通过宏观和微观分析等手段, 对某QT400-18球墨铸铁煤气管道泄漏原因进行了分析。由宏观分析可知管道腐蚀泄漏是由局部腐蚀穿孔所致, 腐蚀从内壁开始, 由内向外直至穿孔泄漏; 微观分析没有观察到微裂纹等缺陷, 成分分析可知管道内壁腐蚀产物中含有大量硫元素, 说明管道腐蚀泄漏的产生与管内介质中含有硫元素有关。综合分析结果表明: 由于所输送煤气中含硫杂质超标, 与管内壁冷凝水共同作用产生局部电化学腐蚀, 从而导致了煤气管道的局部穿孔泄漏。建议在生产中将煤气中的有害杂质和水分含量控制在工艺要求范围内。

The leakage reason for some QT400-18 nodular cast iron pipe used in gas pipeline was analyzed by means of macro and micro analysis. According to the macro analysis results it can be concluded that the leakage of the pipeline was caused by local corrosion and the corrosive leakage developed from inwall to outward until piercing. Micro cracks and other defect were not found by microstructure analysis. Large S element was contained in the corrosion products of pipeline inwall according to component analysis results, which indicated that the corrosive leakage of the pipeline related to the S element in the carried gas. The comprehensive analysis results show that the leakage was as a result of local electrochemical corrosion caused by the impurity of S and condensate water existed in the pipe. Suggestion was proposed to control the impurity and water in technics range.