The fire-tube boilers are most commonly used all over the world for various applications. There are multiple types of boilers, and the Cornish boiler is one of them. Cornish boiler has a similar design as the Lancashire boiler. This article mainly explains the Cornish boiler working, parts, and applications.
What is a Cornish Boiler?
Cornish boiler is an internally fired horizontal fire tube boiler in which the hot gases flowing through a tube increase the temperature of the surrounding water to produce steam.
It is the most famous type of fire tube boiler. It has a cylindrical shell that is installed in the horizontal direction. This shell has a 1.25 m to 1.7 m diameter and 4 m to 7 m length. In 1812, Richard Trevithick designed the first Cornish boiler.
The design of the Cornish boiler is very similar to the Lancashire boiler. However, the Lancashire boiler has more efficiency than the Cornish boiler. The Lancashire boilers have a steam generation rate of up to 9000kg/hour and steam pressure of up to 16 bar, while Cornish boilers have a steam generation rate of up to 6500 kg/hour and steam pressure of up to 10.5 bar.
These types of boilers are most commonly used in sugar mills, textile industries, and steam turbines.
Working Principle of Cornish Boiler
A Cornish boiler works on the thermal conduction principle. In this boiler, the water converts into steam by transferring the heat of the hot flue gases into the surrounding water.
A Cornish boiler works in the following way:
- Coal fuel is placed on the grate of the furnace, and the furnace burns to this fuel.
- Due to the coal combustion, heat is generated, which transfers to the flue gases.
- As the flue gases get heat, their temperature increases, and they start flowing into the fire tube.
- This fire tube fully immerses in the water.
- The hot gases inside the fire tube transfer their heat to the outer water.
- After passing through the internal fire tube, the hot flue gases flow toward the bottom side, where the heat transfers to the bottom water. In this way, the side water is heated by the side flue and the bottom by the bottom flue.
- In this way, flue gases transfer their heat to the water. As the water gets heat, its temperature increases. Due to an increase in the temperature, the water transforms into steam.
- The resulting steam is directed toward the steam turbine for electricity production.
- After passing by the bottom flue, the useless gases and smoke remove into the atmosphere through a chimney.
Read Also: Working of Lancashire Boiler
Parts of Cornish Boiler
The Cornish boiler has the following major parts:
- Blow off valve
- Stop Valve
- Man Hole
- Safety Valve
- Water level indicator
- Combustion chamber
A shell is one of the most important components of the Cornish boiler. It provides basic safety to the internal parts of the boiler. It is an external part.
This component of the boiler contains all the inner parts of the boiler. The boiler water and fire tube are enclosed inside the shell. It is most commonly made of steel.
The grate is an internal part of the boiler. It installs at the furnace bottom. The solid fuel is placed on this part so that the combustion process can take place. It is most commonly made of cast iron.
The grate is designed in such a way that it can permit air to enter the furnace for the burning process. It has enough space so that unburnt fuel and ash of the burned fuel can easily go into the ash pit.
Read More: Different Types of Fire-tube Boilers
It is an area where the combustion process takes place. The main purpose of the furnace is to burn fuel. As the fuel-burning occurs, heat is produced, which further transfers to the flue gases. As the flue gases get heat, they go into the combustion chamber.
4) Fire Tubes
The fire tubes use in the fire tube boiler. The Cornish boiler has only one fire tube. It contains hot flue gases while water surrounds it.
The hot flue gases transfer their heat to the walls of the fire tube, and this tube further transfers its heat to the surrounding water. This heat transfer process occurs through the thermal conduction process. In this way, this tube plays a vital role in the conversion of water into steam.
Read Also: Different Types of Boilers
5) Ash Pit
It uses to collect the unburnt fuel and ash of the burnt fuel. The grate has enough space from where unburnt fuel and ash move into the ash pit.
6) Smoke Box
This is another important component of the boiler. The burning process of the fuel in the furnace generates smoke.
This smoke sends into the smokebox, which further transfers to the chimney from where it transfers into the atmosphere. In this way, smoke is discharged from the boiler into the atmosphere.
This part of the boiler uses to collect the useless or unburnt gases and smoke of the burnt fuel. As the smoke and useless gases are collected into the chimney, then they discharge into the atmosphere.
8) Pressure Gauge
The pressure gauge uses to measure the internal pressure of the boiler. You can install it permanently with the boiler. It has different readings which indicate the internal boiler pressure. Through these readings, you can easily prevent your boiler from the explosion by removing excess steam pressure.
9) Water Indicator
It indicates the water level inside the boiler. This unit also has different symbols or readings that help you understand the water level inside the boiler. In case of a low water level, you can refill your boiler with water.
