1. Types of lubricants in modern industry
Semira Hajrlahovic Mehic, M.Sc.
Inspector Counsellor
Chemicals Office of the Republic of Slovenia

2. Overview Friction What is lubrication Regimes of lubrications
Types of lubrications
Lubricants
Formulation of lubricants
Classification of lubricants
General capabilities expected from lubricant
Parameters important for lubricants

3. Friction When on surface moves over the another surface,
Resistance to relative motion of the surfaces arises

4. Friction
May be defined as the opposing force set up between the surface of contact, when one body moves over the surface of another body

5. Friction
When we look at the solid surface it appears smooth to naked eye
but this smooth surface shows irregularities of projections and cavities when viewed under high power microscope

6. Control of Friction

7. What is lubrication
Lubrication is the process, or technique employed to
reduce wear of one or both surfaces in close proximity, 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

8. The regimes of lubrication
Mode of lubrication is called regime of lubrication:
as the load increases on the contacting surfaces
three distinct situations can be observed
Fluid film 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
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
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

9. 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
Hydrodynamic lubrication or thick film lubrication
Hydrostatic lubrication
Boundary lubrication or thin film lubrication
Extreme pressure lubrication

10. Hydrodynamic lubrication or thick film lubrication
Exists when the moving surfaces are separated by the pressure of a continuous unbroken film/layer of lubrication
In this type of lubrication, the load is taken completely by the oil film
Hydrodynamic lubrication depends on:
relative speed between the surfaces, oil viscosity, load, and clearance between the moving surfaces
Application of hydrodynamic lubrication:
Delicate instruments
Light machines ( watches, clocks, guns, sewing machines)
Scientific instruments

11. Hydrodynamic lubrication or thick film lubrication

12. Hydrostatic lubrication
Essentially is 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

13. Hydrostatic lubrication
Examples:
The cross head pin bearing in two stroke engines employs
In the cross head bearing, the load is very high and the motion is not continuous as the bearing oscillation is fairly short
Under such conditions, hydrostatic lubrication offers the advantage as hydrodynamic lubrication cannot be achieved
The oil is supplied under pressure at the bottom of bearing.
The lube oil pump pressure is related to the load, bearing clearance, and thickness of the oil film required

14. Boundary lubrication or thin film lubrication
Exists when the operating condition are such that it is not possible to establish a full fluid condition
particularly at low speeds between the moving/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

15. Boundary lubrication or thin film 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

17. 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
Additives are organic compounds like :
chlorine (chlorinated esters),
sulphur (sulphurized oils),
phosphorus (tricresyl phosphate)

18. What is lubricant? A lubricant :
is a substance/mixture introduced to reduce friction between surfaces in mutual contact
property of reducing friction = known as lubricity
Ultimately reduces the heat generated when the surfaces move
Generally composed of a majority of base oil plus a variety of additives to impart desirable characteristics

19. Applications of lubricants
Industrial
Hydraulic, Air compressor, Gas Compressor, Gear
Bearing and circulating system
Refrigerator compressor
Other motors (2 stroke engine oil)
Aviation, marine, biomedical applications

20. Lubricants
Automotive Industry-Engine oil, Automatic transmission fluid, Gearbox fluid, Break fluids

21. Functions of lubricants
Keep moving parts apart
Reduce friction
Transfer heat
Carry away contaminants & debris
Transmit power
Protect against wear
Prevent corrosion
Seal for gasses
Stop the risk of smoke and fire of objects

22. Formulation of lubricants
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)

23. Classification of lubricants
By the origin
animal (e.g., sperm oil, goose grease),
vegetable (e.g., soybean oil, linseed oil), or
mineral (e.g., petroleum, molybdenum sulfide)
From ancient times until the late 19th cent. lubricants were obtained from vegetable oils or animal fats and oils

24. Classification of lubricants
Today most derive from mineral oils,
such as petroleum and shale oil, which can be distilled and condensed without decomposition
Synthetic lubricants, such as silicones, are of great value in applications involving extreme temperatures
polyglycols, silicones, organic amines, imines
In certain types of high-speed machinery films of gas under pressure have been successfully used as lubricants

25. Classification of lubricants
Solid lubricants
wax, talc, molibdenum disulphide
Semi solid lubricants
grease and vaseline
Liquid Lubricants
mineral oils, vegetable oils, animal oils

27. Solid lubricants
Posse lamellar structure preventing direct contact between the sliding surfaces even at high loads
graphite and molybdenum disulfide particles
boron nitride, tungsten disulfide and polytetrafluorethylene (PTFE), talc

