Tips and meanings of rolling bearing fault diagnosis

Tips and meanings of rolling bearing fault diagnosis (worthy of collection)
zhishi.zcwz.com 2020/10/15

Tips for Diagnosing Rolling Bearing Faults
Note: This formula is the diagnosis experience of the inner ring and outer ring rolling elements under the condition of unknown bearing parameters on site, and the characteristic frequency should be kept in mind.
It is true that there is a bearing failure, and the frequency component is difficult to hide
Explanation: Four failure frequencies must be clarified. In the case of continuous monitoring of equipment, if the early defects of the bearing failure occur, the failure frequency of the component usually appears first, but if we only diagnose the failure of a certain equipment bearing, we will often encounter a cluster of vibration frequencies, which are friction, The comprehensive reflection form of various frequencies of impact, inner and outer raceways and even cages.
First look at the low frequency of the spectrum, and look at the non-synchronized ones.
Explanation: First look at the frequency components that are not synchronized with the frequency conversion and its multiplication, and the parts that do not overlap.
If there is a non-synchronous component, the fault can be divided into three points
Explanation: If there is a frequency component that is not synchronized with the rotation frequency and its multiplier, it is likely to be the bearing failure frequency.
The characteristic frequency harmonics are stored, and there is no doubt about the corresponding faults
Explanation: If the non-synchronous frequency component still has some wave components, it can basically be concluded that it is the fault frequency of the bearing.
Looking at the high frequency of the frequency spectrum, there is a fault in the modulation.
Explanation: If there is a modulation phenomenon with non-synchronous frequency as the sideband in the high frequency band, it can be concluded that the bearing is faulty.
The outer ring is characterized by frequency modulation, there is no doubt about the loosening phenomenon
Explanation: If the outer ring fault frequency is modulated by frequency conversion, that is, the sideband with frequency conversion, there should be a loose outer ring fault. Partial failures of the outer ring, such as pitting, horizontal lines, etc., may only show the passing frequency of the outer ring. As for the display of the outer ring loosening, it is not very understandable. The loosening of the outer ring of the bearing belongs to the problem of clearance and rigidity, which is often accompanied by the harmonic frequency of the rotation. frequency.
Inner ring fault frequency modulation can also be used as an evidence component
Explanation: The fault frequency of the inner ring will generally be modulated by the frequency conversion. Also, it will not be modulated in many cases, especially when it is a single local defect:
For special circumstances, it is appropriate to diagnose faults. If a single frequency exists, whether the bearing needs to be identified
Explanation: If there is a single non-synchronous frequency, there is no harmonic and modulation phenomenon, it is likely to be an interference signal or other, generally not a bearing failure frequency. In fact, many relatively single partial failures will occur at the passing frequency of the components, but such failures are often not serious.  High frequency is also very important.
Low frequency does not have high frequency, always follow diligent
Explanation: This sentence is good, otherwise you will find nothing if you disassemble the bearing
If the damage is serious, there is a hole in the high frequency lift
Timely replacement is not a fluke, to avoid accidents at all times
Explanation: Early failures are generally difficult to detect in low frequency bands, but they are generally manifested as modulation phenomena in high frequency bands, so pay more attention.
The mechanism of failure should be clearly understood, right and wrong should be distinguished
Lubrication status is often checked, debugging and assembly do not relax
There is a knack for diagnosing bearings, I believe that science can’t be wrong

Summary of Experience in Fault Diagnosis of Rolling Bearings in Gear Boxes
1. Know the internal structure of the gearbox and the characteristics of bearing failure
You need to know the basic structure of the gearbox, such as the type of gear, how many drive shafts there are, which bearings on each shaft, and what type of bearings, etc. Knowing which shafts and gears are high-speed and heavy-duty, you can determine the layout of the measuring points; know the motor speed and the number of teeth and transmission ratio of each transmission gear, you can determine the rotation frequency and meshing frequency of each transmission shaft; know the model of each bearing housing rolling bearing, The characteristic frequency of failure of each bearing can be determined. In addition, it is necessary to understand the characteristics of bearing failure. Gear meshing frequency is an integer multiple of the number of gears and rotation frequency, while the characteristic frequency of bearing failure is not an integer multiple of rotation frequency.
2. As far as possible, measure the vibration on the bearing seat where each drive shaft is located
The measurement points at different positions on the gearbox housing have different signal transmission paths, so the response to the same excitation is also different. The vibration response at the bearing seat where the drive shaft is located is more sensitive. The monitoring point should be set here. The upper part of the shell is relatively close to the meshing point of the gear, which is convenient for monitoring other faults of the gear.
3. Try to measure vibration from three directions: horizontal, vertical and axial
It is not necessary to perform vibration measurement in three directions at all positions, but it must be done for important parts. Multiple sets of vibration data at the same measurement point can also provide sufficient data reference for analyzing and judging the rotation speed of the drive shaft, and for further diagnosis of which end Bearing failures are more serious and get more references.
4. Take into account the high and low frequency vibration
The gearbox vibration signal contains the natural frequency, the rotation frequency of the transmission shaft, the meshing frequency of the gear, the characteristic frequency of the bearing failure, the side frequency family and other components, and its frequency band is relatively wide. For this kind of monitoring and diagnosis, it is generally necessary to classify according to frequency band, and select the corresponding measurement range and sensor according to different frequency ranges.
5. It is best to measure vibration when the gear is fully loaded
Measuring the gearbox vibration under full load can clearly capture the fault signal.
6. When analyzing data, both spectrogram and time domain diagram should be considered
In the case of a gearbox failure, learning UG programming to receive information in group 610677581 can help you sometimes the vibration amplitude of each failure feature on the spectrogram will not change significantly, and it is impossible to judge the severity of the failure or whether the drive shaft rotation speed is correct, so It is necessary to combine both the vibration spectrogram and the time domain diagram to infer.
7. Pay attention to the analysis of sideband frequency
For equipment with low speed and high rigidity, when the bearings in the gearbox wear out, the vibration amplitude of each fault characteristic frequency of the bearing is often not very large, but with the development of bearing wear faults, the harmonics of the characteristic frequency of bearing faults It will appear in large numbers and sidebands will appear. At this time, it indicates that the bearing has a serious failure and needs to be replaced in time.
[Reminder] [Zhongyu Bearing Network] Part of the information comes from the Internet, and strives to be safe, timely, accurate and correct. The purpose is to deliver more information. It does not mean that this website agrees with its views or is responsible for its authenticity. If the reprinted information on this website involves copyright and other issues, please contact this website in time. Phone: 0571-81630205.