Cochran Boiler: Definition, Parts or Construction, Working Principle, Advantages, Disadvantages, Application [Notes & PDF]

Cochran Boiler is a simple fire tube boiler with multiple fire tubes. It is a modification of a simple vertical boiler.

In the Cochran boiler, the heating surface is replaced with multiple fire tubes that’s why it is the modification of Simple Vertical Boiler. Cochran boiler has greater efficiency comparatively Simple vertical boiler.

Here we are going to study Definition, Parts or Construction, Working Principle, Advantages, Disadvantages, and Application in very detail.

At the end of every article, you can download PDF.

let’s start with the definition first,

Cochran Boiler Definition:

Cochran boiler is a fire tube boiler (Fire inside the boiler and water surrounding to them) in which coal or gases as a working fluid is used, for generating the steam and that steam further used for several purposes.

Now comes to the construction,

Cochran Boiler Parts or Construction:

Cochran Boiler consists of the following Parts or Construction:

  • Grate
  • Fire door
  • Ash Pit
  • Flue gases
  • Combustion Chamber
  • Smoke Box
  • Chimney
  • Water level Indicator
  • Man Hole
  • Pressure gauge
  • Safety Valve
  • Steam stop valve
  • anti Primimg Pipe
  • A blow of valve and more
Cochran Boiler

Let’s study one by one,


The grate is basically known as the door for placing the fuel.

Fire door:

The fire is provided through the fire door to start burning of fuel inside the boiler.

Ash Pit:

Here, ashes are accumulated under the fire.

The Ashpit is located below the grate.

Flue gases:

When the burning of fuel starts, it produces gas which is already heated and used for heating the water.

The gas is called as flue gases.

Combustion Chamber:

Here burning of fuel takes place. A huge amount of heat is there. This heat sends to the fire tube for heating the surrounded water.

Smoke Box:

The smokebox is basically used for storing and releasing the smokes to the chimney during the working process of the boiler.


When the gas is complete burns and it remains only smoke, the smoke further comes to the smokebox and Smokebox sens smoke to the chimney. Here smoke is released to the atmosphere.

Water level Indicator:

It is a measuring instrument. It measures the level of water and gives the detail of the water level.

Man Hole:

It is a very important side of the boiler. When things get damaged and not working, then a boiler specialist enters through the Man Hole and fixes the damaged parts.

Pressure gauge:

We use this instrument in several places. The works are to measure the pressure of the steam of the boiler.

Safety Valve:

It is to prevent an increase in steam pressure. When the pressure increases above design pressure, the valve opens and discharges the steam to the atmosphere and,

When this pressure falls just below the design pressure, the valve closes automatically. Usually, the valve is spring controlled.

Steam stop valve:

The steam stop valve regulates the supply of steam outside.

First, from the boiler, the steam generated comes to an anti priming pipe here some parts of water particles will be removed and it completely remains dry steam then further this steam is used for needed place.

Anti Primimg Pipe:

Anti priming pipe is provided in the boiler for extracting steam from the boiler is only dry saturated steam.

A blow of valve:

Water contains some impurities like mud, sand, and salt. Due to the heating of water, these impurities deposited to the ground that creates a problem and it has to be removed.

So the Blow-off-valve is used for removing these things.

After studying construction now let’s have an overview of how it works,

Cochran Boiler Working Principle:

Working of the Cochran boiler is from the grate the fuel gases or coal are used and that is inserted.

From the firing door, the fire is provided to start the burning of fuel.

The burning of fuel generates the hot flue gases and it comes to the combustion chamber. Here almost temperature is maximum.

Cochran Boiler

We know this is a fire tube boiler. In the tube, hot flue gases passing and water is surrounded.

So the hot flue gases are passing through tubes. The hotness of the fire tube starts heating the surrounded water. The water starts evaporating and at some point it becomes steam.

Now the steam comes at the top of the boiler.

With the use of an Anti priming pipe, the complete steam is extracted from the boiler and here the steam stop valve is placed which works is to transfer the steam to other laces such as the turbine and so on.

When the fuel is burned completely and it becomes ash it comes down to the ash pit and the smoke is released to the chimney and to the atmosphere.

Cochran Boiler Working Video:

Video Credit to keeeripulla

It has some advantages and disadvantages too:

Cochran Boiler Advantages:

The following advantages of Cochran Boiler are:

  • Coal or Oil type of fuel can be used.
  • It is a quick and easy installation.
  • Installation and Initial cost of Cochran boiler is a low comparatively another boiler.
  • It is a portable(Easily move) type boiler.
  • The minimum floor required.
  • It has a high volume to area ratio.

Cochran Boiler Disadvantages:

The following disadvantages of Cochran Boiler are:

  • Steam generation is low due to vertical design and it is major disadvantages.
  • The pressure range is also limited.
  • Maintenance is difficult.

Cochran Boiler Application:

The main application of Cochran Boiler is:

  • Cochran Boiler used in small power plants and some industries too.
  • Refining units.
  • Paper manufacturing plants.
  • Chemical processing divisions.

Cochran Boiler Specification:

The following Specification of Cochran Boiler are:

  • Efficiency is 75 percent.
  • Heating Surface area 120 sq meter.
  • Working pressure 7 bar and a maximum up to 15 bar.
  • Height and Shell diameter is 5.75 and 2.75 meter.

This is all about Cochran Boiler from my side.

Also, you can read related articles:

Locomotive boiler
Lancashire Boiler
Lamont Boiler
Babcock and Wilcox Boiler

References [External Links]:

Fire Tube boiler Overview

Download PDF here.

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Amardeep Kumar

Amardeep will share information related to Mechanical Engineering in this platform. He is the author, editor at

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