电站锅炉后屏过热器流体冷却间隔管爆管原因分析

Cause Analysis of Tube Explosion of Fluid Cooling Spacer in Boiler Rear Platen Superheater

某电厂#2机组锅炉后屏过热器流体冷却间隔管在运行时开裂,泄漏的高压蒸汽吹损相邻的后屏过热器管。为查明原因,对流体冷却间隔管管系的布置走向、开裂管道的宏观形貌、化学成分、金相显微组织、力学性能进行了综合性试验分析。结果表明,由于后屏过热器流体冷却间隔管技改后安装位置改变,导致管道吸热超标造成长时过热,金相组织严重球化,力学性能下降,在内部介质压力作用下发生爆破泄漏。确认失效原因后,制订了更换方案,返修后运行约30000 h后复检管道金相组织、硬度正常。

The fluid cooling spacer tube of the boiler rear platen superheater of a power plant#2 unit cracked during operation,and the leaked high-pressure steam blew the adjacent back superheater pipe.In order to find out the reason,a comprehensive experimental analysis was carried out on the layout trend of the fluid-cooled spacer pipe system,the macroscopic morphology,chemical composition,metallographic microstructure and mechanical properties of the cracked pipe.The results show that due to the change of the installation position of the fluid-cooled spacer tube of the back-screen superheater after technical transformation,the heat absorption of the tube exceeds the standard,resulting in long-term overheating,severe spheroidization of metallographic structure,deterioration of mechanical properties,and explosion leakage under the pressure of internal medium.After confirming the failure reason,the replacement plan was worked out.After repairing and running for about 30000 h,the metallographic structure and hardness of the pipeline were rechecked to be normal.