Page 301 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Air intake system: This system supplies necessary air to the engine for fuel combustion. It consists of pipes for
the supply of fresh air to the engine manifold. Filters are provided to remove dust particles from air which may act
as abrasive in the engine cylinder.
Exhaust system: This system leads the engine exhaust gas outside the building and discharges it into atmosphere.
A silencer is usually incorporated in the system to reduce the noise level.
Cooling system: The heat released by the burning of fuel in the engine cylinder is partially converted into work.
The remainder part of the heat passes through the cylinder walls, piston, rings etc. and may cause damage to the
system. In order to keep the temperature of the engine parts within the safe operating limits, cooling is provided.
The cooling system consists of a water source, pump and cooling towers. The pump circulates water through
cylinder and head jacket. The water takes away heat form the engine and itself becomes hot. The hot water is
cooled by cooling towers and is recirculated for cooling.
Lubricating system: This system minimises the wear of rubbing surfaces of the engine. It comprises of lubricating
oil tank, pump, filter and oil cooler. The lubricating oil is drawn from the lubricating oil tank by the pump and is
passed through filters to remove impurities. The clean lubricating oil is delivered to the points which require
lubrication. The oil coolers incorporated in the system keep the temperature of the oil low.
Engine starting system: This is an arrangement to rotate the engine initially, while starting, until firing starts and
the unit runs with its own power. Small sets are started manually by handles but for larger units, compressed air
is used for starting. In the latter case, air at high pressure is admitted to a few of the cylinders, making them to
act as reciprocating air motors to turn over the engine shaft. The fuel is admitted to the remaining cylinders which
makes the engine to start under its own power.

Nuclear power station: Generating station in which nuclear energy is converted into electrical energy is known
as a nuclear power station. In nuclear power station, heavy elements such as Uranium (U235) or Thorium (Th232)
are subjected to nuclear fission in a special apparatus known as a reactor. The heat energy thus released is
utilised in raising steam at high temperature and pressure. The steam runs the steam turbine which converts
steam energy into mechanical energy. The turbine drives the alternator which converts mechanical energy into
electrical energy. The most important feature of a nuclear power station is that huge amount of electrical energy
can be produced from a relatively small amount of nuclear fuel as compared to other conventional types of power
stations. It has been found that complete fission of 1 kg of Uranium (U235) can produce as much energy as can
be produced by the burning of 4,500 tons of high grade coal. Although the recovery of principal nuclear fuels (i.e.,
Uranium and Thorium) is difficult and expensive, yet the total energy content of the estimated world reserves of
these fuels are considerably higher than those of conventional fuels, viz., coal, oil and gas. At present, energy
crisis is gripping us and, therefore, nuclear energy can be successfully employed for producing low cost electrical
energy on a large scale to meet the growing commercial and industrial demands. (Fig 4)
Advantages
1 The amount of fuel required is quite small. Therefore, there is a considerable saving in the cost of fuel
transportation.
2 A nuclear power plant requires less space as compared to any other type of the same size.
3 It has low running charges as a small amount of fuel is used for producing bulk electrical energy.
4 This type of plant is very economical for producing bulk electric power.
5 It can be located near the load centres because it does not require large quantities of water and need not be
near coal mines. Therefore, the cost of primary distribution is reduced.
6 There are large deposits of nuclear fuels available all over the world. Therefore, such plants can ensure
continued supply of electrical energy for thousands of years.
7 It ensures reliability of operation.
Disadvantages
1 The fuel used is expensive and is difficult to recover.
2. The capital cost on a nuclear plant is very high as compared to other types of plants.

3 The erection and commissioning of the plant requires greater technical know-how.
4 The fission by-products are generally radioactive and may cause a dangerous amount of radioactive pollution.

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CITS : Power - Electrician & Wireman - Lesson 106-116