2. CONTENTS:-
Definition of boiler
Classification of boiler
Babcock & Wilcox boiler
Essentials of a good boiler
Boiler mounting and its accessories
Fans of boiler
3. Definition of Boiler:-
A Boiler is a closed vessel in which water or other suitable liquid is heated to
Generate steam or vapour .
The steam or vapour then exited and used for various purposes like heating
application ,Boiler based power generation or even for cooking and other purposes
Which could be domestic or industrial.
4. CLASSIFICATION OF BOILER:-
Boiler can be classified according to the followings
According to the Axis
• Horizontal boiler
• Vertical Boiler
• Inclined Boiler
According to the passage through tubes
• Fire Tube Boiler
• Water Tube Boiler
According to the Method of fabrication
• Packaged Boiler
• Shop assembled Boiler
According to the nature of fuel source used
• Gas fired
• Oil Fired
• Solid fuel fired Boiler
According to the working pressure
• Low pressure Boilers
• High pressure boiler
According to the nature of circulation
• Natural circulation Boiler
• Forced circulation Boiler
According to the method of firing
• Internal firing
• External firing
5. ACCORDING TO THE PASSAGE THROUGH TUBES
Fire tube Boiler:-
Hot gasses passes through the tubes that are surrounded by water.
Some fire tube boilers are
I. Horizontal return tubular
II. Locomotive fire box
III. Scotch marine
IV. Vertical tubular
Water tube Boiler :-
The water passes through the tubes and the hot gases produced by the combustion of fuel, flow outside.
These types of boilers are designated by the common following names
I. Babcock and wilcox boiler – straight but inclined tubes which connects the header.
II. Striling boiler-multi tubular boiler having bent tubes that connect drum to header.
.
6. Fire tube boiler
In fire tube boiler ,the hot gases are inside the tube and water surrounds the tubes.
Relatively small steam capacities(12000 kg /hr).
Low to medium steam Pressures(18 kg/cm2).
Operates with oil, gas or solid fuels.
Examples:-
Cochran boiler
Lancashire boiler
Locomotive boiler
7. Water tube boiler
In this boiler ,water is inside the tube and surrounded by hot gases.
Used for high demand steam requirements.
Its steam capacities(45000 to 120000 kg/hr).
Combustion efficiency enhanced by induced draught provision.
Examples:-
• Babcock and wilcox boiler.
• Stirling boiler.
8. Accordingto pressure
High pressure boiler:-
Boiler having steam pressure above 15 psi is considered as high pressure boiler
e.g.,
Babcock & Wilcox boiler
Lamont boiler
Bension boiler
Low pressure boiler:-
The boiler which designed to operate at 15 psi or below is considered as low pressure boiler.
e.g.
Lancashire boiler
Cochran boilers
9. Accordingto the methodof firing
Internally fired boilers
The furnace is provided inside the boiler shell and is completely surrounded by water cooled surface.
This method of firing is used in
• Lancashire boiler
• Locomotive boiler
• Scotch boiler
Externally fired boilers
The furnace is provided outside or under the boiler. It has an advantage that its furnace is simple to
Construct and can easily be enlarged.
This type of firing used in Babcock and Wilcox boiler.
10. BABCOCKANDWILCOXBOILER
It is a high pressure ,externally fired water tube boiler.
It consist of welded steel high pressure drum mounted at the top.
Drum is connected to the uptake header and down take header.
Water tubes are connected to the headers are inclined at 15 degree to the horizontals.
Furnace is arranged below the uptake header.
Salient aspects of Babcock &Wilcox boiler
Capability to cope with high peak loads which are generally needed in thermal power plant.
Draught loss is minimum.
Replacement of defective tubes can be made easily.
11. ESSENTIALSOF A GOODBOILER
Heat generation capability should be at
I. Required pressure
II. Required quality
III. Fast speed
IV. Minimum fuel consumption
Economic:
I. Low initial cost
II. Low installation cost
III. Low operating cost
IV. Low maintenance cost
Construction:
I. Light weight
II. Less amount of brick work
III. Occupy small floor area
Quick starting
Capable to meet fluctuating demand of steam supply
Easy availability of spare parts.
12. Boiler mounting and its accessories
Boilermountings:-
The necessary devices installed or mounted for the safety of boiler and its control are called boiler mounting.
For safety:-
Safety valves
Water level indicator
Fusible plug
Combined high steam and low water safety valve.
For control:-
Pressure gauge
Stop valve
Feed check valve
Blow off cock
Man hole and mud hole
13. Boiler accessories
The device which are installed for their efficient operation and smooth working are called boiler accessories.
Super heater:- it is a device which converts wet steam or saturated steam into dry steam.
Economizer:-it is heat exchanger used for heating the feed water before it enters the boiler.
Air preheater:-it is used to recover the heat from the boiler flue gas which increases the Thermal efficiency.
Water feeding devices:-used to supply water while the boiler is in operation.
Water heating devices:-used to heat the feed water before it is fed to the boiler.
14. Forced draft (FD) fan
FD fan takes the air present in the outside environment and directs it into the furnace/boiler. As a result a positive p
Created and that contributes to smooth completion of combustion process.
FD fans are fixed and close to the furnace.
The FD fan ensures that the volume of air that is in the system are consistently balanced. This balance is mandatory
balanced combustion.
15. Induced draft(ID) fan
The ID fans are usually curved in the backward direction . This particular design is necessary for fans that have to han
Levels of pressure.
There is an accumulation of hot flue gases in furnace and boilers . The ID fan operate in such a way that these gases g
Out from the system to the atmosphere.
These fans achieve that by generating negative pressure with in the system.
The boiler system’s outlet is the precise point where id fan present.
16. Primary air (PA) fan
The major objective of the PA fan is to ensure that the coal that has been pulverized is properly transported into
the furnace .
The PA fans operate to generate extreme pressure, which is needed to thrust the coal particles and air towards the f
These fans assist in separating the particles of fuel from one another and thus making sure that combustion gets co
devoid of any hindrances.
17. Secondaryair (SA)fan
The chief function of the SA fan is to support the PA fan.
Whenever the situation arises ,the secondary air fans bring about a rise in amount of air flow. Both prevents fuel wa
and enhance the overall efficiency of the combustion process.
Presence of SA fan makes certain that added air is promptly supplied to the system. With that ,there will not be any
In the combustion Process.
