Simple Verticle Boiler is a boiler in which water is boiled inside a large vertical cylindrical shell and steam is produced. This is the simplest type of firetube boiler. This boiler produces low pressure and a small quantity of steam.
This boiler produces a pressure of nearly 10 bar. The construction of this boiler is very simple and easier than any other boiler.
This boiler occupies very little space, so it is used where less land is available for operation. The steam produces in this boiler is used in low working conditions like small power plants for producing current.
Parts of a Simple Vertical Boiler:-
1) Vertical Cylindrical Shell:-
This is the outermost cylindrical vertical shell of the boiler. Other parts of the boiler are inside this part. Most of the part of this cylindrical shell is filled with water and the rest part is for steam.
2) Cross Tubes
One or more cross tubes are riveted or flanged to increase the heating surface and to improve water circulations.
3) Furnace (or Firebox)
Furnace is used for the combustion of the coal. Coal is burnt here to produce heat.
It is present at the bottom of the furnace. It is the place in the furnace where coals are placed.
5) Fire Door or Fire Hole
Coal is inserted in the furnace through this hole or door.
It is available in the boiler to collect the ash deposited by the furnace.
7) Hand Holes
Hand Holes are present in the boiler opposite to the end of each cross tubes for cleaning the cross tubes.
A chimney is a vertical cylindrical pipe that extends from the top of the firebox to 1the top of the shell. It is used to pass the smoke from the boiler to the atmosphere.
Appart from these parts some mountings are present. These are :-
1) Steam Stop Valve
2) Safety Valve
3) Pressure Guage
4) Water Guage
5) Water Feed Valve
Construction of Simple Verticle Boiler
The biggest part of the simple vertical boiler is the vertical cylindrical shell. It is the outermost part of the simple vertical boiler, other boiler parts are contained inside this part.
Inside this shell, there is a firebox at the bottom of the shell. This firebox consists of a grate, furnace and ashpit. Grate is present at bottom of the firebox where fuel or coal is kept and burnt in the furnace. Ashpit is below the grate where ash created by burning fuel is collected. Coal is introduced to the firebox through a fire hole.
The cross tube is present at the center of boiler and is placed horizontally. This tube transfer heat from flue gas to water.
Above the cross tube chimney is present. Flue gases from the cross tube is passed to the chimney where it leaves the boiler and goes into the atmosphere.
Working Of Simple Vertical Boiler
- In the simple vertical boiler, at first the fuel is added through the fire hole into the furnace. Fuel is placed on the grate present at the bottom of the furnace. When the fuel burns hot gases are produced and the ash produced by burning of fuel is collected in the ashpit.
- The hot gases produced by burning of fuel are then going to the cross tubes and then the waste gases are passed out to the atmosphere through the chimney.
- Heat is transferred from flue gases in the cross tubes to the water and the water is heated to produce steam. Due to convection current water goes by natural circulation from the lower end of the cross tube to the higher end.
- The steam which is produced by heat transfer from flue gas to water is then collected at the steam space of the boiler, steam is collected until a certain pressure is reached and then the steam is passed out to the gas turbine or engine or for any other use.
Advantages of Simple Verticle Boiler
- Occupy very less space on ground as it has vertical cylindrical shell.
- Very low initial cost is required due to less parts.
- Maintenance cost is low.
- Easy to install and operate.
- This boiler has water level tolerance.
Disadvantages of Simple Vertical Boiler
- Water impurities settle down and prevent water from heating.
- Vertical design limit its working by many ways.
- Due to small-sized grate, steam production is low.
- Boiler tubes are kept short to minimize height. Since boiler tubes are short, very less time is for the flue gas to heat the tube and hence less steam is produced.