Sealless Centrifugal Pump Diagrams
Figure 1: Pump Liquid End
Fluid is moved by a centrifugal pump through the use of centrifugal force. Fluid is taken into the center of the impeller through the inlet connection. Most centrifugal pumps prefer a positive inlet pressure to prevent cavitation (lack of enough positive inlet pressure to prevent liquid vaporization). This fluid is then caught by the vanes of the impeller as it spins. This rotation of the fluid mechanically by the vanes “throws” the fluid to the outside of the impeller and towards the discharge port of the liquid end of the pump. This mechanical movement of the fluid creates the discharge pressure of the pump. Variables like inlet fluid supply pressure, impeller diameter, motor horsepower and closed face versus open face all effect the flow and pressure of the pump. Each of these variables can be manipulated to achieve a desired flow and/or pressure.Figure 2: Pump Magnetic Drive
A magnetic drive pump uses a balanced magnetic field to create the rotation of the fluid impeller. Unlike a traditional centrifugal pump which has a direct drive connection between impeller and motor, a mag-drive pump eliminates the direct drive mechanism and replaces it with a magnetic field. An outer magnetic bell housing is mounted on the end of the pump shaft. This outer bell is aligned on the outside of the rear casing. The pump impeller is connected to a smaller magnet assembly and rides on an internal shaft and bushing assembly. (The liquid end parts are all isolated within the fluid head of the pump without the need for a mechanical seal.) The smaller magnet assembly is mounted within the center of the magnetic field of the outer bell housing. Although these two magnet assemblies are separated by a fluid barrier, the magnetic fields are aligned. When the pump motor is started the outer bell housing begins to rotate. As the outer bell rotates, the rotating magnetic field effects the inner impeller magnet. As the two magnets begin to turn together, the impeller begins turning and displacing fluid. Now you know how it works.