In this
article we will study about what is a boiler? Different types of boiler
(steam). The boilers are used in power plants for the generation of steam.
They are crucial for the working of a power plant. They are mostly used in the
power plants where steam turbines are used for the generation of electricity..
What is a Boiler?
A
boiler is a closed vessel which is used to convert the water into high pressure
steam. The high pressure steam so generated is used to generate power.
Working Principle of a Boiler
The boiler works on the same principle as the water is heated in a
closed vessel and due to heating, the water changes into steam. This steam possesses
high pressure kinetic energy.The boiler contains water. The water is heated to
its boiling temperature by the use of heat from the furnace. Due to heating of
water, it gets converted into high pressure steam. The steam generated is
passed through the steam turbines. As the high pressure steam strikes the
turbine, it rotates the turbine. A generator is attached to the turbine and the
generator also starts to rotate with the turbine and produces electricity.
Different Types of Boiler
Boilers
can be classified in different basis but here the important basis of boiler
classification are discussed.
1.
According to the Contents in the Tubes
According
to the contents in the tubes, the boilers can be classified as fire tube boiler and water tube
boiler.
(i) Fire Tube Boiler:
In
fire tube boiler the fire or hot gas are present inside the tubes and water
surrounds these fire tubes. Since fire is inside the tubes and hence it is
named as fire tube boiler. The heat from the hot gases is conducted through the
walls of the tube to the water. The examples of the fire tube boiler
are: simple vertical boiler, Cochran boiler, Lancashire boiler,
Cornish boiler, Locomotive boiler, Scotch marine boiler and
Velcon boiler.
(ii). Water Tube
Boiler:
In
water tube boilers, the water is present inside the tubes and the fire or hot
gases surrounds these water tubes.The examples of water tube boilers
are: La-Mont boiler, Benson boiler,
Stirling boiler, Babcock and Wilcox boiler,
Yarrow boiler and Loeffler boiler.
2.
According to the Number of Tubes
According
to the no of tubes, the boilers are classified as single tube boiler and
multitubular boilers.
(i). Single Tube Boilers: The boilers
which contain one fire tube or water tube are called as single tube boiler.The examples of single tube boilers
are Cornish boiler and simple vertical boiler.
(ii). Multitubular Boiler: The boilers
which has two or more water tube or fire tubes are called multi tubular
boilers.Lancashire boiler, Locomotive boiler,
Cochran boiler, Babcock and Wilcox boilers are multitubular boilers.
3.
According to the Position of the Furnace
According
to the position of the furnace, the steam boilers are classified as internally
fired boilers and externally fired boilers.
(i).
Internally Fired Boilers: The boilers
in which the furnace is located inside the boiler shell are called internally
fired boilers.Among all the fire tube boilers, most
of the boilers are internally fired boilers.
(ii).
Externally Fired Boilers: In externally
fired boilers, the furnace is located outside the boiler shell. In this the
furnace is arranged underneath in brick work setting.
§
Water tube boilers are always
externally fired boilers.
4.
According to the Axis of the Shell
According
to the axis of the shell, the boilers are classified as vertical boilers and
horizontal boilers.
(i).
Vertical Boilers: the in which the axis of the
shell is vertical are called vertical boilers.
§
Examples of vertical boilers are:
simple vertical boiler and Cochran boiler.
(ii). Horizontal Boilers: when the axis
of the shell in a boiler is found horizontal than it is called as horizontal
boiler.Lancashire boiler, Babcock and Wilcox boiler and locomotive boilers are
examples of horizontal boilers.
5.
According to the Methods of Circulation of Water and Steam
According
to the method of circulation of water and steam, the steam boilers are divided
into natural circulation boilers and forced circulation boilers.
(i).
Natural Circulation Boilers: In
natural circulation boilers, the circulation of water takes place naturally by
the convection currents that set ups during the heating of water.In most of the boilers there is a
natural circulation of water such as Lancashire boiler, Cochran boiler etc.
(ii).
Forced Circulation Boilers: In this type
of steam boilers, the water circulation takes place with the help of a
centrifugal pump driven by some external power. Here the circulation is forced
by some external agency.Forced circulation is used in high
pressure boilers such as La-Mont boiler, Loeffler boiler, Benson boiler etc.
6.
According to the use
According
to the use, the boilers are classified as stationary boilers and mobile boilers
(i).
Stationary Boilers: These are the boilers which are
stationary and cannot be moved from one place to another. Once they are
installed, cannot be transported to other destination.
§ These boilers are used in power
plants and in industrial process works.
(ii).
Mobile Boilers: these are the steam boilers
which can be moved from one place to another. Locomotive and marine boilers are
mobile boilers.
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