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The four stages of bearing failure - when is the best time to replace bearings

The four stages of bearing failure - when is the best time to replace bearings

2021-06-29

Rolling bearing is the most widely used in rotary machinery, and it is also one of the most easily damaged components. Many failures of rotating machinery are related to rolling bearings. The working quality of bearings has a great impact on the working state of machinery. The defects will lead to abnormal vibration and noise of equipment, and even damage the equipment in serious cases. Correct condition monitoring and diagnosis of rolling bearings is an important aspect of equipment optimization management and predictive maintenance in modern enterprises.

The four stages of rolling bearing fault development:

Corresponding to the structural composition of rolling bearings, rolling bearings have four kinds of failure frequencies: rolling bearing cage failure frequency, rolling bearing rolling body failure frequency, rolling bearing outer ring failure frequency, rolling bearing inner ring failure frequency. For calculating the bearing fault frequency, have a special mathematical formula, but in the practical work of calculation more troublesome, convenient method is to use special software, such as the United States with Rockwell automation software in this feature plug-in, as long as the input bearing model and the information such as the manufacturer, they can get the corresponding all kinds of bearing failure frequency.

The first stage, that is, the budding stage when the bearing begins to fail when the temperature is normal, the noise is normal, the total vibration speed and the frequency spectrum are normal, but the total peak energy and the frequency spectrum have symptoms, reflecting the initial stage of bearing failure. At this time, the real bearing fault frequency appears in the ultrasonic section within the range of about 20-60kHz.

In the second stage, the temperature is normal, the noise is slightly increased, and the total vibration velocity is slightly increased. The change of vibration spectrum is not obvious, but the peak energy is greatly increased, and the spectrum is more prominent. At this time, the bearing failure frequency appears in the range of about 500Hz-2KHz.

In the third stage, when the temperature increases slightly, the noise can be heard, and the total vibration velocity increases greatly. In addition, the bearing fault frequency, its harmonics, and sidebands can be clearly seen in the vibration velocity spectrum. In addition, the noise horizon increases significantly in the vibration velocity spectrum, and the total peak energy becomes larger and the spectrum is more prominent than in the second stage. At this time, the bearing failure frequency appears in the range of about 0-1kHz.It is recommended to replace the bearing in the late stage of the third stage, then at this time, there should have been visible wear and other rolling bearing fault characteristics.

In the fourth stage, the temperature increases significantly, the noise intensity changes significantly, the total vibration velocity and vibration displacement increase significantly, and the bearing fault frequency begins to disappear in the vibration velocity spectrum and is replaced by a larger random broadband high-frequency noise horizon. The total amount of peak energy increases rapidly and some unstable changes may occur. Bearings must not be allowed to operate in the fourth stage of failure development, otherwise, catastrophic damage may occur.

According to the results of the study, in general, if the whole service life of the rolling bearing is then calculated from the time when the bearing is installed and put into use, in its former >;80% of the life period, the bearing is all normal. Then corresponding to the development of rolling bearing faults, the remaining life is 10% in the first stage.20%L10, the second stage is 5%-10%L10, the third stage is 1%-5% L10, and the fourth stage is about 1H or 1%L10.

Therefore, when facing bearing problems in practical work, considering that the fourth stage of bearing fault development has unforeseeable sudden harm, it is recommended to replace bearings in the late stage of the third stage, which can not only avoid the expansion of the fault and the occurrence of more serious accidents but also try to ensure the service life of rolling bearings. And according to the bearing at this time has also appeared visible to the naked eyewear, parts damage, and other rolling bearing fault characteristics, more convincing. As for the identification of the late stage of bearing fault development, it is necessary to consider comprehensively according to the above theoretical characteristics combined with the actual temperature, noise, velocity spectrum, peak energy spectrum, the total trend of velocity, and peak energy, and practical experience.

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