Topics of Today
In the last session, we had discussed Lamont boiler, Benson boiler, Cochran boiler, Babcock and Wilcox boiler in a detailed way whereas, in today's session, we will discuss What is a Boiler? Selection of a boiler, Essentials of Good boiler, Classification of a boiler, Diagram of the boiler, Boiler Mountings, and Boiler Accessories in a detailed way.
The equipment used for producing steam is called Boiler or Steam Generator. Or it is also defined as “ A closed vessel in which steam is produced from water by the combustion of fuel.”
The steam generated is used for:
The working principle of the boiler is very simple. Let’s understand it with a real-life example. For bathing, especially in winter, you need to heat water so you should not feel coolness around you.
but have you seen that when the temperature of the water increases beyond its saturation state, it starts vaporizing? However, at home, you cannot collect the steam but in the industries, that steam is used to generate electricity.
Now lets under What the working Principle of boiler is?
The boiler is a closed vessel that stores the water in it. Apart from water, boiler mountings and boiler accessories are also present which increases the efficiency of the boiler which are explained below. The Fuel(coal) is generally used as a furnace to heat the water present in the boiler shell.
The hot gases from the furnace touch the surface of the boiler shell and thereby steam is generated inside the shell which on further operations can drive the turbine. The driving of the turbine leads to the generation of electricity which will be used for various purposes.
This is the working Principle of Boiler. Now, let’s classify the boilers…
The boilers may be classified as follows:
The explanation of the above types of boilers is as follows.
The parts of a horizontal boiler can be inspected and repaired easily. But, it occupies more space and the vertical boiler occupies less floor area.
For example, Babcock and Wilcox Boiler.
For example, Cochran, Lancashire boiler, etc.
For Example, Cochran, Lancashire boiler, etc.
For example, Babcock and Wilcox Boiler.
For example, Lamont Boiler, Benson Boiler, etc.
Ex: Lanarkshire, Babcock and Wilcox boiler.
High-Pressure Boilers:
The boilers which produce steam at pressures of 80 bar and above are called high-pressure boilers.
For example, Babcock and Wilcox, Lamont, Benson boilers.
Low-Pressure Boilers:
The boilers which produce steam at a pressure below 80 bar are called low-pressure boilers.
For example, Cochran, Lancashire, and locomotive boiler.
Stationary boilers are used for power plant steam for Central station utility power plants.
Portable Boilers:
Portable or mobile boilers include the locomotive type and other small units for temporary usage at sites(Just as in small coal-field pits).
For example, Cornish, Simple Vertical Boiler.
The selection of Boilers is based on below conditions:
These are some essential qualities for a good boiler:
The detailed explanation of Boiler Mountings and Accessories are presented below.
The Boiler Mountings are as follows:
The detailed explanation of Boiler Mountings are shown below.
It is fitted on the boiler so that we can come to know, how much water level was present in the bolier such that suitable steam can be generated from it.
The function of Blow off cock is to empty the boiler by removing water, mud and sediments which are collected at the bottom of the boiler shell.
The main function of Feed Check Valve is to regulate the supply of water which is pumped into the boiler by employing feed pump.
They are generally used to avoid the exposion takes place inside the boiler shell due to the excess pressure. When the pressure crosses the critical pressure, then the safety valve opens which allows excess steam to escape into the atmosphere untill the pressure inside the shell reaches normal pressure.
The Pressure gauge used in the boiler is especially of Bourdan type which is used to measure the pressure inside the boiler shell.
The fusible plug is placed at the top of the firebox whose duty is to avoid the explosion taking place due to the overheating of furnace when the water level in the boiler falls to an unsafe limit and it extinguish fire in the furnace.
The Boiler Accessories are presented below:
A detailed Explanation of Boiler Accessories are explained below.
A feed pump is one of the accessories of the boiler which is used to force the feed water into the boiler at high pressure. There are two types of Feed pumps,
This accessory of the boiler is used to separate the steam from the water in the boiler shell. If it is not taken, then an increase in furnace vaporizes the steam present in the boiler.
It is used to heat the feed water coming out from the boiler before it leaves the chimney to the atmosphere so that, the heat from the flue gases can be used as a preheat to other elements.
The usage of the Economizer increases the overall efficiency of the boiler.
It is placed or installed between the Economiser and Chimney and it has to supply preheated air into the furnace such that an increase in temperature takes place which accelerates the combustion of the fuel.
Thus by the usage of Air Preheater, the thermal efficiency of the plant will be increased.
The function of Superheater is to increase the temperature of the steam about the saturation temperature. It is also a device that is used to convert saturated steam into supersaturated steam.
This steam is used to drive the turbines and generate electricity.
| Criterion | Fire Tube | Water tube |
|---|---|---|
| Position of hot gases and water | Hot Gases in tubes surrounded by water outside | Water in tubes and Hot gases flow outside |
| Mode of firing | Internal fired | External fired |
| Floor area | For a given power, it occupies more floor area. | For a given power, it occupies less floor area. |
| Capacity | 10000kg.hr | 50000kg/hr |
| Evaporation | Slow | Fast |
| Operating Pressure range | 15 to 20 bar | 170 to 200 bar |
| Suitability | Not suitable for large power plants. | Suitable for large power plants. |
| Risk on burning | Involves Lesser risk of explosion due to lower Pressure | Involves more risk on bursting due to High Pressure |
| Application | Not suitable for large power plant | Suitable |
| Requirement of Skill | Requires Less skill for efficient and economic working | Requires more skill for efficient and economic working |
| Water Treatment | Not so necessary | More necessary. |
| Construction | Difficult | Simple |
| Shell Diameter | More | Less |
| Transportation | Difficult | Simple |
| Accessibility of various parts | Not easily accessible for cleaning, repairing and inspection. | Easily accessible |
This is the complete explanation of the Boiler. If you have any doubts feel free to ask in the comment section.
Boilers are classified based on
Horizontal, Vertical and Inclined Boilers
Single tube and Multitube boilers.
Externally Fired and Internally Fired
Stationary and Portable boilers
Fire-tube boiler and Water-tube boiler.
Natural circulation and Forced Circulation
High Pressure and Low-Pressure boilers
The equipment used for producing steam is called Boiler or Steam Generator. Or it is also defined as “ A closed vessel in which steam is produced from water by the combustion of fuel.”
The boiler accessories are Feed Pumps, Economizer, Superheater, Steam Separator, and Air Preheater.
The boiler mountings are Water Level Indicator Feed check valve, Pressure Gauge, Safety Valves, Fusible Plug, and Blow off cock.
More Resources:
Babcock and Wilcox Boiler
High-Pressure boilers
Cochran Boiler
Lamont boiler
Benson boiler
