lubrication

2. Lubrication:
It is the process or technique employed to reduce
the friction between the moving parts of a
machine.
Lubricants
The substances which is employed in the process
of lubrication .Eg: petroleum oil, animal or
vegetable oil .

3.  It act as coolant because it reduces the
production of heat between the moving parts
of the machine in contact.
 It avoid the damage of the moving parts of
machines by minimizing the production of
heat.
 It reduces the wear and tear of by keeping the
moving parts of machines apart.
 It reduces the maintenance and running cost
of machine.

4.  It increases the efficiency of machine by
reducing the loss of energy.
 It can also act as corrosion preventers.
 It act as a seal as in piston.

5. Three types of lubrication are :
 Hydrodynamic or Fluid film or Thick film
lubrication
 Boundary or Thin film lubrication
 Extreme pressure lubrication

6.  Also called complete or full flow.
 Occurs when two surfaces are completely
separated by a fluid film. { Thickness of fluid
film is at least 1000 Å } .
 In this method ,the lubricant fills the grooves
and forms a thick layer in between them so
that there is no direct contact between the
sliding surfaces.
 In this way ,the lubricant reduces the wear
and tear by reducing the frictional resistance
produced by movement of sliding parts.

8.  It is a semi-solid, consisting of a metallic
soap dispersed throughout a liquid
lubricating oil . The liquid lubricant maybe
petroleum oil or synthetic oil and it may
contain additives also.
 These are prepared by saponification of fat {
fatty acid, vegetable oils } with alkali [like
lime,caustic soda ] followed by adding hot
lubricating oil while under agitation.
 Sodium,calcium,lithium soaps are used as
gelling agents.

10.  To improve the heat resistance of grease ,
inorganic solid thickening gents like finely
divided clay,belonite,carbon black etc..

11.  They have high shear or frictional resistance
than oils ,can support much heavier loads at
lower speeds .
 Normally grease can sustain temperature
upto 180 degree.
 They have a tendency to separate into oils
and soaps.

12.  In situations where oil cannot remain in place
due to high load,low speed,sudden jerks etc..
I. FOR EXAMPLE :In rail axle boxes;
 In bearing and gears that work at high T
 In situations where bearing neeeds to be
sealed against entry of dust,dirt,moisture
because greases are less liable to
contamination by these.
 In situations where dripping of oil is
undesirable , because unlike oils,greases if
used do not splash over articles being
prepared by the machine.For
eg:paper,textile industrial machines.

13.  The main function of soap is thickening agent
so that grease sticks firmly to the metal
surface.
 Temperature upto which the grease can be
used.
 Its consistency.
 Its water and oxidation resistance.

14.  CALCIUM BASED GREASES:
 Emulsion of petroleum oils with calcium
soaps.
 Cheapest and most commonly used
 Insoluble in water.
 Used at low temperature ,because above 80°C
oil and soaps begin to separate.
 USED for :Tractors, lubricating water pumps.

15.  Thickened by mixing sodium soaps.
 Not a water resistant.Since it slightly soluble
in water.
 However , they can be used upto 175°C .
 Used in ball bearings.
 Dropping point is very high

16.  It is prepared by the saponification of vegetal
oils with lithium hydroxide.
 It is thickened by adding adding lithium
soaps.
 Water resistant
 Suitable to use at low temperature [15°C]
only.
 Used for lubricating engines.

18.  It is prepared by adding lime to resins and
fatty oils.Fillers like talc and mica are also
added to them.
 Water resistant.
 Very cheap resin-grease.
 Suitable for less delicate equipments working
under high load and low speed’

19.  Used where :
1) Operating conditions and load is too high
2) Where contamination of lubricating oil or
greases is unacceptable.
3) Combustible lubricants must be avoided
4) Operating condition are such that a
lubricating film cannot be secured by use of
oils or greases.