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.
Basic Principle of Lancashire Boiler:
This boiler consists of 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 passes 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. That’s means this boiler uses natural current to flow the water inside the boiler during its operation.
Related: Fire Tube Boiler
Construction of Lancashire Boiler:
Generally this boiler consist a large drum. Its diameter can be up to 4-6m and length can be up to 9-10m. Normally this drum consists of two fire tube and its diameter is up to 40 percent of the diameter of the shell. For this boiler the water drum is placed over the bricks works. Where three spaces are create between the drum and the bricks wall. First one is at bottom and second one is in sides. When boiler is operational, then the flue gases passes through the fire tubes and side and bottom space.
The great thing for this boiler is that, water level inside the drum is always above the side channels of flue gases. For this reason more heat can transfer to the water. But water drum is not completely filled with water. Boiler water drum usually half filled with water form bottom section of drum and the upper half space is for generated steam. Generally the Furnace of this boiler is located at one end of fire tubes which is inside the boiler.
Then low brick is present at the grates and it makes an obstacle to unburned fuel and ash to flow in fire tubes during operation. Lancashire Boiler also consist other necessary mountings and accessories. Those are economizer, safety valve, super heater, water gauge, pressure gauge and some others parts. All are for the better performance of this boiler.
Working of Lancashire Boiler:
For this boiler, hard fuel is burn at the grate. Like water tube boiler, water usually pumped into the shell through the economizer. This operation is performing by a water pump. This process increases the temperature of water before further action. Then the fire tube of this boiler is fully immersed into the water.
Generally hard fuel is fired at the grate. This is the first heating process and it produces flue gases. Then generated flue gases passes through the fire tube. This flue gas can pass from one side to another side, inside the boiler fire tube. Boiler fire tubes can transfer 80 to 90 percent of total heat to the water. Then the backward flue gases passes from the bottom passage of this boiler. By this process, heat from flue gases can transfer another 8 to 10 percent heat to water.
After this process remaining flue gases passes from the side passage of the boiler. It can transfer another 6 to 8 percent of heat to water. Brick wall create those heat transfer channel. Brick wall also work as a heat insulator. There is some damper each side channel to regulate the air flow. When water absorb heat then it become steam. Steam stored at the top section of the shell. Then an anti priming pipe separate the generated steam from the water. Then a steam stop valve received generated steam for various purposes.
Then this steam is transfer to the super heater if it required super heated steam for any work. There is a blow off valve is present at the bottom section of this boiler. By this valve we can clean mud and also drain the water.
Advantage and Disadvantages of Lancashire Boiler:
It’s easy to operate this boiler and it required less maintenance. Manhole is providing with this boiler and for this reason it is easy to clean and inspect inside the boiler. It is one of the most reliable boilers. This boiler can generate large amount of steam and it can easily meet with requirement of steam. This boiler is a natural water circulation boiler. This boiler has high thermal efficiency about 80 to 90 percent.
After all those advantage it has some disadvantage. Because this boiler required more space on floor. It also has leakage problem. Process of steam generation required more time. This boiler cannot generate high pressure steam when you need it.
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