Laboratory Manual for Basic Mechanical Engineering by Dr. Anil Singh Yadav & Prof. Sachin Kumar Nikam

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q9. In Cochran boiler, maximum steam pressure is limited to
a) 1 bar
b) 50 bars
c) 100 bars
d) 20 bars

Q10. The steam generation capacity of Cochran boiler is
a) 20 kg/hr to 3000 kg/hr
b) 20 kg/hr to 10000 kg/hr
c) 20 kg/hr to 15000 kg/hr
d) 20 kg/hr to 20000 kg/hr

Questions for Viva-Voce

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 124

STinhe LBaanrcaisshirae bPorielceirsioisn simAnilgaurlatro
mtheeasCuorirnngishIbnsotirluemr,ebnut t htoas twmoealsaurrgee
pafnileugceleess caoantndtataioninlorgecqatutheireethdfeirewasnogirnklestoeravdJeorobyf
aocnceu.raItteliys gtoenmeraachlliynicnogn. sIitdeisreudsetdo ibne
ctohnejuinnvcetinotniowniothf WslipillgiaamugFe abilrobcakisrnfoirn
bp1ar8er4cs4isa,eraelatmhnogauudlgeahrfrhomimsepaasautheriengmthewcnaht.srofmoSriuitnmhee
cmorertohsoiodn orfesisftiarnint g stteheel, faunrdnaciess
haalrtdereneadte,ly,psroeciassionto rgerdouucned,smaonkde,
srtaabthileizretdh.an the boiler itself.

Lancashire Boiler

Experiment# 11

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

11 EXPERIMENT NO. 11

Lancashire Boiler

Lancashire Boiler AIM
To study of Lancashire boiler.

APPARATUS
Model of Lancashire boiler.

THEORY
A steam boiler is a closed vessel, strongly constructed of steel, in which
steam is generated from water by the application of heat. The steam
generated is used for producing power and for industrial work and heating
work. The steam boiler is also known as steam generator. The function of
a steam boiler or generator is to convert chemical energy of fuel by
combustion into heat and to transfer this heat to water and thus to produce
steam.

According to A.S.M.E. (American Society of Mechanical Engineers,
U.S.A.) code a boiler is defined as a combination of apparatus for
producing, furnishing or recovering heat together with the apparatus for
transferring the heat so made available to water which could be heated
and vaporised to steam form.

The boilers which produce steam at pressure below 80 bar are called low
pressure boilers. Simple Vertical, Cochran, Cornish, Lancashire,
Locomotive boilers, Babcock and Wilcox etc. are the example of low-
pressure boiler. The boilers which produce steam at pressures of 80 bar
and above are called high pressure boilers. Velox, Lamont, Benson
boilers etc. are the example of high-pressure boiler.

A fire-tube or smoke-tube boiler is one in which the hot products of
combustion (hot gases) flow through the inside of tubes, known as smoke
tubes, and water surrounding the tubes. The fire-tube boiler belongs to the
old class of boilers, but they have still a place of usefulness where the
steam pressure does not exceed about 10 bar and where a moderate
quantity of steam is required. They have the advantage of low cost and
compact design. Their evaporative capacities range from 200 to 3,000 kg
of water per hour. Their thermal efficiencies vary from 65 to 68 per cent
under normal conditions, and smaller size of these are easily portable.
Boilers belonging to this class are: Simple vertical boiler, Vertical boiler
with horizontal smoke tubes (Cochran boiler), Locomotive boiler, and
Scotch marine boiler. Fire-tube boilers are also termed as economical
boilers. These boilers have much less water capacity and so they require
less time to raise steam from cold water. Water-tube boilers have water
inside the tubes and hot gases surrounding the tubes.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 125

Lancashire Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

These boilers are used extensively because they can be built for high
pressures and large evaporative capacities. They are safe, quick steaming,
and flexible in construction and operation. Babcock and Wilcox Water-
tube Boiler is the example of water tube boiler.

LANCASHIRE BOILER

It is stationary fire tube, internally fired, horizontal, natural circulation
boiler. This is a widely used boiler because of its good steaming quality
and its ability to burn coal of inferior quality. These boilers have a
cylindrical shell 2m in diameters and its length varies from 8m to 10m. It
has two large internal flue tube having diameter between 80cm to 100cm
in which the grate is situated. The diameter of the internal flue tubes is
about 0.4 times the diameter of the shell. This boiler is set in a brick work
forming external flue so that the external part of the shell forms part of
the heating surface. This boiler can also be used for power generation at a
moderate steam pressure of 15 bar.

The main features of the Lancashire boiler with its brick work shelling
are shown in Fig. 11.1. The boiler consists of a cylindrical shell and two
big furnace tubes ① pass right through this. One bottom flue ② and two
side flues ③ are formed by the brick setting. Both the flue tubes ①
which carry hot gases lay below the water level as shown in the figure.

The grates are provided at the front end of the main flue tubes ① of the
boiler and the coal is fed to the grates through the fire doors. A low fire
brick bridge is provided at the end of the grate, as shown in the figure, to
prevent the flow of coal and ash particles into the interior of the furnace
tubes. Otherwise, the ash and coal particles carried with gases form
deposits on the interior of the tubes ① and prevent the heat transfer to the
water. The fire brick bridge also helps in deflecting the hot gases upward
to provide better heat transfer.

The hot gases leaving the grate pass upto the back end of the tubes ① and
then in the downward direction. They move through the bottom flue ② to
the front of the boiler where they are divided into two and pass to the side
flues ③ as shown in the figure. The flue passages ③ are connected to a
chamber and then to the chimney. Then they move along the two-side
flues ③ and come to the chimney as shown in the figure. Finally, the
water is converted into steam and collected in the steam space in the shell
and it is then taken out through the steam stop valve for use.

With the help of this arrangement of the flow passages of the gases, the
bottom of the shell is first heated and then its sides. The heat is
transferred to the water through surfaces of the two flue tubes (which
remain in water) ① and bottom part ② and sides ③ of the main shell.
This arrangement increases the heating surface to a large extent. The
furnace tubes ① of the boiler form the most important heat transferring
surface, as about 85 per cent of the useful heat transferred is through
these surfaces.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 126

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)Figure 11.1 Lancashire Boiler

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 127

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

The balance of about 15 per cent of heat is transferred through the part of
the shell exposed to the hot gases in the bottom ② and the side flues ③.

Dampers in the form of sliding doors are placed at the end of side flues to
control the flow of gases. This regulates the combustion rate as well as
steam generation rate. These dampers are operated by chains passing over
a pulley at the front of the boiler.

