This study investigates the structural integrity thermal behavior and failure risks associated with a horizontal fire-tube boiler (Model MS61681) with a carbon steel furnace constructed according to BS 1501-151 GR K30A. After nearly 29 years of operation approaching the end of its design life per ASM Metal Handbook Volume 11 .This boiler was evaluated through a combination of mathematical modeling, finite element analysis, computational fluid dynamics(Thesis phase 2) and non-destructive testing ..Thermal modeling confirmed that although the boiler typically operates at 236°C, transient startup conditions could rapidly elevate furnace wall temperatures beyond 600°C. These temperatures significantly exceed the critical creep threshold of 450°C, exposing the material to thermal degradation, accelerated creep, and mechanical stress. Mechanical stress analysis showed that at 600°C and the induced stress reached 1406 MPa, surpassing the temperature-dependent yield strength of the material (295–360 MPa). CFD and FEA results (thesis phase 2) further revealed high-stress concentrations at tube sheet joints and welds, aligning with physical inspection data and emphasizing the critical role of thermal fatigue and stress localization in crack propagation.A critical finding was the identification of a penetrated crack along the longitudinal weld seam, located near the burner zone an area exposed to intense thermal stress and suspected flame erosion. Although UTG measurements showed no abnormal thinning and the corrosion rate remained within BS 2790 standards (0.75 mm), the penetrated crack in a high-risk location overrides other acceptable indicators and highlights an urgent structural concern. Continued operation under these conditions without repair or replacement, presents a serious risk of catastrophic failure or explosion.Based on these findings, several policy and practice recommendations are proposed establishing strict temperature control standards to keep furnace wall temperatures within safe limits adhering to minimum wall thickness and reinforcement requirements per international standards and integrating simulation guided design improvements using FEA and CFD for material selection and structural optimization. The study emphasizes the need for regulated NDT inspection protocols focusing on welds, thin walls, and CFD-identified hotspots. Continuous temperature monitoring using thermocouples is recommended for high-risk zones. Stress-based safety systems and automated emergency shutdown mechanisms should replace traditional temperature-based alarms for better operational safety. Integrating smart sensor technologies with CFD/FEA data and machine learning algorithms can enable real time predictive maintenance, aligning with Industry and circular economy principles. This research highlights the critical role of NDT in identifying hidden structural flaws early . These practices are essential not only for enhancing operational safety but also for extending boiler lifespan in line with circular economy principl also provides a framework for transforming boiler operation from reactive maintenance to proactive, predictive management grounded in data, engineering standards and simulation intelligence. Future research directions include developing multiphysics simulation models that couple fluid dynamics, combustion chemistry, structural mechanics, and thermal behavior to capture more complex failure mechanisms. Investigation into advanced materials and refractory coatings is also encouraged to reduce heat induced stress. Additionally, incorporating long-term creep and degradation modeling will improve lifecycle predictions.
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