Boiler

1. Steam Boilers
 Steam generators
 Closed vessels
 made of steel and
 used for generation of steam
 vaporizing water
 combustion of fuels
 eg. coal,coke,oil,wood,saw dust and begesse etc.
 Steam used for producing power,for industrial
process work or for heating proposes.

2. Requirements of a Perfect
Steam Boilers
 Should be absolutely reliable,capable of producing
maximum steam at required pressure for minimum of
fuel consumption,with minimum attention and minimum
initial cost and operating cost.
 Simple constructions
 Quick starting from cold
 Strong enough against temp. stress & strains
 Well design combustion chamber
 Less floor area, space & light weight
 Best gauges,safety valves and other mountings
 Easily accessible for inspection,cleaning and repairs

3. Classification of Steam
Boilers
 Vertical or Horizontal
 Stationary(Power plant,industrial,central heating and
combined power and heating
boilers.),Portable,Locomotive or Marine
 Internally Fired or Externally Fired (Lancashire and
Locomotive Boilers)
 Solid,Liquid or Gas Fired
 Fire(Smoke)Tube:Water is outside the tubes while the
hot gases are inside the tubes
eg.Vertical,Cochran,Lancashire,Cornish,Locomotives,etc
) or Water Tube: Contain a large number of small tubes
through which water circulates,the fire and hot gases
being outside of the tubes.eg.Babcock and Wilcox,
Stirling and High pressure Boilers etc.)

4. Vertical Boilers
 Used in small factories,small water supply
plants,cranes,excavators,winch engines in
mines and on sites of temporary nature such
as construction work etc.
 Required minimum floor space,not required
elaborate foundations,and is portable.
 Cheap,easy to start but inefficient due to large
wastage of fuel and less heating surface.
 Vertical Boilers are:Simple(having one to three
cross tubes), fire tubes and water tubes types.

5. Simple Cross tube vertical
boiler
 consists of a cylindrical shell surrounding a cylindrical fire box.
 heating surface is about 8-10 times the grate area.
 50% efficiency

6. Cochran Boiler
 It is well design of a Vertical multitubular fire tube boiler
 Improvement over the simple vertical boiler as it
provides greater heating surface.
 Total heating surface area is about 10-25 times the
grate area
 Efficiency 70-75%
 Ranges from 1m dia.X2m high,evaporation 20kg/hr to
3m dia X6m high,evaporation 3000kg/hr.

7. Cochran Boiler contd….

8. Lancashire Boiler
 Is horizontal smoke tube boiler size range
from a shell 2m diaX6m long to 3m diaX10m
long
 Working pressure range are up to 20kgf/cm2
 Ratio of heating surface to grate area is 24-30
 Efficiency is about 56% without economizer
and 75% with economizer.
 Similar to Cornish boiler,in Lancashire Boiler
two flue tubes but in Cornish boiler only one
flue tubes are there.

9. Lancashire Boiler contd……

10. Lancashire Boiler contd……

11. Babcock and Wilcox water
tube Boiler
 Water tube boiler having lager pressure ranges and
larger sizes.
 Three main parts, steam and water drum,water tubes
and furnace.

12. Fire tubes Vs water tubes
Boilers
 Fire tubes boilers has a large volume of water,therefore
more flexible and can meet the sudden demand of
steam without much drop of pressure.
 Fire tubes boiler is rigid and of simple mechanical
construction,so greater reliability and low in first cost.
 Fire tube boilers can be made in smallest sizes therefore
simple to fabricate and transport, occupies less floor
space but more height.
 Due to mostly externally fired water tubes boiler so
furnace can be altered considerably to meet the fuel
requirements.
 Water tubes boilers are more readily accessible for
cleaning,inspection and repairs,compared to the fire
tube boilers.
 Modern trend is in the favors of water tube boiler due to
continuous increase in capacities and steam pressures.