10) Safety Valve
This valve provides safety to your boiler. It prevents the boiler from the explosion. This part of the Cornish boiler works automatically.
The safety valve automatically opens and removes the extra pressure as the steam pressure increases more than desired or boiler bearable pressure. In this way, it ensures the safety of the boiler.
11) Stop Valve
It uses to regulate the flow of steam and water. It is a one-way valve.
Read Also: Types of Valves
This is a hole from where a worker can enter into the boiler. This part of the boiler uses to clean and repair the various parts of the Cornish boiler.
Construction of Cornish Boiler
The exterior shell of the boiler is the shortest component. This is the external component of the Cornish boiler which surrounds other internal components. It provides protection to other parts.
The boiler has a furnace which uses to burn or combust solid fuels. It is an internal component of the boiler. This unit installs at the bottom of the boiler. This furnace has a fire hole from where the fuel introduces into the furnace.
The fire watch installs in the center of the water area. A brick arc uses to stop the ash of the combusted fuel into the flue tube and fire tubes.
The Cornish boiler has one flue tube located at the boiler bottom, which is known as the bottom flue, and two flue tubes are located at the two sides, which are known as side flues. It also has another grip tube known as the main grip tube.
After passing through these tubes, the flue gas enters the chimney. This chimney uses to remove waste gases into the atmosphere.
The boiler has a safety valve. It is a spring-loaded valve. The name of this valve represents that it provides safety to the boiler. It prevents the boiler from explosion due to excess steam pressure. It works automatically. As the steam pressure inside the boiler becomes more than the boiler’s tolerable limit, the safety valve opens and removes the excess steam pressure.
A stop valve uses to control the flow of steam into the steam pipes. It installs on the boiler’s top.
The boiler uses a feed pump to pump the water inside the boiler. It is an external part of the boiler. Multiple types of pumps (i.e., reciprocating pump, piston pump, plunger pump, submersible pump, and centrifugal pump) are used to transfer water into the boiler.
A feed pipe uses to transfer the water from the reservoir into the boiler. It controls with the help of a feed valve. This feed valve works as a one-way valve. It avoids the backflow of the water.
A blow-off coke uses to emilite the contamination from the boiler floor. There is also a manhole. The engineer and other workers use this hole for the inspection and repair of the inner boiler components.
Advantages and Disadvantages of Cornish Boiler
The Cornish boiler has the following advantages and disadvantages:
Advantages of Cornish Boiler
- These are the best boilers for low-pressure applications.
- The Cornish boilers have an easy design.
- They have a simple operation.
- These are portable boilers. In simple words, you can easily transfer them from one place to another.
- The Cornish boiler has a low maintenance cost.
- These have the capability to handle load fluctuation.
- They have low weight.
Disadvantages of Cornish Boiler
- These boilers don’t have a high steam generation rate (i.e., up to 1350 kg/hour) as Lamont boilers.
- It has a low steam pressure production rate.
- These are not suitable for high-pressure applications.
- This boiler needs a large space for installation because of its horizontal structure.
Applications of Cornish Boiler
- The Cornish boiler is most commonly used in hydroelectric power plants and sugar mills.
- These boilers are also used in chemical industries and steam turbines.
- They also use in marine.
Cornish Boiler VS Lancashire Boiler
The main difference between the Cornish boiler and the Lancashire boiler is given below:
|In 1812, Richard Trevithick developed the Cornish boiler.
|In 1844, William Fairbairn developed the Lancashire boiler
|It has only one fire tube.
|It has two fire tubes.
|The Cornish boiler has a shell which has a length from 4 m to 7 m.
|The shell of the Lancashire boiler has a length from 6 m to 10 m.
|The diameter of the shell is 1.25m -1.75m
|The shell of this boiler has a diameter from 2 m to 3 m.
Cornish boiler is an example of which type of boiler?
A Cornish boiler is an example of a fire tube boiler.
What are the common components of the Cornish Boiler?
- Blow off valve
- Stop valve
- Safety valve
- Water level indicator
- Combustion chamber
Who Invented the Cornish Boiler?
In 1812, Richard Trevithick invented the first Cornish boiler.
How many fire tubes are there in Cornish boiler?
The Cornish boiler has only one fire tube.
What is boiler water limit?
To ensure compliance with TDS (Total Dissolved Solids) regulations, low-pressure boilers must maintain a maximum limit of 3500 ppm. However, for higher-pressure boilers, the TDS limit is adjusted proportionally according to the pressure rating. As a preventive measure, the operator is required to periodically open the blowdown valve of the boiler in order to control and release excess TDS levels.