热网加热器不锈钢管腐蚀泄漏的原因分析

CASE ANALYSIS OF CORROSION LEAKAGE OF STAINLESS STEEL PIPES OF HEATERS FOR A HOT WATER SERVICE SYSTEM

某电厂热网加热器不锈钢管使用不到一年即发生大面积泄漏事故,对其进行失效分析,根据现场的实际情况,取得实际水质资料,并对不锈钢管进行宏观检查、化学成分分析、扫描电镜和能谱分析等检验与分析,确定失效原因为:此热网加热器不锈钢管处于保养期约7个月内,水中的细微泥沙在管束中逐渐沉积管内壁,由表面污垢隔离形成的管内壁闭塞区,氧的浓度大幅度降低,在温度及pH值合适的条件下,硫酸盐还原菌(SRB)在管内壁闭塞区大量滋生繁殖,它的大量滋生繁殖引起了管子严重腐蚀,最终导致管子穿孔泄漏.

Large number of leakages of stainless steel pipes of heaters for a hot water service system occurred in one power plant after the system putting in service less than one year. The failure analysis was processed. Accordingly, we collected the data of the quality of water, and examined the stainless steel pipes by metallography,chemical analysis, as well as scanning electron microscopy with energy spectrum analysis. The results showed that due to the system was brought to a standstill for about seven months, mud and sand in the water deposited as scales sediment on the pipe wall. Areas under which oxygen concentration might decrease greatly and hince,sulfate-reducing bacteria（SRB） would breed lastly in such occluded areas at appropriate temperature and pH conditions, SRB influenced corrosion might become serious and finally caused the pipe leaking.