The special features of Lancashire boilers are:

Lancashire Boiler • Its heating surface area per unit volume of the boiler is
considerably large.

• Its maintenance is easy.
• The availability of steam is high and maintenance costs are low. It

is a reliable steam generator.

• It is highly suitable for process industries.

• Due to large water and steam capacity it is not subjected to severe
priming and it stands well against sudden heavy demand for
considerable time without appreciable pressure drop.

• It is suitable where a large reserve of hot water is needed. Load
fluctuations can be easily met by this boiler due to the large
reserve capacity.

• Superheater and economizer can be easily incorporated into the
system; therefore, overall efficiency of the boiler can be
considerably increased (80-85%).

Particulars of Lancashire boiler are as follows:

Diameter of boiler shell 2 meter to 3 metre
Height of boiler shell 6 metre to 10 metre
Diameter of internal fire tube 0.8 meter to 01 meter
Steam generation capacity upto 8500 kg/hr
Pressure of steam 20 bars (general range is
from 7 to 15 bar)
Total heating surface area about 24 to 30 times the
great area
Efficiency 65% without economiser and
75% with economiser

The disadvantages of Lancashire boiler are:

• Due to shell construction the maximum working pressure is
limited to about 20 bar.

• More floor area is required due to brick work setting.

• Cracks in setting, due to large temperature difference inside and
outside, cause leakages.

• The grate area is restricted as the furnace is inside the tubes.
• For developing pressures these boilers take more time due to large

water capacity.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 128

Lancashire Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Mountings and Accessories

This boiler is fitted with usual mountings. The pressure gauge and water
level indicator are provided at the front whereas steam stop valve, safety
valve, low-water and high steam safety valve and manhole are provided
on the top of the shell. The blow-off cock is situated beneath the front
portion of the boiler shell for the removal of sediments and mud. It is also
used to empty the water in the boiler whenever required for inspection.
The fusible plugs are mounted on the top of the main flues just over the
grates as shown in the figure to prevent the overheating of boiler tubes by
extinguishing the fire when the water level falls below particular level. A
low water level alarm is usually mounted in the boiler to give a warning
in case the water level going below the precast value. The low water and
high steam alarm give an audio signal for low water level and high steam
pressure. A feed check valve with a feed pipe is fitted on the front-end
plate. The feed pipe projecting into the boiler is perforated so that the
water is uniformly distributed into the shell.

This boiler is fitted with usual accessories. The superheater is placed at
the end of the main flue tubes. The hot gases before entering the bottom
flue are passed over the superheater tubes as shown in the figure and the
steam drawn through the steam stop-valve is passed through the
superheater. The steam passing through the superheater absorbs heat from
hot gases and becomes superheated. The economizer is placed at the end
of side flues before exhausting the hot gases to the chimney. The water
before being fed into the boiler through the feed check valve is passed
through the economizer. The feed water is heated by absorbing the heat
from the exhaust gases, thus leading to better boiler efficiency Generally,
a chimney is used to provide the draught.

CORNISH BOILER

The Cornish boiler is very similar to a Lancashire boiler. It is also a
horizontal, fire tube, internally fired, natural circulation, stationary boiler.
However, it differs from a Lancashire boiler in two respects.

1. It has only one flue tube.
2. It is small in size.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 129

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

REVIEW QUESTIONS
Q1. Draw a neat sketch of Lancashire boiler.
A1.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 130

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q2. What type of boiler is Lancashire boiler?
Q3. What is the thermal efficiency of Lancashire boiler?
Q4. What are the basic specifications of Lancashire boiler?
Q5. What are the special features of Lancashire boilers?
Q6. What are the disadvantages of Lancashire boiler?
Q7. What type of boiler is Cornish boiler?
Q8. What is the main difference between Lancashire and Cornish
boiler?
Q9. What is the function of the superheater?
Q10. What is the function of the economiser?

WRITE YOUR ANSWERS HERE

Questions for Viva-Voce ……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

…………………………………………………………………………….

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 131

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 132

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

MULTIPLE CHOICE QUESTIONS (✔)
Q1. Which of the following is a low-pressure boiler?

a) Benson
b) Velox
c) Lamont
d) Lancashire boiler

Q2. Lancashire boiler is a
a) Stationary fire tube boiler
b) Internally fire tube boiler
c) Horizontal boiler
d) All of the above

Q3. The diameter of internal flue tubes of a Lancashire boiler is
about….... that of its shell
a) One-fourth
b) One-third
c) Two-fifth
d) One-half

Q4. The number of fire tubes in Lancashire boiler is........
a) Zero
b) One
c) Two
d) Four

Q5. Lancashire boiler is of........
a) Stationary fire tube-type
b) Horizontal type
c) Natural circulation type
d) All of the above

Q6. The length of Lancashire boiler varies from
a) 5 to 6 m
b) 6 to 7 m
c) 6 to 10 m
d) 9 to 10 m

Q7. The internal flue tubes of a Lancashire boiler are reduced in
diameter at the back to provide access to the lower part of the
boiler.
a) TRUE
b) FALSE

Q8. The number of fire tubes in Cornish boiler is........
a) Zero
b) One
c) Two

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 133

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q9. Lancashire boiler is used where working pressure and power
required are
a) Low
b) Moderate
c) High
d) None of this

Q10. The cylindrical shell of a Lancashire boiler has diameter from
a) 1 to 2 m
Questions for Viva-Voce b) 1.25 to 2.25 m
c) 1.5 to 2.5 m
d) 2 to 3 m

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 134

SAinleocoBmaor tivise baoilePrreisciasidoenvicAentghualtairs
museeadsutroingcreaIntestrsutemaemnt frotom wmaetaesrurbey
apunisegicnleegs aanhtdeatato loreecnqaeutreigreythd.e waTnohgriklse orivsJeorbya
ahcocruirzaotenltyaltodrmumachainxiins,g.mIut litsi-tuusbeudlainr,
cnoantjuurnacltiocnirwcuitlhatsiolinp, gaaurtgieficbilaolckdsrfaofrt,
bpfaroerrcsciesaderecaimnrcgauudlleaartfiroomnm,eamasuehdrieigmuhmecnhtp.rroemsSsiuuinrmee,
csoorlriodsifounel frierseidstafnirte tsutbeeel,boialnerd thiast
hhaarsdeneadn, pinretecrisniaoln fgirroeundf,urnaancde.
sLtaobciolimzeodt.ive engine has been used in
the railway over long period of time.
Locomotive boiler has high steam
generation rate and is portable. It is
also used in the marine sector.

