Spherical roller  bearings  are principally provided with two rows of symmetrical spherical rollers and a common sphere raceway in out ring, the two inner ring raceways are included at an angle to the bearing axial. The bearings have good self-aligning ability and can operate when the shaft deflection under load or the shaft deflection under load or the shaft misaligningment in mounting, and their permissible aligning angle is 1 to 2.5 degree. This type of bearings has heavy load carrying capacity and anti-impact ability, in addition to radial loads, they also can carry axial loads in two directions. In general, this type of bearings permit a low limiting speed.