Design, Construction And Test Of Magnetic Bearings In An Industrial Canned Motor Pump

Abstract

The replacement of conventional bearings with magnetic bearings in a canned motor pump is discussed. The primary objective was the development of a long life bearings for canned motor pumps. The research project was a joint effort between the University of Virginia, Kingsbury, Incorporated, and Goulds Pump Company. The research team designed, constructed and tested the bearings in a 20 hp, 300 gpm, single stage centrifugal canned motor pump running at 3600 rpm. Both magnetic radial and thrust bearings were incorporated in retrofitted bearing housings. Displacement probes sensed the shaft position near the bearings. Control electronics then employed the displacement signal as the feedback signal to control the level of current in the magnets. Proportional-integral-derivative type analog controls were used. The bearings were successfully installed and tested. Performance and vibration tests were conducted on the canned motor pump with the original bearings and with the magnetic bearings. No significant change was found in the pump performance but some small changes were observed in the pump vibration characteristics. It is believed by the authors that this is the first installation of magnetic bearings in a commercial pump.