Locomotive Boiler

Experiment# 12

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

12 EXPERIMENT NO. 12

Locomotive Boiler

Locomotive Boiler AIM
To Study of Locomotive Boiler.

APPARATUS
Model of Locomotive Boiler.

THEORY
A steam boiler is a closed vessel, strongly constructed of steel, in which
steam is generated from water by the application of heat. The steam
generated is used for producing power and for industrial work and heating
work. The steam boiler is also known as steam generator. The function of
a steam boiler or generator is to convert chemical energy of fuel by
combustion into heat and to transfer this heat to water and thus to produce
steam.

According to A.S.M.E. (American Society of Mechanical Engineers,
U.S.A.) code a boiler is defined as a combination of apparatus for
producing, furnishing or recovering heat together with the apparatus for
transferring the heat so made available to water which could be heated
and vaporised to steam form.

The boilers which produce steam at pressure below 80 bar are called low
pressure boilers. Simple Vertical, Cochran, Cornish, Lancashire,
Locomotive boilers, Babcock and Wilcox etc. are the example of low-
pressure boiler. The boilers which produce steam at pressures of 80 bar
and above are called high pressure boilers. Velox, Lamont, Benson
boilers etc. are the example of high-pressure boiler.

A fire-tube or smoke-tube boiler is one in which the hot products of
combustion (hot gases) flow through the inside of tubes, known as smoke
tubes, and water surrounding the tubes. The fire-tube boiler belongs to the
old class of boilers, but they have still a place of usefulness where the
steam pressure does not exceed about 10 bar and where a moderate
quantity of steam is required. They have the advantage of low cost and
compact design. Their evaporative capacities range from 200 to 3,000 kg
of water per hour. Their thermal efficiencies vary from 65 to 68 per cent
under normal conditions, and smaller size of these are easily portable.
Boilers belonging to this class are: Simple vertical boiler, Vertical boiler
with horizontal smoke tubes (Cochran boiler), Locomotive boiler, and
Scotch marine boiler. Fire-tube boilers are also termed as economical
boilers. These boilers have much less water capacity and so they require
less time to raise steam from cold water. Water-tube boilers have water
inside the tubes and hot gases surrounding the tubes.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 135

Locomotive Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

These boilers are used extensively because they can be built for high
pressures and large evaporative capacities. They are safe, quick steaming,
and flexible in construction and operation. Babcock and Wilcox Water-
tube Boiler is the example of water tube boiler.

LOCOMOTIVE BOILER

It is horizontal multi-tubular, fire tube, induced draught, internally fired,
medium pressure, mobile boiler. The Locomotive boiler generates steam
at a pressure of about 25 bar with a steam rate of 60-70 kg/h per square
metre of the heating surface. This steam rate is quite high and thus it is
mostly used on locomotives for generating steam to drive a steam engine
train. It has very short chimney and is used in railways.

The locomotive boiler shown in Fig. 12.1 comprises the followings:

1. Multi tubular barrel containing an envelope of water in which are
immersed fire tubes.

2. Fire box which has more or less flat sides. This forms a combined
grate and combustion chamber. Grate is a platform in the
combustion chamber upon which fuel is burnt. The grate generally
consists of iron bars which are spaced apart so that air required for
combustion can pass through them.

3. Smoke box equipped with a very short chimney.

The coal, introduced into the fire box through the fire hole, is burnt on the
grate which slopes downwards towards the front.

On the shell or dome are fitted the mountings such as safety valve, stop
valve, pressure gauge and water level etc. The boiler is also provided with
a manhole for cleaning purposes and a large door for excess to the smoke
box and tubes for cleaning. The height of the chimney has to be less so
that when the locomotive is passing through a tunnel or under a bridge,
the chimney does not strike against them. Moreover, a high chimney is
likely to create unbalancing.

It consists of a horizontal steel cylindrical shell with internal firebox at
one end and smoke box at the other end. The fire box is rectangular in
shape and made of steel. It has inclined grate. An ash pit and inclined
brick arch to divert the flue gases. Similarly, the inclined brick arch also
deflects the flue gases thereby delay the entrance to the flue tubes until
the combustion of coal gets completed in the furnace. The boiler shell
contains large number of horizontal tubes through which flue gases pass
from one end to another end. The boiler shell has two sizes of the tubes;
usually the bottom one 148 to 160 tubes of 4.75 cm diameter and upper
one 21 to 24 tubes of 13 cm diameter are fitted. The large diameter tubes
accommodate superheater tubes which tries to superheat the steam.

The steam is collected from the highest point of the boiler, usually in a
dome. The flow of steam through outlet pipe is regulated by means of a
rod connected by a wheel in the driver's cabin.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 136

Locomotive Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)
Figure 12.1 Locomotive Boiler
Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 137

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

This steam is then passed through the superheater with the help of header
and from where superheated steam is taken out. This superheated steam is
supplied to run the steam engine.

It is not possible to provide high chimney to exhaust the flue gases to the
atmosphere as these boilers are running from one place to the other at a
high speed, in which high chimney may cause vibrations. Hence artificial
induced draught is used in these boilers. This is achieved by supplying
exhaust steam from steam engine to the smoke box through blast pipe.
Thus, moves out speedily through the chimney and carries the flue gases.
This produces vacuum in the smoke box. The air is drawn in the furnace
due to this vacuum, so hot gases flow towards the smoke box. A large
door at the front end of the smoke box is provided which can be opened
for cleaning the flue tubes and smoke box.

Locomotive Boiler Because of low chimney, artificial draught has to be created to drive out
the burnt gases. The draught is accomplished by the following methods:

• Motion of locomotive on rails.

• Periodic rush of spent up steam from the engine cylinder into the
fire box. The vacuum thus created sucks the hot gases and helps
their discharge to atmosphere.

• A blower which is run by steam supplied directly by the boiler.
The blower is operated only when supply of steam to the engine is
cut off.

High draught thus produced increases the coal consumption and the steam
evaporation rate. The ash of coal burnt on the grate falls into ash pit from
where it can be removed at regular intervals.

The locomotive boiler is so designed that it is capable of meeting the
sudden and fluctuating demands of steam which may be imposed because
of variation of power and speed. In addition to railways, road rollers and
haulage engines, the locomotive boilers have been used in agricultural
fields, saw mill plants, and stationary power service where semi-
portability is
desired.

