Bearing Knowledge Encyclopedia (5)
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Source: China Bearing Network | Time: 2013-06-21
When designing a bearing system, it's crucial to consider various factors such as load capacity, power loss, and expected operational life. For example, if a bearing is required to operate for more than 1000 hours with a power loss of 4%, the life percentage from the table is 53% of the standard L bearing life. To calculate the adjusted life, divide the required lifespan by the correction factor:
L = 1000 / 0.53 ≈ 1887 hours
This means that achieving a 96% reliability level requires a bearing life of approximately 1887 hours. Introducing the dynamic bearing capacity equation helps in calculating the appropriate bearing size for a 90% reliability rating.
Calculating loads and equivalent loads is essential to determine the additional stress on the bearing. It's important to consider all forces acting on the equipment, including the moments generated by each force over time. These conditions can be tabulated, with load units in Newtons (N), speed in revolutions per minute (r/min), and operating time expressed as the bearing's reserved life.
By simplifying these conditions into an equivalent load P, you can apply the relevant equations to determine the effective load for each scenario. If both speed and load remain constant during operation, the equivalent load is simply the actual load:
P = P (Equation A)
However, if the load varies over time while the speed remains constant, the equivalent load calculation becomes more complex. In cases where the load changes nonlinearly—such as through step functions, power functions, or sine waves—the equivalent load must account for these variations over time.
When both load and speed change simultaneously, the equivalent load depends on the corresponding speed and load values. The modified life formula accounts for different speeds and their respective durations. The coefficient "500" in the formula represents a reference life of 500 hours at a standard speed of 33 r/min, aligning with international bearing standards.
Oscillating loads often require adjustments in the equivalent load calculation. In such cases, the correction factor K is used to account for the worst-case oscillating force compared to the stable radial load. Table 1.6 provides correction coefficients for different loading scenarios, ensuring accurate bearing selection.
For further reading, check out related articles such as "Can SKF Bearing Grease Be Changed?" or "Protection and Smoothing of Anti-Wear Bearings in NSK Imported Bearings."
This article was originally published on China Bearing Network. For more information, visit [http://www.chinabearing.net](http://www.chinabearing.net).
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