Cochran and Babcock & Wilcox boilers are two common types of industrial boilers. Cochran boilers are vertically oriented, internally fired fire tube boilers capable of generating up to 4000 kg of steam per hour. Babcock & Wilcox boilers are large horizontally oriented water tube boilers that can generate over 7000 kg of steam per hour and operate at pressures over 10 bar. Both have advantages like fuel flexibility but Cochran boilers have disadvantages of lower efficiency and capacity while Babcock & Wilcox boilers are more complex, expensive and require pure feedwater.

1. COCHRAN BOILER AND
BABCOCK & WILCOX
BOILER

2. WHAT IS A BOILER?
• A boiler is a device used to generate steam at a desired pressure and temperature
by transferring heat energy produced by burning fuel to water to change it to
steam.
• It is a combination of apparatus used for producing, furnishing or recovering heat
together with the apparatus for transferring the heat so made available to the fluid
being heated and vaporized.
APPLICATIONS OF BOILERS
• Power generation
• Heating
• Industrial process

3. COCHRAN BOILER
Some features of Cochran boiler:
1. Vertical
2. Multi-tubular
3. Internally fired
4. Natural circulation
5. Fire tube boiler
6. Up to maximum steam pressure of 15 bar
7. Maximum evaporative capacity of 4000 kg of steam per hour.

5. CONSTRUCTION
The boiler consists of cylindrical shell, hemispherical fire box, fire tubes and chimney.
The top of the shell has hemispherical shaped crown. The hemispherical crown of
boiler gives good strength to with stand pressure of steam inside the boiler. The
hemispherical shape of furnace can withstand high heat and is also useful to
increase radiant heat transfer from the furnace to hemispherical furnace wall. The
grate is placed at the bottom of the furnace and ash pit is located below the grate.
The furnace and the combustion chamber are connected by short flue pipe. The
wall of the combustion chamber is lined with the fire bricks. The ash pit is located
below the grate.

6. WORKING
The water is supplied to the boiler through feed check valve.
The coal is introduced to the grate through the fire door.
The hot gases produced from furnace enters combustion chamber through flue
pipe.
These hot gases enters into horizontal fire tubes.
Convection heat transfer take place from flue gases passing inside the tubes to
water surrounded the tubes.
The flue gases coming from fire tubes enter into smoke box.
Finally they discharge to atmosphere through a chimney.
The ash formed is collected in ash pit.
The steam is collected through anti-priming pipe on top of the shell.

7. ADVANTAGES AND DISADVANTAGES
OF COCHRAN BOILER
ADVANTAGES
• 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 location.
• Quick and easy installation.
• Any type of fuel can be used ( coal or oil).
DISADVANTAGES
• 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 sizes.
• Difficult in cleaning and inspection due to vertical design.
• The boiler requires high head room.

8. BABCOCK AND WILCOX BOILER
Some features of Babcock & Wilcox boiler:
1. Horizontal, Straight & Stationary
2. Externally fired
3. Natural circulation
4. Water tube boiler
5. Minimum steam pressure of 10 bar
6. Minimum evaporative capacity of 7000 kg of steam per hour.

10. CONSTRUCTION
• Boiler Shell: It consists of one or more steel plates bent into a cylindrical form and riveted or welded together. The shell and ends
are closed with the endplates.
• Uptake-header and Down Take Header: Boiler shell and water tubes are connected by the two tubes. Out of them, one is Up
Take header and the other is Down Take Header.
1. UpTake Header: The steam from the water tubes to the drum flow by means of UpTake Header.
2. Down Take Header: The water flows from the drum to the water tubes by means of down take header.
• Water Tubes: The angle of inclination of the water tubes to the horizontal is about 15 degrees. In this boiler, water will flow from
the drum by means of tubes only.
• Superheater: It increases the temperature of saturated steam.
• Grate: It is the platform in the furnace upon which fuel is burnt.
• Furnace: It is a chamber formed by the space above the grate and below the boiler shell in which combustion takes place.
• Baffles: The baffles are provided to deflect the hot flue gases so that the water tubes experience more amount of heat.
• Mud Box: All the impurities which are present in the boiler are deposited at the om and are stored in the mud box.
• Inspection doors: They are provided for cleaning and inspection of the boiler.
• Water space: It is the volume of a shell that is covered by water.
• Steam Space: The volume of shell except, the volume of water and tube space is called Steam space.
• Water Level Indicator: It is the indicator, which shows the level of water in the shell.

11. WORKING
● The entire boiler except for the furnace, are hung by means of metallic slings or straps or
wrought iron girders supported on pillars.
● This arrangement enables the drum and the tube to expand or contract freely.
● The angle of inclination of the water tubes to the horizontal is about 15 degrees. ● A feed valve
is provided to fill the drum and the inclined tubes with the water level of which is indicated by the
water level indicator.
● Through the fire door, the fuel is supplied to the fire grate and it is burnt. The hot gases are
forced to move upwards between the tubes by the baffle plates.
● The system consists of a Down Take Header(DTH) and UpTake Header(UTH) which consists of
holes in which a series of Inclined water tubes are fixed.
● The water from the drum flows through the inclined tubes via down-take header and goes back
into the shell in the form of steam and water mixture via UTH (Up Take Header).
● The steam is collected in the steam space of the drum.
● The steam enters through the APP(Anti-Priming Pipe) and flows in the ST(Superheater Tubes),
where it converts from Wet steam to Dry saturated steam and it is taken out from MSV(Main Stop
Valve) and feed to the turbine.
● At the lowest point of the boiler, the mud and dirt collect which is pumped out through Blow-
off Cock.

12. ADVANTAGES AND DISADVANTAGES
OF BABCOCK AND WILCOX BOILER
ADVANTAGES
• Generate Steam at high pressure and rate is high (140 bar and 40000kg/hr)
• For a given output, It occupies less space.
• Parts are accessible for cleaning, inspection, and repair
• Parts of the boiler can be separated and transported easily
• Due to the heating surface, Fuel is completely burnt.
DISADVANTAGES
• Pure feed water required
• Cost is high
• It requires more skill and careful attention

13. THANK YOU