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Presenting a power point presentation on introduction and

classifications of boilers

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A closed fuel-burning apparatus or container for

heating water

Boiler it’s a device in which steam is used for driving prime movers like steam

turbines or industrial purpose like heating process.

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According to Indian boiler regulations ,boiler is a closed pressure vessel in which steam is generated with capacity exceeding 25 liters, estimate pressure greater than or

equal to 1Kg/cm (sq.),and water is heated at 100 degree Celsius or above.

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6For generating power in steam engines or steam turbines

In textile industries for sizing and bleaching

For heating the buildings in cold weather and for producing hot water for hot water supply.

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According to position of water and hot gases:

(A) fire tube boilers(B)water tube boilers

According to location of furnace:(A) externally fired boilers(B)internally fired boilers

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According to method of water circulation:(A) Naturally circulation boilers(B) forced circulation boilersAccording to working pressure:(A) high pressure boilers(B) medium pressure boilers(C) low pressure boilers

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According to mobility :

(A)staionary boilers

(B)mobile boilers

According to tubes:

(A) single tube boilers

(B) multi tube boilers

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Further …..there are three types of boilers…..

Lancashire boiler

Locomotive boiler (SIMPLE BOILER)

Cochran boiler

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Locomotive boiler (SIMPLE BOILER)

Main characteristics of this boiler:

PortableNatural circulated and low pressure

boiler

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13Construction of locomotive

boiler

As all you can see locomotive boilers construction

Its vertical

Fire box at bottom

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14Working of locomotive

boiler

Fuel is place on the grate where it is burned to produce the hot gases.

Fire hole is used to feed the fuel. Hot gases which are produce as a result of fuel burning are diverted into fire tube with the help of fire brick arch.

Steam produce is collected is the steam drum place at the top of the shell.

As shown the wet steam goes through inlet headers of super heater and after passing through tubes, it returns to the outlet header of super heater and is taken out for steam engine. For the cleaning and maintenance of the complete boiler a door is provided at the side of the smoke box.

Chimney is completely eliminated in locomotive boilers because they are always in motion

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Lancashire boiler

Main characteristics of this boiler:

Horizontal

Stationary

Natural circulation of hot gases

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construction

Cylindrical shell

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18Working

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In Lancashire Boiler first coal is fed on the grate where combustion of coal takes place.

The Flue gases pass through the internal flue tubes and then pass downwards.

The flue gases travels through the bottom flue to the front of the boiler.

Then they are split up into two  steams and flow through the side flues to the rear end of the boiler.

Flue gases then pass through the dampers into the main flue and are finally discharged through the chimney into the atmosphere.

The heat of flue gases is transferred to the water to generate steam.

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Cochran boiler

Main characteristics of this boiler:VerticalFire tubesNaturally circulated fire

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working

Coal is fed into the grate through the fire hole and burnt.

Ash formed during burning is collected in the ash pit provided just below the grate and then it is removed manually.

The host gases from the grate pass through the flue pipe to the combustion chamber.

The hot gases from the combustion chamber flow through the horizontal fire tubes and transfer the heat to the water by convection.

The flue gases coming out of fire tubes pass through the smoke box and are exhausted to the atmosphere through the chimney.

Smoke box is provided with a door for cleaning the fire tubes and smoke box.

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Babcock and Wilcox boiler

Main characteristics of this boiler

Steam and water drum (boiler shell)

Water tubes

Furnace

Mud box: 

Inspection doors: 

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Working Babcock and Wilcox Boiler:

The hot flue gases rise upward and pass across the left-side portion of the water tubes.

The baffles deflect the flue gases and hence the flue gases travel in the zigzag manner (i.e., the hot gases are deflected by the baffles to move in the upward direction, then downward and again in the upward direction) over the water tubes and along the superheated.

The flue gases finally escape to atmosphere through chimney.

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Accessories of

boilers

Feed Water Pump:

It is used to feed the water at a high

pressure against the high pressure of steam already

existing inside the boiler.

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Steam Injector:

A steam injector lifts and forces the feed water into the boiler. It is usually used for vertical and locomotive boilers and can be

accommodated in small space. It is less costly. It does not have any

moving parts thus operation is salient.

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Economizer: An economizer is a heat exchanger, used for

heating the feed water before it enters the boiler. The

economizer recovers some of waste heat of hot flue gases going to chimney. It helps in

improving the boiler efficiency. It is placed in the

path of flue gases at the rear end of the boiler just before

air pre-heater.

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Air Pre-heater : The function of an air pre-heater is similar to

that of an economizer. It recovers some portion of the waste heat of hot flue gases going to chimney, and transfers same to the fresh air before it enters the combustion chamber. Due to preheating of air, the furnace temperature increases. It results in rapid combustion of fuel with less soot, smoke and ash. The high furnace temperature can permit low grade fuel with less atmospheric pollution. The air pre-heater is placed between economizer and chimney.

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Super heater:

It is a heat exchanger in which heat of combustion products is used to dry the wet steam, pressure remains constant, its volume and temperature increase. Basically, a super heater consists of a set of small diameter U tubes in which

steam flows and takes up the heat from hot flue gases.

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