Difference Between Fire Tube Boiler and Water Tube Boiler [Notes & PDF]

The main difference between fire tube and water tube boilers is, fire tube boilers are internally fired, and hot flue gases pass through the tube, and in the water tube boilers the hot flue gases do not pass through the tube, they surround the tube and water tube is externally fired boilers.

This is the most comprehensive guide on the comparison or differences Between Fire Tube Boilers and Water Tube Boilers.

In short: If you understand these differences you can easily score maximum on it whether it may be an exam or an Interview.

Let’s get started.


A Boiler is a closed vessel in which steams is generated (from water to steam) with the help of coal-burning or other fuel substances. It is used in thermal power plants for steam generation and further, the steam is used for rotating the turbine for the generation of electricity.

Coming to classification there are multiple types of boilers but mainly it has been classified into two types:

  1. Fire Tube Boiler and
  2. Water Tube Boiler

Fire Tube Boiler:

The fire-tube boiler is a boiler in which fire (hot flue gases) is inside the tube and water is surrounded by them.

We call this type of boiler is Fire-tube boiler because the hot flue gases are flowing inside the tube and water surrounds the tube.

There are various types of fire tube boilers and here is the following list:

Water Tube Boiler:

The Water-tube boiler is a boiler in which Water is inside the tube and fire (hot flue gases) is surrounded by them.

The water is flowing in the tube and hot flue gases surround the tube therefore we call this type of boiler is water tube boiler.

Here also there are various types of water tube boilers. Some of them are the following:

Differences between Fire Tube and Water Tube Boilers:

I have listed 17 points on the difference between Fire Tube and Water Tube boiler which are the following:

Sl No.Fire Tube BoilerWater Tube Boiler
1.The Hot flue gases flow inside the tube and water has surrounded the tube. Whereas In the water tube boiler, The water flow inside the tube, and the hot flue gases have surrounded the tube.
2.This is heavy in weight.This is light in weight.
3.This is also called an internal fire tube boiler andThis one is called an Externally Fire-tube boiler.
4.Here the pressure is limited to only 20 bar butIn the water tube boiler, the pressure is around 100 bar and more.
5.The rate of Steam generation is Lower. Why? because the pressure is limited to only 20 bar. The rate of Steam generation is High. Why? because the pressure is limited to 100 bar and more.
6.The explosion chances are less in a fire tube boiler because of low pressure.Here explosion chances are more because of high pressure.
7.The overall efficiency is around 75 percent.In the water tube, the overall efficiency is around 90 percent.
8.Efficiency is less compared to the water tube.Efficiency is more.
9. Load fluctuations cannot be handled. Load fluctuations can be handled easily.
10. The direction of water circulation is not well defined in this boiler.The direction of water circulation in a water tube boiler is well-defined.
A definite path is provided for the circulation of water.
11. This is not suitable for a large Power Plant. It is used in the process industry. But It is suitable for Large Power plants.
12.It is simple in design. It is complex in design.
13.A less skilled operator can work on this boiler.But here it requires a more skilled operator.
14.This is having a low maintenance cost.But the Water tube boiler has High maintenance costs.
15.Fire Tube Boiler example:
Cochran Boiler
Cornish Boiler
Locomotive Boiler
Velcon Boiler
Simple Vertical and
Scotch Marine Boiler.
Water Tube boiler example:
Benson Boiler
Lamont Boiler
Babcock and Wilcox Boiler
Lamont Boiler
Loeffler boiler and
Yarrow boiler.
16.A fire-tube boiler requires more floor area for a given output.The water-tube boiler requires less floor area for a given output.
17.The fire-tube boiler is bulky and difficult to transport. ButThese (Water Tube Boilers) are light in weight, hence transportation is not a problem.
Fire Tube Boiler vs Water Tube Boiler

Now we have studied 17 Points on Differences between them.

I guess these 17 points have enough data to understand the differences between them.

Let me know if you understand or not. with the use of the comment box below.

If you are reading these lines then I must be sure that you liked the articles. Thank you so much. Keep Visiting for other articles.

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Video (In Hindi):


Question and Answers:

Which is better fire tube boiler or a water tube boiler?

The answer is a water tube boiler, because of more efficiency.

What are a fire tube boiler and a water tube boiler?

Fire-tube boiler: In a fire tube boiler the flue gases pass inside the tube and water surrounded them but In a water tube boiler: The water passes inside the tube and flue gases surround them.

Why water tube boiler is more efficient than the fire tube boiler?

The production rate of steam generation is much higher than the water tube boiler.

What is a smoke tube?

The flue gases (from the combustion process) pass through the smoke tube.


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Er. Amrit Kumar

Amrit Kumar is a Mechanical Engineer and founder of Themechanicalengineering.com. I have done a Diploma and Engineering degree in Mechanical and writes content since 2016.

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