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Lubrication
Hafiz Muhammad Zubair
University of the Punjab
Overview
 What is lubrication
 Regimes of Lubrications
 Types of Lubrications
 Lubricants
 Formulation of Lubricants
...
What is lubrication?
 Lubrication is the process, or technique employed to
reduce wear of one or both surfaces in close
p...
The regimes of lubrication
 As the load increases on the contacting surfaces three distinct
situations can be observed wi...
Types of Lubrication
 Considering the nature of motion between moving or
sliding surfaces, there are different types of
m...
Hydrodynamic Lubrication or
Thick Film Lubrication
 Hydrodynamic lubrication is said to exist when the moving
surfaces ar...
Hydrostatic Lubrication
 Hydrostatic lubrication is essentially a form of
hydrodynamic lubrication in which the metal sur...
Boundary Lubrication or Thin
Film Lubrication
 Boundary lubrication exists when the operating condition are
such that it ...
Extreme Pressure Lubrication
 When the moving or sliding surfaces are under very
high pressure and speed, a high local te...
What is lubricant?
 A lubricant is a substance introduced to reduce
friction between surfaces in mutual contact, which
ul...
Formulation
 Typically lubricants contain 90% base oil (most often
petroleum fractions, called mineral oils) and less tha...
Types of Lubricants
 Solid lubricants possess lamellar structure
preventing direct contact between the sliding
surfaces e...
Types of Lubricants
 Semi-fluid lubricants (greases) are produced by emulsifying
oils or fats with metallic soap and wate...
Types of Lubricants
 Fluid lubricants (Oils) Mineral fluid lubricants are
based on mineral oils. Mineral oils (petroleum ...
General properties of
Lubricants
 A good lubricant generally possesses the following
characteristics:
 high boiling poin...
Solid Film Lubricants
 These materials are characterized as dry film or solid
film lubricants.
 These materials may be a...
Self-Lubricating Composites
 Self-lubricating composites have been available for a
long time and are used rather extensiv...
Thank you
Questions and Answers
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Lubrication

