LubricationLubrication1. Lubrication is the process, or

technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each other, by interposing a substance called lubricant between the surfaces to carry or to help carry the load (pressure generated) between the opposing surfaces surfaces

Purpose of lubrication

The purpose of bearing lubrication is to The purpose of bearing lubrication is to prevent direct metallic contact between prevent direct metallic contact between the various rolling and sliding elements. the various rolling and sliding elements. This is accomplished through the This is accomplished through the formation of a thin oil (or grease) film on formation of a thin oil (or grease) film on the contact surfaces.the contact surfaces.

Advantage of lubrication Advantage of lubrication for rolling bearingfor rolling bearing

Reduction of friction and wear Dissipation of friction heat Prolonged bearing life Prevention of rust Protection against harmful

elements

Function of lubricationFunction of lubrication

1.1. To reduce friction and wear between the To reduce friction and wear between the moving parts and thereby the energy loss moving parts and thereby the energy loss and to increase the life of engine. and to increase the life of engine.

2.2. To provide sealing action e.g rhe To provide sealing action e.g rhe lubrication oil helps the piston ring to lubrication oil helps the piston ring to maintain the effective seal against the maintain the effective seal against the high pressure gases in the cylinder from high pressure gases in the cylinder from leaking out into the crankcase.leaking out into the crankcase.

3.3. To cool the surfaces by caring away the To cool the surfaces by caring away the heat generated in the engine components. heat generated in the engine components.

4.4. To clean the surface by washing away To clean the surface by washing away carbon and metal particles caused by carbon and metal particles caused by wear.wear.

Mechanism of Mechanism of lubrication lubrication

The resistance between moving surface can be The resistance between moving surface can be reduce by introducing of a small film of reduce by introducing of a small film of lubricant between the moving surface so that lubricant between the moving surface so that the to surface are not in physical contact. The the to surface are not in physical contact. The lubricant film provides the lesser resistance lubricant film provides the lesser resistance than that of solid surface and hence less force is than that of solid surface and hence less force is required to accomplish a relative motion . Thr required to accomplish a relative motion . Thr friction due to surface irregularities and larger friction due to surface irregularities and larger molecular attraction is reduced. The solid molecular attraction is reduced. The solid friction is replaced with a definitely lesser fluid friction is replaced with a definitely lesser fluid film. film.

Tangential force Tangential force coefficient of friction (f)= Normal force coefficient of friction (f)= Normal force

Selection of lubricating oil

Under normal operating conditions, spindle oil, machine oil, turbine oil, and other mineral oils are widely used for the lubrication of rolling bearings. However, for temperatures above 150°C or below -30°C, synthetic oils such as diester oil, silicone oil, and fluorocarbon oil are used.

Automatic Transmission Automatic Transmission fluidfluid(ATF)(ATF)

Has red color to identify it from Has red color to identify it from motor oil.motor oil.

Several kindsSeveral kinds:: Dexron/MerconDexron/Mercon Type FAType FA

Role of viscosityRole of viscosity

For lubricating oils, viscosity is one of the most important properties and determines an oil’s lubricating efficiency. If viscosity is too low, formation of the oil film will be insufficient, and damage will occur to the raceways of the bearing. If viscosity is too high, viscous resistance will also be great and result in temperature increases and friction loss. In general, for higher speed applications a lower viscosity oil should be used; for heavier load applications, a higher viscosity oil should be used.

Oil viscosity chartOil viscosity chart :- :-

Relubrication intervals The intervals at which lubricating oil

should be changed varies depending upon operating conditions, oil quantity, and type of oil used. In general, for oil bath lubrication where the operating temperature is 50°C or less, oil should be replaced once a year. When the operating temperature is between 80°C – 100°C, oil should be replaced at least every three months. For important equipment, it is advisable that lubricating efficiency and oil purity deterioration be checked regularly to determine when oil replacement is necessary.

Elastohydrodynamic Elastohydrodynamic lubrication lubrication

Journal bearing Journal bearing lubrication lubrication

Stable lubrication Stable lubrication

Lubricating systemLubricating system

The function of lubrication system is to The function of lubrication system is to provide sufficient quantity of cooled, provide sufficient quantity of cooled, filtered oil to give positive and filtered oil to give positive and adequate lubrication to all moving adequate lubrication to all moving parts of an engine. parts of an engine.

Lubrication systems used in the internal Lubrication systems used in the internal combustion engine are:-combustion engine are:-

1.1. Misty lubrication system Misty lubrication system 2.2. Wet sump lubrication system Wet sump lubrication system 3.3. Dry sump lubrication system Dry sump lubrication system

Mist lubrication system Mist lubrication system