超超临界机组疏水罐罐体泄漏原因分析及防治

Cause Analysis and Prevention of Drainage-Tank Leakage in Ultra-supercritical Power Plant

对运行不到2年的某电厂1 000 MW超超临界火电机组再热热段管道疏水罐罐体开裂的原因进行了分析。首先对罐体进行超声检测、然后对裂纹进行解剖,对裂纹周围微观组织、裂纹断口形貌进行观察分析。结果表明,再热热段管道疏水罐开裂的主要原因是再热管道上的冷凝水反复回流,造成罐体上下部分温差较大,从而产生热疲劳裂纹,最终热疲劳裂纹扩展导致泄漏。对此,建议改进疏水罐结构并采用过热度控制方式,且定期对疏水罐进行超声检测。

The cause of drainage-tank leakage of the reheat steam pipe is analyzed in a 1000MW ultra-supercritical power plant which has been operated for less than two years.Firstly,the tank is examined using ultrasonic,then the crack is dissected,and finally the microstructure and fracture morphology of the crack are inspected carefully and analyzed.The results show that,the cracking of the pipeline hydrophobic tank in the reheating section can largely be attributed to the repeated reflux of the condensate water on the reheat pipe,which causes significant temperature difference between the upper and lower parts of the pipe,and hence the thermal fatigue cracks are generated.Eventually the thermal fatigue crack propagation leads to the leakage.Therefore,it is suggested that the structure of the drain tank should be improved and the superheat control mode should be adopted.Additionally the ultrasonic inspection for the tank should be carried out regularly.