Short Answer:

The examples of water-tube boilers include Babcock and Wilcox boiler, Stirling boiler, Lamont boiler, Benson boiler, and Loeffler boiler. In these boilers, water flows inside the tubes and is heated by the hot gases flowing outside the tubes. These types of boilers are mainly used for high-pressure and high-temperature applications.

In simple words, water-tube boilers are used in large industries and power plants where large quantities of steam are required. Examples like Babcock and Wilcox and Lamont boilers are widely used because they can produce steam quickly, efficiently, and safely at very high pressures.

Detailed Explanation :

Examples of Water-Tube Boilers

A water-tube boiler is a type of boiler in which water flows inside the tubes while hot flue gases flow outside the tubes. These boilers are suitable for high-pressure and high-temperature steam generation, unlike fire-tube boilers that are used for low-pressure applications.

Water-tube boilers are used in thermal power plants, chemical industries, marine engines, and refineries. The design allows for faster heat transfer, efficient operation, and safety under high-pressure conditions. Some of the most commonly used examples of water-tube boilers are discussed below.

1. Babcock and Wilcox Boiler

The Babcock and Wilcox boiler is one of the most popular and widely used water-tube boilers. It is a horizontal, stationary, high-pressure, and multi-tubular boiler.

Construction:

• It consists of a large drum connected to several inclined water tubes.
• The drum contains water at the lower part and steam at the upper part.
• A furnace is provided below the tubes, and the hot gases from combustion pass over the water tubes.
• The superheater, air preheater, and economizer are added to improve efficiency.

Working:

• Water is supplied into the drum, and it circulates through the tubes.
• The furnace burns fuel, producing hot gases that flow over the tubes.
• Heat is transferred from the gases to the water, converting it into steam.
• The steam is collected at the top of the drum and then sent to the superheater or directly to turbines.

Applications:

• Used in power plants and industries where large quantities of high-pressure steam are required.

Features:

• Produces steam up to 40 bar pressure.
• High efficiency due to large heating surface area.

2. Stirling Boiler

The Stirling boiler is a high-pressure, multi-drum, bent-tube water-tube boiler. It is mainly used in large industrial and power generation applications.

Construction:

• It consists of three or four drums connected by banks of bent tubes.
• The lower drum holds water, while the upper drum collects steam.
• The furnace is placed below the tubes, and baffles are used to direct the flow of hot gases.

Working:

• Hot gases from the furnace flow over the bent tubes, transferring heat to the water inside.
• The heated water turns into steam and rises to the upper drum.
• The separated steam is collected and supplied to turbines or other equipment.

Applications:

• Used in marine boilers and power stations for high-pressure steam generation.

Features:

• High evaporation rate and rapid steam generation.
• Excellent circulation of water due to multiple drums.

3. Lamont Boiler

The Lamont boiler is a forced circulation, high-pressure water-tube boiler. It was developed to overcome the limitation of slow natural circulation in conventional boilers.

Construction:

• It consists of a steam separator drum and a circulating pump.
• Water from the drum is circulated through evaporator tubes by a centrifugal pump.
• The superheater and economizer are included for better efficiency.

Working:

• The circulating pump forces water from the drum into the tubes, where it is heated by flue gases.
• The water partially turns into steam and returns to the drum.
• The separated steam is then superheated before being sent for use.

Applications:

• Widely used in marine and stationary power plants for high-pressure steam generation.

Features:

• Produces steam at pressure up to 170 bar.
• High efficiency due to forced circulation and compact design.

4. Benson Boiler

The Benson boiler is a supercritical, high-pressure water-tube boiler that operates without a steam drum.

Construction:

• It consists of straight tubes through which water flows and is heated directly by the combustion gases.
• It does not have a drum because it operates above the critical pressure (around 225 bar), where water and steam coexist in the same phase.

Working:

• Feedwater is pumped into the boiler tubes, where it absorbs heat continuously.
• As the water passes through the tubes, it gradually changes into steam without any separation process.
• The superheated steam is then supplied to turbines for power generation.

Applications:

• Used in supercritical power plants for high efficiency and reduced fuel consumption.

Features:

• No drum, compact design, and light weight.
• Efficiency up to 90% due to continuous heat absorption.

5. Loeffler Boiler

The Loeffler boiler is another forced circulation water-tube boiler that uses superheated steam to evaporate feedwater.

Construction:

• It has a steam separator drum, evaporator tubes, and a superheater.
• The steam generated in the boiler is divided into two parts — one part is sent to the superheater and turbine, while the other part is used to heat feedwater.

Working:

• Feedwater is first preheated by exhaust gases and then evaporated using superheated steam from the turbine.
• The resulting steam is again superheated before being sent back to the turbine.
• This process eliminates the problem of salt and sediment deposition in tubes.

Applications:

• Used in large thermal power plants for high-pressure, large-scale steam generation.

Features:

• Steam generation up to 140 bar pressure.
• Reduced scaling and maintenance requirements.

6. Other Examples

Some additional examples of water-tube boilers include:

• Yarrow boiler – widely used in ships and marine applications.
• Velox boiler – a compact, high-efficiency boiler using gas turbines for air compression.

Conclusion

The examples of water-tube boilers include Babcock and Wilcox, Stirling, Lamont, Benson, and Loeffler boilers. These boilers are designed for high-pressure, high-efficiency steam generation and are mainly used in power plants, marine systems, and industrial applications. Unlike fire-tube boilers, they are safer and more efficient due to rapid heat transfer and better water circulation. Although they are complex and expensive, their performance and reliability make them essential for modern steam power generation systems.