2. INTRODUCTIONINTRODUCTION
STEAM GENERATOR OR BOILER
A steam generator or boiler is
usually a closed vessel made of steel. Its
function is to transfer the heat produced by
the combustion of fuel to water and
ultimately to generate steam.
3. The steam generated may be supplied :
1.To an external combustion engine, i.e., steam engine
and steam turbines
2.At low pressures for industrial process work in
cotton mills, sugar factories , breweries etc., and
3.For producing hot water, which can be used for
heating installations at much lower pressures
4. Purpose of boilers
• For generating power in steam engines or
steam turbines
• In textile industries for sizing and bleaching
• For heating the buildings in cold weather and
for producing hot water for hot water supply
5. Primary requirements of a boiler
• The water must be contained safely
• The steam must be safely delivered in desired
condition (as regard its pressure,
temperature, quality and required rate)
7. Shell: Consists of one
or more steel plates
bent into a cylindrical
form and riveted or
welded together. The
shell ends are closed
with end plates
8. Furnace:
it is the chamber
formed by the space
above the grate and
below the boiler shell, in
which combustion takes
place.
9. Grate: it is a platform
in the furnace upon
which fuel is burnt
10. BURNER - A device for the
introduction of fuel and air
into a furnace at the desired
velocity.The burner is the
principal device for the firing
of oil and/or gas.
11. Ash Pit
The ash pit is the space where
ashes accumulate under the
fire. The ashes fall through the
fire grate into a (often)
removable box.
12. Mud Ring or Mud Drum
A typically cylindrical shaped
space at the bottom of the water
space. Sediment, mud, and other
impurities gather there.
SAFETY VALVE - A spring
loaded valve that automatically
opens when pressure attains the
valve setting. Used to prevent
excessive pressure from building
up in a boiler.
13. • Pressure Gauge. This
indicates the pressure of
the steam in the boiler.
• Fusible Plug . A fusible plug
operates as a safety valve
when dangerous
temperatures, rather than
dangerous pressures, are
reached in a closed vessel.
14. • Feed Check Valve. The
high pressure feed water
is supplied to the boiler
through this valve. This
valve opens towards the
boiler only and feeds the
water to the boiler.
• Steam Stop Valve.
• It regulates the flow of
steam supply outside.
15. Classification of boilers
• Horizontal, vertical or inclined
• Fire tube and water tube
• Externally fired and internally fired
• Forced circulation and natural circulation
• High pressure and low pressure
• Stationary and portable
• Single tube and multi tube
16. Horizontal, vertical or inclined
• If the axis of the boiler is horizontal, vertical or
inclined then it is called horizontal, vertical or
inclined boiler respectively
17. Fire tube and water tube
• If hot gases are inside the tube and water is
outside the tube, it is called fire-tube boiler.
• Examples: Cochran, Lancashire and
locomotive boilers
• If water is inside the tube and hot gases are
outside the tube, it is called fire-tube boiler.
• Examples: Babcock and Wilcox, Stirling,
Yarrow boiler etc
18. Externally fired and internally fired
• The boiler is known as externally fired if the
fire is outside the shell.
• Examples: Babcock and Wilcox, Stirling
• The boiler is known as internally fired if the
furnace is located inside the boiler shell.
• Examples: Cochran, Lancashire
19. Forced circulation and natural
circulation
• In forced circulation type of boilers, the
circulation of water is done by a forced pump
• Examples: Velox, Lamont, Benson boiler
• In natural circulation type of boilers, circulation
of water in the boiler takes place due to natural
convection currents produced by the
application of heat
• Examples: Lancashire, Babcock and Wilcox
20. High pressure and low pressure
• The boilers which produce steam at pressures
of 80 bar and above are called high pressure
boilers
• Examples: Babcock and Wilcox, Velox,
Lamont, Benson boilers
• The boilers which produce steam at pressure
below 80 bar are called low pressure boilers
• Examples: Cochran, Cornish, Lancashire
and locomotive boilers
21. Stationary and portable
• Stationary boilers are used for power plant-
steam, for central station utility power plants,
for plant process steam etc
• Mobile or portable boilers include locomotive
type, and other small unit for temporary use
at sites
22. Single tube and multi tube
• The fire tube boilers are classified as single
tube or multi-tube boilers, depending upon
whether the fire tube is one or more than one
• Examples of single tube boilers are Cornish
and simple vertical boiler
23. WATER TUBE STEAM BOILER:WATER TUBE STEAM BOILER:
The water is contained inside the tubes(called
water tubes)which are surrounded by flames
and hot gases from outside.
Ex: Babcock and Wilcox boiler, stirling boiler,
la - Mont boiler, yarrow boiler and loeffler
boiler
24. FIRE TUBE BOILER
In fire tube steam boilers, the flames and
hot gases produced by the combustion of
fuel pass through the tubes(called multi
tubes) which are surrounded by water.
The heat is conducted through the walls
of the tube from the hot gases through
the surrounding water.
