What is Locomotive Boiler?
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 an internally fired furnace. It is used in railway locomotive engines and in marine. It is a mobile boiler and has a high steam generation rate.
A locomotive boiler has three main components: a double-walled firebox; a horizontal, cylindrical “boiler barrel” containing a large number of small flue tubes; and a smokebox with a chimney, for the exhaust gases.
The boiler barrel contains larger flue tubes to carry the superheater elements, where present. Forced draught is provided in the locomotive boiler by injecting exhausted steam back into the exhaust via a blast pipe in the smokebox.
Locomotive-type boilers are also used in traction engines, steam rollers, portable engines and some other steam road vehicles. The inherent strength of the boiler means it is used as the basis for the vehicle: all the other components, including the wheels, are mounted on brackets attached to the boiler.
It is rare to find superheaters designed into this type of boiler, and they are generally much smaller (and simpler) than railway locomotive types.
The locomotive-type boiler is also a characteristic of the overtype steam wagon, the steam-powered fore-runner of the truck. In this case, however, heavy girder frames make up the load-bearing chassis of the vehicle, and the boiler is attached to this.
Locomotive Boiler Parts
There are three main parts in this boiler including a horizontal cylindrical boiler baller, a smokebox, and a double-walled firebox. In this section, we will introduce the most important parts of this boiler to help you understand the Locomotive boiler diagram better.
- Grate: Just like any other horizontal boiler, Locomotive boiler has a grate that contains the fuel used for combustion.
- Fire Hole: This hole is at the rear end of this boiler which receives the solid fuel to be ignited into the furnace through the fire hole.
- Boiler Tubes: These tubes receive the hot flue gasses and as a result, they are able to transfer the heat to the surrounding water.
- Fire Box: The Fuel burns in the Firebox of the Locomotive boiler.
- Smoke Box: When the burnt fuel passes through the fire tubes, this box collects the smoke of this burnt fuel and transfers the smoke to the environment through the chimney.
- Chimney: The chimney receives the gasses and smokes from the smokebox to throw them out into the environment.
- Superheater: This unit is responsible to superheat the steam before it enters the steam engine’s cylinder.
- Fire Brick Arch: This arch is placed over the grate to stop dust, ash, and burnt fuel particles from getting into the fire tubes.
- Steam Pipe: As the name suggests, the steam passes through this pipe. There are two steam pipes in this boiler: one between the dome and the superheater header, which is the main steam pipe, and another one that is used for connecting the steam engine to the superheater exit end.
- Blast Pipe: This pipe sits above the steam engine and receives the exhaust steam. By creating an artificial draft, it transfers the smoke to the outside atmosphere through the chimney. Plus, by creating suction for the hot flue gasses, moves them forward through the fire tubes of the boiler.
- Dome: This boiler part regulates the steam that’s produced through the steam pipe.
- Regulator Valve: This unit is used for regulating the steam through the main steam pipe.
- Superheater Element Pipes: The steam flows through these pipes and gets superheated.
- Superheater Header: The steam that’s flowing through the steam pipe should go through the superheater header to be able to flow through the superheater element pipes.
- Safety Valve: When the pressure of the boiler increases and passes the pre-defined level, the safety valve blows off the steam to prevent the basting of the Locomotive boiler.
- Pressure Gauge: Shows the boiler pressure to help the safety valve.
- Water Level Indicator: This instrument enables the boiler to know the water level and do the necessary procedures to keep the water at the desired level.
- Ashpan: It’s a tray that’s under the grate to collect ashes.
- Man Hole: This unit has been designed for the experts to enter the boiler and repair or maintain the internal parts of the system.
How Does a Locomotive Boiler Work?
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
- It has high rate of evaporation somewhere 55 to 70 kg/Sec.
- Free from the brick boundary and external insulation that reduces the overall cost.
- It is portable, can be move from one place to other.
- Easy Operation.
Disadvantages of Locomotive Boiler
- Not suitable for high load due to overheating problem.
- Maximum steam pressure is limited to 20 bars.
- Leakage occurs at the joints that decreases the efficiency.
- Scale and corrosion formation occur.
Applications of Locomotive Boiler
- Locomotive boiler is mainly used in the railway to run the train engine. Efficiency of this steam engine is very less and limited so it no more used in the railway.
- It is also used in marine, traction engines, steam roller etc.
