Locomotive Boiler – Construction Working and Application with Diagram

Locomotive boiler is a horizontal drum axis, multi-tubular, natural circulation, artificial draft, forced
circulation, mobile, medium pressure, solid fuel fired fire tube boiler with internally fired furnace. It
is used in railway locomotive engines and in marine. It is a mobile boiler and has high steam
generation rate.

Construction
The construction or main parts of a locomotive boiler are:

1. Fire hole: It is a hole provided at the rear end of the boiler. The solid fuel is inserted and ignited
into the furnace through this hole.
2. Fire box: It is a box in which the burning of the fuel takes place.

3. Grate: Grate is a platform on which the solid fuel is kept and burnt.

4. Fire brick arch: It is a brick arch placed inclined over the grate. It prevents the entry of the ash,
dust and burnt fuel particles into the fire tubes. It provides a way to the hot flue gases to travel a
definite path before entering into the fire tubes of the boiler.
 5. Boiler tubes: They are the fire tubes through which the hot flue gases passes and exchange the
heat with surrounding water.

6. Smoke box: 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 flue gases. The suction created allows the hot flue gases to move forward
through the fire tubes.

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

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

10. Super heater element pipes: These are the pipes of superheater through which the steam travels
and gets superheated.

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

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

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

14. Superheater header: It is the head of the superheater which accepts the steam form the steam
pipe.

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

Working
 In 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 flue gases. A fire brick arch is provided that
makes the flow of hot flue 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 flue gases passes through the long fire tubes and heats the water surrounding them. Due to
the heating the water gets converted into saturated steam and gets collected at the top.
 The saturated steam from the dome enters into the main steam pipe through the regulator valve.
The steam travels in the main steam pipe and reaches to the superheater header. Form header, the
steam enters into super heater element pipes. Here it is superheated and then the superheated
steam enters into the steam pipe of the smoke box.
 The steam form the superheater goes to the cylinder containing 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 into the blast pipe. The burnt gases and smoke after
passing through the fire tubes enters into the smoke box. The exhaust steam coming out from the
blast pipe pushes the smoke out of the boiler through the chimney. Here the smoke cannot escapes
out form the boiler by its own, so artificial draft is created by exhaust steam coming out from the
steam engine. This artificial draft created pushes the smoke out of the smoke box and creates
suction for the hot flue gases.

Advantages and Disadvantages

Advantages
 It is portable.
 It is capable of meeting sudden and fluctuating demands of steam.
 It is cost effective boiler.
 It has high steam generation rate.
 It is compact in size and its operation is easy.

Disadvantages
 It faces the problems of corrosion and scale formation.
 Unable to work under heavy load conditions because of overheating problems.
 Some of its water space are difficult to clean.

Application
Locomotive boilers are mostly used in railways and marines. The efficiency of this boiler is very
less. It cannot work in heavy load conditions because this leads to the overheating of the boiler and
finally gets damage. They are also used in traction engines, steam rollers, in portable steam engines
and some other steam road vehicles.

Locomotive Boiler – Construction,

Working and Application
A locomotive boiler is a device which is used to create steam from water by using heat
energy. It is a horizontal drum axis, multi-tubular, natural circulation, artificial draft,
forced circulation, mobile, medium pressure, solid fuel fired fire tube boiler that has an
internal fire furnace. It is capable of producing high steam rate and hence it is used for
railway locomotive engines and in marines.

Construction of locomotive boiler

1.Fire hole: This hole is used to insert solid fuel and ignite it in the furnace. It is located
at the rear end of a boiler.

2.Fire box: In this box, burning of fuel takes place.

3.Grate: It is the platform on which fuel is kept and ignited.

4.Firebrick arch: It is placed over the grate in an inclined position to stop the entry of
dust, ash, and burnt fuel particles into fire tubes. It allows the movement of fuel gases in
such a way that they move in a definite path before going into the fire tubes of the
boiler.

5.Boiler tubes: Through these tubes, hot flue gases pass and exchange the heat with
the surrounding.
6.Smokebox: The burnt fuel smoke, after passing through fire tubes, get collected in the
smoke box and then released into the environment through the chimney.

7.Blast pipe: It is located above the steam engine and exhaust steam is passed through
this pipe. It creates an artificial draft that pushes the smoke out through the chimney.
Also, it creates suction for hotter flue gases in order to move forward through the fire
tubed.

8.Steampipe: Steam is passed through the steam pipe. There are two types of steam
pipes; one is used between superheater and dome which is called as main steam pipe
and another is used between superheater end exit and steam engine.

9.Superheater: The steam is superheated with the help of superheater at the desired
temperature before entering into the steam engine cylinder.

10.Superheater element pipes: These pipes are present in the superheater through
which steam moves and gets superheated.

11.Dome: It is used to regulate the steam generated through the steam pipe. It is
located on the top.

12.Regulator valve: During the superheating process, this valve regulates the steam
through the main steam pipe.

13.Safety valve: For a safe working steam pressure this valve is used. When pressure
is more than the safety level, it blows off and prevents the boiler from blasting.

14.Superheater header: To accept the steam from the steam pipe, superheater header
is used.

15.Chimney: To send out the exhaust smoke and gases from the boiler, a chimney is
used which has a very small length.

The locomotive boiler works with the insertion of solid fuel on the grate and then igniting
it through the fire hole. As the fuel is burnt, it produces hot flue gases. These hot flue
gases are moved through a definite path by firebrick arch into the long fire tubes and
heat the water in the surrounding. As the heating continues, the water starts converting
into saturated steam which gets collected at the top.
Then, from the dome, this saturated steam gets into the main steam pipe via regulator
valve and reaches into the superheater header. The steam enters into the pipes of
superheater element to get superheated and then transferred to the steam pipe of
smoke box.

The steam from the superheater then enters into the cylinder which contains a piston.
With the pressure exerted by the steam, the piston is moved. The piston is connected to
the wheels of a locomotive, thus power is directly transferred to the wheels and they
start rotating.

The burnt gases and smoke are transferred to the smoke box through fire tubes and exhaust
steam from the cylinder is transferred to the blast pipe. The exhaust steam pushes out the
smoke from the boiler through the chimney, by coming out from the blast pipe. However, the
smoke doesn’t move out from the boiler on its own, therefore artificial draft is made by exhaust
steam that comes out of the steam engine. This artificial draft pushes the smoke out and
simultaneously creates suction for hot flue gases.

Advantages

 It can meet the fluctuating need of steam and can be ported easily.
 It provides high steam production rate.
 Its operation is easy and it is cost effective along with a compact size.

Disadvantages

 Over time, it gets corroded and scale is formed.

 Gets overheated when works under heavy load.
  Cleaning of some water spaces is not easy.

Application of locomotive boiler-

The locomotive boiler has low efficiency and cannot be used under heavy load because
of its overheating problem. They are commonly used in the railways and marines. In
addition, they can be used in a portable steam engine, steam rollers, traction engines,
and in other steam road vehicles.