Cochran Boiler | Parts, Working, Advantages and Disadvantages

Cochran Boiler – Parts, Working, Advantages, and Disadvantages:

Generally, the Cochran boiler is one of the best types of vertical multi-tubular boiler. It is a fire tube boiler. It is a popular portable boiler. It occupies a very small floor area.

Cochran Boiler
Cochran Boiler

The specification of Cochran boiler are as under :

Shell diameter             = 2.75m (1 to 3m)
Height                           = 5.75 m (2 to 6m)
Working pressure       = 6.5 bar (Maximum = 15 bar)
Steam capacity            = 3500 kg/hr (Maximum = 4000 kg/hr. 20 to 4000 kg/hr)
Heating surface area  = 120 m2 (10 to 25 times grate area)
Efficiency                       = 70% to 75%

Characteristics of the Cochran boiler :

  1. It is vertical.
  2. It is not portable.
  3. It is a fire-tube boiler.
  4. The number of tubes is more.
  5. It is internally fired.
  6. It has natural circulation.
  7. Solid as well as liquid fuel can be burnt.
  8. It is a horizontal tube boiler.

List of Main parts of Cochran Boiler: 

  1. Cylindrical Shell
  2. Firebox
  3. Grate
  4. Ash Pan
  5. Flue Pipe
  6. Combustion chamber
  7. Smoke Chamber
  8. Steam Space

(1) Cylindrical Shell: It consists of a vertical, cylindrical shell. At the bottom of the
shell, a fire-box is provided.

(2) Fire box: The top of the boiler shell, as well as that of the firebox, are hemispherical. It is the special feature of this boiler. These shapes require less material with maximum strength and volume. The firebox consists of Grate.

(3) Grate : It is used as a platform in the furnace. It is provided with a fire door or the hole on one side of the box for adding coal.

(4) Ash Pan: Ash pan or ash pit is provided bellow the grate. The ash pan collects the ashes produced by the burning of coal.

(5) Flue Pipe: The top of firebox carries a short flue pipe through which hot gases pass with considerable velocity to enter the combustion chamber.

(6) Combustion chamber: The combustion chamber mainly consists of horizontal
flue tubes. Fire bricks lining is provided on one side of the combustion chamber. This lining deflects the hot gases coming from the firebox and directs them towards horizontal flue tubes. On the other side of the combustion chamber, a smoke chamber is provided.

(7) Smoke Chamber: The waste gases are collected here and then releases to the
chimney and then to the atmosphere.

(8) Steam Space: The top, hemispherical portion of the boiler is called steam space. It collects the steam generated in the boiler. This portion is fitted with a safety valve provided for the safety of the boiler against excessive steam pressure. The other components provided are stop valve, manhole, etc.

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The following mountings are used with Cochran boiler:

I. Steam pressure gauge - To read steam pressure

2. Water level indicator - To find out the water level in the boiler

3. Dead weight safety valve - For boiler safety

4. Feed check valve - To feed the water in the boiler

5. Blow- off cock - For taking scale and other impurities from the boiler and to empty the boiler when necessary.

6. Steam stop valve - To stop or allow the flow of steam from the boiler

7. Man hole - For periodic inspection and maintenance

8. Fusible Plug - To stop firing when the water level in the boiler is lower than safe limit.

9. Anti-priming pipe - To separate suspended moisture and allow the passage of dry saturated steam through the steam stop valve.

Working of Cochran Boiler:

The water is fed into the boiler through the feed check valve. The level is adjusted with the help of a water level Indicator. Coal is added through the fire-hole to the grate and burnt. The hot gases produced are collected in the fire-box. From the fire-box, the gases pass on to the combustion chamber through the short flue pipe with considerable velocity. The fire brick lining in the combustion chamber deflects the hot gases to pass through the horizontal tubes. From here. the hot gases through smoke-box enter the chimney. The water evaporates and the steam is collected at the top. The steam is taken out for utilization through the stop valve.

Advantages and Disadvantages of Cochran Boiler:

Advantages :
1.  The minimum floor area is required. (That it is a compact boiler.)
2. The cost of construction is low.
3. It can be moved and set up readily in different locations.
4. Boiler has a self-contained furnace. No brickwork setting is necessary.
5. Any type of fuel can be used.

Disadvantages :
1. Steam raising capacity is less due to vertical design.
2. Difficulty in cleaning and inspection due to vertical design.
3. The capacity and pressure are limited.
4. The boiler requires a high headroom.

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Cochran Boiler | Parts, Working, Advantages and Disadvantages Cochran Boiler | Parts, Working, Advantages and Disadvantages Reviewed by Harish on August 02, 2020 Rating: 5

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