Selection of Spherical Roller Bearing Clearance: Fine Considerations and Practical Applications

May 13, 2024

As a key component in modern industrial machinery, the performance of spherical roller bearings directly affects the operating efficiency, service life, and safety of the equipment. Among the many performance indicators of spherical roller bearings, the selection of clearance is particularly important. Clearance, that is, the size of the internal gap of the bearing, is not only related to the smooth operation and load-bearing capacity of the bearing but also closely related to its service life and noise level. Therefore, how to reasonably select the clearance of spherical roller bearings has become a problem worthy of in-depth discussion.

Basic concepts and classification of clearance

Clearance refers to the relative displacement between the inner and outer rings of a bearing when external forces do not act upon it. According to the size and nature of the clearance, it can be divided into two types: radial clearance and axial clearance. Radial clearance refers to the displacement of the bearing's inner ring relative to the outer ring in the radial direction. In contrast, axial clearance refers to the displacement of the bearing in the axial direction. In practical applications, our main concern is the selection of radial clearance.

Factors affecting clearance selection

1. Load and speed: Load size and speed are important factors that affect the selection of clearance. Generally speaking, bearings that bear larger loads or rotate at higher speeds should choose smaller clearances to ensure the stability and load-carrying capacity of the bearings. On the contrary, for bearings with smaller loads or lower speeds, the clearance can be appropriately increased to reduce friction and wear.

2. Operating temperature: Bearings will generate heat during operation, causing the bearing temperature to rise. The high temperature will cause thermal expansion of the bearing material, thereby changing the size of the clearance. Therefore, when selecting the clearance, the operating temperature range of the bearing needs to be fully considered. Bearings working in high temperature environments should choose larger clearances to avoid failures caused by too small clearances due to thermal expansion.

3. Fitting accuracy: The fitting accuracy between the bearing, shaft, and bearing seat will also affect the selection of clearance. If the fit accuracy is high and the space between the inner and outer rings of the bearing and the shaft and bearing seat is small, a smaller clearance should be selected at this time. On the contrary, if the fit accuracy is low and the gap between the inner and outer rings of the bearing and the shaft and bearing seat is large, the clearance can be appropriately increased.

4. Accuracy requirements: Different mechanical equipment have different accuracy requirements for bearings. For equipment with higher accuracy requirements, such as precision machine tools, measuring instruments, etc., a smaller clearance should be selected to ensure the accuracy and stability of the equipment. For equipment with lower accuracy requirements, the clearance can be appropriately increased.

The picture above is the double-row spherical roller bearing 24024CCW33 C3 stamped steel cage C3 clearance produced by FV.

Methods and steps for clearance selection

1. Understand the usage conditions and requirements of the bearing: Before selecting the clearance of the spherical roller bearing, you must first understand the usage conditions and requirements of the bearing, including load size, speed, operating temperature range, fit accuracy, accuracy requirements, etc. These conditions and requirements will directly affect the selection of clearance.

2. Determine the preliminary range of clearance: Based on the use conditions and requirements of the bearing, the range of clearance can be preliminarily determined. Generally speaking, the appropriate clearance range can be selected according to the accuracy grade and load size of the bearing. For example, for high-precision bearings and bearings that bear larger loads, a smaller clearance range should be selected, while for low-precision bearings and bearings that bear smaller loads, the clearance range can be appropriately increased.

3. Consider the impact of operating temperature: After determining the preliminary range of clearance, the impact of operating temperature on clearance also needs to be considered. Since the bearing generates heat during operation and causes thermal expansion, the clearance needs to be adjusted based on the operating temperature range of the bearing. For bearings operating in high-temperature environments, the clearance should be appropriately increased to compensate for the effects of thermal expansion.

4. Select an appropriate clearance value: After considering the above points, you can select an appropriate clearance value according to the actual situation. Generally speaking, the appropriate clearance value can be selected based on the bearing's manufacturing standards and usage experience. At the same time, you can also refer to the clearance selection guide provided by the bearing manufacturer or consult professionals to determine the final clearance value.

5. Conduct actual testing and adjustments: After selecting the appropriate clearance value, actual testing and adjustments are required. The rationality and effectiveness of the selected clearance value can be verified through actual testing, and appropriate adjustments can be updated based on the test results. Suppose the selected clearance value is too small or too large, causing problems such as unstable bearing operation or reduced load-carrying capacity. In that case, the clearance value needs to be adjusted in time to ensure the smooth operation of the bearing.

The picture above is the spherical roller bearing 24144MBW33 C2 customized by FV for customers with brass cage C2 clearance.

4. Summary

The selection of spherical roller bearing clearance is a complex and important process that requires comprehensive consideration of many factors. To select the ideal clearance value for a bearing, you need to understand its operating conditions, determine a preliminary clearance range, consider the impact of temperature, choose the appropriate clearance value, and test it to ensure its effectiveness, thereby ensuring the stable operation of the bearing and extending its service life. At the same time, it is also necessary to continuously learn and accumulate experience to improve the accuracy and reliability of clearance selection.