Lubricants are substances that reduce friction between moving parts. The document defines lubricants and lubrication, and describes the different types of lubricants according to physical state - solid, semi-solid, and liquid. It then discusses key properties of lubricants including viscosity, flash point, fire point, oiliness, emulsification, carbon residue, decomposition stability, corrosion stability, aniline point, and precipitation number. Lubricants must have properties like proper viscosity, resistance to heat and pressure, and ability to form stable emulsions in order to effectively reduce friction between machine parts.

1. Submitted by-
Vishal Shrivastava

2. LUBRICANTS
The substances which are used
to decrease the force of
friction between the moving
parts of machine in contact are
known as Lubricants
and the
process of decreasing the force
of friction between the moving
parts of machine in contact is
known as Lubrication.

10. Types (According to physical state)
Lubricants
Solid Semi-solid Liquid
e.g. Graphite e.g. Grease e.g. petroleum oil

12. Mineral oil vs. Synthetic

13. Synthetic oils

15. Properties of Lubricants
1. Viscosity:
The property of a liquid or fluid by virtue of which it offers resistance
to its own flow .
(viscosity is inversely proportional to temperature)
viscosity

16. • Flash Point is the min temp at which the lubricant vaporizes that ignite for a
moment when tiny flame is brought near.
• Fire Point is the Min temp at which the lubricant’s vapours burn constantly
for 5 seconds when tiny flame is brought near.
• If flash point < 140°F = Flammable liquids
And if flash point > 140°F =Combustible liquids.
The flash and fire points are generally determined by using
Pensky-Marten’s apparatus.
4

17. 3. Oiliness:
A measure of its capacity to stick on to the surfaces of
machine parts under conditions of heavy pressure or load.
o For high pressure - high oiliness oil should be used.
o Important for extreme – Pressure lubrication
Oiliness

18. 4. Emulsification:
o The property of oils to get intimately mixed with water forming
an emulsion.
o Emulsions have a tendency to collect dirt, girt, foreign material
etc., causing abrasion and wearing out of the lubricating parts
of the machinery.
o A good lubricating oil should form an emulsion with water
which breaks off quickly. emulsificati

19. 5. Carbon residue:
Normally lubricants consist of high % of carbon containing compounds.
o Lubricants decompose due to raise in temp. and deposit carbon creating problems
to :
a) IC engines and b) Air compressors.
o A good lubricant should deposit least amount of the carbon .
6. Decomposition stability:
o Lubricating oils must be stable to decomposition at the operating temperatures
by :
a. Oxidation: To prevent it anti oxidant or inhibitor are used.
b. Hydrolysis: Moisture in oils causes hydrolysis of esters
c. Pyrolysis : At high temperature

20. 7. Corrosion stability:
 Corrosion Test:
o A polished copper strip is placed inside a lubricating oil for
a specified time and temperature and then checked for any
tarnishing .
o To prevent or retard corrosion effect of lubricating oils,
additives such as Phosphorous, Arsenic, Antimony,
Chromium, Bismuth or Lead are added.

21. • Aniline point is the Min temp at which oil is miscible with equal amt of
aniline
• Aniline Point is a measure of aromatic content of the lubricating oil.
• Low Aniline Point oil have high aromatic content which attacks rubber
seals.
• Higher Aniline point means low %age of hydrocarbons (desirable).
Determination of Aniline Point :
Aniline +
sample oil
(equal)
Heated in Test tube
Homogeneous
solution
Cooled
Cloudiness
The temperature at which separation of the two phases (Aniline + oil) takes place
is the Aniline Point.

22. 9. Precipitation Number:
o The percentage of asphalt present in oil after centrifuging oil
solution in petroleum ether.
o Precipitation Number is used to differentiate the different
classes of lubricants.
• It’s the mgs of KOH required to saponify 1 gm of oil.
• Saponification is hydrolysis of an Easter with KOH to give alcohol and Na/K salt of acid.