Effective August 9, 2007, this report has been made publicly available in accordance with Section 734.3(b)(3)
and published in accordance with Section 734.7 of the U.S. Export Administration Regulations. As a result of
this publication, this report is subject to only copyright protection and does not require any license agreement
from EPRI. This notice supersedes the export control restrictions and any proprietary licensed material notices
embedded in the document prior to publication.
Materials & Chemistry Report
August 2007
Dear Colleagues,
Welcome to the second issue of this newsletter, which features ongoing R&D activities and EPRI products and services designed to address
challenges common to conventional steam-electric plants, combined-cycle units, and future generation options. The Materials & Chemistry Report
emphasizes the following programs:
• Boiler Life and Availability Improvement (63)
• Boiler and Turbine Steam and Cycle Chemistry (64)
• Steam Turbines, Generators, and Balance-of-Plant (65)
• Fossil Materials and Repair (87)
• HRSG Dependability (88)
• Thermal Fatigue Cracking in the Waterwalls of Supercritical Boilers (171)
The last item is a new, crosscutting initiative involving Fossil Materials and Repair (87), Combustion Performance and NO x Control (71), and
other programs. Our comprehensive, issue-oriented approach will accelerate efforts to resolve a boiler tube failure mode thought to have been
addressed almost two decades ago with expanded adoption of oxygenated treatment (OT). Thermal fatigue cracking arises from both increased
waterwall temperatures and frequent and severe thermal transients. One cause of elevated temperatures today is the use of weld overlays to mitigate
fireside corrosion in existing boilers operating under staged combustion conditions. Others include the high heat fluxes and flame impingement
experienced in new supercritical units. Transients may be caused by slag shedding, sootblowers, water cannons/blowers, and other features.
Building on methodologies developed in 2006 for a supercritical unit, EPRI will create thermal fatigue management solutions for supercritical
and subcritical boilers, with and without low-NO x burners and overlays, and operating with OT or not. Products will include an overall guideline
encompassing root cause analysis and mitigation, plus optimal approaches
for nondestructive analysis, condition assessment, and remaining lifetime
prediction. This guideline is scheduled to be issued in 2009.
Preventing Failure: Modeling and Predicting Corrosion in
I would like to make note of several changes within EPRI’s Materials and
Low Pressure Steam Turbines..............................................2
Chemistry team. First, the contributions of Barry Syrett, who retired
On-Line Resources and Navigation Tips...............................5
at the end of 2006, are to be acknowledged. In more than 25 years of
Interacting Mechanisms: Creep-Fatigue Damage
work at EPRI, he managed R&D and provided application services to
Assessment....................................................................6
help mitigate corrosion problems in steam turbine, condenser, feedwater
heater,
flue-gas desulfurization, and other systems. Recent projects
Project Updates..............................................................9
addressing areas such as corrosion’s economic impacts on the electric
• Updated and Expanded Tube Failure Book
power industry and technologies for on-line corrosion monitoring and
• Modeling Deposition Phenomena in Drum-Type Boilers
control are expected to inform R&D planning and industry practice for
• Sensors for On-Line Monitoring of Steam-Phase Conditions
years to come.
• Turbine and Boiler Materials Development for Advanced
Second, I’m pleased to welcome Mia Caldwell to EPRI. She has a
Ultrasupercritical Coal Plants
background in electrochemistry and over 20 years of experience in
Technology Innovation.....................................................13
industry, research, and litigation support, spanning the scale from
• Nanocoating Development for Waterwall Protection
major plant power components to drug delivery micro-implants. She
• Advanced Feedwater Filtration Options
has extensive experience in corrosion monitoring, failure analysis, and
metallurgical and electrochemical aspects of corrosion and testing.
Featured Products............................................................15
She holds a BS in Chemical Engineering and MS and PhD degrees in
Upcoming Events............................................................16
Corrosion Science and Engineering.
Recent Deliverables.........................................................17
Finally, I would like to bring one additional change to your attention.
Supplemental Projects......................................................18
After more than two decades of collaborating through EPRI with
Materials & Chemistry Staff Experts....................................19
researchers and utility practitioners from around the world, I have
Contents
continued on page 2
13314787
Letter from Barry Dooley
Preventing Failure
continued from page 1
decided to move on as of mid-July 2007. Together,
we have made substantial progress in addressing the
root causes of availability losses attributable to boiler
and HRSG tube failure, steam turbine damage, cycle
chemistry, and other issues.
