09-02-2013, 02:13 PM
BEARING
BEARING.ppt (Size: 945.5 KB / Downloads: 415)
INTRODUCTION
A Bearing is a device to permit constrained relative motion between two parts, typically rotation or linear movement.
When there is a relative motion between two machine parts, one of which supports the others.The supporting member is called Bearing.
CLASIFICATION OF BEARING
Bearing are classified depending upon the load.
Bearing are also classified depending upon the type of contact.
1. Sliding contact bearing
- journal bearing
- plane bearing
2. Antifriction bearing
- Ball bearing
- roller bearing
FUNCTION OF BEARING
• A bearing permits relative motion between two machine members while minimizing Frictional resistance.
• A bearing consists of an inner and outer member separated either by a thin film of Lubricant or a rolling element.
• A bearing bears the load.
• It locates the moving parts in correct position.
• It provides free motion to the moving part by reducing friction.
SELECTION OF BEARING TYPE
Each bearing type displays characteristic properties, based on its design which makes it more, or less appropriate for a given application
The most important factors to be considered when selecting a standard bearing type and thus a facilitate an appropriate choice :
Available space
Loads
Misalignment
Precision
Speed
Quiet running
Stiffness
Axial displacement
Mounting and dismounting
Integral seals
LOADS
MAGNITUDE OF LOAD :-
The magnitude of the load is one of the factors that usually determines the size of the bearing to be used. Generally, roller bearing are available to support heavier loads than similar size ball bearing and bearings having a full compliment of rolling elements can accommodate heavier loads than the corresponding caged bearing.
SPEED
The permissible operating temperature limits the speed at which rolling bearings can be operated. Bearing types with low friction and correspondingly low heat generation inside the bearing are therefore the most suitable for high - speed operation.
BEARING LUBRICATION
Lubrication reduces friction. It also prevents wear and corrosion, and guards against
solid and liquid contamination. Theoretically, a properly lubricated bearing operating
under ideal conditions will last forever. This is not possible in reality, of course. But a
properly lubricated bearing has the best chance of achieving its maximum service life.