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Useful tricks for the diagnosis of rolling bearings
Source: Bearing network time: 2017-12-04
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First, the method and key to the diagnosis of rolling bearing problems <br> The useful method for monitoring the condition of the rolling bearing and the diagnosis of the disease is the oscillation 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 rolling bearings normal operation and useful diagnosis and diagnosis <br> We found in the long-term production monitoring; rolling bearings in their application process showed a strong regularity; and repeatability is very good. Normal high-quality bearings at the beginning Time; the oscillation and noise are 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 tips
Nowadays, because of the counterfeit and inferior bearings, it is inevitable to enter the company and equipment; and the serious problems caused by these movable bearings are often sudden; catastrophic, such as the bearing cage suddenly cracked, the bearing inner and outer ring burst cracking, etc.; these problems will form the rotor Holding the 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; and replace the shoddy bearing in time; Preventing major incidents. We are in a lot of such incidents; we have also accumulated some useful tips; that is, such bearings are in the early stages of operation; monitor their oscillations; and perform spectrum analysis. We find that the bearings are in the early stages of operation; It has its common features; that is, the equipment power frequency usually does not occupy the primary component. However, the total value of the oscillation is not large; the oscillation specification (such as the ISO2372 specification) is used to determine the oscillation is qualified.
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 and diagnosis of the door <br> We are in the theoretical situation monitoring; often only need to judge the quality of the rolling bearing; how long can be used; and the fine analysis and diagnosis of a certain part of the bearing diagnosis is often not very useful The useful diagnosis of 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 analysis skill; 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; Contact the bearing kurtosis value for induction and diagnosis. When both conditions exceed the specification; we judge the bearing fault.
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
Nowadays, data collectors have been used more and more. But in the usefulness, we pay attention to the tricks. The oscillation is not big; the bearing kurtosis is not large; the spectrum is disorderly oscillating signal; when it is difficult to judge whether there is any problem in the field; we collect the oscillation signal Passed to the computer for fine analysis. At this moment; first routine analysis; see the oscillation velocity spectrum and bearing kurtosis can be close to the norm; then use the power spectrum to investigate whether the oscillation energy can be overrun; if the power spectrum is not large; investigate the spectrum Frequency component. If the spectral line corresponds to the frequency of the power frequency, it should focus on finding the fault in the layout of the unit. If it is a power frequency fraction; if it has more decimal frequencies, it should focus on finding the bearing frequency; if so; If there is any problem in the bearing; if it is not; after cleaning other parts, it needs to be alert; strengthen the monitoring. The theory finds that many oscillations are not over-expanded; but the bearing fault case is presented. Once the bearing characteristic frequency or the characteristic frequency spectrum of the bearing is presented, the bearing should be judged to exist. Wounds; then according to the magnitude of the large.
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