The article beginning on this page mentions one of my
favorite success stories, even though the industry has
not yet realized the benefits. Fundamental research
launched by EPRI in the early 1990s has substantially
advanced understanding and modeling of chemical
and physical processes that control corrosion in the
phase transition zone of steam turbines. Our work has
turned the conventional wisdom on its head: Shutdown
conditions, rather than operating environments, are the
primary determinant of blade and disk failure. When
turbines are shut down without adequate chemical
protection, initiation occurs and pitting damage
accumulates. If the damage initiation period can be
increased, then service life can be extended. In-depth
evaluation of a relatively simple shutdown protection
method is scheduled for 2007. By investing in basic,
first-principles study over a sustained period, EPRI,
its members, and its R&D partners have created new
knowledge that could save billions of dollars annually
across the worldwide steam turbine asset base.
There is much more to be achieved through international
collaboration. EPRI’s Materials and Chemistry group
will continue to represent a catalyst for coordinated,
timely, and effective response to both pressing and
emerging technical challenges. Thank you for your
interest in and support for our work.
Barry Dooley
Technical Executive, Materials & Chemistry����
Modeling and Predicting Corrosion
in Low-Pressure Steam Turbines
Most outage hours for steam turbines result from corrosion occurring in the phase
transition zone (PTZ) and leading to failure of low-pressure (LP) blades and disks.
To reduce maintenance costs and successfully avoid failures, unscheduled outages,
and the associated economic impacts, plant operators need predictive models that
reflect state-of-the-art knowledge of fundamental damage mechanisms and allow
for the use of on-line data to optimize service life and provide early warning of
particularly corrosive conditions.
Based on over a decade of strategic laboratory and field research led by EPRI,
damage initiation and propagation processes were characterized, providing
the foundation for development of increasingly deterministic models of stress
corrosion cracking (SCC) and corrosion fatigue (CF). In 2007, efforts to
transform the model into a user-friendly software tool have been initiated. Case
study validation activities are continuing, and a beta version of the “Corrosion in
the PTZ” code is scheduled for release in 2008.
“Our goal is to provide the industry with a tool for predicting damage initiation
and propagation and calculating failure probability in real time,” says Barry
Dooley, EPRI Technical Executive, Materials & Chemistry. “This will allow
operators to maintain proper cycle chemistry and, in the event of problems, to
implement timely countermeasures for decreasing failure probability.”
Model Development
In the early 1990s, EPRI catalyzed formation of an international R&D
collaboration to enhance basic understanding of chemical and physical processes
in the PTZ of LP turbines. By the end of the decade, key aspects of the PTZ
environment—moisture nucleation, early condensate composition, thickness and
composition of liquid films on blade surfaces, deposition of salts on blade surfaces,
and the effect of charged droplets and liquid films—had been comprehensively
described through laboratory, field, and theoretical research. Attendees at a
Corrosion of Steam Turbine Blading and Disks workshop reviewed the state of
Latest EPRI Steam Turbine-Generator
Notes Published
The latest issue of the Steam Turbine-Generator Notes
newsletter (1015268) is available, providing additional
detail on EPRI work under the Steam Turbine,
Generators, and Balance-of-Plant Program (65) as well
as the Nuclear Steam Turbine Initiative. The newsletter
includes an update on ongoing R&D activities and plans
through 2009, abstracts of 2006 products, an events
calendar, and other content. Visit www.epri.com to
download this issue.
knowledge and identified development of a modeling capability for predicting
the evolution of corrosion damage in PTZ components as the central thrust for
follow-on work.
In 2000, an initial mathematical model was developed for all stages in the
initiation and propagation of corrosion damage. Its architecture—still in use
today—includes an overall damage module and modules for pit and crack
nucleation, growth, repassivation, and transition. An additional environment
module addresses the role of liquid films on the blade and disk surface:
composition, conductivity, thickness, corrosion potential, temperature, and
mechanical conditions. Two key areas of data deficiency were identified during
initial model development, leading to the launch of further experimental work.
continued on page 3
Materials & Chemistry Report
13314787
August 2007
of pitting resistance, from most to least, among three common PTZ
materials: 17-4PH, 403SS, and A470/471.
Modeling and Predicting Corrosion in Low-Pressure Steam Turbines
continued from page 2
Findings from these experimental studies have been applied to further
develop the general theoretical basis underlying the PTZ model and
to describe in increasing detail the different corrosion events of defect
nucleation, active and passive pit growth, development of cracks,
and crack growth. In addition, the evolutionary history of the local
environment, the stress, the operating conditions, and their effects on
damage processes has been further characterized.
