Table of Contents

Types of Boilers | How Boilers are Classified ?

INTRODUCTION TO BOILERS: –

Boiler is a closed vessel in which heat produced by combustion of fuel is transferred to water for its conversion in to steam at the desired temperature and pressure. According to IBR a boiler is closed pressure vessel with capacity exceeding 25.75 Lits used for IBR a boiler is closed pressure vessel with capacity exceeding 25.75 Liters used for generating steam under pressure it includes all the mountings fitted to such vessels which remains wholly or partly under pressure when steam is shut off.

Classification of boilers :

The boilers may be classified as under

1. Horizontal, Vertical or Inclined boilers

(a) Horizontal boiler:- If the axis of the boiler shell is horizontal, it is called the horizontal boiler. Example: Lancashire boiler, Locomotive boiler

(b) Vertical boiler :- If the axis of the boiler is vertical it is called the vertical boiler. Example: Cochran boiler

(c) Inclined boiler :- If the axis of the boiler is inclined it is known as inclined boiler.

2. Fire tube and water tube boilers :-

(a) Fire tube boiler :– The boilers in which the hot gases are inside the tubes and water is surrounding the tubes is called fire tube boiler. Example : Cochran, Lancashire and Locomotive

(b) Water tube boiler :– The boilers in which the water is inside the tubes and the hot gases surround them is called water tube boilers. Example : Babcock and Wilcox boiler.

3. Externally tired and internally tired boilers

(a) Externally fired boiler :- In the boiler if the fire is outside the shell, that boiler is known as externally fired boiler. Example : Babcock & Wilcox boiler

(b) Internally fire boiler :- In the boiler in which the furnace is located inside the boiler shell it is known as internally fired boiler. Example : Cochran boiler, Lancashire boiler etc.

4. Forced Circulation and Natural circulation boilers :

(a) Forced circulation boiler :– In the boilers if the circulation of water is done by a pump then they are known as forced circulation boilers. Example : Velox boiler, Lamount boiler, Benson boiler etc.

(b) Natural circulation boiler :– In the boiler if the circulation of water takes place due to difference in density resulting from difference in temperature, it is known as natural circulation boiler. Example : Lancashire boiler, Babcock and Wilcox boiler etc.

5. High Pressure, Medium Pressure and Low Pressure boilers

(a) High Pressure steam boiler :– It is one in which the working pressure of the boiler is more than 25 bar. Example : Babcock & Wilcox boiler.

(b) Low Pressure steam boiler :– It is defined as a steam boiler whose working pressure is between 3.5 to 10 bar. Example : Cochran and Cornish boiler.

(c) Medium pressure boiler :- It is that boiler whose working pressure (pressure of steam and water in the shell) is between 10 bar to 25 bar. Example: Lancashire boiler and Locomotive boiler

6. Stationary boiler and Portable boiler:-

(a) Stationary boilers :- The boilers which cannot be transported easily from one place to another are called stationary boilers. Example: Lancashire boiler, Babcock and Wilcox boiler

(b) Portable boiler :- The boilers which can be easily transported (moved) from one place to another are called portable boilers. Example: Locomotive boiler.

7. Single tube boilers and multi tube boilers :-

(a) Single tube boilers : The boiler having only one fire tube or water tube is called single tube boiler. Example: Cornish boiler

(b) Multi tube boiler :– The boiler having two or more fire or water tubes for the circulation of hot gases or water are called multi tube boiler. Example : Lancashire boiler, Locomotive boiler, Cochran boiler, Babcock and Wilcox boiler etc.