LESSON 2

Question 1

are the most commonly used lubricants.

Answer 1

Mineral Oils

Question 2

They are manufactured from crude oil which is
mined in various parts of the world.

Answer 2

Mineral Oils

Question 3

The commonly accepted hypothesis about the origins of mineral oils is the

Answer 3

fossil fuel theory

Question 4

The theory states that the mineral oils are the result of decomposition of animal and plant
matter in salt water. According to the theory the remains of dead plants and animals were
collected in sedimentary basins, especially in places where the rivers dump silt into the sea.
Over time they were buried and compressed.

Answer 4

fossil fuel theory.

Question 5

Under these conditions the organic matter
transformed into tar-like molecules

Answer 5

kerogen.

Question 6

The fundamental differences between mineral oils are based on:

Answer 6

chemical forms,
sulfur content,
viscosity

Question 7

There are three basic chemical forms of mineral oil:

Answer 7

paraffinic,
naphthenic,
aromatic.

Question 8

It has been demonstrated, for example, that between _____ of
natural sulphur content ensures reduced wear.

Answer 8

0.1% and 1%

Question 9

The sulphur
content varies with the source of crude oil and the range of concentration lies between

Answer 9

0% and 8%.

Question 10

Mineral oils can also be classified by _____, which depends on the degree of refining.

Answer 10

viscosity,

Question 11

cS means?

Answer 11

centistoke

Question 12

that can withstand high temperatures without
decomposing and at the same time will provide a reduced fire hazard.

Answer 12

synthetic lubricants

Question 13

In most cases synthetic hydrocarbon lubricants are produced from low molecular weight
hydrocarbons which are derived from the
_____ of petroleum

Answer 13

‘cracking’

Question 14

____ by itself is a very poor lubricant but
when mixed with oils to form emulsions or when mixed with water-soluble hydrocarbons to
produce an aqueous solution, some useful lubricants can be developed.

Answer 14

Water

Question 15

____ are produced by mixing water and oil with an emulsifier.

Answer 15

Emulsions

Question 16

The ____ emulsions are used as fire resistant hydraulic

Answer 16

‘W/O’

Question 17

while the ____ emulsions are suitable as metalworking coolants.

Answer 17

‘O/W’

Question 18

Emulsions and aqueous solutions are mostly used as _____ and as ______

Answer 18

cutting fluids in the metal working
industry and fire resistant lubricants in the mining industry

Question 19

They are in fact mixtures of lubricating oils and
thickeners.

Answer 19

Grease

Question 20

What does grease provide?

Answer 20

semi-permanent lubrication

Question 21

The most widespread application of greases is
as

Answer 21

low-maintenance, semipermanent lubricants in rolling contact bearings and some gears.

Question 22

_______ are also
suitable candidates for grease lubrication.

Answer 22

Low maintenance items

Question 23

Greases have to meet the same
requirements as lubricating oils but with one extra condition,

Answer 23

the grease must remain as a semi-solid
mass despite high service temperatures.

Question 24

it is not effective as a cooling agent.

Answer 24

Grease

Question 25

It also cannot be used at speeds as high as oil because frictional drag would cause overheating.

Answer 25

Grease

Question 26

Greases are manufactured by adding _________ to a quantity of oil:

Answer 26

alkali and fatty acid

Question 27

Greases always contain three basic active ingredients:

Answer 27

base mineral or synthetic oil, additives and thickener.

Question 28

Thickeners used in grease?

Answer 28

metal soaps and clays

Question 29

What plays the most important role in determining the grease performance?

Answer 29

mineral oil

Question 30

Different types of lubricants

Answer 30

1. Mineral Oils 2. Synthetic Oils 3. Emulsions and Aqueous Lubricants 4. Grease

Question 31

The parameter that plays a fundamental role in lubrication

Answer 31

oil viscosity.

Question 32

oil viscosity changes with

Answer 32

temperature,

Question 33

shear rate and pressure and the thickness of the generated oil film is usually proportional to

Answer 33

oil velocity

Question 34

Knowing the temperature at which the oil is expected to operate is critical as oil viscosity is extremely

Answer 34

temperature dependent.

Question 35

-is defined as the property of a fluid which offers a resistance to the movement of one layer of fluid over another layer of fluid, thus, it is the resisting property of a fluid to shearing force.

Answer 35

Dynamic Viscosity

Question 36

is important in engineering calculations and sometimes offers a simple way of identifying lubricants.

Answer 36

Lubricant density

Question 37

is often used to characterize crude oils.

Answer 37

Density or specific gravity

Question 38

is defined as the ratio of the mass of a given volume of oil at temperature 't1'to the mass of an equal volume of pure water at temperature 't2’.

Answer 38

Specific gravity

Question 39

is the mass per unit volume of oil [kg/m3].

Answer 39

Density,

Question 40

API

Answer 40

(American Petroleum Institute)

Question 41

- Another standard commonly associated with brine.

Answer 41

Baume Gravity Unit, °Baume’ or ° Be’

Question 42

The most important thermal properties of lubricants are

Answer 42

specific heat, thermal conductivity and thermal diffusivity.

Question 43

varies linearly with temperature and increases with increasing polarity or hydrogen bonding of the molecules.

Answer 43

Specific heat

Question 44

also varies linearly with temperature and is affected by polarity and hydrogen bonding of the molecules. The

Answer 44

Thermal conductivity

Question 45

-is defined as the property of a fluid which offers a resistance to the movement of one layer of fluid over another layer of fluid, thus, it is the resisting property of a fluid to shearing force.

Answer 45

Dynamic Viscosity

Question 46

the ratio of dynamic viscosity to the density of the fluid

Answer 46

Kinematic Viscosity

Question 47

is th e parameter describing the temperature propagation into the solids

Answer 47

Thermal Diffusivity

Question 48

On the other hand, too much sulphur is

Answer 48

detrimental to the performance of the machinery,it may accelerate the corrosion of seals.

Question 49

The sulphur content varies with the source of crude oil and the range of concentration lies between

Answer 49

0% and 8%.

Question 50

For commonly used mineral oils, viscosity varies from about

Answer 50

5 [cS] to 700 [cS].

Question 51

spindle oil

Answer 51

20 [cS],

Question 52

engine oil

Answer 52

between 30 and 300 [cS],

Question 53

bright stock

Answer 53

about 600 [cS],

Question 54

mineral oils also have several serious defects, such as

Answer 54

oxidation and viscosity loss at high temperatures, combustion or explosion in the presence of strong oxidizing agents and solidification at low temperatures.

Question 55

Mineral oils advantage

Answer 55

availability and relatively low cost,

Question 56

A prime example of this method of lubricant synthesis is the production of a

Answer 56

polyolefin synthetic lubricant oil from olefins (alkenes).

Question 57

Why water is an attractive extender of lubricating oils?

Answer 57

cheap, good heat transfer characteristics and non-flammability are all useful attributes.

Question 58

Disadvantage of emulsions

Answer 58

The most severe limitation of these lubricants is the temperature range at which they can successfully be applied. They are limited to the temperature range of water, which lies between the melting point of ice and the boiling point of water.

Question 59

Enumerate the Physical Properties of Lubricants

Answer 59

1. Oil Viscosity 2. Lubricant Density and Specific Gravity

Question 60

Enumerate the Thermal Properties of Lubricants

Answer 60

1. Specific Heat 2. Thermal Conductivity 3. Thermal Diffusivity