热电厂余热锅炉疏水管爆管失效分析

Failure Analysis on Drain Pipe in Heat Recovery Boiler at Thermal Power Plant

通过宏观分析、显微组织观察、力学性能测试、硬度测试以及能谱成分分析,对某热电厂余热锅炉20G疏水管爆管原因进行了分析。结果表明:爆口管件存在明显胀粗;爆口附近珠光体已经完全球化,并且存在轻度石墨化现象,表明该管件长期超温;管件的室温拉伸性能略低于标准要求的下限值,说明材质性能下降。结合疏水管现场空间结构推断,疏水管隔仓与受热面烟气通道之间缺乏有效的密封,存在高温烟气向隔仓内流动,导致疏水管局部因长期超温而爆管。

The failure analysis of 20G steel drain pipe in heat recovery at a thermal power plant was investigated by means of macro analysis, metallographic analysis, mechanical performance testing, hardness measurement and EDS analysis.The results show that the failure pipe is swelled;the complete spheroidization of pearlite with light graphitization appears at the burst area, which indicates long-term overtemperature problem existed for this pipe. The strength of pipe does not meet the lower limit of standard, which indicates the strengh decreases. Considering the structure of the drain pipe in boiler, this long-term overtemperature burst is caused by high temperature flue gas because of the lace of effective seal between gas passage and drain pipe system.