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CHEMISTRY > LUBRICANTS > Flashcards

LUBRICANTS Flashcards

1
Q

Lubricants

A

Substances which are used to reduce the friction and deformities between two moving/sliding surfaces.

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2
Q

Function of a lubricant

A

1) Reduce friction
2)As a coolant
3)Reduce wear and tear
4)As a sealing material
5)Prevent corrosion
6)Transmit fluid power
7)Improve efficiency of a machine

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3
Q

Types of Liquid lubricants

A

Animal Oil
Vegetable Oil
Mineral Oil
Blended Oil

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4
Q

Animal Oil

A

Extracted from animal bodies.
Ex: bone oil, cod-liver oil, lard oil

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5
Q

Vegetable oil

A

Extracted from plants
Ex: Coconut, sunflower, mustard oil

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6
Q

Mineral Oil

A

Extracted from earth
Ex: Petrol, diesel, crude oil

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7
Q

Blended Oil

A

Mixed according to requirements

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8
Q

Types of Blended Oil

A

1) Lubricant protective additives (LPA)
2)Surface Protective Additives (SPA)
3)Performance Additives

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9
Q

Types of LPA

A

Antioxidants
Metal deactivator
Anti-foamants

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10
Q

Antioxidants

A

Retards oxidative decomposition
Ex: Aromatic Amines, Hindered Phenol

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11
Q

Metal Deactivators

A

Decreases catalytic activity on Oxidation rate
Ex: Amines, Sulphide, Phosphides

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12
Q

Anti-foamants

A

Prevent persistent foam formation
Ex: Silicon Polymers

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13
Q

Types of SPA

A

Rust and corrosion inhibitors
Anti-wear agents
Friction modifiers
Detergents
Dispersants

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14
Q

Rust and corrosion inhibitors

A

Prevents rusting and corrosion of metal parts in contact with the lubricant
Ex: Metal Phenol, Fatty acid, Amines

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15
Q

Friction modifier

A

It changes the coefficient of friction
Ex: Organic fatty acids, Amines, Phosphoric acids, ester, etc..

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16
Q

Anti wear agent

A

Reduces wear and tear
Ex: zinc dithiophosphate, organic phosphates

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17
Q

Detergents

A

Keep surface deposit free
Ex: magnesium phenolates, phosphates , etc.

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18
Q

Dispersants

A

Keep the lubricant’s insoluble contaminants dispersed in the liquid
Ex: thiophosphates, alkylsuccinimides

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19
Q

Types of performance additives

A

Viscosity modifier
Pour point depressants

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20
Q

Viscosity modifier

A

Reduces the rate of viscosity change in temperatures
Ex: Polymers and copolymers of oletins, alkylated styrenes, etc

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21
Q

Pour point depressant

A

Enables lubricants to flow at low temperatures
Ex: polymethacrylates, phenolic polymers

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22
Q

Semi solid Lubricants

A

AKA grease
made from petroleum products

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23
Q

Types of Grease

A

Cap grease
Soda based grease
Lithium based grease
Axle based grease

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24
Q

Cap grease

A

Petroleum product + Calcium soap of fatty acid + water

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25
Q

Conditions of Cap grease

A

under 80 degree Celsius

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26
Q

Calcium soap of fatty acid

A

Oleic acid or stearic acid

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27
Q

Soda based grease

A

petroleum product + sodium soap of fatty acid+ water

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28
Q

Conditions of Soda grease

A

under 175 degree celsius

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29
Q

Lithium based grease

A

petroleum product+ lithium soap of fatty acid + water

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30
Q

Conditions of lithium grease

A

under 15 degree Celsius

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31
Q

problem with Lithium grease

A

Costly

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32
Q

Axle based grease

A

Petroleum product + slaked lime + water + rosin oil

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33
Q

Conditions of Axle grease

A

under 160 degree celsius

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34
Q

Solid lubricant

A

Graphite, molybdenum disulphite

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35
Q

Emultion Lubricant

A

emulsion is a mixture of at least 1 immiscible liquid dispersed in another liquid in form of droplets whose diameter exceeds 0.1 µm.

