某天然气长输工程外腐蚀失效分析

ANALYSIS ON EXTERNAL CORROSION FAILURE OF NATURAL GAS LONG-DISTANCE PIPELINE

文章针对油气长输管道易发生腐蚀失效的问题,对某天然气长输工程中管道腐蚀失效区域进行宏观和扫描电镜观察以及腐蚀产物能谱分析;对管子进行金相和化学成分分析、力学性能检测;并对管道周围敷设土壤进行分析。分析结果表明,管子外部机械损伤首先导致管壁产生极大的损伤缺陷和壁厚减薄,同时造成管道外防腐层的破损;其二,该损伤点直接暴露在土壤电解质环境中,进一步发生化学或电化学腐蚀,直至发生局部壁厚减薄失效。上述分析揭示了管道安装过程中的机械损伤和运行期间的腐蚀作用共同诱发管道失效的一般现象。文章针对失效原因,提出了在采购、施工安装、运行维护阶段的相关建议措施,对相似问题的处理具有一定的参考价值。

Aiming at the problem of oil and gas long-distance pipeline being prone to corrosion failure,this paper conducted macroscopic and corrosion product analysis,metallographic analysis,chemical analysis,mechanical property testing,hardness determination,scanning electron microscopy and energy spectrum testing of the failure area and surrounding soil analysis of the natural gas long-distance pipeline.The results show that external mechanical damage first led to great damage defects and thickness thinning of the pipe wall,and also caused breakage of the external anti-corrosion coating of the pipe.Then the damage site was directly exposed to the electrolyte environment of the soil,and chemical or electrochemical corrosion occurred in the damaged site until the occurrence of the pipeline failure due to local wall thickness reduction.The above analysis demonstrates the general phenomenon of pipeline failure induced by mechanical damage during installation and subsequent corrosion during operation.According to the failure causes,this paper puts forward relevant recommendations and measures for the procurement,construction and installation,and operation and maintenance stages,which are of certain reference value for the handling of similar problems.