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ME ELECTIVE 1 > LESSON 2 > Flashcards

LESSON 2 Flashcards

1
Q

are the most commonly used lubricants.

A

Mineral Oils

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2
Q

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

A

Mineral Oils

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3
Q

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

A

fossil fuel theory

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4
Q

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.

A

fossil fuel theory.

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5
Q

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

A

kerogen.

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6
Q

The fundamental differences between mineral oils are based on:

A

chemical forms,
sulfur content,
viscosity

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7
Q

There are three basic chemical forms of mineral oil:

A

paraffinic,
naphthenic,
aromatic.

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8
Q

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

A

0.1% and 1%

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9
Q

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

A

0% and 8%.

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10
Q

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

A

viscosity,

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11
Q

cS means?

A

centistoke

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12
Q

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

A

synthetic lubricants

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13
Q

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

A

‘cracking’

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14
Q

____ 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.

A

Water

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15
Q

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

A

Emulsions

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16
Q

The ____ emulsions are used as fire resistant hydraulic

A

‘W/O’

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17
Q

while the ____ emulsions are suitable as metalworking coolants.

A

‘O/W’

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18
Q

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

A

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

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19
Q

They are in fact mixtures of lubricating oils and
thickeners.

A

Grease

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20
Q

What does grease provide?

A

semi-permanent lubrication

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21
Q

The most widespread application of greases is
as

A

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

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22
Q

_______ are also
suitable candidates for grease lubrication.

A

Low maintenance items

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23
Q

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

A

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

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24
Q

it is not effective as a cooling agent.

A

Grease

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25
Q

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

A

Grease

26
Q

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

A

alkali and fatty acid

27
Q

Greases always contain three basic active ingredients:

A

base mineral or synthetic oil, additives
and thickener.

28
Q

Thickeners used in grease?

A

metal soaps and clays

29
Q

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

A

mineral oil

30
Q

Different types of lubricants

A
  1. Mineral Oils
  2. Synthetic Oils
  3. Emulsions and Aqueous Lubricants
  4. Grease
31
Q

The parameter that plays a fundamental role in lubrication

A

oil viscosity.

32
Q

oil viscosity changes with

A

temperature,

33
Q

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

A

oil velocity

34
Q

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

A

temperature
dependent.

35
Q

-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.

A

Dynamic Viscosity

36
Q

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

A

Lubricant density

37
Q

is often used to characterize crude
oils.

A

Density or specific gravity

38
Q

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’.

A

Specific gravity

39
Q

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

A

Density,

40
Q

API

A

(American Petroleum Institute)

41
Q
  • Another standard commonly associated with brine.
A

Baume Gravity Unit, °Baume’ or °
Be’

42
Q

The most important thermal properties of lubricants are

A

specific heat, thermal conductivity
and thermal diffusivity.

43
Q

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

A

Specific heat

44
Q

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

A

Thermal conductivity

45
Q

-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.

A

Dynamic Viscosity

46
Q

the ratio of dynamic viscosity to the density of
the fluid

A

Kinematic Viscosity

47
Q

is th e parameter describing the temperature propagation into the solids

A

Thermal Diffusivity

48
Q

On the other hand, too much sulphur is

A

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

49
Q

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

A

0%
and 8%.

50
Q

For commonly used mineral oils, viscosity varies from about

A

5 [cS] to 700 [cS].

51
Q

spindle oil

A

20 [cS],

52
Q

engine oil

A

between 30 and 300 [cS],

53
Q

bright stock

A

about 600 [cS],

54
Q

mineral oils also have several serious defects, such as

A

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

55
Q

Mineral oils advantage

A

availability and relatively low cost,

56
Q

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

A

polyolefin synthetic lubricant oil from olefins (alkenes).

57
Q

Why water is an attractive extender of lubricating oils?

A

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

58
Q

Disadvantage of emulsions

A

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.

59
Q

Enumerate the Physical Properties of Lubricants

A
  1. Oil Viscosity
  2. Lubricant Density and Specific Gravity
60
Q

Enumerate the Thermal Properties of Lubricants

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

ME ELECTIVE 1 (3 decks)

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