Edited by J.B. Kitto and S.C. Stultz

The Babcock & Wilcox Company
Steam 41
Copyright © 2005 by
The Babcock & Wilcox Company
a McDermott company
Forty-first edition
First printing
All rights reserved.
Reproduction or translation of any part of this work in any form or by any means beyond
that permitted by the 1976 United States Copyright Act without the permission of the
copyright holder is unlawful. Requests for permission or further information should be
addressed to: STEAM, The Babcock & Wilcox Company, 20 S. Van Buren Avenue, P.O. Box
351, Barberton, Ohio, U.S.A. 44203-0351.
Disclaimer
The information contained within this book has been obtained by The Babcock
& Wilcox Company from sources believed to be reliable. However, neither The
Babcock & Wilcox Company nor its authors make any guarantee or warranty,
expressed or implied, about the accuracy, completeness or usefulness of the
information, product, process or apparatus discussed within this book, nor
shall The Babcock & Wilcox Company or any of its authors be liable for error,
omission, losses or damages of any kind or nature. This book is published
with the understanding that The Babcock & Wilcox Company and its authors
are supplying general information and neither attempting to render engineering
or professional services nor offering a product for sale. If services are desired,
an appropriate professional should be consulted.
Steam/its generation and use. 41st edition.
Editors: John B. Kitto and Steven C. Stultz.
The Babcock & Wilcox Company, Barberton, Ohio, U.S.A.

2005
Includes bibliographic references and index.
Subject areas: 1. Steam boilers.
2. Combustion – Fossil fuels.
3. Nuclear power.
The editors welcome any technical comments, notes on inaccuracies, or thoughts on important omissions. Please direct these to the
editors at
© 1955, 1960, 1963, 1972, 1975, 1978, 1992, The Babcock & Wilcox Company. All rights reserved.
ISBN 0-9634570-1-2
Library of Congress Catalog Number: 92-74123
ISSN 1556-5173 Printed in the United States of America.
ii
The Babcock & Wilcox Company
Steam 41 iii
Steam/its generation and use is the longest continuously published engineer-
ing text of its kind in the world. It has always been, and continues to be, writ-
ten and published by The Babcock & Wilcox Company, the Original, head-
quartered in Barberton, Ohio, and incorporated in Delaware, The United States
of America.
Steam, Edition: 41
The Babcock & Wilcox Company
Steam 41iv
The Babcock & Wilcox Company
The Babcock & Wilcox Company
Steam 41 v
Preface
Dear Reader:
The founders of our company, George Babcock and Stephen Wilcox, invented
the safety water tube boiler. This invention resulted in the commercialization
of large-scale utility generating stations. Rapid increases in generation of safe,

dependable and economic electricity literally fueled the Industrial Revolution
and dramatically increased the standard of living in the United States and
industrialized economies worldwide throughout the twentieth century.
Advancements in technology to improve efficiency and reduce environmen-
tal emissions have continued for nearly 140 years, creating a unique and valu-
able body of applied engineering that represents the individual and collective
contributions of several generations of employees. As in other areas of science
and engineering, our field has continued to evolve, resulting in an extensive
amount of new material that has been incorporated into our 41st edition of
Steam/its generation and use. This edition required an extensive amount of
personal time and energy from hundreds of employees and reflects our com-
mitment to both our industry and our future.
Today it is clear that the challenge to generate power more efficiently from
fossil fuels, while minimizing impacts to our environment and global climate,
will require significant technological advancements. These advances will re-
quire creativity, perseverance and ingenuity on the part of our employees and
our customers. For inspiration, we can recall the relentless drive and imagi-
nation of one of our first customers, Mr. Thomas Alva Edison. For strength,
we will continue to embrace our Core Values of Quality, Integrity, Service and
People which have served us well over our long history as a company.
I thank our shareholders, our employees, our customers, our partners and
our suppliers for their continued dedication, cooperation and support as we move
forward into what will prove to be a challenging and rewarding century.
To help guide us all along the way, I am very pleased to present Edition: 41.
David L. Keller
President and Chief Operating Officer
The Babcock & Wilcox Company
The Babcock & Wilcox Company
Steam 41vi
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii to ix

