A STUDY ON THE METALLURGICAL CAUSES OF SUPERHEATER TUBE FAILURES IN BIOMASS POWER PLANTS

This article presents an investigation of a failed superheater tube made of SA210 Grade C used in a biomass power plant. Visual inspection, microstructural examinations, chemical analysis, and hardness measurements were conducted to analyze the causes of the superheater tube failure. The results showed that the failure was mainly caused by long-term overheating, resulting in excessive thermal oxidation and graphitization. Excessive thermal degradation accelerated reduction in the wall tube and facilitated the stresses generated on the tube. Graphitization degraded the microstructure of the tubes, thereby reducing the mechanical performance. The combined effects of severe thermal oxidation and graphitization are attributed to the premature failure of the tube. Therefore, SA213 T22 should be used in the superheated zone. Regular monitoring and inspection of the conditions of the tube is also recommended.