某余热锅炉低温过热器U型管爆管原因

Burst Reason of Low Temperature Superheater U-Tube of a Waste Heat Boiler

某新建余热锅炉运行不足两个月低温过热器U型管即发生爆管事故,通过宏观观察、化学成分分析、力学性能测试、金相检验、扫描电镜及能谱分析等,分析并确定了爆管的原因和机制。结果表明:由于锅炉运行期间炉水碱度偏高,导致低温过热器U型管积盐形成碱浓缩,在冷弯成型残余应力和蒸汽压力的共同作用下,积盐处萌生碱应力腐蚀裂纹,随着时间的推移,裂纹持续扩展,导致U型管爆管。

A low temperature superheater U-tube burst accident occurred in a new waste heat boiler after less than two months of operation.The causes and mechanism of tube burst were analyzed and determined by macroscopic observation,chemical composition analysis,mechanical property test,metallographic examination,scanning electron microscopy and energy spectrum analysis.The results show that due to the high alkalinity of the boiler water during operation of the boiler,the salt accumulation in the U-tube of the low temperature superheater formed alkali concentration.Under the combined action of cold residual stress of cold roll forming and steam pressure,the alkali stress corrosion crack was initiated at salt deposit.With the passage of time,the crack continued to expand,resulting in the U-tube burst.