10 Key Facts About Cochran Boiler Construction, Working, Advantages, and Disadvantages [PDF]

In this article, we will look into the Main Parts, Working principle, Applications, Advantages, and Disadvantages of the Cochran Boiler. We have also provided a PDF for the same.

What is Cochran Boiler?

Cochran Boiler 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. The efficiency of this boiler is much better than the simple vertical boiler.

Parts of Cochran Boiler

A Cochran Boiler consists of the following parts

  • Shell
  • Grate
  • Combustion Chamber
  • Fire tubes
  • Fire hole
  • Firebox (Furnace)
  • Chimney
  • Man Hole
  • Flue pipe
  • Fire Brick Lining
  • Feed Check Valve
  • Blow Off Valve
  • Ash Pit
  • Smoke Box Door
  • Anti Priming Pipe
  • Crown
  • Pressure Gauge
  • Safety Valve
  • Water Level Indicator
  • Water Level Gauge
  • Fusible Plug
  • Stop Valve
Cochran Boiler Diagram
Diagram of Cochran Boiler, Learn Mechanical


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.


In the grate section, solid fuel is stored, it is designed so well that air can easily flow through it, and also the ashes fall from the grate quite easily. In this section, the fire is placed.

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 the other to the chimney. Several horizontal fire tubes are provided to increase the heating surface.

Fire Hole

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

Fire Box (Furnace)

It works as a mediator of fire tubes and combustion chambers. 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 smokebox.

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.

Fire Brick Lining

It is a special type of brick lining used in Cochran boilers to reduce the convection of heat from the outer surface of the boiler. Fire Brick is generally made of fire clay.

Feed Check Valve

It is used to control the flow of water inside the boiler, it also helps to restrict the backflow of water.

Blow-Off Valve

It is used to blow off the settle-down impurities, mud, and sediments present in the boiler water.

Ash Pit

It is a chamber inside a boiler where ashes are stored.

Smoke Box Door

It is used to clean the smoke box deposits materials.

Anti-Priming Pipe

Sometimes water droplets come out with the steam, so to prevent these droplets from being carried out by steam the Anti Priming Pipe is employed.


It is a hemispherical dome-shaped section of a boiler, where the burning of fuel happens.

Pressure Gauge

It measures the pressure of steam inside the boiler.

Safety Valve

 It blows off the extra steam when the steam pressure inside the boiler reaches above safety level.

Water Level Indicator

The position of the water level in the Cochran boiler is indicated by the water level indicator.

Water Level Gauge

It is a glass tube fitted outside of the boiler to check the water level inside the boiler.

Fusible Plug

It is one type of safety measure. If the inside temperature of the boiler crosses the limit, then for safety purpose this Fusible Plug melts and the water comes into the boiler furnace and extinguish the fire.

Stop Valve

A stop valve is used to transfer steam to the desired location when it is required. Otherwise, it stops the steam in the boiler.

Working Principle of Cochran Boiler

The Cochran boiler works as same as other fire tube boilers. 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 a fire hole. Then flue gases start flowing into the hemispherical dome-shaped combustion chamber. This flue gas further moves into the fire pipes.

Heat is exchanged from flue gases to the water in these fire tubes. The steam produced is collected into the upper side of the shell and taken out by when the required pressure is generated. The flue gases now are sent to the chimney through a firebox where it leaves into the atmosphere. Now, this process repeats and runs continuously. The steam generated is used in small industrial processes.

Applications of Cochran Boiler

  • Steam for power generation: They are widely used in power plants to drive turbines by generating electricity from steam.
  • Industrial Operations: It is used in many industrial processes like chemicals manufacturing, textile production and food processing for heating, drying and sterilization procedures.
  • Heating Facilities: They are also used in large buildings such as schools, hotels and hospitals for space heating purpose
  • Steam locomotives: In the past, they were used to produce steam for engines for locomotives.
  • Marine applications: They are used in marine applications such as heating, ship propulsion and other on board procedures.
  • They are also useful in Agriculture, Food and beverage, healthcare facilities, Pharmaceuticals, paper industries, etc.

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

These are some features of the Cochran Boiler which are as follows

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

Advantages of Cochran Boiler

The advantages of Cochran Boiler are as following

  • Low floor area required.
  • Low initialization cost.
  • It is easy to operate.
  • Transport from one place to another is very easy.
  • It has a higher volume-to-area ratio.

Disadvantages of Cochran Boiler

There are some disadvantages of the Cochran Boiler which are as follows

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


So this is all about Cochran boiler, In conclusion, the Cochran boiler is a vertical, multi-tubular boiler that is widely used in different industries due to its simplicity and efficiency. It is easy to operate and maintain thanks to its construction and working principle, and it offers several benefits, including low fuel consumption and rapid steam production. Nevertheless, it also has some drawbacks, such as a limited heating surface area and the need for regular cleaning to prevent corrosion. Overall, the Cochran boiler is a dependable and cost-effective option for small to medium-sized applications that require a consistent steam supply.


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