of the factors, through quantitative analysis method ofpipeline external corrosion situation evaluation, establishes the buried steel gas pipelineexternal corrosion direct assessment model.The corrosion produced inevitably low the pipeline residual strength and bearingcapacity, reduced the period length of pipeline corrosion inspection and maintenance. Inorder to make the pipeline gas supply system can run normally, in pipeline externalcorrosion direct assessment model, and on the basis of predecessors’ research, The author evaluated residual strength and predicted residual life for corrosion points.The conclusions of this paper mainly have three: First, the main factors affectingpipeline external corrosion is damage degree of anticorrosive coating and pipelineoperating life, but other factors (soil resistivity, soil pH, pipe-to-soil potential,etc) alsocannot be ignored. Second, he buried steel gas pipeline external corrosion directassessment model was established. The last, the paper presented a method aboutsuitability evaluation of pitting corrosion.