Boilers report

Brief Introduction on boilers in detail
R.K.JAIN

TABLE OF CONTENTS
1) PREFACE
2) BOILERS
3) PURPOSEOF BOILERS
4) HOW DOES A BOILER WORKS
5) CLASSIFICATION OF BOILERS
6) BOILER MOUNTINGS
7) BOILER ACCESSORIES
8) BOILER MOUNTINGS FOR CONTROL
9) BOILERS TERMS
10) CONCLUSIONS AND
RECOMMENDATIONS

BOILERS
A Closed VesselIn Which Steam Is Produced FromWater By Combustion Of Fuel.
A Boier May Be Defind As A Closed Vessel In Which Steam Is Produced From
Water By Combustion Of Fuel.
Transfer Heat From A Fuel Source (Oil, Gas, Coal) Into Steam.
A Boiler Is A Closed Vessel In Which Water Or Other Fluid Is Heated. The Fluid
Does Not Necessarily Boil. (In North America The Term "Furnace" Is Normally
Used If The Purpose Is Not Actually To Boil The Fluid.)
The Heated Or Vaporized Fluid Exits the Boiler For Use In Various Processes Or
Heating Applications, Including Central Heating, Boiler-Based Power
Generation, Cooking, And Sanitation.

PURPOSE OF BOILERS
For Generating Power In Steam Engines Or Steam Turbines.
In Textile Industries For Sizing And Bleaching.
All PurposeBoiler Treatment Is Excellent For Cleaning And Conditioning Steam
And Hot Water Boilers. ALL PURPOSEBOILERTREATMENT Removes Sludge And
Scale, And Inhibits Corrosion On AllMetal Surfaces InsideTheBoiler And Pipes.
Prevents Oxygen Pitting And Formation Of Lime Scale; Eliminates Surging And
Foaming And Controls Ph Of Boiler Water. All PurposeBoiler Treatment Helps In
Increasing Boiler Efficiency And Decreasing Fuel Consumption.

How does a boiler work?
Closed system: when 100% of the steam produced is returned to be reused.
Open system: a system that does not return the condensate.
The boiler usually sits on top of a burner in which fuel is burned to produce heat. The
fuel produces the heat, the water or steam in the boiler is used to distribute the heat
through the house usually via pipes and radiators.
The most common fuel for boilers in the United States today is natural gas which is
usually piped directly into the house from a pipeline that runs under the street or road. In
rural areas not served by natural gas lines the most common fuel for boilers is propane
gas which is kept in a large tank in the yard and piped into the house. Propane is
usually more expensive than natural gas.
In some areas of the US mainly New England there are some boilers that are heated by
fuel or heating oil. Outside of the Northeast oil fired boilers are actually very rare. Many
oil fired boilers have been converted to burn natural gas or propane. The reason natural
gas and propane are more popular is that they are much cheaper fuels.
There are also a small number of boilers around that burn other fuels. Before Word War
II many boilers burnt coal. Today, some people particularly in rural areas burn wood
because it is often cheaper than natural gas or propane. There are also boilers that burn
other more exotic fuels such as waste oil, wood pellets and even corn cobs.
Anybody who has a hot water or steam heating system in their home needs to know
how a boiler works. The boiler is the most important part of a steam or hot water heating
system because it is what actually provides the heater.
A boiler is defined as “a closed vessel in which water or other liquid is heated, steam or
vapor is generated, steam is superheated, or any combination thereof, under pressure
or vacuum, for use external to itself, by the direct application of energy from the
combustion of fuels, from electricity or nuclear energy.

Classification of Boilers:
Boilers may be classified according to the following-
1. Relative position of Hot gases and Water
a) Fire tube boiler:
The hot gases passes through the tubes that are surrounded by water. Fire tube
boilers are also known by certain common names.
i) Horizontal return tubular
ii) Locomotive fire box
iii) Scotch marine and
iv) Vertical tubular
The combustion gases pass inside boiler tubes, and heat is transferred to water
on the shell side.

b) Water tube Boiler:
The water passes through the tubes and the hot gases produced by
combustion of fuel, flow outside. This type of Boilers designated by the following
common names:
i) Babcock and Wilcox Boiler (straight but inclined tubes which connect the
headers).
ii) Stirling Boiler (multitubular boiler having bent tubes that connect boiler
drums to headers).
Boiler water passes through the tubes while the exhaust gases remain in the shell
side, passing over the tube surfaces.

