Suma Precision Machinery

For modern high quality bearings, the nominal or basic rated life may be very different from the actual service life in a particular application.In a particular application, the service life is affected by various factors, including lubrication, contamination, misalignment, proper installation, and environmental factors.

ISO 281:1990/Amd 2:2000 therefore includes a revised life equation to supplement the calculation of the basic rated life.This life calculation USES a correction factor that takes into account lubrication, contamination and material fatigue limits of the bearing.ISO 281:1990/Amd 2:2000 also allows the bearing manufacturer to recommend appropriate methods for calculating the available bearing life correction factors based on operating conditions.SKF correction factor A, SKF adopts the concept of fatigue load limit Pu, similar to the algorithm used for other machine components.The value of the fatigue load limit is given in the product list.In addition, the SKF life correction factor the aSKF also USES the lubrication condition (viscosity ratio) and a coefficient c representing the degree of contamination to reflect the operating conditions in use.

The equation for SKF rated life is the same as ISO 281:1990/Amd 2:2000 Lnm = A1 aSKF L10 = A1 aSKF (C/P) P If the speed is constant, the life can be expressed by the equation Lnmh = A1 aSKF 106/(60n) L10,Where Lnm = SKF rated life (reliability 100-n1) %, million RPM Lnmh = SKF rated life (reliability 100-n1) %, operating hours L10 = basic rated life (reliability 90%), million RPM A1 = life reliability coefficient, aSKF = SKF life correction coefficient = basic rated dynamic load, KNP = equivalent dynamic load,KN = equivalent dynamic load

N = rotation speed, r/minp = life calculation equation exponential 3 for ball bearings 10/3 for roller bearings

The coefficient n represents the possibility of failure, for example: the difference is between the required reliability and 100%.

In some cases, instead of millions of revolutions or hours, it is preferable to express the bearing life in other units.For example, the bearing life of axle bearings used in road and rail vehicles is usually expressed in mileage.