The hydraulic end of a centrifugal pump driven by a standard motor necessitates the presence of a sealing system on the shaft. Now it happens that 75% of pump breakdowns have mechanical sealing problems as the root cause. Therefore a pumping system in which no dynamic sealing is particularly attractive to users of dangerous liquids.
The canned motor pump comprises a traditional hydraulic centrifugal impeller close coupled to a special motor. In this motor the stator is lined in the gap between rotor and stator, confining the liquid to the rotor chamber. The pumped liquid circulates in the rotor chamber, then cooling the motor. The shroud around this chamber therefore forms an enclosed space which confines the liquid without dynamic sealing.
Furthermore, if the stator liner ruptures, the liquid is still enclosed in the motor shell (capable of withstanding an explosion). That's what we call double safety. | 
