A locomotive boiler is a steel shell containing water which is converted into steam by the heat of the fire in the firebox to furnish energy to move the locomotive.
It is a horizontal, multi-tubular, internally fired, natural circulation boiler.
An artificial steam jet draught is present in this boiler for increasing the heat transfer rate which will see in detail in the working section of this article.
These boilers have enlarged back-end for the firebox. Also, this boiler has nearly 116 general fire tubes and 38 super-heated fire tubes. It used solid fuel like coal for its working.
Locomotive boiler is a portable boiler i.e it can be easily carried from one place to another.
This locomotive boiler can produce a high steam rate and is generally used in railway locomotive engines and in Submarines.
The first locomotive engine was constructed in 1803.
Parts of Locomotive Boiler:
1 Boiler Shell:
It is the outermost covering of the boiler. Other parts of the boiler is present inside this shell.
2 Super Heater:
This super heater is used to heat the steam to a very high desired temperature before entering into the steam engine.
3 Fire Tubes:
The hot gases will flow inside this fire tubes. These fire tubes are surrounded by water and exchange heat with the surrounding water.
4 Ashpit or Ashpan:
The ash of burnt fuel is collected in this ashpit. It is also known as ashpan. It is fitted beneath the grate.
The fuel is burnt by placing it over the grate. The grate is made up of cast iron. There is the spacing between the grate so that the air can pass through it and the fuel can burn easily.
6 Fire Brick Arch:
This brick arch is placed over the grate. The main function of this brick arch is to prevent ash, dust, and burnt fuel particles from entering into the fire tubes.
It also acts as a path for the flue gases before entering into the fire tubes.
When the fuel is burnt then the deflector is used to deflect the hot gases produced towards the fire tubes.
8 Fire Hole:
The fuel enters the boiler through this fire hole. The solid fuel generally coal is entered through this fire hole and is placed over the grate. This hole is provided at the rear end of the boiler.
9 Fire Box:
The fuel is burnt inside this firebox.
10 Smoke Box:
In the smoke, the smoke of the burnt fuel is collected after passing through the fire tubes.
11 Smoke Box Door:
The boiler can be cleaned through this smokebox door.
12 Blast Pipe:
This blast pipe is used to create an artificial draft that is used to push the smoke out through the chimney and create suction for the hot flue gases.
This suction created by the blast pipe also helps the flue gases to move inside the fire tubes.
This chimney of the locomotive boiler is small in size and an artificial blower is used to remove gases from the boiler. This chimney is used to remove the exhaust, smoke, and gases from the boiler.
14 Super Heater Header:
The super heater header is used to collect the saturated steam and covert this steam into superheated steam and this superheated steam is passed inside the firetubes through the superheater tubes which is placed inside the firetubes and has less diameter than the fire tubes.
15 Super Heater Tubes:
These super heater tubes are present inside the fire tubes are less in diameter than the fire tubes. The superheated steam produced using superheater passes through these superheater tubes.
16 Steam Dome:
This steam dome is used to collect the steam produced by the boiler. The steam regulator is present inside this steam dome.
This regulator is used to supply the steam when the operator pulls the lever. It regulates the steam through the main steam pipe for superheating.
18 Safety Valve:
The safety valve is used to blow off extra steam when the pressure in the boiler exceeds above safety level and prevents the boiler from blasting.
19 Blow Off Cock:
Blow Off Cock is used to remove or discharge mud and other sediments. It is also used to drain off boiler water.
20 Exhaust Steam Pipe:
The steam which escapes from the engine after working on it comes out from this exhaust steam pipe.
21 Water Level Indicator:
As the name suggests, it is used to indicate the level of water in the boiler.
22 Pressure Gauge:
It is used to indicate the pressure reading inside the boiler.
23 Man Hole:
Man Hole is a hole provided in the boiler for people to enter into the boiler. Anyone can enter inside the boiler through this man hole and change its parts if needed or can clean the boiler if required.
Working of Locomotive Boiler:
At first, the solid fuel (coal) is placed over the grate through the fire hole and is ignited from the fire hole.
As the fuel starts burning over the grate, hot gases come out from the burning fuel and these hot gases enter into the fire tubes. Now the gases will flow through the flue pipes and will heat these flue pipes.
A fire brick arch is present which provides a path and direction to the flue gases to reach the flue pipes and also prevents the solid fuel particles from entering into the fire tubes.
These flue pipes are surrounded by water and this water will start getting heated and these flue gases will come out from the chimney.
In this way, the flue gases will continuously heat the pipe and will escape the boiler through the chimney.
Due to heat received from the flue gases, the water will start getting heated and slowly it will start converting into steam.
This steam starts getting collected in the steam dome. Now, this saturated steam produced by heating water can be used directly or it can be superheated by directing it towards the superheater header.
Now the regulator regulates the saturated steam present in the steam dome and helps the saturated steam to enter into the main steam pipe.
The steam travels in the main steam pipe and reaches the superheater header. After the superheater, the superheated steam will be distributed in the superheater tubes and this superheated steam enters the steam pipe of the smokebox. This superheated steam is further used to run the steam engine and rotate the wheels of the rail.
The exhaust steam from the steam engine. The burnt gases and smoke reaches the smokebox after passing through the fire tubes. The exhaust steam which comes out from the blast pipe pushes the smoke and burnt gases present in the smokebox and moves them out of the boiler and through the chimney.
The smoke in the smokebox requires an artificial draft to come out of the chimney and this artificial draft is provided by steam coming out from the steam engine. Due to this artificial draft, the smoke pushes out of the smokebox, and suction is created for the flow of hot flue gases.
Advantages of Locomotive Boiler:
1) This boiler has a high steam generation rate.
2) It is very easy to operate.
3) It is compact in size and hence easily portable.
4) It is very cost-effective.
Disadvantages of Locomotive Boiler:
1) Some of its spaces are difficult to clean.
2) Corrosion formation is also one of its disadvantages.
3) It can not be used in heavy load conditions as overheating can occur in heavy load conditions.
Applications of Locomotive Boiler:
1) They are used in railways.
2) They are used in marines.
3) They are also used in traction engines.
4) They are also used in portable steam engines and some other steam road vehicles.
5) They are also used in steam rollers.