Useful tips for the diagnosis of rolling bearings

Source: China Bearing Network Time: 2014-04-05

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The use of rolling bearings in equipment is very extensive; the condition of rolling bearings is directly related to the operation of rotating equipment; especially in the production of large continuous production; many are used in important parts of large rotating equipment; therefore; the production of rolling bearings in the theoretical production and monitoring The diagnosis of defects is an important part of the equipment repair and handling. We pass the long-term theory and exploration; it has accumulated some useful tips for the diagnosis of rolling bearing theory.
First, the method of diagnosis of rolling bearing problems and the key to the conditional monitoring of rolling bearings and the diagnosis of fault diagnosis is a vibration analysis.
In the usefulness, it is necessary to pay attention to the selection of the orientation and collection method of the measuring point. In order to accurately reflect the oscillation condition of the rolling bearing, it is necessary to pay attention to the accurate and accurate collection of the signal; therefore, it is necessary to organize the measuring point from the bearing; the motor is usually at the free end. Rear fan cover; its measuring point is selected in the electric fan cover fixing screw has a better monitoring function. Others need to pay attention to the repeated collection and analysis of the oscillating signal; inductive comparison. Talent can be refined.
Second, the characteristics of the normal operation of rolling bearings and the diagnosis of defects in the long-term production situation monitoring; rolling bearings in their application process shows a strong regularity; and repeatability is very good. Normal high-quality bearings at the beginning of use; oscillation And the noise is comparable. The lamp is smashed 18. The ring is slashed and smashed. The beggar is smashed.
After a period of motion; the oscillation and noise are kept at a certain level; the spectrum is very simple; only one or two times the frequency is present. The spectrum of three times the power frequency is rarely presented; the bearing condition is very stable;
After continuous operation, it enters the late stage of operation; bearing oscillation and noise start increase; sometimes it shows an abnormal sound; but the change of the oscillation increase is slower; at this moment; the bearing kurtness value starts to reach a certain value. We think that the bearing is the initial stage. Faulty.
At this time; the bearing should be closely monitored; pay close attention to its change. After that; the bearing kurtosis value starts to decrease rapidly; and it is close to the normal value; and the oscillation and noise start increase obviously; it increases the undulation and starts to accelerate; When the oscillation exceeds the oscillation specification (such as the ISO 2372 specification); its bearing kurtosis value also starts to increase rapidly; when it exceeds the oscillation specification; and the kurtosis value also exceeds the normal value (available kurtosis relative specification); we think that the bearing Has entered the late stage of disease; need to repair equipment in time; replace the rolling bearing.
Bearings exhibit late-stage fault characteristics to present severe problems (usually bearing damage such as axles, burns, sand cracks, raceways, bead wear, etc.) that do not exceed one week at all times; the larger the equipment capacity; the faster the speed; The shorter the interval is. Therefore, in the diagnosis of the theoretical rolling bearing fault; once the late fault characteristics are found; the bearing should be judged to be faulty;
Third, the rolling bearing abnormal operation characteristics and diagnosis of the trick nowadays because the counterfeit and inferior bearings will inevitably enter the company and equipment; and the serious problems caused by these active bearings are often sudden; catastrophic. If the bearing cage suddenly cracked, the bearing inside and outside the ring Burning cracks, etc.; these problems will form the rotor holding shaft; the heavy ones cause the rotor or equipment to be invalid. In recent years, we often encounter such conditions in the theory. Therefore; in the theoretical monitoring and diagnosis; it is necessary to quickly diagnose the condition of the rolling bearing Good or bad; and timely replacement of shoddy bearings; prevent major incidents. We are in many such incidents; also piled up some useful tips; that is, such bearings in the early stage of operation of the device; monitor its oscillation; and perform spectrum analysis. We found that the bearing is in the early stage of operation; its spectrum has its common features; that is, the power frequency of the equipment usually does not occupy the primary component. However, the total value of the oscillation is not large; the oscillation specification is determined by the oscillation specification (such as the ISO2372 specification).
At this moment; it will cause us to be alert; this situation is manifested as the shortcomings of the bearing components; its failure is often very fast and very violent. In the above example, the rotor is hung two hours after the measurement is completed.
In the diagnosis of these fake and shoddy bearing problems; pay attention to the multi-pile normal high-quality bearing in the normal operation of the spectrum and oscillation time domain conditions; easy to identify the bearing fault in the appearance of such anomalous spectrum; prevent equipment incidents.
Fourth, the useful rolling bearing rapid diagnosis of the sputum in the theoretical situation monitoring; often only need to judge the quality of the rolling bearing; how long can be used; and fine analysis and diagnosis of a certain part of the bearing diagnosis is often not useful. Useful Fine diagnosis is affected by factors such as working conditions; the characteristic frequency corresponding to the rolling bearing is often not found. Although the wavelet analysis developed in recent years is more accurate than the rapid co-oscillation demodulation and analysis skills, the required equipment investment is large; More analysis is needed; the on-site diagnosis is usually used less frequently. We use the dimension parameter and the dimensionless parameter to determine the diagnosis of the bearing disease in the useful diagnosis; that is, the frequency oscillation speed in the spectrum analysis is selected; The degree is inductively diagnosed. When both conditions exceed the specification; we determine that the bearing is faulty.
This method of judging has passed the theory of three years; it proves that it is very useful for the diagnosis of rolling bearings. The speed is accurate and accurate; the accuracy rate exceeds 90%. The diagnosed bearings are basically in the late period; there is a very good economy. benefit.
Others; when monitoring the low-frequency oscillation of the rolling bearing is very large; after sweeping the unit is not centered, unbalanced, loose layout, the fundamental resonance layout elements; even if there is no rolling bearing characteristic frequency; should determine the rolling bearing fault for maintenance.
V. Useful spectrum analysis and diagnosis of rolling bearings Tuen Mun has now been used in data collectors. However, it pays attention to the tricks in terms of usefulness. The oscillation is not large; the bearing kurtosis is not large; the spectrum is disorderly oscillating signal; When the problem occurs; we collect the oscillating signal; pass it to the computer for fine analysis. At this moment; first perform routine analysis; see if the oscillation velocity spectrum and bearing kurtosis can be close to the specification; then use the power spectrum to investigate whether the oscillation energy can be overrun; The power spectrum is not large; investigate the various frequency components in the spectrum. If the spectral line corresponds to the frequency of the power frequency, it should focus on finding the faults in the layout of the unit. If it is a power frequency fraction, it will present more decimal frequencies. Focus on finding the frequency of bearing; if there is; then there is a problem with the bearing; if not; need to be alert after sweeping other parts; strengthen monitoring. The theory finds that many oscillations do not overspend; and present a case of bearing fault. Once the bearing characteristic frequency or near is present Bearing characteristic frequency spectrum; it should be judged that the bearing is faulty; then according to the amplitude of the large. Only occasionally.

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