A mag drive pump is a pump with no dynamic shaft seal, which transmits torque from the driver to the pump through magnets separated by a containment shell. Mag drive pumps can be rotary or rotodynamic and are used in applications where it is important that the liquid is contained or controlled.
Image 1 shows a sectional of a rotodynamic mag drive pump. Items 230 and 232 are the magnets that drive the pump and item 231 is the containment shell. The magnets transmitting torque across the containment shell limit the need for a shaft mechanical seal and the potential leakage if it failed.
For more information on rotary and rotodynamic mag drive pumps, refer to ANSI/HI 4.1-4.6 and ANSI/HI 5.1-5.6, respectively, at pumps.org/standards.