Magnetic-drive centrifugal pumps are well suited for pumping caustic and hazardous fluids because shaft seals are not required. Instead of shaft seals, magnetic-drive pumps generally feature a pump shaft separated from a drive shaft by a containment shell. The drive shaft is arranged to rotate with a first magnetic assembly, which is magnetically coupled to a second magnetic assembly. The second magnetic assembly applies torque to the pump shaft to pump a fluid contained within the containment shell.
The reliability of containment shells may be rated in terms a burst strength. The burst strength is a pressure per unit area from the pumped fluid on the containment shell that results in damage to the containment shell sufficient to cause the leakage of fluid from the containment shell. In general, the higher burst strength, the better the containment shell. However, increasing the burst strength of a containment shell poses some difficult technical obstacles. For example, increasing the thickness of the containment shell or adding metallic reinforcement to the containment shell may significantly degrade pump performance, making any increase in the strength of the containment shell irrelevant. If the thickness of the containment shell is too great or if metal reinforcements are used indiscriminately, magnetic coupling between the first magnetic assembly and the second magnetic assembly may be impaired. In turn, the impeller may stop rotating entirely or may rotate too slowly for proper pump performance. Thus, a need exists for a containment shell with a superior burst strength, without sacrificing the requisite efficiency of the magnetic coupling between the first magnetic assembly and the second magnetic assembly.
Many magnetically driven pumps include a front support and a rear support to support a rotating or a stationary pump shaft. The front support is often located such that the front support obstructs the inlet flow to the impeller, detrimentally limiting the performance of the pump under conditions of low net positive suction head (NPSH). Meanwhile, the rear support may be integral with a containment shell of polymer composite construction. The containment shell of the dual-support pump is often structurally inadequate to support a shaft without the assistance of a front support. Consequently, elimination of a front support for low net NPSH applications may reduce the burst strength of the containment shell, provide inadequate radial support for the pump shaft, or otherwise detrimentally impact pump reliability. Thus, a need exists for a containment shell that can support radial loads from a cantilevered shaft, while meeting a burst strength design goal.