Model Features
Based on EPRI research, highly deterministic descriptions of all
stages in the initiation and propagation of SCC and CF damage in LP
turbines are available for the first time.1 These descriptions underlie
ongoing development and validation of the “Corrosion in the PTZ”
code. Damage function analysis (DFA) is being combined with Monte
Carlo simulation to provide powerful and unprecedented capabilities for
predicting the evolution of damage on blade and disk surfaces.
Nucleation of metastable pit
As a deterministic tool, all of the model’s predictions are constrained
Repassivation
by natural physical laws—for example, the conservation of an atomic
particle’s charge, mass, momentum, and energy—that represent a
Transition from metastable to
stable form
summation of all previous scientific experience. DFA defines the
accumulation of localized corrosion damage as a function of how many
pits and other corrosion events within a given depth range, as measured
in centimeters (cm), are found per unit area, as measured in cm 2. The
Growth of stable pit
damage function, f, has a dimension of number/cm3, analogous to the
concentration of a particle in a given medium. Each defect is treated
Repassivation
as a particle, k, moving in the x direction, perpendicular to the metal
surface, where x = 0 at the surface and at any other coordinate coincides
Transition from pit to corrosion
fatigue or stress corrosion cracking
Chemistry
with the depth of penetration into the metal.
Growth of corrosion crack
Loading
Basic knowledge of damage initiation and propagation processes
leading to corrosion in low-pressure steam turbines is supporting
development of a predictive model and mitigation measures.
Over the past several years, particular emphasis has been given to the
growth of pits and cracks in environments simulating those that exist in
the liquid films present on operating turbines. One study used a rotating
disk electrode to determine the corrosion potential and corrosion
currents characterizing dissolution in a pit for PTZ materials based on
the Tafel portions of the anodic and cathodic polarization curves. The
kinetic equations for hydrogen evolution and oxygen reduction—the
principal partial corrosion reactions—were developed. Visual and
microscopic examination of material surfaces also was used to quantify
pitting phenomena. Experimental data indicated the following order
Materials & Chemistry Report
13314787
Turbine Operation
Shutdown
Deposits and
Liquid Films
(No O2)
Deposits, Oxygen,
and Moisture
Pitting
Crevices
Pitting
Microcracks
Cyclic
Steady State
Corrosion Fatigue
SCC
No Loading
EPRI’s “Corrosion in the PTZ” code will integrate highly deterministic
descriptions of fundamental processes with advanced analytical
techniques to provide powerful and unprecedented capabilities for
predicting damage progression on blade and disk surfaces.
1 Detailed description of the EPRI code is abstracted from “The Prediction of Blade and Disc
Failures in Low Pressure Steam Turbines” by G. L. Engelhardt, D. D. Macdonald, and
R. B. Dooley (in 1014831, 2007).
continued on page 4
August 2007
No Shutdown Protection
Modeling and Predicting Corrosion in Low-Pressure Steam Turbines
continued from page 3
According to the law of mass conservation, the damage function may be
Probability of Failure
calculated based on three independent functions for each kind of particle,
or corrosion defect, k, plus the defect’s initial distribution, f k0(x):
1. The rate of particle introduction, that is, defect nucleation, nk
2. The particle flux density, that is, the growth or propagation rate of
the defect, jk
3. The rate of transition from one type of defect to another,
that is, pit repassivation and transition into cracks, Rk
The system is described in Equation 1 below and may be solved
subject to the appropriate boundary and initial conditions presented in
Equations 2 and 3:
Rk =
∂f k / ∂t + ∂jk / ∂x and k = 1, 2, …, K
Eq. 1
jk =
nk(t)
at x = 0, t > 0
Eq. 2
fk =
f k0(x)
at x > 0, t = 0
Eq. 3
Shutdown Protection
Oxygen Concentration, ppm
EPRI research has identified environmental conditions as the primary
determinant of turbine corrosion and failure, and initial modeling
has determined that measures to manage oxygen and chloride
concentrations during shutdown represent possible options for reducing
the probability of failure to essentially zero. Shutdown protection methods
are being evaluated in ongoing EPRI work.
To support DFA, EPRI has used the Point Defect Model (PDM) to
calculate the rate of pit nucleation, nk; the Coupled Environment Pitting
Model (CEPM) to determine the rate of pit or crack propagation, jk;
and the Coupled Environment Fracture Model (CEFM) and Coupled
Environment Corrosion Fatigue Model (CECFM) to calculate the rate
“The two-pronged analytical approach represents a major innovation,”
of pit repassivation to a stable form and pit transition to SCC and CF,
states Dooley. “We can now account for rare events in determining
Rk. In addition, generalized criteria have been developed to represent
the probability of failure, reducing the need for overly conservative
repassivation processes between damage states.
assessments.”
