Lancashire Boiler is a horizontal, low pressure, internally fired, stationary fire tube and natural circulation boiler.
This boiler was invented in the year 1844 by William Fairbairn.
William Fairbairn was a Scottish civil engineer.
It is called internally fired because the furnace is present inside the boiler.
The main purpose of this boiler is to produce steam and this steam is used for different purposes.
The length of the boiler is 7-9 meters and the diameter of the boiler is nearly 2-3 meters.
This boiler is mostly is used to drive steam engines, marines and locomotive engines.
Lancashire boiler has a pressure range of 16 bar ( maximum ). Its steam production rate is 9000 kg/hr. Its efficiency is from 50% to 70% depending upon the type of fuel used.
Parts of Lancashire Boiler:
It is the outermost part of the Lancashire boiler. It is cylindrical in shape. Other parts of the boiler are present inside this shell.
2) Fire door:
Fire door is used to ignite the fuel inside the boiler which is present in the front end of each fire tube. This fire door has a grate.
The solid fuels are burnt in this grate. It is present in the firebox.
small arch-shaped brickwork is provided at the end of the grate to deflect the flue gases upwards and prevent the entry of burning coal and ashes into the interior part of the fire tube.
Ashpit is used to collect the ash of the fuel after the fuel is burnt.
5) Fire Tube:
Lancashire boiler has two large firetubes through which the hot flue gases flow. These fire tubes are surrounded by water.
6) Brick Work:
The cylindrical shell of the boiler is placed over brickwork which creates several channels for the flow of hot flue gases.
The chimney is used to pass the hot flue gases to the atmosphere after it passes through the bottom channel and side channel.
There are dampers present at the end of each side channel to regulate the airflow to the chimney.
9) Man Hole:
The manhole is provided in this boiler for a man to enter inside the boiler and clean and repair it from inside.
10) Feed Check Valve:
Feed Check Valve is used to feed water into the boiler and stop the water from entering the boiler.
11) Water Level indicator:
It indicates the level or quantity of water in the boiler. Using this indicator water level is checked and feed accordingly.
12) Safety Valve:
It is used to blow off steam when there is excess pressure of steam and prevents the boiler from bursting.
13) Fusible Plug:
It is used when safety valve doesn’t and the pressure of steam exceeds the working pressure. In this condition, the fusible plug fuses and whole steam goes out of the boiler and prevents it from bursting.
14) Blow off Valve:
It is mainly used to remove the sediments or mud if collected at the bottom of the boiler.
15) Steam Stop Valve:
It is used to stop and allow the flow of steam from the boiler to the steam pipe.
It is present before the chimney. The hot flue gases pass through this economizer before going out from the chimney. This economizer takes heat from the flue gases and uses this heat to pre-heat the water which after preheating is fed to the boiler.
17) Super Heater:
It is used to superheat the steam which is generated in the boiler. It increases the temperature of the steam coming from the steam stop valve and this superheated is sent to the required place. This superheater gets heat from the flue gases.
Construction Of Lancashire Boiler:
- Lancashire Boiler consists of a horizontal cylindrical shell filled with water. This boiler has two large fire tubes that are surrounded by water.
- The cylindrical shell is placed inside a brick wall creates several channels for the flow of hot flue gases.
- The fire tubes are slightly conical towards its rear end to increase the velocity of hot flue gases.
- There are dampers at the end of each side channel to regulate the airflow.
- The feed check valve is used to feed water uniformly to the boiler shell.
- An anti priming pipe separates the water from steam which is present at the top of the boiler.
- A manhole is provided at the top and the bottom of the shell to allow a man to enter the boiler and clean it.
- A blow off valve is provided to remove the mud that has settled down. It is also used to empty and clean the boiler.
Working of Lancashire Boiler:
- At first, water is fed uniformly to the boiler shell using the feed pump.
- Before entering into the boiler, the water is preheated using the economizer which gets heat from the flue gases. This economizer increases the efficiency of the boiler.
- After that, solid fuel is entered from the fire door and burnt on the grate which is present at the starting if each fire tube.
- As the solid fuel is burnt, flue gases start traveling in the fire tube.
- There is a small brick arc which stops ashes and burnt coal to enter into the fire tube.
- As the flue gases pass through the fire tubes, these fire tubes start getting heated and the heat is transferred to the water which is surrounding the fire tube
- As the heat is transferred to the water, the water starts to get converting into steam and the steam generated is transferred to the required place using the stop valve.
- Before reaching the stop valve the steam crosses the superheater which superheats the steam before delivering it to the required place.
- After passing through the firetube, the flue gases go to the bottom channel which is created in the brickwork and then the flue gases pass through the side channel.
- As the flue gases pass through the channels in the brickwork, these flue gases come in contact with the boiler shell and the boiler shell gets heated and this heat is transferred to the water inside the boiler shell and the efficiency of boiler is increased.
- channel and transfer heat to the superheater before passing through the chimney.
- The flue gases after passing through side channels transfer the heat to the superheater and then escapes to the environment through the chimney.
Advantages of Lancashire Boiler:
1) Very simple design.
2) Ease of Operation.
3) It can be easily maintained and replaced.
4) It is very cost effective.
Disadvantages of Lancashire Boiler:
1) This boiler requires large area.
2) The steam production rate is high.
3) Much of the available heat is lost through the chimney due to less number of chimney.
4) It has low efficiency.
Applications of Lancashire Boiler:
1 It is commonly used to drive steam turbines.
2 It is also used in marines.
3 It is used in locomotives.
4 It also employed in sugar mills, textile mills etc.