<![CDATA[This study analyzes the causes of recurrent cracking in the Primary Air Fan (PAF) ducting of a Circulating Fluidized Bed (CFB) boiler and develops improvement recommendations. The methods comprise field crack mapping, Root Cause Analysis (RCA) using Ishikawa and Fault Tree Analysis, Computational Fluid Dynamics (CFD), and Finite Element Analysis (FEA). Cracks were concentrated at panel edges, stiffener terminations, welded joints, and heat-affected zones. CFD revealed non-uniform flow and vortices at elbow/transition regions, while FEA showed maximum stress increasing from 142 MPa at 40 °C to 224 MPa at 50 °C. A 100 mm panel-edge radius reduced stress from 145 MPa to 36 MPa, or 75.2%. The novelty lies in integrating field evidence, RCA, CFD, and FEA to explain the failure mechanism comprehensively. The findings support more targeted repair strategies to improve PAF ducting reliability and service life.]]>
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