Deep groove ball bearings are widely used in rotating machinery and are also one of the easily damaged components. Many faults in rotating machinery are related to rolling bearings, and the quality of the bearings has a great impact on the working state of the machinery. Their defects can cause abnormal vibration and noise in the equipment, and in severe cases, even damage the equipment. Proper monitoring and diagnosis of the condition of rolling bearings is an important aspect of equipment optimization management and predictive maintenance in modern enterprises.
The four stages of fault development in deep groove ball bearings:
Corresponding to the structural composition of rolling bearings, there are four types of fault frequencies: fault frequency of rolling bearing cage, fault frequency of rolling element of rolling bearing, fault frequency of outer ring of rolling bearing, and fault frequency of inner ring of rolling bearing. There is a specialized mathematical formula for calculating the failure frequency of these bearings, but in practical work, the calculation is more complicated. A more convenient method is to use specialized software to obtain it, such as the software of Rockwell Automation in the United States, which includes this function plugin. As long as information such as the bearing model and manufacturer is inputted, corresponding various bearing failure frequencies can be obtained.
In the first stage, which is the budding stage of bearing failure, the temperature is normal, the noise is normal, the total vibration speed and spectrum are normal, but there are signs of peak energy and spectrum, reflecting the initial stage of bearing failure. At this point, the true frequency of bearing failure occurs in the ultrasonic range of approximately 20-60kHz.
In the second stage, the temperature is normal, the noise slightly increases, the total vibration velocity slightly increases, and the vibration spectrum does not show significant changes, but the peak energy increases significantly, and the spectrum becomes more prominent. At this time, the frequency of bearing failures occurs in the range of approximately 500hz-2khz.
In the third stage, with a slight increase in temperature, noise can be heard and the total vibration speed increases significantly. The bearing fault frequency, harmonics, and sidebands are clearly visible on the vibration speed spectrum. In addition, the noise level on the vibration speed spectrum increases significantly, and the total peak energy becomes larger and the spectrum is more prominent compared to the second stage. At this point, the frequency of bearing failures occurs in the range of approximately 0-1kHz. It is recommended to replace the bearings in the later stage of the third stage, as visible wear and other rolling bearing fault characteristics should have already appeared by this time.
In the fourth stage, the temperature significantly increases, the noise intensity significantly changes, the total vibration velocity and displacement significantly increase, and the bearing fault frequency on the vibration velocity spectrum begins to disappear, being replaced by larger random broadband high-frequency noise; The total amount of peak energy rapidly increases and may experience some unstable changes. Bearings must not be allowed to operate during the fourth stage of fault development, otherwise catastrophic damage may occur.
According to research results, generally speaking, if the entire service life of a rolling bearing is calculated from the time of installation and use of the bearing, during its first>80% service life period, the bearing is in normal condition. Next, corresponding to the development of rolling bearing faults, their remaining lifespan ranges from 10% to>20% L10 in the first stage, from 5% to 10% L10 in the second stage, from 1% to 5% L10 in the third stage, and approximately 1 hour or 1% L10 in the fourth stage.
Therefore, when facing bearing problems in practical work, considering the unpredictable and sudden harm of the fourth stage of bearing failure development, it is recommended to replace the bearings in the later stage of the third stage. This can not only avoid the expansion of faults and more serious accidents, but also ensure the service life of rolling bearings as much as possible. Moreover, according to the visible wear and tear on the bearings at this time The characteristics of rolling bearing faults such as component damage are quite convincing. As for the identification of bearing faults in the later stage of the third stage, it is necessary to comprehensively consider the above theoretical characteristics, combined with actual temperature, noise, velocity spectrum, peak energy spectrum, total trend of velocity and peak energy, and practical experience.