Lubricants in Engineering Chemistry
Course:
B.Tech.
Subject: Engineering
Chemistry
Unit:
V
(
B
)
undefined
D
EFINITION
:
L
UBRICANTS
A lubricant is substance (often liquid)
introduced between
two moving
surfaces
to
reduce the friction between
them.
Fluid
which
is
introduced
in between
moving
parts in order to reduce the
friction,
generated heat &
wear
and tear of
machine
parts are called
Lubricants.
This process of introducing lubricant is
called
Lubrication.
Automotive
Oils
Gear and
Transmission
oils
A
u
tomotive
Grease
C
OMPOSITION
Non liquid lubricants contains
Grease,
g
r
aphite,
Mol
y
b
d
enum
T
eflon
tape
u
sed
in
powder(dry
disulphite),
plumbing
etc.
Tho
s
e
non
liquid
l
u
b
ricants
p
r
o
v
i
de
l
u
b
r
ic
a
tion
a
t
hig
h
er
te
m
p
.
(
u
p
to
350
°C)
ADDITIVES
USED
IN
LUBRICANTS
(1)
Anti oxidant --- Aromatic
amines,Phenols,Sulphides and
phosphates
(2)
Corrosion Inhibitor
---
Amino
salts and
salts
of sulphonic
acids
(3)
Antiwear agents ---
Tricresyl
phosphate
(4)
Foam inhibitors
---
Glycerols
Functions of Lubricants
It acts as a thermal barrier and reduces friction
and wear and prevents welded
joints
Avoids
seizure of moving
surfaces
Acts
as
coolant
Acts
as
a seal and prevents entry of
dust,
moisture, &
dirt
between moving
parts
Some lubricants
acts as
corrosion
inhibitors
thus
reduce operational cost
.
A good lubricating
oil
should
have:
•
High
boiling
point
•
Adequate
Viscosity
•
Low freezing
point
•
High oxidation
resist
•
Non Corrosive
properties
•
Good thermal
stability
2
Types
Of
Lub
r
ic
a
t
i
ons
Thick
Film
or
Fluid
Film
or
hydrody
n
a
m
i
c
Lubrication
Thin
Film
or
Boundary
Lubrication
Extreme
Pressure
Lub
r
ic
a
t
i
on
•
•
This is also called
Hydrodynamic
or
fluid film
lubrication.
Two
sliding
metal
surfaces
are
separated from each other by
a
o
thick film of fluid (
1000
A
thick).
•
The coefficient of friction in such
cases is as low as 0.001 to
0.03
•
Lubricants used :
Hydrocarbon
Oils.
•
Provided in delicate instruments
such as watches, clocks, light
machines like sewing machines,
scientific instruments
etc.
•
•
•
•
•
This lubrication is also
called
Boundary
Lubrication.
Its used for high load conditions.
Very
thin film of the lubricant is
adsorbed on the surface by
physical
or
chemical
forces or
both.
The
coefficient
of
friction
is 0.05
to
0.15
Lubricants used for
boundary
•
lubrication
should have
high
viscosity
index, resistance to heat and
oxidation, good
oiliness.
Examples
are
Organic
oils,
Vegetable
oils, Graphite and
MoS
2
,
Mineral
Oils
etc.
•
This lubrication is
for
very
high
press/temp/speed
sliding
surfaces
.
•
Extreme pressure
additives
are used
along
with
the
lubricants.
•
Chemicals used are
compounds of
Cl, S &
P.
•
These additives form solid
surface
films
of
Cl, S &
P.
•
•
High
melting
point
metal
compounds are
good
lubricants.
E.g. graphite is used for
drawing
wires made
up of
mild
steel.
3
Classification
of
Lubricants
Liquid
Lubricants
Eg.Mineral
Oil,
Petroleum
Oil,
Vegetable Oil
etc
Semi
Solid
Lubricants
Eg.
Petroleum
jellies
Synthetic
Lubricants
Solid
Lubricants
Eg.
Graphite,
Molybdenum
Disulphide
etc.
T
YPES
OF
L
UBRICANTS
Solid lubricants
e.g
Wax,
Talc,
Mica,
Molibdenum
disulphide
Semi
solid lubricants
e.g. Grease and
Vaseline
Liquid Lubricants
e.g. Mineral oils,
Vegetable
oils,
Animal
oils
Synthetic lubricants
e.g.
Polyglycols,
Silicones,
Organic
amines, Imines,
Amides.
F
EATURES
OF
L
UBRICANTS
Increase efficiency
and reduce
wear
Dissolving or transporting foreign particles
and
distributing
heat
Single
largest
application
is in form
of
Motor
Oil,
protecting internal combustion engines in
motor vehicles
and powered
equipments
Another approach
is to use ball bearings,
roller
bearing or
air
bearings which in turn require
internal lubrication
themselves
•
It’s
a
measure
of a
fluid’s
resistance to
flow.
