Lancashire boiler works on the principle of the heat exchanger. The heat is a transfer from exhaust gases to the water through convection. It is a natural circulation boiler which uses natural current to flow the water inside the boiler.
It is basically a shell and tube type heat exchanger in which the exhaust gases flow through the tubes and the water flows through shell.
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Parts of Lancashire Boiler
The following are the parts of Lancashire Boiler:
- Water level indicator
- Pressure gauge
- Safety valve
- Steam stop valve
- Feed check valve
- Blow off valve
- Fusible plug
- Fire door
- Ash pit
1. Water Level Indicator
It indicates a level of water in the boiler. It is located in front of the boiler. There are two water level indicators are used in boilers.
2. Pressure Gauge
The pressure gauge is adapted to measure the pressure of the steam inside the boiler. It fixed in front of the boiler.
3. Safety Valve
A safety valve is an important device in the boiler which ensures safety to a boiler from being damaged due to excessive steam pressure.
4. Steam Stop Valve
Its purpose is to prevent and allow the flow of steam from the boiler to the steam pipe.
5. Feed Check Valve
The function of a feed check valve is to control the flow of water from the feed pump to the boiler and to prevent the backflow of the water from the boiler to the pump.
6. Blow off valve
The function of a blow-off valve is to eliminate periodically the sediments deposited at the bottom of the boiler while the boiler is in operation.
7. Man Hole
It is a hole situated on the boiler so that a man can easily enter the boiler for the purpose of cleaning and repairing it.
8. Fusible Plug
The function of the fusible plug is to put-off the fire in the furnace of the boiler when the water levels fall below the unsafe level.
The Grate is a floor that is used to burn coal.
10. Fire Door
It is used to burn the fuel inside or outside the boiler.
11. Ash Pit
The function of the ash pit is to collect fuel ash after burning the fuel.
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Boiler Mountings and Accessories of Lancashire Boiler
The following are the different boiler mountings and accessories of Lancashire Boiler:
- Air pre-heater
- Feed pump
In the economiser, heating the feed water does the recovery of heat in the flue gases. the economiser is placed in the path of the gases. It improves the overall efficiency of the boiler.
2. Air Pre-heater
The air preheater is an accessory that recovers the heat in the exhaust gases by heating the air supplied to the furnace of the boiler. It improves the thermal efficiency of the boiler.
The superheater is an accessory used in superheating steam generated in boilers. Its main purpose is to raise the temperature of saturated steam without any change in pressure.
4. Feed Pump
A feed pump is a boiler accessory required to force the feed water at high pressure into the boiler.
Construction of Lancashire Boiler
This boiler is similar to a shell and tube type heat exchanger. It consists of a large drum of diameter up to 4-6 meter and length up to 9-10 meter. This drum consist two fire tube of diameter up to 40% of the diameter of the shell. The water drum is located over the bricks works.
Three spaces between the drum and the bricks, one is at the bottom and two are insides as shown in figure. Flue gases pass through the fire tubes and side and bottom space.
The water level inside the drum is always above the side channels of the flue gases, so more heat transfer to the water. The drum is filled with water and the upper half-space for steam. A furnace is placed at one end of fire tubes inside the boiler.
The low brick is situated at the grates (space where flue burns) which does not allow to un-burned flue and ash to flow in the fire tubes. The boiler also consists of other necessary mountings and accessories like economiser, superheater, safety valve, pressure gauge, water gauge, etc, to perform boiler.
Working of Lancashire Boiler
Lancashire boiler is a shell and tube type, heat exchanger. The fuel is burned at the grate. The water is pumped into the shell through the economiser which increases the temperature of the water. Now the shell is filled with water. The fire tube is fully immersed in the water. The fuel is charged at the grate produces exhaust gases.
These flue gases first pass through the fire tubes from one end to another. This fire tubes transfer 80% to 90% of the heat to the water. The backward flue gases pass from the bottom passage where it transfers 8-10% heat to water.
The remaining flue gases pass from the side passage where it transfers 6-8% of the heat to the water. The brick is the lower conductor of heat, so work as a heat insulator. The steam produces in drum shell is taken out from the upper side where it flows through superheater if required. So the steam generated is taken by out for process work.
Advantages of Lancashire Boiler
- Cleaning and inspection can be done easily.
- It is more reliable and can generate a large amount of steam.
- It required less maintenance.
- This boiler is a natural circulation boiler so lower electricity consumption than others.
- It can easily operate.
- It can easily meet with the load requirement.
- Lancashire boiler has a high thermal efficiency of about 80-90%.
Disadvantages of Lancashire Boiler
- This boiler required more floor space.
- This boiler has a leakage problem.
- It requires more time to generate steam.
- It cannot generate high-pressure steam if required.
- Grates are situated at the inlet of fire tube, which has a small diameter. So the grate area is small in this boiler.
Application of Lancashire Boiler
- Lancashire boilers are employed to operate steam turbines, locomotives, marines etc.
- The Lancashire boiler used in several industries like paper industry, textile industry, sugar industry, tire industry etc.
As you know Lancashire boiler is a shell and tube type, heat exchanger. Which uses natural current to flow the water inside the boiler. This boiler is more reliable and can create a large amount of steam. You can easily handle this boiler.
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