Trouble shooter

Published:  06 March, 2015

For large-size rolling bearings with outside diameters above 1500mm, what type of heating methods are available for mounting/dismounting and which is the most suitable?

Answer:

A variety of heating methods are available, each with their advantages and disadvantages.

Using an oil bath requires a large enough bath for the bearings to be heated in. If one does not exist, it will have to be constructed, which is time consuming and costly. Uniform heating of the oil is a problem and there will be difficulties in handling a large, oily bearing at 120oC. Hundreds of litres of oil are also needed, which must then be properly disposed of. An oil bath is also a potential fire risk.

Gas flame burners require only a couple of gas cylinders and a burner. However, this method needs a highly skilled operator(s) to evenly heat up the bearing with a soft flame, which may tie up 3 or 4 people for up to four hours per bearing. There is also a risk of local overheating, which can cause changes to the structure of the bearing, with adverse effects on hardness, dimensional stability and operating life.

Fixed or mobile induction heaters are faster, cleaner and more suitable for batch heating. Heat is transferred directly and uniformly to the bearing. Due to their increased energy efficiency, induction heaters can reduce heating times by up to 50%.

For large-size rolling bearings, flexible induction heating is the most suitable method. The heating cable is flexible and so can be placed in and around the bearing or in areas that would normally be inaccessible. Heating time is only 1-2 hours. The heating process is automatic and the bearing does not require cleaning post-heating.

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