660MW超临界锅炉末级过热器爆管原因分析

Cause Analysis of Ruptured Finishing Superheater Pipe on 660 MW Supercritical Boiler

某电厂660 MW机组锅炉末级过热器投运1 a来连续发生5次爆管泄漏事故。采用化学成分分析及金相组织、扫描电镜、X射线衍射等检测手段分析末级过热器爆管原因。分析检查发现,末级过热器T91钢管爆口处金相组织老化,爆口下方TP347H管材内壁氧化物为饱和价态Fe2O3。因此认为,管系中异物或氧化物脱落堵塞导致的短时超温过热是锅炉末级过热器爆管的主要原因。建议查找堵管异物,监测锅炉在启机过程中的温升速率及停机过程中的冷却速度,避免类似事故再次发生。

The finishing superheater pipe of 660 MW supercritical boiler had been ruptured over five times since it was put into operation. The bursted pipe was studied by chemical analysis, metallurgical structure, scanning electron microscope, and X-ray diffraction. The results showed that the metallurgical structure of ruptured T91 were aged, and the quantivalency of Fe203 in deciduous oxide attached TP347H pipe under the ruptured site were saturated. The short-time overheated which caused by foreign substance in pipe or the deciduous oxide were the main reasons of pipe bursting. Finding the foreign substance in pipe and monitoring the speed rate of temperture during the starting and ending process in 660 MW supercritical boiler in order to avoid the same accident were suggested.