The important dimensions and specifications of the locomotive boilers
which are being made at Chitranjan are as follows:

Length and diameter of barrel 5.203 m and 2.095 m
Size and number of super heater tubes 14 cm and 38
Size and number of flue tubes 5.72 cm 116
Working pressure and capacity 14 bar and 9000
kg/hr
Heating surface and grate area 271 m2 and 4.2 m2

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 138

Locomotive Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Advantages: The Locomotive boilers are very popular because of:
1. Large rate of evaporation (55 to 70 kg/sec) per square metre of
heating surface. This aspect however tends to produce wet steam
and loss in efficiency.
2. Freedom from brickwork, chimney and special foundations and
this reduces the cost of installation.
3. Reasonable low cost and compactness makes it ideal for a
portable unit. The unit can be easily moved and set up readily in
different locations.
4. It is very compact boiler.
5. Large quantity of steam generation is needed so that more number
of small and large diameter tubes are provided to increase heating
surface area.
6. High quality of steam is readily available with this boiler as
superheater is installed in the boiler flue tubes.

Disadvantages: The Locomotive boilers is, however, incapable of
meeting very high overloads because of the danger of being damaged due
to overheating. Other shortcomings are:

1. maximum steam pressure is limited to 20 bar.
2. leakage occurs frequently at the places where the tubes join the

plates.
3. large flat surface needs bracing.
4. accumulation of sediments and mud particles in the water legs is

liable to cause corrosion and scale formation. To safeguard
against this, good feed water has to be supplied to the boiler.

The various mountings are provided on the boiler to provide safety. These
are pressure gauge, water level indicator, steam stop valve, fusible plug,
blow off cock, high steam and low water safety valve, feed check valve
and man hole. The following necessary mountings provided for safe and
easy working of the boiler as an essential component:

Feed Check Valve
It is provided in the front side of driver's cabin for supply of feed water
from the reservoir and checks the reverse flow of water from the shell to
reservoir. It is non-return flow control type valve.

Water level indicator
The water level indicator is fitted outside the boiler shell which indicates
the level of water inside the boiler with the help of glass tube. It helps to
maintain a particular level of water inside the boiler otherwise
overheating may take place which in turn may burn out the tubes. They
are two in numbers in a boiler.

Pressure Gauge
It is fitted on top of the boiler shell and indicates the pressure of steam
inside the boiler when boiler is working.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 139

Locomotive Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Safety Valve
The safety valve is fitted on top of the crown of the boiler shell. The
function of safety valve is to maintain a desired pressure in the boiler
shell. If the pressure in the boiler shell increases then extra steam is
released to atmosphere through opening of safety valve.

Steam stop valve
The steam stop valve is fitted upper side of the boiler shell in the steam
space. The stop valve is used for regulating the supply of generated steam
in the boiler shell. It is used to regulate the superheated steam available
from superheater. The steam is used for running the steam engine and
also for creating artificial draught in the smoke chamber.

Fusible plug
The fusible plug is mounted on the boiler shell above the furnace and
below the water level in the shell. This plug under normal condition is
immersed in water in the boiler which keeps the temperature of fusible
metal in the fusible plug below its melting point. When the water level in
the shell falls below the fusible plug level, the fusible metal of the fusible
plug melts by the heat of the flue gases in the furnace. Thus, the plug
melts and drops cut and high-pressure steam/water rushes out to the
furnace and puts off the fire in the furnace. Thus, boiler is protected from
overheating and mishappening.

Blow off cock
Blow off cock is fitted at the bottom most position of the water level in
the shell. During annual maintenance and also in other special occasions,
it is necessary to empty the boiler in order to clean, inspect and repair
internally by blowing off the water and other sediments from boiler.

Man hole
A man hole usually elliptical or oval shaped and is provided at the top of
the boiler shell. The man hole is provided for the entry of person for
repair, cleaning and inspection purposes during annual maintenance. The
man hole and other opening are made steam tight with the help of
asbestos sheet or asbestos board, which are used as a packing material
between shell and manhole. Oval shaped manhole is usually 40cm by
30cm in sizes.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 140

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

REVIEW QUESTIONS
Q1. Draw a neat sketch of Locomotive Boiler.
A1.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 141

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q2. What type of boiler is Locomotive Boiler?
Q3. Why there is no chimney in Locomotive boiler?
Q4. Why fire grate is inclined in Locomotive boiler?
Q5. What are the advantages of Locomotive boiler?

WRITE YOUR ANSWERS HERE
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 142

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

MULTIPLE CHOICE QUESTIONS (✔)

Q1. Which of the following boiler is best suited to meet the fluctuating
demand of steam
a) Locomotive boiler
b) Lancashire boiler
c) Cornish boiler
d) Babcock and wilcox boiler

Q2. In locomotive boiler, maximum steam pressure is limited to.
a) 1 kg/cm2
b) 5 kg/cm2
c) 10 kg/cm2
d) 18 kg/cm2

Q3. Locomotive boiler is a following type
a) Multitubutar
b) Horizontal
c) Internally fired
d) All of the above

Q4. The shell diameter and length of locomotive boiler are
a) 1.5 m,4 m
b) 1.5 m,6 m
c) 1 m,4 m
d) 2 m,4 m

Q5. The draught in locomotive boilers is produced by a
a) Chimney
b) Centrifugal fan
c) Steam jet
d) All of the above

Q6. Locomotive type boiler is a
a) Horizontal multitubular water tube boiler
b) Water wall enclosed furnace type
c) Vertical tubular fire tube type
d) Horizontal multitubular fire tube boiler

Q7. Locomotive boiler has
a) 137 fire tubes and 44 superheated tubes
b) 147 fire tubes and 34 superheated tubes
c) 157 fire tubes and 24 superheated tubes
d) 167 fire tubes and 14 superheated tubes

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 143

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q8. The fire tubes in a Locomotive boiler has …….diameter
a) 4.75 mm
b) 5.47 mm
c) 7.45 mm
d) 47.5 mm

Questions for Viva-Voce Q9. The diameter of superheated tubes in a locomotive boiler is
a) 13 mm
b) 31 mm
c) 130 mm
d) 230 mm

Q10. The length of shell of a Locomotive boiler is
a) 1m
b) 2m
c) 3m
d) 4m

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 144

SIinne186B7a,r PrisoviadenPcre,ciRsiohnodeAInsglualnadr,
mreesaisduernintsg SItnepsthruemn enWt ilctoox manedasuhreis
papniaegcrletenseraantdGtaeoorlogreceqauteHireethdremwaannogrklBe aobrvcJeoorcbyk
apcactuernatteeldy ttohemaBchaibncinogc.kIt &is uWseidlcionx
cNoonnju-nEcxtipolnoswivieth Bsliopilegra,ugwe hbilcohcksufsoerd
bpwarearcstiesarerefaimlnlgeadudleatrfurobmmeesaasaunhridegmhdecneht-.nroumcSlieuianmtee
cboorirloinsigonto greenseisrtaatnet stesatemel,moraendsafeilsy
htahradneneidt,herpruencidseiorn-firegrorundfi,re-taunbde
sbtaobilielirzse.d. The boilers more safely
generated higher pressure steam and
was more efficient (as an energy to
steam converter) than existing
designs.