•
Viscosity
of
the
lubricating
oil
determines its performance
under operating
conditions.
•
A
low
viscosity oil is thin and flows easily
.
•
A high viscosity oil is thick and flows
slowly.
•
As oil heats up it becomes
more
viscous (
Becomes
thin)
•
Too
low
viscosity of the
liquid
> Lubricant film cannot
be
maintained between the moving surfaces > Excessive
wear.
•
Too
high viscosity of
the
liquid > Excessive
friction.
•
Selected Lubricant
must
be proper
viscous.
•
Viscosity
is usually expressed in centipoise or
centistoke.
•
Iodine
number is
the
number
of
Gms
equivalent of iodine
to
amount
of ICl absorbed by
100gm
of
oil.
•
Each oil
has
its specific Iodine
Number.
•
So
Iodine
Number determines
the extent of
contamination
of
oil.
•
Low Iodine
Number
is desirable in
oils.
Some
oils and their Iodine
Numbers
are given below
:
Iodine
Number
Oil
Example
>
150
Drying
oil
Linseed oil, tung
oil
100-150
Semidrying
oil
Castor oil , Soyabean
oil
<
100
Non-Drying
oil
Coconut oil, Olive
oil
•
Aniline
point
is
the
Min
temp
at
which
oil
is
miscible
with
equal
amt
of
aniline
Aniline Point
is
a
measure
of
aromatic
content of the lubricating
oil.
•
•
Low
Aniline Point
oil have
high aromatic
content
which attacks
rubber
se
a
l
s
.
Higher Aniline point
means
low %age of hydrocarbons
(desirable).
•
•
Thus
Aniline
Point
is
used
as
an
indication
of
possible
deterioration
of
rubber sealing
etc.
Determination of
Aniline
Point
:
Aniline
+
sample
oil
(equa
l
)
Heated in
Test
tube
Ho
m
ogen
e
ous
solution
Cool
e
d
Cloud
i
ness
The temperature at which separation of the two phases (Aniline + oil) takes
place
is
the Aniline
Point.
•
Emulsification
is the property of water
to
get
mixed
with water
easily.
•
Emulsions can
be
oil in
water
emulsion
or water
in
oil
emulsion.
•
A good
lubricating oil
should form such an
emulsion
with
water
which breaks
easily.
This
property is
called
demulsification.
•
The
time
in seconds in which a
given
volume
of
oil and
water
separates
out
in
distinct
layers is
called steam
demulsification
number.
•
A good
lubricating oil
should
have lower demulsification
number.
•
Quicker
the oil separates
out from the
emulsion formed, better
is the
lubricating oil.
•
In
cutting oils
the higher the
emulsification
number,
better the
oil
is.
This
is because the
emulsion
acts as a coolant as well as a
lubricant.
•
Flash Point is the
min temp
at which the lubricant vaporizes that
ignite
for
a
moment
when
tiny flame
is brought
near.
•
Fire
Point is the
Min
temp
at which the
lubricant’s
vapours burn constantly
for
5 seconds when
tiny flame is
brought
near.
•
If flash point <
140°F
=
Flammable
liquids
And
if flash point >
140°F
=Combustible
liquids.
The flash and fire points are generally determined by
using
Pensky-Marten’s
apparatus.
•
Oil
under examination
is
filled in the oil cup up to the
mark
and heated by the air bath by a
burner.
•
Stirrer
is
worked b/n
tests
at a rate of about 1 – 2
rev/sec.
•
Heat is
applied
so
as to raise the oil
temp
by about
5c/min.
•
The
temp
at which distinct flash appeared in
side
the oil
cup
is recorded as
flashpoint.
•
The heating
is
continued to record the fire
point.
4
•
Drop Point is the
Temperature
at
which grease passes from the
semi-
solid
to the liquid
state.
So, it
determines
the upper
temp limit
for
the
applicability
of
grease.
Determination
:
Beaker is
heated.
Temperature
is
raised.
•
•
•
Grease
sample
passes from a
semi-
solid
to a fluid
state.
•
Temp
at which
its
first drop
falls
from the opening is recorded
as
drop-point.
5
•
Cloud Point
is
the
temp
at which the
lubricant
becomes cloudy or hazy when
cooled.
•
P
o
ur
P
o
int
is
the
t
e
m
p at
w
hich
the
l
u
b
ri
c
ant
just
ceases
to
flow
when
cooled.
•
Both
indicates suitability
of lubricant in cold
conditions and thus
must
be
low.
•
It’s
the
mgs
of KOH required to
saponify
1 gm of
oil.
•
Saponification
is hydrolysis of an
Easter with
KOH to
give alcohol and Na/K salt of
acid.
