Introduction and Mechanism of Lubrications

Apr 27 • General • 3486 Views • 3 Comments on Introduction and Mechanism of Lubrications

LUBRICANTS

Introduction and Mechanism of Lubrications 

Any substance that reduces friction between two moving surfaces is termed as lubricant and this property of reducing friction is called as lubricity.The main application of lubricant is motor oil .This motor oil protects the internal combustion engines in motor vehicles by preventing friction between two moving surfaces.

Some characteristics possessed by lubricants are 

1. lubricants are thermally stable.
2. lubricants have Low freeing point .
3. lubricants have High boiling point.

The important functions of lubricants are :

1. Lubricants Reduces the loss of energy as heat dissipation .
2. Lubricants reduces damage of machine parts of engines .
3. It Enhances smooth motion of moving parts of machines.
4. It helps in Preventing the expansion of metal due to  frictional heat and
5. Lubricants also help in Minimizing  the possibility of corrosion in iron.

There are 3 important types of lubrication :-

(1) Boundary lubrication also known as  thin film lubrication

(2) Hydrodynamic lubrication also called thick film lubrication and

(3) Extreme pressure lubrication.

Boundary lubrication:-

Boundary lubrication occurs in machine parts of low speed and high load .The film thickness of the lubricant is low as 2-3 molecule thickness with the frictional coefficient being 0.05 to 0.15.In this type it is just impossible to maintain the thick film of lubricant in between the moving surfaces.

Hydrodynamic lubrication:-

Hydrodynamic lubrication takes place in machine parts of high speed .The coefficient of friction is low that is it ranges  from  0.01 to 0.003 .Here a thick film of lubricant separates the two moving parts of machine.

Extreme pressure lubrication:-

The conditions under which this type of lubrication occurs are :

(1)High load

(2)High speed

The lubricant here either vaporizes or decomposes due to local heat .Some addictives are used to overcome this difficulty and are called extreme pressure additives .These additives at high temperature react with metal giving metallic chlorides possessing high melting point and high temperature.

Important Questions and Answers :-

Que >  Define a lubricant and name the various modes  of lubrication  ?

Ans > The substance that helps in reducing  friction between moving surfaces is termed as lubricant and this property of reducing friction is called as lubricity . There are 3 important modes  of lubrication :-

(1)Boundary lubrication also known as thin film lubrication

(2)Hydrodynamic lubrication also called thick film lubrication and

(3)Extreme  pressure  lubrication.

Que > Why are additives used with various lubricants ?

Ans >  The lubricants used in extreme pressure lubrication either decomposes or vaporizes due to local heat . Additives are used to overcome this difficulty and are called extreme pressure  additives . These additives at high temperature  react with metal giving metallic chlorides possessing  high melting point and high temperature .

Que >  What are the characterstics of  lubricants ?

Ans > The characteristics possessed by lubricants are  (1) lubricants are thermally stable.

(2)  lubricants have Low freeing point .

(3)   lubricants have High boiling point.

Que >  Describe some functions of lubricants ?

Ans >  Some  important functions of lubricants are:

(1)Reducing loss of energy as heat dissipation .

(2)Reducing damage of machine parts of engines .

(3)Enhancing smooth motion of moving parts of machines.

(4)Preventing the expansion of metal due to  frictional heat

(5)Minimizing the possibility of corrosion in iron.

Que > Mention the conditions under which  extreme pressure lubrication takes place ?

Ans > The conditions under which extreme pressure  lubrication occurs are :

(1)High load and

(2)High speed of machine parts .

Boundary LubricationINDUSTRIAL LUBRICANTINTRODUCTION AND MECHANISM OF LUBRICATIONSLubrication Typesquestions & answers on Lubrication

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