Boiler Mountings
The necessary devices installed or mounted for the safety of boiler and its control
are called boiler mountings.
Boiler mountings are the machine components that are mounted over the body
of the boiler itself for the safety of the boiler and for complete control of the
process of steam generation.
Various boiler mountings are as under:
1) Pressure gauge
2) Water Level Indicator
3) Fusible plug
4)Safety Valve
i) Lever Safety Valve
ii) Spring Loaded safety Valve
5) Steam stop valve
6) Feed check valve
7) Blow off cock

Bourdon's pressure gauge.
Function:
1.To record the steam pressure at which the steam is generated in the boiler.
2. A bourdon pressure gauge in its simplest form consists of elliptical elastic tube
bent into an arc of a circle.
3. This bent up tube is called as BOURDON’S tube.
4. One end of tube gauge is fixed and connected to the steam space in the boiler.
The other end is connected to a sector through a link.
Water Level Indicator
• The function of water level indicator is to indicate the level of water in the boiler
constantly.
• It is also called water gauge.
• Normally two water level indicators are fitted at the front end o
Fusible plug
• Function: To extinguish fire in the event of water level in the boiler shell falling
below certain specified limit.
• It protects fire tubes from burning when the level of the water in the water shell
falls abnormally low and the fire tube or crown plate which is normally submerged
in the water, gets exposed to steam space which may not be able to keep it cool.
• It is installed below boiler's water level.
• When the water level in the shell falls below the top of the plug, the steam cannot
keep it cool and the fusible metal melts due to over heating. Thus the copper plug
drops down and is held within the gunmetal body by the ribs. Thus the steam space
gets communicated to the firebox and extinguishes the fire. Thus damage to fire
box which could burn up is avoided.
• By removing the gun metal plug and copper plug the fusible plug can be put in
position again by interposing the fusible metal usually lead or a metal alloy.
safety valve :

Function : The function of safety valve is to release the excess steam when the
pressure of steam inside the boiler exceeds the rated pressure.
There are 4 types of safety valves:
Lever Safety Valve
The disadvantage of this valve is that it admits of being tempered with, and the
effect of a small addition to the weight is magnified considerably in its action on the
value.
Spring Loaded safety Valve
• For locomotives and marine engines both the lever and dead weight types are
unsuitable for obvious reasons, and the valve must be spring loaded, as such valve
is unaffected by vibration or deviation from the vertical.
• Disadvantage :
One disadvantage of this valve is that the load on the valve increases as the valve
lifts, so that pressure required just to lift the valve is less than that required to
open it fully.
iii)Dead Weight Safety Valve
• It is mainly used for low pressures, low capacity, stationary boilers of the Cornish
and Lancashire types.
• Merits:
1)Simplicity of design
2)Gives quite a satisfactory performance during operation.
3)It cannot be easily tempered from the pressure adjustment view.
• Demerits:
1)Unsuitable for use on any boiler where extensive vibration and movement are
experienced( e.g. locomotive and marine work).

2)It is not suitable for high pressure boilers because a large amount of weight is
required to balance the steam pressure.
iv) High steam and low water safety valve
• It serves the following purposes.
The steam automatically escapes out when the level of water falls below a certain
level.
It automatically discharges the excess steam when the pressure of the steam rises
above a certain pressure.
Use : It is generally used on Lancashire or Cornish boiler. It cannot used in mobile
boilers.
Steam stop valve
• A valve is a device that regulates the flow of a fluid (gases, fluidized solids,
slurries, or liquids) by opening, closing, or partially obstructing various
passageways.
• Function: to shut off or regulate the flow of steam from the boiler to the steam
pipe or steam from the steam pipe to the engine.
• When the hand wheel is turned, the spindle which is screwed through the nut is
raised or lowered depending upon the sense of rotation of wheel. The passage for
flow of steam is set on opening of the value.
Feed check valve
Function: The function of a feed check valve is to control the supply of water
to the boiler and to prevent the escaping of water from the boiler when the pump
pressure is less or pump is stopped.
i) To allow the feed water to pass into the boiler.
ii) To prevent the back flow of water from the boiler in the event of the failure of
the feed pump.
The feed check valve is fitted in the water space of the boiler slightly below the
normal level of the water.