28. Solid lubricants Mainly used as additives to oils and greases
Used in form of dry powder or as constituents of coatings
Added or alloyed into the surface when the component is being manufactured

29. Semi-fluid lubricants (greases)
Produced by emulsifying oils or fats with metallic soap and water at °F ( °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, salts of long-chained fatty acids) and
additives (extra pressure, corrosion protection, anti-oxidation)

30. Semi-fluid lubricants (greases)
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

31. Fluid lubricants (oils)
Mineral fluid lubricants are based on mineral oils
Mineral oils (petroleum oils) are products of refining crude oil
Types of mineral oil:
Paraffinic; produced either by hydrocracking or solvent extraction process
Naphtenic; produced from crude oil distillates
Aromatic ; products of refining process in manufacture of paraffinic oils

32. Self-lubricating composites
Self-lubricating composites have been available for a long time
Used rather extensively by industry to combat friction and wear in a variety of sliding, rolling, and rotating bearing applications
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 :Ti, TiN, TiC, Pb, PbO, ZnO, Sb2O3

33. General capabilities expected from an engine lubricant
Dispersivity or capacity to keep the cold parts of an engine clean
Detergency or capacity to keep hot parts of an engine clean
Thermal strength or capacity to withstand temperature changes
Anti-oxidant or capacity to resist the action of oxygen

34. General capabilities expected from an engine lubricant
Anti-wear or capacity to contain wear
Anti-scuffing or capacity to preserve oil film even in the presence of high pressures
Alkalinity reserve/capacity to neutralize acids formed during combustion
Demulsibility or capacity to separate contaminants

35. General capabilities expected from an engine lubricant
Resistance to hydrolysis or capacity to withstand the action of water which can affect additives
Pumpability, centrifuge ability and filterability or capacity to separate insoluble elements
Anti-rust, anti-corrosive and anti-foam
just some of the other properties which protect the metalic object from wear down

36. Parameters important for lubricants
Viscosity
Iodine number
Aniline point
Emulsion number
Points: drop, cloud, pour and neutralization
Saponification number

37. Viscosity It’s a measure of a fluid’s resistance to flow
Determines performance under operating conditions
A low viscosity oil is thin and flows easily , a high viscosity oil is thick and flows slowly
Too low viscosity of the liquid →lubricant film cannot be maintained between the moving surfaces
Too high viscosity of the liquid → excessive friction
Selected lubricant must be proper viscous
Usually expressed in centipoise or centistoke

38. Viscosity Index
The rate at which viscosity of a lubricant changes with temperature
Silicones, polyglycol ethers, Diesters or triesters have high viscosity index
Higher V.I., lesser is the variation of viscosity with change in temperature
thus, a good lubricating oil should possess high V.I.

39. Iodine number Each oil has its specific Iodine Number
Iodine Number determines the extent of contamination of oil
Low Iodine Number is desirable in oils

40. Aniline Point The temperature at which separation of Aniline
and oil takes place
Aniline Point is a measure of aromatic content of the lubricant
Low Aniline Point →oil have high aromatic %
Higher Aniline point means low % of hydroca-robons (desirable)

41. Emulsion number
Emulsification is the property to get mixed with water easily
A good lubricating oil should:
form such an emulsion with water which breaks easily (property is called demulsification)
have lower demulsification number
Quicker the oil separates out from the emulsion formed, better is the lubricating oil

42. „Points“:drop, cloud, pour and neutralization point I
All paraffinic mineral oil base stocks contain small amounts of waxy materials
Drop point is the temperature at which grease passes from the semi-solid to the liquid state
So, it determines the upper temp. limit for the applicability of grease

43. „Points“: drop, cloud, pour and neutralization point II
When the temperature of the oil is decreased, some of the waxy components come out of solution as tiny crystals, and the solution begins to appear hazy to the naked eye
The temperature at which this occurs is called the cloud point
Pour point:
The lowest temperature at which the oil is fluid
Both indicates suitability of lubricant in cold conditions (and thus must be low for oils)

44. Points“ :drop, cloud, pour and neutralization point III
Determines acidity or alkalinity of oil
As neutralization point of oil increases, age of oil decreases

45. Saponification number
It’s the mg of KOH required to saponify 1 g of oil
Mineral oils do not react with KOH and are not saponifiable
Vegetable and animal oils have very high saponification values
Significance:
each oil has its specific saponification number
deviation from it indicates the extent of adulteration
helps us to ascertain whether the oil reference is mineral or vegetable oil

46. How to go on? Many types of lubricant available
To choose/develop wright lubricant:
Know and understand the logic of process
Type of friction, operational conditions
Properties/characteristic of lubricants

47. semira.hajrlahovic-mehic @gov.si
Thank you!