DFA characterizes damage in terms of the evolution of an ensemble of
Ongoing model validation activities are proceeding through case
corrosion events. In power plant environments, however, frequently a
studies, and corrosion tests are being conducted in liquid films and in
single pit or crack or only a few defects may be “alive” and propagating
crevice environments to determine the pitting potential on blade/disk
on a corroding metal surface, with all others repassivated. Under these
surfaces and support further refinements. Additional practical features
circumstances, the differential equations for the damage function, which
are also being incorporated, including the capability to input data on the
are equivalent to mass balance equations for an ensemble of particles
metallurgical, microstructural, and microchemical features of a surface,
within a given medium, lose their strict physical meaning. This is an
such as emergent precipitates or second-phase particles. This will allow,
important limitation for DFA because interactions among a few active
for the first time, the use of real-world surface structural features for the
defects can be critical to damage progression and failure.
deterministic prediction of localized corrosion damage.
For the EPRI model, Monte Carlo techniques have recently been
Plant Applications
developed to keep track of each stable pit or crack as it nucleates,
propagates, and repassivates or otherwise transitions to a new state.
EPRI’s commercial “Corrosion in the PTZ” code is scheduled for
Corrosion behavior is simulated based on kinetic equations for
beta-version release in 2008 to provide operators with unprecedented
hydrogen evolution and oxygen reduction at the metal surface and
analytical capabilities for analyzing and predicting damage initiation
within individual pits. This statistical simulation approach—used with
and propagation in LP steam turbines based on materials data and
spectacular success in other applications—allows the contributions
variables such as steam chemistry environment, liquid film composition
to localized corrosion behavior and damage progression arising from
and electrochemical properties, stress, temperature, and conductivity.
interactions among individual defects to be accounted for in an explicit
Innovative instrumentation being demonstrated in parallel work (see
manner. Monte Carlo algorithms and DFA thus work together to
pp. 10–11) will provide on-line data necessary for real-time damage
characterize the statistical behavior of individual defects within a
mitigation during turbine operations.
deterministic description of cumulative corrosion damage.
Materials & Chemistry Report
13314787
continued on page 5
August 2007
Modeling and Predicting Corrosion in Low-Pressure Steam Turbines
continued from page 4
Though not yet available in commercial form, EPRI’s PTZ model
“We don’t expect to have definitive guidance on this approach until field
already has yielded valuable conclusions. Results clearly indicate
validation studies are completed and worldwide experience is assessed,
that the service lifetime of blades and disks is extremely sensitive to
but this unexpected solution is exactly the type of practical intervention
environmental conditions, with failure due to SCC or CF dominated
strategy desired as an end result of fundamental mechanistic research
by initiation. Initiation occurs and pitting damage accumulates at
and analytical modeling.”
much faster rates when steam turbines are shut down without adequate
Lead Contacts
chemical protection, but in contrast, crack growth proceeds under strain
during turbine operations. Increasing the initiation period is the key to
David Gandy, davgandy@epri.com, 704.595.2198
extending service life, suggesting control of environmental conditions
Kevin Shields, kshields@epri.com, 410.374.0110
during shutdown as an effective approach for protecting against blade
and disk failure.
Key Resources
Numerous simulations have been performed to evaluate the potential
Development of Model to Predict Stress Corrosion Cracking and Corrosion
efficacy of alternative approaches to environmental modification for
Fatigue of Low Pressure Turbine Components (1012204), March 2007
shutdown protection. Results indicate that using dehumidified air during
Development of Code to Predict Stress Corrosion Cracking and Corrosion
shutdown to prevent liquid films from forming on metal surfaces will
Fatigue of Low Pressure Turbine Components: Electrochemical and
short-circuit the principal partial-corrosion reactions and dramatically
Corrosion Properties of Turbine Steels (1010184), December 2005
reduce the overall probability of failure. In early 2007, EPRI launched a
focused project to evaluate and demonstrate this promising approach in
Development of Code to Predict Stress Corrosion Cracking and Corrosion
partnership with turbine manufacturers and power producers.
Fatigue of Low-Pressure Turbine Components (1009690), March 2005;
and (1004190), February 2004
“Identifying shutdown conditions, rather than operating stresses, as the
key determinant of turbine failure is a revolutionary finding. Shutdown
Corrosion of Low Pressure Steam Turbine Components (1000557),
protection using dehumidified air should prevent pit initiation,
November 2000
potentially eliminating the risk of component failure,” notes Dooley.
