This pump runs dry

Erie, PA--Finish Thompson Inc. (FTI) says its KC 6-8-10 Series magnetic drive pump eliminates the damage that frequently occurs to conventional pumps during startup rotation checks, or when the pumps are operated under low-liquid-level conditions. Though its product development process ended in success, at the onset FTI faced several major challenges.

The first design requirement was to find internal magnets that were considerably lighter and smaller than what was commercially available at the time. Reducing the weight of the rotating components would make it possible to reduce the size of the bushings and generate less heat. The solution: Engineers used neodymium rare earth magnets, reducing the magnet assembly weight from 3 to 4 lbs to approximately 1/2 lb. Also, the cantilevered design of the impeller spindle provided added impact resistance, reducing breakage, frictional heat, and heat buildup.

Another challenge for engineers was finding a bushing material with strong self-lubricating properties. FTI chose P-658RCH carbon-graphite from Morgan Advanced Materials and Technologies (MAMAT; St. Mary's, PA). The material assists in laying down a low-friction transfer film that helps control temperature rise if the interface becomes dry. In addition, the material provides the corrosion resistance necessary for many of the applications in which these pumps are used, such as chemical processing, pcb manufacturing, and pharmaceutical and plating applications.

The combination of lighter magnets and self-lubricating carbon-graphite material enables the pump to run indefinitely without lubrication, says Jeff Richmond, director of research and development at Finish Thompson. "The same design features that allow the pump to run dry provide nearly unlimited bearing life," he adds. "The benefit to the user is reduced down time and reduced maintenance cost."