工业纯碱生产线降膜管损坏失效分析

Failure analysis of falling film tube in industrial sodium hydroxide production line

国内某工业纯碱生产厂降膜管在使用半年后发现漏液现象,无法正常搜集工业纯碱。为探究其降膜管失效原因,先后通过体视显微镜、扫描电子显微镜(SEM)、金相显微镜(OM)和电子探针(EPMA)对失效件进行了低倍宏观形貌、表面形貌、金相组织及成分分析等。结果表明:该降膜管失效的原因是外壁焊接区因污染元素S的存在发生了应力型腐蚀开裂,导致降膜管焊接区部分产生贯通性裂纹,最终碱液渗漏。

The liquid leakage was observed for one falling film tube in an industrial sodium hydroxide plant in China after service for half a year.It was unable to collect industrial sodium carbonate normally.In order to explore the failure reason of the falling film tube,the low magnification macroscopic morphology observation,surface morphology analysis,metallographic structure analysis and composition analysis of the failed parts were conducted by stereo microscope,scanning electron microscope(SEM),metallographic microscope(OM) and electron probe microanalysis(EPMA).The results showed that the failure of the falling film tube was caused by the stress corrosion cracking in the outer wall welding area due to the presence of the pollution element sulfur,which led to the through cracks in the welding area of the falling film tube.Finally,the leakage of soda solution was caused.