Cochran boiler presentation

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Topic : cochran boiler By rajesh goswami

Transcript of Cochran boiler presentation

Page 1: Cochran boiler presentation

Topic : cochran boilerBy rajesh goswami

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Cochran boiler is modification of simple vertical boiler where heating surface has bin increased by increasing numbers of fire tubes.

It is used for steam generation at low rate. It is a fire tube boiler.

Cochran boiler

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Characteristics of boiler: A vertical, multi tubes, fire tube, internally fired, natural circulated boiler.

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Specification: Shell diameter: 2.75m, height 5.75m heating surface area 120m², working pressure 6.5bar (max 15bar), steam capacity 3500kg/hr (max capacity

4000kg/hr), efficiency 70% to 75%.

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1).Cylindrical shell: It is shell in which different parts of the boiler are enclosed and on which the different mountings are fitted.

2).Grate: It is platform in the furnace on which fuel is burnt.

3).Furnace(Fire box): It is a chamber formed by the space above the grate and below the boiler shell in which combustion takes place. It is also called a fire box. This chamber contains hot gases produced by combustion of fuel.

Basic parts of boiler

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4). Fire hole: it is the hole through which coal is added to the furnace.

5).Ash-pit: It is the area in which the ash of burnt coal is collected.

6). Smoke chamber (smoke box): The waste gases are collected here and then release to the chimney and then to atmosphere.

7).Man hole: It is a hole provided on the boiler shell so that a work man can go inside the boiler for inspection, cleaning and maintenance . Based on man shape and strength point of view it is in oval shape. An oval shaped door or cover is provided to close the man hole.

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8). Hand holes: It is a hole provided on the shell to give easy access for the purpose of cleaning the water tubes or some other internal parts of boiler. They are also fitted with covers.

9).Mud box: It collects all impurities present in the water. It is at the bottom of barrel or shell. This impurities are removed time to time by help of blow off cock.

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10) Steam collecting pipe(Anti priming pipe): when the steam leaving the boiler , it contains certain amount of water. Anti priming pipe is used to separate water particles from the steam and to collect dry steam from boiler. The water having a much higher specific gravity than the steam, tends to fall back as the steam moves upward. Also a deflector is provided in the path of wet steam which change the direction of wet steam , since water particles having more weight and higher inertia, can not follow the steam path so it fall back. This principle is used in steam collecting pipe.

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Steam collecting pipe is a horizontal perforated pipe placed on the top of the steam space of the boiler. The wet steam enters into the pipe through rectangular holes in down ward direction and again the steam has to change the direction and move upward. But water particles having high weight so it fall back and settle at the bottom of the pipe. The small hole provided at the bottom of the pipe to drain the water.

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The boiler consists of cylindrical shell , hemispherical fire box , fire tubes and chimney . The top of the shell having hemispherical shaped crown . The hemispherical crown of boiler gives good strength to with stand pressure of steam inside the boiler . The hemispherical shape of furnace can withstand high heat and is also useful to increase radiant heat transfer from the furnace to hemispherical furnace wall . The grate is placed at the bottom of the furnace and ash pit is located below the grate . The furnace and the combustion chamber are connected by short flue pipe . The wall of the combustion chamber is lined with the fire bricks . The ash pit is located below the grate.

Construction

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The water is supplied to the boiler through feed check valve . The coal is introduced to the grate trough the fire door . The hot gases produced from furnace enters combustion chamber through flue pipe . This hot gases enters into horizontal fire tubes . Convection heat transfer take place from flue gases passing inside the tubes to water surrounded the tubes . The flue gases coming from fire tubes enter into smoke box . Finally they discharge to atmosphere through a chimney . The ash formed is collected in ash pit . The steam is collected through antipriming pipe on top of the shell .

Working

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Steam pressure gauge water level indicator dead weight safety valve feed check valve , blow off cock , steam stop valve , manhole , fusible plug , anti priming pipe and dampers are the boiler

mounting .

Mounting

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Fusible Plug. If the water level in the boiler falls below a

predetermined level, the boiler shell and tubes will be overheated.

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Water Level Indicator. This indicates the water

level in the boiler .

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Pressure Gauge. This indicates the

pressure of the steam in the boiler.

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Steam Stop Valve. It regulates the flow of steam supply

outside. The steam from the boiler first enters into an ant-priming pipe where most of the water particles associated with steam are removed

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Feed Check Valve. The high pressure

feed water is supplied to the boiler through this valve. This valve opens towards the boiler only and feeds the water to the boiler.

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Blow-off Cock. The water supplied

to the boiler always contains impurities like mud, sand and, salt Due to heating, these are deposited at the bottom of the boiler, they have to be removed using blow off cock.

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1). It is compact and portable boiler therefore minimum floor area is required .

2). Initial cost of boiler is less .3). It can be moved and set up readily in

different location .4). Quick and easy installation .5). Any type of fuel can be used ( coal or

oil ) .

Advantages

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1). Steam raising capacity is less due to vertical design .

2). Water along with steam may enter the steam pipe under heavy loads due to small steam space .

3). Efficiency is poor in smaller sizes .

Disadvantage

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Thank you…