This presentation is about the Lubricants and lubrication systems, their types and mechanism of lubrication.

1. LUBRICANTS AND LUBRICATION
SYSTEMS
DR. Mahesh Kumar Attri
Mukand Lal National College, Yamuna Nagar,
Haryana-135001, India
1

2. ASPERITIES AND VALLEY
Irregularities on metal surface are called
Asperities (peaks) and valley.
2

3. DEFINITION OF LUBRICANTS
Due to mutual rubbing of one part of a
machine with other, resistance is offered
which is known as friction.
Any substance introduced between two
sliding parts in order to reduce the
friction between them is known as
Lubricants.
3

4. FUNCTIONS OF LUBRICANT
Reduces the friction forces
 Reduces cost of maintenance
 Reduces heating energy produced
due to friction
 Enhances the efficiency of machine.
4

5. MECHANISM OF LUBRICATION
THREE TYPE OF MECHANISM
1. Fluid-film or thick-film lubrication
(Hydrodynamic lubrication)
2. Boundary lubrication (Thin film
lubrication)
3. Extreme pressure lubrication
5

6. 1. FLUID FILM OR THICK-FILM
LUBRICATION (HYDRODYNAMIC
LUBRICATION)
The condition in which surfaces are
completely separated by a continuous film
of lubricating fluid is commonly referred to
as Hydrodynamic or Full Fluid Film
Lubrication. Since thick film of lubricant is
used, hence it is also known as thick film
lubrication.
 This type of lubrication works only when
load is not high. 6

7. EG
7

8. 8

9. 9

10. 10

11. 2. BOUNDARY LUBRICATION
(THIN FILM LUBRICATION)
This lubrication comes into play when thick
film lubrication fails.
This can happen when
Load is very high
 Viscosity of oil is very low
 Speed is very slow
11

12. A type of lubrication in which the
lubricant film is very small between the
two surfaces in contact.
Lubricant gets adsorbed over metal
surfaces by physical or chemical forces.
Metal layer avoid the metal – metal
forces.
e.g. rollers, tractors require such type
of lubrication
12

13. 13

14. Many time, Lubricant film is too thin to
provide total surface separation.
Contact between surface asperities (or
microscopic peaks and valleys) occurs
which causes wear and tear.
14

15. 3. EXTREME PRESSURE LUBRICATION
 When the moving surfaces are working under a very
high pressure and high temperature, the ordinary
liquid lubricants either vaporizes or decomposes.
 In such cases ‘Extreme pressure lubrication’ is
done.
 special additives are used along with the liquid
lubricants eg chlorinated esters, sulphurized oils,
tricresyl phosphate etc are examples of additives.
 these additives forms metallic chlorides, sulphides
and phosphides which form a durable film.
15

16. CLASSIFICATION OF LUBRICANTS
Mainly 3 classes
1. Solid lubricants
2. Semi-solid lubricants
3. Liquid lubricants
16

17. SOLID LUBRICANTS
Lubricants which exist in solid form called
solid lubricants.
 e.g. graphite, molybdenum disulphide,
wax, chalk, talk etc.
Graphite is most commonly used lubricant
bz
it is non flammable,
resist oxidation even at higher temperature.
17

18. CONDITIONS FOR USING SOLID
LUBRICANTS
It is used in machines when
semisolid or liquid lubricants are not
suitable.
 machine is heavy.
 semisolid (grease) or liquid lubricants are
contaminated due to presence of dust
particles.
18

19. Q: WHY GRAPHITE IS USED AS SOLID
LUBRICANTS?
Ans. Due to following reasons
 It is soapy in touch.
 it is non flammable
 it is not oxidized in air
 it can be used in powdered form or in suspension
form.
 when graphite is dispersed in oil, it is called ‘oildag’
and when graphite is dispersed in water, it is called
‘aquadag’
 it has a unique structure. Each C atom is sp2
hybridized and covalently attached to 3 neighboring
carbons.
19

20.  As a result planner hexagonal ring are formed.
These rings forms a layer or sheet which are
held together by weak vander Waals forces.
Due to weak forces layer can slip over each
other and that’s why it is soft and smooth.
20