On-Line Resources and Navigation Tips
EPRI’s website, www.epri.com, represents a single-stop resource for
• Events: Calendars, abstracts and programs, registration
information, and technical contact information. (From the “Events”
drop-down menu, select “All EPRI Events” and “Generation.")
information from EPRI’s fossil plant chemistry and materials programs.
Members-only content is available to those with myEPRI accounts;
general content is available to others.
• Base Program Projects and Plans: Program overviews and benefits,
2007-2008 R&D plans and project descriptions, news, project
opportunities, and contacts. (From the “Portfolio > Generation”
• News: Project updates, product releases and plans, event
announcements, newsletters, and contacts for individual programs.
(From the “Members > My Research” drop-down menu, select
“My Research Areas” and click on the “+” sign next to “Major
Component Reliability” to access information on Programs 63, 64,
65, and 87; the “+” sign next to “Combustion Turbines” to access
information on Program 88; or the “+” sign next to “Generation
Issue Programs” to access information on Program 171.)
drop-down menu, select “Major Component Reliability” to access
information on Programs 63, 64, 65, 87, and 171; and select
“Combustion Turbines” to access information on Program 88.)
• Technology Innovation Projects and Plans: Program
overview, success stories, project status information, news,
and contacts. (From the “Portfolio” drop-down menu, select
“Technology Innovation.” Or, from the “Members > My
Research” drop-down menu, select “My Research Areas” and
click on the “+” sign next to “Technology Innovation.”)
• Products: Abstracts, downloadable files, and hard-copy order
forms for completed deliverables. (Select “Product Search”
and enter product number or search terms. Members can
apply the navigation instructions presented above to view
product information relating to specific programs.)
Materials & Chemistry Report
13314787
August 2007
Interacting Mechanisms
Creep-Fatigue Damage Assessment
Creep is defined as a slow change in materials characteristics with time
and usage, while fatigue involves damage resulting from repeated or
cyclic stresses. Creep-fatigue damage arising when these two distinct
mechanisms interact under thermal stresses is of major concern for
high-temperature power plant components.
In conventional steam-electric units built for baseload operation, boiler
and turbine components are increasingly being subjected to operating
practices that involve more stressful cycles—in terms of number,
magnitude, or both—than the design basis. Deployment of large
numbers of combustion turbines with heat recovery steam generators
(HRSGs) has significantly expanded the number of materials and
components exposed to cyclic conditions at high temperatures. New,
In 2006, strategic research was initiated with support from the EPRI
high-efficiency coal plants will be operating at temperatures much
Program on Technology Innovation. The project began with an Expert
higher than those of traditional plants, and they will be employing new
Workshop on Creep-Fatigue Damage Interaction including invited
alloys and components.
representatives from seven countries—Canada, France, Germany,
Together, these factors highlight the increasing importance of creep-
Japan, Switzerland, the United Kingdom, and the United States. The
fatigue damage mechanisms. To support proactive management
delegates, including academics, original equipment manufacturers,
strategies, enhanced knowledge of damage initiation and propagation
utility personnel, researchers, and consultants, held three days of
processes is needed, as are improved techniques to predict damage
discussions to define the current state of knowledge and to evaluate
accumulation and to support run-repair-replace decision making for
existing condition and remaining life assessment methodologies. These
individual components and overall systems.
discussions supported the identification of R&D needs, as well as
initiation of strategic work to address priorities.
Case A
Competitive
Case B
Additive
Case C
Interactive
“Bringing worldwide experts together for conversation on damage
mechanisms is an extremely effective way to kick off resolution-oriented
R&D,” reports David Gandy, EPRI Manager, Fossil Materials and
Repair. “Since the creep-fatigue workshop, we have jumpstarted research
to fill critical knowledge and capability gaps.”
Industry Context
In the power generation industry, creep-fatigue damage is generally the
result of stresses induced by constraints to thermal expansion during
transient conditions. The constraint may be integral—where thermal
gradients arise between the surface and the interior or vice versa—as
in the case of heavy-section components (for example, rotors, headers,
drums, and casings) or components subject to rapid surface heating
Creep-fatigue damage mechanisms interact in different ways, with
varying implications for damage mitigation and component lifetime.
EPRI has engaged worldwide experts in assessing the state of knowledge
and in developing science and technology solutions for damage like that
shown in the photograph above.
