Quality inspection method for bearings
1.National standard of vibration acceleration (commonly known as z-standard)
The standard was established earlier, to measure the vibration acceleration value of the bearing when rotating, to determine the quality of the bearing, divided into Z1, Z2, Z3 from low to high quality grade.At present, bearing manufacturers in China are still using the vibration acceleration value to measure the advantages and disadvantages of the bearing, it simply reflects the fatigue life of the bearing.
2.Vibration velocity standard (commonly known as V standard)
Because the original vibration acceleration standard has not been abolished, so the standard is issued by the ministry of machinery industry standards, is the reference to the European standards combined with the actual situation and needs of our country, to test the bearing vibration speed to determine the quality of the bearing grade (equivalent to the national standard).Divided into V, V1, V2, V3, V4 five quality levels.Various ball bearing quality classes from low to high V, V1, V2, V3, V4;Roll bearings (cylinder, cone) quality grade from low to high for V, V1, V2, V3 four quality grade.It is to detect the vibration speed of bearing of different frequency segments (low frequency, medium frequency, high frequency) to reflect the quality of bearing.It can be generally analyzed whether the bearing has the geometric size problem (such as the steel ring ellipse), the quality problem of raceway/rolling body, the quality problem of the cage, compared with the vibration acceleration to investigate the bearing quality has made a significant improvement.At present, the domestic bearings exported to Europe, the Chinese military and the aerospace industry all carry out bearing quality inspection in accordance with this standard, and at the same time, the quality inspection of European imported bearings and the discrimination of counterfeit imported bearings provide a feasible means.
At present, there are two parallel standards in bearing quality inspection, and the bearings with high quality grade of "z-standard" may not have good quality performance in "v-standard" inspection, and there is no correspondence between the two.This in the bearing quality inspection is to pay special attention to.
The bearing in use is tested by vibration measuring instrument
Bearing in operation, although ISO2372 standard is excessive vibration velocity to determine, but in the actual to pay special attention to the change of bearing acceleration value, bearing damage process is mostly the early performance for fatigue damage, it can generally show the obvious acceleration increases, with the development of fatigue, vibration velocity and displacement increases gradually, heralds bearing in the fatigue damage.Especially for detecting a bearing, pay careful attention to the vibration value is instability to swing (it is recommended to use analog pointer instrument, can look for the obvious), if there is a swing, indicates the unstable vibration signal, the acceleration is also big, especially speed increase at the same time, is likely to "play" bearing fault.
For new equipment, acceptance testing, while the vibration is very small, in line with the national standard, but in the vibration of the bearing parts appear small oscillation phenomenon, eliminate bearing after (play) with problem, probably bearing geometry problems, such as bearing rims ellipse, rolling body after a long axis of the ellipse, may be caused by gap decrease instant card roller die, subsequent continued squeezing roller, make the rolling body produces sliding friction, each will appear in the sliding friction roller, cause the unstable signal.This problem was encountered in the detection of the new 220KW motor in shanxi, disintegrating the detection, testing the bearing, proving that the judgment is completely correct.
Special note: in the inspection of the rolling bearing, must not ignore the bearing acceleration value of the change.Acceleration can better predict the failure of rolling bearings in the early stage.
3.Reference for quality inspection and analysis of imported bearing
In the quality inspection of imported bearings, the quality of each type of genuine bearings from Japan is good.However, it is found that the quality of a famous bearing is not ideal.In the nominal origin for Malaysia and Australia bearing test found that the quality is not ideal, or even inferior to the domestic formal manufacturers of genuine bearings.
Tip: at present, there is no corresponding testing standard for all kinds of double-row rolling bearing and pure axial thrust bearing.After the angular contact ball bearing meets the specified axial load, the quality grade of deep groove ball bearing can be referred to.