某公司尿素装置蒸发系统入口管道在服役过程中发生泄漏,采用宏观观察、渗透检测、化学成分分析、金相检验、扫描电镜和能谱分析等方法分析了其泄漏原因。结果表明:管外壁保温层中含氯离子,雨水的浸湿使管壁与导热泥的缝隙中形成了潮湿环境,干湿交替环境导致氯离子在管壁富集,引起管壁点腐蚀和氯化物应力腐蚀开裂。

Leakage occurred in the inlet pipeline of the evaporation system of a urea units during service. The cause of leakage was analyzed by means of macroscopic observation, penetrant testing, chemical composition analysis, metallographic examination,scanning electron microscope and energy spectrum analysis. The results show that the insulation layer of the outer wall of the pipe contained chloride ions. Due to the wetting of rainwater, a humid environment was formed in the gap between the pipe wall and the heat conducting mud. The dry-wet alternating environment led to the enrichment of chloride ions in the pipe wall, caused pitting corrosion and chloride stress corrosion cracking.