System of Units: English and Système International . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
Editors’ Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Introduction to Steam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intro-1 to 17
Selected Color Plates, Edition: 41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plates 1 to 8
Section I – Steam Fundamentals
Chapter 1 Steam Generation – An Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 to 1-17
2 Thermodynamics of Steam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 to 2-27
3 Fluid Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 to 3-17
4 Heat Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 to 4-33
5 Boiling Heat Transfer, Two-Phase Flow and Circulation . . . . . . . . . . . . . . 5-1 to 5-21
6 Numerical Modeling for Fluid Flow, Heat Transfer, and Combustion . . . . 6-1 to 6-25
7 Metallurgy, Materials and Mechanical Properties . . . . . . . . . . . . . . . . . . . . 7-1 to 7-25
8 Structural Analysis and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 to 8-17
Section II – Steam Generation from Chemical Energy
Chapter 9 Sources of Chemical Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 to 9-19
10 Principles of Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 to 10-31
11 Oil and Gas Utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1 to 11-17
12 Solid Fuel Processing and Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1 to 12-19
13 Coal Pulverization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1 to 13-15
14 Burners and Combustion Systems for Pulverized Coal . . . . . . . . . . . . . . . 14-1 to 14-21
15 Cyclone Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1 to 15-13
16 Stokers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1 to 16-11
17 Fluidized-Bed Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1 to 17-15
18 Coal Gasification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1 to 18-17
19 Boilers, Superheaters and Reheaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-1 to 19-21
20 Economizers and Air Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-1 to 20-17
21 Fuel Ash Effects on Boiler Design and Operation . . . . . . . . . . . . . . . . . . . . 21-1 to 21-27
22 Performance Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-1 to 22-21
23 Boiler Enclosures, Casing and Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . 23-1 to 23-9
24 Boiler Cleaning and Ash Handling Systems . . . . . . . . . . . . . . . . . . . . . . . . 24-1 to 24-21

25 Boiler Auxiliaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-1 to 25-23
Section Ill – Applications of Steam
Chapter 26 Fossil Fuel Boilers for Electric Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-1 to 26-17
27 Boilers for Industry and Small Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27-1 to 27-21
28 Chemical and Heat Recovery in the Paper Industry . . . . . . . . . . . . . . . . . 28-1 to 28-29
29 Waste-to-Energy Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29-1 to 29-23
30 Wood and Biomass Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-1 to 30-11
31 Marine Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31-1 to 31-13
Table of Contents
The Babcock & Wilcox Company
Steam 41 vii
Section IV – Environmental Protection
Chapter 32 Environmental Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32-1 to 32-17
33 Particulate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33-1 to 33-13
34 Nitrogen Oxides Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34-1 to 34-15
35 Sulfur Dioxide Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35-1 to 35-19
36 Environmental Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36-1 to 36-15
Section V – Specification, Manufacturing and Construction
Chapter 37 Equipment Specification, Economics and Evaluation . . . . . . . . . . . . . . . . . 37-1 to 37-17
38 Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38-1 to 38-13
39 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39-1 to 39-19
Section VI – Operations
Chapter 40 Pressure, Temperature, Quality and Flow Measurement . . . . . . . . . . . . . . 40-1 to 40-25
41 Controls for Fossil Fuel-Fired Steam Generating Plants . . . . . . . . . . . . . . 41-1 to 41-21
42 Water and Steam Chemistry, Deposits and Corrosion . . . . . . . . . . . . . . . . . 42-1 to 42-29
43 Boiler Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43-1 to 43-17
Section VII – Service and Maintenance
Chapter 44 Maintaining Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44-1 to 44-21
45 Condition Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45-1 to 45-21
Section VIII – Steam Generation from Nuclear Energy

Chapter 46 Steam Generation from Nuclear Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . 46-1 to 46-25
47 Fundamentals of Nuclear Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47-1 to 47-15
48 Nuclear Steam Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48-1 to 48-15
49 Nuclear Services and Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49-1 to 49-21
50 Nuclear Equipment Manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50-1 to 50-13
Appendices
Appendix 1 Conversion Factors, SI Steam Properties and Useful Tables . . . . . . . . . . . T-1 to T-16
2 Codes and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1 to C-6
Symbols, Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S-1 to S-10
B&W Trademarks in Edition: 41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TM-1
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-1 to I-22
The Babcock & Wilcox Company
Steam 41
Steam/its generation and use is the culmination of the work of hundreds of B&W employees who have con-
tributed directly and indirectly to this edition and to the technology upon which it is based. Particular recogni-
tion goes to individuals who formally committed to preparing and completing this expanded 41st edition.
* The editors offer special acknowledgment to authors J.E. Granger and E.H. Mayer who passed away
during the preparation of Edition: 41.
Acknowledgments
viii
Editor-in-Chief/Project Manager
S.C. Stultz
Technical Editor/Technical Advisor
J.B. Kitto
Art Director/Assistant Editor
G.L. Tomei
Assistant Technical Editors
J.J. Gaidos
M.A. Miklic
Lead Authors

