Bearing Heaters Information
Bearing heaters use heat to facilitate the assembly or disassembly of bearings, gears, sprockets, and other machine components. Heat is introduced to the inner ring of the bearing, which causes thermal expansion and allows the bearing or gear to be mounted or dismounted without damage. A temperature sensor mounted to the bearing inner ring measures the temperature as the bearing heats, typically between 230° to 250° F (110° to 120° C). Some heaters are furnished with adjustable thermostats to prevent overheating. Some heaters have a demagnetization built-in cycle, while others are designed to prevent magnetization during heating.
Proper bearing alignment is critical to optimal bearing performance and maximum bearing life. Improper installation can create a misalignment with the shaft and lead to premature bearing failure. Heating a bearing with a bearing heaters will cause the inner ring of the bearing to expand slightly and allow for easy, misalignment-free mounting of the bearing to the shaft. Once the bearing cools, it creates an interference fit. This process is referred to as induction shrink fitting.
Bearing heaters eliminate the need for pressing or hammering cold-mounted bearings, which can cause misalignment and reduced bearing life. They are also a safer alternative to a torch or hot oil bath, which are less precise heating methods and pose an increased risk of injury to the user. Direct heat from a torch can damage a bearing, and should never be used. Oil baths take a long time to sufficiently heat the bearing, and may be dirty, in addition to posing handling hazards.
The three most common types of bearing heaters for bearing assembly are yoke style, cone style, and hot plates.
Yoke style bearing heaters (also referred to as induction bearing heaters) are designed with a yoke that is placed through the bearing bore. Electrical current flowing through the bearing causes it to heat up. Many bearing heaters have different size yokes which can be changed to accommodate various bearing sizes. The yoke spans a support member on one end and a heating coil on the other. During heating, the bearing inner ring rests against the yoke. If the bearing is large enough, and there is space around the coil, the bearing may be placed over the coil for more efficient heating.
Hot plate style bearing heaters have a flat heating surface, and are specifically designed for heating bearings. Hot plates are typically used for heating smaller bearing sizes.
A yoke-style (left) and hot-plate-style bearing heater.
Cone style bearing heaters are, as the name implies, cone shaped, and are have a stepped design to accommodate a range of bearing sizes. Heat is transmitted from the cone into the bearing inner ring, which eliminates the magnetization caused by induction heaters.
While bearing pullers are the most common bearing removal tool, specialty bearing heaters for dismounting cylindrical roller bearing inner rings are also available.