The improper selection of bearings is mainly due to not using thrust bearings or bearing support structures that can withstand combined radial and axial loads when there is a large axial load. It is inappropriate to only use cylindrical roller bearings without cages. Poor lubrication of SKF bearings is the direct cause of bearing damage, analyzed from the current situation of damaged bearings. After a cumulative working time of 3000 hours, the rolling working surface of the imported bearing showed no fatigue damage, and the bearing only showed scratches. The fatigue life of the bearing calculated based on radial load is very long.

According to observation, the material structure at the fracture surface of the bearing is fine and there is no occurrence of coarse grains. The fracture surface is silver gray and belongs to brittle fracture. There is no obvious wear or material adhesion burn on the inner raceway of the bearing. However, obvious wear and scratches were found on one side of the inner ring guard edge of the bearing. The main reason is that on both sides of the main crack on the inner ring guard edge, visible cracks were found on both sides of the SKF bearing, and some areas of the material turned blue. There were no abnormalities on the side of the inner ring guard edge of the imported bearing.

Limitations on bearing size.

The space that bearings can usually be installed is limited. In most cases, the shaft diameter (or bearing inner diameter) is limited by mechanical or other design considerations. So the selection of bearing type and size is determined by the inner diameter of the bearing. Therefore, the main dimension tables of standard bearings are compiled based on international standard inner diameter dimensions.

Classification of the second bearing.

Based on the classification of bearings, an analysis was conducted on the industries that may use imported bearings. The key issue is to determine the key industries to focus on based on the actual situation of the company's stock preparation.

Installation of bearings: The installation of SKF bearings must be carried out under dry and clean environmental conditions. Before installation, the mating surface of the shaft and housing, the end face of the shoulder, the groove, and the machining quality of the connecting surface should be carefully checked.

Generally, equipment with high-speed operation and high precision requires bearings to ensure normal speed and high precision, as well as reduce maintenance costs.

Usually, a shaft is supported by two bearings in both radial and axial directions. The SKF bearing on one side is called a fixed end bearing, which bears both radial and axial loads and plays a role in fixing the relative axial displacement between the shaft and the bearing housing. The other side is called the free end, which only bears radial loads and can move relatively axially.

Fixed end bearings must be fixed to both the shaft and bearing housing. The most suitable bearings are radial bearings that can withstand composite loads, such as deep groove ball bearings, self-aligning roller bearings, and double row or paired angular contact ball bearings or tapered roller bearings. A combination of radial bearings that can withstand pure radial loads, such as cylindrical roller bearings without retaining edges on the inner and outer rings, can also be used as fixed end bearings when combined with deep groove ball bearings, four point contact ball bearings, or bi-directional thrust bearings. At this point, the second bearing provides bidirectional axial positioning, but it must be installed with a certain radial distance from the bearing housing. When the length of the free end bearing changes due to thermal expansion of the shaft, there will be no compression inside the imported bearing. Axial displacement can occur inside the bearing, as well as between the bearing ring and the bearing seat.

"Cross fixed" refers to an imported bearing configuration where each SKF bearing positions the shaft in a unidirectional direction, with opposite directions. This combination is mainly used for short axes. All radial bearings that can withstand axial loads in at least one direction are applicable, including deep groove and angular contact ball bearings, tapered roller bearings, and NJ cylindrical roller bearings. When using angular contact ball bearings or tapered roller bearings, preloads must be applied in certain situations.