M.J. Albrecht
G.T. Bielawski
K.P. Brolly
P.A. Campanizzi
P.L. Cioffi
R.A. Clocker
P.L. Daniel
R.A. Detzel
J.A. Dickinson
W. Downs
D.D. Dueck
S.J. Elmiger
J.S. Gittinger
J.E. Granger*
G.R. Grant
G.H. Harth
T.C. Heil
D.A. Huston
B.J. Jankura
C.S. Jones
K.L. Jorgensen
J.B. Kitto
D.L. Kraft
A.D. LaRue
M.P. Lefebvre
P. L i
G.J. Maringo
W.N. Martin
E.H. Mayer*
D.K. McDonald

R.M. McNertney Jr.
J.E. Monacelli
T.E. Moskal
N.C. Polosky
E.F. Radke
K.E. Redinger
J.D. Riggs
D.E. Ryan
D.P. Scavuzzo
S.A. Scavuzzo
W.G. Schneider
T.D. Shovlin
T.A. Silva
B.C. Sisler
J.W. Smith
R.E. Snyder
W.R. Stirgwolt
J.R. Strempek
S.C. Stultz
J.M. Tanzosh
G.L. Tomei
D.P. Tonn
S.J. Vecci
P.S. Weitzel
R.A. Wessel
L.C. Westfall
P.J. Williams
The Babcock & Wilcox Company
Steam 41 ix
Primary Support Authors

S.A. Bryk
D.E. Burnham
D.S. Fedock
J.T. Griffin
B.L. Johnson
N. Kettenbauer
T.P. Kors
G.J. Lance
R.C. Lenzer
E.P.B. Mogensen
G.M. Pifer
K.J. Rogers
B.J. Youmans
Executive Steering Committee
B.C. Bethards
E.M. Competti
J.S. Kulig
D.C. Langley
J.W. Malone
M.G. Morash
R.E. Reimels
Production Group
J.L. Basar
L.A. Brower
P.L. Fox
L.M. Shepherd
Outside Support
P.C. Lutjen (Art)
J.R. Grizer (Tables)
The Babcock & Wilcox Company

Steam 41
To recognize the globalization of the power industry, the 41st edition of Steam
incorporates the Système International d’Unitès (SI) along with the contin-
ued use of English or U.S. Customary System (USCS) units. English units
continue to be the primary system of units with SI provided as secondary units
in parentheses. In some instances, SI units alone have been provided where
these units are common usage. In selected figures and tables where dual units
could detract from clarity (logarithmic scales, for example) SI conversions are
provided within the figure titles or as a table footnote.
Extensive English-SI conversion tables are provided in Appendix 1. This
appendix also contains a complete SI set of the Steam Tables, Mollier diagram,
pressure-enthalpy diagram and psychrometric chart.
The decision was made to provide exact conversions rounded to an appro-
priate number of figures. This was done to avoid confusion about the original
source values.
Absolute pressure is denoted by psi or kPa/MPa and gauge pressure by psig
or kPa/MPa gauge. The difference between absolute pressure and pressure
difference is identified by the context. Finally, in Chapters 10 and 22, as well
as selected other areas of Steam which provide extensive numerical examples,
only English units have been provided for clarity.
For reference and clarity, power in British thermal units per hour (Btu/h)
has typically been converted to megawatts-thermal and is denoted by MW
t
while megawatts-electric in both systems of units has been denoted by MW.
The editors hope that these conversion practices will make Steam easily usable
by the broadest possible audience.
System of Units
English and Système International
x
The Babcock & Wilcox Company