U
S
E
S
Other
uses
are
for
cooking,
biomedical
applications on
human(lubricants
for
artificial
joints).
A
PPLICATIONS
Automotive
Industry-Engine
oil,
Automatic
transmission fluid, Gearbox fluid, Break
fluids.
Tractor(One
lubricant for all
systems)
Other motors(2 stroke
engine
oil)
Industrial(Hydraulic oils, Air compressor oils,
Gas
Compressor oils, Gear oils Bearing and
circulating system oils, Refrigerator compressor
oils)
Aviation
Marine
R
EFERENCES
1.
www.motosport.com
2.
www.umongo.co.za
3.
http://www.vidyarthiplus.in/2012/01/engineering-
chemistry1-lubricants.html#
4.
www.aimil.com
5.
www.machinerylubrication.com
6.
A
textbook
of
Engineering Chemistry by
Shashi
chawla
Lubricants are substances introduced between moving surfaces to reduce friction, heat generation, and wear and tear of machine parts. They act as thermal barriers, coolants, seals, and corrosion inhibitors. Good lubricating oils have high boiling points, adequate viscosity, and non-corrosive properties. Various types of lubrication include thick film, thin film, and extreme pressure lubrication. Additives such as antioxidants and antiwear agents enhance the performance of lubricants.
Download Presentation
Please find below an Image/Link to download the presentation.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.
You are allowed to download the files provided on this website for personal or commercial use, subject to the condition that they are used lawfully. All files are the property of their respective owners.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.
E N D
Presentation Transcript
Course: B.Tech. Subject: Engineering Chemistry Unit: V (B)
DEFINITION: LUBRICANTS A lubricant is substance (often liquid) introduced between two moving surfaces to reduce the friction between them. Fluid which is introduced in between moving parts in order to reduce the friction, generated heat & wear and tear of machine parts are called Lubricants. This process of introducing lubricant is called Lubrication.
Gear and Transmission oils Automotive Oils Automotive Grease
COMPOSITION Typically oil(petroleum-mineral oils) and less than 10% additives contains 90% base Non liquid lubricants contains Grease, graphite, Teflon disulphite), plumbing etc. powder(dry Molybdenum tape used in Those non liquid lubricants provide lubrication at higher temp.(up to 350 C)
ADDITIVES USED IN LUBRICANTS (1)Anti oxidant ---Aromatic amines,Phenols,Sulphides and phosphates (2)Corrosion Inhibitor ---Amino salts andsalts of sulphonic acids (3)Antiwear agents --- Tricresyl phosphate (4) Foam inhibitors --- Glycerols
Functions of Lubricants It acts as a thermal barrier and reduces friction and wear and prevents welded joints Avoids seizure of moving surfaces Acts as coolant Acts as a seal and prevents entry of dust, moisture, & dirt between moving parts Some lubricants acts as corrosion inhibitors thus reduce operational cost .
A good lubricating oilshould have: High boiling point AdequateViscosity Low freezing point High oxidation resist Non Corrosive properties Good thermal stability 2
Types Of Lubrications Thick Film or Fluid Film or hydrodynamic Lubrication Thin Film or Boundary Lubrication Extreme Pressure Lubrication
This is also called Hydrodynamic or fluid film lubrication. Two sliding metal surfaces are separated from each other by a thick film of fluid ( 1000A thick). The coefficient of friction in such cases is as low as 0.001 to 0.03 Lubricants used : Hydrocarbon Oils. Provided in delicate instruments such as watches, clocks, light machines like sewing machines, scientific instruments etc. o
This lubrication is alsocalled Boundary Lubrication. Its used for high load conditions. Very thin film of the lubricant is adsorbed on the surface by physical or chemical forces or both. The coefficient of friction is 0.05to 0.15 Lubricants used forboundary lubrication should have highviscosity index, resistance to heat and oxidation, good oiliness. Examples are Organic oils, Vegetable oils, Graphite and MoS2, Mineral Oils etc.
This lubrication is for very high press/temp/speed sliding surfaces. Extreme pressure additives are used along with the lubricants. Chemicals used are compounds of Cl, S & P. These additives form solid surface films of Cl, S & P. High melting point metal compounds are good lubricants. E.g. graphite is used for drawing wires made up of mild steel. 3
Classification of Lubricants Liquid Lubricants Semi Solid Lubricants Synthetic Lubricants Solid Lubricants Eg.Mineral Oil, Petroleum Oil, Vegetable Oil etc Eg. Graphite, Molybdenum Disulphide etc. Eg. Petroleum jellies
TYPES OF LUBRICANTS Solid lubricants e.g Wax, Talc, Mica, Molibdenum disulphide Semi solid lubricants e.g. Grease and Vaseline Liquid Lubricants e.g. Mineral oils, Vegetable oils, Animal oils Synthetic lubricants e.g. Polyglycols, Silicones, Organic amines, Imines,Amides.
