Spherical roller bearings are self-aligning bearings designed for heavy radial loading. The rollers are barrel shaped. These bearings automatically compensate for large angular errors commonly called shaft misalignments. They are usually of double row design, both the rows of the rollers having common spherical raceways in the outer ring. This feature has great practical importance in those cases where it is difficult to obtain exact parallelism between the shaft and housing both axes.