Analysis of Leakage Failure of Convection Pipes in a Boiler

Surface corrosion and leakage occurred on a large number of convection pipes in a boiler. Based on macro and micro corrosion morphology analysis, metallographic analysis, chemical composition analysis, and mechanical property testing, combined with the actual operating conditions on site, the causes of convection pipe failure were analyzed. The results show that the properties of convection pipe material were normal. The main cause of leakage of the convection pipes was that the pipes were perforated by oxygen corrosion in condensed water. There were corrosive ions (chloride, sulfate, etc.) in the condensed water, these ions were absorbed at corrosion points, causing the destruction of the surrounding passivation film and accelerating electrochemical corrosion. Finally, penetrating holes were formed and steam leakage occured in the convection pipes.