Babcock and
Wilcox Boiler

Experiment# 13

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

13 EXPERIMENT NO. 13

Babcock and Wilcox Boiler

Babcock and Wilcox Boiler AIM
To Study of Babcock and Wilcox Boiler.

APPARATUS
Model of Babcock and Wilcox Boiler.

THEORY
A steam boiler is a closed vessel, strongly constructed of steel, in which
steam is generated from water by the application of heat. The steam
generated is used for producing power and for industrial work and heating
work. The steam boiler is also known as steam generator. The function of
a steam boiler or generator is to convert chemical energy of fuel by
combustion into heat and to transfer this heat to water and thus to produce
steam.

According to A.S.M.E. (American Society of Mechanical Engineers,
U.S.A.) code a boiler is defined as a combination of apparatus for
producing, furnishing or recovering heat together with the apparatus for
transferring the heat so made available to water which could be heated
and vaporised to steam form.

The boilers which produce steam at pressure below 80 bar are called low
pressure boilers. Simple Vertical, Cochran, Cornish, Lancashire,
Locomotive boilers, Babcock and Wilcox etc. are the example of low-
pressure boiler. The boilers which produce steam at pressures of 80 bar
and above are called high pressure boilers. Velox, Lamont, Benson
boilers etc. are the example of high-pressure boiler.

A fire-tube or smoke-tube boiler is one in which the hot products of
combustion (hot gases) flow through the inside of tubes, known as smoke
tubes, and water surrounding the tubes. The fire-tube boiler belongs to the
old class of boilers, but they have still a place of usefulness where the
steam pressure does not exceed about 10 bar and where a moderate
quantity of steam is required. They have the advantage of low cost and
compact design. Their evaporative capacities range from 200 to 3,000 kg
of water per hour. Their thermal efficiencies vary from 65 to 68 per cent
under normal conditions, and smaller size of these are easily portable.
Boilers belonging to this class are: Simple vertical boiler, Vertical boiler
with horizontal smoke tubes (Cochran boiler), Locomotive boiler, and
Scotch marine boiler. Fire-tube boilers are also termed as economical
boilers. These boilers have much less water capacity and so they require
less time to raise steam from cold water. Water-tube boilers have water
inside the tubes and hot gases surrounding the tubes.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 145

Babcock and Wilcox Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

These boilers are used extensively because they can be built for high
pressures and large evaporative capacities. They are safe, quick steaming,
and flexible in construction and operation. Babcock and Wilcox Water-
tube Boiler is the example of water tube boiler.

BABCOCK AND WILCOX BOILER

This is a horizontal, externally fired, water tube, natural circulation type
of stationary boiler.

The salient aspects of the constructional features of the Babcock and
Wilcox boiler have been shown in Fig. 13.1.

1) It consists of a welded steel high pressure drum mounted at the
top. From each end of drum connections are made with the uptake
header and a down take header. The headers are joined to each
other by a large number of tubes which are kept inclined at an
angle of about 15° to the horizontal. The water tubes are straight,
solid drawn steel tubes about 10 cm in diameter and are expanded
into the bored holes of the headers. Due to serpentine (sinusoidal)
form of headers, the tubes are staggered and this exposes the
complete heating surface to flue gases.

2) The furnace is arranged below the uptake header. The unit has a
grate for fuel burning, provided with a chain gate stoker. The coal
is fed to the chain gate stoker through the fire door. The chain
speed is so adjusted that by the time coal reaches the other end of
the grate, its combustion has been complete. The residual ash falls
into the ashpit.

3) Baffles are provided across the water tubes to act as deflectors to
the flue gases and to provide them with gas passes.

4) At the bottom of the rear header is the mud box. The foreign
matter held in suspension in water gets collected in it and can be
blown off from time to time. The access to the interior of boiler is
provided by the doors. This is necessary to clean the tubes and
remove the soot. The draught is regulated by a damper which is
provided in the back chamber.

5) For getting the superheated steam, the unit is fitted with
superheater tubes which are arranged in the combustion chamber
above the water tubes.

6) Vents are also provided for mountings and accessories such as
safety valve, pressure gauge, water level indicator, fusible plug
and feed check valve etc.

7) The entire assembly of water tubes is hung along with the drum
from steel girder frame by steel rods called slings in a room made
of masonry brick lined with fire bricks.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 146

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)Figure 13.1 Babcock and Wilcox Boiler

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 147

Babcock and Wilcox Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

The boiler drum shell is filled with water through feed valve and a
constant water level is maintained upto about 2/3rd part in the shell. The
water from the drum flows through inclined tubes via downtake header
and then goes back into the shell in the form of water and steam via
uptake header. Obviously, the circulation of water is maintained by
convective currents. The hottest water and steam rise from the tubes to
the uptake header and then through riser enter the boiler drum. The steam
vapours escape through water to the upper half of the drum. The cold-
water flows from the drum to the rear header and that completes the water
circuit.

The hot combustion gases produced by burning fuel on the grate rise
upwards up to the water drum and then downwards. They again move
upwards and downwards between the baffles. Baffle plates make the hot
gases move in such a way that a longer contact time is maintained
between hot gases and inclined water tubes. During their travel, the gases
give their heat to water and steam is formed. Finally, the hot gases escape
to chimney through the smoke chamber.

The steam collected in the water drum is next led to the superheater tubes
via antipriming pipe. Since the superheater tubes are exposed to hot
gases, the steam passing through them gets superheated. When steam is
raised from cold boiler, the superheater should be flooded (filled with
water) to avoid its burning. The superheated steam is finally taken out
through the stop valve and supplied to the engine when needed.

Capacity and Utility: Evaporative capacity of such boiler ranges from
20,000 to 40,000 kg/hr and operating pressures from 11.5 to 17.5 bar are
quite common. The steam from such boilers is primarily used to run
steam turbines and generate electric power.

Salient Aspects: The notable aspects of Babcock and Wilcox boiler in
the context of merits and demerits are:

1. The unit has the capability to quickly cope with high peak loads
which are generally needed at thermal power stations.

