Failure analysis and radial load characteristic study of a magnetic-levitated marine mixed flow pump

Marine centrifugal pumps pose significant challenges in maintenance and spare part replacement, making the extension of their maintenance-free operation period and service life a long-standing research objective. The magnetic levitated pump equipped with active magnetic bearings (AMBs) enables a non-contact, wear-free support mechanism while eliminating internal mechanical seals, thereby substantially enhancing maintenance-free operation duration and prolonging service life. Targeting at a novel marine magnetic levitated mixed-flow pump unit, this study investigates a bearing overload failure observed during pre-deployment testing in inclined position. The study attributed the cause to the sharply increased radial load on the pump shaft under part-load conditions based on experimental data analysis. Subsequently, a full-scale Computational Fluid Dynamics (CFD) analysis was conducted to numerically calculate the radial load, and the accuracy of the numerical method was validated with experimental data. Furthermore, by extracting and analyzing the radial forces and flow field distribution characteristics of the primary radial force source—the impeller-diffuser structure—under varying flow rates, the intrinsic mechanism behind the sudden increase in radial forces within the impeller-volute structure under low-flow conditions was elucidated. Finally, the applicability of the similarity law in predicting impeller radial loads at different rotational speeds was numerically and experimentally validated. The findings of this research hold significant implications not only for the design and lifespan optimization of magnetic levitated pump units but also for pumps utilizing conventional mechanical bearings, particularly those deployed in marine environments where non-horizontal installation or operation under tilting and swaying conditions is required.