In this article, you will learn about Locomotive Boiler Definition, Construction, Specifications, Working, Applications, Advantages and Disadvantages.
As its name suggests, the Locomotive Boiler is mainly employed in locomotives though it may be used as a stationary boiler. The good thing is that it is compact in construction and the rate of production of steam is high.
Definition of Locomotive Boiler
The Locomotive Boiler is a multi-tubular boiler which has a horizontal drum axis. The circulation in this boiler is natural and it is a medium pressure boiler. The draft of the boiler is artificial, mobile, forced circulation and solid fuel fired fire tube boiler. The locomotive boiler is an external fire boiler and it has a large fire space. It consists of a horizontal shell and this shell consists of a number of fire tubes.
Construction of Locomotive Boiler (Main Parts)
The following are the important parts of the Locomotive Boiler:
- Fire Hole: It is a hole provided at the rear end of the boiler from where the solid fuel is inserted and ignited into the furnace.
- Fire Box: The burning of fuel takes place inside this box.
- Grate: it is platform on which the solid fuel is kept and burnt. It is made up of a set of parallel bars at the bottom of the fire box.
- Fire Brick Arch: It is an arch of bricks placed inclined over the grate. It helps in preventing the entry of ash, dust and burnt fuel particles into the fire tubes. It provides the hot flue gases a way to travel a definite path before entering into the fire tubes.
- Boiler Tubes: The hot flue gases pass through these tubes and exchange heat with the surrounding water.
- Ash Pans: These are suspended beneath the fire-box for collecting and carrying the ashes. Sometimes coal may drop between the grate bars also gets collected in the ash pans. They are made up of sheet of steel.
- Draft: It is very important that the pressure in the smoke box is maintained at a value less than the atmospheric pressure. This difference in pressure between the smoke box and the atmosphere is called draft. The draft receives power for doing its work from the exhaust steam from the cylinders. Its world consists of drawing air through the ash pan, grates, fire door and other openings and continues its work by drawing the gases of combustion through the flues of the boiler into the front end.
- Diaphragm: It is an iron plate placed obliquely over some portion of the front end of the flues which deflects the flue gases downward before entering the stack. It can be adjusted to deflect gas more or less as desired.
- Stack: The stack is one of the most important features of the front end of the locomotive boiler. Various types and forms of stacks have been employed but at present, two general forms are found in use namely, the straight and tapered stacks.
- Smoke Box: It is a box in which the smoke of the burnt fuel gets collected after passing through the fire tubes. From there it is released in the atmosphere by the chimney.
- Blast Pipe: This pipe is provided above the steam engine; the exhaust steam passes through this pipe. It creates an artificial draft which pushes the smoke out through the chimney and creates suction for hot flue gases. This created suction helps the flue gases to move forward through the fire tubes.
- Steam Pipe: This is the pipe through which steam passes. There are two steam pipes, first the main steam pipe which is present between the super-heater header and the dome, second is that which connects the superheater exit end to the steam engine.
- Super-heater: The super-heater heats the steam to the desired temperature before entering into the cylinder of the steam engine. There are pipes of the super heater through which the steam travels and gets superheated, these are called super heater element pipes.
- Dome: It is preset at the top of the boiler and contains the regulator for regulating the steam produced through steam pipe.
- Regulator Valve: This valve regulates the steam through the main steam pipe for superheating.
- Safety Valve: This valve is used to maintain the safe working steam pressure in the locomotive boiler. It ensures the blowing off of steam when the steam pressure increases above safety level which prevents blasting of the boiler.
- Water Level Indicator: As its name suggests, it is used to indicate water level in the boiler and to maintain water at constant level because the production of steam majorly depends upon the quantity of water.
- Chimney: It is used to throw out exhaust smoke and gas in the atmosphere. In the locomotive boiler length of the chimney is short.
Approximate Specifications of the Locomotive Boiler
Below are the approximate specifications of the Locomotive Boiler, to provide you with a rough idea of the same:
- Barrel length: 5.2m
- Diameter: 2.1m
- Diameter of ordinary tube: 5.72m
- Diameter of super-heating tube:14m
- Number of ordinary tubes: 116
- Steam capacity: 9350kg/hr
- Coal burnt: 1750kg/hr
- Maximum pressure: 14.2 bar
- Efficiency: 70%
Working of Locomotive Boiler
The locomotive boiler consists of a smoke box at one end and a cylindrical barrel with a rectangular box at the other end. Coal is introduced through the fire hole in the grate which is placed at the bottom of the firebox.
The gases which are generated due to burning of the coal are deflected by the arch of fire bricks, so that the walls of the fire-box get heated properly. The firebox is completely surrounded by water excluding the fire hole and the ash pit that is located below the firebox which is fitted with dampers at its front and back ends.
The dampers governs the flow of air to the grate. Hot gases travel from the fire box to the smoke box through a series of fire tubes and through the chimney they escape into the atmosphere. These hot flue gases pass through long fire tubes and heat the water surrounding them. Due to this heating, water converts into saturated steam and gets collected at the top.
The saturated steam from the dome enters the main steam pipe through the regulator valve and travels in the main steam pipe and reaches the super heater header. From the header the saturated steam enters into the superheated element pipes. Here it gets superheated and then this superheated steam enters into the steam pipe of the smoke box.
The super-heated steam from the super-heater goes to the cylinder containing the piston where the steam makes the piston move within the cylinder. This piston is connected to the wheels of the steam engine which start rotating. The exhaust steam from the cylinder enters the blast pipe. The smoke and burnt gases after passing through the fire tubes enter into the smoke box. The exhaust which comes out of the blast pipes pushes the smoke out of the boiler through the chimney. In locomotive boiler the smoke cannot escape on its own, so an artificial draft is created by exhaust steam coming out of the steam engine. This artificial draft pushes the smoke out of the smokebox and creates suction for hot flue gases.
Applications of Locomotive Boiler
Locomotive boilers are mostly used in railways and marine operations. They are applied in traction engines, steam rollers, portable steam engines and other steam road vehicles. They are also employed in agricultural fields, saw mill plants and stationary power services.
Advantages of Locomotive Boiler
The advantages of the Locomotive Boiler are:
- It is a portable boiler and can be easily transported.
- It is capable of sudden and fluctuating demands of steam.
- Locomotive boiler is cost effective.
- Steam generation rate is high.
- It has a compact size and is easy in operating.
- Cost of construction and installation is low.
Disadvantages of Locomotive Boiler
Some of the disadvantages of the Locomotive Boiler are:
- It faces problems like corrosion and scale formation.
- It is unable to work under heavy load conditions because of overheating problems.
- some of the water spaces in the boiler are difficult to clean.
- This boiler needs bracing for large parts.
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