Smoke Tube Boilers
Q. Smoke Tube Boilers or cochron boiler diagram.
In these boilers the flue gases pass through the tubes which are surrounded by water in boiler shell. Some of the boilers of these type are being discussed below.
Cochron Boiler :
- It is a fire tube boiler in which the flue gases from the furnace are passed through a number of small tubes surrounded by water as shown in Figure.
- It consists of an external cylindrical shell (CS), crown (Cr) and fire box (F), all being of hemispherical shapes.
- The bottom most portion is ash-pit ( A) and above this is grate (G) on which the coal is burnt in presence of air. Due to the combustion of the fuel, the produced flue gases pass through the number of small smoke tubes (T) via the flue pipe (FP).
- The heat energy of the flue gases is transferred to the surrounding water in the shell. The flue gases from the smoke box (SB) are discharged to the atmosphere through the chimney (C).
- The combustion chamber (CC) is lined up with bricks (B) to reduce the heat losses.
- A door (D) is provided in the smoke box for cleaning the smoke tubes and a manhole (M) is provided at the crown for periodic cleaning and maintenance of the boiler. A mud hold (H) is provided at the bottom most point for draining out the water from the boiler.
- Usually these type of boilers have 160 tubes 6.25 cm diameter each with its shell diameter of 1.8 m and height 4.5 m approximately. These boilers can produce steam upto 3000 kg/hr and working pressures upto 20 bar.