SHANKHERSINH VAGHELA BAPU INSTITUTE OF TECHNOLOGY

MECHANICAL DEPARTMENT

BOILERSPREPARED BY=

Krishna Gondaliya-

(140750106032)

Ujas Patel-

(140750106096)

Keval Barbasiya-

(140750106004)

Ambili punnath-

(140750106106)

GUIDED BY=

Nishant Patel

INDEX

I. Introduction

II. Cochran boiler

III. Lancashire boiler

IV. Badcock and Wilcox water tube boiler

V. Boiler mountings and accessories

INTRODUCTION Steam boiler is a closed vessel in which heat

produced by the combustion of fuel is utilized to produce steam from water, at desired temperature and pressure.

Boiler is a device used for generating steam which is used for driving prime movers like steam turbines or industrial purposes like process heating.

According to INDIAN BOLIER REGULATION a boiler is a closed pressure vessel with capacity exceeding 22.75 litres for generating steam under pressure.

COCHRAN BOILER Cochran boiler is modification

of simple vertical boiler where heating surface has been increased by increasing numbers of fire tubes.

It is used for low rate of steam generation.

CONSTRUCTION The boiler consists of a cylindrical shell,

hemispherical fire tube and chimney. The hemispherical crown of boiler gives good

strength to withstand steam inside the boiler. The grate is placed at the bottom of furnace

and ash pit is located below the grate. The wall of combustion chamber is lined with

the fire bricks.

WORKING The water is supplied to the boiler through feed check

value. The coal is introduced to the grate through the fire

door. The hot gases produced from furnace enters

combustion chamber through flue pipe. Heat transfer takes place from flue gases passing

inside the tube of water surrounded the tubes by convection.

The flue gases coming from of fire tubes enter into smoke box.

Finally they discharge to atmosphere through chimney.

ADVANTAGES AND DISADVANTAGES

ADVANTAGES It is compact and

portable boiler. Initial cost of boiler

is less. It can be moved and

set up readily in different locations.

Easy and quick installation.

DISADVANTAGES Steam raising

capacity is less. Water along the

steam may enter the steam pipe under heavy loads due to small steam space.

Efficiency is poor in smaller sizes.

LANCASHIRE BOILER

Lancashire boiler is simple in design, easy to operate and less operating and maintenance cost.

It is commonly used in suger mills, textile industries where power generation as well as access heating is required.

It is one of the commonly used as a stationary boiler.

CONSTRUCTION It consists of a cylindrical shell and two fire tubes. The cylindrical shell is placed over the brick structure. One flue passes from inside the boiler, second from

below and third from the side of boiler shell. These three passes are formed by brick work, one

bottom flue and two side flue. A fire is provided at the end of the grate to prevent coal

and ash particles into the interior of the furnace tubes. Superheater is provided at the end of the main flue tubes

in passage of flue gases. While an economiser is at the end of the side flues,

before exhausting the gases to chimney. Damper is placed at the end of side flues.

WORKING

The coal is introduced to the grate through fire holes.

The combustion of coal takes place in presence of air which is regulated by damper.

The combustion will produce gases.

ADVANTAGES AND DISADVANTAGES

ADVANTAGES Due to three passes of flue

gases, the heating surface area per unit volume of boiler is large.

The fluctuations in load can be easily met by this boiler due to large reservoir.

Easy operation, low maintenance costs, easy to clean and inspect.

By use of economiser and superheater, maximum heat of flue gases is utilized, so efficiency of boiler can be increased.

DISADVANTAGES Maximum working

pressure is limited to 16 bars.

Due to brick work, more floor area is required.

Response of pressure build up is less.

The furnace is inside the tubes therefore the grate area is restricted.

BADCOCK AND WILCOX BOILER

It is used in stationary and marine engine.

The efficiency of this boiler is much greater than the fire tube boiler.

This boiler is exclusively used when pressure is above 10 bar and steam generating capacity is required higher then 7000kg/hr.

CONSTRUCTION It consists of inclined water tubes, a steam and water drum, a

mud box and superheater. The drum is connected to up take and down take header by

short riser tubes. These headers are connected to a series of inclined water

tubes. The hand hole is provided in header in front of each tube for

cleaning and inspection of tubes. The baffles plates are provided in order to make the

circulation of hot gases in sine of wave form. A damper is fitted at back of boiler to ragulate the draught and

the furnace is equipped with chain grate stroker to feed the coal to furnace.

Soot doors is provided to clean the outside of the water tubes & to remove soot.

WORKING The water is feed into the drum through the feed

check valve. Due to gravity water passes through the short raiser

tubes, header and fills up the inclined water tubes. Then water collects in the drum.

Initially one half of drum is filled up with water. The coal is introduced to furnace grate by help of stroker.

The coal is fired, hot gases produced is first forced to move upwards between tubes. The damper controls the flow of air into the furnace.

