The life of a rolling bearing refers to the number of turns or working hours experienced from the beginning of use to the first appearance of fatigue spalling under rotating conditions. The contact fatigue is random and the bearing life follows Weibull distribution law. Based on this distribution, we can determine a certain range of bearing damage rate distribution as the calculation standard of stress cycles of rolling bearings. For example, a bearing failure rate of 10% is often used as a calculation standard. If a particular industry requires higher reliability, a lower failure rate, such as 1%, can be used as a calculation criterion. To better understand this concept, assume that 100 identical centrifugal pumps are equipped with 100 identical sets of bearings and operate under similar conditions. If after 10,000 hours of operation, a set of bearings fails (99% of bearings do not fail), then it can be said that L01 = 10,000 hours; If 10 sets of bearings fail after 30,000 hours (90% of bearings do not fail), then L10 = 30,000 hours. Bearing manufacturers and industry associations have found through many years of failure investigations of a large number of bearings that the 90% reliability criterion usually avoids typical fatigue spalling failures, thereby providing a robust and reliable bearing solution. This is the origin of the often said L10 life. Bearing reliability factor Bearing reliability comes from three aspects: Bearing manufacturers: To ensure that the design of bearings (force, speed, structure, cage, lubrication, sealing, etc.), materials (high purity steel), manufacturing (strength, hardness, accuracy, etc.) and transportation and storage meet high standards. OEM manufacturers: Ensure that bearings are properly selected and designed to ensure adequate lubrication. Unit of use: Ensure the correct installation of bearings, correct lubrication and good maintenance. Factors affecting bearing life during use In the use stage, the reliability of bearings is mainly related to the application environment and working cycle. According to statistics, only a few bearings can reach the fatigue limit (that is, the catalog life), and usually only 10% of rolling bearings can reach the L10 life (according to the definition should be 90% can reach this life). In order to ensure that bearings have a normal life expectancy, we need to avoid the following causes of failure: Mechanical reasons: Exceeding the rated dynamic load capacity of the bearing will significantly reduce the fatigue life of the bearing. For most bearings, doubling the bearing load will reduce the normal life of the bearing by about one-eighth. Improper and unbalanced installation can have a similar effect. Wrong lubrication: Using the wrong lubricating oil, degraded lubricating oil, mixing incompatible lubricating oil or contaminated lubricating oil can lead to reduced lubricant performance. Lubrication pollution: pollutants such as particles and water are the main reasons for shortening bearing life. High temperature operation: Overheating is a common cause of lubrication and mechanical problems. For example, excessive lubrication can cause grease lubricated bearings to heat up. Insufficient lubrication: After the bearing runs for a long time, the lubricating oil or grease will dry up and must be properly re-lubricated. Incorrect re-lubrication intervals are often the number one cause of inadequate lubrication, but cold starts, dry starts, and lubrication leaks can also cause inadequate lubrication. conclusion In order to ensure that the bearing has a normal life expectancy, it is necessary to ensure that the above failure causes will not occur at any time after installation and commissioning. This includes avoiding excess loads, ensuring proper lubrication, preventing contamination, controlling temperature, and regularly replenishing lubrication. Through these measures, the reliability and service life of bearings can be significantly improved.
