Many people who deal with machinery on a regular basis are at a loss when it comes to the overeating of bearings, not knowing what causes the issue or how they can best prevent it. Luckily, this is a problem that is fairly simple to rectify once you know a bit more about the situation.
How does it happen?
The overheating of bearings is typically caused by fluid friction due to fluid churning. This is a secondary consequence of a cavity that has been overfilled during relubrication. One of the simplest things that can be done to help in this situation is to install a relief vent port. However, this will only tackle the symptom of the problem and not its root cause.
If you truly want to get to the bottom of your overheating problem, then you will need to look critically at your current relubrication practices. Although traditional guidelines for relubrication can often be right, the fact that your bearings are overheating would suggest that something is off.
What you need to do is calculate the amount and frequency of lubrication, taking into consideration the type of bearing used, as well as speed and relevant factors in the operating environment. By working out the right interval and volume for each relubrication, you can avoid overfilling the housing. There are a number of freely available formulas that will enable you to do this with ease.
Choosing your lubrication
The other thing that you will need to look at if you want to avoid unnecessary bearing overheating is your lubricant selection process. You need to know that the viscosity requirement of a lubricant goes down as the speed of bearings increase, and that the viscosity of oil goes down with temperature. This means that it is extremely important that you should choose a lubricating grease based on the bearing manufacturer’s recommendations for any given application.
This recommendation is typically based on the formula: NDm = Speed in rpm * ((bearing bore + bearing outside diameter) / 2).
Relubrication guidelines issued by bearing manufacturers are very specific in terms of minimum oil viscosities, and you should do everything you can to ensure that the lubricant you choose, whether from Fuchs, Mobil or elsewhere, meets the recommended viscosity level with a minor cushion to ensure smooth running.