21. Q: Why molybdnum disulphide is used as solid
lubrocant?
Ans: (i) It has sandwich structure. The layer of
molybdnum atoms lie between two layers of
sulphur atoms. Layers are held together by
weak vander Waal forces that’s why it is soft
and smooth in nature.
 (ii) It is stable up to 400 °C temp.
 (iii) it has low coefficient of friction.
 (iv) It is used in powdered or on additives.
21

22.  Fig. Molybdnum disulphide
22

23. 2. SEMI-SOLID LUBRICANTS
 Lubricants which are neither solid or liquid are
called semi-solid lubricants.
 E.g. grease, Vaseline, waxes, creams etc.
Conditions for using solid lubricants
it is used when
 Machine works under high load or at low speed.
 lubricating oil is not suitable for machines.
 sealing of oil is problematic. 23

24. 3. LIQUID LUBRICANTS
 Lubricants which exist in liquid form and reduce
friction or wear between the metallic surfaces by
providing a continuous film in between them are
called liquid lubricants e.g. animal oil, vegetable oil,
mineral oil (petroleum oil).
Conditions for using liquid lubricants
it is used when
 solid or semisolid lubricants are not suitable.
 machine are operated under low load.
 machine produces low heat. 24

25. CLASSIFICATION OF LIQUID
LUBRICANTS
Animal
Vegetable
Mineral
Synthetic
 blended oil
 emulsions
25

26. ANIMAL LUBRICANTS
 Lubricants with animal origin:
 Whale oil
Seal oil
Lard oil
Neat’s foot oil
Porpoise oil
 These are highly stable at normal temperatures
 Animal lubricants may not be used for internal
combustion because they produce fatty acids
Limitations of animal oil
 Undergo oxidation easily 26

27. VEGETABLE LUBRICANTS
 Examples of vegetable lubricants are:
Castor oil
Olive oil
Cottonseed oil
 Animal and vegetable oils have a lower
coefficient of friction than most mineral
oils.
27

28. MINERAL LUBRICANTS
 These are obtained from fractional
distillation of petroleum.
 They have poor oiliness but they are
widely used as lubricants bz they are
cheap and available in large amount.
 These lubricants are used to a large
extent in the lubrication of aircraft
internal combustion engines.
 Eg petroleum oil
28

29. SYNTHETIC LUBRICANTS
 Because of the high operating
temperatures of gas-turbine engines, it
became necessary to develop lubricants
which would retain their characteristics at
temperatures that cause petroleum
lubricants to evaporate and break down
 Synthetic lubricants do not break down
easily and do not produce coke or other
deposits eg
29

30. BLENDED OIL
 Mixture of two or more oil or any additive
added in oil, resultant mixture is called
blended oil.
 Blended oil has better quality as
compared to their components.
 Some additives are
 Oiliness carrier: cater oil, coconut oil etc.
 antioxidant: amino compounds
 Anti foaming agent: glycol and glycerol.
30

31. EMULSIONS
 Mixture of oil and water is called emulsion.
 It is prepared by vigorous mixing in presence of
emulsifier (stabilizer) eg sodium salt of sulphuric
acid.
 Emulsions are important lubricants which are used
in boring and milling. Two types:
 Oil in water (cutting emulsion): Oil in dispersed
phase and water as dispersion medium. Oil act as
lubricant and water as coolant. It is used in boring,
drilling machines.
 Water in oil (cooling emulsion): Water is dispersed
phase and oil as dispersion medium. It is used in
steam cylinders to keep wall cool with less oil
consumption.
31

32. LUBRICATING OIL PROPERTIES
 Flash Point and fire
point
 Viscosity
 Viscosity index
 Cloud Point and
Pour Point
 Aniline point
 Saponification value
 Iodine value
32

33. FLASH AND FIRE POINT
Flash Point:The flash point of an oil lubricant
is the temperature at which lubricant gives
off sufficient vapor that ignite for a moment,
when a flame is brought near it.
Fire point: The flash point of an oil lubricant is
the temperature at which lubricant gives off
sufficient vapor that ignite (burn) for at least
five seconds, when a flame is brought near
it.
33

