How to carry out correct condition monitoring and diagnosis of rolling bearings?

"Many mechanical failures are related to the rolling bearings in rotation. The performance of NSK bearing has a great impact on the working state of the machine. Its defects can cause abnormal vibration and noise in the equipment, and even damage the equipment in severe cases."

Many mechanical failures are related to the rolling bearings in rotation. The performance of the bearing has a great influence on the working state of the machine. Its defects can cause abnormal vibration and noise of the equipment, and even damage the equipment in severe cases. Correct condition monitoring and diagnosis of rolling bearings is an important aspect of equipment optimization management and predictive maintenance of modern enterprises.

Let's analyze the 4 early warning stages before bearing failure：

Four early warning stages of rolling bearing failure: Corresponding to the structural composition of rolling bearings, rolling bearings have 4 common faults: the cage, the rolling element, the outer ring of the bearing, and the inner ring of the bearing. For these bearing failure frequencies, there are special mathematical calculation formulas, but calculations are more troublesome in actual work. In daily use, the 4 problem stages that can be distinguished based on experience and testing are:

The first stage is the embryonic stage when the bearing starts to fail. At this time, the temperature is normal, the noise is normal, the total vibration speed and frequency spectrum are normal, but the total peak energy and frequency spectrum show signs, reflecting the initial stage of bearing failure. At this time, the real bearing failure frequency appears in the range of about 20-60khz in the ultrasonic section.

In the second stage, the temperature is normal, the noise increases slightly, the total vibration speed increases slightly, and the vibration frequency spectrum does not change significantly, but the peak energy increases greatly and the frequency spectrum becomes more prominent. The bearing failure frequency at this time appears in the range of about 500hz-2khz.

In the third stage, the temperature rises slightly, noise can be heard, the total amount of vibration velocity increases greatly, and the bearing fault frequency and its harmonics and sidebands are clearly visible on the vibration velocity spectrum, and the noise level on the vibration velocity spectrum is obvious. Increase, the total amount of peak energy becomes larger than the second stage, and the frequency spectrum is more prominent. At this time, the bearing failure frequency appears in the range of about 0-1khz. It is recommended to replace the bearing in the later stage of the third stage, then the rolling bearing failure characteristics such as wear and tear that can be seen with the naked eye should have appeared at this time.

In the fourth stage, the temperature increased significantly, the noise intensity changed significantly, the total vibration velocity and the total vibration displacement increased significantly, and the bearing failure frequency on the vibration velocity spectrum began to disappear and was replaced by a larger random broadband high-frequency noise level; The total amount of peak energy increases rapidly, and some unstable changes may occur. The bearing must not be allowed to operate in the fourth stage of failure development, otherwise catastrophic damage may occur.

According to the research results, in general, if the entire service life of a rolling bearing is counted from the time the bearing is installed and put into use, the bearing is normal for the first 80% of its service life. And then corresponding to the development of rolling bearing failure, the remaining life in the first stage is 10% to >20% L10, the second stage is 5%-10% L10, the third stage is 1% to 5% L10, and the fourth stage is about It is 1h or 1%L10.

Therefore, when facing bearing problems in actual work, considering that the fourth stage of bearing failure development has unforeseen sudden hazards, it is recommended to replace the bearings in the later stage of the third stage, so as to avoid the expansion of failures and more serious accidents. It can ensure the service life of the rolling bearing as much as possible, and it is more convincing based on the fact that the bearing has also been seen by the naked eye at this time, such as wear and component damage.

As for the identification of the later stage of the third stage of bearing failure development, it needs to be comprehensively considered based on the above theoretical characteristics, combined with the actual temperature, noise, speed spectrum, peak energy spectrum, the total trend of speed and peak energy, and actual experience.