Abstract: A fluid pump includes main support bearings for supporting the impeller shaft and back-up bearings for supporting the shaft upon failure of the main support bearings. The back-up bearings are positioned between the main support bearings and shaft driver/motor, and have a radial clearance with the shaft which is greater than the radial clearance between the main support bearings and shaft and yet is small enough to prevent any shards that may result from failure of the main support bearings from passing through the radial clearance space between the back-up bearings and shaft and damaging other rotating parts of the pump. A diagnostic monitor detects wear or failure of the main support bearings by sensing relative shaft displacement. Also, a controller causes the driver to shut down when a predetermined amount of allowable wear of the main support bearings is reached.