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Lubrication

  1. 1. Lubrication Hafiz Muhammad Zubair University of the Punjab
  2. 2. Overview  What is lubrication  Regimes of Lubrications  Types of Lubrications  Lubricants  Formulation of Lubricants  Types of Lubrication  Solid Film Lubrication  Self Lubricating Materials  Q & A Session
  3. 3. What is lubrication?  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.
  4. 4. The regimes of lubrication  As the load increases on the contacting surfaces three distinct situations can be observed with respect to the mode of lubrication, which are called regimes of lubrication:  Fluid film lubrication is the lubrication regime in which through viscous forces the load is fully supported by the lubricant within the space or gap between the parts in motion relative to one another object.  Hydrostatic lubrication is when an external pressure is applied to the lubricant in the bearing, to maintain the fluid lubricant film where it would otherwise be squeezed out.  Hydrodynamic lubrication is where the motion of the contacting surfaces, and the exact design of the bearing is used to pump lubricant around the bearing to maintain the lubricating film
  5. 5. Types of Lubrication  Considering the nature of motion between moving or sliding surfaces, there are different types of mechanisms by which the lubrication is done. They are:  Hydrodynamic lubrication or thick film lubrication  Hydrostatic lubrication  Boundary lubrication or thin film lubrication  Extreme pressure lubrication
  6. 6. Hydrodynamic Lubrication or Thick Film Lubrication  Hydrodynamic lubrication is said to exist when the moving surfaces are separated by the pressure of a continuous unbroken film or layer of lubrication. In this type of lubrication, the load is taken completely by the oil film.  Hydrodynamic lubrication depends on the relative speed between the surfaces, oil viscosity, load, and clearance between the moving or sliding surfaces.  Application of hydrodynamic lubrication  Delicate instruments.  Light machines like watches, clocks, guns, sewing machines.  Scientific instruments.
  7. 7. Hydrostatic Lubrication  Hydrostatic lubrication is essentially a form of hydrodynamic lubrication in which the metal surfaces are separated by a complete film of oil, but instead of being self-generated, the separating pressure is supplied by an external oil pump.  Hydrostatic lubrication depends on the inlet pressure of lube oil and clearance between the metal surfaces, whereas in hydrodynamic lubrication it depends on the relative speed between the surfaces, oil viscosity, load on the surfaces, and clearance between the moving surfaces.
  8. 8. Boundary Lubrication or Thin Film Lubrication  Boundary lubrication exists when the operating condition are such that it is not possible to establish a full fluid condition, particularly at low relative speeds between the moving or sliding surfaces.  The oil film thickness may be reduced to such a degree that metal to metal contact occurs between the moving surfaces. The oil film thickness is so small that oiliness becomes predominant for boundary lubrication.  Boundary lubrication happens when  A shaft starts moving from rest.  The speed is very low.  The load is very high.  Viscosity of the lubricant is too low.
  9. 9. Extreme Pressure Lubrication  When the moving or sliding surfaces are under very high pressure and speed, a high local temperature is attained. Under such condition, liquid lubricant fails to stick to the moving parts and may decompose and even vaporize.  To meet this extreme pressure condition, special additives are added to the minerals oils. These are called “extreme pressure lubrication.”  Additives are organic compounds like chlorine (as in chlorinated esters), sulphur (as in sulphurized oils), and phosphorus (as in tricresyl phosphate).
  10. 10. What is lubricant?  A lubricant is a substance introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces moves. The property of reducing friction is known as lubricity.  Lubricants are generally composed of a majority of base oil plus a variety of additives to impart desirable characteristics.  Lubricants perform the following key functions:  Keep moving parts apart, Reduce friction, Transfer heat, Carry away contaminants & debris, Transmit power
  11. 11. Formulation  Typically lubricants contain 90% base oil (most often petroleum fractions, called mineral oils) and less than 10% additives. Vegetable oils or synthetic liquids such as hydrogenated polyolefins, esters, silicones, fluorocarbons and many others are sometimes used as base oils.  Non-liquid lubricants include grease, powders (dry graphite, PTFE, molybdenum disulfide, tungsten disulfide, etc.)  Dry lubricants such as graphite, molybdenum disulfide and tungsten disulfide also offer lubrication at temperatures (up to 350 °C)
  12. 12. Types of Lubricants  Solid lubricants possess lamellar structure preventing direct contact between the sliding surfaces even at high loads.  Graphite and molybdenum disulfide particles are common Solid lubricants. Boron nitride, tungsten disulfide and polytetrafluorethylene (PTFE) are other solid lubricants.  Solid lubricants are mainly used as additives to oils and greases. Solid lubricants are also used in form of dry powder or as constituents of coatings.
  13. 13. Types of Lubricants  Semi-fluid lubricants (greases) are produced by emulsifying oils or fats with metallic soap and water at 400-600°F (204- 316°C).  Typical mineral oil base grease is vaseline.  Grease properties are determined by a type of oil (mineral, synthetic, vegetable, animal fat), type of soap (lithium, sodium, calcium, etc. salts of long-chained fatty acids) and additives (extra pressure, corrosion protection, anti-oxidation, etc.).  Semi-fluid lubricants (greases) are used in variety applications where fluid oil is not applicable and where thick lubrication film is required: lubrication of roller bearings in railway car wheels, rolling mill bearings, steam turbines, spindles, jet engine bearings and other various machinery bearings.
  14. 14. Types of Lubricants  Fluid lubricants (Oils) Mineral fluid lubricants are based on mineral oils. Mineral oils (petroleum oils) are products of refining crude oil. There are three types of mineral oil: paraffinic, naphtenic and aromatic.  Paraffinic oils are produced either by hydrocracking or solvent extraction process.  Naphtenic oils are produced from crude oil distillates.  Aromatic oils are products of refining process in manufacture of paraffinic oils.
  15. 15. General properties of Lubricants  A good lubricant generally possesses the following characteristics:  high boiling point and low freezing point (in order to stay liquid within a wide range of temperature)  high viscosity index  thermal stability  hydraulic stability  corrosion prevention  high resistance to oxidation.
  16. 16. Solid Film Lubricants  These materials are characterized as dry film or solid film lubricants.  These materials may be applied to a surface in the form of an additive to a fluid lubricant, or in a pure form, and may also be added or alloyed into the surface when the component is being manufactured.  The more common types of materials include the following:  Molybdenum disulfide (MoS2),Polytetrafluoroethylene (PTFE),Graphite, Boron nitride, Talc, Calcium fluoride, Cerium fluoride, Tungsten disulfide
  17. 17. Self-Lubricating Composites  Self-lubricating composites have been available for a long time and are used rather extensively by industry to combat friction and wear in a variety of sliding, rolling, and rotating bearing applications.  They are generally prepared by dispersing appropriate amounts of a self-lubricating solid (as fillers, preferably in powder form) with a polymer, metal, or ceramic matrix.  Examples are Ti, TiN, TiC, Pb, PbO, ZnO, Sb2O3
  18. 18. Thank you Questions and Answers

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