Blow off cock
• Function: To drain out the water from the boiler for internal cleaning, inspection,
repair or other purposes.
• It may discharge a portion of water when the boiler is in operation to blow out
mud, scale or sediments, periodically.
• It is fitted on the boiler shell directly or to a short branch pipe at the lowest part
of the water space.
Boiler Accessories
The Devices Which Are Installed In The Boiler For Their Efficient Operation And
Smooth Working Are Called Boiler Accessories.

Boiler Mountings for safety:
1. Two water level indicators – 2

2. Two safety valves.
3. Combined high steam and low water safety valve.

4. Fusible plug.
Boiler Mountings for control:
1. Pressure gauge

2. Feed check valve
3. Blow-off cock

4. Man hole and mud hole
Boilers Terms
Shell: Consists Of One Or More Steel Plates Bent Into A Cylindrical Form And
Riveted Or Welded Together. The Shell Ends Are Closed With End Plates.
Setting: The Primary Function Of Setting Is To Confine Heat To The Boiler And
Form A Passage For Gases. It Is Made Of Brick Work And May Form The Wall Of
The Furnace And Combustion Chamber.
Grate: It Is A Platform In The Furnace Upon Which Fuel Is Burnt.
Furnace: ItIs The Chamber Formed By The Space Above The Grate And Below The
Boiler Shell, In Which Combustion Takes Place.
Water Space And Steam Space: The Volume Of The Shell That Is Occupied By The
Water Is Termed As Water Space While The Entire Shell Volume Less The Water
And Tubes Is Called Steam Space.
Mountings: The Items Which Are Used For Safety Of Boiler Are Called Mountings.
Accessories: The Items Which Are Used For Increasing The Boiler Efficiency Are
Called Accessories.
Water Level: The Level At Which Water Stands In The Boiler Is Called Water Level.
Refractory: Insulation Material Used For Lining Combustion Chamber.
Foaming: Formation Of Steam Bubbles On The Surface Of Boiler Water Due To
High Surface Tension Of Water.

Scale: A Deposit Of Medium Due To Extreme Hardness Occurring On The Water
Heating Surfaces Of Boiler Because Of An Undesirable Condition In The Boiler
Water.
Blowing Off: The Removal Of Mud And Other Impurities Of Water From The
Lowest Part Of The Boiler. Accomplished With The Help Of Blow Off Cock Or
Valve.
Lagging: Insulation Wrapped On The Outside Of The Boiler Shell Or Steam Piping.
Conclusions And Recommendations
Conclusions
The Ultimate Choice Concerning The Installation And Operation Of A Cogeneration
System Is Neither A Simple NorEasy One. There Are Many Factors That Affect Such A
Decision And Each Of These Must Be Considered Before An Educated Decision Can
Be Made.
First, The Nature Of A Given Facility's Operation Must Be Studied. If The Facility
Does Not Have Similar Electrical And Thermal Loads, Then A Cogeneration System
May Not Be Well Suited. Also, If Either Of The Loads Is Highly Transient In Nature,
Specific And Detailed Analysis Must Be Performed Concerning The Types Of
Equipment Capable Of Following Such Loads.
Fuel Availability Affects The Type Of Cogeneration System Selected. The Nature Of
The Industry Choosing To Cogenerate Will Often Determine The Fuel Type, And
Thereby The Cogeneration System. Pollution Concerns Must Be Considered As Well.
States Are Beginning To Heavily Regulate Industrial Emissions. Clean Burning Fuels,
Either Natural Gas Or Light Grade Fuel Oils, Will Often Be Required In These States.
Cogeneration Systems Which Most Effectively Utilize These Fuels Will Probably
Prove To Be The Most Economically Attractive.
The Base System Analyzed In The Theoretical Analysis Consisting Of A Gas Fired
Boiler With The Purchase Of Utility Electricity Is Typical Of The Systems Currently
Installed In Many Facilities Operating Today. The Operating Cost Of The Gas Boiler
System Was Used To Normalize The Operating Cost Of All The Other Systems. The
Results Could Then Be Directly Compared. As Electricity Becomes More Expensive
In Relation To Gas, The Electrical Boiler System Quickly Became Too Expensive For

