By

-Abhijit H Jadhav (Roll no 02)

-(Roll no 03)

-(Roll no 04)

*Lubricant

Need of lubricant Introduction Classification of lubricants Characteristics of lubricant Types of lubrication Function of lubricant Application of lubricants Biblography

*Overview

Resistance to the motion (Friction) is created when there is relative motion between two surfaces.

*Need of lubricant

Lubricants are used as a material between surfaces to reduce friction.

A lubricant is a substance introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move.

*Introduction

The process of introducing lubricant is called Lubrication.Functions of lubricants :

Reduces the frictional resistance.Reduces wear & tear, surface deformation

Acts as a coolant Provides protection against

corrosion Improves the efficiency of the

machine

Lubricants are classified on the basis of their physical state as follows:

Liquid Lubricants or Lubricating OilsSemi-Solid Lubricants or greasesSolid Lubricants.

* Classification of Lubricant

Lubricating oils reduce friction and wear  between two moving metallic surfaces by providing a continuous fluid film in between the surfaces.

Examples: Animal and Vegetable oils Petroleum oils Mineral oils Blended oils

* Liquid Lubricants or Lubricating Oils

Grease is a semi solid lubricant obtained bythickening liquid lubricating oil through the addition of a metallic soap.

The thickness isusually sodium or calcium or lithium soap.

Types of greases Soda-base grease Lime-base grease Lithium-soap grease Barium-soap grease

* Semi-Solid Lubricants or greases

Lubricant are solid in state and these are used where

The operating temperature and load is too high Contaminations of lubricating oils or greases by

the entry of dust or grit particles are avoided. Combustible lubricants must be avoided.Graphite

and Molybdenum disulphide are the widely used solid lubricants

*Solid Lubricants.

It must have high boiling point or low vapour pressure.

Thermal stability and oxidation resistance must be high.

It must also have adequate viscosity for particular operating conditions.

The freezing point must be low.

It must also have non-corrosive property.

* Characteristics of lubricant

It reduces the maintenance and running cost of the machine.

It reduces unsmooth relative motion of the moving surfaces.

It reduces the loss of energy in the form of heat that is it acts as a coolant.

It reduces waste of energy, so that efficiency of the machine is increased.

It minimizes corrosion.

*Functions Of Lubricants

*Types of lubrication

Types Of Lubrications

Thick Film or Fluid Film

or hydrodynamic

Lubrication

Thin Film orBoundary Lubrication

This is also called Hydrodynamic or fluid film lubrication.  

The moving/ sliding surfaces are separated from each other by a bulk lubricant film (at least 1000oA thick).

This bulk lubricant film prevents direct surface to surface contact so that the small peaks andvalleys do not interlock

*Thick Film Lubrication

When the lubricant is not viscous enough to generate a film of sufficient thicknessto separate the surfaces under heavy loads, friction may yet be reduced with the proper lubricant

The coefficient of friction is 0.05 to 0.15 Lubricants used for boundary lubrication should

have high viscosity index, resistance to heat and oxidation, good oiliness.

Examples are Organic oils, Vegetable oils, Graphite and Mineral Oils etc.

*Thin Film Lubrication

Used in vehicle Engine as oil. Used as gear box fluid. Hydraulic fuel Air compressor fuel Bearing and circulating system oils Refrigerator compressor oils Steam and gas turbine oils Piston engine oil.

*Application of Lubricants

www.wikipedia.org http://

www.vidyarthiplus.in/engineering-chemistry1-lubricants

www.britannica.com/technology/lubrication

https://books.google.co.in/books www.machinerylubrication.com

*Biblography