Electrical submersible pumps (ESP) are normally installed on the bottom end of jointed production tubing within a cased wellbore and powered by a power cable typically attached to the outside of production tubing. In this configuration, an annulus is formed between the tubing and the wellbore casing and the produced fluids are pumped up the production tubing to the surface.
The ESP pumps typically have a large number of stages, each stage having a stationary diffuser and a rotating impeller. The rotating impellers exert a downward thrust as the fluid is moved upward. The downward force is generally handled by a thrust bearing radially mounted on the pump shaft. Size constraints in a producing well limit the thrust bearing diameter and thus its load bearing capacity. To prevent bearing overload in some pumps, additional thrust bearings have been added at different locations along the shaft length. Attempts to distribute the load equally to the bearings include the use of springs and linkages. However these attempts have not been able to provide equal loading distribution.