Steam 41
When we completed the 40th edition of Steam in 1992, we had a sense that
perhaps our industry was stabilizing. But activity has again accelerated. To-
day, efficiencies are being driven even higher. Emissions are being driven even
lower. Many current technologies are being stretched, and new technologies
are being developed, tested and installed. We have once again changed much
of Steam to reflect our industry’s activity and anticipated developments.
Recognizing the rich history of this publication, we previously drew words
from an 1883 edition’s preface to say that “we have revised the whole, and
added much new and valuable matter.” For this new 41st edition we can draw
from the 1885 edition to say “Having again revised Steam, and enlarged it by
the addition of new and useful information, not published heretofore, we shall
feel repaid for the labor if it shall prove of value to our customers.”
We hope this new edition is of equal value to our partners and suppliers,
government personnel, students and educators, and all present and future em-
ployees of The Babcock & Wilcox Company.
Editors’ Foreword
xi
The Babcock & Wilcox Company
Steam 41
Section I
Steam Fundamentals
Steam is uniquely adapted, by its availability and advantageous properties,
for use in industrial and heating processes and in power cycles. The funda-
mentals of the steam generating process and the core technologies upon which
performance and equipment design are based are described in this section of
eight chapters. Chapter 1 provides an initial overview of the process, equip-
ment and design of steam generating systems, and how they interface with
other processes that produce power and use steam. This is followed by funda-
mental discussions of thermodynamics, fluid dynamics, heat transfer, and the

complexities of boiling and steam-water flow in Chapters 2 through 5. New
Chapter 6 is dedicated to exploring the dramatic increase in the use of advanced
computational numerical analysis in the design of modern steam generators.
The section concludes with Chapters 7 and 8 discussing key elements of mate-
rial science and structural analysis that permit the safe and efficient design of
the steam generating units and components.
The Babcock & Wilcox Company
Steam 41
Section II
Steam Generation from
Chemical Energy
This section containing 17 chapters applies the fundamentals of steam gen-
eration to the design of boilers, superheaters, economizers and air heaters for
steam generation from chemical or fossil fuels (coal, oil and natural gas). As
discussed in Chapter 1, the fuel and method of combustion have a dramatic
impact on the size and configuration of the steam producing system. There-
fore, Chapters 9 and 10 begin the section by exploring the variety and charac-
teristics of chemical and fossil fuels, and summarize the combustion calcula-
tions that are the basis for system design.
The variety of combustion systems available to handle these fuels and the
supporting fuel handling and preparation equipment are then described in
Chapters 11 through 18. These range from the venerable stoker in its newest
configurations to circular burners used for pulverized coal, oil and gas, to flu-
idized-bed combustion and coal gasification. A key element in all of these sys-
tems is the control of atmospheric emissions, in particular oxides of nitrogen
(NO
x
) which are byproducts of the combustion process. Combustion NO
x
con-

trol is discussed as an integral part of each system. It is also discussed in Sec-
tion IV, Chapter 34.
Based upon these combustion systems, Chapters 19 through 22 address the
design and performance evaluation of the major steam generator heat trans-
fer components: boiler, superheater, reheater, economizer and air heater. These
are configured around the combustion system selected with special attention
to properly handling the high temperature, often particle-laden flue gas. The
fundamentals of heat transfer, fluid dynamics, materials science and struc-
tural analysis are combined to provide the tradeoffs necessary for an economi-
cal steam generating system design. The boiler setting and auxiliary equip-
ment, such as sootblowers, ash handling systems and fans, which are key ele-
ments in completing the overall steam system, conclude this section in Chap-
ters 23 through 25.
The Babcock & Wilcox Company
Steam 41
Section III
Applications of Steam
The six chapters in this section illustrate how the subsystems described in
Section II are combined to produce modern steam generating systems for spe-
cific applications. A number of steam generating unit and system designs for
various applications are described and illustrated.
Chapter 26 begins the section with a discussion of large fossil fuel-fired equip-
ment used to generate electric power. Both large and small industrial units, as
well as those for small electric power applications, are then described in Chap-
ter 27. The next four chapters address specialized equipment for specific appli-
cations. Unique designs for steam producing systems are used in pulp and paper
mills, waste-to-energy plants, biomass-fired units, and marine applications.
Biomass-fired systems in particular are receiving increased interest as renew-
able energy resources grow in importance.
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Steam 41
Section IV
Environmental Protection
Environmental protection and the control of solid, liquid and gaseous efflu-
ents or emissions are key elements in the design of all steam generating sys-
tems. The emissions from combustion systems are tightly regulated by local
and federal governments, and specific rules and requirements are constantly
changing. At present, the most significant of these emissions are sulfur diox-
ide (SO
2
), oxides of nitrogen (NO
x
), and fine airborne particulate. All of these
require specialized equipment for control.
Chapter 32 begins this section with an overview of current regulatory re-
quirements and overall emission control technologies. The chapter concludes
with a discussion of mercury emissions control which is expected to become an
integral part of overall plant multi-pollutant control strategy. Following this
overview, Chapters 33, 34 and 35 discuss specific equipment to control atmo-
spheric emissions of particulate, NO
x
and SO
2
respectively. The NO
x
discus-
sion focuses on post-combustion technologies; combustion-related control op-
tions are addressed in Chapter 11 and Chapters 14 through 18.
Finally, a key element in a successful emissions control program is mea-
surement and monitoring. Chapter 36 addresses a variety of issues and out-

