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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 industrialprocess work or for heating proposes.

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STEAM GENERATORS

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BOILER ALTERNATOR TURBINE

TO

PROCESS

TO PROCESS

Fuel

Air

TO

POWER 

SUPPLY

CONDENSER 

TO COOLINGTOWER 

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R equirements 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

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Classification of Steam

Boilers Vertical or Horizontal

Stationary(Power plant,industrial,central heating andcombined 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 thehot gases are inside the tubeseg.Vertical,Cochran,Lancashire,Cornish,Locomotives,etc) or Water Tube: Contain a large number of small tubesthrough which water circulates,the fire and hot gasesbeing outside of the tubes.eg.Babcock and Wilcox,Stirling and High pressure Boilers etc.)

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Vertical Boilers Used in small factories,small water supply

plants,cranes,excavators,winch engines in

mines and on sites of temporary nature suchas construction work etc.

R equired minimum floor space,not requiredelaborate foundations,and is portable.

Cheap,easy to start but inefficient due to largewastage of fuel and less heating surface.

Vertical Boilers are:Simple(having one to threecross tubes), fire tubes and water tubes types.

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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

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Cochran Boiler It is well design of a Vertical multitubular fire tube boiler

Improvement over the simple vertical boiler as itprovides greater heating surface.

Total heating surface area is about 10-25 times thegrate area

Efficiency 70-75%

R anges from 1m dia.X2m high,evaporation 20kg/hr to3m dia X6m high,evaporation 3000kg/hr.

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Cochran Boiler contd«.

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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

R atio 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 oneflue tubes are there.

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Lancashire Boiler contd««

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Lancashire Boiler contd««

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Locomotive Boiler Is an internally fired multitubular fire tube boiler

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LOCOMOTIVE BOILER CONTINUED

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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.

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Stirling Boiler Example of water tube boiler where bent tube are used

instead of straight tube which are used in Babcock and Wilcoxboiler

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Stirling Boiler

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High Pressure Boilers Two types- Natural circulation & Forced circulation

Boilers

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High Pressure Boilers contd««« La-Mont Boiler( Forced circulation Boiler)

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La-Mont Boiler

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Once-Through Forced

Circulation Boiler Does not required a steam and water drum,saving in weight

Supercritical Pressure Boiler

Two types- Benson and R amzin

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BENSON BOILER

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R amzin Boiler

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Loeffler Boiler Indirect heating is combined with forced circulation

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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 mechanicalconstruction,so greater reliability and low in first cost.

Fire tube boilers can be made in smallest sizes thereforesimple to fabricate and transport, occupies less floorspace but more height.

Due to mostly externally fired water tubes boiler so

furnace can be altered considerably to meet the fuelrequirements.

Water tubes boilers are more readily accessible forcleaning,inspection and repairs,compared to the firetube boilers.

Modern trend is in the favors of water tube boiler due tocontinuous increase in capacities and steam pressures.

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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 workingof the plant are knows as boiler accessories.

Fittings which are essential from thesafety point of view are as follows,

      Water level indicators

      Safety valves

      Combined high steam and low water safety valve

      Fusible plug

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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