Answer:
Hit would be best if you need a bearing that can last approximately 375,774.85 revolutions with the given load and speed.
Step-by-step explanation: To determine the catalog rating you should search for in an SKF catalog, you need to consider the desired bearing life, operational reliability, and reliability. The catalog rating you're looking for is typically given as the bearing's dynamic load rating (C), which is the load at which the bearing's approach is expected to have a nominal life of 1 million revolutions.
Given the following information:
Desired life (L₁): 5,000 hours
Operating speed (N): 1,725 revolutions per minute (rpm)
Load (P): 400 pounds-force (lbf)
Reliability (R): 90%
First, you need to calculate the number of revolutions the bearing will undergo during its desired life:
L₁ = (60 / N) * L
Where:
L₁ = Desired life in revolutions
N = Operating speed in rpm
L = Desired life in hours
L₁ = (60 / 1,725) * 5,000 = 174,275.36 revolutions
Next, you need to use the reliability factor (a) to determine the actual life required for a 90% reliability. The reliability factor can be calculated as follows:
a = (1 / (1 - R))^(1/3)
Where:
R = Reliability (expressed as a decimal)
a = (1 / (1 - 0.90))^(1/3) = 2.15443
Now, calculate the actual life (L₉₀) required for 90% reliability:
L₉₀ = a * L₁ = 2.15443 * 174,275.36 ≈ 375,774.85 revolutions
So, having a bearing that can last approximately 375,774.85 revolutions with the given load and speed would be best.
Now, search for a bearing in the SKF catalog with a dynamic load rating (C) equal to or greater than the applied load of 400 lbs. The bearing's dynamic load rating (C) indicates the load the bearing can handle while achieving the desired life. Choose a bearing with a C value that meets or exceeds the load requirement, and you'll have a bearing with a suitable catalog rating for your application.