1. The grease has impurities;

　　2. Insufficient lubrication (the oil level is too low, improper storage causes oil or grease to leak through the seal);

　　3. The clearance of the bearing is too small or too large (factory problem);

　　4. Impurities such as sand or carbon particles are mixed into the bearing, which acts as an abrasive;

　　5. The bearing is mixed with water, acid or paint and other dirt, which has a corrosive effect;

　　6. The bearing is flattened by the seat hole (the roundness of the seat hole is not good, or the seat hole is not twisted straight);

7. The pads on the bottom surface of the bearing seat are not flat (resulting in deformation of the seat hole or even cracks in the bearing seat);

8. There are debris in the bearing seat hole (remaining chips, dust particles, etc.);

9. The seal ring is eccentric (touches adjacent parts and rubs);

10. The bearing is subject to additional load (the bearing is axially tightened, or there are two fixed end bearings on one shaft);

11. The fit between the bearing and the shaft is too loose (the diameter of the shaft is too small or the adapter sleeve is not tightened);

12. The clearance of the bearing is too small, and the rotation is too tight (the adapter sleeve is over-tightened);

13. The bearing is noisy (caused by the slippage of the end face of the roller or the steel ball);

14. The thermal elongation of the shaft is too large (the bearing is subjected to static indeterminate axial additional load);

15. The shaft shoulder is too large (it hits the seal of the bearing and rubs);

16. The shoulder of the seat hole is too large (the seal of the bearing is distorted);

17. The clearance of the labyrinth seal is too small (friction with the shaft);

18. The teeth of the lock washer are bent (it hits the bearing and rubs);

19. The position of the oil throwing ring is not suitable (it touches the flange cover and rubs);

20. There is a pressure pit on the steel ball or roller (caused by hitting the bearing with a hammer during installation);

21. The bearing is noisy (with external vibration source interference);

22. The bearing is discolored and deformed by heat (caused by using a spray gun to heat and disassemble the bearing);

23. The shaft is too thick and the actual fit is too tight (causing too high bearing temperature or noise);

24. The diameter of the seat hole is too small (causing the bearing temperature to be too high);

25. The diameter of the bearing seat hole is too large, and the actual fit is too loose (the bearing temperature is too high - the outer ring slips);

26. The bearing seat hole becomes larger (the non-ferrous metal bearing seat hole is enlarged, or becomes larger due to thermal expansion);

27. The cage is broken.

28. The bearing raceway is rusted.

29. Steel balls and raceways are worn (unqualified grinding or products are bruised).

30. The raceway of the ferrule is unqualified (the problem of the manufacturer)