Metallurgical investigation of boiler tube failure in a power plant

Abstract

The boiler tube used in the power plant industry had failed prematurely after 11 years of service, which was used to supply steam at working temperature – 420 °C (approx) and working pressure of about ∼ 146 kg/cm2. The failed tube cut off the steam supply to the power plant industry and caused the plant to shut down for several days. So in this paper, the root cause failure of the boiler tube has been investigated. The tube was made from SA 210 Gr. C steel supplied in hardened and tempered conditions. However, certain defects in the manufacturing process and corrosion/erosion in the tube have initiated to thin the tube and resulted in failure of the tube. Due to these defects, the wall thickness was reduced by more than 20% of the nominal thickness. The microstructure analysis around the failure zone and away from the failure zone confirms the normal microstructure of ferrite and pearlite. Finally, it is recommended to use a defect-free tube and in case of severe erosion, ultrasonic wall thickness measurement may be carried out to check the reduction in thickness, so that the premature failure of the tube can be avoided in the near future.