FAILURE OF OIL-FIRED BOILER WATERWALL TUBES DUE TO INTERGRANULAR CORROSION-FATIGUE PROCESS: A CASE STUDY

摘要

Internal corrosion and circumferential cracking due to a corrosion fatigue process are some of the most common failure causes of waterwall boiler tubes. The case study reported in this paper considers the failure of waterwall tubes of a small subcritical refinery boiler due to a combination of both processes. Circumferential cracking is reported in supercritical boilers with the characteristic feature of transgranular cracks. Intergranular corrosion fatigue cracks were present as a result of high temperature, which resulted from the presence of internal corrosion and formation of heavy deposits. While internal corrosion played a key role in the failure mechanism, the root cause of the failure is considered to be related to the generation of reducing atmospheres and high thermal flux due to flame impingement.