Failure Analysis of Y-Anchors of Hot Cyclone Refractory of Circulating Fluidized Bed Boilers

The Y-anchors are critical components of a refractory system since they are used to hold the components to the wall of industrial equipment or furnaces to be used in aggressive environments. It is estimated that up to 40% of refractory lining failures can be attributed to a problem with the design of the anchor system or improper installation. Proper anchor material selection, design, and installation are essential to the performance of refractory lining. This paper aims to investigate the root cause of Y-anchor fractures resulting in refractory detachment/falling of walls and roof refractory lining in hot cyclones inlet ducts of 02 × 250 ton/hr circulating fluidized bed (CFB) boilers at the FFBL Power Company Limited (FPCL) power plant. The methodology adopted in this study involves analyzing the failed anchors made of AISI 310S for chemical composition, mechanical properties including tensile strength-h, hardness, impact strength, and microstructural condition using SEM analysis. The results of the analyses revealed that the failed material had the sigma phase embroilment which caused the failure of anchors near the welded joint location. Sigma phase embrittlement is a damage mechanism that occurs when AISI 310S stainless steel is exposed to approx. 800 °C temperature which results in reduced impact strength at 30 °C temperature. Loss of anchor reinforcement resulted in the falling of refractory in the inlet ducts. Based on these findings, it can be concluded that anchor failure resulted from improper design and material selection which was not suitable for the required service temperature range. The study also highlights the significance of conducting root cause analysis to ensure the safe and efficient operation of equipment.