Chemistry

Instructor details
• Name : Abdul Shakeer
• Email : shakeer_141@rediffmail.com

Today’s Agenda
I. Functions of Lubricants
II. Kinds of Lubricants
III. Origin of lubricants
IV. Processing of Lube Oils
V. How are Lube oils used ?
VI. Lube Oil tests
VII.Brake Oils
VIII.How to choose a lubricant ?

I. Functions of Lubricants
1. Decrease friction between moving surfaces of
machines.
2. Absorb extra heat in the machine , and send it
to the radiator.

I. Functions of Lubricants (Cont’d)
3. In Internal combustion engines , they prevent
gas leakage from the minute distances between
the cylinder and piston rings.
4. Help in carrying some of the solid combustion
products which if not removed , may cause
erosion.

II. Kinds of Lubricants
1. Oils
2. Greases
3. Solid Lubricants
4. Lubricating emulsions.

III. Origin of Lubrication oils
• In the past , vegetable and animal oils were used
(e.g. Castor oil and Olive oil)
• Nowadays , they are replaced by the heavy
paraffinic compounds resulting from oil
refineries.

IV. The process of extraction of
lube oils
?

IV. The process of extraction of
lube oils
1. Vacuum Distillation
• It is conducted at temperatures between 300OC to 350OC , and
at pressures ranging from 30 to 50 mm.Hg
2. De – Asphalting
• Aims to remove Asphalt and naphthenic componuds from the
oil
• Reason : Asphalt increases the viscosity of the oil in a harmful
matter , and naphthenic compounds are oxidizable causing
formation of water and acidic compounds which have harmful
effects on oil viscosity.
• This is done using solvent extraction by Phenol or Furfural.

IV. The process of extraction of
lube oils(Cont’d)
3. De-Waxing
• Aims to remove wax from raw oil.
• Reason : Wax has harmful effects on viscosity.
• This is done by cooling oil to low temperature (-10OC) ,
the wax solidifies and can be filtered easily using rotary
filters

IV. The process of extraction of
lube oils(Cont’d)
4. Finishing
A. By Using Hydrogen Treatment :
• Aim : to remove unsaturated compounds by converting
them into saturated compounds.
• Reason :To prevent the formation of heavy polymers
causing oil blockage.
• Also , hydrogen eliminates sulfur compounds in the oil
and converts them into hydrogen sulfide.
B. By Using Activated Clay:
• Aim : to remove colors , residual waxes and naphthenic

IV. The process of extraction of
lube oils (Cont’d)
5. Introduction of oil Additives:
• Aims to expand the lifetime of the oil , to improve its
efficiency , and its viscosity index (will be discussed
shortly)
• Examples of some additives:
1. Additives to prevent oil oxidation
2. Additives to prevent oil erosion
3. Additives to compensate for the decrease in oil
viscosity resulting from high temperature.
4. Additives to prevent solidification by oil , this
additives tend to coat any solidified pellets.

Flow diagram for processing of
raw oil into treated oil
• Was illustrated using the board.

Lube oil tests
1. Viscosity measurements
• In this test , we use an apparatus called Saybolt
• We measure the time in seconds needed for a specific oil
volume to spill through a standard hole.
• The unit of measurement is Saybolt universal second
(S.U.S.)
• Usually , the test is done at 3 different temperatures
which are 100oF,130oF, and 210oF
• Viscosity decreases as temperature increases

Lube oil tests (Cont’d)
2. Viscosity Index (V.I.)
• V.I. expresses the rate of change of oil viscosity with
respect to change in temperature.
• The value of V.I. is high when the oil is perfect ; which
means that the change in viscosity w.r.t. temperature is
low
• For paraffinic oils , this change is very low . And one of
the paraffinic oils (Pennsylvanian oil) is given V.I. of 100
• For naphthenic oils , this change is very high . And one of
the naphthenic oils (Gulf oil) is given V.I. of Zero