Further Consideration. Unless Specific Industrial Processes Require An Electric
Boiler, The Electric Boiler System Should Not Be Used.
Of The 5 Systems Considered, The Reciprocating Engine System Returned The
Highest Fuel-To-Electrical Efficiency. For A Given Set Of Operational Parameters,
The Return On This System From Electrical Savings Will Be Greatest. However, The
Quantity And Thermal Quality Of The Heat Available For Recovery Is Much Lower
Than The Gas Turbine And Steam Turbine Systems Since A Considerable Portion Of
The Heat Exits In The Coolant System.
For Smaller Applications Or Applications With Transient Load Profiles, The
Reciprocating Engine Is Well Suited. Packaged Cogeneration Systems With
Reciprocating Engines As Prime Movers Are Commonly Available In A Wide Array
Of Sizes. These Systems Can Be Quickly And Easily Installed With A Minimum Of
On-Site Engineering.
The Steam Turbine System Had The Lowest Fuel-To-Electrical Efficiency Of The
Systems Considered. Steam Turbines Are Best Suited For Systems With A High
Thermal-To-Electrical Usage Ratio. Steam Turbines Are Generally Inexpensive And
Available In Many Sizes. For Facilities That Already Generate High Pressure Steam,
Steam Turbines Can Be Used To Replace Pressure Reducing Valves For The
Recovery Of Free Electricity. This Electricity Is Available Because Many Facilities
Generate Steam At A Higher Than Required Pressure Then Throttle The Steam Down
To A Lower Delivery Pressure. Throttling The Steam In This Manner Wastes
Valuable Energy That Can Be Recovered By A Steam Turbine.
The Gas Turbine Cogeneration System Had Close To The Same Fuel-To-Electrical
Efficiency As The Reciprocating Engine System, But Because The Thermal Energy
Exits At Such A High Temperature It Is Much More Easily Recovered. If Required,
The Exhaust May Be Used As Combustion Air For Further Firing In A Hrsg Due To
The High Oxygen Content Of The Gas Turbine Exhaust. The Gas Turbine Has As
Long A Life Span As Any System Considered And The Maintenance And
Supervision Costs Are Low. Also, Because Gas Turbine Generator Systems Come
Prepackaged (For Smaller Sized Systems), Installation Expenses Are Relatively Low.
Based On The Energy Usage Characteristics Of The Georgia Tech Campus, A Gas
Turbine Cogeneration System Was Chosen For Further Study. The Magnitude Of The
Electrical Demand Exceeds That Generally Taken As A Maximum For Reciprocating
Engine Systems (~3 Mw), And The Low Thermal-To-Electrical Demand Of The
Campus Would Severely Limit The Amount Of Electricity Available From A Steam
Turbine System Sized To Meet The Campus Thermal Load.

