Loeffler Boiler: Definition, Parts, Working, Advantages, Disadvantages, and Applications

Want to know about Loeffler Boiler?

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Loeffler Boiler is a forced circulation, high pressure, and water tube boiler with an internally fired furnace.

In this boiler, 2/3 of superheated steam is used to evaporate the water in the evaporating drum and the remaining 1/3 of the steam from the superheater is used by the turbine.

Steam circulating pump is used to circulate the steam into the boiler. The Loeffler boiler is an addition to the Lamont Boiler.

Parts or construction of Loeffler Boiler-

Here are some parts and construction-

  • Economiser
  • Evaporative Drum
  • Mixing Nozzle
  • Steam circulating Pump
  • Radiant Superheater
  • Convection Super Heater
  • Steam Outlet


The feed water from the feed tank is supplied to the economiser by the feed pump. It is known as Air preheater.

In the economiser, the feed water is made to flow through a number of tubes surrounding which the hot gases leaving the furnace to pass over.

There is a heat exchange from the hot gases to the feed water, which is preheated in the economiser.

Evaporative Drum-

It is housed away from the furnace. It contains a mixture of steam and water.

The feed water from the economiser tubes enters the evaporator drum into which is also passed 2/3 of the superheated steam generated by the boiler.

The superheated steam gives its superheat to the water in the drum and evaporate it to saturated steam.

Mixing Nozzle-

The nozzle distributes and mixes the superheated steam throughout the water in the evaporator drum.

Steam circulating Pump

Steam circulating pump forces this saturated steam from the evaporator drum to the radiant heater through the tube of the furnace wall.

Radiant Superheater

The radiant superheater is placed in the furnace. The hot gases in the furnace are used for superheating the saturated steam from the drum.

The radiant superheater receives heat from the burning fuel through the radiation process.

Convection Super Heater

Steam from the radiant heater enters into the convection superheater where it is finally heated to the desired temperature of 500°C.

The convection superheater receives heat from the flue gases entirely by convective heat transfer.

Both radiant and convection superheaters are arranged in series in the path of flue gases.

Steam Outlet-

About 1/3 of the superheated steam from the convection superheater passes to the steam turbine while the remaining 2/3 is passed onto the evaporator drum to evaporated the feed water to saturated steam.


The capacity of this boiler is about 100tones/hour of superheated steam generated at a pressure of 140kgf/sq.cm and at a temperature of 500°C.

Loeffler boiler diagram-

loeffler boiler diagram

Now, let’s move to the working section, where you know the fundamental working of this boiler. So, here I dive in-

Working of Loeffler Boiler-

The feed pump draws water from the hot well and delivers it to evaporating drum through the economiser.

About 65% of the steam coming out of the superheater is passed through the evaporator drum in order to evaporate the feed water coming from the economiser.

Steam circulating pump draws the saturated steam from the evaporator drum and then passed through the radiant and then convective superheater.

About 35% of the steam coming out from the superheater is supplied to the turbine.

This was the Loeffler boiler working principle.


Here are some advantages of Loeffler Boiler-

  • High salt concentration
  • Compact
  • High steam generation capacity
  • Flexible operation
  • Economical


Here are some Disadvantages of Loeffler Boiler-

  • Bubble formation
  • havier and costly part

These were the Loeffler boiler advantages and disadvantages, now let’s move to its applications.


Here are some Loeffler boiler applications-

  • Steam generation
  • Marine Industry
  • Power Generation

Still, want to more?

Here is the video guide, which will further help you to know more, Give a watch-

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If you have any questions or any suggestions, feel free to ask and say in the comment section down below or through various preferred contact mediums.

If want to read more, then here are some suggested articles-

Benson Boiler

Velox Boiler

LaMont Boiler

Thank you for being with me. I hope to see you in the next session.


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Before you go. here is some Q&A and MCQ session of this article, you should have a look…


What type of boiler is a Loeffler boiler?

Loeffler Boiler is a forced circulation, high pressure, and water tube boiler.

What is the working pressure of a Loeffler boiler?

The working pressure of the Loeffler Boiler is 140kgf/sq.cm.

Is the Loeffler boiler a high-pressure boiler?

Yes!! Loeffler Boiler is a high-pressure boiler.

In the high-pressure natural circulation boilers, the flue gases flow through the following boiler accessories-
A. Superheater
B. Air-preheater
C. economizer
D. Fan
The correct sequence of the flow of the flue gases through these boiler accessories is-
1. A, B, C, D
2. A, B, D, C
3. B, A, C, D
4. A, C, B, D

Answer- 4. A, C, B, D

Which of the following are boiler mountings and not boiler accessories?
A. Pressure gauge
B. Air-preheater
C. Superheater

Answer- A. Pressure gauge

What are the advantages of water tube boilers over fire tube boilers?
A. Steam at higher pressures can be produced
B. More effective heat transfer
C. Sediment deposition is more

Answer- A and B

What is the primary function of a steam trap in a boiler?
A. Recover heat from exit gases
B. Increase temperature of steam above the saturated temperature
C. Separate the water particles from the steam
D. Drain off condensed water accumulating in the steam pipelines

Answer- D. Drain off condensed water accumulating in the steam pipelines

The heat loss in a boiler takes place in the form of——-
A. Heat carried away by flue gases
B. Heat carried away by ash
C. Moisture present in fuel and steam formed by combustion of hydrogen in fuel
D. All of above

Answer- D. All of above

The diameter of tubes for natural circulation boiler as compared to controlled circulation boiler is-
A. More
B. Less
C. Same
D. Could be more or less depending on other factors

Answer- A. More

Which of the following boilers is the best suited to meet the fluctuating demands?
A. Babock & Wilcox
B. Locomotive boiler
C. Lancashire
D. Cochran

Answer- B. Locomotive boiler


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