34. PENSKY-MARTEN’S APPARATUS TO
MEASURE FLASH POINT AND FIRE
POINT
34

35.  It consist of
 (i) oil cup: It is a metallic cup having diameter 5 cm
and depth 5.5 cm.
 (ii) Shutter: It is provided at top of cup and
controlled with a handle known as shutter
controller.
 (iii) Air bath: oil cup is placed in an air bath bz air is
bad conductor of heat and ensure uniform heating.
 (iv) Pilot burner: It is always lighted automatically to
perform burning test and it is introduced in oil cup
through a hole.
 (v) Flame test burner: it is a burner by which the
test flame is introduced into oil cup containing
lubricating oil and it is supported by a pilot burner.
35

36.  Working:
 Oil is filled in oil cup and heated with constant
stirring.
 for every 1° rise in temperature test flame is
introduced for a moment with the help of a
shutter.
 The temp. at which a distinct flash appears
inside the cup is recorded at as a flash point.
 Heating is continued further and test flame
introduced as before.
 The temp. at which lubricating oil catches fire at
last 5 sec is recorded as its fire point.
36

37. VISCOSITY
 Viscosity of a lubricating oil is defined as the
internal friction offered by the layers of fluid of
its flow.
 Viscosity is a measure of flow ability of a liquid
at a definite temperature.
 It determines the performance of oil under
operating conditions.
 Higher the viscosity of fluid lesser will be its
flow.
37

38.  Coefficient of viscosity is called absolute viscosity is
defined as tangential force per unit area required to
maintain a unit velocity gradient between two parallel
layers a unit apart. It is denoted by η (eta).
Mathematically, η =
Where F = force
A= Area
dv/dx=velocity gradient.
Units: In C.G.S. system poise = dyne cm-2
s
In SI system Nm-2
s.
The absolute viscosity of lubricant is determined by
measuring the time of flow of the oil through a capillary of
definite dimensions at uniform temperature.
The viscosity is can be measured by a Redwood viscometer.
38

39. DESCRIPTION OF REDWOOD
VISCOMETER:
It is available in two sizes. These are:
(i) RW1 or Redwood No. 1 (Universal)
 Diameter of capillary 1.62 mm
 Length of jet 10 mm
(ii) RW2 or Redwood No. 2 (Admirality)
 Diameter of capillary 3.8 mm
 Length of jet 50 mm
39

40. CONSTRUCTION
40

41.  (i) OIL CUP: It has a brass oil cup fitted with an agate jet
of specific dimension in the middle of base and open at the
upper end.
 (ii) Water bath: Surrounding the oil cup is cylindrical
vessel made of copper. This vessel is filled with water and
serves as a water bath to maintain the oil at a desired
temperature of oil. It is heated by means of heating coils.
 (iii) STIRRER: The water bath is provided with stirrer
having four blades to maintain uniform temperature of
bath.
 (iv) Kohlrausch flask: A thermometer is fitted in a water
bath to know the temperature of water at its base. A 50
mL flask called Kohlrausch flask is provided below the jet
to collect the liquid flowing out of the jet. The apparatus
is also provided with leveling screws for its leveling 41

42. PROCEDURE
 Pour the test oil in the cup carefully up to the pointer.
Insert a thermometer and stirrer and cover the lid.
 Place a clean and dry Kohlrausch flask immediately
below and directly in the line with the discharge jet
 Remove the ball when oil attains desired temperature
with one hand and start stop watch with the other hand.
Allow the oil to flow till the flask is filled up to 50 mL
mark. Stop the stop watch and note the time of flow in
seconds.
 Repeat the experiment 3-4 times and record the reading.
 Report the mean value in Redwood seconds and also
mentioning the viscometer used and the test
temperature.
42

43. CLOUD POINT AND POUR POINT
 The cloud point is the temperature at
which the oil becomes cloudy in
appearance is alled cloud point.
 A temp. at which oil do not flow or
solidify called pour point.
43

