Sealed bearings are rolling-element bearings that provide smooth radial or axial motion for a spinning system while protecting internal components from external contamination. These bearings are used in many applications, specifically those where moisture, chemicals or fine particles are present and have the potential to enter the bearing, causing friction, heat and lowered capabilities.
Related Categories
Standard ball bearings, including sealed bearings, have three main parts: an inner ring, the balls and an outer ring. The two rings act as races, or pathways, for the balls to travel around while spinning. The surface contact between the rings and the balls is minimal, though there is very little space or clearance above or below the balls. Separators may be used to keep the balls apart so they do not cause friction or wear on each other. Sealed bearings add another component: sides. Generally rubber or plastic, these sides protect the balls from contaminants such as dust and oil mist. Sealed bearings cannot be re-lubricated after the initial process because the seal would be ruined. Sealed bearings are used in places that are infrequently accessed or where maintenance is impractical because the bearing is difficult to access. Motors, spinning machinery, pumps and other equipment use sealed bearings for smooth, precise, low friction motion.
Sealed bearings are most commonly made from synthetic rubber that is molded to a steel plate that is incorporated into the outer ring of the ball or roller bearing. They are either contact or non-contact types, depending on whether the seal touches the inner race. Sealed contact bearings are slightly better at keeping out moisture, but they also create friction and therefore heat, resulting in higher temperatures and decreased efficiencies. Non-contact bearings do not provide as high performance as their contact counterparts because they cannot seal out moisture as well; at the same time, they also do not add significant amounts of friction because they do not touch the race. Bearings may be sealed on one or both sides. Shielded bearings are a similar product. Steel plates are attached to the bearings to protect them from penetrating foreign materials like dirt. They also prevent grease from leaking out of the ball bearing. These shields are all non-contact, which keeps the friction low. Shielded bearings may be re-lubricated fairly easily because the plates are simple to remove and reattach. While they provide more protection than an open bearing with no sides, shielded bearings cannot protect the balls from moisture because while they are physical barriers, they have no seal to block small particles.
