cochran boiler

Cochran Boiler-Construction, Working, Application, Disadvantages, PDF

Amrit Kumar Thermodynamics and Applied Thermodynamics 4 Comments

Are you looking for the Cochran Boiler? So today we will study the working principle, Diagram Application, and Advantages, Disadvantages of Cochran Boiler. Here you will get the articles of Mechanical Engineering in brief with some key points and you will get to know an enormous amount of knowledge from It. So If you find this articles helpful, please let us know in the comment box, either if any correction required too, also let us know in the comment box.

Cochran Boiler:

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

Cochran Boiler Construction or Main Parts:

The Main parts of Cochran boiler:

  1. Shell
  2. Grate
  3. Combustion chamber
  4. Fire tubes
  5. Fire hole
  6. Firebox (Furnace)
  7. Chimney
  8. Man Hole
  9. Flue pipe


  • The main body of the boiler is known as a shell.
  • It is hemispherical on the top, where space is provided for steam.
  • This hemispherical top gives a higher volume to area ratio which increases the steam capacity.


  • The area where the fire is placed known as a grate.
  • It is placed at the bottom of the furnace where coal is burnt.

Combustion Chamber:

  • It is lined with fire bricks on the side of the shell to prevent overheating of the boiler.
  • Hot gases enter the fire tubes from the flue pipe through the combustion chamber.
  • The combustion chamber is connected to the furnace.

Fire Tubes:

  • There are various fire tubes whose one end is connected to the furnace and other to the chimney.
  • A number of horizontal fire tubes are provided, thereby the heating surface is increased.
cochran boiler
Cochran boiler

Fire Hole:

  • The small hole is provided at the bottom of the combustion chamber to place fuel is known as a fire hole.

Fir Box(Furnace):

  • It works as a mediator of fire tubes and combustion chamber.
  • It is also dome-shaped like the shell so that the gases can be deflected back till they are passed out through the flue pipe to the combustion chamber.


  • It is provided for the exit of flue gases to the atmosphere from the smoke box.

Man Hole:

  • It is provided for the inspection and repair of the interior of the boiler shell.

Flue Pipe:

  • It is a short passage connecting the firebox with the combustion chamber.

Cochran Boiler Working:

  • The Cochran boiler works as same as other fire tube boiler example: Babcock and Wilcox boiler.

Step by Step:

  • First, The coal is placed at the grate through the fire hole.
  • Then the air is entering into the combustion chamber through the atmosphere and fuel is sparked through fire hole.
  • Then flue gases start flowing into the hemispherical dome-shaped combustion chamber. This flue gases further moves into the fire pipes. And then
  • Heat is exchanged from flue gases to the water into the fire tubes.
cochran boiler
Cochran boiler
  • The steam produce collected into the upper side of the shell and taken out by when the required pressure generated and then
  • The flue gases now send to the chimney through firebox where it leaves to the atmosphere.
  • Now, this process repeats and run continuously. The steam generates used into the small industrial processed.
  • Various boiler mounting and accessories are attached to the boiler for its efficient working:

1. Pressure Gauge: It measures the pressure of steam inside the boiler.

2. Safety Valve: It blows off the extra steam when the steam pressure inside the boiler reaches above safety level.

3. Water level Indicator: The position of the water level in the Cochran boiler is indicated by the water level indicator.

4. Stop Valve: Stop valve is used to transfer steam to the desired location when it is required. Otherwise, it stops the steam in the boiler.

5. Blow off Cock: It is used to blow off the settle down impurities, mud, and sediments present in the boiler water.

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Application of Cochran Boiler:

  1. Variety of process applications in industries
  2. Chemical processing divisions
  3. Pulp and Paper manufacturing plants
  4. Refining units

Besides, they are frequently employed in power generation plants where large quantities of steam (ranging up to 500 kg/s) having high pressures i.e. approximately 16 megapascals (160 bar) and high temperatures reaching up to 550 °C are generally required.

Features of Cochran boiler:

  1. In Cochran boiler, any type of fuel can be used.
  2. It is best suitable for small capacity requirements.
  3. It gives about 70% thermal efficiency with coal firing and about 75% thermal efficiency with oil firing.
  4. The ratio of grate area to the heating surface area varies from 10: 1 to 25: 1.

Cochran Boiler Advantages:

  1. Low floor area required.
  2. Low initialization cost.
  3. It is easy to operate.
  4. Transport from one place to another is very easy.
  5. It has a higher volume to area ratio.

Cochran Boiler Disadvantages:

  1. Low steam generation rate.
  2. Limited pressure handles capacity.
  3. It is difficult to inspect and maintain.

Cochran Boiler PDF:

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About the Author

Amrit Kumar


Amrit is a Co-founder of Learn Mechanical Portal (Previously owned ""). He completed his diploma in Mechanical Engineering from Acharya Polytechnic Bangalore and also completed his B-Tech from Delhi. Amrit is now preparing for Govt. exams. If you need help, you can ask him regarding any suggestions in the mechanical engineering field. He loves to meet new people.

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