Analysis and measures of causes of bearing damage

Why are bearings damaged?
Bearings are precision parts, so they require considerable caution when using them. Even if high-performance bearings are used, if used improperly, the expected performance results will not be achieved, and the bearings will easily be damaged. Therefore, when using bearings, you should pay attention to the following matters:

1. Keep the bearing and its surrounding environment clean. Even if invisible dust enters the bearing, it will increase the wear, vibration and noise of the bearing.
2. Be careful when using and installing. Do not allow strong stamping, directly hit the bearing with a hammer, and do not allow pressure to be transmitted through rolling elements.
3. Use appropriate and accurate installation tools. Use special tools as much as possible, and try to avoid using things like cloth and short fibers.
4. Prevent bearing corrosion. When holding the bearing directly by hand, wash off the sweat on your hands and apply high-quality mineral oil before operating. Pay special attention to rust prevention during the rainy season and summer.
However, under certain special operating conditions, bearings can obtain a longer life than conventional calculations, especially under light loads. These special operating conditions are when the rolling surfaces (rails and rolling elements) are effectively separated by a lubricating oil film and limit possible surface damage caused by contaminants. In fact, under ideal conditions, so-called permanent bearing life is possible.
Bearing life
The life of a rolling bearing is defined in terms of revolutions (or the number of hours of operation at a certain speed): Bearings within this life should have initial fatigue damage (peeling or defects) on any of their bearing rings or rolling elements. However, whether in laboratory tests or in actual use, it can be clearly seen that bearings with the same appearance under the same working conditions have very different actual lifespans. In addition, there are several different definitions of bearing “life”, one of which is the so-called “operating life”, which indicates the actual life that a bearing can achieve before it is damaged. Damage is usually not caused by fatigue, but by wear and tear. Caused by wear, corrosion, seal damage, etc.
Why do bearings wear out?
Only some bearings are damaged in actual use. There are many reasons why most bearings are damaged – exceeding the originally estimated load, ineffective sealing, too small bearing clearance caused by too tight fit, etc. Each of these factors has its own specific pattern of damage and will leave specific traces of damage. Therefore, by inspecting the bearings of damaged shafts, the possible causes can be found in most cases. Generally speaking, one-third of bearing damage is caused by fatigue damage, and the other one-third is caused by poor lubrication. The other third is caused by contaminants entering the bearings or improper installation and handling. However, these damage patterns are also industry-specific. For example, in the pulp and paper industry, bearing damage is more likely to be caused by poor lubrication or contamination than by material fatigue.
Countermeasures
Damage Causes and Measures Excessive peeling load. Poor installation (non-linearity) moment load, foreign matter intrusion, water intrusion. Poor lubrication, inappropriate lubricant, and inappropriate bearing clearance. The accuracy of the bearing box is not good, the rigidity of the bearing box is uneven, the deflection of the shaft is large, and the development is caused by rust, erosion points, scratches and indentations (surface deformation phenomena). Check the size of the load and re-study the bearing used, improve the installation method, improve the sealing device, and prevent rust during shutdown. Use lubricants of appropriate viscosity and improve lubrication methods. Check the accuracy of the shaft and bearing housing. Check the clearance. When the bearing rotates under load, the raceway surface or rolling surface of the inner ring and outer ring will peel off like fish scales due to rolling fatigue. Stripping lubricants are not suitable. Foreign matter has entered the lubricant. Poor lubricant causes rough surface. The surface finish of mating rolling parts is not good. Lubricant selection improves sealing and improves surface finish of mating rolling parts. It shows a dark side with slight wear. There are many tiny cracks on the dark side with a depth of 5-10m from the surface to the inside, and micro peeling (micro peeling) occurs in a large range. It was hit during installation. The load is too large. Poor use such as falling. Improve installation methods (use thermal installation, use appropriate tool clamps). Correct loading conditions. The bearings are installed in place so that the ribs are supported. The so-called breakage refers to a small part breaking due to the impact or excessive load exerted on the flange of the raceway wheel machineor the local part of the roller angle. Jamming due to excessive load and excessive preload. Poor lubrication. Foreign object bites in. The inclination of the inner ring and the outer ring, and the deflection of the shaft. The accuracy of the shaft and bearing box is poor. Check the size of the load. The preload must be appropriate. Improve lubricants and lubrication methods. Check the accuracy of the shaft and bearing box. The so-called jamming damage is the surface damage caused by the accumulation of micro burns in the parts where the sliding surface damage occurs. Linear scars in the circumferential direction of the slide surface and rolling surface. The cycloidal scars on the roller end face are close to the jamming damage on the collar surface of the roller end face. Scratches, high speed, light load, rapid acceleration and deceleration, lubricant is not appropriate. Water intrusion, improve preload, improve bearing clearance, use lubricants with good oil film properties, improve lubrication methods, and improve sealing devices. The so-called scratches are tiny scratches on the raceway surface and rolling surface caused by rolling slippage and thermal cracking of the oil film. Surface damage that occurs as a result of burns. Produces surface roughness with adhesive. Cracks and fissures with excessive interference. Excessive load, impact load. Divestment has evolved. Heating and fretting wear due to contact between the raceway die casting wheels and mounting components. Heating due to creep. The taper angle of the taper shaft is poor. The cylindricity of the shaft is poor. The fillet radius of the shaft step is larger than the bearing chamfer, causing interference with the bearing chamfer. The amount of interference is appropriate. Check loading conditions. Improve installation methods.