2. Its evaporating capacity is quite high compared with other boilers
(20,000 to 40,000 kg/h). The operating pressure lies between 11.5
to 17.5 bar.

3. The inspection-of the boiler can, be carried even when the boiler
is in operation.

4. The replacement of defective tubes can be made readily.
5. The draught losses are minimum.
6. Any type of fuel can be burnt in the boiler.
7. The efficiency of this boiler is more than that of fire tube boiler.
8. The entire boiler rests on an iron structure, independent of brick

structure.
9. Further, since the boiler unit (except furnace) is suspended, any

expansion or contraction of the boiler has no harmful effects on
the masonry work enclosing the furnace and the boiler.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 148

Babcock and Wilcox Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

The following necessary mountings provided for safe and easy working
of the boiler as an essential component:

Feed Check Valve
The feed check valve is fitted on front side of the drum with feed water
supply line. The feed water is supplied to the boiler through this valve. It
is unidirectional flow control valve. No reverse flow of water can take
place with this valve. The feed check valve is fitted as shown in diagram.

Water level indicator
The water level indicator is mounted on front side of the boiler shell
which indicates the level of water inside the boiler with the help of glass
tube. It helps to maintain a particular level of water inside the boiler shell;
otherwise overheating may take place which in turn may burn out the
tubes.

Pressure Gauge
It is fitted on top of the boiler shell and indicates the pressure of steam
inside the boiler when boiler is working.

Safety Valve
The safety valve is fitted on the steam space of the boiler shell. The
function of safety valve is to maintain a desired pressure in the boiler
shell. If pressure in the boiler shell increases then extra steam is released
to atmosphere through opening of safety valve.

Steam stop valve
The steam stop valve is fitted on the steam space of the boiler shell i.e. in
uppermost portion and it is connected through super heater. The super-
heated steam is taken for the required purpose by steam stop valve. The
wet steam generated is stored in boiler shell which passes to the
superheater tubes. The superheater tubes are in direct contact with flue
gases coming from furnace and transfers its heat to steam to superheat.
The steam is thus gets superheated and then it pass to steam stop valve.

Blow off cock
The blow off cock is mounted at the lowest side of the down take header
to blow off water and sediments whenever required. It is a common
practice to remove periodically the sediments and other deposited
material from the boiler shell.

Fusible plug
The fusible plug is mounted on the boiler shell above the furnace and
bottom side of the shell. This plug under normal condition is immersed in
water in the boiler which keeps the temperature of fusible metal in the
fusible plug below its melting point. When the water level in the shell
falls below the fusible plug level, the fusible metal of the fusible · plug
melts by the heat of the flue gases in the furnace.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 149

Babcock and Wilcox Boiler Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Thus, the plug drops out and the high-pressure steam/water rushes out to
the furnace and puts off the fire in the furnace. Thus, boiler is protected
from overheating and mishappening.
Man hole
A manhole usually elliptical or oval shaped and is provided at the rear
end the boiler shell. The man hole is provided for the entry of operator for
repair, cleaning and inspection purposes during annual maintenance. The
manhole and other openings are made steam tight with the help of
asbestos sheet or asbestos board, which are used as a packing material
between shell and manhole.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 150

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

REVIEW QUESTIONS
Q1. Draw a neat sketch of Babcock and Wilcox boiler.
A1.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 151

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q2. What type of boiler is Babcock and Wilcox?
Q3. Why baffle plates are used in Babcock and Wilcox boiler.
Q4. Why water tubes are inclined in Babcock and Wilcox boiler?
Q5. Write some salient features of Babcock and Wilcox boiler?

WRITE YOUR ANSWERS HERE
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
………….…………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
………………….…………………………………………………………
……………………………………………………………………………
…………….………………………………………………………………

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 152

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

MULTIPLE CHOICE QUESTIONS (✔)

Q1. Which of the following is a water tube boiler
a) Locomotive boiler
b) Lancashire boiler
c) Cornish boiler
d) Babcock and wilcox boiler

Q2. The water tubes in a Babcock and wilcox boiler are
a) Horizontal
b) Vertical
c) Inclined
d) Horizontal and inclined

Q3. Which type of water circulation inside Babcock and Wilcox boiler
a) Natural circulation
b) Forced circulation
c) No need of circulation
d) Both a & b

Q4. Babcock and Wilcox boiler is solid fuel fired boiler
a) True
b) False

Q5. Steam generation capacity of Babcock and Wilcox boiler is about
a) 2000 to 40000 kg/hr.
b) 2000 to 60000 kg/hr.
c) 2000 to 80000 kg/hr.
d) 2000 to 110000 kg/hr.

Q6. What is the angle of inclination of the tube in Babcock Wilcox
boiler
a) 35 to 45 degree
b) 10 to 15 degree
c) Only 45 degree
d) 55 to 60 degree

Q7. Babcock and Wilcox boiler also consists of following tube
a) Over flow control tube
b) Air leakage tube
c) Superheating tube
d) None of the above

Q8. Babcock Wilcox boiler works on pressure up to
a) 90 bars
b) 40 bars
c) 120 bars
d) 30 bars

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 153

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q9. Babcock Wilcox boiler is an internally fired boiler
a) True
b) False

Q10. Babcock Wilcox boiler consists ………type of axis of water
drum.
a) Vertical
b) Drumless boilers
c) Horizontal
d) Inclined

Questions for Viva-Voce

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 154

Boiler Mountings: Boiler mountings

Aaremipcrriommaerteilry, sinomteentdimedesfokrnotwhen saasfeaty
micrometer screw gauge, is a device
ionfcothrpeobraotiilnegr anad focralciobmratpeldete cscornetwrol

wofidelysteaumsed fgoerneraactciounrate plrionceeasrs.

mMeoausunrteinmgesntformofintecgormapl opnaernttss of itnhe
mabsoeiclwheaernllicaals engineering and machining
most mechanical trades,

aBloonilger Awcciethssorioetsh:eBr oilemr eatrcocleosgsiocrailes

ianrsetruinmsetanltlsedsutcohinacsrdeaiasle, tvheerneieffri,ciaenndcy
doifgitthael cbaoliipleerrsp. lants to help in proper

working of boiler unit. Accessories

are not integral part of the boiler.

Boiler Mountings &
Accessories

Experiment# 14

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

14 EXPERIMENT NO. 14

Boiler Mountings & Accessories

Boiler Mountings & Accessories AIM
To study of boiler mountings and accessories.

APPARATUS
Models of various mountings and accessories.

THEORY

For efficient operation and maintenance of safety, the boilers are

equipped with two categories of components or elements.

