Lancashire Boiler – Construction and Working

Lancashire Boiler is a horizontal type and stationary fire tube boiler. Before we go further, let’s know person who invented this boiler. Lancashire Boiler was invented in the year 1844, by William Fairbairn. But his patent was for the method of firing the furnaces alternately. Generally flue gases passes through the fire tube. It is present inside the boiler shell or body and for this reason it is a fire tube boiler. Lancashire Boiler is an internally fired boiler because the furnace uses to present inside the boiler. This boiler generates low pressure steam and it is a natural circulation boiler.

Construction of Lancashire Boiler :

It consists of

• Cylindrical shell
• Furnace tubes, bottom flue and side flues
• Grate
• Fire bridge
• Dampers

Cylindrical shell
It is placed in horizontal position over a brick work. It is partly filled up with water. The water level inside the shell is well above the furnace tubes.

Furnace tubes, bottom flue and side flues:
Two large internal furnace tubes (flue tubes) extend from one end to the other end of the shell. The flues are built-up of ordinary brick lined with fire bricks. One bottom flue and two side flues are formed by brick setting, as shown in the figure.

Grate
The grate is provided at the front end of the main flue tubes. Coal is fed to the grate through the fire hole.

Fire bridge:
A brickwork fire bridge is provided at the end of the grate to prevent the flow of coal and ash particles into the interior of the furnace (flue) tubes. Otherwise the coal and ash particles carried with gases form deposits on the interior of the tubes and prevent the heat transfer to the water.

Dampers:
Dampers is in the form of sliding doors are placed at the end of the side flues to control the flow of gases from side flues to the chimney flue.

Working of Lancashire boiler

In Lancashire boiler fuel is added into the grate of the boiler and burning of this make gases hot. These hot gases start their motion from grate section and enter the fire tube of the boiler. Hot gases enter at the front section of the boiler and leave the boiler from the back and enter the bottom fuel and start moving toward the front section of the boiler. At front section hot gases leave the bottom flue and enter in side flue and move again toward the back of the boiler and enter the main outlet there. There is 85% heat transfer when hot gases are in fire tube and 15% when they are in bottom and side flue. Pressure range of the boiler is about 0.7 MPa to 2 MPa and efficiency is 65 to 70%. Dimension of the boiler depends on the dimension of the shell which is 2 to 3 m is diameter and 6 to 10 m in length.

Advantages of Lancashire Boiler

• Lancashire Boiler is an Economical boiler
• It can be easily operated
• Compactness
• Portability
• Simple design
• Easy construction
• Have low maintenance cost
• High overall efficiency (80% to 85%)
• Steam produce have excellent quality
• Due to the large quantity of water available, it can easily overcome the load fluctuation

Disadvantages Lancashire Boiler

• Corrosion in water legs
• It is difficult to clean inside
• Low steam production rate (9000kg/hr)
• Horizontal structure cover more ground space
• Maintenance of brick work is tedious.
• Have limited grate area because the fire tubes have small diameter.
• It’s a low pressure Boiler maximum limit is only 20 bars

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