Fire Tube Boiler – Working Principle, Types of Fire Tube Boilers

The Fire tube boiler is intended for transmitting hot-gases using heat source as well as cycle. These gases flow through pipes with a water-filled drum. This procedure efficiently transmits the heat from the hot gas to the water, which efficiently produces steam.  The main features of fire tube boilers include a simple design, easy to operate as well as the low cost to purchase. These boilers are extremely flexible in producing the average to low degrees of force with the capacity as well as skilled to be arranged in different designs.

What is Fire Tube Boiler?

These are one of the most fundamental and old designed boilers. These boilers are very famous in the 18th century, and especially applicable for train engines. In this kind of boiler, combustion of heat, as well as gases, flows through the pipe enclosed by water. These boilers may be high-pressure or low-pressure boilers. The measurement of these boilers can be done always with their external diameter. Generally, these boilers are intended for pressures up toward a highest of 250 psi & around 750 horsepower

Fire Tube Boiler
Fire Tube Boiler

Construction and Working Principle of Fire Tube Boiler

The construction of a water tube boiler can be equipped with cylindrical shell, vertical, firebox in the base, space for water in the center segment, and space for steam in the higher segment. A fire-grate is located at the fire-box base as well as coal is fired-up on the firebox. For burnt coal, an ash pit is placed at the base of the grate for gathering the ash from the burnt coal, and sometimes it can be detached.

One or many cross-tubes are flanged to the space of water that is placed within the box to raise the outside area of heating for improving the water flow. A small chimney is associated with the pinnacle of the firebox for releasing the waste outlets at some larger height. The cleaning of the boiler can be done by the hand holes as well as manholes of the tubes & shell of the boiler.

Fire Tube Boiler Diagram
Fire Tube Boiler Diagram

These boilers include a water level indicator; a pressure gauge, steam stop tap security tap, & a manhole like mountings for providing security as well as simplicity of working. The 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.

The water nearby the cylindrical type firebox also gets heat through radiation as well as convection, therefore steam will be generated. The flow of water in the boiler will be based on the difference of density within water that is formed with the difference of temperature.

Types of Fire Tube Boiler

The different types of this boiler include the following.

1) Cornish Fire Tube Boiler

The first Cornish boiler was approved by an engineer namely “Trevithick a Cornish”. This kind of boiler includes a plane cylindrical shell, as well as a tiny flue pipe holding the heating system, flows through it.

Cornish Fire Tube Boiler
Cornish Fire Tube Boiler

2) Lancashire Fire Tube Boiler

The construction of the Lancashire boiler is related to Cornish boiler but as a substitute of one flue pipe, two flue pipes are utilized.

Lancashire Fire Tube Boiler
Lancashire Fire Tube Boiler

3) Locomotive Fire Tube Boiler

The locomotive boiler is an inactive boiler which is used in train engines. This type of boiler is capable while producing steam as well as it is solid. The design of the locomotive boiler is horizontal multi tubular. The main advantage of using this type of boiler is low cost for construction, installation and steam capacity is high.

Locomotive Fire Tube Boiler
Locomotive Fire Tube Boiler

4) Vertical Fire Tube Boiler

The vertical boiler is a simple boiler, and it comprises of a cylindrical shell enclosed a larger section of water and rest of section will be occupied with steam. It contains cross tubes and a furnace at the bottom of the boiler. The combustion gases after heating the water are allowed to escape into the atmosphere.

Vertical Fire Tube Boiler
Vertical Fire Tube Boiler

5) Cochran Fire Tube Boiler

The Cochran boiler is a vertical type multi-tubular boiler, and it includes several horizontal fire tubes. The heating system is one part of the construction and it is perfect.

Cochran Fire Tube Boiler
Cochran Fire Tube Boiler

6) Scotch Marine Fire Tube Boiler

The Scotch marine boiler is very popular boilers used for high vapor capacities at high forces. This type of boiler includes a huge number of tiny diameter tubes for providing the benefit of the high-heating region of the surface. The boilers are fired up internally and leave from the boiler using a chimney to the environment.

Scotch Marine Fire Tube Boiler
Scotch Marine Fire Tube Boiler

7) Immersion Fire Tube Boiler

The immersion type boiler is a single flow boiler that was expanded in the year 1940 by Sellers Engineering. It includes fire tube only, works as a boiler as well as the burning chamber. By several burners, needles inserting premixed air & normal gas below pressure. It maintains condensed thermal pressures and requires brick-work totally because of its construction

Difference between Fire Tube Boiler and Water Tube Boiler

The comparison between two boilers namely water tube as well as fire tube mainly includes working pressure, material type, the rate of steam production, the requirement of floor area,  efficiency, load handling variation, design, operator skills, the cost for maintenance are discussed below.

  • In fire tube, the flow of hot flue gases will be through pipes and enclosed with water whereas, in water tube, the flow of water will be through pipes and enclosed with hot flue gases.
  • The low-pressure range of fire tube is up to 20 bar whereas in water tube up to 250 bar.
  • The load fluctuations in the fire tube cannot be handled whereas, in a water tube, it can be handled easily.
  • This boiler occupies more floor area for output whereas, in a water tube boiler, it occupies less area.
  • Fire tubes are large and not easy for transporting whereas, in a water tube boiler, it is not an issue.
  • The efficiency of fire tubers are up t0 75% whereas in water tube boiler is up to 90%
  • The flow of direction in fire tube is not in an exact direction whereas, in water tube, it flows in an exact direction.
  • The size of the drum in fire tube is large as well as injury caused by burst is also large whereas in water tube if any water tube gets damage then we can replace it easily.
  • The design of the fire tube is simple, easy to upright, and maintenance price is low whereas in water tube, the design is complex, not easy to upright, and maintenance price is high.
  • For efficient operation, fire tubes require fewer experts whereas in water tubes require experts

Advantages and Disadvantages

The advantages of this boiler include the following.

  • Designing of this boiler is simple and less maintenance price.
  • It is applicable to small-scale industries
  • Fewer experts are enough for the operation
  • No pure water is necessary
  • Treatment of feed water is not very essential this boiler

The disadvantages of this boiler include the following.

  • The efficiency of this boiler is up to 75%
  • The variation of the load cannot
  • It occupies more floor area
  • The working pressure of this boiler is maximum 20 bar
  • The handling of load fluctuations is not easy.

Thus, this is all about fire tube boiler design and its types. The applications of this boiler mainly involve in marines, railways, plants, and industries. Here is a question for you, what are the differences between steam boiler, water tube boiler, and fire tube boiler?

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