Working Principle of Boiler


A boiler is a closed vessel system that is typically used to produce hot water or steam. There are basically two types of boilers available in the market, namely hot water boilers and steam boilers. A hot water boiler is typically used to produce hot water for domestic and commercial purposes, whereas the steam boiler is used to generate steam. A steam boiler is usually used for industrial applications such as to generate the driving force required for the movement of the wings of a motor or a turbine, to heat or melt elements, etc. The combustion of fuels is generally used as the source of energy to power the boilers. The advantages of using a boiler for various commercial and domestic applications include high efficiency, low emission of toxic gases, even distribution of heat, etc. Boilers can be used to perform various operations such as cleaning, cooling, heating, sanitization, etc. Some of the boilers available in the market are also used for humidification purposes and to generate power.  A boiler serves to be one of the most important and critical parts of a thermal power plant. Boilers are generally used in railway engines, ships, power plants, hotels, offices, buildings, greenhouses, and various other applications. Various factories and industries such as food and beverage companies, pharmaceutical firms, textile plants, paper mills, metal industries, sugar mills, etc. make use of boilers to carry out various operations. One of the prime applications of boilers can also be seen in the health care and medicine department. There are a variety of boilers are available in the market that can be broadly categorized on the basis of the type of application, the portability requirement, arrangement of the water circulation, position, output pressure value, and the type of input fuel used.

Working Principle of Boiler

The working of a boiler typically depends on the principle of conversion of energy from one form to the other and the conversion of matter from one state to the other. Initially, when the water is poured into the chamber or into the boiler’s closed vessel, it is externally supplied with heat energy. Due to the heat energy applied to the boiler, the conversion of energy from one form to the other can be observed easily. The heat energy supplied to the boiler chamber by the combustion of fuel tends to heat up the surface of the boiler and further gets coupled to the water present inside the chamber. This causes the water molecules to vibrate at a relatively high speed, thereby demonstrating the conversion of heat energy into kinetic energy. The rise in temperature increases the velocity with which the water molecules vibrate. This helps the water present in the vessel to boil after crossing a certain temperature value. On further heating of the water, the production of steam takes place and the conversion of water from the liquid state to the gaseous state can be observed very easily.

Parts of Boiler

On the basis of the type of operation performed, the parts of a boiler can be broadly classified into two categories, namely boiler mounting parts and boiler accessories.

1. Boiler Mounting Parts

The parts of the boiler that fall under the boiler mounting category are responsible to define the overall performance of the boiler. Various mounting components of a boiler include a pressure gauge, water level indicator, stop valve, safety valve, grate, blow-off cock, and feed check valve. The working of each of the boiler mounting components is given below:

1. Grate

The grate is nothing but the portion of the furnace where the combustion of the fuel takes place.

2. Pressure Gauge

A pressure gauge used by the boilers is typically fitted at the boiler’s front portion and is used to measure the pressure value inside the boiler chamber.

3. Safety Valve

As the name itself suggests, a safety valve is used by the boilers to ensure the safe operation of the instrument. Due to the continuous generation of steam inside the boiler chamber, the pressure value keeps on increasing. This increase in pressure inside the chamber increases the chances of boiler explosion. To avoid this, a safety valve is typically fitted on the drum walls that continuously monitors the pressure value and tends to blow off in case the internal pressure of the boiler increases and surpasses a certain threshold value. Generally, two or more safety valves are used and attached inside the boiler to ensure complete security.

4. Stop Valve

A stop valve is generally used by the boilers to control the flow of liquid or steam from the chamber to the outlet pipe.

5. Feed Check Valve

The feed check valve is typically used as a non-return valve. It is usually immersed into the water contained by the boiler and is required to be fitted on the drum surface. The main purpose of the feed check valve is to monitor and regulate the water supply.

6. Blow Off Cock

The blow-off cock is placed at the base of the boiler drum and is used as a mechanism to empty the boiler by blowing off the water and other particles present in the chamber.

2. Boiler Accessories

The parts of the boiler that are used to estimate the efficiency of the boiler fall under the category of boiler accessories. Some of the main boiler accessories include a superheater, feed pump, economizer, air preheater, etc.

1. Air Preheater

An air preheater is used by the boiler to heat the air of the chamber in advance to improve the generation of the steam and enhance the operation or overall efficiency of the boiler

2. Super Heater

The main purpose of the superheater is to heat the steam up to a significantly high level before passing over to the turbine. This helps improve the efficiency and functioning of the boiler as the saturated steam is susceptible to cause corrosion of the elements.

3. Feed Pump

The feed pump is used to continuously feed water to the boiler drum. This helps in the uninterrupted and continuous operation of the device, thereby increasing the overall efficiency of the boiler.

4. Economizer

The economizer mainly helps to filter the gases before they are released into the environment. This resists the boiler to emit toxic pollutants or contaminants into the environment.

Working of Boiler

There are a number of boilers available in the market that have their respective construction and working. To understand the working of a typical boiler, consider the working of a water tube boiler. A water tube boiler typically makes use of an arrangement of tubes through which the water is made to flow. The tubes are further surrounded by heating devices or fire that tend to supply heat energy to the pipes. The pipes are constructed with the help of conductors, hence the heat gets linked to the water molecules present inside the tube. This causes the molecules to vibrate at high velocity. The conversion of heat energy into kinetic energy can be observed easily. Further heating of the water causes the production of steam. The steam passes on to the upper drum and can be extracted out through the steam outlet. The steam produced as a result can now be linked to various applications such as rotating the turbine or rotor blades of a device, and many more.

Working of Boiler

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