page contents

Cochran Boiler | Main Parts, Working, Features, Advantages & Limitations

Cochran Boiler

  • The Cochran boiler was founded by Cochran & Co. of Annan.
  • It is a vertical multi-tubular boiler and having a number of horizontal fire tubes.
  • It is the modification of simple vertical boiler where the heating surface has been increased by means of a number of fire tubes.
  • The efficiency of this boiler is much better than the simple vertical boiler.

Main Parts of Cochran Boiler

cochran boiler

Fig. Cochran Boiler line Diagram.

1. Shell

  • A shell is the main body of the boiler.
  • They having vertical axis cylindrical drum with hemispherical dome type shell at the top.
  • This hemisphere gives higher volume to increase steam capacity.

2. Grate

  • It is the platform on which the solid fuel is burnt.

3. Combustion chamber

  •  The burning of fuel takes place in the combustion chamber.

4. Fire tubes

  • The fire tubes helps in the exchange of heat from the hot flue gases to the water.

5. Fire hole

  • It is the hole through which fuel is fire inside the furnace.

6. Furnace (Fire box)

  • Furnace is the place where combustion of all the fuel is take place.
  • It lies at the bottom of the boiler.
  • It terms as fire box.

7. Ash pit

  • It is the place where ash of the burning fuel is collected.

8. Chimney

  • The chimney is attached with the smoke box .
  • And it releases smoke into the atmosphere.

9. Fire brick lining

  • It helps in the combustion of the fuel and present in combustion chamber.

10. Man hole

  • It is a hole on the boiler shell for the purpose of either cleaning, inspection and maintenance.

11. Flue pipe

  • It is a small passage which connected with the fire box and combustion chamber.
  • The hot gases enter into the combustion chamber through the flue pipe.

Working of Cochran boiler

  • Fuel is placed at the grate through fire hole.
  • Air comes into the combustion chamber through atmosphere.
  • Fuel is burn through fire hole.
  • Then, the hot flue gases emerge out and start flowing into hemispherical dome shaped combustion chamber.
  • This hot flue gases further moves into the fire pipes.
  • The hot flue gases inside the fire tubes exchange the heat from the hot gases to the water.
  • Due to the exchange of heat, the steam produced. And it rises upward to collect into the upper side of the shell.
  • When the required pressure generated, the flue gases goes to the chimney through fire box where it leaves to the atmosphere.
  • Hence, this process repeats and run continuously.


  • In Cochran boiler, any types of fuel may be used.
  • It gives 70% to 75% of thermal efficiency with coal and oil firing.
  • It is well suitable for small capacity requirement.
  • The ratio of grate area to the heating surface area varies from 10:1 to 20:1.

Specification of the Cochran boiler

  Height 5.75 m
  Efficiency 70 – 75 %
  Shell diameter 2.75 m
  Steam capacity 3500 kg/hr (max. 4000 kg/hr)
  Working pressure 6.5 bar( max. 15 bar)
  Heating surface area 120 m


  • It occupies less floor space.
  • Initial cost of boiler is less.
  • It is easy to operate.
  • Low initialization cost.
  • They having higher volume to area ratio.
  • Easy to clean and inspect.
  • It’s easy to transport from one place to another.


  • Maintenance and inspection are difficult due to narrow space inside for entering.
  • They having limited pressure range.
  • Steam generation rate is low.
  • Due to it’s vertical design, high room head is required for its installation.

Different types of Mounting used in Cochran boiler

  • The Mountings are those mechanical appliances which are considered essential for operating a boiler smoothly and safety. Which are usually mounted on the surface of a boiler.

The following are the important mountings of a boiler:

            1. Safety valves                                            2. Fusible plug

            3. Pressure gauge                                        4. Water level indicator

                 5. Blow off cock                                            6. Feed check valve

                 7. Steam stop valve

1. Safety valves

  • It is used to prevent explosion due to excessive internal pressure.
  • Safety valves are attached on the chest of the boiler.

Different types of Accessories used in Cochran boiler

1. Economizer

2. Feed pump

3. Super heater

4. Air preheater

15 thoughts on “Cochran Boiler | Main Parts, Working, Features, Advantages & Limitations

Leave a Reply

Your email address will not be published. Required fields are marked *