Which type of bearing is more suitable for centrifugal pumps

The selection of centrifugal pump bearings depends on various factors, including the bearing’s load capacity, speed, stiffness, temperature, lifespan, maintenance requirements, and environmental conditions. The NU series cylindrical roller bearings and angular contact ball bearings used in the original design are both common choices in industry, each with its own characteristics: 1. Cylindrical roller bearings: They are typically used to bear high radial loads, but they are not suitable for bearing large axial loads. Their rolling elements are cylindrical, and the contact with the inner and outer raceways is linear, which enables them to provide a high radial load capacity. 2. Angular contact ball bearings: Can withstand both radial and axial loads. By adjusting the contact angle, the load capacity and stiffness of the bearing can be adjusted. Generally speaking, the larger the contact angle (such as 30 degrees), the greater the bearing’s capacity to withstand axial forces. However, an excessively large contact angle or inappropriate preload can lead to excessive bearing clearance, affecting the bearing’s operating accuracy and stability. In your case, the frequent damage and leakage of mechanical seals may be related to the stiffness and precision of the bearings. Due to the presence of the contact angle, angular contact ball bearings can indeed develop a relatively large axial play under certain conditions. If the bearing clearance is too large, it will cause increased shaft wobble, which in turn affects the performance of the mechanical seal, as mechanical seals are very sensitive to the radial and axial movements of the shaft. After switching to deep groove ball bearings, the leakage from the mechanical seal improved, likely because deep groove ball bearings generally possess good radial and axial stiffness, as well as the ability to withstand axial loads to a certain extent. The internal structure of deep groove ball bearings enables better control over the position of the shaft, reduces shaft wobble, ensures the stability of mechanical seals, and thus lowers the likelihood of leakage. Furthermore, deep groove ball bearings are usually easy to install and maintain, which also helps to ensure their proper installation and operational condition, thereby improving the reliability of the entire system. Therefore, it is not merely a matter of the contact angle of angular contact ball bearings; it may also involve various factors such as the setting of the bearing preload, the alignment of the shaft, the surface finish of the bearings, and the design of the sealing system itself. In practical applications, the selection of bearings also needs to be considered comprehensively in light of specific operating conditions and the design parameters of the pump. .

Monitor the vibration of the pump, as vibration has a significant impact on mechanical seals and can accelerate the wear of the rotating and stationary sealing rings； Another point is to avoid fluctuations in the pressure flow, as the start-up and stop-off of the pump have a significant impact on the machine seals.

It is recommended to check the smoothness of the contact surfaces of the rotor and stator seals, especially the smoothness of the surface where the rotor shaft comes into contact with the seal. Usually, during the operation of a new pump, it often suffers its first damage due to frequent startups or because the sealing water is not connected before startup. Most of these initial damages result in damage to the contact surface between the shaft and the mechanical seal; when it is reinstalled, if the smoothness of this area is not sufficient, it leads to a reduction in the lifespan of the equipment during the next usage cycle. Smooth the damaged surface of the shaft surface to extend its service life. Those with excessive damage need to be rewelded and turned to restore their original shape, for reference.

The clearance of the axial angular contact thrust bearing was not adjusted properly, and the axial movement caused damage to the seal. The original cylindrical roller bearings allow for axial movement; replacing them with deep groove ball bearings helps to control shaft play, but pumps with high power and heavy loads are prone to bearing damage.

Compared to angular contact ball bearings, deep groove ball bearings have lower assembly requirements. Within the load range, deep groove ball bearings are still the preferred choice.

Thank you for your reply; it was well explained