44. 44
DETERMINATION OF CLOUD POINT
AND POUR POINT

45.  Test tube containing oil is removed from
bath at every 1° fall in temp. and examined.
Temp. at which cloud appears is noted as
cloud point.
 After this cooling is continued and tube is
removed from bath and its flow is checked.
 The temp at which oil does not flow in test
tube is noted as pour point.
45

46. VISCOSITY INDEX
 The rate at which viscosity of oil changes with
temperature is called viscosity index.
 It is used to characterize lubricating oil.
 The viscosity of liquids decreases as temperature
increases.
 if the viscosity of oil is much affected with the rise in
temperature, it is called low viscosity index and vice
versa.
 A good lubricant should have high viscosity index i.e.
no much change in viscosity of oil with increase in
temperature.
 Some lubricant has high viscosity index
 e.g. Silicone, Polyglycol ethers, Diesters, triesters etc.
46

47. DETERMINATION OF VISCOSITY
INDEX
Where
U = Viscosity of oil at 100 °F
L = Viscosity of low viscosity index standard oil (Gulf
oil) at 100 °F
H = Viscosity of high viscosity index standard oil
(Pennysylvanian) at 100 °F
47

48. ANILINE POINT
 It is minimum temp at which equilibrium
exist between aniline and oil sample.
48
DETERMINATION

49.  Firstly aniline and oil are mixed with help if
stirrer in a tube.
 Now mixture is allowed to cool in a cold bath.
 Temp at which cloudiness is observed is
reported as Aniline point.
49
 Saponification or Koettsdoerfer number:
Saponification is process of alkaline hydrolysis of
oils (vegetable or animal) and fats giving soap.
Saponification number is defined as number of
milligrams of KOH required to saponify 1 mg of a
fatty oil.

50.  Add 25 mL of ethyl methyl ketone and 25 mL of alc.
KOH solution to two flasks one having oil and other is
blank.
 Reflux both solution on a water bath and add 7-8 drops
of phenolphthalein indicator to each flask. Titrate the
solution of each flask against N/2 HCl taken in a
burette till pink colour just disappears.
50
CH2 O C
O
R1
CH2 O C
O
R1
CH2 O C
O
R1
+ 3 KOH
CH2
OH
CH OH
CH2
OH
+
R1COOK
R2COOK
R3COOK
(R1, R2, R3 may be same or different)

51.  Saponification number of oil =
51

52. IODINE VALUE OR IODINE NUMBER
 The iodine value (or "iodine adsorption value" or
"iodine number" or "iodine index") is the mass of
iodine in grams that is consumed by 100 grams of
a oil.
 In a typical procedure, the fatty acid is treated
with an excess of the Hanuš or Wijs solutions,
which are, respectively, solutions of iodine
monobromide (IBr) and iodine monochloride (ICl)
in glacial acetic acid. Unreacted iodine
monobromide (or monochloride) is then allowed to
react with potassium iodide, converting it to
iodine, whose concentration can be determined by
titration with sodium thiosulfate.
52

53.  Iodine value =
Significance:
 It determines the degree of unsaturation of
oil.
 It determines the blending percentage in oil.
53

54. BIODEGRADBLE LUBRICANTS
 Lubricants which are easily decomposed when
it is spilled in to water or land without leaving
harmful substances.
 eg Plant based oil like sunflower, mustard oil,
soybean oil.
ADVANTAGE: These are
(i) less toxic (ii) easily available (iii) reduce the
environmental pollution (iv) have low cost (v)
reduce energy consumption (vi) high flash
point and fire point (vii) high viscosity index. 54

55. DISADVANTAGE
 Vegetable oil have low oxidative
stability.
 Vegetable oil have very high pour
point.
55

56. ADDITIVES FOR LUBRICANTS
 Suitable compound which is added to
lubricating oil which enhance the desirable
property.
eg
 Rust inhibitors: alkyl succinic acids and fatty
acids.
 Antifoam additives: Silocones and glycerols
 Emulsifier: monoesters of polyhydric
alcohols, sodium salt of carboxylic acids.
These promote the mixing of oil and water.
56

57. THANKS TO
ALL
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