【Q&A Question 101】April 11, 2017

Improper material quality, inadequate manufacturing processes, wrong product selection, incorrect installation methods, excessive heating, excessive or insufficient clearance, improper use of lubricants, dirty or overheated oil with water content, excessively high or low ambient temperatures, excessive vibration, and excessive forces (axial and radial forces)

Lack of lubricant； High bearing temperature ；

Installation and adjustment, operation and maintenance, repair and upkeep

Answer: 1. Incorrect lubrication type； 2. Lack of lubricant inside the bearing ； 3. Excessive lubricant in the bearing ； 4. The external ambient temperature is too high ； 5. The bearing clearance is too small ； 6. Equipment vibration ； 7. Rotation of the bearing inner ring ； 8. The outer ring of the bearing rotates.

Factors affecting the service life of bearings: First, during the bearing selection phase, many factors need to be taken into consideration (such as load, hardness, operating environment, etc.). A good bearing design helps to ensure that the bearing reaches its maximum service life (refer to “Factors to consider in bearing design”). Second, proper storage is important; bearings should be kept in their original packaging before installation. It needs to be kept in a clean, dry environment with a relatively constant temperature. Rolling bearings should be kept away from dust, water, and corrosive chemicals. Shaking and vibration can permanently damage the mechanical properties of bearings; therefore, vibration should be avoided during handling and storage. Bears should generally be stored horizontally; some heavier bearings may deform due to their own weight if they are kept upright for an extended period of time. Additionally, special care must be taken with bearings that are coated with grease (or sealed), as the density of the grease can change over time as a result of storage. When a bearing is used for the first time, there will be a certain level of rotational noise. Therefore, the storage time for such bearings should be controlled according to the first-in, first-out principle! 3. Cleaning is very important for rolling bearings. The rotating surface of the bearing ring is extremely smooth and highly sensitive to damage caused by contaminants. Particle impurities can be excessively crushed by the rolling elements, generating localized pressure within the bearing, which ultimately leads to permanent material fatigue. IV. Complete reinstallation of the equipment: Bearings should be installed and removed carefully using appropriate tools (you can refer to the series of videos on bearing removal). The right tool should be chosen! Industry experts estimate that 16% of premature bearing failures are caused by incorrect installation. For large-scale installation, appropriate bearing installation equipment is generally used. However, during maintenance or replacement work, the environments can vary greatly! It is recommended that everyone carefully review the relevant drawings, maintenance manuals, and product instructions. The components of the bearing must also be kept absolutely clean! V. Install and remove the bearing carefully. The installation of bearings has been discussed many times before (if you have similar questions, there are some articles on bearing installation available); here is a brief summary again: 1. Do not apply any force during installation to the rolling elements, as this can easily lead to localized overloading at the contact surfaces between the rolling elements and the rings, thereby causing premature failure of the bearing. 2. Do not use any hard tools (such as hammers, screwdrivers, etc.; I have seen too many instances of these tools being used to force the installation, and it’s too aggressive) to strike the surface of the bearing, as this can cause the bearing rings to break or crack. 3. Generally, bearings are not removed from the equipment; only larger bearings are taken off for preventive maintenance. During disassembly, it is necessary to use the correct tools first, and ensure that adjacent components are not damaged! VI. Proper lubrication: Lubricants can isolate the surfaces of bearings, thereby reducing friction, protecting metal components, and preventing contamination and impurities. There are various types of greases available for use in different operating conditions. Due to excessive rotation of the rolling components, the bearing lubricant is subjected to prolonged mechanical stress; moreover, especially when exposed to high temperatures, humidity, or contaminated environments for long periods, the chemical properties of the lubricant change. All of these will lead to a decline in the quality of lubrication. Therefore, the bearings need to be relubricated regularly. The cycle is determined by the operating conditions.

Problems with the lubricating oil, overloading of the equipment, issues with the quality of the bearings themselves

There are usage factors and internal factors. The usage factors mainly refer to whether installation and adjustment, use and maintenance, as well as repair work meet the technical requirements. Installation conditions are one of the primary factors among those related to usage. Bearings often experience changes in the stress distribution among their various components due to improper installation, which causes them to operate under abnormal conditions and thus reach the end of their useful life sooner than expected. Internal factors mainly refer to the three key elements that determine the quality of bearings, namely structural design, manufacturing processes, and material quality. The role of raw material quality factors in bearing failure analysis has significantly decreased, but it remains one of the main factors contributing to bearing failures. Whether the material selection is appropriate remains a factor that must be considered in bearing failure analysis. The manufacturing of rolling bearings generally involves multiple processing steps such as forging, heat treatment, turning, grinding, and assembly. Among them, the heat treatment and grinding processes that affect the quality of the finished bearings are often more directly related to the failure of these bearings.

Rolling bearings have a short lifespan; apart from factors related to the bearing’s own quality； There are mainly the following aspects ； 1. Installation issues ； Rough installation, incorrect selection, significant dimensional errors in the journal and bearing housing. 2. Maintenance issues ； Lack of lubrication, dirty grease (oil), water or other contaminants, or temperatures in the operating environment that are too high or too low. 3. Operation issues ； There are issues with the precision of the equipment, excessive radial runout of the shafts or gears, and excessive axial force.

①The bearing housing is defective； ②Centerline movement ； ③Incorrect installation ； ④Improper fit between the shaft and the housing ； ⑤Poor lubrication ； ⑥Poor sealing; dust and moisture have entered ； ⑦Large vibration

Improper material quality, inadequate manufacturing processes, wrong product selection, incorrect installation methods, excessive heating, excessive or insufficient clearance, improper use of lubricants, dirty or overheated oil with water content, excessively high or low ambient temperatures, excessive vibration, and excessive stress