lines a number of technologies for flue gas monitoring.
The Babcock & Wilcox Company
Steam 41
Section V
Specification, Manufacturing
and Construction
This section begins with an in-depth discussion of the specification, evalua-
tion and procurement process for large capital expense items. This includes
discussions about project scope, terms and conditions, and general bid evalua-
tion. Also discussed are power system economics, and procedures for the evalu-
ation of equipment characteristics in terms of justifiable expenditures. Ex-
amples and calculations are included for both utility and industrial units.
This is followed by a discussion of the manufacturing processes for fossil fuel-
fired equipment. Welding and metal removal techniques, as well as fabrica-
tion of the various components and component parts, are covered. Examina-
tion and quality control are also discussed. The section ends with a discussion
of various construction techniques, labor requirements, on-site considerations,
safety issues, and post-construction testing prior to unit startup.
The Babcock & Wilcox Company
Steam 41
Section VI
Operations
With proper design, manufacture and construction, modern steam generat-
ing systems are capable of operating efficiently for long periods of service.
However, successful operation requires adherence to basic operating principles.
These principles begin with the careful monitoring of operating conditions so
that a system functions within design limits. Chapter 40 describes the instru-
mentation for monitoring pressures, temperatures and flows – the key process
parameters. (Specialized instrumentation for environmental equipment is
covered in Section IV, Chapter 36.) These operating parameters then serve as

the inputs to the control system. The fundamentals of control theory and mod-
ern integrated control systems are reviewed in Chapter 41. These systems have
advanced rapidly during the past few decades to provide greater operator knowl-
edge and flexibility to optimize plant performance.
Successful long-term operation of steam producing systems requires care-
ful attention to water treatment and water chemistry control. Chapter 42 pro-
vides a discussion of water treatment practices from startup through opera-
tion and chemical cleaning. Drum and once-through boilers have different re-
quirements, and each boiler requires individual consideration.
General operating principles and guidelines outlined in Chapter 43 conclude
this section. Each steam generating system is unique and requires specific
operating guides. However, a number of general principles covering initial
operations serve as a basis.
The Babcock & Wilcox Company
Steam 41
Section VII
Service and Maintenance
This section describes the last element of a successful steam generating sys-
tem life cycle plan – service and maintenance.
As owners and operators of steam plants search for optimum performance,
efficiency, and life cycle for all equipment, issues of maintenance and avail-
ability have become increasingly important.
The section begins with a discussion of service and maintenance encoun-
tered with all plants, both utility and industrial. A well-crafted service and
maintenance program is essential in sustaining the availability of critical steam
generating assets and maximizing overall performance and output. Condition
assessment is then addressed with detailed discussion about examination tech-
niques, assessment of various components, and analysis techniques for deter-
mining remaining life. The effects of cycling operation are also addressed.
The Babcock & Wilcox Company

