VISTA Technology Knowledge: Causes and Prevention of Premature Failure of Rolling Bearing

The failure causes of rolling bearings will be studied and corresponding solutions will be found to avoid premature failure of bearings and prolong the service life of rolling bearings.

Rolling bearings are often used in industrial and agricultural production. Their working state is directly related to the normal use of mechanical equipment and the service life of the whole machine. Although the bearings are selected according to sufficient safety degree in design, a considerable part of rolling bearings fail when they are far from reaching the design life, affecting the normal operation of the equipment.

The failure forms of rolling bearing mainly include fatigue pitting corrosion, plastic deformation and wear. In addition, there are gluing, cage fracture, outer ring fracture, rolling element crushing, corrosion, etc. Next, the failure causes of bearings will be studied and corresponding solutions will be found to avoid premature failure of bearings and prolong the service life of rolling bearings.

1. The Causes of Premature Failure of Bearing

There are many reasons for premature bearing failure, but the most important is improper use and protection. The most common are poor bearing lubrication, pollution, serious overload, improper assembly, impact and impact during transportation or loading and unloading.

1.1 Poor lubrication

The viscosity of the oil is too low to fully lubricate, which will wear the seat ring quickly. The discoloration of raceway and steel ball is the initial sign of lubrication failure caused by the loss of lubricating oil (grease) or high temperature, followed by serious wear accompanied by overheating. The higher the speed, the more serious the heating and wear.

1.2 Pollution

Most of the bearings used on the machine work under dusty conditions. Although the sealing device is adopted, impurity particles often enter the bearing, causing dents on the surface of the seat ring, which will expand fatigue pitting and cause failure. At this time, the entire seat ring surface will be dented. More serious is the pollution of lubricants. After the lubricant is polluted, it is difficult to check. Some solid impurities are mixed in the lubricant and become an abrasive. If the pollution is serious, the bearing will wear out prematurely.

1.3 Improper assembly

The angular error between the center line of the bearing hole and the center line of the shaft will make the rolling element separate from the normal raceway and distribute on the non-circular raceway. The greater the angle error, the greater the additional torque to the bearing, the more “force”, and the easier it is to cause premature failure of the bearing. The reasons for centerline misalignment are as follows.

(1) The position of bearing or shoulder is out of tolerance.

(2) Improper fit tolerance between shaft and bearing hole.

(3) The center lines of the holes between the bearing seats are not aligned.

At the same time, if the inner and outer seat rings are knocked too hard during installation, the seat rings will be pressed into dents by the rolling elements. The greater the external load, the greater the rolling pressure. After several times of impact, sheet fatigue pitting corrosion occurs at the indentation. In addition, raceway indentation can produce noise, vibration and additional torque.

There is a small interference between the inner and outer rings of the bearing, which must be strictly controlled. Excessive interference will lead to assembly difficulties, excessive prestress, heating, early damage and other faults, and even direct damage to the bearing. If the interference is too small or there is a gap, it will cause looseness and wear, the inner and outer rings will rotate relative to the mating parts, and the mating parts will be damaged.

1.4 Overload overheating

If the bearing is overloaded, the bearing steel ball raceway will be seriously worn, spalling in a large area and sometimes accompanied by overheating. If the clearance between the rolling element of the bearing and the inner and outer raceways is too small and the lubrication is poor, the bearing will also overheat. Bearing overheating will cause locking. In a period of time before locking, excessive wear and high heat will soften the bearing steel, cause the volume expansion of various parts in the bearing, and squeeze each other more and more until the bearing “locks”. Overheated bearings are often accompanied by a smaller gap between the raceway of the inner and outer rings, the rolling element and the cage, and the friction will also produce stress on the cage, which may break the cage and accelerate the failure of the bearing.

1.5 Vibration erosion

When the bearing acts with external load and does not rotate, the external vibration makes the rolling body in the bearing vibrate, resulting in elliptical indentation on the raceway of the inner and outer rings of the bearing. This kind of situation often occurs in the process of equipment transportation or the vibration caused by external factors when the equipment is not working, which eventually leads to fatigue pitting corrosion of the raceway. The small pit of the raceway also acts as the starting point of corrosion and invalidates the whole bearing.

1.6 Corrode

If the bearing is exposed to corrosive liquid or gas, red or brown stains will appear on the whole bearing, causing corrosion failure of the bearing.

2. Methods to avoid premature failure of bearing

1. Good lubrication is one of the important conditions to avoid bearing failure and prolong its service life. Good lubrication can not only improve the stability and accuracy of movement, but also absorb vibration, buffer and reduce wear. The viscosity of lubricating oil must be carefully selected. If it is too viscous, it will increase the resistance. Too thin selection will affect the lubrication effect. What kind of lubrication method, grease or oil, should be adopted depends on its specific working conditions.

2. The pollution of bearings and lubricants is unavoidable in some industrial production, especially in the industrial production of building materials industry. Through practical investigation, it is found that 50% of the failed rolling bearings in the building materials industry are caused by pollution. Usually, the protective cover or sealing strip is used to prevent the invasion of dust and dirt. However, since the inner ring and outer ring of the bearing move relatively, it is impossible to have a perfect sealing device. Therefore, the pollution of lubricant is inevitable. In order to prolong the service life of the bearing, pay attention to cleaning when assembling and disassembling the bearing. In the process of use, ensure that the bearing has a good working environment.

3. Reasonable bearing assembly is also very important to avoid bearing failure and prolong bearing life. The key to the assembly of bearings is whether the assembly method is appropriate and whether the appropriate clearance and clearance can be guaranteed. Similarly, there are method problems when disassembling the bearing. If it is not disassembled properly, it will cause indentation on the raceway if it is light, and the bearing will be scrapped if it is heavy. During the assembly and disassembly of the bearing inner ring, the inner ring shall be stressed, and the outer ring shall be stressed during the assembly and disassembly of the bearing outer ring. In addition, during bearing assembly, if the axial clearance is too small, the additional torque will increase, the angular displacement between the bearing centerline and the bearing hole centerline will be too large, and the working state of the bearing will be deteriorated. These should be avoided in practical work.

4. Excessive load or excessive initial load will cause premature fatigue of bearing materials. If the cause of bearing failure is overload, bearings with high bearing capacity should be used. In addition, the sudden overload in the work will cause fatigue pitting corrosion of the bearing, which should be avoided as far as possible. If unavoidable, the actual service life of the bearing shall be carefully calculated according to the actual situation in order to formulate the bearing maintenance plan.

5. In order to avoid bearing failure caused by vibration corrosion, eliminate the seismic source and keep the bearing well lubricated. Add isolation pads or separate the foundations of mechanical equipment from each other. Reduce vibration caused by the environment. A light initial load is applied to the bearing to keep the rolling elements of the bearing in close contact with the raceway and improve the anti-vibration ability.

More about VISTA High quality Rolling Bearing：

Rolling bearings support and guide rotating or oscillating machine elements – such as shafts, axles or wheels – and transfer loads between machine components. They provide high precision and low friction and therefore enable high rotational speeds while reducing noise, heat, energy consumption and wear. Rolling bearings are cost-effective and exchangeable machine elements that typically follow national or international dimension standards. VISTA rolling bearings include tapered roller bearings, spherical roller bearings, cylindrical roller bearings and so on.

Vista Bearing as a leading global supplier of high quality ball and roller bearings, will be your best choice for better support your machinery high efficiently run.

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