Difference between water tube boiler and fire tube boiler


Difference between Water Tube Boiler and Fire Tube Boiler

In today’s article we are going to learn about the difference between water tube boiler and fire tube boiler. We know that boiler is used onboard for power generation and it is one of the most important thing on ship. Boiler is broadly categorized into water tube boiler and fire tube boiler. And since they are categorized differently this means that there must be some differences between them either in functioning, maintaining, running or economical differences. This article is all about their differences.

 Difference between water tube boiler and fire tube boiler

Difference between water tube boiler and fire tube boiler in a descriptive format :

Fire Tube Boiler

In fire tube boiler, as the name suggest Fire Tube (i.e Fire in Tube) the hot combustion gases ( flue gases) are passed through the tubes which are arranged inside the cylindrical drum and the outside of the tubes are surrounded by the water. The heat transfer takes place between the hot gases and the surrounded water through the tubes. This heats up the water and convert it into steam.
Fire Tube boilers are simple in construction as compared water tube boilers and are used as their alternative because of being cheaper. These are generally used in small scale industries as the operating pressure of fire tube boilers are low. Other advantages of fire tube boilers are that they have compact size and have the ability to handle the fluctuations in steam demand more efficiently.
There are also certain disadvantages of Fire tube boiler like it’s efficiency is low, it takes longer time to convert that amount of water into the steam, not able to cope up with sudden increase in load.

fire tube boiler

Water Tube Boiler

Now coming to the water tube boiler (i.e water in the tube), the water runs inside the tube and the hot gases are passed over the outer surface of the tube. The heat is transferred from the hot gases to the water in the tubes and it gets converted into steam. Since the steam is generated in the tubes , the water tube boilers can operate at higher pressure than the fire tube boilers and hence they are used in large scale production that requires high pressure and high steam output.


Water tube boilers are generally provided with more than one burner and we can use these burner either individually or in parallel combination for a single furnace. This provides a way to have controlled shutdowns so that maintenance can be carried out without shutting off the boiler entirely. Also the burners can be used to operate at different loads.
Water tube boilers are also provided with Programmable Logic Controller for controlling and maintaining proper functioning of the burners provided. They also control the super heater and feed water systems.
As the volume of area of production of steam is less in water tube boiler the water tube boilers are able to produce high pressure steam and at a faster rate than the fire tube boiler. They can also produce super heated or saturated steam according to the design and the place where they are required. They are able to operate at higher pressure.
The water tube boiler can be constructed to use high-ash fuels in conjunction with the soot blowers and proper Ash handling and flue gas cleanup equipment to maintain environmental regulations.


Though we have seen the various advantages of the water tube boiler but there are certain disadvantages also. The capital cost of water tube boiler is very high and the size of the water tube boiler is large as compared to fire tube boiler which bring it to a point that it is mostly constructed on the site where it has to be used.
Because of the use of control systems the complexity and it’s cost increases more. And for working on it a proper training is required.
Now that we have seen the descriptive difference between water tube boiler and fire tube boiler. Now it is more easy to remember in point form rather than the description, though the description gives you a better understanding of the differences.

water tube boiler

Difference between water tube boiler and fire tube boiler

Water Tube Boiler Fire Tube Boiler
1. The water flows inside the tube and the hot combustion gases flows outside the tube. 1. The hot gases flows inside the tube and the water is outside the tube.
2. These are generally high pressure boiler ranging up to 70-100 Bar. 2. These are generally low or medium pressure boiler up to 25 Bar.
3. Faster rate of steam Production. 3. Lower rate of steam Production.
4. More efficient 4. Less efficient
5. These boilers are mostly externally fired. 5. These are internally fired. The furnace is placed at one end of the Fire tube.
6. Suitable for large scale power plants. 6. Suitable for small scale power plants.
7. Since the operating pressure is high, the risk of explosion is also high. 7. Risk of explosion is less, as less operating pressure.
8. Occupies less floor space. 8. Occupies large floor space.
9. Because of complexity, skilled person is required to operate. 9. Less complex, less skill required.
10. Easy to clean as it is externally fired 10. Difficult to clean as internally fired.
11. The shell diameter is less. 11. The diameter of shell is more.
12. Easy to carry out maintenance. 12. Difficult to carry out maintenance
13. Since water flows inside the tube, treatment of water is necessary to prevent deposit formation. 13. Treatment of water is not necessary.
14. More environment friendly 14. Less environment friendly
15. Operating cost is high 15. Operating Cost is less.
16. Examples: Babcock and Wilcox Boiler, Stirling Boiler, La-mont Boiler, Benson Boiler, Loeffler Boiler, Yarrow Boiler 16. Examples: Simple Vertical Boiler, coachran boiler, Lancashire Boiler, Cornish Boiler, Scotch Boiler, Locomotive Boiler, Velcon Boiler.
fire tube gif
Fire tube Boiler