Sunday, 10 January 2016

INDUCTION HEATERS FOR BEARINGS INSTALLATION

INDUCTION HEATERS FOR BEARINGS INSTALLATION

One of my readers had asked me one question that we want to install a bearing with tight fit of the bearing inner ring with the respective shaft bearing sheet, how to secure such installation of bearing with respective shaft bearing sheet.

 
There are so many engineering applications, where we need tight fit of bearing inner ring with respective shaft bearing sheet or we need tight fit of outer ring of bearing with bearing housing. I have attended one training session, from Timken bearing, few years ago and they have explained this concept very precisely.

We can easily secure the tight fit of bearing inner ring with respective shaft bearing sheet or outer ring of bearing with bearing housing by heating the bearing with bearing heating methods that we will see here in this post.

In order to install small bearing, we will require small mounting force but as bearing size increases we will require more mounting force for mounting the bearing to its desired position. In order to secure the tight fit mounting of bearing we will use the principle of expansion of metal due to heat.

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Smaller size of bearing heating

In order to heat the bearings of smaller size, we can use the bearing induction heater. Bearing induction heater working principle is quite similar with electric transformer. Core and winding of induction heater will be considered as primary coil where as the work piece, bearing in this case which is being heated, will be considered as short circuited secondary coil. Induction bearing heated is displayed here in following figure.
Induction bearing heater
Image Courtesy: Google

When an AC current will be provided to the primary coil, there will be created one alternating magnetic field and as per principle of faraday there will be induced an eddy electric current if secondary coil is placed within the magnetic field. This eddy current will flow against the metal electrical resistivity and simultaneously will produce localized & precise heat and we must note it here that there will not be any direct surface contact between the workpiece and inductor.

We can easily heat the bearing in few minute and we must have to note it here that heat will be provided here only to workpiece and induction heater will be at ambient temperature and hence we can touch the heater at any time without any issue with human safety. Non metallic components for example sealing or lubricants will not be heated here.

You might be thinking that up to what temperature, we should heat the bearing. We should heat the bearing up to 110 degree centigrade. We must have to avoid the temperature above 120 degree centigrade as it can cause several structural changes in bearing material.

 
By considering the safety against heat, we must have to use heat resistant hand gloves to mount the hot bearing to its desired position and we will have to hold in that position until tight fit is secured.

Advantages of bearing induction heating

There are various advantages of induction heating as mentioned here
  1. Good service life
  2. Less consumption of time in heating the bearing
  3. Environmental friendly
  4. Energy efficient
  5. Suitable fitting
  6. Simple operation and simple set-up
  7. Safe in operation with specified using of PPE

Larger size of bearing heating

 
If we are interested to mount a bearing of large size with tight fit with respective shaft bearing sheet, we can easily heat the bearing in a container filled with oil i.e. oil bath. We will have to take care that surface of bearing should not touch the bottom or side surface of container. In order to avoid any direct surface contact of bearing with container, we will have to use one platform over which we will keep the bearing as shown in following figure.

Bearing heating in oil bath
Image Courtesy: Google

Do you have suggestions? Please provide your suggestions in comment box so that we can make this platform to secure various engineering information’s.

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