Lubrication of HSD Power Plant

LUBRICATION 

Frictional forces causes wear and tear of rubbing parts of the engine and thereby the life of the engine is reduced. This requires that some substance should be introduced between the rubbing surfaces in order to decrease the frictional force between them. Such substance is called lubricant. The lubricant forms a thin film between the rubbing surfaces and prevents metal to metal contact. The various parts of an I.C. engine requiring lubrication are cylinder walls and pistons, big end bearing and crank pins small end bearing and gudgeon pins, main bearing cams and bearing valve tappet and guides and timing gears etc. The functions of a lubricant are as follows

• It reduces wear and tear of various moving parts by minimizing the force of friction and ensures smooth running of parts. 

• It helps the piston ring to seal the gases in the cylinder. 

• It removes the heat generated due to friction and keeps the parts cool. 

 

The various lubricants used in engines are of three types: 

1. Liquid Lubricants. 

2. Solid Lubricants. 

3. Semi-solid Lubricants. 

Liquid oils lubricants are most commonly used. Liquid lubricants are of two types: 

(a) Mineral Oils 

(b) Fatty oils. 

Graphite, while lead and mica are the solid lubricants. Semi solid lubricants or greases as they are often called are made from mineral oils and fatty oils. 

A Rood lubricant should possess the following properties: 

• It should not change its state with change in temperature. 

• It should maintain continuous films between the rubbing surfaces. 

• It should have high specific heat so that it can remove maximum amount of heat. 

• It should be free from corrosive acids. 

The lubricant should be purified before it enters the engine. It should be free from dust, moisture, metallic chips, etc. The lubricating oil consumed is nearly 1% of fuel consumption. The lubricating oil gets heated because of friction of moving parts and should be cooled before recirculation. The cooling water used in the engine may be used for cooling the lubricant. Nearly 2.5% of heat of fuel is dissipated as heat which is removed by the Lubrication oil. 

Lubricating oil is purified by following four methods: 

1. Settling, 

2. Centrifuging, 

3. Filtering,

4. Chemical reclaiming. 

The centrifuging widely used gives excellent purification when properly done. 

The figure shows the lubricating oil external circuit.