Machines and their Bearings
Bearings, although they may be the smallest, are undeniably the most important component in many machines. If a machine fails due to its bearings the result of repair can be very time consuming and very costly for the supplier. Bearing failure seems like a whole subject to its own and it really is, the precision of bearings needs to be so exact that even the slightest bit off means a whole machine will break down or won’t work properly. In essence the life of a bearing should outlive that out of the machine but due to external stimuli this is usually not the case. When a machine breaks down or fails and it is due to the bearings an analysis is undergone and documented. This is so the manufacturer can aim to eradicate the problem from happening again and they can track backwards if need be.
Why Bearings Sometimes Fail
Reasons for bearing failure can be categorized under many different titles for example track markings, fatigue failure, premature fatigue, fitting damage, lubrication failures, loss of internal clearance, wear, fretting damage, manufacturing defects, overheating, excessive loads, true and false brinelling, reverse load, and electrical damage, and there are many more.
Let’s look at a few of these in more detail:
Bearings that Overheat – when the temperature of a bearing exceeds 400 F the bearing becomes less hard and reduces the bearing capacity causing it to fail. If the temperature rises to extreme degrees the bearing can become disfigured and may destroy the lubricant as well. How can you tell if a bearing has overheated? The bearing and the rings are discoloured from gold to blue.
Bearing Corrosion – corrosion simply means rusting of the bearing. If water or any other corrosive agents gets inside of the bearings or the rings then the bearing will rust. If rusting is present the lubricant does not work effectively and finally will cause the bearing to fail. How can you tell if corrosion has taken place? You’ll be able to see grey / black streaks across the raceways.
Fatigue Failure – sometimes referred to as spalling – means a fracture of the bearing components and the removal of small particles. Once a little fracture has taken place then it will spread a lot faster. You can usually tell a fracture has taken place because there is an increase in the vibration.
