Vibration Acceleration National Standard (commonly known as Z-standard)
This standard was established relatively early. It determines the quality grade of a bearing by measuring the vibration acceleration value during rotation, and is divided into three quality grades: Z1, Z2, and Z3, from low to high. Currently, domestic bearing manufacturers still use this standard, relying solely on vibration acceleration values to measure bearing quality, which simply reflects the bearing's fatigue life.
Vibration Velocity Standard (commonly known as V-standard)
Since the original vibration acceleration standard has not been abolished, this standard was issued by the Ministry of Machinery Industry. It was developed with reference to European standards and combined with my country's actual situation and needs. It classifies bearing quality grades by detecting the vibration velocity (equivalent to the national standard). It is divided into five quality grades: V, V1, V2, V3, and V4. The quality grades of various ball bearings, from low to high, are V, V1, V2, V3, and V4; the quality grades of roller bearings (cylindrical and tapered) are V, V1, V2, and V3, from low to high.
This standard reflects bearing quality by detecting the vibration velocity (b-velocity) at different frequency ranges (low, medium, and high). It can broadly analyze whether the bearing has geometric dimensional problems (such as elliptical raceways), raceway/rolling element quality issues, and cage quality problems, representing a significant improvement over using vibration acceleration to assess bearing quality. Currently, bearings exported from China to Europe, as well as those used by the Chinese military and aerospace industry, are inspected according to this standard. It also provides a feasible means to inspect the quality of imported European bearings and identify counterfeit imported bearings.
However, bearing quality inspection currently involves two parallel standards. A bearing with a high "Z-standard" quality grade may not perform well under the "V-standard" test; there is no direct correlation between the two standards. This is a crucial point to consider in bearing quality inspection.
