Benson boiler - Working, Advantages, Main Parts and Diagram

What is Benson boiler? 

The Benson boiler is a high pressure, forced circulation, once through the boiler and water tube boiler. The Benson boiler is introduced by Benson and he argued that if the boiler pressure is raised above the critical pressure (225 atm.), the steam and water have the same density, therefore bubbles would not be formed. Hence, the difficulty experienced in the case of the La-mount boiler as the danger of bubbles formation can be easily eliminated. 

This boiler also is known once-through boiler as in this case water is fed to the boiler at one end and superheated steam discharged through the other end. Hence, the entire operation of feedwater heating, steam formation (evaporation), and superheating are taken place in a single tube without the use of a drum. In the case of non-once through boilers only a fraction of water flowing in the steam-generating tubes is evaporated and remains water is recirculated through the drum & evaporating tube. 

The Main parts of Benson Boiler are:

  1. Air preheater
  2. Economizer
  3. Radiant Superheater
  4. Convection Evaporator
  5. Convection superheater
  6. Feed pump


1. Air preheater: 

The function of the air preheater is to recover the waste heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the flue gas.

2. Economizer:

 A common application of economizers in steam power plants is to capture the waste heat from boiler flue gas and transfer it to the boiler feedwater.

3. Radiant Superheater:

The function of a radiant superheater is to heat the water with radiation produced by burnt fuel. It raises the temperature of water to supercritical temperature.

4. Convection Evaporator: 

The convection is used to transfer heat from the flue gases to water. The function of the evaporator is to evaporate the water completely.

5. Convection superheater:

It superheats the steam to the desired temperature and this superheated steam is taken out for the useful industrial work.

6. Feed pump:

It is a boiler accessory needed to force the feed water at high pressure into the boiler.


Working of Benson Boiler: 

  • The feedwater is supplied by a feed pump at a pressure higher than 225 atm. This water passes through the economizer and then a radiant evaporator where most of the water is evaporated as shown in fig.



  • The remaining water evaporated in a convective evaporator and converted into steam. The steam is passed through the superheater and finally supplied to the prime mover.


Advantages of Benson boiler: 

1. The generation of steam in evaporating tubes at a pressure higher than critical pressure (225 atm). Therefore, do not require any evaporator drum. 

2. There no drum, the total weight of the boiler is 20 % less than other boilers. It reduces the cost of the boiler. 

3. Natural circulation boiler requires expansion joints but it does not require in the Benson boiler. Hence Benson boiler can be started very quickly because of welded joints. 

4. The erection of the Benson boiler is easier and quicker as all the parts are welded at the site. 

5. The superheater of the Benson boiler is an integral part of the forced circulation and hence no special starting arrangement for the superheater is required. 

6. At part and overload the Benson boiler can be operated economically by varying temperature and pressure. The desired temperature of steam can be maintained constant at any pressure. 

7. Benson boiler is very suitable for fluctuating demand because there is no formation of bubbles when demand (load) is suddenly decreased. 

8. High generation rate of steam. Hence suitable for power generation plants. 

9. It requires less space. 

Also Read: Horizontal Axis Wind Turbine

Disadvantages: 

1. Salt deposition and sediment on the inner surface of the water tubes. 

2. Danger of overheating. 

Also Read: Cochran Boiler


Benson boiler - Working, Advantages, Main Parts and Diagram Benson boiler - Working, Advantages, Main Parts and Diagram Reviewed by Harish on September 24, 2020 Rating: 5

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