Lancashire Boiler: Definition, Construction, Working, Uses, Advantages and Disadvantages

In this article, you will learn about Lancashire Boiler Definition, Construction, Specifications, Working, Applications, Advantages and Disadvantages.

Lancashire Boiler: Definition, Construction, Working, Uses, Advantages and Disadvantages

The Lancashire Boiler is basically an internally fired, natural circulation boiler, used to generate low-pressure steam.

Definition of Lancashire Boiler

The Lancashire boiler is a horizontal type and internally fired boiler as the furnaces are used to present inside the boiler. It is a stationary fire tube boiler, invented by William Fairbairn in the year 1844. It is a natural circulation boiler and generates low pressure steam. It has a high thermal efficiency of about 80 to 90%. The size of the boiler is roughly 7-9 meters in length and 2-3 meters in diameter. It mainly works on the principle of the heat exchanger. Through convection, the heat produced from the exhaust gases is transferred to the water. Meanwhile, it has a shell and tube type heat exchanger, in which the water flows through shell and exhaust gases flow through the tubes.

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Components of Lancashire Boilers

  • Steam stop valve: The main purpose of steam stop valve is to prevent and allow the flow of steam from the boiler to the steam pipe.
  • Feed check valve: The main task of a feed check valve is to control the flow of water from the feed pump to the boiler and to stop the backflow of the water from the boiler to the pump.
  • Blow off valve: The main work of blow off valve is to periodically remove the sediments or mud which are collected at the lower part of the boiler while the boiler is in operation.
  • Safety valve: When the pressure of the steam inside the boiler surpasses the working pressure, then the safety valve is used to blow off the steam.
  • Pressure gauge: It is used to measure the pressure of the steam inside the boiler.
  • Manhole: As the name suggests, a manhole is located on the boiler so that a man can enter the boiler for cleaning or maintenance.
  • Water level indicator: It shows the level of water in the boiler. It is situated in front of the boiler. Generally, two water level indicators are used in the boiler.
  • Ash pit: After the burning of fuel, the ash is collected in the ash pit.
  • Fusible plug: It is used to blow out the fire inside the boiler when the water level drops below the unsafe level and prevent an explosion. It also restrains the damage which may happen due to the explosion.
  • Fire door: The main task of fire door is to burn the fuel inside or outside the boiler.
  • Grate: It is used to burn the coal.

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Boiler Mountings and Accessories of Lancashire Boiler

  • Super-heater: It is used to superheat the steam generated in boilers. The main task of super-heater is to increase the temperature of saturated steam without any change in pressure.
  • Air pre-heater: It is used to extract the heat from the flue gases and then transmit it to the atmosphere. It also improves the thermal efficiency of the boiler.
  • Economizer: In steam power plant, it is used as a heat exchanger. Its task is to pre-heat the water(fluid) by taking the remaining heat from the combustion products (flue gases). Installation of economizer is done to increase the efficiency of the boiler.
  • Feed pump: A feed pump is a boiler device which is used to force the feed water at high pressure into boiler.

Construction of Lancashire Boiler

Basically, Lancashire boiler consists a large drum. It has a length which goes up to 9-10m and diameter up to 4-6m. This drum contains two fire tubes of diameter up to 40% of the diameter of the shell. This water drum is situated over the brick works. Lancashire boiler is same as a shell and tube type heat exchanger.

Construction of Lancashire Boilers
Image Via: mech4study

As shown in the above figure, three spaces are created between the drum and the bricks. Two are in the sides and one is at the bottom. Flue gas transmits through the fire tubes and side and bottom space when the boiler is working. More amount of heat is transferred to the water as the water level inside the drum is always above the side channels of flue gases. Moreover, the water drum is not fully filled with water. Usually, the water drum is half filled with water from the lower section of the drum and the upper half space is for generating steam. Mostly, the furnace of this boiler is situated at one end of the fire tubes inside the boiler. The low brick is situated at the grates and which blocks the unburned flue and ash to flow in the fire tubes.

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Working of Lancashire Boiler

For Lancashire boiler, hard fuel is burned at the grate. The water is discharged into the shell with the help of economizer, which increases the temperature of the water. The shell is half filled with water while the fire tube is completely submerged into water. The fuel is charged at grate which creates flue gases. Flue gases passes through the fire tubes from one end to other. 80-90% of heat is transferred to the water by fire tubes while 8-10% of heat is transmitted to water with the help of backward flue gases which passes from the lowest passage. Furthermore, 6-8% of heat is transferred to the water from the remaining flue gases which passes through the side passage.

Working of Lancashire Boilers
Image Via: SlideShare

The wet steam and hot steam are segregated where the steam produced flows to the anti-priming pipe. Additionally, the wet steam is superheated and dry steam is fed to the steam stop valve. As we know, brick is the lower conductor of heat hence it works as a heat insulator. The steam produced is used to operate a turbine which is then used for the generation of electricity.

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Advantages of Lancashire Boiler

  • Operation of this boiler is quite easy.
  • Lancashire boiler can easily meet the load requirement.
  • It consists of high thermal efficiency of about 80-90%.
  • It consumes less electricity compared to other boilers as this boiler is a natural circulation boiler.
  • A large amount of steam can be produced with the help of this boiler.
  • Maintenance of this boiler is less.
  • Inspection and cleaning of this boiler can be easily done.

Disadvantages of Lancashire Boiler

  • Generation of high-pressure steam can’t be done if required.
  • More amount of time is needed to generate steam.
  • Extra floor space is required for this boiler.
  • The area of grate is very small in this boiler as it is located at the inlet of the fire tube, which has small diameter.
  • It contains a leakage issue.

Applications of Lancashire Boiler

  • Lancashire boilers are used for operations in the maritime industry, steam turbines, locomotives and more.
  • They are mostly used in various industries such as tire industry, sugar industry, paper industry and textile industry.

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