Some bearings do not need to be lubricated during use, which is called oil-free lubricated bearings. However, many bearings need to be lubricated and maintained during use, and whether the lubrication is proper is also very important. If you lubricate the bearing, but do not do it properly, it is the so-called ineffective lubrication, which will bring many disadvantages to the bearing.
Rolling bearings are a type of mechanical element that is widely used in mechanical transmission. Their movement is mainly rolling and sliding friction. Friction can cause local thermal deformation, accelerate the wear of the parts surface, increase the operating error, and even make the spindle scrapped.
The causes of bearing failure are often multifactorial. All factors affecting the design and manufacturing process are related to the failure of the bearing. Analysis of the causes of bearing damage shows that about 40% of bearing damage is related to poor lubrication.
Four major drawbacks of ineffective bearing lubrication
(1) Color change
Metal-to-metal contact can cause bearing temperatures to rise excessively, resulting in discoloration of the raceways and rollers. In mild cases, this discoloration is due to lubricant contamination of the bearing surfaces, while in severe cases, the metal is discolored due to the high temperatures. In all cases, early detection can avoid costly repairs.
Discoloration due to lubricant contamination of the bearing surface
(2) Scratches and peeling
Check the bearings for cuts into the metal or metal spalling - these conditions require immediate attention. Scoring and spalling are more likely to occur in high-load, low-speed applications or under sustained high temperatures, and thin or insufficient lubricant films can accelerate the onset of the problem. Inadequate lubrication, incorrect grease selection or sudden changes in operating conditions can cause bearing material to spall or the bearing ribs to score.
(3) Roller overheating
Lubricant film breakdown can lead to direct contact between components and thus localized scoring. In tapered roller bearings, this may appear as scoring on the roller big end and the guide rib. Thermal damage to tapered rollers due to metal-to-metal contact
(4) The bearing is completely locked
Extreme localized heating can create metal flow in the bearing, changing the original bearing material and geometry. This can lead to excessive roller tilting, cage damage, and complete bearing locking. If catastrophic damage does occur, it is recommended to consult a bearing expert to determine the root cause of the problem, as factors other than lubrication may be to blame.
The role of bearing lubrication
When the bearing is working, in order to ensure the effective and reliable operation of the bearing, it must be fully lubricated. The role of bearing lubrication:
Prevent or reduce direct metal contact between rolling elements, raceways and cages in bearings, and reduce friction and wear;
An oil film is formed on the friction surface. When the pressure oil film is formed, the contact bearing area of the parts can be increased, thereby reducing the contact stress and extending the rolling contact fatigue life.
Lubricants have anti-rust and anti-corrosion effects
Oil lubrication also has the function of dissipating heat and taking away wear particles or intrusive contaminants generated during bearing operation;
Grease lubrication can increase sealing and prevent the intrusion of external pollutants;
It has a certain effect of reducing vibration and noise.
Damage caused by ineffective bearing lubrication can vary widely in appearance and in the effects on bearing performance. In all cases, the grease quantity, type, grade, viscosity, additives and delivery system must be properly designed for the bearing system. Grease selection should be based on historical experience, loads, speeds, sealing systems, service conditions and expected life. If these factors are not properly considered, bearing performance and application results may be less than expected.
