ELEMENTS OF MECHANICAL ENGINEERING

COCHRAN BOILER

By Jeet Bhadania15EC003

Index:

• General • Specification• Characteristics• Working• Mounting• Advantage• Disadvantage

COCHRAN BOILER

GENERAL

It is one of 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.

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%

Characteristics It is vertical. It is portable. It is a fire tube boiler. The number of tubes are more. It is internally fired. It has natural circulation. Solid as well as liquid fuel can

be burnt. It is horizontal tube boiler.

Construction 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.

Continue…

The furnace and 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.

Working The water is 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.

Mountings

Steam pressure gauge Water level indicator Dead weight safety valve Feed check valve Blow-off cock Steam stop valve Man hole Fusible plug

Advantages

It is compact 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).

Disadvantages

Steam raising capacity 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.

Any Question…

Thank You