cochran boiler(vertical multi tube boiler) detailed explanation.

 Cochran Boiler (Vertical multi-tubes boiler) 

 It is one of the best type of vertical multi-tubular boiler. It is fire tube boiler and used for steam generation at lower rate. 

Specification of cochran boiler

Shell diameter = 2.75 m Height = 5.75 m 

Working pressure = 6.5 bar 

Heating surface area 120 m2 

Steam capacity = 3500 kg/hr (Max. = 4000 kg/hr) 

Efficiency = 70 to 75 % 

Cochran boiler

Characteristics of cochran boiler

It is a vertical, multi tubes, fire tube, internally fired, natural circulation boiler. Construction The boiler consists of a cylindrical shell, hemispherical fire box, fire tubes and chimney. The top of the shell having hemispherical shaped crown as shown in fig.

The hemispherical crown of boiler gives good strength to withstand pressure of steam inside the boiler. The hemispherical shape of furnace can withstand high heat and it is also useful to increase radiant heat transfer. 

The grate is placed at the bottom of furnace and ash pit is located below the grate. The furnace and the combustion chamber are connected by short flue pipe. The wall of the combustion chamber is lined with the fire bricks. 

Working of cochran boiler

The water is supplied to the boiler through feed check valve. The level is adjusted with the help of water level indicator. Coal is added through the fire-hole or door to the grate and burnt. The hot gases produced are collected in the fir box. 

These hot gases enter into horizontal fire tubes. Heat transfer takes place from flue gases passing inside the tubes to water surrounded the tubes. The flue gas coming from the fire tubes enter into smoke box. Finally they discharged to atmosphere through a chimney. 

The ash formed is collected in ash pit. The steam is collected through anti priming pipe on the top of the shell.

Advantages of cochran boiler

1.  cochran boiler is compact and portable boiler therefore minimum floor area is required. 
2.  cochran boiler can be moved and set up readily in different locations.
3.  Any type of fuel can be used(Coal or Oil).
4.  Quick and easy installation.
5.  Initial cost of boiler is less.

Disadvantages of cochran boiler

1. Steam raising capacity is less due to vertical design. 
2. Water along with steam may enter the steam pipe under heavy loads sue to small steam space. 
3. Efficiency is poor in smaller sizes.