In order to heat a bearing for proper bearing installation, you can use multiple methods. In this case I will compare using an Oil Bath Heater to using an Induction Heater.

In an Oil Bath Heater you need a container which will be filled with oil and heated in order to place a bearing in the hot oil to heat the bearing.

Using proper protection is essential in using Oil Baths; you also need to be absolute certain that the container and the oil within is clean. If the oil was previously used then that oil must be filtered to remove contaminants.

Monitoring of the temperature is imperative, not only to make sure that you do not overheat the bearing but also that you do not reach the oil’s flash point and create a fire hazard. You also need to make sure that there is enough oil in the container to cover the volume of the bearing. This will allow the bearing to reach the temperature of the oil and sufficient time needs to be alotted for this to take place.

Once the bearing has reached the desired temperature, absolute care needs to be taken with the excess oil that will be on the bearing—wearing your Personal Protective Equipment (PPE) is essential. If a pre-lubricated bearing was heated it is important to completely clean the bearing and new bearing lubrication be added.

In comparison, if an Induction Heater is used, make sure that you are using the correct induction heater based on the weight of the bearing, and also make sure that you are using the largest possible yoke or crossbar for the I.D. of the bearing being heated. Also make sure gloves are used to handle the bearing after the heating cycle is complete.

Place the bearing with either the horizontal yoke going through the bore or one of the vertical posts going through the bore. Set the desired temperature on the induction heater, make sure to place the temperature probe on the inner bore or ring of the bearing not on the outer diameter part.* Select the temperature to which you wish to heat the bearing (not to exceed 250° F) and press start to begin the heating cycle. Once the heating cycle is completed and the bearing has automatically been demagnetized** place the bearing on the shaft.

Comparison: The induction heater has the major advantage over the oil bath method. Several things stand out immediately, safety foremost among them, along with precise temperature monitoring and control. Safety-wise, the oil bath method has some serious drawbacks, chief among them the burn hazards to the operator, respiratory hazards and the possibility of flash fires. In addition, the possibility of contaminating the bearing and poor temperature control are other significant disadvantages compared to induction heating. The temperature is being set for the oil, it is difficult to gauge the temperature of the bearing as it is submerged in the oil.

*Note: Best induction heaters like our SURETHERM actually offer two temperature probes so that you can mount the probes on both the inner and outer diameters of the bearing, and modulate the heating cycles to monitor the difference between these (a Best Practice) so as not to stress your bearing, a particularly valuable feature for expensive or high precision bearings. Always try to use one of these types of induction heaters if possible.

** Never use an induction heater that does not automatically fully demagnetize your bearing after the heating cycle has completed.

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by Bernd Seidenthal CRL