Bearings show strong regularity during their use, and the repeatability is very good. Normal high-quality angular contact ball bearings have relatively small vibration and noise at the beginning of use, but the frequency spectrum is somewhat scattered and the amplitude is small, which may be due to some defects in the manufacturing process, such as surface burrs.

After exercising for a period of time, the vibration and noise maintain a certain level, and the frequency spectrum is very single, with only one or two times frequency appearing. The spectrum above three times the power frequency rarely appears, and the state of Timken bearings is very stable, and it has entered a stable working period.

After continuing to run and entering the later stage of use, the vibration and noise of the bearing begin to increase, and sometimes there are abnormal sounds, but the increase in vibration changes slowly. At this time, the kurtosis value of the angular contact ball bearing suddenly reaches a certain value. We believe that at this time the bearing is showing an initial failure.

At this time, it is required to closely monitor the bearing and pay close attention to its changes. After that, the bearing kurtosis value began to drop rapidly again and approached the normal value, while the vibration and noise began to increase significantly, and the increase rate began to accelerate. When the vibration exceeded the vibration standard (such as the ISO2372 standard), the bearing kurtosis value also began to increase rapidly.

The time between bearing showing late failure characteristics and serious failure (generally bearing damage such as shaft holding, burns, spalling of sand frame, raceway, bead wear, etc.) does not exceed one week. The larger the equipment capacity and the faster the speed, the shorter the interval time. Therefore, in the actual bearing fault diagnosis, once the late fault features are found, it should be decisively judged that there is a fault in the bearing and arrange for maintenance as soon as possible.

1. The installation and adjustment of low-noise angular contact ball bearings can also follow the grouping method of long-life bearings, so that the size of the fit and interference is relatively consistent, and the clearance of the bearings is also relatively consistent, and it is hoped that the fit and interference can take a smaller value within the possible range to ensure that the deformation of the bearing raceway is small, so that the noise caused by the passing of the rolling elements becomes smaller.

2. The clearance has a great relationship with the noise. The ideal state is that when the imported bearing is in the highest temperature state of operation, the clearance value is just zero. The methods for judging the excessive clearance are as follows: the shaft is displaced axially in a static state, and its reciprocating range is relatively large, and it emits loud and heavy noise during operation.

3. If there is an annoying sharp howling sound during operation, it means that the preload of the angular contact ball bearing is too large, and the timken bearing has a relatively large preload, and the preload should be slightly relaxed. If the clearance is too large, the two bearing rings can be slightly offset relative to each other in the axial direction: it not only reduces the clearance, but also increases the axial rigidity, which can reduce the bearing noise.

4. The rolling element will slip or move left and right when it enters the no-load area, which will increase noise and cause wear, but small clearance and large axial stiffness can eliminate this phenomenon. However, the clearance should not be too small, so as not to cause excessive temperature and shorten life.

5. Sometimes due to the large operating temperature range of the main engine, or the large dispersion of the dimensions of the shaft and the seat hole, it is impossible to obtain a more appropriate clearance at one time. In this case, the outer ring of the angular contact ball bearing can be preloaded with elastic constant pressure.