Rolling bearing is the most widely used mechanical part, it is also the most easily damagedmachine element. Many rotating machinery breakdown is related to the state ofthe rolling bearing. According to statistics on rotating machinery driven by rolling bearings, about 30% mechanical failure is caused by the bearing. So thequality of bearing influences greatly on the state of the machine.
In general,since the bearing defect can cause the machine vibration and noise, and evencause damage to the machine. In the precision machinery (such as precisionmachine tool spindles, gyroscope, etc.), a higher degree of bearing accuracy is needed, it will destroy machine accuracy of the entire system by micron defects on bearings.
Rolling bearing is widely used in the equipment applications. Bearing state directly affects the running state of rotating equipment, it influences greatly especially in the continuous production of large enterprises, since a large number of large bearing are usedin important parts. So monitoring rolling bearing condition and bearing fault diagnosis in actual production is key process to improve equipment maintenance and management. Through a long time practice and exploration, we have accumulated some practical tips on bearing fault diagnosis.
Nowadays the counterfeit bearings will inevitably enter the business and equipment, which may cause sudden and catastrophic serious fault. Such as the bearing cage suddenly ruptures, bearing rings deflagration fracture, these failures will cause the rotor axle, or even seriously cause the rotor or destruction of equipment. In recent years, we also had gone through such situations. Therefore, in practical monitoring and diagnosis, it must be diagnosed as soon as the rolling bearing state is good or bad, and make sure timely replacement of counterfeit bearings, to avoid big accidents. Through a large number of incidents, we accumulate some practical skills, during initial operating stage of installation, monitor the vibration state, and make spectral analysis. We found during initial operation, the spectrum has its own unique characteristics, which is the device frequency is generally not accounted for the major ingredients. But vibration is not strong, it is ok to judge the vibration with a vibration standards (such as ISO2372 standard).
By this time, it should arouse our vigilance in this situation that is manifested as bearing defective parts, etc., which often fail quite quickly and suddenly. After the example that is measured in this figure two hours rotor axle.
When these counterfeit bearings fault is diagnosed, we should pay attention to the accumulation of spectral and time domain vibration of high quality bearing working condition on equipment, to facilitate the emergence of such a spectrum of abnormal timely when bearing failure is found, and avoid equipment accident.
●The practical skills for rapid diagnosis of rolling bearings
During the process of actual monitoring, we often check if the bearing is good or bad, how long it can be used, but the sophisticated analysis and diagnosis of certain parts of the diagnostic bearing failure is often not practical. Due to the working conditions and other factors, we are often not able to find the rolling bearing corresponding to the characteristic frequency through practical precise diagnosis. Though the wavelet analysis in recent years and the co-vibration demodulation analysis are more accurate, big funds is required on purchasing equipment, besides more analysis is needed, so it is rarely used by on site analysis staff. We take the dimensionless parameters and dimensionless parameter binding judgment for rapid fault diagnosis in practical bearing diagnosis, which uses the frequency spectrum analysis of vibration velocity, combined bearings kurtosis comprehensive diagnosis. When both conditions are exceeded the standard, we determine the faulty bearings.
After three years of practice, this judgment method is proved very practical on fault diagnosis of rolling bearings, to determine quickly and accurately with the accuracy rate of over 90%.Diagnosed bearings are substantially in the late stages of the fault, which is good cost saving.
Further, when low-frequency vibration to the rolling bearing is monitored very strong, after excluding unit misalignment, unbalance, loose structure, basic resonance structural factors, even without the characteristic frequency of rolling bearings, rolling bearing fault judgment should be decisive for maintenance.
