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Elements of Mechanical Engineering
The document summarizes two types of boilers: the Cochran boiler and the Lancashire boiler. The Cochran boiler is a vertical, multi-tube, fire tube boiler that is portable with a small floor area. It has a shell diameter of 2.75m, height of 5.75m, and can produce 3500 kg/hr of steam. The Lancashire boiler is a horizontal, stationary boiler commonly used in industries. It is longer than the Cochran boiler at 7-9m in length and can produce 9000 kg/hr of steam. Both boilers use fire tubes for heat transfer and have similar components like safety valves, but the Lancashire boiler has a larger heating surface area due to its three-pass design
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Elements of Mechanical Engineering
- 1. Elements of Mechanical Engineering COCHRAN BOILER& LANCASHIRE BOILER
- 2. Index: Here _words means hyperlink & cons. Means construction.
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- 4. General It is oneof the best types of vertical multi-tube type boiler. It is fire tube type boiler. It is popular portable boiler. It consist of very small floor area.
- 5. Specifications Shell diameter= 2.75m Height = 5.75m Working pressure = 6.5bar(max = 15bar) Steam capacity = 3500 kg/hr(max = 4000 kg/hr) Heating surface area = 120 m² Efficiency = 70% to 75%
- 6. Characteristics It isvertical. It is portable. It is a fire tube boiler. It’s multi tube boiler. It is internally fired. Solid as well as liquid fuel can be burnt. It has natural circulation. It’s low pressure boiler.
- 7. Construction & Working The boiler consist of a cylindrical shell, hemispherical fire box, fire tubes & chimney. The top of the shell having hemispherical shaped crown. The hemispherical crown of boiler gives good strength to withstand pressure of steam inside the boiler. The grate is placed at the bottom of furnace and ash pit is located below the grate.
- 8. Continue… The furnaceand the combustion chamber are connected by short flue pipe. The wall of the combustion chamber is lined with the fire bricks. The ash pit is located below the grate. TOP
- 9. Working The wateris supplied to the boiler through feed check valve. The coal is introduced to the grate through the fire door. The hot gases produced from furnace enters combustion chamber through flue pipe. This hot gases enters into horizontal fire tubes. Convection heat transfer take place from flue gases passing inside the tubes to water surrounded the tubes. The flue gases coming from of fire tubes enter into smoke box. Finally they discharge to atmosphere through a chimney. The ash formed is collected in ash pit. The steam is collected through antiprimming pipe on top of the shell. TOP
- 10. Mountings Steam pressuregauge Water level indicator Dead weight safety valve Feed check valve Blow-off cock Steam stop valve Man hole Fusible plug Antipriming pipe TOP
- 11. Advantages It iscompact and portable boiler therefore minimum floor area is required. Initial cost of boiler is less. It can be moved and set up readily in different locations. Quick and easy installation. Any type of fuel can be used(coal or oil). TOP
- 12. Disadvantages Steam raisingcapacity is less due to vertical design. Water along with steam may enter the steam pipe under heavy load due to small steam space. Efficiency is poor in smaller size. Difficulty in cleaning and inspection due to vertical design. The boiler require high head room. TOP
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- 14. General It’s simplein design, easy to operate and less operating and maintenance cost. It’s one of the most commonly used stationary boilers. It’s normally used in sugar mills, textile industries where power generation as well as process heating is required. TOP
- 15. Specifications Shell diameter= 2 to 3 m Length of the shell = 7 to 9 m Working pressure = 16 bar Steam capacity = 9000 kg/hr Efficiency = 50% to 70% TOP
- 16. Characteristics It ishorizontal. It is stationary. It is a fire tube boiler. It’s multi tubes boiler. It is internally fired. It has natural circulation. Solid as well as liquid fuel can be burnt. It’s medium pressure boiler. TOP
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- 18. Working The coal isintroduced to the grate through fire holes. The combustion of coal takes place in presence of air which is regulated by damper. The combustion will produce hot gases. TOP
- 19. Mountings Steam pressuregauge Water level indicator Dead weight safety valve Feed check valve Blow-off cock Steam stop valve Low water & high steam safety valve Man hole Fusible plug Antipriming pipe TOP
- 20. Advantages Due tothree passes of flue gases , the heating surface area per unit volume of boiler is large. The fluctuations in load can be easily met by this boiler due to large reservoir. By use of economizer and superheater , maximum heat of flue gases is utilized, so efficiency of boiler can be increased. Easy operation, low maintenance costs, easy to clean and inspect. TOP
- 21. Disadvantages Maximum workingpressure is limited to 16 bars. Due to brick work, more floor area is required. Response of pressure build up is less. The furnace is inside the tubes therefore the grate area is restricted. TOP
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