Used in metal working and cutting

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36
Q

Synthetic Lubricants

A

Manufactured in chemical plants or refineries to produce tailor made products that can lubricate like conventional lubricants but at severe conditions

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37
Q

Characteristics of a good lubricant

A

High BP
Low FP
Adequate viscosity
High resistance to heat and corrosion
non-corrosive properties
stability to decomposition

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38
Q

problem with vegetable oil and animal oil

A

Costly
less resistant to oxidation
thicken in air
hydrolyze easily

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39
Q

How to increase oiliness of mineral oil

A

Adding oleic acid and stearic acid

40
Q

Dewaxing

A

removal of wax from an oil otherwise wax raises the pour point and makes lubricant unfit at low temperatures

41
Q

Additives

A

Material that imparts new or desired properties to the lubricating oil

42
Q

Application of Grease

A

1)In rail axle boxes
2)in bearing and gears that work at high temperatures
3)in machines where dripping of oil is undesirable
4)in situations where bearing needs to be sealed against entry of dust, grit or moisture.

43
Q

Flash point

A

Temperature of lubricant oil at which vapours of any lubricant catch fire

44
Q

Fire Point

A

If vapours of lubricant brun for more than 5 sec at a certain temperature then that temperature is called fire point.

45
Q

Lubrication

A

process or technique applied to reduce friction and wear between 2 relatively sliding or moving surfaces by interposing a lubricant between the surfaces to carry or to help carry the load

46
Q

Tribology

A

Science of friction,lubrication and wear

47
Q

Mechanisms of Lubrication

A

Hydrodynamic or fluid film lubrication
Boundary lubrication or thin film lubrication
extreme pressure lubrication

48
Q

difference btw mechanisms of lubrication

A

Book pg no 111

49
Q

Acid refining of mineral oils

A

Treatment with conc.H2SO4 so that asphaltic and naphthenic impurities and other undesirable constituents can be eliminated from dewaxed oil

50
Q

Chemically active additives

A

those which chemically react with the metals and with polar oxidation and degradation products.

51
Q

Chemically inert additives

A

those which improve the physical properties that are critical to the effective performance of the lubricant

52
Q

Non newtonian lubricant

A

grease

53
Q

Grease with water

A

fiber structure of thickener is adversely affected by water and the grease undergoes degradation

54
Q

Consistency value or yield value

A

distance in tenths of a millimeter that a standard cone penetrates vertically into the sample of grease under the standard conditions of load(150gm), temperature (25C) and time (5s)

55
Q

Factors affecting consistency of grease

A

1) structure and interactions of the gelling elements in it
2)viscosity of oil used in preparation of the grease

56
Q

Determination of consistency of grease

A

penetrometer

57
Q

Drop point

A

temperature at which grease passes from semi-solid state to liquid state

58
Q

significance of drop point

A

it determines the upper limit of temperature upto which the grease can function with a satisfactory lubricant

59
Q

Properties of graphite

A

low coefficient of friction
non-inflammable
not oxidized in air

60
Q

aquadag

A

graphite dispersed in water

61
Q

oildag

A

graphite dispersed in oil

62
Q

graphite acts as lubricant on moon

A

cause temperature ranges from 110C in day to -150C in night
absence of air

63
Q

Characteristics of synthetic lubricants

A

1) thermal stability at high temp
2)chemical stability in corrosive environment
3) high viscosity index
4)low freezing point
5) non-inflammability and high flash point

64
Q

advantages of mineral oil and synthetic oil

A

easily dissipate heat
easy to refill and drain
greater range of operating speeds and temperatures

65
Q

limitations of mineral oil and synthetic oil

A

poor sealing abilities
more maintenance
leak proof design required

66
Q

advantages of grease

A

better sealing abilities
easily retained as it is non-newtonian
no need for leak proof design
less maintenance

67
Q

limitation of grease

A

More energy demanding due to higher coefficients of friction
ineffective dissipation of heat
on storage grease seperates into soap and oil

