CASE STUDY: Failure analysis of induced draft fan after serious inspection by overlay welding

•The failures of IDF occur after serious inspection.•Cracks occur not in areas that have high-stress concentrations.•The failure occurs due to residual stress in the HAZ region generated by the overlay welding process. IDF or Induced draft fans are one of the components in a steam power plant that functions to dispose of the combustion gases of coal in the steam generator. IDF operation is inseparable from the failure problem, both on the fan or IDF shaft. During operation, real-time monitoring of IDF is an important factor to determine technical conditions and detect failures at an early stage. When something that can cause failure is detected, an inspection is needed to ensure that the IDF components continue to function properly, such as First-Year Inspection, Simple Inspection, Mean Inspection, and Serious Inspection. The failures of IDF occur after serious inspection, cracks occur on the IDF shaft, where cracks occur not in areas that have high-stress concentrations. This failure on the IDF-Shaft does not reach the final fracture because of the detection of the vibration monitoring device so that when the trend rises at a certain peak, the IDF operation will shut down automatically. The failure occurs due to residual stress in the HAZ region generated by the welding process at making the impeller. The formation of residual stresses in the welding process, welding metals, and parent metals undergo a thermal cycle of heating and cooling. This thermal cycle causes stresses and stresses which in turn result in residual stresses and distortion. Residual stress can cause shaking, reduce fatigue resistance, welding strength, and corrosion resistance.