埋地管道外腐蚀致因事故树分析

土壤腐蚀是导致埋地输油气管道腐蚀失效的主要形式。由于土壤环境的复杂性和多样性,土壤介质对埋地金属管道的腐蚀电化学机理和过程相对复杂。文章简要阐述了埋地管道土壤电化学腐蚀机理:阴极过程主要是氧的还原,在阴极区域生成OH-离子;阳极过程主要为铁的氧化过程,氧化后的Fe2 离子与土壤发生水合作用。采用事故树分析对管道外腐蚀进行致因分析和结构重要度分析,得出了管道腐蚀事故主要与土壤腐蚀性和防腐层状况有关及重要程度。最后,提出了埋地管道土壤腐蚀防护措施和相关建议。

FAULT TREE ANALYSIS OF EXTERNAL FACTORS OF SOIL CORROSION FOR BURIED PIPELINE

The soil corrosion is a main form which results in corrosion failure of buried pipelines.Because of the complexity and variety of soil surroundings,the mechanism of electrochemical corrosion and process is complex correspondingly.This paper introduces the mechanism of electrochemical corrosion briefly.Oxygen is deoxidized and OH-ions are created in cathodic area;iron is oxidized and the products of Fe2 ions are hydrated with water from soil in anodic area.The corrosion factors and structural importance are analyzed by fault tree analysis(FTA),and then the soil corrosion factors and status of anti-corrosive coatings and structural importance are obtained for the reasons of corrosion on buried pipelines.Some measures and proposals are presented for soil anti-corrosive methods.