Industrial Boilers

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 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. 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