As a core component, the importance of bearings to equipment operation is self-evident. To ensure bearings operate smoothly and reach their expected service life, it is necessary to master the corresponding knowledge and skills in every aspect, from installation and adjustment to lubrication and disassembly. Today, we provide you with a comprehensive guide, summarizing all relevant knowledge about bearings.
Key Point 1: Rigorous Material Selection and Bearing Life Calculation
First, we need to start with the selection of bearing materials and the calculation of bearing life.
Good bearings depend on good steel—in fact, the steel used in bearings undergoes one of the most rigorous tests of steel performance. Only high-quality steel can help bearings withstand various harsh working environments, including high temperatures, extremely low temperatures, high speeds, and dust impurities. Simply put, the quality of bearing materials is mainly measured by the purity of the steel and the heat treatment process; these are prerequisites for judging a good bearing. For more information on bearing materials, please refer to: *The World of Materials*.
Life calculation is a crucial step in bearing selection. The actual service life of a bearing often differs significantly from its theoretical life due to external factors such as operating conditions, loads, and installation methods. Adjusted life, derived by modifying the theoretical life based on actual operating conditions, is more meaningful because it incorporates factors beyond reliability and material life coefficients, including operating condition life coefficients, foreign object life coefficients, load-bearing zone life coefficients, lubrication life coefficients, eccentricity life coefficients, and low-load life coefficients. At Timken, engineers utilize robust adjusted life calculation criteria and the specialized bearing analysis software Syber to accurately predict bearing life for customers. Combined with advanced finite element analysis technology, they quickly determine the bearing's service life and stress distribution, enabling the selection of the most suitable bearing for the application. Readers interested in materials science can refer to: "A Bonus Question for Engineers".
Knowledge Point 2: Bearing Installation and Adjustment
In addition to selecting high-quality bearings, reasonable fitting and clearance recommendations should also be provided.
Proper fit requires ensuring that there is no misalignment between relatively moving parts, while also avoiding over-tightening that could damage the shaft or bearings.
The size of the running clearance affects the smooth operation and heat generation of the bearing. If the running clearance is too small, there is a risk of excessive bearing preload, which can cause peeling of the roller surface or even jamming, as shown in Figure 1. If the running clearance is too large, it will increase the impact between the roller and the cage when the roller enters and exits the load-bearing area, which will accelerate the wear of the cage, as shown in Figure 2.
Figure 1 shows that excessive clearance caused severe peeling on the roller surface.
Figure 2 shows severe wear on the cage caused by excessive clearance.
To help customers select appropriate fit and clearance values, Timken engineers always communicate extensively with customers and even conduct on-site inspections to gain a deep understanding of the actual operating conditions of the bearings, and then use Timken's proprietary analysis software to perform precise calculations.
During actual installation, we remind customers to use appropriate installation methods based on bearing type and application conditions, employing specialized tools when necessary, and conducting post-installation inspection. Furthermore, there are various methods for adjusting clearance, including the push-pull method, Acro-Set™ method, Tor-Set™ method, Projecta-Set™ method, and Set-Right™ method. Timken can provide customers with guidance on the most suitable adjustment methods for different bearing applications or clearance setting ranges. Regarding bearing installation and clearance setting, we recommend two technical articles: "The Engineering Handbook for 'Putting an Elephant in a Refrigerator'" and "Mastering the Art in Millimeters."
Knowledge Point 3: Bearing Lubrication
The purpose of lubrication is to form a thin oil film between two relatively moving metal surfaces to prevent direct metal-to-metal contact. Insufficient lubrication between the contact surfaces will cause micro-peeling, as shown in Figure 3. If the insufficient lubrication persists for an extended period, the operating temperature will continue to rise, which can easily lead to component burn-out, as shown in Figure 4. Most bearing damage is caused by improper lubrication.
Figure 3 Insufficient lubricating oil film
Figure 4. Roller burns and discoloration due to increased temperature.
Insufficient lubrication film can be caused by a variety of factors. Therefore, Timken engineers will recommend appropriate lubrication methods and lubricants based on the actual application conditions. For detailed information on bearing lubrication, please refer to: "Lubrication, the Best Helper for Bearings".
On the other hand, Timken's bearing design also fully optimizes lubrication performance. For example, its unique high-performance self-aligning roller bearings feature a window-type stamped steel cage (as shown in Figure 6) that enhances the fluidity of the lubricating oil, reduces operating temperature, and extends bearing life.
Figure 5 Window-type stamped steel retainer
Knowledge Point 4: Bearing Disassembly
After a period of operation, bearings inevitably need to be disassembled for maintenance or repair. For clearance fits, disassembly is relatively simple and convenient. However, for interference fits (internal or external ring), depending on the size and type of bearing, it is crucial to use the correct disassembly method to avoid damage and ensure the safety of operators. Detailed disassembly procedures can be found in: "Practical Tips on Bearing Disassembly Techniques".
You can also seek help from Timken's service engineering team. They can recommend suitable disassembly methods based on the actual situation and provide disassembly tools if needed, such as flexible coil induction heaters, which can be used in situations where disassembly cannot be performed by simply pulling.
Knowledge Point 5: Bearing Protection
Finally, it's crucial to remember that bearings are precision mechanical parts, requiring a protected environment both before and after installation. Dust, impurities, or water entering the bearing's operating system can severely impact its performance. During the bearing's continuous operation, abrasive particles trapped between the rollers and raceways can cause abrasive wear, leading to pitting corrosion on the metal-to-metal contact surfaces, as shown in Figure 7. The presence of water reduces the viscosity of the lubricating oil, decreasing its lubrication effect. Water can also cause bearing corrosion when the equipment is shut down. Sealing is an effective way to protect bearings from impurities and water corrosion, and specialized seals can withstand high-temperature, high-speed operating conditions, ensuring the bearing's smooth operation. Figure 8 shows various sealing options offered by Timken.
Figure 6 Abrasive wear
Figure 7. Various sealing methods
summary:
Bearing operation is quite complex, and many factors can affect it. Therefore, a comprehensive consideration of these factors is necessary to ensure smooth bearing operation and achieve the expected lifespan. We hope this guide will help you select and use bearings correctly and troubleshoot problems promptly. You are also welcome to contact Timken engineers at any time for more detailed bearing usage precautions.
