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In production environments where liquids are continuously processed, centrifuges play a central role. These installations often operate non-stop under high load and are subject to wear over time. The rotating components, including the drive shaft, are exposed to torsion, fluctuating loads, and temperature changes.
During the production process, one of these centrifuges regularly failed, significantly reducing the factory’s overall “reliability.” It became clear that a structural issue was the underlying cause. MCI was commissioned to conduct an independent investigation to determine the nature and root cause of the problem, enabling recurrence to be prevented.
The shaft broke during operation at a rotational speed of 24 rpm and a continuous operating temperature of around 90 °C. The failure turned out not to be an isolated incident: similar fractures showed comparable damage patterns.
At MCI, we performed microscopic and SEM analysis. These techniques allowed us to inspect the fracture surfaces down to microcracks. This revealed that the fracture surface exhibited clear signs of fatigue cracking under low-frequency torsional loading. The presence of slag inclusions in the longitudinal direction of the material, combined with sharp geometries, led to reduced fatigue resistance.
Based on the investigation results, our specialists formulated targeted recommendations to address the issue structurally. Several material-related improvements were identified that can significantly increase the fatigue resistance of the shaft. Additionally, specific stress concentrations in the design were identified, for which optimisations were proposed to improve structural integrity.
Furthermore, the dynamic load caused by operational scenarios such as start-stop movements was analysed in more detail, resulting in concrete recommendations to reduce torsional peak loads. Finally, it was advised to carry out an independent assessment during future design or overhaul projects, in order to ensure reliability is embedded from the drawing board stage.
