2022 2023 TFE ELM MULIEJI LELESA RODRIGUE

This thesis investigates the recurrent fractures of the agitator shaft in tank six of the cobalt production circuit at Kamoto Copper Company (KCC). The study aims to identify and analyze the mechanical, design, and operational factors responsible for these failures, and to propose measures to improve the reliability and service life of the industrial agitator AMX16000. After a general review of cobalt production processes and the critical role of agitating systems in hydrometallurgical operations, the work presents a technical description of the agitator, its operating conditions, and its failure history. The methodological approach combines reliability analysis based on Weibull statistics (evaluation of TBF and reliability indicators), analytical calculation of mechanical solicitations (bending, torsion, fatigue, pressure and hydrodynamic forces on the blades), and numerical simulation using COMSOL Multiphysics. The results highlight the predominance of fatigue mechanisms aggravated by high torsional moments, stress concentrations, and possible deviations in alignment and structural loading. The simulations confirm critical stress zones on the shaft and blades, consistent with observed fracture locations. An economic analysis quantifies the production losses and maintenance costs associated with these recurrent breakdowns. The study concludes with recommendations on design optimization, operating parameter control, and preventive maintenance strategies to enhance the durability and reliability of the agitator and, consequently, the robustness of the cobalt production process.