SHRI S’AD VIDYA MANDAL INSTITUTE OF TECHNOLOGY,BHARUCH
DEPARTMENT OF MECHANICAL ENGINEERING
By Ashish J. Modi
STEAM BOILER
ASHISH J. MODI @ SVMIT
INTRODUCTION
ƒ Boiler
B il – a device
d i used
d to
t generating
ti steam
t
from water.
ƒ Steam
S
i utilized
is
ili d for
f power generation,
i
f
for
process heating or for space heating.
ƒ According to IBR (Indian Boiler Regulation),
a boiler is a closed pressure vessel with
capacity
it exceeding
di
22.75 litres
lit
used
d for
f
generating steam under pressure.
ASHISH J. MODI @ SVMIT
Essential Qualities
Essential Qualities
1. Should
Sh ld produce
d
maximum
i
steam
t
with
ith
2.
3.
4.
5.
6.
minimum fuel consumption.
Sh ld be
Should
b able
bl to deliver
d li
d i d quantity
desired
i
of steam quickly after starting.
Should be able to meet large load
fluctuation.
Should be light and simple in construction.
Should occupy less space.
Should be easy to maintain and inspect
ASHISH J. MODI @ SVMIT
Essential Qualities
Essential Qualities
7. Joints should
sho ld be accessible for inspection
and should not face the impact of flame
directly.
8. Velocity of water and that of flue gases
should be minimum.
9. Tubes should be sufficiently strong to
resist wear and corrosion.
10. Mud and other deposits should not collect
on heated plates.
11. Should as per regulation given by IBR.
ASHISH J. MODI @ SVMIT
Classification
1. According to Relative Position of Water
and Hot gases:
1. Fire Tube Boilers
2. Water Tube Boilers
2. According to Geometric Orientation:
1. Horizontal Boilers
2. Vertical Boilers
3. According to Location of Furnace:
1 Externally Fired Boilers
1.
2. Internally Fired Boilers
ASHISH J. MODI @ SVMIT
Classification
4. According to Method of Water Circulation
‐ Natural Circulation Boilers: water convection
currents are set up due to temperature
difference. water from steam drum falls under
gravity
i to header
h d where
h
i temperature rises
its
i
and density reduces. So it travels upwards to
steam drum through evaporator
ASHISH J. MODI @ SVMIT
Classification
‐ Forced Circulation Boilers: water is circulated
through
g boiler circuit by
yap
pump.
p Low capacity
p
y
boilers use natural circulation, while only high
pressure‐high capacity boilers use forced
circulation.
circulation
ASHISH J. MODI @ SVMIT
Classification
5. According
Pressure:
to
Magnitude
of
working
1. High Pressure Steam Boilers > 25 bars
e.g. Babcock and Wilcox Boilers
2. Medium Pressure Steam Boilers – 10‐25
5 bars
e.g. Lancashire and Locomotive Boilers
33. Low Pressure Steam Boilers – 3
3.5‐10
5
bars
e.g. Cochran and Cornish Boilers
ASHISH J. MODI @ SVMIT
Classification
6. According to Mobility of Boiler:
1. Stationary Boilers
e.g. Lancashire Boilers,
Babcock and Wilcox Boilers
2. Mobile Boilers
e.g. Locomotive Boilers
ASHISH J. MODI @ SVMIT
Factors affecting the Selection of a boiler
1. Type
yp of steam to be p
produced. i.e. wet,, dry
y
2.
3.
4.
5.
6
6.
7.
and superheated steam.
Steam g
generating
g rate and steam p
pressure
required.
Quality and quantity of fuel and water
available.
Cost of installation and erection.
Cost of operation and maintenance.
Availability of floor space.
space
Probable load factor.
ASHISH J. MODI @ SVMIT
Parts of a Boiler
Parts of a Boiler
1. Cylindrical
C li d i l Shell
Sh ll
2. Grate
3. Fire Hole
4. Fire Box
5. Ash Pan (Ash Pit)
6. Smoke Box (Smoke Chamber)
7. Man Hole
8 Hand Hole
8.
ASHISH J. MODI @ SVMIT
Parts of a Boiler
Parts of a Boiler
9. Mud Box
10. Steam
S
C ll i Pipe
Collecting
Pi
11. Boiler Stays
11
12. Flue and Fire Tube
ASHISH J. MODI @ SVMIT
ASHISH J. MODI @ SVMIT
Simple Vertical Boiler
ASHISH J. MODI @ SVMIT
Simple Vertical Boiler
ASHISH J. MODI @ SVMIT
Advantages and Limitations
Advantages and Limitations
ƒ Compact
C
t and
d requires
i less
l
fl
floor
space.
ƒ Transported easily and not require heavy
ffoundation.
d i
ƒ As the gases move directly towards
chimney, heat transfer efficiency is very
low. Much of the gas with hot gases is
wasted.
t d
ƒ Can produce up to 7 bar and steam rate
around
d 300 kg/hr.
k /h
ASHISH J. MODI @ SVMIT
Cochran Boiler
ASHISH J. MODI @ SVMIT
Cochran Boiler
ASHISH J. MODI @ SVMIT
Advantages Advantages
ƒ The
Th minimum
i i
fl
floor
area is
i required.
i d
ƒ
ƒ
ƒ
ƒ
(compact boiler)
C
Cost
off construction
i is
i low.
l
It can be moved and setup readily in
different locations.
