In industry, mechanical equipment such as pumps, compressors, turbines, motors and any other type of machine having moving parts, need ‘LUBRICATION’ – to minimize friction and wear, to carry away heat from moving parts, to clean and to prevent rust.
Efficient operation of machinery largely depends not only on the lubricant selected but also on its method of application.
Lubricants formerly were applied by hand, but modern machinery requires exact methods that can be precisely controlled.
For most machinery, different methods of lubrication and types of lubricants must be employed for different parts. In an automobile, for example, the chassis is lubricated with grease, the manual transmission and rear-axle housings are filled with heavy oil, the automatic transmission is lubricated with special-grade light oil, wheel bearings are packed with grease that has a thickener composed of long fibers, and the crankcase oil that lubricates engine parts is lightweight, free-flowing oil.
Friction is the resistance of motion when one object rubs against another.
Anytime two objects rub against each other, they cause friction.
Friction works against the motion and acts in the opposite direction.
Friction generates heat and damage to moving parts.
A common way to reduce friction is by using a lubricant, such as oil, water, or grease.
Lubrication is the science of reduction of friction by using oils, greases or other special materials between the moving parts and the stationary parts of machines.
We are all familiar with the problems which can arise with our car if we allow the oil level in the sump to become too low or the oil too old and dirty.
Replacement of bearings, pistons and/or piston rings and cylinder liners etc, is very expensive and time consuming, not to mention the inconvenience caused by the car being off the road for a while.
The selection of the correct lubrication to be used in any machine is also very important. In industry, the science of lubrication is taken to a very high standard in order to protect the many hundreds of different types and sizes of modern machinery.
The important functions of lubricants are as follows:
- Keep moving parts apart
- Reduce friction
- Transfer heat
- Carry away contaminants & debris.
- Transmit power
- Protect against wear
- Prevent corrosion
- Seal for gasses
4.0. TYPES OF LUBRICANTS
There are three kinds of lubricants:
- solid lubricants
- semi-solid lubricants
- Liquid lubricants.
Solid Lubricants: Commonly used lubricants are graphite and soapstone. These lubricants are used when liquids or soft solids cannot be used and when the surfaces between which the lubricant will be placed are hard materials
Semi Solid Lubricants: Examples of semi solid lubricants are grease and Vaseline.
Liquid lubricants: Liquid lubricants are used in delicate and light machines which work at high speed but under low pressure.
Mineral oils, vegetable oils & animal oils are the various types of liquid lubricants.
Basics of Lube oil
Lube oil consists of a base fluid, generally of petroleum origin, combined with additive chemicals that improve various properties of the base oil.
Two main sources of base oil are: refining of petroleum crude oil (Mineral Oil) and “A product prepared by chemical reaction” called synthetic oil.
5.0. CHARACTERISTICS OF LUBE OILS
Viscosity describes a fluid’s internal resistance to flow and may be thought of as a measure of fluid friction .Viscosity is the most important property of any lubricating oil. Viscosity provides the proper thickness of the oil film at the operating temperature and conditions to keep the mating surfaces of the mating components apart during hydrodynamic lubrication conditions.
The power of an oil to maintain a continuous film under pressure while it is used as lubricants. A lubricant which doesn’t squeeze out from the sliding surface and maintain a continuous film is known as lubricant having high degree of oiliness.
Volatility of a lubricant is its tendency to vaporize with the increase of temperature. If the lubricant is highly volatile, it will vaporize readily even at low temperature. A good lubricant should have low volatility.
The minimum temperature at which a lubricant gives momentary flash of light when a flame is applied to it, but it does not continue to burn. Lubricant with higher flash point is most preferred.
The temperature at which a lubricant catches fire and burns continuously when flame is applied to it. Fire point of oil is always greater than its flash point.
It is the lowest temperature at which the oil eased to flow when cooled under prescribed conditions. If oil is used at a temperature below the pour point, the lubrication action will stop.
Emulsification: When oil is mixed with water or water is mixed with oil, emulsion is formed. A good lubricant is one which does not form emulsion and even if it forms, the emulsion should break quickly.