Construction and Working Principle of Lancashire Boiler

Lancashire boiler -

            Lancashire Boiler is a horizontal type and stationary fire tube boiler. Lancashire Boiler is invented by Sir William Fairbairn in 1844. 

Principal of Lancashire boiler -

         Lancashire boiler consists of a horizontal cylindrical shell filled with water. It uses to surround by two large fire tubes. Heat exchanging is the basic working principle of this boiler. It is has a shell and tube type heat exchanging system. Generally, the flue gases pass through the fire tubes and water flows through the shell. By this way, the heat is transfer from flue gases to the water. It is a low pressure, internally fired, natural water circulation boiler. 

Construction of Lancashire boiler -

Lancashire boiler consists of -

1. Cylindrical shell
2. Furnace tubes, bottom flue and side flues
3. Grate
4. Fire bridge
5. Dampers 

• Lancashire boiler consist a large drum This drum consist two fire tube of diameter up to 40% of the diameter of shell.
• The water drum is placed over the bricks works.
• Spaces create between the drum and the bricks are as follows -                                          • first is at bottom   

                    • another two are in sides of boiler.

• Flue gases passes through the fire tubes and side and bottom space. 
• The water level inside the drum is always above the side channels of flue gases, so more heat transfer to the water. 
• The drum is half filled with water and the upper half space for steam. 
• The Furnace is located at one end of the fire tubes inside the boiler. 
• The low brick is situated at the grates  (space where fuel burns) which does not allow to un-burned fuel and ash to flow in fire tubes. 
• The boiler also consist other necessary mountings and accessories like economizer, super heater, safety valve, pressure gauge, water gauge, etc. to perform better.

Working of Lancashire boiler -

• Lancashire boiler consists of a horizontal cylindrical shell filled with water surrounding two large fire tubes.
• The cylindrical shell is placed over a brick work which creates several channels for the flow of hot flue gases.
• Solid fuel is provided by the fire door which then burnt over grate at the front end of each fire tube.
• A small arc shape brick work is provided at the end of the grate to deflect the flue gases upward and prevent the entry of burning coal and ashes into the interior part of the fire tubes.
• The fire tubes are slightly conical at rear end to increase the velocity of hot flue gases.
• When hot flue gases are allowed to pass through the downward channel at the front end of the fire tubes. Now these gases pass through the side channel towards the rear end of the fire tube and finally escape out through the chimney.
• There are dampers at each side channel to regulate the air flow.
• Feed check valve is used to feed the water uniformly to boiler shell.
• Once the boiler is at quickly, water converts into steam by absorbing the heat from the flue gases. This steam is stored at the upper portion of the boiler where anti priming pipe separates the water from steam. Thus the steam stop valve receives the dry steam for various purposes.
• A man hole is provided at the top and bottom of the shell to allow a man to enter into the boiler and clean it.
• A blow off valve is provided to remove the mud that has settled down. It is also used to clean the boiler.