Due to heating of the water density of water decreases. Low density water moves upward in water tubes.

CONTINUE......

The water tubes just above furnace is heated comparatively at higher temperature than the rest of it. Therefore low density water converted into the steam.

Then the steam enters through the antipriming pipe and flows in the superheater tubes where it is further heated and is finally taken out through the main stop valve and supplied to the engine when needed.

ADVANTAGES The steam generation capacity of this boiler

is very high, about 2000 to 40,000 kg/hr. Replacement of defective tubes is easy. The draught losses as compared to other

boilers is minimum. It is used in power stations for generating

large quantity of steam. Boiler is required less space area compared

to fire tube boilers, and offers greater operational safety.

BOILER MOUNTINGS

PRESSURE GAUGE It is an instrument

measure the pressure

of steam in boiler.

WATER LEVEL INDICATOR

Indicate the water level inside the boiler. It shows level of water in the boiler drum.

STEAM STOP VALVE To regulate the flow

of steam from boiler to the steam pipe or from one steam pipe to the other.

FEED CHECK VALVE To control the supply of

water to the boiler and to prevent the back flow of water from the boiler when the feed pump pressure is less then boiler pressure or pump is stopped.

BLOW-OFF COCKIt performs two functions To discharge periodically a

portion of water which contains mud, scale or sediments at bottom of boiler vessel while boiler is in operation. We know that water feed to the boiler, it contains some sediments and dissolved salts, it is not converted to steam, but diposited on the bottom of boiler vessel. So blow off cock useful to discharge a water which contains mud, sediments, etc.

To empty the boiler when necessary for cleaning, inspection and repair.

FUSIBLE PLUG To protect the boiler

against damage due to overheating caused by low water level in boiler.

SAFETY VALVES To release the excess steam when the pressure of steam inside

the boiler increases higher than the safe pressure. Safety valve are used to maintain safe pressure inside the boiler.

As soon as pressure of steam inside the boiler increases higher than the safety pressure, safety valve automatically opens and excess steam rushes out into the atmosphere still pressure drops down to normal value. Safety valve generally mounted on the top of the shell. All boiler should have at least two safety valves.

The safety valve may be classified as

1) Dead weight safety valve

2) Lever safety valve

3) Spring loaded safety valve

4) High steam and low steam water safety valve

BOILER ACCESSORIES

FEED PUMP Function To feed the water into the boiler through the feed

check valve. It is used to deliver feed water to the boiler under

pressure. It is a device of boiler use to supply proper amount of

water at least equal to that evaporated in the boiler. These pumps are classifies as

1) Reciprocating pumps – simplex, duplex, triplex

2) Rotory pump

3) Centrifugal pump

FEED WATER HEATERS FUNCTION To increase the temperature of the feed water

before it enters into the boiler. Feed water heaters can be classified based on

heat utilized for heating feed water

I. Economiser

II. Exhaust steam feed water heater

ECONOMISER It is a device in which the

waste heat of flue gases is utilised for heating the feed water.

Function To increase the

temperature of feed water using waste heat from the exhaust steam from boiler is utilised for heating the feed water.

EXHAUST STEAM FEED WATER HEATER

It is a device in which the heat from the exhaust steam or steam from boiler is utilised for heating the feed water.

Function To increase temperature

of feed water using heat from exhaust steam of steam turbine or steam from boiler.

SUPERHEATER Function To increase the temperature of

the steam above its saturation point.

The steam generated above the surface of water is always wet.

The main negative effect of supplying wet steam to steam turbine or steam engine are errosion of turbine blades, pipes etc., and condensetion losses occurs.

Therefore steam must be superheated before supplying to steam turbine or steam engine.

STEAM SEPARATOR Function To remove the suspended

water particles from the steam. Steam is collected from the

boiler may be wet, dry or superheated, but many case steam becomes wet due to loss of heat during passing in steam pipe.

The use of wet steam in a engine or turbine is not economical.

So there is need to seperate the water particles from the steam.

STEAM TRAP

Function To drain away

automatically the condensed steam from steam pipes, steam jackets and steam seperators without permitting any steam to escape.

AIR PREHEATER

Function To increase the

temperature of air before it supply to the furnace using heat from flue gases passing through chimney.

DRAUGHT SYSTEM

It is a pressure difference required to maintain constant flow of air to discharge the exhaust gases through the chimney to atmosphere.

Function Draught system creates pressure difference to introduce required

quality of air to the grate for combustion of fuel and to carry away the burned product of combustion and discharge to atmosphere.

Classification

I. Natural draught – chimney

II. Artificial draught – 1)Steam jet = a)Induced fan

b)Forced fan

2)Mechanical = a)Induced fan

b)Forced fan

c)Balanced(induced & forced fan)

THANK

YOU