(for example, combustion turbine blades). The constraint also may
be external, as in the case of joints between thick and thin sections or
between materials with different coefficients of thermal expansion (for
example, dissimilar metal welds).
continued on page 7
Materials & Chemistry Report
13314787
August 2007
Creep-Fatigue Damage Assessment
continued from page 6
For existing plants, maximizing productivity; deferring replacement of
Much of the past research on creep-fatigue mechanisms and prediction
expensive components; and optimizing operation, maintenance, and
has been aimed at crack initiation phenomena. The resultant knowledge
inspection procedures are all key strategic objectives. This creates two
and capability base has proven useful from a design point of view when
apparently opposing forces: the drive for improved plant availability and
developing and specifying materials offering increased resistance to
profitability necessitates more severe duty cycles, such as increased cold
thermal stresses, and it remains directly applicable once materials are
starts, fast starts, load cycling, and load following; all of which may
placed in service in rotating components where crack initiation typically
cause significant variations in temperature, stress, strain, and, thus,
defines failure. By contrast, crack growth phenomena are particularly
more severe creep-fatigue damage. The need to reduce O&M costs
important for stationary components such as headers and casings,
may result in fewer, shorter, and less rigorous outages and longer outage
where cracks are tolerated and decisions are, therefore, based on damage
intervals, placing components at greater risk of failure.
progression.
The immediate technical challenge is to develop tools and techniques
For both crack initiation and growth, variations in construction
that permit rapid, cost-effective, and accurate condition assessment for
materials, operating environments, stress states, and other factors make
critical components—both with respect to their current status and to
it impossible to apply a single damage rule for all cases. Component-
the possible introduction of alternative strategies for system operation,
specific life prediction is needed using appropriate materials property
inspection, and maintenance.
data generated under conditions relevant to the service and using the
proper failure criterion. In response to this need, EPRI organized the
expert workshop in 2006. Attendees summarized current knowledge and
identified key issues for future consideration in the areas of laboratory
testing methodologies, materials property data, analytical methods
for crack initiation, analytical methods for crack propagation, and
application of creep-fatigue data for component design and assessment.
Subsequently, EPRI published a proceedings volume (1014482)
identifying a set of near-term action items (one year) and defining
medium- and long-term work scopes (two to four years and three to
seven years, respectively). Research was immediately initiated to support
more careful consideration of the interactions between creep and fatigue
in damage-assessment calculations.
Interaction Modes
A 2007 EPRI report (1014837) summarizes results from a comprehensive
review and assessment of creep-fatigue interactions based on previous
studies involving metallographic analysis and laboratory testing of exservice components and virgin materials.
At present, there is no well-established methodology for assessing defect
formation or damage levels when both creep and fatigue mechanisms
are in effect. Common practice is to use “damage diagrams” or “damage
envelopes” defined by fatigue life fraction and creep life fraction data
for specific materials, service environments, and operating conditions.
Current diagrams assume a linear interaction passing through the point
(total fatigue damage = 0.5, total creep damage = 0.5), and they employ
Typical steam-turbine load-change cycles vary the temperature, stress,
and strain conditions imposed on components over time. The complex
modes of interaction between creep and fatigue at present are not
modeled adequately, complicating component assessment and lifetime
optimization. (Source: Viswanathan and Bernstein)
(0.33, 0.33) as a conservative, lower-bound estimate of lifetime. To
support damage assessment, creep and fatigue test data are plotted to
predict crack initiation.
continued on page 8
Materials & Chemistry Report
13314787
August 2007
Creep-Fatigue Damage Assessment
continued from page 7
This simplistic approach implies that creep and fatigue mechanisms are
additive, making no attempt to differentiate between several observed
modes of interaction. In a sequential mode, for example, a component
faces creep conditions when under baseload operation and fatigue
conditions when cycled. If the cyclic behavior involves dwell times at
elevated stress and temperature, then creep and fatigue damage may
accumulate independently, or they may interact. Creep may affect
fatigue, as is conventionally understood, and fatigue may affect creep.
However, the effects may not necessarily be additive.
While adequate for design purposes, separate consideration of creep
and fatigue damage is inadequate for plant operators trying to obtain
as much life as possible from equipment. Recent EPRI work has shown
that current “bi-linear” creep-fatigue interaction diagrams can be
replaced to a good approximation by continuous damage curves, with
the conservative line passing through (0.33, 0.33), which corresponds
Conventional “bi-linear” damage diagrams do not accurately account
for complex creep-fatigue interactions. EPRI research shows that new,
continuous damage curves are a technically valid solution for reducing
over-conservatism in damage assessment and remaining life prediction.
to the maximum combined interaction; and the less conservative line
passing through (0.67, 0.67), which corresponds to independently
acting creep and fatigue processes.