Four Sizes Of Gas Turbine Systems Were Chosen For The Study With Each Turbine
Operated Under Three Different Operational Strategies. A 10 Mw, 7.5 Mw, 5 Mw,
And 4 Mw Were Each Used For Analysis. The 10 Mw Unit Is The Largest Gas
Turbine Generator That Could Be Operated Under A Base Load Strategy, And The 4
Mw Unit Is The Smallest Turbine Size Before The Price For Turbines On A Dollar
Per Kw Basis Becomes Prohibitive.
The First Of The Three Operational Strategies, The Base Load Strategy, Requires
That The Turbines Operate Fully Loaded At All Times. The Exhaust Is Routed To A
Heat Recovery Boiler Where It Produces Steam. The Steam Is Used To Meet The
Campus Thermal Load. Any Shortfall In Steam Is Met By The Current Central Boiler
System
The Peaking Strategy Requires That The Turbines Operate Only When The Cost For
Rtp Electricity Exceeds A Given Value. This Value Is Calculated By Determining
The Cost For Producing One Kw Of Electricity Using The Gas Turbine Cogenerator
For A Given A Cost Of Natural Gas. If The Rtp Price For A Given Hour Exceeds The
"Break Even" Cost, The Generator Is Turned On. Otherwise, The Generators Are Not
Operated. As In The Base Load Strategy, The Exhaust Is Used To Meet The Campus
Thermal Load.
Finally, The Thermal Following Strategy Requires That The Gas Turbines Operate
Such That The Recovered Thermal Energy Taken From The Hrsg Exactly Meets The
Thermal Load Of The Campus. Whatever Electricity That Can Be Generated Under
This Operational Strategy Is Used To Offset Electrical Purchases From The Electric
Utility. During The Winter Months, The Turbines Will Be Unable To Meet The
Campus Thermal Load. The Currently Installed Boiler System Will Make Up The
Shortfall.
From The Economic Analysis Performed, The Base Load Strategy Returned The Best
Economic Results. Any Of The Turbine Sizes Would Have A Simple Payback Of
Less Than Six Years, A Value Which Seems Reasonable For The Large Scale Nature
Of A Cogeneration Project. The Turbines Operate At Full Load, Which Minimizes
Maintenance And Supervision Costs, Maximizes The Life Span Of The Unit, And
Returns The Best Fuel-To-Electrical Efficiency.
The 5 Mw Gas Turbine Returned The Best Economic Results. The Actual Payback
Was 4.1 Years, Or A 36% Return On Investment Assuming A 15 Year Life Energy
Cost Escalation Of 10%, A Very Attractive Number. The 5 Mw Unit Benefits From A
Relatively Low Installed Cost And A Better Than Average Thermal Recovery.

The Other Two Operational Strategies Returned Less Attractive Economic Results.
The Peaking Strategy Suffered From Both Low Operating Hours And Poor Benefits
Gained From The Electrical Rate Structure. The Cbl Cannot Be Lowered Unless The
Gas Turbine Is Operated Continuously. The Peaking Turbine Offsets Cheaper Rtp
Electricity. Also, The Peaking Turbines Only Operate For 370 Hours Per Year. These
Two Factors Combine To Return A Simple Payback Of Approximately 30 Years For
Each Of The Four Turbine Sizes Chosen.
The Final Operational Strategy, Thermal Following, Performed Better Than The
Peaking Strategy, Yet Not As Well As The Base Loading Strategy. Due To The
Increased Load Factors Of The Smaller Turbines, The Payback For The Thermal
Following Strategy Improved As The Turbine Size Decreased. In Fact, At 2.3 Mw,
The Gas Turbine Reaches A Completely Loaded Condition, Meaning It Is Fully
Loaded Both Thermally And Electrically. But, The Increasing Cost On A Dollar Per
Kw Basis Of The Smaller Turbines Increases Their Payback.
Recommendations
Based Upon The Economic Analysis Of The Various Turbine Sizes And Operational
Strategies, A Base Loaded 5 Mw Turbine Would Prove To Be An Economically Viable
Choice For The Georgia Tech Campus. The Payback Is Only 4 Years. The Gas Turbine
Cogeneration System Is Small, With A Long Life Span And Low AssociatedCosts Such
As Maintenance And Engineering Supervision. Some Of The Existing Campus
Equipment Would Need To Be Removed Before The Turbine Could Be Installed Inside
The Existing Building, But If This Is Undesirable, Almost All Gas Turbine Generator
Sets Come With Full Environmental Protection And Sound Attenuation For Outside
Installation.
Of Course There Are Other Considerations Besides Just Economic Ones. Georgia
Power Has A Considerable Amount Of Interest In Maintaining Georgia Tech As A
Power Customer. Georgia Power Has Been A Long Time Supporter Of Georgia Tech
And The Political Influence They Wield Within The State Would Act To Limit The
Attractiveness Of A Cogeneration System On Campus. It Is Not Within The Scope Of
This Project To Address These Types Of Concerns, But They Should Be Considered.

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