How to select bearing from catalogue

A bearing is a machine element that constrains relative motion and reduces friction between moving parts. Bearing is a mechanical element which permits relative motion between two parts, such as the shaft and the housing, with minimum friction. In this article we will see Procedure for selecting standard bearing available from manufacturing catalogue. Selection of bearing may involve various factors like Applications conditions, shafts Speed, Working condition, motor speed and torque, lubrication facility available, vibration, etc.

The functions of the bearing are as follows:
1. The bearing facilitates free rotation of the shaft with minimum friction.
2. The bearing supports the shaft and holds it in the correct position.
3. The bearing takes up the forces that act on the shaft and transmits them to the frame.

According to Application Of loads bearing types Selected are as Follows :

Light radial load with high rotational speed – Single row deep groove ball bearing
Heavy axial load with high rotational speed – Angular contact bearing.
Axial thrust only with medium speed. – Thrust ball bearing
Combined radial and axial load with medium speed. – Taper roller bearing

Sliding contact bearing is commonly used where there is relatively high load but relatively less speed. Following are the some of the practical applications.

1) Steam and gas turbines
2) Crankshaft bearing of diesel engines.
3) Electric motors of large size.
4) Centrifugal and axial pumps
5) Material handling equipments like rope conveyors.

What the procedure for selecting the bearing from the manufacturer’s catalogue?

The following procedure is followed in selecting the bearing from the manufacturer’s catalog.

Calculate the radial and axial loads i.e Fr and Fa acting on bearing.
Determine the diameter of the shaft on which the bearing is to be mounted.
Select the proper type of bearing for the given application.
The selection of bearing is done by trial and error. To begin with a bearing of extra light series is selected for the known shaft diameter.
Find the value of the basic static capacity ( Co ) of the selected bearing from the catalog.
Calculate the ratios (Fa/V Fr) and (Fa/Co).
Find the values of radial and thrust factors i.e. x and y from the catalog. The values depend upon two ratios (Fa/VFr) and (Fa/Co).
For the given application, find the value of load factor or app. factor Ka from catalog.
Calculate the equivalent dynamic load by using relation
Pe= (XVFr + YFa) Ka.
Depending upon the application decide the expected life of the bearing and express the life in million revolutions L10.
Calculate the required basic dynamic capacity for the bearing by using relation
L10 =(c/Pc)a.
Check whether the selected bearing has the required dynamic capacity. If not select the bearing of the next series and go back to step 5 and continue.
The above steps can be expressed as a flow diagram as below {In exam list either steps of flow diagram or both }

Flow chart for the selection of bearing from the manufacturers catalog

Procedure for selection of bearing from Catalog

Terms used here are explained below :

Life Of Bearing :

The life of an individual bearing is defined as the total number of revolutions (or the number of hours at a given constant speed) which the bearing can complete before the evidence of fatigue failure develops on the balls or races.

The bearing life can be defined by rating life.
The rating life of a group of apparently identical bearing is defined as the number of revolutions (or the number of hours at a given constant speed) that 90 percent of a group of bearings will complete or exceed before the first evidence of fatigue failure develops. It is also known as L10 life.

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