elements of mechanical

1.  NAME: RANA KARAN H
 BRANCH: CHEM. TECH (2ND SEM)
 EN.ROLL NO. : 130990136050
Guided by,
Hussain
Sir…
Prepared
by,
karan
rana…

2.  Characteristics of boiler:
 Horizontal
 Multi-water tube
 Externally fired
 Natural circulation of water
 Forced circulation for air and hot gases
 Solid as well as liquid fuel fired
 Specification:
 Diameter of the Drum 1.22 to 1.83 m
 Length 6.096 to 9.144 m
 Size of the water tubes 7.62 to 10.16 cm
 Size of superheated tubes 3.84 to 5.71 cm
 Maximum Working pressure 40 bar
 Maximum Steam capacity 40,000 kg/hr
 Efficiency 60% to 80%

4. Construction :
 It consists of inclined water tubes a steam and water drum a mud box and
superheater.
 The drum is connected to up take and down take header by short riser
tubes.These headers are connected to a series of inclined water tubes.
 The water tube inclind to the horizontal about 15° or above to bring natural
circulation of water. The hand hole is provided in header in front of each tube
for cleaning and inspections of tubes.
 The Baffles plates are provided in order to make the circulation of hot gases in
sine wave form.
 A dmaper is fitted at back of the boiler to regulate the draught and the furnace is
equipped with chain grate stroker to feed the coal to furnace.
 Soot doors is provided to clean the outside of the water tubes and to remove the
soot. Soot doors are also help to access the interior of the boiler.

5. Working :
 The water is fed into the drum through the feed check valve. Due to gravity water
passes through the short riser tubes header and fills up the inclined water tubes.
 Then Water collects in drum. Initially one half of drum is filled up with water. The
coal is introduced to furnace grate by help of stroker. The coal is fired hot gases
produced is first forced to move upward through passage between tubes.
 The Baffles Plates make flow of hot gases in sine wave as move down and then
upward over the water tubes.
 The damper controls the flow of air into the furnace.Water in the drum come
down through down take header and enter the tubes. They are hitted by hot gases
coming from furnace.
 Due to heating of the water density of water decreases Low density water moves
upward in water tubes. The Water tubes just above furnace is heated
comparitively at a higher temperature than the rest of it.
 Therfore low density water gradually converted into steam in their path and rises
into the drum through the up take header.
 Thus a continuous circulation of water from drum to water tubes and water tubes
to drum is maintained due to density difference of water and gravity,without any
pump.

6.  The steam then enters through the anti-priming pipe and flows in the superheater
tubes where it is further heated an is finally taken out through the main steam
stop valve and supplied to the engine when needed.
 At the lowest point of the header mud collector is provided to remove the mud
particles through a blow down cock.
Advantages :
 The steam generation capacity of the boiler is very high,about 2000 to 40,000
kg/hr
 Replacement of defective tubes is easy.
 The draught losses as compared to othr boilers is minimum.
 It is used in power station for generatin large quantity of steam.
 Boiler is required less space area compared to fire tube boilers and offers greater
operational safety.