Boilers have several uses including generating steam to drive turbines for electricity production, and to provide steam for heating, cooling and industrial processes. Boilers can be classified based on their orientation, water and gas flow design, furnace location, circulation method, pressure rating, mobility, and number of tubes. Common boiler types include fire tube boilers like Cochran and Lancashire where gases pass through tubes and water surrounds them, and water tube boilers like Babcock & Wilcox where water passes through tubes and gases surround them. Each boiler type has advantages like efficiency, capacity, and cost, but also limitations regarding pressure, size, and complexity.

1. BOILERS

2. BOILERS

3. BOILERS
Uses of Boilers
• To generate steam to drive turbines to generate electricity.
• Steam used for air conditioning systems.
• Steam used for driving steam engines.
• Steam used for boilers to run ships using super heated steam.
• Steam used for auto clave's, portable heat /hot water for buildings.

4. Classification of Boilers
Boilers can be classified as follows:
• According to geometric orientation of boiler:
• According to relative position of water and hot gases:
• According to location of furnace:
• According to method of water circulation:
• According to working pressure:
• According to mobility of boiler:
• According to number of tubes in the boiler:

5. According to geometric orientation of boiler
a) If the axis of boiler is horizontal then it is called horizontal
boiler. Example:- Lancashire boiler, Locomotive boiler.
b) If the axis of boiler is vertical then it is called vertical boiler.
Example:- Cochran boiler.
c) If the axis of boiler is inclined then it is called inclined boiler.

6. According to relative position of water and
hot gases
a) Fire tube boilers:- If the hot gases of combustion from the furnace
pass through the tubes and water is surrounding the tubes is
called fire tube boilers. Example:Cochran, Lancashire, Locomotive.
b) Water tube boiler:- If the water passes through the tubes and hot
gases surrounding the tubes is called water tube boiler.
Example:- Babcock and Wilcox boiler.

7. According to location of furnace
a) Externally fired boilers:- In this boiler the furnace is placed outside
the boiler shell. Generally water tube boilers are externally fired.
Example:- Babcock and Wilcox boiler.
b) Internally fired boilers:- In this boiler the furnace is placed inside
the boiler shell. Generally fire tube boilers are internally fired.
Example:- Lancashire, Cochran boiler.

8. According to method of water circulation
a) Natural circulation boilers:- In this boiler, water flow take place
naturally, by density difference of water. The flow of water and
steam are set up due to density difference resulting from
difference in temperature. Example:- Lancashire, Babcock and
Wilcox boiler.
b) Forced circulation boilers:- In this boiler, water flow takes place by
a pump.
Example:- Benson boiler, La- mont boiler, Velox
boiler.

9. According to working pressure
a) High pressure boiler:- The working pressure of this boiler is higher
than 25 bar.
Example:- Babcock and Wilcox boiler.
b) Medium pressure boiler:- The range of working pressure of this
boiler is between 10 bar to 25 bar.
Example:- Lancashire boiler, Locomotive boiler.
c) Low pressure boiler:- The range of working pressure is between
3.5 to 10 bar.
Example:- Cochran and Cornish boiler.

10. According to mobility of boiler
a) Stationary boiler:- This boiler cannot be moved easily from one
place to another place. This are used in power generation or
process heating in industries.
Example:- Lancashire, Babcock and Wilcox boiler.
b) Mobile boiler:- It is portable boiler and can be easily moved. This
is used in marine and locomotive.
Example:- Locomotive boiler.

11. According to numbers of tubes in the boiler
a) Single tube boiler:- This boiler having only one fire or water tube
for circulation of hot gases or water.
Example:- Cornish boiler.
b) Multi-tube boiler:- This boiler having two or more fire or water
tubes for the circulation of hot gases or water.
Example:- Locomotive, Cochran, Lancashire, Babcock and
Wilcox boiler.

12. Fire Tube Boiler

13. Water Tube Boiler

14. Comparison between Fire tube boiler and
Water tube boiler
Fire Tube Boiler
1)
Hot gases are inside the tube and water is
outside.
Water Tube Boiler
1)
Water is inside the tube and hot gases outside.
2)
Can work under as high pressure as more than
125 bar.
2)
Operating Pressure limited to 25 bar.
3)
Rate of steam generation is lower.
3)
Rate of steam generation is higher.
4)
Not suitable for large power plant.
4)
Suitable for large power plant.
5)
Chance of explosion is less due to low
pressure.
5)
Chance of explosion is higher due to high
pressure.
6)
Floor space requirement is more.
6)
Floor space requirement is less.
7)
Cost is less.
7)
Cost is more.
8)
Required less skill for efficient and economic
working.
8)
Required more skill and careful attention for
efficient and economic working.
9)
For producing process steam.
9)
For producing steam for power generation as
well as process heating.
10) There is no problem of scale deposition and
less problem of overheating and bursting.
10) Small deposition of scale will cause
overheating and bursting of the tubes.

15. COCHRAN BOILER
Cochran boiler is modification of simple vertical boiler.

16. Working of Cochran Boiler

17. Advantages of Cochran Boiler
• It is compact and portable boiler therefore minimum floor area is
required.
• Initial cost of boiler is less.
• It can be moved and set up readily in different locations.
• Quick and easy installation.
• Any type of fuel can be used.(coal or oil)

18. Disadvantages of Cochran Boiler
• Steam raising capacity is less due to vertical design.
• Water along with steam may enter the steam pipe under heavy
loads due to small steam space.
• Efficiency is poor in smaller size.

19. LANCASHIRE BOILER
Lancashire is one of the most commonly used stationary boiler.

20. Working of Lancashire Boiler

21. Advantages of Lancashire Boiler
• Due to three passes of flue gases, the heating surface area per unit
volume of boiler is large.
• The fluctuations in load can be easily met by this boiler due to large
reservoir.
• Easy operation, low maintenance costs, easy to clean and inspect.
• By use of economizer and super heater, maximum heat of flue gases
is utilized, so efficiency of boiler can be increased.

22. Disadvantages of Lancashire Boiler
• Maximum working pressure is limited to 16 bars.
• Due to brick work, more floor area is required.
• Response of pressure build up is less.
• The furnace is inside the tubes therefore the grate area is restricted.

23. BABCOCK AND WILCOX BOILER
This boiler is used in stationary and marine engine. This is exclusively
used when pressure above 10 bar and steam generating capacity
more than 7000 kg/hr. is required.

24. Working of Babcock and Wilcox Boiler

25. Advantages of Babcock and Wilcox Boiler
• The steam generation capacity of the boiler is very high, about 2000
to 40,000 kg/hr.
• Replacement of defective tubes is easy.
• The draught losses as compared to other boilers is minimum.
• It is used in power station for generation large quantity of steam.
• Boiler is required less space area compared to fire tube boilers, and
offers greater operational safety.