Lubrication means apply of lubricating element at right position, right amount and right time. In case of bearing lubrication is very necessary to minimize the bearing resistance, frictions and power losses.
Purpose of lubrication:
Ø To reduce the sliding frictions.
Ø To remove heat from contact surfaces.
Ø To prevent corrosions.
Ø To keep contaminants out of surface.
Lubricants:
The elements which are used for lubrication are known as lubricant. There are mainly two types of lubricants:
- Oil
- Grease
Properties of good lubricants:
Ø Higher wear resistance
Ø Medium viscosity
Ø Having unbroken film
Ø Transparent and chemically stable
Ø Prevent frictions
Ø Removes heats from contact surface
Ø Remain stable under several operations
Lubricant selections: It depends upon the parameters –
Ø Load
Ø Speed
Ø Temperature
Ø Bearing types
Oil lubrication:
It is used for light and moderate loads operating at high speed with 30oF – 200oF.
Applications:
Ø Antifriction bearings
Ø Generators
Ø IC engines
Ø Machine tools
Ø Power transmission equipments
Ø Pumps
Grease lubrication:
Grease is a mixture of lubricating oil and thickening substances like soap, graphite etc. It is used at low temperature under heavy loads. It also prevents the dust particles and other contaminants.
Grease selection:
It depends upon the factors-
Ø Hardness
Ø Stability
Ø Water resistance
Hardness is expressed in terms of number. Higher the number indicates higher hardness.
Generally greases are classified by number.
When number = 6, then most hard grease
When number = 0, then softer.
Softer grease is easy to apply anywhere and more efficient.
Relation with temperature:
Ø Grease life becomes half with every 25oF temperature increase.
Ø Grease life becomes double with every 25oF temperature decrease.
Applications:
Ø Motor bearings
Ø Power transmission devices.