These results suggest that it may not be necessary to apply highly
restrictive damage diagrams in all circumstances. For a given material,
A thorough evaluation of existing damage-assessment approaches that
temperature, strain range, and imposed cycle, less conservative
underlie current methods and codes is under way, with results expected
assumptions may be appropriate, allowing for more optimistic assessment
to inform the development of methodological enhancements. Also, a
of remaining life. The recent report (1014837, 2007) provides guidance
web-based information clearinghouse is being created to facilitate
on the use of metallography and laboratory tests to guide decision
collection and exchange of creep-fatigue data on a worldwide basis, and
making for in-service components.
a second international workshop is scheduled for October 2007.
“Careful analysis of creep-fatigue interactions avoids the need for
Lead Contacts
wholesale application of lower-bound—potentially over-conservative—
assessments,” says Gandy. “Initial work has laid the foundation for
David Gandy, davgandy@epri.com, 704.595.2198
considering a new approach to assessment of creep-fatigue damage
Vis Viswanathan, rviswana@epri.com, 650.855.2450
interactions.”
Key Resources
Next Steps
Creep-Fatigue Damage Accumulation and Interaction Diagram Based on
In 2007, interim EPRI guidelines are being developed to address several
Metallographic Interpretation of Mechanisms (1014837), March 2007
key issues:
Proceedings of the Expert Workshop on Creep-Fatigue Damage Interaction
• Use of standardized laboratory testing methods and specimens for
(1014482), November 2006
collection of data that supports modeling of damage initiation and
Damage Mechanisms and Life Assessment of High-Temperature Components,
growth processes, as well as component design and assessment
R. Viswanathan, ASM International, 1989
• Data requirements for condition and remaining
life assessment of in-service components
• Criteria for inspection and monitoring of damaged components
Materials & Chemistry Report
13314787
August 2007
Project Updates
Updated and Expanded Tube Failure
Book Available
operating environments, and the basic chemistry and materials issues.
One of EPRI’s most popular products, Boiler and Heat Recovery Steam
address failure mechanisms in specific environments. A total of 47
Volume 1: Fundamentals provides background on BTF/HTF impacts,
Volume 2: Water-Touched Tubes and Volume 3: Steam-Touched Tubes
mechanisms are covered, with 35 relevant to conventional plants and
Generator Tube Failures: Theory and Practice, has been reissued in updated
and greatly expanded form. Drawing on worldwide industry experience
25 specific to HRSGs.
and the latest R&D findings, the book provides comprehensive guidance
Power producers adopting EPRI’s BTF management program have
on tube failure mechanisms and preventive measures in conventional
realized substantial availability improvements as well as savings totaling
steam-electric plants and combined-cycle units.
in the tens to hundreds of millions of dollars per year (1013098, 2006).
Boiler tube failure (BTF) and heat recovery steam generator (HRSG)
Participants in an analogous HTF management program are reaping
tube failure (HTF) have been the primary availability problems for as
similar benefits.
long as reliable statistics have been kept. Tubes fail in new and old units;
EPRI offers customized workshops and training services to assist
in cycling and baseload plants; in supercritical, once-through, and drum
owners and operators of conventional and combined-cycle plants with
boilers; in HRSGs; and in plants burning every sort of combustible
implementing comprehensive BTF/HTF reduction and cycle chemistry
material. They emanate from poor initial design, inadequate operation
improvement programs, as well as with diagnosing and addressing
and maintenance, harsh fireside and cycle chemistry environments, and
specific failure problems.
lack of management support for comprehensive interventions.
Contact: Kent Coleman, kcoleman@epri.com, 704.595.2082
“Most failures are repeat occurrences, indicating that returning a unit
Modeling Deposition Phenomena
in Drum-Type Boilers
to service is often viewed as more important than understanding failure
mechanisms and root causes,” notes Barry Dooley, EPRI Technical
Executive, Materials & Chemistry. “If you commit to BTF and HTF
reduction, you can reduce availability losses and increase revenues—it
A preliminary model of processes governing complex deposition
is as simple as that.”
phenomena in fossil drum-type boilers has been developed—an
EPRI’s new, three-volume book, available as a single product (1012757,
important step along the path toward enhanced corrosion control
March 2007), provides owners and operators with a technical basis for
capabilities and optimized chemical cleaning practices.
preventing repeat failures and creating permanent solutions. It reflects
BTF mechanisms involving deposition on water-side heat transfer
worldwide experiences with the initial BTF manual (TR-105261, V1–3,
surfaces are a significant problem. Improved understanding and
published in 1996) and the initial HTF manual (1004503, published
management of boiler deposition are integral to reducing BTF incidence
in 2002), along with R&D progress and practical advances over the
and improving plant availability. Initial EPRI research to determine the
last decade. Experts in failure analysis, tube materials, cycle chemistry,
feasibility of modeling the various processes governing deposition was
inspection methods, and operations and maintenance contributed to
completed in 2004 (1004931).
the new book’s development and review.
