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Locomotive Boiler: Parts, Construction, Working, Advantages, and Applications

In this post, we will discuss what is Locomotive Boiler? And Its Definition, Parts, Working, Advantages, and Application of Locomotive Boiler.

Locomotive Boiler

Locomotive boiler is horizontal drum axis, artificial draft, natural circulation, multi-tubular, mobile, forced circulation, medium pressure, solid fuel fired fire tube boiler with the internally fired furnace.

It is used in marine engines and railway locomotive engines. It is a mobile boiler and has a high steam generation rate.

Locomotive Boiler diagram

Read also: Cochran Boiler: Parts, Working, Advantages, Mountings and More

Parts of Locomotive Boiler

The main construction parts of a locomotive boiler are as follows:

  1. Fire hole
  2. Firebox
  3. Grate
  4. Fire brick arch
  5. Boiler tubes
  6. Smokebox
  7. Blast pipe
  8. Steampipe
  9. Dome
  10. Superheater element pipe
  11. Superheater header
  12. Chimney

1. Fire hole

It is a hole provided at the air rear end of the boiler. The solid fuel is entered and burned into the furnace through this hole.

2. Firebox

The firebox is a type of box in which the burning of fuel takes place.

3. Grate

The grate is a platform on which the solid fuel is kept and burnt.

4. Fire brick arch

A fire brick arch is placed inclined over the grate. It prevents dust, ash, and burnt fuel particles from entering into the fire tubes. This arch provides a way for the hot exhaust gases to travel a definite path before entering the fire tubes of the boiler.

5. Boiler Tubes

They are the fire tubes through which the hot exhaust gases pass and exchange the heat with the surrounding water.

6. Smokebox

According to its name, it is a box in which the smoke of the burnt fuel after passing through the fire tubes gets collected. From there it is exhausted in the environment by the chimney.

7. Blast Pipe

It is pipe provided above the steam engine. The exhaust steam passes through this blast pipe. It is used to create the artificial draft that pushes the smoke out through the chimney and creates suction for the hot exhaust gases. The suction created allows the hot exhaust gases to move forward through the fire tubes.

8. Steampipe

It is the pipe through which the steam passes. We have two steam pipes, one in the main steam pipe present in between the superheater header and dome. And the second one is that which connects the superheater exit end to the steam engine.

9. Dome

It is present at the top and contains the regulator for regulating the steam produced through the steam pipe.

10. Superheater element pipes

These are the pipes of the superheater through which the steam travels and gets superheated.

11. Superheater header

It is the head of the superheater which accepts the steam from the steam pipe.

12. Chimney

It is used to throw out exhaust smoke and gases into the environment. The length of the chimney is very small in this boiler.

Boiler Mountings and Accessories of Locomotive Boiler

Locomotive boiler mountings and accessories are as follows:

  1. Water level indicator
  2. Pressure gauge
  3. Blow off valve
  4. Superheater
  5. Regulator Valve
  6. Safety Valve

1. Water Level Indicator

It is a device employed to show the water level in a boiler.

2. Pressure Gauge

The pressure gauge a device that determines the boiler pressure reading.

3. Blow-off valve

The purpose of the blow-off valve is to remove the mud and other sediments. It can also be applied for drain-off boiler water.

4. Superheater

It superheats the steam to the desired temperature before entering into the cylinder of the steam engine.

5. Regulator Valve

It is a valve that regulates the steam through the main steam pipe for superheating.

6. Safety Valve

It is used to maintain the safe working steam pressure in the locomotive boiler. It blows off steam when the pressure of the steam increases above safety level and prevents blasting oof the boiler.

Working of Locomotive Boiler

In a locomotive boiler, first, the solid fuel (coal) is inserted on the grate and is ignited from the fire hole. The burning of the fuel starts and it creates hot exhaust gases. A fire brick arch is provided that makes the flow of hot exhaust gases to a definite path before entering into the long tubes (fire tubes). It also prevents the entry of burnt solid fuel particles into the fire tubes.

The hot exhaust gases pass through the long fire tubes and heat the water surrounding them. Due to the heating, water gets transformed into saturated steam and collected at the top. Saturated steam from a dome enters into the steam pipe with the help of a regulator valve. The steam travels in the main steam pipe and reaches the superheater header. From the header, the steam enters into the superheater element pipes.

Here it is superheated and then the superheated steam enters into the steam pipe of the smokebox. The steam from the superheater goes to the cylinder containing the piston. The superheated steam made the piston moves within the cylinder. The piston is connected to the wheels of the steam engine and the wheels start rotating. The exhaust steam from the cylinder enters the blast pipe.

The burnt gases and smoke after passing through the fire tubes enter into the smokebox. The exhaust steam coming out from the blast pipe pushes the smoke out of the boiler through the chimney. Here the smoke cannot escape out from the boiler on its own, so an artificial draft is created by exhaust steam coming out from the steam engine. This artificial draft created pushes the smoke out of the smokebox and creates suction for the hot exhaust gases.

Advantages of Locomotive Boiler

  1. It is portable.
  2. This boiler is capable of meeting sudden and fluctuating demands of steam.
  3. It is a cost-effective boiler.
  4. High steam generation rate.
  5. It is compact in size and its operation is easy.

Disadvantages of Locomotive Boiler

  1. It faces the problems of corrosion and scale formation.
  2. Unable to work under heavy load conditions because of overheating problems.
  3. Some of its water space are difficult to clean.
  4. The overall efficiency is less.

Application of Locomotive Boiler

  1. Locomotive boilers are used in railways and marines.
  2. This type of boiler is used in traction engines.
  3. This is also used in steam rollers.
  4. It is can be used in portable steam engines and some other steam road vehicles.


What is the working principle of the Locomotive boiler?

As the fuel starts burning hot flue gases are produced. These hot flue gases are passed through pipes while the surrounding water is heated. Therefore, the water there changes the phase to saturated steam.

What is the application of the Locomotive boiler?

These types of boilers are employed in railways and marines. The locomotive boiler is used in traction engines.


That’s it, thanks for reading. So now, I hope that I have clear all your doubts about the parts and function of the locomotive boiler.

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About Saif M

Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at www.theengineerspost.com

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