Steam 41
Section VIII
Steam Generation from
Nuclear Energy
Nuclear power generation provides a critical element in the energy supply
of virtually all developed nations today, and offers the promise to address grow-
ing power needs in an environmentally acceptable and safe manner in the fu-
ture. This section describes the application of steam generation fundamentals
to the design of nuclear steam supply systems (NSSS) in which steam is gener-
ated by heat released from nuclear fuels.
This section begins with an overview of nuclear installations, concentrating
on the pressurized water reactor. Principles of nuclear reactions and the nuclear
fuel cycle are then explored in Chapter 47. Chapter 48 is dedicated to nuclear
steam generators. Operating experience indicates that this component is a
particularly challenging and important part of the NSSS. As nuclear power
plants age, the steam generators are increasingly being replaced to optimize
plant performance and extend the operating plant life.
Chapter 49 explores the key service, maintenance and operating character-
istic of a nuclear steam system that can optimize life and performance. The
section concludes in Chapter 50 with an overview of the highly specialized
manufacturing requirements and capabilities that are necessary for success-
ful component fabrication.
The Babcock & Wilcox Company
Steam 41
Appendices
The Babcock & Wilcox Company
Steam 41 / Introduction to Steam Intro-1
Introduction to Steam
Throughout history, mankind has reached beyond
the acceptable to pursue a challenge, achieving sig-

nificant accomplishments and developing new tech-
nology. This process is both scientific and creative. En-
tire civilizations, organizations, and most notably, in-
dividuals have succeeded by simply doing what has
never been done before. A prime example is the safe
and efficient use of steam.
One of the most significant series of events shap-
ing today’s world is the industrial revolution that be-
gan in the late seventeenth century. The desire to gen-
erate steam on demand sparked this revolution, and
technical advances in steam generation allowed it to
continue. Without these developments, the industrial
revolution as we know it would not have taken place.
It is therefore appropriate to say that few technolo-
gies developed through human ingenuity have done
so much to advance mankind as the safe and depend-
able generation of steam.
Steam as a resource
In 200 B.C., a Greek named Hero designed a simple
machine that used steam as a power source (Fig. 1).
He began with a cauldron of water, placed above an
open fire. As the fire heated the cauldron, the caul-
dron shell transferred the heat to the water. When the
water reached the boiling point of 212F (100C), it
changed form and turned into steam. The steam
passed through two pipes into a hollow sphere, which
was pivoted at both sides. As the steam escaped
through two tubes attached to the sphere, each bent
at an angle, the sphere moved, rotating on its axis.
Hero, a mathematician and scientist, labeled the

device aeolipile, meaning rotary steam engine. Al-
though the invention was only a novelty, and Hero
made no suggestion for its use, the idea of generating
steam to do useful work was born. Even today, the basic
idea has remained the same – generate heat, trans-
fer the heat to water, and produce steam.
Intimately related to steam generation is the steam
turbine, a device that changes the energy of steam
into mechanical work. In the early 1600s, an Italian
named Giovanni Branca produced a unique invention
(Fig. 2). He first produced steam, based on Hero’s
aeolipile. By channeling the steam to a wheel that
rotated, the steam pressure caused the wheel to turn.
Thus began the development of the steam turbine.
The primary use of steam turbines today is for elec-
tric power production. In one of the most complex sys-
tems ever designed by mankind, superheated high-
pressure steam is produced in a boiler and channeled
to turbine-generators to produce electricity.
Fig. 1 Hero’s aeolipile.
The Babcock & Wilcox Company
Intro-2 Steam 41 / Introduction to Steam
Today’s steam plants are a complex and highly so-
phisticated combination of engineered elements. Heat
is obtained either from primary fossil fuels like coal,
oil or natural gas, or from nuclear fuel in the form of
uranium. Other sources of heat-producing energy in-
clude waste heat and exhaust gases, bagasse and bio-
mass, spent chemicals and municipal waste, and geo-
thermal and solar energy.

