Classification of Steam Boilers based on different factors. Cochran, Babcock Wilcox, Lancashier etc. Accessories of steam boilers like economiser, superheater, steam separator, air preheater. Boiler Mountings like pressure gauges, feed check valve, steam stop valve, safety valves, water gauges, blowdown valves, scum valves, salinometer cocks etc.
2. Classifications
Position Of
Water And
Flue Gases
Position Of
Furnace
Position Of
Axis Of Boiler
Where It Can
Be Used
Source Of
Heat
Circulation Of
Water And
Steam
Pressure
Generated
Nature Of
Draught
Employed
3. Smoke Tube Or Fire Tube
• In these type of boilers the hot gases or the flue gases from the furnace
are passes through the tubes surrounded by the water outside to be
evaporated
• Ex : Cochran, Lancashire, Locomotive boilers etc
Water Tube
• In these boilers the water to be evaporated passes through the tubes
and the gases from the furnaces are passed over the external surface of
he tubes.
• Ex : Babcock-Wilcox, Stirling boilers etc
Position Of Water And Flue Gases
4. Internally Fired Boilers
• In these the furnace is inside the body of the boiler
shell.
• Ex : Lancashire, Locomotive boilers etc
Externally Fired Boilers
• In these the furnace is outside the boiler shell.
• Ex : Babcock-Wilcox, Stirling boilers, Loeffler etc
Position Of Furnace
5. Vertical Boilers
•In which the axis of the boiler shell is in
vertical plane
Horizontal Boilers
•In which the axis of the boiler shell is in
Horizontal plane
Position Of Axis
7. Heat energy due to combustion of solid,
liquid or gaseous fuels.
Hot waste gases or electrical energy or
atomic energy etc
Source Of Heat
8. Natural Circulation
• In case of Natural circulation the circulation is set up by
convection current or by gravity.
•Ex : Babcock-Wilcox boilers
Forced Circulations
• In Forced circulations the circulation is set up for high pressure
steam through pumps.
•Ex : LaMont and Loeffer boilers
Circulation Of Water And Steam
9. Low Pressure Boilers
• The boilers which produces steam less than 20 bar are called
low pressure boilers.
•Ex : Cochran, Lancashire and Locomotive boilers
High Pressure Boilers
• The boilers which produces steam above 20 bar are called high
pressure boilers.
•Ex : Babcock-Wilcox, Stirling
Pressure Generated
10. Natural OR Chimney Draught
• When the fuel is burnt on the surface due to natural
circulation of air, the draught is called as natural or chimney
draught.
Artifical Draught
• If the air is circulated with help of the fan driven by external
sources of power, the draught is called artificial draught.
Nature Of Draught Employed
12. • A vertical boiler is a type of fire-
tube or water-tube boiler where the
boiler barrel is oriented vertically
instead of the more common
horizontal orientation. Vertical boilers
were used for a variety of steam-
powered vehicles and other mobile
machines, including early steam
locomotives.
Simple Vertical Boiler
13. • Vertical design limits its working in
many places.
• Because of the limited grate area
steam production is limited.
• Impurities settle down at the bottom
thus prevent water from heating.
• Boiler tubes must be kept short to
minimize height. As a result, much of
the available heat is lost through the
chimney, as it has too little time to
heat the tubes.
Disadvantages
• low initial cost because of lesser parts.
• Low maintenance cost.
• Simple working.
• Easy to install and replace.
• Occupy small space on ground
• Simple vertical boiler have water level
tolerance
Advantages
Simple Vertical Boiler
14. • Cochran boiler consists of a
cylindrical shell with a dome shaped
top where the space is provided for
steam. The furnace is one piece
construction and is seamless. Its
crown has a hemispherical shape and
thus provides maximum volume of
space.
Cochran Boiler
15. • Steam raising capacity is less due
to vertical design.
• Difficult in cleaning and
inspection due to vertical design.
• The capacity and pressure are
limited.
• The boiler requires high head
room.
Disadvantages
• The minimum floor area is required.
• Cost of construction is low.
• it can be moved and stet up take it to
different location.
• Boiler has self contained furnace . No
brick work setting is neccessary.
• Any type of flue can be used.
Advantages
Cochran Boiler
16. • It is a simple horizontal boiler and
belong from the shell and tube types
of boilers. It has a circular shell
connected to end plates supported by
gusset plates. It has a circular shell
connected to end plates supported by
gusset plates. Lancashire boiler have
two fire tubes whose length is equal
to length of the boiler and diameter of
the fire tube is less than half of the
diameter of the shell.
Lancashire Boiler
17. • Corrosion in water legs.
• It is difficult to clean inside.
• Low steam production rate
(9000kg/hr) .
• Horizontal structure cover more
ground space.
• Maintenance of brick work is tedious.