68
Q

advantages of soild lubricants

A

lubrication for lifetime
reduce fretting caused by vibration
they solve lubrication problem caused by abrasive contamination

69
Q

limitations of solid lubricants

A

do not dissipate heat
wear life is less than oil lubricant

70
Q

viscosity

A

property of a fluid that determines its resistance to flow

71
Q

temperature and viscosity

A

inversely proportional to temperature

72
Q

pressure and viscosity

A

proportional to pressure

73
Q

significance of viscosity

A

in lubrication that lubricant is selected which should have a sufficient high viscosity to adhere to the bearing and resist being squeezed out due to high pressure and get fluid enough to resist excessive friction due to the shearing of oil itself

74
Q

Redwood viscometer

A

book pg 127

75
Q

Viscosity index

A

rate at which viscosity of an oil changes with temperature is measured by an empirical number known as viscosity index. a relatively small change in viscosity with temperature is denoted by a high viscosity index

76
Q

pennsylvanian oil

A

it consists mainly of paraffins and are assigned a VI of 100 due to relatively small change in their viscosity with temperature

77
Q

gulf oil

A

it consists mainly of alicyclics and are assigned a VI of 0 due to a large change in their viscosity with temperature

78
Q

Formula for viscosity

A

V.I.=[ (L-U) / (L-H) ] * 100

79
Q

VI and molecular structure of oil

A

a high VI is exhibited by those oils which have a linear or rod like shaped molecules of higher molecular weights

80
Q

VI in terms of Viscosity temperature curve

A

numerical expression of average slope of viscosity temperature curve of a lubricating oil between 100 F and 210 F.

81
Q

significance of flash and fire point

A

used to indicate fire hazards and evaporation losses under high temperature operations

82
Q

factors affecting flash and fire point

A

moisture
low molecular weight
contamination with organic compounds
experimental factors

83
Q

Cloud and pour points

A

temperature at which solidified compounds like paraffin wax present in the oil begin to crystallize or seperate from solution when the oil is cooled under specified conditions

84
Q

significance of cloud and pour point

A

it indicates the suitability of lubricants in cold conditions. lubricants used in a machine working at low temperature should possess low pour-point otherwise solidification of lubricant will cause jamming of the machine

85
Q

aniline point

A

minimum equilibrium solution temperature for equal volume of aniline and oil sample

86
Q

significance of aniline point

A

lower aniline point means higher percentage of aromatic hydrocarbons which means more chances of deterioration of an oil when it comes in contact with rubber sealings etc

87
Q

emulsification

A

property by virtue of which an oil gets mixed with water to form on emulsion

88
Q

demulsibility

A

ability of lubricating oil to seperate from water

89
Q

steam emulsion number (SEN) or demulsification number

A

time in second in which oil and water emulsion separate out in distinct layers . faster they seperate lower the SEN

90
Q

importance of SEN

A

to avoid corrosion of polished steel surfaces like roll necks and to ensure proper lubrication

91
Q

Saponification number

A

the number of milligrams of potassium hydroxide required to saponify the fatty material present in one gram of the oil

92
Q

significance of saponification number

A

helps in calculating
1)avg molecular weight of oil or fat
2)avg length of carbon chain of fatty acid components
3)estimate of non-fatty impurities in oil
4)amount of alkali required for conversion of triglyceride to stop

93
Q

carbon residue

A

lubricating oils contain high percentage of carbon in combined form. On being subjected to high temperature they decompose and form a carbonaceous deposit

94
Q

Total acid number (TAN)

A

the number of milligrams of potassium hydroxide needed to neutralize any acid in one gram of oil

95
Q

Total base number (TBN)

A

number of milligram of hydrochloric acid needed to neutralize any base in one gram of oil

96
Q

significance of TAN and TBN

A

it shows relative changes in an oil due to oxidation. comparing TAN or TBN values of a new oil will indicate the development of harmful products or the affect of additive depletion.

CHEMISTRY (3 decks)

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