Magnetic drive pumps make use of a magnetic coupling to turn the impeller, which provides the pumping action. The impeller is joined to a shaft bearing a permanent magnet. This structure is sealed in a containment unit separate from the motor. A second set of magnets is joined to the drive shaft that connects to the motor. The two sets of magnets form a coupling that transmits the torque from the motor to the impeller.
Such a design eliminates the need for a seal around the drive shaft, which is the norm for standard pumping devices. The elimination of the seal greatly lessens the possibility of leakage. Damage to a pump seal from vibration and loss of integrity from aging increases the risk of material loss over time. Magnetic drive pumps effectively eliminate this problem and are the design of choice for handling high-risk materials.
Typically, magnetic drive pumps are used to move liquids such as gasoline, diesel fuel and heating oil. Pump leakage in transferring these types of materials would constitute a serious combustion hazard. Properly designed magnetic drive pumps are also capable of handling corrosive agents, high temperature material and hazardous chemicals. Environmental contamination can be limited when moving sewage and wastewater.
The two basic designs for magnetic drive pumps are the rotating shaft and the stationary shaft. The rotating shaft design is the more robust of the two, typically constructed of metal components. This offers the greatest capability for heavy-duty applications requiring high pressure or temperature. Stationary shaft pumps offer a simpler design and make use of plastic or ceramic parts. This increases corrosion resistance, but limits their use to a narrower operating range for temperature and pressure.
Magnetic drive pumps are generally rated according to their discharge flow and pressure, intake and discharge diameter, as well as temperature of the material it is capable of safely handing. A power source is not necessarily included with the pump. The pump has been successfully adapted for use with compressed air, internal combustion and electric power sources.
The design is suited to a variety of industrial, commercial, and home applications. Safety is increased in the chemical and petroleum industries by eliminating the leaks common to standard pumping devices. In municipal sewer and wastewater treatment facilities, magnetic drive pumps help reduce contamination and preserve environmental integrity. The containment of the material being moved within a sealed shell provides the control needed in the food processing and pharmaceutical industries. At home, such pumps are often found in aquariums and home brewing equipment.