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Cochran Boiler | Main Parts, Working, Features, Advantages & Limitations

Cochran Boiler

  • The Cochran boiler was founded by Cochran & Co. of Annan.
  • It is a vertical multi-tubular boiler and having a number of horizontal fire tubes.
  • It is the modification of simple vertical boiler where the heating surface has been increased by means of a number of fire tubes.
  • The efficiency of this boiler is much better than the simple vertical boiler.

Main Parts of Cochran Boiler

cochran boiler

Fig. Cochran Boiler line Diagram.

1. Shell

  • A shell is the main body of the boiler.
  • They having vertical axis cylindrical drum with hemispherical dome type shell at the top.
  • This hemisphere gives higher volume to increase steam capacity.

2. Grate

  • It is the platform on which the solid fuel is burnt.

3. Combustion chamber

  •  The burning of fuel takes place in the combustion chamber.

4. Fire tubes

  • The fire tubes helps in the exchange of heat from the hot flue gases to the water.

5. Fire hole

  • It is the hole through which fuel is fire inside the furnace.

6. Furnace (Fire box)

  • Furnace is the place where combustion of all the fuel is take place.
  • It lies at the bottom of the boiler.
  • It terms as fire box.

7. Ash pit

  • It is the place where ash of the burning fuel is collected.

8. Chimney

  • The chimney is attached with the smoke box .
  • And it releases smoke into the atmosphere.

9. Fire brick lining

  • It helps in the combustion of the fuel and present in combustion chamber.

10. Man hole

  • It is a hole on the boiler shell for the purpose of either cleaning, inspection and maintenance.

11. Flue pipe

  • It is a small passage which connected with the fire box and combustion chamber.
  • The hot gases enter into the combustion chamber through the flue pipe.

Working of Cochran boiler

  • Fuel is placed at the grate through fire hole.
  • Air comes into the combustion chamber through atmosphere.
  • Fuel is burn through fire hole.
  • Then, the hot flue gases emerge out and start flowing into hemispherical dome shaped combustion chamber.
  • This hot flue gases further moves into the fire pipes.
  • The hot flue gases inside the fire tubes exchange the heat from the hot gases to the water.
  • Due to the exchange of heat, the steam produced. And it rises upward to collect into the upper side of the shell.
  • When the required pressure generated, the flue gases goes to the chimney through fire box where it leaves to the atmosphere.
  • Hence, this process repeats and run continuously.

Features

  • In Cochran boiler, any types of fuel may be used.
  • It gives 70% to 75% of thermal efficiency with coal and oil firing.
  • It is well suitable for small capacity requirement.
  • The ratio of grate area to the heating surface area varies from 10:1 to 20:1.

Specification of the Cochran boiler

  Height 5.75 m
  Efficiency 70 – 75 %
  Shell diameter 2.75 m
  Steam capacity 3500 kg/hr (max. 4000 kg/hr)
  Working pressure 6.5 bar( max. 15 bar)
  Heating surface area 120 m

Advantages

  • It occupies less floor space.
  • Initial cost of boiler is less.
  • It is easy to operate.
  • Low initialization cost.
  • They having higher volume to area ratio.
  • Easy to clean and inspect.
  • It’s easy to transport from one place to another.

Limitations

  • Maintenance and inspection are difficult due to narrow space inside for entering.
  • They having limited pressure range.
  • Steam generation rate is low.
  • Due to it’s vertical design, high room head is required for its installation.

Different types of Mounting used in Cochran boiler

  • The Mountings are those mechanical appliances which are considered essential for operating a boiler smoothly and safety. Which are usually mounted on the surface of a boiler.

The following are the important mountings of a boiler:

            1. Safety valves                                            2. Fusible plug

            3. Pressure gauge                                        4. Water level indicator

                 5. Blow off cock                                            6. Feed check valve

                 7. Steam stop valve

1. Safety valves

  • It is used to prevent explosion due to excessive internal pressure.
  • Safety valves are attached on the chest of the boiler.

Different types of Accessories used in Cochran boiler

1. Economizer

2. Feed pump

3. Super heater

4. Air preheater

https://mechanicalnotes.com/2019/06/11/boiler-definition-classification-parts/

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