By: Khalid Nawaz
Institute Of Chemical Engineering And Technology
University Of the Punjab Lahore Pakistan
What is a boiler/steam
• A closed vessel made up of steel to transfer heat
produced by combustion of fuel to water and ultimately
generate steam .
It may be defined as:
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.
What should characteristics
Generate maximum steam.
Light in weight and not occupy large space.
Proper safety regulations.
Cheaper in cost.
Easy cope up with fluctuating demands of
Easily accessible for inspection and repair.
Where Steam is Used
Steam is used in steam generators for production of
It is used as heating source for different purposes
Steam is used for production of different products in
Sources of heat in boiler..??
Water tube Fire tube
Classification of Boilers:
Boilers may be classified according to the following-
1. Relative position of Hot gases and Water
a) Fire tube boiler:
The hot gases passes through the tubes that are
surrounded by water. Fire tube boilers are also known by
certain common names-
i) Horizontal return tubular
ii) Locomotive fire box
iii) Scotch marine and,
iv) Vertical tubular
b) Water tube Boiler:
The water passes through the tubes and the hot gases
produced by combustion of fuel, flow outside. This
type of Boilers designated by the following
i) Babcock and Wilcox Boiler (straight but inclined
tubes which connect the headers).
ii) Stirling Boiler (multitubular boiler having bent
tubes that connect boiler drums to headers).
BOILER MOUNTINGS AND ACCESSORIES
Boiler Accessories for efficient operation:
1. Water heating devices.
2. Water feeding devices.
3. Super heater
5. Air preheater
The boiler mountings are the part of the boiler and are
required for proper functioning.
In accordance with the Pakistan Boiler regulations, of the
boiler mountings is essential fitting for
safe working of a boiler.
Water level indicator..??
Water level indicator is
located in front of boiler
in such a position that
the level of water can
easily be seen by
attendant. Two water
level indicators are used
on all boilers.
A pressure gauge is
fitted in front of boiler
in such a position that
the operator can
conveniently read it. It
reads the pressure of
steam in the boiler and
is connected to steam
space by a siphon tube.
The most commonly, the
Bourdon pressure gauge
Safety valves are located on the top of the boiler. They guard the boiler
against the excessive
high pressure of steam inside the drum. If the pressure of steam in the boiler
the working pressure then the safety valve allows blow-off the excess
quantity of steam to
atmosphere. Thus the pressure of steam in the drum falls. The escape of
steam makes a
audio noise to warm the boiler attendant.
There are four types of safety valve.
1. Dead weight safety valve.
2. Spring loaded safety valve
3. Lever loaded safety valve
4. High steam and low water safety valve
Dead weight safety valve Spring loaded safety valve
Lever loaded safety valve
It is very important safety device, which
protects the fire tube boiler against
overheating. It is
located just above the furnace in the boiler. It
consists of gun metal plug fixed in a gun metal
body with fusible molten metal.
During the normal boiler operation, the fusible
plug is covered by water and its temperature
does not rise to its melting state. But when the
water level falls too low in the boiler, it
uncovers the fusible plug. The furnace gases
heat up the plug and fusible metal of plug
the inner plug falls down The water and steam
then rush through the hole and extinguish the
fire before any major damage occurs to the
boiler due to overheating.
The function of blow-off cock is to
discharge mud and other
sediments deposited in the
bottom most part of the water
space in the boiler, while boiler is
in operation. It can also be
used to drain-off boiler water.
Hence it is mounted at the lowest
part of the boiler. When it is
open, water under the pressure
rushes out, thus carrying
sediments and mud.
Feed Check Valve
The feed check valve is fitted
to the boiler, slightly below the
working level in the boiler. It
is used to supply high pressure
feed water to boiler. It also
prevents the returning of feed
water from the boiler if feed
pump fails to work.
Steam Stop Valve
The steam stop valve is
located on the highest part of
the steam space. It regulates
supply to use. The steam stop
valve can be operated
manually or automatically.
Air preheater : It utilize the heat of exhaust
Economizer: Heat is used to raise the
temperature of feed water supplied to the boiler.
Steam super heater: Used to super heat the
Feed pump: Raise the pressure of water and
force it into the boiler.
An economizer is a device in which
the waste heat of the flue gases is
utilized for heating the feed water.
Economizer are of two types :
a) Independent type, and
b) Integral type
The function of an injector is to
feed water into the boiler. It is also
used where the space is not
available for the installation of a
Its is a pump which is used to deliver
feed water to the boiler.
The appliances in common use for
delivering the feed-water into the
steam boilers are:
a) Reciprocating pump
b) Rotary pump
Ratio of heat actually utilized in the generator to the heat
supplied by the fuel.
Efficiency= ma ( h –
Where, C is the calorific value of the
Boilers are most important part of chemical industry.99
% boilers used in Pakistan chemical industries are water
tube boilers because of their high efficiency and
safety.so we should have cler understanding about the