Failure analysis of refractory anchors of powder boiler

Abstract

The present study analyse the refractory structure failure in the bull nose - hot face area of cyclone of a circulating fluidised bed combustion (CFBC) boiler. Failed anchor rods made of AIS309 SS were analyzed for chemical composition, hardness, tensile strength and microstructural condition. Sigma (s) phase induced embrittlement caused failure of anchor at the non-welded end. At the anchor-MS plate weld, poor quality of the weld was noted. Overheating from flue gas entry in the gaps caused by inadequate expansion joints resulted in damage to the backup insulation layers. At such high temperatures, the SS anchor-MS weld will have a lesser strength and weld failure occurred. Loss of anchor reinforcement resulted in falling of refractories.