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.
● Rolling bearings fault diagnosis methods and key points
Practical methods for rolling bearing condition monitoring and fault diagnosisis through vibration analysis. We should pay attention to select the test point and signal acquisition method. To accurately reflect the true state ofvibration of rolling bearings, signal acquisition must be true and accurate,and therefore choose measuring point from the nearest spot of the bearing.Generally there is a fan cover at the free end of the motor , so the test point should be in the fan cover fixing screws for better monitoring results. To get accurate results, we should make a comprehensive comparison on several of the vibration signal acquisition and analysis.
●The characteristics of rolling bearing normal operation and practical diagnostic skills.
Through long-term production status monitoring, we find rolling bearing shows strong regularity in the course of working, and very good reproducibility. For normal quality bearings at the start of use, the vibration and noise are relatively small, but some scattered spectrum amplitude are small, probably due to some defects in the manufacturing process, such as surface glitch.
After a period time of working, we see vibration and noise maintain a certain level, the spectrum is single only for one or two multiplier. It rarely occurs more than three times the frequency spectrum, which means the bearing condition is very stable, leads into the stable phase.
Continuously run into the post-use, bearing vibration and noise begins to increase, sometimes arising abnormal sound, further more changes of increasing vibration become very slow, meanwhile bearing kurtosis values began suddenly reaches a certain value. In our view, the bearing now is manifested as initial failure.
In this case, the bearing requires close monitoring, pay close attention to the changes. Thereafter, bearing kurtosis values began to decline rapidly, and close to normal, and the vibration and noise began to significantly increase its growth began to accelerate dramatically when the vibration exceeds vibration standards ;which also started bearing kurtosis rapid increase, when the vibration exceeds both standards, and kurtosis values than normal (relative standard available kurtosis), we believe that the bearing has entered production late failure. Please maintain equipment timely and replace rolling bearings accordingly.
It takes not more than a week from late time failure to a serious failure(usually as axle bearing damage, burns, sand shelf spoliation, raceway, wearbeads, etc.).For greater capacity of the device and faster speed, the interval will be much shorter. Therefore, in the actual ball bearing fault diagnosis,once found fault with advanced features, it should be decisive to determinefaulty bearings, maintenance arrangements as soon as possible.
