In a standard centrifugal, gear and turbine pump, the power is delivered to the pump end either through a direct connection between the rotating element and the motor shaft or through a coupling between the pump end shaft and the motor shaft. In these cases the pumping chamber needs to be sealed from the outside atmosphere. Traditionally packing or some other sort of mechanical seal accomplishes this.
The principle of a magnetic drive pump is that the rotation from the motor shaft is transferred to the pump end via a magnetic coupling which eliminates the need for the shaft seal or packing. A drive magnet is mounted to the motor shaft, which transfers the motor torque through a sealed housing to an internal driven magnet. The driven magnet is coupled directly to the pumping element (centrifugal impeller, gears, turbine impeller) inside the pump cavity. This design typically uses one static o-ring or flat gasket to hermetically seal the pumping chamber. This configuration is categorized as seal less since the motor shaft does not protrude into the pump casing. Design constraints typically associated with seals such as leakage, friction, and maintenance due to wear are eliminated.