First category includes the fittings which are primarily intended for the

safety of the boiler and for complete control of the process of steam

generation. These units are called boiler mountings. The mountings form

an integral part of the boiler and are mounted on the body of the boiler

itself. In accordance with Indian Boiler Regulations, the following

mountings are usually installed on the boiler.

(1) Two safety valves (2) Two water level indicators

(3) Pressure gauge (4) Fusible plug

(5) Steam stop valve (6) Feed check valve

(7) Blow-off cock (8) Man and mud holes.

Out of the above-mentioned mountings, safety valve, water level
indicator and the fusible plug are called safety fittings and the remaining
are the control fittings.

Second category includes the components which are installed to increase

the efficiency of the steam power plant and help in the proper working of

the boiler unit. These fittings are called boiler accessories. Usually a

boiler has the following accessories attached to it.

(1) Air preheater (2) Economiser

(3) Superheater (4) Feed pump

(5) Injector (6) Steam separator and steam trap

BOILER MOUNTINGS
Some of the above-mentioned boiler mountings are discussed in the
following sections with particular reference to their function and location.

1. Safety Valves
Function: The function of the safety valve is to permit the steam in the
boiler to escap to atmosphere when pressure in the steam space exceeds a
certain specified limit. Thus, the safety valve prevents the building up of
excessive pressure in the boiler. As per Boiler Regulations, each boiler
must be fitted atleast with two safety valves.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 155

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Location: The safety valve is located above the steam space in the boiler.
The safety valves operate on the principle that a valve is pressed against
its seat through some agency such as strut, screw or spring by external
weights or force. When the steam force due to boiler pressure acting
under the valve exceeds the external force, the valve gets lifted off its seat
and some of the steam rushes out until normal pressure is restored again.
The commonly used safety valves are as:

(i) Dead weight safety valve
(ii) Lever safety valve
(iii) Spring loaded safety valve
(iv) High steam-low water safety valve

Figure 14.1 Dead weight safety valve

Figure 14.2 Lever safety valve

Figure 14.3 Spring loaded safety valve

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 156

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Figure 14.4 High steam-low water safety valve
2. Water Level Indicator
Function: The function of the water level indicator is to ascertain
constantly and exactly the level of water in the boiler shell.
Location: The water level indicator, also called water gauge, is fitted in
the front of the boiler from where it is easily visible to the operator. The
top of the mounting is connected with steam space and the bottom with
water space.

Figure 14.5 Water Level Indicator
3. Fusible Plug
Function: The function of the fusible plug is to extinguish the fire in the
event of water level in the boiler shell falling below a certain specified
limit. We know that when the water on heating transforms into steam, the
level of water in the boiler falls down. If the water is not replenished and
the steam generation continues then the parts which have been uncovered
by water may get overheated and subsequently get melted. To safeguard
against this eventuality, we use fusible plug.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 157

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Location: The fusible plug is inserted at the box crown or over the
combustion chamber at the lowest permissible water level.

Figure 14.6 Fusible Plug
4. Pressure Gauge
Function: Each boiler has to be provided with a pressure gauge which
records the pressure at which the steam is being generated in the boiler.
Location: The gauge is usually mounted at the front top of the boiler shell
or drum. The gauge has to be clearly visible to the attendant so that he
can easily record the pressure reading.

Figure 14.7 Pressure Gauge
5. Blow off Cock
Function: The blow off cock serves to drain out the water from the boiler
periodically for any one of the following reasons:

1. to discharge mud, scale and other impurities which settle down at
the bottom of the boiler.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 158

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

2. to empty the boiler for internal cleaning and inspection.
3. to lower the water level rapidly if the level becomes too high.
Location: The unit is fitted at the lowest portion of the boiler. It may be
mounted directly to the boiler shell or through an elbow pipe which is
fitted to the boiler shell.

Figure 14.8 Blow off Cock
6. Feed Check Valve
Function: The feed check valve has the following two functions to
perform:

1. to allow the feed water to pass into the boiler.
2. to prevent the back flow of water from the boiler in the event of

the failure of the feed pump.
Location: The valve is installed between the feed pump and the water
space of the boiler shell.

Figure 14.9 Feed Check Valve

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 159

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

7. Stop Valve
Function: The function of the steam slop valve is to shut off or regulate
the flow of steam from the boiler to the steam pipe or from the steam pipe
to the engine. When used for the former purposes, it is called junction
valve. Usually the junction valve means a regulating valve of larger size
and a stop valve refers to a regulating valve of smaller size.
Location: The junction valve is mounted on the highest part of the steam
space of the boiler and is connected to the steam pipe which carries the
steam to the engine.

Figure 14.10 Stop Valve

8. Manholes
Function: These are doors to allow men to enter inside the boiler for
inspection and repair.

BOILER ACCESSORIES

The components which are installed to increase the efficiency of the

steam power plant and help in the proper working of the boiler unit.

These fittings are called boiler accessories. Usually a boiler has the

following accessories attached to it.

(1) Air preheater (2) Economiser

(3) Superheater (4) Feed pump

(5) Injector (6) Steam separator and steam trap

Some of the important boiler accessories are discussed in the following
sections with particular reference to their function and location.

1. Air Preheater
Function: Air heaters or air preheaters are waste heat recovery devices in
which the air on its way to the furnace is raised in temperature by
utilizing the heat of the exhaust gases. Roughly there is again of about 2%
in the boiler efficiency for each 35-40°C rise of the temperature of
combustion air. The other advantages of using preheated air are:

1. increase in the evaporated rate,
2. better combustion with less soot, smoke and ash,
3. low grade and inferior fuels can be used.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 160

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Figure 14.11 Air Preheater
Location: Air preheater is generally placed after the economiser, so that
the flue gases first pass through the economiser and then to the air
preheater.

Figure 14.12 Economiser
2. Economiser
Function: The economiser is a device which serves to recover some of
the heat being carried by exhaust flue gases. The heat thus recovered is
utilized in raising the temperature of feed water being supplied to the
boiler. If the feed water at raised temperature is supplied to the boiler, it
needs less heat for its conversion into steam and thus there is a saving in
the consumption of fuel. The other advantages claimed by installing an
economiser are:
Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 161

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

1. Improvement in the thermal efficiency of the steam plant. It has
been estimated that for each 8.5 to 6°C rise in the temperature of
feed water, there is a gain of about 10% in the plant efficiency.

2. Reduction in the losses of heat with flue gases.
3. Increase in the steaming capacity of the boiler.
4. Less thermal stresses in the boiler parts and consequently long life

of the boiler.
Location: The economiser unit is installed in the path of the flue gases
between the boiler and the chimney.