FEATURES OF LUBRICANTS Increase efficiency and reduce wear Dissolving or transporting foreign particles and distributing heat Single largest application is in form of Motor Oil, protecting internal combustion engines in motor vehicles and powered equipments Another approach is to use ball bearings, roller bearing or air bearings which in turn require internal lubrication themselves
Its a measure of a fluids resistance to flow. Viscosity of the lubricating oil determines its performance under operating conditions. A low viscosity oil is thin and flows easily. A high viscosity oil is thick and flowsslowly. As oil heats up it becomes more viscous (Becomes thin) Too low viscosity of the liquid > Lubricant film cannot be maintained between the moving surfaces > Excessive wear. Too high viscosity of the liquid > Excessive friction. Selected Lubricant must be proper viscous. Viscosity is usually expressed in centipoise or centistoke.
Iodine number is the number of Gms equivalent of iodine to amount of ICl absorbed by 100gm of oil. Each oil has its specific Iodine Number. So Iodine Number determines the extent of contamination of oil. Low Iodine Number is desirable in oils. Some oils and their Iodine Numbers are given below : Iodine Number >150 Oil Dryingoil Example Linseed oil, tungoil 100-150 <100 Semidryingoil Non-Dryingoil Castor oil , Soyabeanoil Coconut oil, Oliveoil
Aniline point is the Min temp at which oil is miscible with equal amt of aniline Aniline Point is a measure of aromatic content of the lubricatingoil. Low Aniline Point oil have high aromatic content which attacks rubber seals. Higher Aniline point means low %age of hydrocarbons(desirable). Thus Aniline Point is used as an indication of possible deterioration of rubber sealing etc. Determination of Aniline Point: Aniline+ sample oil (equal) Homogeneous solution Heated in Testtube Cooled Cloudiness The temperature at which separation of the two phases (Aniline + oil) takes place is the AnilinePoint.
Emulsification is the property of water to get mixed with water easily. Emulsions can be oil in water emulsion or water in oil emulsion. A good lubricating oil should form such an emulsion withwater which breaks easily. This property is called demulsification. The time in seconds in which a given volume of oil and water separates out in distinct layers is called steam demulsification number. A good lubricating oil should have lower demulsification number. Quicker the oil separates out from the emulsion formed, better is the lubricating oil. In cutting oils the higher the emulsification number, better the oil is. This is because the emulsion acts as a coolant as well as a lubricant.
Flash Point is the min temp at which the lubricant vaporizes that ignite fora moment when tiny flame is broughtnear. Fire Point is the Min temp at which the lubricant s vapours burn constantlyfor 5 seconds when tiny flame is broughtnear. If flash point < 140 F = Flammableliquids And if flash point > 140 F =Combustibleliquids. The flash and fire points are generally determined byusing Pensky-Marten s apparatus. Oil under examination is filled in the oil cup up to the mark and heated by the air bath by a burner. Stirrer is worked b/n tests at a rate of about 1 2 rev/sec. Heat is applied so as to raise the oil temp by about 5c/min. The temp at which distinct flash appeared in side the oilcup is recorded as flashpoint. The heating is continued to record the fire point. 4
Drop Point is the Temperatureat which grease passes from thesemi- solid to the liquid state. So, it determines the upper temp limit for the applicability of grease. Determination : Beaker isheated. Temperature is raised. Grease sample passes from asemi- solid to a fluidstate. Temp at which its first drop falls from the opening is recordedas drop-point. 5
Cloud Point is the temp at which the lubricant becomes cloudy or hazy when cooled. Pour Point is the temp at which the lubricant just ceases to flow when cooled. Both indicates suitability of lubricant in cold conditions and thus must be low.
Its the mgs of KOH required to saponify 1 gm of oil. Saponification is hydrolysis of an Easter with KOH to give alcohol and Na/K salt of acid.
USES Other uses are for cooking, biomedical applications on human(lubricants for artificial joints).
APPLICATIONS Automotive Industry-Engine oil,Automatic transmission fluid, Gearbox fluid, Break fluids. Tractor(One lubricant for all systems) Other motors(2 stroke engine oil) Industrial(Hydraulic oils, Air compressor oils, Gas Compressor oils, Gear oils Bearing and circulating system oils, Refrigerator compressor oils) Aviation Marine
REFERENCES www.motosport.com 1. www.umongo.co.za 2. http://www.vidyarthiplus.in/2012/01/engineering- chemistry1-lubricants.html# 3. www.aimil.com 4. www.machinerylubrication.com 5. Atextbook of Engineering Chemistry by Shashi chawla 6.
