What Is a Bearing Heater?
A bearing heater is a device used for the installation of the inner ring of a bearing onto a shaft through a hard fit. This process, known as burnishing, utilizes the metal’s expansion when heated to increase the inner diameter of the bearing’s inner ring, allowing for a secure fit onto the shaft.
While other methods such as heating bearings in an oil bath exist, they are time-consuming and carry risks such as uneven heating and potential weakening of the bearing material. Bearing heaters often use electromagnetic induction for heating, addressing these issues effectively.
Applications of Bearing Heaters
Bearing heaters are essential when the inner ring of a bearing and a rotating shaft need to be securely clamped together. For small bearings with minimal clamping allowance, a press-fit method may suffice. However, for larger bearings requiring significant tightening allowance, bearing heaters offer a more efficient solution. The choice between clamping the inner or outer ring depends on the load direction and magnitude each ring will face. In cases where both rings must be secured, specific fitting strategies are employed to ensure a secure attachment.
Principle of Bearing Heaters
The principle of bearing heaters involves heat shrink fitting, where the bearing is uniformly heated and expanded, allowing the shaft to be inserted into the enlarged bore. Upon cooling, the bearing contracts to its original size, creating a tight and secure fit with the shaft. Electromagnetic induction is commonly used in bearing heaters, functioning similarly to a microwave oven by generating heat through eddy currents induced by magnetic flux. This method avoids direct flame use, is space-efficient, and includes safety features like demagnetization functions to prevent the attraction of ferrous debris to the magnetized bearing after heating.
Other Information on Bearing Heaters
Temperature of Bearing Heaters
Bearing heaters can reach various temperatures, with some induction types capable of heating up to 200°C. However, it is recommended to assemble bearings at temperatures of 120°C or lower to avoid exceeding the tempering temperature of the bearing material, which could reduce its strength. A temperature difference of 90°C between the bearing and shaft usually provides sufficient expansion for assembly without risking overheating.