锅炉水冷壁捕渣管泄漏原因分析

CAUSE ANALYSIS OF SLAG-CATCHING TUBE LEAKAGE ON THE WATER-WALL OF BOILERS

某电厂连续发生水冷壁捕渣管开裂泄漏事故,为此对泄漏管进行了宏观、化学成分、拉伸、金相、扫描电镜和能谱等分析试验。结果表明,水冷壁捕渣管外壁敷设的耐热材料脱落,高温烟气使得该处产生膨胀差异,在管外壁形成环向的疲劳裂纹,同时使水中的杂质在腐蚀坑、沟槽的底部浓缩产生垢下腐蚀形成裂纹,进而内外壁裂纹扩展贯通使水冷壁捕渣管开裂泄漏。对此,建议电厂大小修时对水冷壁外壁敷设的耐热材料进行检查,及时修复剥落的耐热材料,并保证凝汽器的严密性及控制加氧量。

The leakage of slag-catching tubes on the water-wall of boilers has continuously occurred in one power plant.For this,the macroscopic inspection,chemical elements analysis,tensile testing,metallographic examination,scanning electron microscope and energy spectrum analysis have been carried out.The results of analysis show that the drop-off of refratory material from outer wall of the slag-catching tubes makes the high-temperature flue gas to produce differentical expansion at there,the annular fatigue cracks were occurred on the outer side of the tubes,at the same time,impurities in the water have concentrated in the bottom of etch pits and grooves,resulting in corrosion under deposit,and forming cracks,the cracks on inner and outer walls further expanded and linked up,making the slag-capturing tubes on the water-wall to be cracking and leaking.For this,it is recommended that the refractory material laid on the outer surface of water-wall should be inspected during the time of major and temporary repairs,timely repairing the dropped off refractory materials,and ensuring the tightness of condenser,as well as controlling the oxygen-dosing amount.