Investigation into the failure of a superheater tube in a power generation plant utilizing waste material combustion in a furnace

Abstract

This study presents an investigation into the failure of a superheater tube. To pinpoint the primary cause of failure, a range of destructive and non-destructive analyses were conducted at various points on both the failed and non-failed sides of the tube. Visual inspection unveiled longitudinal fissures indicative of the initiation of a fish-mouth opening, along with minor bulging, a slight diameter increase, and a marginal thickness reduction at the failure zone. Through chemical composition analysis, mechanical testing, and hardness measurements, it was determined that the material satisfies the specification for low-alloyed steel as per P265GH standard. The microscopic examination revealed the non-fireside (not failed) of the tube consisted of ferrite and pearlite structure, whilst the fireside (failed) showed spheroidization of the pearlite colonies without any evidence of recrystallized grain structure. A more in-depth examination using scanning electron microscopy on the failed section indicated that the tube rupture on the fireside was triggered by an interactive mechanism involving sulfidation corrosion and thermal fatigue. The propagation of cracks occurred through an environmentally assisted thermal-fatigue process. Suggestions for corrective actions have also been proposed to prevent this type of failure.