1. LUBRICATION
PURPOSE, METHODS AND SYSTEMS OF
LUBRICATION
When one surface moves across the other the irregularities cause a
resistance to movement called friction
Friction causes heat and the heat causes the metal to expand, wich in turn
increases the frictional force on the surfaces
Wear takes place when the high point on the mating surfaces come into
contact and break off. These minute particles act as cutting tools that grind
the mating surfaces and cause more heat, greater vibration, and additional
wear.
Basic function of lubrication
 Reduce friction
Sliding friction results from two
surfaces moving across each
other
Rolling friction is the result of the
roller on a stationary surface
 Reduce wear
 Helps dampen or absorb shock
 Reduce temperature rise
 Minimize corrosion
 seal out contaminations
 flush out contaminants
The golden rule of lubrication " good lubrication depends
on the right lubrication being available in the right quantity at the right time"

2. Basic principles governing the application of lubricants
 cleanliness is vital (lubricating equipment must be kept free
of dirt and other contaminants
 before changing lubricant the equipment should be cleaned
out
 an excess of lubricant especially grease will cause
excessive heat to build up and eventual breakdown of the
lubricant
 Lubricant filters should always be changed at the
recommended time
 Inadequate lubrication can often be identified by the
operating condition of a bearing
 Lubricants are potentially hazardous materials and should be
stored with regard to safety effect on the environment
basic methods of lubricants
1-Manual application
 Oil can for liquid lubricant
 Grease gun for grease
 Brush or spray gun for solid lubricant
2-Gravity (dripping) (drip-feed oiling)
Only for liquid lubricants
3- Splash and bath lubrication
The components requiring lubrication being partially immersed in
an oil sump so that they pick up oil as they rotate

3. 4- Pressure lubrication
When the operating speeds are high the equipment require a
pressurized system to ensure that an adequate supply of lubricant
can be determined
5- Automatic lubrication
The automatic lubricators are the single-point small reservoir units
that mount on the bearing in place of grease fitting and dispense
the correct amount of grease to bearings as needed
6- Centralized automatic lubrication systems
Basic types of lubricant
1. Liquid
2. Semi-solid or plastic
3. Solid
4. Gaseous
Source of lubricant
 Animal
 Vegetable
 Mineral

4. Criteria for measuring the properties of oils
 Viscosity (thickness of a fluid and is also described as
resistance to flow)
 Viscosity index (rate of change of viscosity with temperature)
 Flash point (temperature at which the vapor of lubricant will
ignite
 Fire point ( the temperature at the vapor will ignite)
 Pore point ( low temperature at which the lubricant becomes
so thick it ceases to flow)
 Oxidation resistance ( at increased temperature they tend to
absorb oxygen)
Criteria for measuring the properties of greases
 Hardness
 Dropping point (temperature at which grease will change to
liquid)
 Pumpability (a measure which grease will flow through a
system)
 Water resistance (determine whether or not grease will
dissolve in water
 Stability (determines the ability of grease to retain its
characteristics)

5. Types of liquid lubricants (oils)
 Circulating oils
 Gear oils (required to have high viscosity)
 Machine and engine oils (commonly used on plain bearing
and slides ways)
 Spindle oils (high quality oils used for sensitive equipment)
 Refrigeration oils (for refrigeration equipments)
 Steam cylinder oils
 Special purpose oils
 General purpose oils (multi viscosity or multi grad
specifications)
GREASES
Categories of greases
Calcium based
Sodium based
Barium based
Lithium based
Aluminum based
Complex
Mixed based
Mineral oils mixed with solids
Applications of greases
 Way and slides
 Plain bearing greases
 Rolling element bearing

6. Solid lubricants
Solid lubricant such as graphite and molybdenum
Additives
To improve lubricant properties
Types of additives
 Oxidation inhibitors (prevent the chemical breakdown)
 Detergents and dispersants (keep surfaces clean )
 Rust and corrosion inhibitors (prevent formation of rust)
 Pour point depressants (to ensure that the lubricant will
maintain its ability to flow at low temperature
 Viscosity index improvers (to reduce the effect of changes
temperature on viscosity
 Anti-foam agents (to break up the air bubbles that tends to
form )
 Anti-friction compounds ( to reduce the coefficient of friction
between the rubbing surfaces
 Anti-water agents ( reduce friction and water due to scoring
 Extreme pressure agents (help to cushion the shock
between gear teeth at high loads)

7. SELECTION OF LUBRICANT
The selection of lubricant is by the following factors
 Load
 Speed
 Temperature
 Environment
For light loads and high speed - use lubricant of low viscosity
For high loads and low speed - use lubricant of high viscosity