Failure Analysis and Treatment of Under-Scale Corrosion Burst in CFB Boilers’ Water Wall Tube

In a company’s circulating fluidized bed power plant boiler, the furnace water wall tube burst occurred several times a month. In this paper, the failure mode and the cause of the tube burst of the water wall were analyzed by macroscopic inspection, chemical composition analysis, metallographic examination, fracture SEM analysis, and EDS analysis of the corrosion products. It is concluded that the damage modes of the water wall tube burst are high temperature hydrogen corrosion and alkali stress corrosion cracking. The root cause of the damage cracking is the inner wall scale of the water wall tube in the high heat load area, which induced heat transfer deterioration and medium concentration corrosion under the scale.