Lube oil tests (Cont’d)
2. Viscosity Index (V.I.)
• To evaluate the V.I. of an oil
• Its viscosity is measured at 100OF , and 210OF
• Gulf and Pennsylvanian oils that have the same
viscosity at 210OF as the tested oils are determined.
• Their viscosity at 100OF is determined
• Use the following equation:
V.I.=
𝑉𝑖𝑠𝑐 𝑜𝑓 𝐺𝑢𝑙𝑓 𝑜𝑖𝑙 𝑎𝑡 100℉−𝑉𝑖𝑠𝑐 𝑜𝑓 𝑂𝑖𝑙 𝑋 𝑎𝑡 100℉
𝑉𝑖𝑠𝑐 𝑜𝑓 𝐺𝑢𝑙𝑓𝑜𝑖𝑙 𝑎𝑡 100℉−𝑉𝑖𝑠𝑐 𝑜𝑓 𝑃𝑒𝑛𝑛 𝑂𝑖𝑙 𝑎𝑡 100℉

Lube oil tests (Cont’d)
3. Oxidation resistance test
• Oxygen is passes over an oil sample in a standard way.
• If the oxidizing ability of the oil is high , the oil turns
turbid due to the oxidation of some of its components
and formation of water.
• This oil is considered as a bad oil

Lube oil tests (Cont’d)
4. Sediments test:
• An oil sample and diluted with alcohol , then it enters a
centrifuge machine to assure the removal of any solids or
remaining activated clays or additives

Oil Cycle
• Was explained using the board.

Greases
A. Their composition
• Lubrication oils dispersed in a soap material
• During operation , soap acts as a velvety surface which
carries the lube oil.
B. When to use them?
1. In places where it is hard to make an oil cycle.
2. When lubricated locations are exposed to water and
dust.

Greases
C. Kinds of greases
• Greases differ in the kind of oil used , and the kind of
acidic and mineral radicals of the used soap , and their
percentages.

Greases
Calcium
Grease
Sodium
Grease
Lithium
Grease
Silicon
Grease
Composition Calcium soap +
Lube oil
Sodium soap +
Lube oil
Lithium soap +
Lube oil
Lithium soap +
Silicon Lube oil
Water resistant Yes No , dissolves
in water
Yes -------------------
Used in Tractors and
Pumps
---------------- Plane parts Space crafts
and Ultra sonic
planes
Working Temp <60OC <80OC Can bare low
temp down to -
5OC
From -7OC to
300OC
Notes Most
commonly
used grease
-------------- Expensive Can last to
1000 working
hours

Solid Lubricants
• At high temperatures , powders of solid materials are
used.
• Molybdenum sulphide and Graphite are the two most
commonly used lubricants.
• At temperatures below 900OC, Molybdenum Sulphide is
used , while at higher temperature Graphite
predominates.

Solid Lubricants (Cont’d)
• Usually , they are mixed with compressed gas or liquid ,
and sprayed from bottles , or they can used in the form
of coatings.
• An example of using solid lubricants is in Super crafts.
• In some cases , some coats of plastics are used as solid
lubricants (e.g. Teflon) and they are replaced every few
years.

Lubricating Emulsions
• They consist of Water+ Oil+ Emulsifier
• They are used usually in cutting and lathing processes ,
where oil lubricates (minimizes friction) and water
absorbs the heat energy produced.
• This decreases the cutting cost as it saves energy
required for cutting + making the cut surfaces smooth.

Brake Fluid Oil
Properties of a typical brake oil
1. It should NOT attack the metal or the piston.
2. The oil should be chosen so that it will not be absorbed
by the piston and consequently , cause its expansion.
3. Surface tension of the oil should be reasonable to
prevent its leakage from the piston.
4. Its V.I. should be high.
• Castor oil diluted to 25% by volume with amyl or butyl
alcohol is very satisfactory , an erosion inhibitor can be
added.

Choice of a lubricant
Factors to consider:
1. Speed , load , and the Physical conditions of the moving
metal surfaces inside the engines.
2. Viscosity of lubricant should not vary with temperature
3. Lubricant should resist all harmful chemical reactions
during its operation.

Choice of a lubricant (Cont’d)
Example
• For any lubricated parts which moves on a circular path , 2 opposite
forces exist:
1. A force that adheres the oil to the moving part:
• this is the friction force between the lubricant and the moving part
• This force is directly proportional to the number of revolutions per
unit time (N) and the viscosity (Ƞ) :F α N*ƞ
2. A Force that repels the lubricant away from the moving part:
• Which is the centrifugal force which is directly proportional to N2
The suitable oil is the one whose viscosity is slightly higher than the
centrifugal force at the operation temperature at the higher possible
velocity.