16 Difference Between Fire Tube Boiler And Water Tube Boiler (With Pictures)

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A fire-tube boiler is a type of boiler in which hot gases pass from a fire through one or many more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and ultimately creating steam.

These boilers include a water level indicator, a pressure gauge, steam stop security tap and a manhole like mountings for providing security as well as simplicity of working. Fuel burns on the grate of the firebox in the boiler and the resultant hot-flue gases are permitted to flow in the region of cross tubes.

Water-Tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam generating tubes. The working principle of water tube boiler is thermal siphoning (circulation of natural water). In smaller boilers, additional generating tubes are separate in the furnace, while larger utility boilers rely on the water-filled tubes that make up the walls of the furnace to generate steam.

The Difference

  1. Water-tube boiler is the boiler in which the water is present inside the tubes and fire or hot gases surrounds these fire tubes. On the other hand, Fire-tube boiler is the boiler in which the fire or hot gas is present inside the tubes and water surrounds these fire tubes.
  2. Operation of water-tube boiler requires skilled operators whereas less skilled operators are just sufficient for effective operation of the fire-tube boiler.
  3. Due to low water volume, the startup time for water-tube boiler is lesser and response to load changes is faster when compared to that of fire-tube boiler.
  4. Water-tube boilers are high pressure boilers and usually operate at pressure of about 165 bar. On the contrary, fire-tube boilers are low or medium pressure boilers, and usually operate at pressure of about 25 bar.
  5. In water-tube boilers the risk of explosion is higher due to high pressure whereas due to low pressure in fire-tube boiler the risk of explosion is low.
  6. In water-tube boiler, the rate of steam generation and quality of steam are better and suitable for power generation. On the other hand, the rate of steam generation and quality of steam are very low in fire-tube boiler, therefore, not suitable for power generation.
  7. In water-tube boiler, water circulates in a definite direction whereas in fire-tube boiler, water doesn’t circulate in a definite direction.
  8. A water-tube boiler is complex in design, difficult to install and has high maintenance cost. On the contrary, fire-tube boiler is simple in design, easy to install and has a low maintenance cost.
  9. In water-tube boiler, treatment of feed water is very crucial as small scale deposits inside the tubes can cause overheating and bursting. In contrast, the treatment of feed water is not very important, because overheating due to scale formation cannot burst the thick shell.
  10. The bursting of water-tube boiler does not result to any serious destruction to the whole boiler system. On the contrary, the bursting of fire-tube boiler has a high probability of resulting to a serious destruction to the entire boiler system.
  11. The overall efficiency of water-tube boiler is up to 90% with the economizer. On the other hand, the overall efficiency of fire-tube boiler is up to 75%.
  12. Water-tube boilers work on fluctuating loads all the time whereas fire-tube boiler can only work on fluctuating load for a shorter time.
  13. The most popular water-tube boiler brands include: Foster wheeler D-type boiler, Foster wheeler ESD type boiler, Babcock & Wilcox boiler etc. The most popular fire-tube boiler brands include: Cochran boiler, Lancashire boiler, scotch boiler etc.
  14.  Water tube boiler occupies a less floor area when compared to a fire-tube boiler that requires a large floor area.
  15. Water-tube boilers are lighter in weight and therefore transportation is also not tedious. Fire tube boilers on the contrary are heavy in weight and therefore they cause a lot of challenges to transport.
  16. Water-tube boilers are usually used in large power plants whereas fire-tube boilers are usually used in process industries such as sugar mills, textile, paper industries and so on.

Fire Tube boiler (Smoke Tube) Vs Water Tube Boiler

BASIS OF COMPARISON WATER TUBE BOILER FIRE TUBE BOILER
Description Water-tube boiler is the boiler in which the water is present inside the tubes and fire or hot gases surrounds these fire tubes. Fire-tube boiler is the boiler in which the fire or hot gas is present inside the tubes and water surrounds these fire tubes.  
Operation Skills Operation of water-tube boiler requires skilled operators.   Less skilled operators are just sufficient for effective operation of the fire-tube boiler.  
Startup Time & Response To Load Changes Due to low water volume, the startup time for water-tube boiler is lesser and response to load changes is faster when compared to that of fire-tube boiler.   The startup time for fire-tube boiler is more and response to load changes is lesser when compared to that of water-tube boiler.  
Operation Pressure They are high pressure boilers and usually operate at pressure of about 165 bar.   They are low or medium pressure boilers, and usually operate at pressure of about 25 bar.
Explosion Risk The risk of explosion is higher due to high pressure.   Due to low pressure in fire-tube boiler the risk of explosion is low.  
Suitability The rate of steam generation and quality of steam are better and suitable for power generation. The rate of steam generation and quality of steam are very low in fire-tube boiler, therefore, not suitable for power generation.  
Circulation Of Water Water circulates in a definite direction. Water doesn’t circulate in a definite direction.  
Design & Maintenance Cost A water-tube boiler is complex in design, difficult to install and has high maintenance cost. Fire-tube boiler is simple in design, easy to install and has a low maintenance cost.  
Treatment Of Feed Water Treatment of feed water is very crucial as small scale deposits inside the tubes can cause overheating and bursting.   The treatment of feed water is not very important, because overheating due to scale formation cannot burst the thick shell.
Impact Of Bursting The bursting of water-tube boiler does not result to any serious destruction to the whole boiler system. The bursting of fire-tube boiler has a high probability of resulting to a serious destruction to the entire boiler system.  
Boiler Efficiency The overall efficiency of water-tube boiler is up to 90% with the economizer.   The overall efficiency of fire-tube boiler is up to 75%.
Fluctuating Load Time Water-tube boilers work on fluctuating loads all the time.   Fire-tube boiler can only work on fluctuating loads for a shorter time.
Popular Brands The most popular water-tube boiler brands include: Foster wheeler D-type boiler, Foster wheeler ESD type boiler, Babcock & Wilcox boiler etc. The most popular fire-tube boiler brands include: Cochran boiler, Lancashire boiler, Scotch boiler etc.  
Floor Area Occupation Water tube boiler occupies a less floor area when compared to a fire-tube boiler that requires a relatively large floor area.   Fire tube boiler occupies a more floor area when compared to a water-tube boiler that requires a relatively small floor area.  
Weight & Transportation Challenge They are usually lighter in weight and therefore transportation is also not tedious.   They are usually heavy in weight and therefore they cause a lot of challenges to transport.
Usage They are usually used in large power plants. They are usually used in process industries such as sugar mills, textile, paper industries and so on.