smoke tube boiler

What is Smoke tube boiler? | Construction & Working of fire tube boiler |

In a smoke tube boiler the exhaust gas or flue gas flows inside the tube from the combustion chamber and heats up the surrounding water and turns it into steam.


In this boiler, a combustion chamber is placed which acts as a  source of heat energy for this boiler and is connected to the tube which provides a path for hot flue gasses or combustion gas to the exhaust funnel. The tube is placed in a tank with water surrounding it.

Working of smoke tube boiler:

When hot flue gasses or combustion gasses pass through the tube, heat exchange takes place between the tube and water. Since there is a large quantity of water, it will take time to heat all the water present there and slowly start to produce steam.

Mostly used on Bulk Carriers, Container Ships, and RO-RO Ships. This boiler is used wherever the pressure is needed among 6-7 bar. It is also known as SCOTCH MARINE BOILER.


  1. Simple in Construction.

2. Relatively Inexpensive.

3. Compact Sizes.


  1. Excessive time is required to raise steam.

2. Cannot generate high amounts of steam.

Difference between Water Tube Boiler and Smoke Tube Boiler

Water Tube BoilerSmoke Tube Boiler
Water circulated inside the tubes , and tubes are surrounded by hot flue gasses.Hot flue gasses circulated inside the tubes , and tubes are surrounded by water.
It can generate steam pressure up to 350 bar.It can generate steam pressure up to 25 bar.
Rate of steam generation is higher.Rate of steam generation is lower.
Suitable for large power plants.Suitable for small power plants.
For the same capacity floor space required less.For the same capacity more floor space is required.
Operating cost is high.Operating cost is less.
Overall efficiency is 90%.Overall efficiency is75%.
More problems of bursting and overheating.Less problem of bursting and overheating.


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