Each fuel contains potential energy, or a heating
value measured in Btu/lb (J/kg). The goal is to release
this energy, most often by a controlled combustion
process or, with uranium, through fission. The heat is
then transferred to water through tube walls and other
components or liquids. The heated water then changes
form, turning into steam. The steam is normally heated
further to specific temperatures and pressures.
Steam is also a vital resource in industry. It drives
pumps and valves, helps produce paper and wood
products, prepares foods, and heats and cools large
buildings and institutions. Steam also propels much
of the world’s naval fleets and a high percentage of
commercial marine transport. In some countries, steam
plays a continuing role in railway transportation.
Steam generators, commonly referred to as boilers,
range in size from those needed to heat a small build-
ing to those used individually to produce 1300 mega-
watts of electricity in a power generating station –
enough power for more than one million people. These
larger units deliver more than ten million pounds of
superheated steam per hour (1260 kg/s) with steam
temperatures exceeding 1000F (538C) and pressures
exceeding 3800 psi (26.2 MPa).
Today’s steam generating systems owe their de-
pendability and safety to the design, fabrication and
operation of safe water tube boilers, first patented by
George Babcock and Stephen Wilcox in 1867 (Fig. 3).
Because the production of steam power is a tremen-
dous resource, it is our challenge and responsibility to

further develop and use this resource safely, efficiently,
dependably, and in an environmentally-friendly manner.
The early use of steam
Steam generation as an industry began almost two
thousand years after Hero’s invention, in the seven-
teenth century. Many conditions began to stimulate
the development of steam use in a power cycle. Min-
ing for ores and minerals had expanded greatly and
large quantities of fuel were needed for ore refining.
Fuels were needed for space heating and cooking and
for general industrial and military growth. Forests were
being stripped and coal was becoming an important
fuel. Coal mining was emerging as a major industry.
As mines became deeper, they were often flooded
with underground water. The English in particular
were faced with a very serious curtailment of their
industrial growth if they could not find some economi-
cal way to pump water from the mines. Many people
began working on the problem and numerous patents
were issued for machines to pump water from the
mines using the expansive power of steam. The early
machines used wood and charcoal for fuel, but coal
eventually became the dominant fuel.
The most common source of steam at the time was
a shell boiler, little more than a large kettle filled with
water and heated at the bottom (Fig. 4).
Not all early developments in steam were directed
toward pumps and engines. In 1680, Dr. Denis Papin,
a Frenchman, invented a steam digester for food pro-
Fig. 3 First Babcock & Wilcox boiler, patented in 1867.

Fig. 4 Haycock shell boiler, 1720.Fig. 2 Branca’s steam turbine.
The Babcock & Wilcox Company
Steam 41 / Introduction to Steam Intro-3
cessing, using a boiler under heavy pressure. To avoid
explosion, Papin added a device which is the first safety
valve on record. Papin also invented a boiler with an
internal firebox, the earliest record of such construction.
Many experiments concentrated on using steam
pressure or atmospheric pressure combined with a
vacuum. The result was the first commercially suc-
cessful steam engine, patented by Thomas Savery in
1698, to pump water by direct displacement (Fig. 5).
The patent credits Savery with an engine for raising
water by the impellant force of fire, meaning steam.
The mining industry needed the invention, but the
engine had a limited pumping height set by the pres-
sure the boiler and other vessels could withstand.
Before its replacement by Thomas Newcomen’s engine
(described below), John Desaguliers improved the
Savery engine, adding the Papin safety valve and us-
ing an internal jet for the condensing part of the cycle.
Steam engine developments continued and the ear-
liest cylinder-and-piston unit was based on Papin’s
suggestion, in 1690, that the condensation of steam
should be used to make a vacuum beneath a piston,
after the piston had been raised by expanding steam.
Newcomen’s atmospheric pressure engine made prac-
tical use of this principle.
While Papin neglected his own ideas of a steam en-
gine to develop Savery’s invention, Thomas

Newcomen and his assistant John Cawley adapted
Papin’s suggestions in a practical engine. Years of ex-
perimentation ended with success in 1711 (Fig. 6).
Steam admitted from the boiler to a cylinder raised a
piston by expansion and assistance from a counter-
weight on the other end of a beam, actuated by the
piston. The steam valve was then closed and the steam
in the cylinder was condensed by a spray of cold wa-
ter. The vacuum which formed caused the piston to
be forced downward by atmospheric pressure, doing
work on a pump. Condensed water in the cylinder was
expelled through a valve by the entry of steam which
was at a pressure slightly above atmospheric. A 25 ft
(7.6 m) oak beam, used to transmit power from the
cylinder to the water pump, was a dominant feature
of what came to be called the beam engine. The boiler
used by Newcomen, a plain copper brewer’s kettle,
was known as the Haycock type. (See Fig. 4.)
The key technical challenge remained the need for
higher pressures, which meant a more reliable and
stronger boiler. Basically, evolution of the steam boiler
paralleled evolution of the steam engine.
During the late 1700s, the inventor James Watt
pursued developments of the steam engine, now
physically separated from the boiler. Evidence indi-
cates that he helped introduce the first waggon boiler,
so named because of its shape (Fig. 7). Watt concen-
trated on the engine and developed the separate steam
condenser to create the vacuum and also replaced
atmospheric pressure with steam pressure, improving