Ex: Cochran boiler, Lancashire boiler,
Cornish boiler,
25. Comparison of fire tube and water
tube boilers
ParticularsParticulars Fire-tube boilersFire-tube boilers Water-tube boilersWater-tube boilers
Position of water and hotPosition of water and hot
gasesgases
Hot gases inside the tubesHot gases inside the tubes
and water outside theand water outside the
tubestubes
Water inside the tubesWater inside the tubes
and hot gases outside theand hot gases outside the
tubestubes
Mode of firingMode of firing Generally internally firedGenerally internally fired Externally firedExternally fired
Operation pressureOperation pressure Limited to 16 barLimited to 16 bar Can go up to 100 barCan go up to 100 bar
Rate of steam productionRate of steam production LowerLower HigherHigher
SuitabilitySuitability Not suitable for largeNot suitable for large
power plantspower plants
Suitable for large powerSuitable for large power
plantsplants
Risk on burstingRisk on bursting Involves lesser risk ofInvolves lesser risk of
explosion due to lowerexplosion due to lower
pressurepressure
More risk on burstingMore risk on bursting
due to high pressuredue to high pressure
Floor areaFloor area For a given power itFor a given power it
occupies more floor areaoccupies more floor area
For a given power itFor a given power it
occupies less floor areaoccupies less floor area
ConstructionConstruction DifficultDifficult SimpleSimple
26. Cont…
ParticularsParticulars Fire-tube boilersFire-tube boilers Water-tube boilersWater-tube boilers
TransportationTransportation DifficultDifficult SimpleSimple
Shell diameterShell diameter Large for same powerLarge for same power Small for same powerSmall for same power
Chances of explosionChances of explosion LessLess MoreMore
Treatment of waterTreatment of water Not so necessaryNot so necessary More necessaryMore necessary
Accessibility of variousAccessibility of various
partsparts
Various parts not so easilyVarious parts not so easily
accessible for cleaning,accessible for cleaning,
repair and inspectionrepair and inspection
More accessibleMore accessible
Requirement of skillRequirement of skill Require less skill forRequire less skill for
efficient and economicefficient and economic
workingworking
Require more skill andRequire more skill and
careful attentioncareful attention
28. Cochran boiler
• Shell diameter: 2.75 mm
• Height: 5.79 m
• Working pressure: 6.5 bar
• Steam capacity: 3500 kg/hr
• Heating surface: 120 m3
• Efficiency : 75%
29. WORKING OF AN COCHRANWORKING OF AN COCHRAN
BOILERBOILER
Considered to be one of the most efficient
type multi tubular boilers.
Consists of external cylindrical shell and
fire box. The shell and fire box both are
hemispherical.
The fire box and combustion chamber is
connected through a short pipe.
The flue gases from the combustion
chamber flow to the smoke box through a
30. WORKING OF AN COCHRANWORKING OF AN COCHRAN
BOILERBOILER
number of smoke tubes.
The gases from the smoke box pass to the
atmosphere through a chimney
The external diameter of pipe is 62.5mm and
are 165in number.
Manhole is provided for cleaning.
33. Specifications
• Dia . Of shell: 2-3m
• Length of shell: 7-9 m
• Max. working pressure: 16 bar
• Steam capacity: 9000 kg/hr
• Efficiency: 50-70%
34. The boiler consists of a long cylindrical
external shell (1) built of steel plates in
sections riveted together.
It has two large internal flue tubes (2).
A fire grate (3) is also called furnace is
provided at one end of the flue tubes on
which solid fuel is burnt.
At the end of the fire grate there is a brick
arch (5) to deflect the flue gases upwards.
The hot flue gases leaving internal flue
tubes passes through the bottom tube(6).
WORKING OF LANCASHIRE
BOILER
35. These flue gases move to the front of the
boiler where they divide and flow into
side tube (7).
The flue gases then enter the main flue
(9) which leads them to chimney.
The damper (8) is fitted at one side flues
to control the draught and thus regulate
the rate of generation of steam.
A spring loaded safety valve (10) and
stop valve (11) are mounted.
37. Specifications of cornish boiler
• No.of flue tubes: 1
• Diameter of shell: 1.25-1.75m
• Length of the shell: 4-7m
• Pressure of steam: 10.5 bar
• Steam capacity:6500 kg/hr
38. CORNISH BOILERCORNISH BOILER
It is a similar type of Lancashire boiler in
all respects, except there is only one flue
tube in Cornish boiler instead of two in
Lancashire boiler.
The diameter of Cornish boiler is
generally 1m to 2m and its length various
from 5m to 7.5m.
The diameter of flue tube may be 0.6
times that of shell.
40. Specifications of locomotive boiler
• Barrel diameter: 2.095m
• Length of barrel: 5.206m
• No of ordinary tubes:116
• no of superheated tubes: 38
• Working pressure: 14 bar
• Efficiency: 70%
41. • Consists of cylindrical barrel with rectangular
fire box at one end and smoke box at another
end
• Hot gases generated due to burning of coal
are deflected by an arch of fire bricks, so that
walls of the fire box may be heated properly
• The heat of the hot gases is transmitted into
water through the heating surfaces of fire
tubes
43. Specifications of babcock boiler
• Diameter of drum:1.22-1.83m
• Length :6.096-9.144m
• Size of water tubes:7.62-10.16cm
• Working pressure:40 bar
• Steam capacity:40000 kg/hr
• Efficiency:60-80%
44. Cont…
• It consists of a drum connected to a series of
front end and rear end header by short riser
tubes
• To these headers are connected a series of
inclined (150
or more) water tubes
• A hand hole is provided in the header in front
of each tube for cleaning and inspection of
tubes
45. • Stirling boiler
• The Stirling boiler is an early
form of water-tube boiler, used
to generate steam in large land-
based stationary plants.
• Stirling boilers are one of the
larger arrangements for a
water-tube boiler. They consist
of a large brick-built chamber
with a sinuous gas path through
it, passing over near-vertical
water-tubes that zigzag
between multiple steam drums
and mud drums.
