Short Answer:

The examples of fire-tube boilers include Cochran boiler, Lancashire boiler, Cornish boiler, Locomotive boiler, and Scotch marine boiler. These boilers are simple in design and operate at low to medium pressure. In all these types, hot gases pass through tubes surrounded by water, converting the water into steam.

In simple words, fire-tube boilers are mainly used for small and medium steam generation applications. The most popular examples such as the Cochran and Lancashire boilers are commonly used in industries, heating systems, and marine applications due to their low cost, easy maintenance, and reliable operation.

Detailed Explanation :

Examples of Fire-Tube Boilers

A fire-tube boiler is a type of boiler in which hot flue gases pass through tubes surrounded by water inside a shell. The heat from these gases is transferred through the walls of the tubes to the surrounding water, converting it into steam. Fire-tube boilers are widely used in industries where low and medium-pressure steam is required, such as textile mills, sugar industries, and small power plants.

There are several types of fire-tube boilers designed for different purposes, but their working principle remains the same. Below are some of the most commonly used examples of fire-tube boilers.

1. Cochran Boiler

The Cochran boiler is a vertical, multi-tubular, and internally fired boiler. It is compact, simple in design, and widely used for small steam generation.

Construction:

• It has a hemispherical shell and furnace which provides maximum strength and heat transfer area.
• The fire tubes are arranged horizontally inside the shell, surrounded by water.
• The chimney is placed at the top for exhaust gases.

Working:

• Fuel is burned in the furnace, and the hot gases flow through the fire tubes.
• These gases heat the water surrounding the tubes, producing steam.
• The steam collects in the upper part of the shell and is used for industrial purposes.

Applications:

• Used in small industries, workshops, and heating plants.
• Suitable for producing steam up to 6.5 bar pressure.

Features:

• Compact and portable.
• Low cost and easy to maintain.

2. Lancashire Boiler

The Lancashire boiler is a horizontal, internally fired, fire-tube boiler. It is one of the most commonly used stationary boilers in industries.

Construction:

• It consists of a large cylindrical shell filled with water.
• Two large furnace tubes pass through the shell, where hot gases flow.
• The rear end of the furnace tubes connects to a firebrick-lined combustion chamber.
• Hot gases pass through a series of flues before leaving through the chimney.

Working:

• The fuel is burned on the grate inside the furnace tubes.
• Hot gases move through the tubes, transferring heat to the surrounding water.
• The steam formed rises to the top of the shell and is collected for use.

Applications:

• Used in textile industries, sugar mills, and paper factories.
• Operates at pressures up to 15 bar.

Features:

• High efficiency due to multiple flues.
• Economical and reliable for stationary applications.

3. Cornish Boiler

The Cornish boiler is similar to the Lancashire boiler but has only one large flue tube. It is a horizontal, internally fired, fire-tube boiler.

Construction:

• It consists of a cylindrical shell containing a single large flue tube.
• The furnace is located inside this tube, where fuel combustion takes place.
• The rear end of the tube connects to a brick-lined passage that leads to the chimney.

Working:

• Hot gases produced in the furnace travel through the main flue and then through side flues before escaping through the chimney.
• Water surrounding the flue tubes absorbs heat and converts into steam.

Applications:

• Used for small-scale power generation and heating purposes.
• Common in industries requiring steam below 10 bar.

Features:

• Simple design and easy maintenance.
• Lower efficiency compared to the Lancashire boiler.

4. Locomotive Boiler

The locomotive boiler is a horizontal, multi-tubular, and externally fired boiler used in railway engines.

Construction:

• It consists of a large cylindrical boiler shell with many small fire tubes inside.
• A grate is provided for fuel burning, and a smoke box collects exhaust gases.
• The boiler has a steam dome, safety valve, and chimney.

Working:

• Coal is burnt on the grate, and the hot gases produced pass through multiple small fire tubes.
• The water surrounding the tubes absorbs heat and converts into steam.
• The steam is used to drive pistons in the locomotive engine.

Applications:

• Used in railway locomotives and portable steam engines.

Features:

• Capable of producing large quantities of steam quickly.
• Compact and suitable for mobile applications.

5. Scotch Marine Boiler

The Scotch marine boiler is a horizontal, multi-tubular, fire-tube boiler commonly used in ships and marine applications.

Construction:

• It has a cylindrical shell containing multiple fire tubes.
• The furnace is placed inside the boiler, surrounded by water.
• The hot gases from the furnace pass through these tubes and exit through the chimney.

Working:

• The fuel is burned in the furnace, and the resulting hot gases flow through the fire tubes.
• The heat from these gases is transferred to the water, producing steam.
• The steam is used to operate engines or turbines on ships.

Applications:

• Used in marine ships and naval vessels for steam propulsion.

Features:

• Compact and strong construction.
• Suitable for marine environments due to durability.

6. Simple Vertical Boiler (Additional Example)

The simple vertical boiler is a small, vertical fire-tube boiler mainly used for laboratory and small-scale applications.

Construction:

• It has a vertical cylindrical shell filled with water.
• A furnace and grate are provided at the bottom.
• Hot gases rise through the vertical fire tubes surrounded by water.

Working:

• Fuel burns on the grate, and hot gases rise through the tubes.
• The heat converts the surrounding water into steam, which is collected at the top.

Applications:

• Used for small steam engines, testing labs, and workshops.

Conclusion

The examples of fire-tube boilers include Cochran, Lancashire, Cornish, Locomotive, and Scotch marine boilers. These boilers are designed for low and medium-pressure steam generation and are easy to operate and maintain. They are mainly used in industries, ships, and railway engines where moderate steam requirements exist. Although fire-tube boilers are less efficient than water-tube boilers, their simplicity, low cost, and reliability make them suitable for a wide range of practical applications.