the engine’s efficiency. He also established the mea-
surement of horsepower, calculating that one horse
could raise 550 lb (249 kg) of weight a distance of 1 ft
(0.3 m) in one second, the equivalent of 33,000 lb
(14,969 kg) a distance of one foot in one minute.
Fig. 6 Newcomen’s beam engine, 1711.
Fig. 7 Waggon boiler, 1769.
Fig. 5 Savery’s engine, circa 1700.
The Babcock & Wilcox Company
Intro-4 Steam 41 / Introduction to Steam
Fire tube boilers
The next outstanding inventor and builder was Ri-
chard Trevithick, who had observed many pumping
stations at his father’s mines. He realized that the
problem with many pumping systems was the boiler
capacity. Whereas copper was the only material previ-
ously available, hammered wrought iron plates could
now be used, although the maximum length was 2 ft
(0.6 m). Rolled iron plates became available in 1875.
In 1804, Trevithick designed a higher pressure en-
gine, made possible by the successful construction of a
high pressure boiler (Fig. 8). Trevithick’s boiler design
featured a cast iron cylindrical shell and dished end.
As demand grew further, it became necessary to ei-
ther build larger boilers with more capacity or put up
with the inconveniences of operating many smaller
units. Engineers knew that the longer the hot gases were
in contact with the shell and the greater the exposed sur-
face area, the greater the capacity and efficiency.
While a significant advance, Newcomen’s engine

and boiler were so thermally inefficient that they were
frequently only practical at coal mine sites. To make
the system more widely applicable, developers of steam
engines began to think in terms of fuel economy. Not-
ing that nearly half the heat from the fire was lost
because of short contact time between the hot gases
and the boiler heating surface, Dr. John Allen may
have made the first calculation of boiler efficiency in
1730. To reduce heat loss, Allen developed an inter-
nal furnace with a smoke flue winding through the
water, like a coil in a still. To prevent a deficiency of
combustion air, he suggested the use of bellows to force
the gases through the flue. This probably represents
the first use of forced draft.
Later developments saw the single pipe flue replaced
by many gas tubes, which increased the amount of
heating surface. These fire tube boilers were essen-
tially the design of about 1870. However, they were
limited in capacity and pressure and could not meet
the needs that were developing for higher pressures
and larger unit sizes. Also, there was the ominous
record of explosions and personal injury because of
direct heating of the pressure shell, which contained
large volumes of water and steam at high tempera-
ture and pressure.
The following appeared in the 1898 edition of
Steam: That the ordinary forms of boilers (fire tube
boilers) are liable to explode with disastrous effect is
conceded. That they do so explode is witnessed by the
sad list of casualties from this cause every year, and

almost every day. In the year 1880, there were 170
explosions reported in the United States, with a loss
of 259 lives, and 555 persons injured. In 1887 the
number of explosions recorded was 198, with 652 per-
sons either killed or badly wounded. The average re-
ported for ten years past has been about the same as the
two years given, while doubtless many occur which are
not recorded.
Inventors recognized the need for a new design, one
that could increase capacity and limit the conse-
quences of pressure part rupture at high pressure and
temperature. Water tube boiler development began.
Early water tube design
A patent granted to William Blakey in 1766, cover-
ing an improvement in Savery’s steam engine, includes
a form of steam generator (Fig. 9). This probably was
the first step in the development of the water tube
boiler. However, the first successful use of a water
tube design was by James Rumsey, an American in-
ventor who patented several types of boilers in 1788.
Some of these boilers used water tube designs.
At about this time John Stevens, also an American,
invented a water tube boiler consisting of a group of
small tubes closed at one end and connected at the
Fig. 8 Trevithick boiler, 1804. Fig. 9 William Blakey boiler, 1766.