Fan Application
®
product
application guide
A technical bulletin for engineers, contractors and students in the air movement and control industry.
Understanding bearings for the fan industry
Bearings are one of the most critical components in the operation of a fan and careful consideration must be given to the selection of the appropriate bearing for each application. Fan manufacturers that have comprehensive product line ranging from small light duty commercial fans to heavy duty,
industrial fans inherently acquire more experience in bearing application. Through the years Greenheck
has worked closely with our bearing supplier partners to establish the quality features required for our full range of products, and to provide the bearing life expectancy required by our industry.
The following information is intended as a guide to understand
Bearing Life
Bearing life is usually expressed as the number of hours an individual bearing will operate before the first evidence of metal fatigue develops in the rings or rolling elements. In past years, four different terms were used when referring to bearing life. The terms commonly used were B10 or L10 and B50 or L50. The terms B10 and L10 had the same meaning and the terms B50 and L50 also had the same
meaning. It’s time to end the confusion! In today’s terminology the preferred term is L10. However, L50 is sometimes used, therefore both meanings must be understood.
L10 life: The preferred term in specifying bearing life.
The American Bearing Manufacturers Association (ABMA), formerly the AFBMA defines the Basic Rating Life, L10 as the bearing life associated with a 90% reliability when operating under conventional conditions, i.e. after a stated amount of time 90% of a group of identical bearings will not yet have developed metal fatigue. L10 life is also referred to by manufacturers as the `minimum expected life’.
L50 life: Or average life.
Although the L10 life is the proper method of specifying fatigue life per the ABMA, another term is often used in the industry. The L50 or average life is accepted as the bearing life associated with a 50% reliability, i.e., after a stated amount of time, only 50% of a group of identical bearings will not yet have developed metal fatigue. L50 life equals five times the L10 life.
In other words, to get a L50 life equal to a L10
Required L10 | Equivalent L50 (avg) |
Life Hours | Life Hours |
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|
20,000 | 100,000 |
40,000 | 200,000 |
80,000 | 400,000 |
100,000 | 500,000 |
200,000 | 1,000,000 |
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® | P.O. Box 410 • Schofield, WI 54476 • 715.359.6171 • Fax 715.355.2399 |
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