1. Industrial 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 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. Locomotive Boiler
Is an internally fired multitubular fire tube boiler

12. 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.

13. Stirling Boiler
Example of water tube boiler where bent tube are used instead of straight tube which are used in Babcock and Wilcox boiler

14. High Pressure Boilers
Two types- Natural circulation & Forced circulation Boilers

15. High Pressure Boilers contd………
La-Mont Boiler( Forced circulation Boiler)

16. Once-Through Forced Circulation Boiler
Does not required a steam and water drum,saving in weight
Supercritical Pressure Boiler
Two types- Benson and Ramzin

17. Ramzin Boiler

18. Loeffler Boiler
Indirect heating is combined with forced circulation

19. Velox boiler
Fire tube forced circulation Boiler

20. 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.

21. Boiler Mountings and Accessories
Fitting and devices which are necessary for the safety and control are knows as boiler mountings
Fitting or devices which are provided to increase the efficiency of the boiler and help in the smooth working of the plant are knows as boiler accessories.
Fittings which are essential from the safety point of view are as follows,
Water level indicators
Safety valves
Combined high steam and low water safety valve
Fusible plug

22. Boiler Mountings and Accessories contd….
Fittings which are essential from the control point of view are as follows,
Pressure gauge
Junction or stop valve
Feed check valve
Blow-off cock
Man hole and Mud Box
The important accessories are
Superheater
Economiser
Air-preheater
Feed pump or injector