3. Superheater
Function: The steam generated by a simple boiler is generally wet or at
the driest saturated. Steam superheater is a surface heat exchanger in
which the wet stream is first dried at the same temperature and pressure
and then raised to temperature above the saturation temperature at
constant pressure.
Since superheating results in the increased efficiency and economy of the
steam plant, it has become the most important accessory of the steam
power plants. The advantages of using superheated steam are:

1. Increase in the amount of work output for the same weight of
steam and consequently increase in cycle efficiency.

2. Loss due to condensation of steam in reciprocating steam engines
is minimised to an appreciable extent.

3. No condensation of steam in the pipe line connecting the boiler to
the appliance.

4. Absence of moisture in the steam reduces the friction and the
erosion of steam turbine blades.

Location: Heat of flue gases is utilized in superheating the steam and as
such the superheater is placed in the path of flue gases. However, in
bigger installations, the superheater may be placed in an independently
fired furnace. Such superheaters are, known as separately fired or
portable superheaters.

Figure 14.13 Sudgen's Hair Pin Type Superheater

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 162

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

4. Feed Water Equipment
Function: The pressure inside a steaming boiler is high and so the feed
water has to be raised in pressure before its entry can be affected in the
boiler. Feed pump is a device which raises the pressure of water and
forces it into the boiler. The commonly used pumping devices are:

1. Centrifugal pump
2. Reciprocating pump
3. Steam Injector

Figure 14.14 Steam Injector
Fig. 14.15 indicates the position of an economiser, an air preheater, and a
superheater in a steam generating plant.

Figure 14.15 Schematic diagram of a boiler plant showing important
accessories and flow sheet

In addition to the fittings described above, the boilers are also fitted with
an antipriming pipe, water separator and the steam trap. We know that
when a boiler is required to raise steam quickly, the steam is bound to
carry water particles with it. Before being supplied to the engine,
arrangements are made to separate the water particles going along with
steam.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 163

Boiler Mountings & Accessories Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

An antipriming pipe is a cast iron box which is fitted in the steam space
of the boiler shell and under the mounting block on which the steam stop
valve is to be bolted. When the steam with water particles passes through
the perforations made in the upper half of the antipriming pipe, the
heavier water particles separate out and are collected at the bottom of the
pipe. The water thus collected is later on drained to the boiler through the
holes which are made at the ends of the pipe.
The steam separator or drier also serves the purpose to remove the water
particles being carried along with steam and the water particles resulting
from a certain amount of condensation in the steam pipe between the
boiler and the engine. The steam is led to pass through a chamber in
which it strikes the baffle plate, gets deflected and made to change its
direction. The water particles are thrown out because of greater inertia.
The water collected at the bottom of the chamber is drained out at regular
intervals.
Steam traps are used to collect and automatically drain away the water
resulting from the partial condensation of steam without allowing any
steam to escape with it. The steam condensed in the steam pipe flows to
the steam trap by gravity. When the level of water in the trap becomes
sufficiently high, a valve opens a passage through which the water is
forced out. After the water has been discharged the passage is again
closed and this prevents the escape of steam which follows water.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 164

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

REVIEW QUESTIONS

Q1. What are boiler mountings and accessories?
Q2. Write down the name of basic mountings used in boiler.
Q3. Write down the name of various accessories used in boiler.

WRITE YOUR ANSWERS HERE
……………………………………………………………………………

……………………………………………………………………………

……………………………………………………………………………

Questions for Viva-Voce ……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………

……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………

……………………………………………………………………………
……………………………………………………………………………

……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………

Q4. Complete the following tables

S. Boiler Function
No. Accessories

1 Economiser ……………………….………………..………...
…………………………………………………..

2 Superheater …………………………………………………..
…………………………………………………..

3 Air preheater …………………………………………………..
…………………………………………………...

4 Steam injector ……………………………………………..……
…………………………………………………..

5 Anti-priming …………………………………………………...
pipe ……………………………………..…………….

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 165

Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q5. Complete the following tables

S. Boiler Function
No. Mountings

1 Safety ……………………….………………..………...
valves …………………………………………………..

Questions for Viva-Voce 2 Water-level ……………………….………………..………...
indicator …………………………………………………..

3 Pressure ……………………….………………..………...
gauge

4 Steam stop ……………………….………………..………...
valve
…………………………………………………..

5 Feed check ……………………….………………..………...

valve …………………………………………………..

……………………….………………..………...

6 Blow-off ……………………….………………..………...
cock
…………………………………………………..

7 Man hole ……………………….………………..………...
…………………………………………………..

8 Mud hole ……………………….………………..………...
(with door) ………………………………………………….

9 Fusible plug ……………………….………………..………...
…………………………………………………..

High ……………………….………………..………...

10 pressure, …………………………………………………..
low water ……………………….………………..………...

safety valve …………………………………………………..

Low water, ……………………….………………..………...
11 high water …………………………………………………..

safety valve ……………………….………………..………...

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 166

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q6. Draw a neat sketch of fusible plug.
A6.

Q7. Draw a neat sketch of water level indicator.
A7.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 167

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

Q8. Draw a neat sketch of Sudgen's hair pin type superheater.
A8.

Q9. Draw a schematic diagram of a boiler plant showing important
accessories and flow sheet.

A9.

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 168

Questions for Viva-Voce Lakshmi Narain College of Technology (LNCT) Bhopal (MP)

MULTIPLE CHOICE QUESTIONS (✔)

Q1. The following is an accessory of a boiler
a) Pressure gauge
b) Safety valve
c) Fusible plug
d) Super heater

Q2. The following is a boiler mounting
a) Feed pump
b) Water level gauge
c) Economizer
d) Super heater

Q3. The impurities are removed from boiler with the help of
a) Safety valve
b) Blow off cock
c) Stop valve
d) Fusible plug

Q4. Which of the following is used to heat the feed water by using
waste heat of flue gases?
a) Air preheater
b) Superheater
c) Economizer
d) Steam separator

Q5. ………..is generally placed after the economizer
a) Air preheater
b) Superheater
c) Evaporator
d) None of the above

Q6. How many level indicators are there in the water level indicator of
a boiler?
a) 1
b) 2
c) 3
d) 4

Q7. Other than Steam stop valve in the boiler which is the other
similar type of valve used?
a) Non-reversible valve
b) Transient valve
c) Reversible valve
d) Junction valve

Mechanical Engineering Department | Lab Manual | Basic Mechanical Engineering [BT-203] 169