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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

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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.

GreasesA. 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.

GreasesCalcium Grease

SodiumGrease

LithiumGrease

SiliconGrease

Composition Calcium soap + Lube oil

Sodium soap + Lube oil

Lithium soap + Lube oil

Lithium soap + Silicon Lube oil

Water resistant Yes No , dissolvesin 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.