Boiler- Introduction, Classification, Mountings and accessories, efficiency and draught.

The Mechanical engineering, is playing a vital role in today's Technology.
It Assist you to done things with ease, and also it brings the helpful technologies to modernize our society.

So keeping these things in mind, Lets learn about the Boiler- Introduction, Classification, Mountings and accessories, efficiency and draught.
Boiler- Introduction, Classification, Mountings and accessories, efficiency and draught.
Boiler- Introduction, Classification, Mountings and accessories

Boiler introduction:-

A boiler is usually closed vessel and it is made from steel.

The function of boiler is to transfer the heat produced by the combustion of fuel to water and ultimately to generating the steam.

The selection of type and size of a boiler is depending upon the following factors.

  • The power required and the working pressure in boiler.
  • The probable load factor.
  • The fuel and water availability.
  • The geographical position of the power house .

Classification of steam boilers:-

There are many classification of steam boilers at the following are important from the subjective point of view.

1. According to contents in the tube

A. Fire tube or smoke tube boiler
B. Water tube boiler

2. According to the position of the furnace

A. Internally fired boiler
B. Externally fired boiler

3. According to the axis of the shell

A. Vertical boiler
B. Horizontal boiler

4. According to the number of tubes in a boiler

A. Single tube boiler
B. Multi tube boiler

5. According to the method of circulation of water and steam in boiler

A. Naturally circulation boiler
B. Forced circulation boiler

6. According to use of boiler

A. Stationary boiler
B. Mobility boiler

7. According to the source of heat given to the boiler

A. Electrical energy sourced boiler
B. Nuclear energy sourced boiler 
C. Solid liquid and gaseous or hot waste gases boiler.

By applying above filter to the boiler there are several types of boilers as follows that are important as a subject view point:-

  1. Simple vertical boiler 
  2. Cochran boiler or vertical multi tubular boiler.
  3. Scotch Marine boiler
  4. Cornish boiler
  5. Lancashire boiler
  6. Locomotive boiler
  7. Babcock and wilcox boiler
  8. La-mont boiler

Boiler mountings:- 

Boiler- Introduction, Classification, Mountings and accessories, efficiency and draught.
Boiler mountings

For the proper and safe functioning of the boiler some are the fittings are mounted to the boiler is called as boiler mountings.

Some of the important while the mountains are as follows:

1. Water level indicator:

This indicating the water level inside the boiler to an operator.
This is the safety device on which the correct working of the boiler are totally depends.
This fittings may be seen in front of boilers generally it is in two numbers.

2. Pressure gauge:

Pressure gauge is used to measure the pressure in the steam inside the steam boiler.
It is fixed in front of the boiler.
The pressure gauge generally used are bourdon tube pressure gauge.

3. Safety valves:

These are attached to the steam chest for preventing explosion due to excessive internal pressure of the steam.
Boiler usually provides with the two safety valves and that are directly placed on the boiler.
Following are the mean type of safety valves used in a boiler.
  • Level safety valve
  • Dead weight safety valve
  • Spring loaded safety valve
  • High steam and low water safety valve.

4. Steam stop valve:

It is the largest valve on the steam boiler and it usually fitted to the highest part of the shell by means of flange.
Used to control the flow of steam of boiler with the main pipe
Also used to turn off the steam completely when required.

5. Blow off cock:

It is used to:
To empty the boiler when you were required. 
To discharge the mud, scale or sediments at the bottom of the boiler.

6. Feed check valve:

It is a non return valve which are fitted to a screwed spindle to regulate the lift.
The main function of this valve is to regulate the supply of water that are pumped into the boiler by the feed pump.
It fitted to the shell slightly below the normal water level of the boiler.

7. Fusible plug:

It is fitted to the fire box. 
When the level of the water in a boiler falls down then to avoid the explosion due to overheating of the furnace plate this fusible plug is used.

Boiler accessories:-

Boiler- Introduction, Classification, Mountings and accessories, efficiency and draught.
Boiler accessories

The accessories which are used as an integral part of the boiler and that helps to increase the efficiency that called boiler accessories.

1. Feed pump:-

Feed pump is uses to delivery of water to the boiler.
Feed pump are centrifugal type or reciprocating type.
Now a days a double acting reciprocating pump is commonly used as a feed pump.

2. Superheater:- 

Superheater is an important device of a steam generating units.
Its purpose is to increase the temperature of saturated steam without raising its pressure.
It is generally an integral part of a boiler and is placed in a path of hot flue gases from the furnace.

3. Economiser:- 

Economizer is a device used to heat feed water by utilising the heat in exhaust gases before leaving through the chimney.
It improves the economy of a steam boiler.

By the use of economiser following advantage getting: 
  • The cool saving is about 15 to 20% .
  • It increases the steam arising capacity of boiler because it shorten the time required to convert the water into the steam.
  • To prevent formation of scale in water tube because the scale formed in economiser can be cleaned easily.

4. Air preheater:-

The air preheater is used to preheat the fresh air by using the heat of wastage of fuel gases.
Intezar important accessories to increase the efficiency of the boiler.

5. Steam injector:-

Steam injector used to lift and force the feed water into the boiler.
The steam engine connector on the boiler to increase the performance of boiler.

Boiler efficiency:-

The boiler efficiency defined as the ratio of heat actually used in producing the steam to the heat liberated in the furnace.
It is called the thermal efficiency of boiler.

Heat losses in boiler:-

Following are the heat losses happen in a boiler

  1. Heat loss due to dry flue gases
  2. Heat loss due to moisture present in the fuel
  3. Heat loss due to steam formed by combustion of hydrogen.
  4. Heat loss due to incomplete combustion of carbon to the carbon monoxide.
  5. Heat loss due to radiation.
  6. Heat loss due to unburnt carbon in ashpit.

Boiler draught:-

It is the difference of pressure as above and below the fire gate.
The main object of providing brought in a boiler are:
  • To provide adequate supply of air for the fuel combustion.
  • To exhaust gases of combustion from the combustion chamber.
  • Discharge gases to the atmosphere through the chimney.

1. Natural draught:

It is the draught produced by a chimney due to the difference of density is between the hot gases inside the chimney and cold atmospheric air outside.
It is also called chimney draught.

2. Mechanical or artificial draught:

It is a draught produced by a fan, blower or steam jet.
Generally the mechanical draught is provided when natural draught is not sufficient, it may be induced or forced.

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