In this article we will discuss about:- 1. Introduction to Lubrication 2. Functions of Lubrication 3. Principles 4. Methods.
Introduction to Lubrication:
Lubrication is the process of making two surfaces smooth when they are in contact having relative motion with each other. This is done by introducing a substance called lubricant in order to reduce frictional forces. In fact lubrication reduces the power consumed by reducing the frictional force between two machine components having relative motion with each other.
It is a well-known fact that all machines or engines have an assembly of components and some of them are in motion and in contact with each other having relative actions. Frictional forces are generated which oppose the motion causing a loss of power, excessive wear of components and in due course failure of the components.
Due to the rubbing action of the components, there is an excessive production of heat. When the lubricating oil is poured in between the surface, it forms a fluid film which keeps the two parts separated from each other and reduces the amount of friction.
Functions of Lubrication:
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Following are the functions of lubrication:
(a) It reduces frictional forces between the moving components.
(b) It reduces the wear and tear of components.
(c) It increases the life of machine and engine components.
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(d) Lubricants act as coolant. The engine components are cooled by removing the heat produced due to friction (carbon metallic particle).
(e) It washes away all deposits formed due to wear between two surfaces and thus helps in cleaning the surface.
(f) It provides mechanical sealing between two parts.
(g) It reduces metallic noise in engine components.
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(h) It reduces corrosion of the components.
Principles of Lubrication:
When two machine components are in contact and they have relative motion with each other, even though the metal surface is made smooth by machining, there are always a lot of abrasion found (if magnifications are made 100 times) as shown in Fig 8.1.
If the machine components are loaded and lubricating oil is introduced into them, the load will try to force the lubricating oil layer out of the surface and this results in metal-to-metal contact. The clear understanding is based on the fact that when a shaft rotates in a bearing, it is lubricated by pouring lubricating oil. Due to some technical reason, some clearance is always provided between the two surfaces of shaft and bearing.
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When the shaft is at rest, as shown in Fig. 8.2(a), there is a metal-to-metal contact. When the shaft rotates, the lubricant tends to rise up the shaft into the bearing due to centrifugal actions. The lubricant occupies a slightly eccentric position in between two surfaces as shown in Fig. 8.2(b).
Methods of Lubrication:
In addition to the proper selection of lubricants for specific purpose, an effective method is also necessary for any machinery.
Following are the main methods of lubrication:
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(a) Manual lubrication
(b) Gravity feed lubrication
(c) Forced lubrication
(d) Splash method of lubrication
(a) Manual Lubrication:
Manual lubrication by oil can comes under this category. An oil can is shown in Fig. 8.3.
(b) Gravity Feed Lubrication:
In gravity feed, lubricants are supplied by gravity.
(c) Forced Lubrication:
In a forced lubrication, the lubricating oil is supplied at high pressure by an oil pump.
(d) Splash Method of Lubrication:
In the splash method of lubrication, the moving part of machine or engine components are immersed in oil bath which splashes the oil by rotating to the surface to be lubricated.