Understanding Bearing Failure AnalysisAll bearings have a predetermined life based on load, speed, operating conditions, and application. Our goal is to understand the reason a bearing may have failed prior to its expected life. Bearing failure analysis is the collection and analysis of data to identify the specific cause of bearing failure. This practice can prevent complete system breakdowns and inform the design of new bearing products. Knowing more about bearing failure analysis, when it’s needed, and how to perform it can help keep your operations running and ensure you’re using the right bearing products for your application.
When Is Bearing Failure Analysis Needed?Bearing failure analyses are conducted when customers submit bearings that have failed to us. The analysis is also done when developing or improving bearing designs and applications. This process involves determining the main cause of the failure and how to make the necessary repairs to prevent future bearing failure, saving the time and money that operations might otherwise lose due to downtime. According to machine designers, bearings should last for a certain number of hours based on the type of operation before experiencing normal failure. To prevent bearing failure and unscheduled downtime, it’s important to replace bearings before their expected normal life.
How to Perform a Bearing Failure AnalysisA bearing failure analysis follows these steps to gather data and identify the failure’s specific cause:
- Professionals conduct a visual examination of the bearing and assess its condition when disassembling it.
- A laboratory analysis examines oil samples and other types of particles embedded in the components.
- All relevant operating data—including bearing temperatures, oil outlet temperatures, vibration levels, and pressure levels—are evaluated.
- Experts identify any prior incidents that could have contributed to the bearing failure, along with histories of failure and recent operational changes.
- The process completes with a final analysis of the sequence of events causing the failure.
Common Reasons Why Bearings FailBearing failure can occur due to numerous reasons, which we detail below.
1. Insufficient LubricationOne common cause is a lack of lubrication, which leads to scraping between the rolling elements instead of a smooth gliding motion. This scraping generates heat that accelerates bearing failure.
2. Excessive LubricationConversely, too much lubrication might allow for gliding but result in grease churning, which also produces heat and increased energy losses. As a result, internal components such as the raceway and ball bearings experience wear. The service life of the lubricant should be matched to the service life of the bearing. For example, if a bearing has an expected life of 2,000 hours using standard grease, you can extend the life of the bearing by 10-20% if you use a higher-grade lubricant.
3. Contaminated Lubrication Causing Housing FailureFluid may leak into bearings if their mechanical seals experience failure. These fluids could include water and other substances that can render the bearings ineffective or unable to perform properly.
4. Internal ClearanceBearings may also have too much or too little internal clearance that results in friction and high temperatures, eventually causing failure. Too much clearance will cause excess metal-on-metal contact and bearing overload. Too little clearance will cause shafts to wobble and prevent bearings from working as intended.
5. OverloadingOverloading may cause failure and has several potential causes, such as fluids with an unexpectedly high viscosity, pumps operating away from their curves, and the presence of solids in the pumped fluid.
6. High TemperaturesMany of the same issues that cause overloading can cause overheating of parts, to the point where the units expel lubricants and result in failure. This risk makes it important to perform temperature checks when commissioning equipment.
7. MisalignmentComponents not designed to handle substantial stress may absorb uneven radial loads resulting from misalignment, leading to bearing failure.
8. Worn HousingAs the bearing’s housing wears down, the more room the bearing will have to move, potentially disrupting lubricant flow and leading to insufficient lubrication. To learn more about the reasons why bearings fail and types of failures, download our comprehensive “Bearing Failure Analysis” Guide. Visuals are also included to help you gain a thorough understanding.
Importance of Proper Bearing MaintenanceBearings remain one of the most important components to monitor with predictive maintenance. While these parts are inexpensive and smaller than other seemingly more important parts, their functionality is critical for maintaining operations. Bearings frequently experience wear because of their design and function, which means they demand more maintenance and care. Bearings need ample lubrication to maximize their service life and reduce the risk of breakdowns. You can keep your bearings functioning and replace them regularly with a solid maintenance schedule in place. Generally, you should get preventative maintenance for bearings with the following frequencies:
- Once per month for electric motor applications
- Once per month for shaft bearings
- Once every two months for support bearings
- Twice per month for cylinder head bearings