Hydrogen damage in a power boiler: A study of damage selectivity and conditions

Abstract

We report two evaporator tube failures that took place in the same boiler owing to hydrogen damage within an interval of approximately one year. Notably, hydrogen damage occurred selectively on recently repaired tubes. In contrast, some of the original tubes that had been operating for 18 years or longer remained intact under the same environment. Comprehensive metallurgical investigation and chemical analysis revealed that the older tubes slowly developed a thin film of evaporation residue on their inner surface, which had a protective effect and suppressed the progress of corrosion. Hydrogen damage is more likely to proceed in the electric resistance welding (ERW) part than in the other parts. Kinetic consideration proved the rapid (within 18 hours) progression of hydrogen damage in evaporator tubes. Moreover, it confirmed that the hydrogen damage could be stemmed by instantaneous shutdown without improving the water quality immediately. The cleaning test suggested that tubes that already suffered hydrogen damage may be further damaged during acid cleaning. These results can help identify the cause of hydrogen damage in evaporator tubes due to poor water quality and determine the area of tube renewal/repair.