Sealless pump rotor position and bearing monitor

Abstract

A bearing monitor for use with a canned motor pump having a wound stator and a rotor drivably coupled to an impeller, the rotor being mounted on radial journal bearings and axial thrust bearings within a containment can comprises a first and a second target embedded in an outer periphery of the rotor in axial proximity to a first and a second end of the rotor. The monitor includes a plurality of sensors mounted external to the containment can in axial proximity to each of the two targets and radially displaced approximately equally around the periphery of the containment can. A plurality of magnetic field generators create local magnetic fields coupled through the containment can, process fluid, rotor, and at least a portion of one target to one of the sensors. In response to each field, each sensor generates an output signal which varies as a result in a change in the magnetic circuit reluctance caused by bearing wear. A monitor circuit is coupled to the sensors and compares their output signals to generate a scaled output which is approximately linearly related to bearing wear. The output of sensors in the same axial plane are utilized to determine bearing wear in a radial direction, while the output of sensors in different axial planes are utilized to determine bearing wear in an axial direction. Electromagnetic shielding may be used depending on the environmental and operating conditions.