Boiler has self contained furnace. No brick
work setting is necessary.
Any type of fuel can be used.
ASHISH J. MODI @ SVMIT
Disadvantages Disadvantages
ƒ Steam
St
raising
i i capacity
it is
i less
l
d to
due
t vertical
ti l
design.
ƒ Difficulty
iffi l in
i cleaning
l
i and
d inspection
i
i due
d to
vertical design.
ƒ The capacity and pressure are limited.
ƒ The boiler requires high head room.
ASHISH J. MODI @ SVMIT
Lancashire Boiler
ASHISH J. MODI @ SVMIT
Advantages
ƒ Heating
H ti area per unit
it volume
l
i large.
is
l
ƒ Its maintenance is easy.
ƒ Load fluctuation can be easily met by this
boiler due to large reserve capacity for
water.
ƒ By incorporating economizer or and
superheater, the efficiency of the boiler can
be increased.
ASHISH J. MODI @ SVMIT
Limitations
ƒ Occupies
O
i
l
large
fl
floor
space due
d
t brick
to
bi k
work.
ƒ Take
k more time
i
to deliver
d li
steam at required
i d
pressure and rate.
ƒ Grates are inside the flue tubes. So their
area is restricted.
ƒ Maximum pressure is limited to around 15
bar due to shell construction.
ASHISH J. MODI @ SVMIT
Cornish Boiler
ASHISH J. MODI @ SVMIT
Comparison with Lancashire
Comparison with Lancashire
ƒ The
Th parts
t like
lik boiler
b il
shell,
h ll brick
b i k work,
k
chimney flue and grate are similar to
Lancashire boiler.
boiler
ƒ There is only one main flue tube here
i t d off two
instead
t
i Lancashire
in
L
hi boiler.
b il
ƒ The flue gases are first passed to side flues
after
ft the
th main
i flue
fl and
d then
th to
t the
th bottom
b tt
flue. Thus the sides of the shell are heated
more.
more
ASHISH J. MODI @ SVMIT
Locomotive Boiler
ASHISH J. MODI @ SVMIT
Locomotive Boiler
ASHISH J. MODI @ SVMIT
Locomotive Boiler
ASHISH J. MODI @ SVMIT
Advantages
ƒ Large
L
steam
t
generation
ti
rate
t per unit
it
heating surface area.
ƒ Compact
C
and
d portable.
bl
ƒ Can satisfy sudden and fluctuating
demands due to variation of power and
speed.
ASHISH J. MODI @ SVMIT
Disadvantages
ƒ Sediments
S di
t
and
d mud
d particles
ti l
may
accumulate in the narrow water spaces
which may lead to scale formation and
corrosion.
ƒ Difficult
Diffi lt to
t clean
l
some water
t spaces.
ƒ Leakage at tube joints and plates is a
problem.
bl
ASHISH J. MODI @ SVMIT
Babcock and Wilcox Boiler
ASHISH J. MODI @ SVMIT
Babcock and Wilcox Boiler
ASHISH J. MODI @ SVMIT
Advantages
ƒ Capacity
C
it is
i very high
hi h (20,000
(
t 40,000
to
kg/hr).
ƒ Defective
f i tubes
b can easily
il replaced.
l d
ƒ Boiler rests over an iron structure,
independent of brickwork. So it can expand
or contract freely.
ƒ Draught loss (pressure drop of gases) is
much less.
ASHISH J. MODI @ SVMIT
Boiler Mountings
ASHISH J. MODI @ SVMIT
Mountings
Function
1. Steam Pressure Gauge
To read steam pressure
2. Water
W t Level Indicator
L l I di t
T fi d t t l l i b il
To find out water level in boiler
3. Dead weight safety valve For boiler safety
4. Feed check valve
To feed water in a boiler
5. Blow off cock
For taking scale and other impurities from boiler and to empty the boiler when necessary.
necessary
6. Steam stop valve
To stop or allow the flow of steam from boiler.
7. Manhole
For periodic inspection
8. Fusible plug
To stop firing when the water level in the boiler is lower than safe limit.
9. Anti priming pump
To separate suspended moisture and allow passage of dry saturated steam through steam stop valve.
ASHISH J. MODI @ SVMIT
Steam Pressure Gauge
g
ASHISH J. MODI @ SVMIT
Water Level Indicator
ASHISH J. MODI @ SVMIT
Dead Weight Safety Valve
ASHISH J. MODI @ SVMIT
Feed check valve
ASHISH J. MODI @ SVMIT
Blow off cock
ASHISH J. MODI @ SVMIT
Steam stop valve
ASHISH J. MODI @ SVMIT
Fusible Plug
ASHISH J. MODI @ SVMIT