The shape of the shaft should be appropriate. The so-called cracks refer to crack damage in the raceway wheel or rolling element. This will also include cracks where cracks will develop if used continues. Damage to the cage and poor installation (non-linearity of the bearing). Poor use. The moment load is large. Shock and vibration. The rotation speed is too high and there is rapid acceleration and deceleration. Poor lubrication. The temperature rises. Check the installation method. Check load, rotation and temperature conditions. Reduce vibration. Correct cage selection. Change lubricants and lubrication methods. Damage to the cage includes cage deformation, breakage, wear, etc. Damage to the column. Deformation of end face. Wear on the recessed surface. Wear of the guide surface. Foreign matter such as metal powder bites into the indentation. The impact load received during assembly or transportation is too large. Impact bushing. Improve sealing device. Filter the lubricating oil. Improve assembly and usage methods. The dents are formed on the raceway surface or rotating surface when small metal powder, foreign matter, etc. are bitten into the raceway surface. Due to impact during installation etc., concave surfaces (Brimnell hardness indentations) are formed at the intervals between the rolling elements. Wear, foreign matter intrusion, rust and electric corrosion cause development. Poor lubrication.

Slip due to irregular movement of rolling elements. Improve sealing device. Clean the bearing housing. Filter the lubricant thoroughly. Check the lubricant and lubrication method. Prevent non-linearity. The so-called abrasion corrosion causes wear of the raceway surface or rolling surface, roller end surface, collar surface and concave surface of the cage due to friction. Foreign objects bite during the lubrication process of pear skin points. Condensation due to moisture in the air. Poor lubrication. Improve sealing device. Filter the lubricant thoroughly. Use suitable lubricant. Weak luster, dark pear-like pitting on the raceway surface. Fretting wear and poor lubrication. Small amplitude rocking motion. Insufficient interference. Use appropriate lubricant. Add preload. Check for interference. Apply lubricant to mating surfaces. The wear caused by the relatively repeated contact between the two contact surfaces occurs at the contact portion between the raceway surface and the rolling elements. Due to the occurrence of reddish brown and black wear powder, it is called fretting corrosion. False Brinell indentation occurs due to vibration and oscillation of bearings during transportation. Swinging motion with small amplitude. Poor lubrication. During transportation, the shaft and bearing box must be secured by biting.

During transportation, the inner and outer rings must be packaged separately. Add preload to reduce vibration. Use appropriate lubricant. During the micro-vibration period, wear develops at the contact part between the rolling element and the raceway wheel due to vibration and shaking, resulting in imprints similar to Brinell indentations. Electric corrosion causes the ground potential difference between the outer ring and the inner ring. When setting the circuit, current must not flow through the bearing part. Insulate bearings. The so-called electric corrosion means that when electric current flows in the contact part of the bearing race wheel machine and the rolling element, sparks are emitted through the thin lubricating oil film, and local melting and unevenness appear on the surface. Insufficient creep interference or clearance fit. The adapter sleeve is not tightened enough. Check the interference amount and implement anti-rotation measures. Properly tighten the adapter sleeve. Study the accuracy of shafts and bearing housings. Axial preload. The raceway wheels are fastened laterally. Bonding mating surfaces. Apply lubricant to mating surfaces. The so-called creep means that when a gap is generated on the mating surface of the bearing, relative sliding occurs between the mating surfaces. The mating surface that creeps appears to be mirror bright or dark, and sometimes the page has jamming and wear. Discoloration and poor lubrication. Reaction with lubricant causes hot oil immersion. The temperature rises greatly. Improve lubrication methods. Due to temperature rise and lubricant reaction, the raceway wheels, rolling elements and cages will become discolored. Burns are poorly lubricated. Excessive load (excessive preload). The speed is too high. The clearance is too small. Intrusion of water and foreign matter. The accuracy of the shaft and bearing box is poor, and the deflection of the shaft is large. Research lubricants and lubrication methods. Correct bearing selection. Study fits, bearing clearances and preload. Improve sealing device. Check the accuracy of the shaft and bearing housing. Improve installation methods. The raceway wheels, rolling elements and cages heat up rapidly during rotation until they become discolored, softened, welded and damaged. Intrusion of rust, corrosive water, corrosive substances (paint, gas, etc.). Unsuitable lubricant. Water droplets are attached due to the condensation of water vapor. Stops when the temperature is high and humid. Poor rust prevention during transportation. The storage status is inappropriate. Inappropriate use. Improve sealing device. Research lubrication methods. Anti-rust measures during shutdown. Improve storage methods. Be careful when using it. Bearing rust and corrosion include pit rust on the surface of the raceway wheels and rolling elements, and comprehensive rust and corrosion. Installation scars, impact loads on the inner ring during installation and disassembly, and tilted installation and disassembly of the outer ring. Shock loads are prevented by using the press with the proper tools. Centering during installation