revolutions that 90 percent of a group of bearings will complete at a given

Revolutions that 90 percent of a group of bearings

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revolutions, that 90 percent of a group of bearings will complete at a given load and speed before fatigue failure occurs -This life can also be given in hours of operation -The basic load rating can be used to predict the L10 life of a bearing under specific load and speed conditions-Prediction of bearing life -Bearing life is inversely proportional to bearing load and speed -Thus, reducing the load or speed or increasing the bearing size can substantially increase the bearing life -Safety factors -Because it is virtually impossible to predict the exact life of a bearing, a safety factor should be used to minimize the possibility of premature or unexpected failure -Bearing replacement and machine downtime may cost fat more than that for installing a larger bearingApplication and Selection -Bearing application and selection-Bearing application and selection is based on three major factors: load, speed and life-Consideration must also be given to other operating and environmental conditions, as well as installation and operating costs
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- Here are some factors to consider: - Load: is it radial, thrust, or a combination of both? What is the magnitude? Is the load uniform or does it pulse causing the bearing to operate under shock? - Speed: what is its magnitude? Is it constant or variable? Bearing speeds are limited by tolerance grade, lubricant used, retainer cage design and type of bearing seal - Required life: how long must the bearing of operate? This is usually expressed as the number of hours of operation reuqired at a given load and speed? - Noise and vibration: will the bearing operate where noise is undesirable or in high-speed equipment where balance is essential to prevent vibration? - Selecting a bearing - Misalignment: is it present? To what degree? - Temperature: what are the ambient and operating temperatures? Speed, load and external heat affect operating temperature - Environmental conditions: are contaminants or corrosives present? To what degree and what types - Once you have identified and evaluated these application constraints, compare the capabilities of various bearing types with the application requirements - Consider both operating and maintenance requirements, as well as cost - Selecting rolling element bearings - Here are various considerations when selecting rolling element bearings - Rolling-element bearings can handle heavier loads and higher speeds - They have the lowest friction and require the last energy to turn - Load requirements usually determine the type of rolling-element bearing to use for a specific application - For example, predominant thrust loading requires either thrust, angular contact, or tapered roller bearings - Ball bearings are typically applied in hihg-speed applications, whereas roller bearins are best suited for high loads - Spherical roller bearings offer high radial load capabilities with moderate thrust capacity and dynamic alignment capability - Tapered roller bearings have high radial and thrust load capability but do not allow for misalignment - Selected mounted bearings -
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