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Mounting Bearings Using Heat
Last Updated: 09/13/2012
Application Note and Video courtesy of SKF Maintenance Products.

The force needed to mount bearing increases rapidly with bearing size. Because of the mounting force required, larger bearings cannot easily be pressed onto a shaft or into a housing. Therefore the bearing or the housing is heated before mounting.
Principle of induction heating
An induction heater can be compared to a transformer using the principle of a primary coil with a large number of windings, and a secondary coil with a few windings, on a mutual iron core. The input/output voltage ratio is equal to the ratio of the windings, while the energy remains the same. Consequently, the secondary coil will provide a low voltage at high amperage. In the case of the SKF induction heater, the bearing is a short circuited, single turn, secondary coil through which a low A.C. voltage flows at high amperage, thus generating high heat. The heater itself, as well as the yoke, remains at ambient temperature. As this type of heating induces an electric current, the bearing will become magnetized. It is important to ensure that the bearing is then demagnetized so that it will not attract metal particles during operation. All SKF induction heaters have automatic demagnetizing cycles.

Hot mounting
The temperature difference between the bearing and seating depends on the magnitude of the interference fit and the bearing size. Normally a bearing temperature of 80 to 90 C (144 to 162 F) above that of the shaft is sufficient for mounting. Never heat a bearing to a temperature greater than 125 C (257 F), because the material may change metallurgic ally and produce alterations in diameter or hardness. Local overheating must be avoided and in particular never heat a bearing using an open flame. Wear clean protective gloves when mounting a hot bearing. Lifting (hoisting) gear can facilitate mounting. Push the bearing along the shaft as far as the abutment and hold the bearing in position, pressing until a tight fit is obtained.

Lifting gear

 Never heat a bearing using
an open flame
Reliability Direct, Inc. supplies a full range of heating tools, such as induction heaters and electric plates with an adjustable thermostat and cover for all common mounting needs.

Video Demonstration SKF TIH Series Induction Bearing Heaters

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