• Have limited grate area because the
fire tubes have small diameter.
Disadvantages
• Lancashire Boiler is an Economical
boiler.
• It can be easily operated.
• Compactness.
• Portability.
• Simple design .
• Easy construction.
• Have low maintenance cost High
overall efficiency (80% to 85%)
Advantages
Lancashire Boiler
18. • It is a water tube boiler used in steam
power plants. In this, water is
circulated inside the tubes and hot
gases flow over the tubes.
Babcock-WIlcox Boiler
19. • It is less suitable for impure and
sedimentary water, as a small deposit
of scale may cause the overheating
and bursting of tubes. Hence, water
treatment is very essential for water
tube boilers.
• Maintenance cost is high.
Disadvantages
• Steam can be generated at very high
pressures.
• Heating surface is more in comparison
with the space occupied, in the case of
water tube boilers.
• Steam can be raised more quickly than
is possible with a fire tube boiler of
large water capacity. Hence, it can be
more easily used for variation of load.
• The hot gases flow almost at right
angles to the direction of water flow.
Hence maximum amount of heat is
transferred to water.
Advantages
Babcock-WIlcox Boiler
21. • They are two in number but can be
three also, if the boiler has an super
heater fitted inside it. This is a very
important mountings fitted on the
boiler and its proper function is
prerequisite. If it is not maintained
properly, its working is abysmally
affected. Safety valve protects boiler
from an uneven increase in pressure.
It entails to be set up on a desired
value that is safe enough and when
pressure in boiler reaches to that
level, it lifts up and releases the
pressure developing inside the boiler.
It is always set at a pressure which is
3% more than the boiler working
pressure.
Safety Valves
22. • This valve regulates the flow of steam
to the distribution lines from boiler. It
is slowly opened, so as to avoid any
type of water hammering taking place
in the distributing lines and
damaging them. It is a Screw down
non return valve and do not allow
steam to come to the boiler back.
Adjacent to it an auxiliary steam stop
valve is also installed and it is used in
case main Steam stop valve is
damaged due any reason and making
unfit for further use.
Main Steam Stop Valves
23. • Fresh water from hot well tank is
supplied to the boiler with the help of
these valves. These are also SDNR
(Screw down non return valve) type
of valve and have a flow that can only
go in one direction. It avoids
pressurized water inside the boiler to
come out and damage the pump,
pumping the fresh water.
Feed Check Valves
24. • This piece of equipment is used to
measure the level of water inside the
boiler. It is very important to keep an
eye on the level of water inside the
boiler, because if it goes below the
normal level, then it can affect boiler
working. There are two water level
gauges provided in every boiler and
one works as a standby type.
Water Gauges
25. • To measure the pressure of steam that
is being developed inside the
boiler,pressure gauges are used. But
they are not directly connected to
boiler and reason behind this is that,
direct steam can damage this piece of
instrument. So, a coil which cools
down the steam to low levels is used
before this pressure gauge.
Pressure Gauges
26. • These cocks are used to for taking
samples of boiler water for taking
readings related to the presence of
chemical inside the boiler. A cooling
coil is also fitted for the high pressure
boilers.
Salinometer Cocks
27. • This valve is used for purging the
boiler. By purging we mean that, in
course of time at the bottom of boiler
various types of impurities like
corrosion deposits, chemical starts
accumulating. So, it becomes
necessary to remove theses sediments
and hence this process is called as the
purging.
•
Blowdown Valves
28. • Sometimes with feed water, some oil
particles come inside the boiler. Now
these oil particles starts floating at the
top of the water level and this
sometimes cause less heat transfer to
water. A valve called as Scum is used
in order to remove these oily particles
and get rid of this problem creating
stuff.
Scum Valves
30. • An economiser is a device in which
the waste heat of the flue gases is
utilised for heating the feed water.
Economiser
31. • The function of an injector is to feed
water into the boiler. It is commonly
employed for vertical and locomotive
boilers and does not find its
application in large capacity high
pressure boilers. It is also used where
the space is not available for the
installation of a feed pump.
In an injector the water is delivered to
the boiler by steam pressure; the
kinetic energy of steam is used to
increase the pressure and velocity of
the feed water.
Injector
32. • The function of a super heater is to
increase the temperature of the steam
above its saturation point. The super
heater is very important accessory of
a boiler and can be used both on fire-
tube and water-tube boilers. The
small boilers are not commonly
provided with a super heater.
Super Heaters
33. • The steam available from a boiler
may be either wet, dry; or
superheated; but in many cases there
will be loss of heat from it during its
passage through the steam pipe from
the boiler to the
Steam Separator
34. • The function of the air pre-heater is to
increase the temperature of air before
it
enters the furnace. It is generally
placed after the economizer; so the
flue gases pass through the
economizer and then to the air
preheater.
Air Preheater