“The goal of the model development activity is to create a tool supporting
elimination of avoidable deposition and enhanced management of
any deposition that cannot be prevented,” states Kevin Shields, EPRI
Manager, Water Chemistry. “Phase 1 work demonstrated feasibility
and highlighted the need to take an iterative approach in addressing
technical challenges and knowledge gaps.”
A new EPRI report (1012207, 2007) presents findings from follow-up
work by an interdisciplinary project team. To date, an overall model
structure applicable to deposition at simple-geometry locations (that
continued on page 10
Failed Tubes
Materials & Chemistry Report
13314787
August 2007
Project Updates
continued from page 9
is, vertically oriented, smooth surface tubing) has been established,
At present, the project team is developing an expanded database of
and several key fluid-deposit interactions have been characterized.
deposit characterization data and integrating the equations governing
For example, equations have been developed to describe ionization
fluid-deposit interactions with those characterizing phenomena
and precipitation processes for selected chemical species, as well as the
within porous deposits. The current, simplified deposition model
interactions of sodium, phosphate, ammonia, chloride, iron, and copper
also is being enhanced to account for the influence of tube surface
species. Also, a two-dimensional model has been created characterizing
geometry since solids accumulate and damage often initiates in non-
heat, mass, and solute transport activity within porous boiler deposits.
vertical tubing sections and in areas with flow disruptions or direction
changes. Continuing work will improve the research-grade model’s
ability to predict deposit growth rates and characteristics, as well as the
chemistry environment within deposits during boiler operation. This
will lead to new guidelines for maintaining chemistries to avoid underdeposit corrosion problems and to safely extend time intervals between
operational chemical cleanings.
Contact: Kevin Shields, kshields@epri.com, 410.374.0110
Sensors for On-Line Monitoring
of Steam-Phase Conditions
New technology for on-line monitoring of key parameters in the phase
transition zone (PTZ) of low pressure (LP) steam turbines is moving
closer to commercial reality. The EPRI Steam Sensor, scheduled for
field demonstration in 2008, is potentially applicable for controlling
processes that can lead to corrosion of LP blades and disks in all types of
steam-electric generating plants.
For more than a decade, EPRI has been directing strategic research to
provide the foundation for deterministic modeling of stress corrosion
cracking and corrosion fatigue processes. EPRI’s “Corrosion in the
PTZ” code, scheduled for beta-version release in 2008, will allow
operators to use mechanistic models and on-line data for predicting
damage initiation and propagation, analyzing probability of failure, and
implementing effective countermeasures. (See pp. 2–5 for a discussion
of PTZ modeling.)
Unchecked deposit growth can lead to performance degradation,
chemical attack, and component failure in conventional plants and
heat-recovery steam generators. Comprehensive, deterministic modeling
of complex deposition-related phenomena may be used to understand
the deposit and fluid environments under which damage becomes active,
thus permitting better management of cycle chemistry conditions and
cleaning schedules to prevent tube failures.
Anticipating the code’s development, EPRI initiated an Innovator’s
Circle project in 2004 to fill a critical capability gap by exploring novel
approaches for generating the requisite on-line data on the properties
of liquid films forming on PTZ surfaces during turbine operations.
This strategic project demonstrated proof of concept for capillary
condensation as a means of sampling superheated steam, creating
To supplement theoretical and semi-empirical equations created in EPRI
a liquid film on the surface of a sensor, and measuring the three key
work, the project team has examined empirical relations developed in
parameters that influence PTZ corrosion: pH, chloride, and oxidizing-
previous research. In addition, the characteristics of fire-side and water-
reducing potential (1013099, 2006).
side deposits from a fossil drum-type boiler have been comprehensively
assessed, and results have been critically examined for use as input
parameters to various model equations.
Materials & Chemistry Report
13314787
continued on page 11
10
August 2007
Project Updates
continued from page 10
In a follow-on project, atmospheric- pressure and high-pressure facilities
At present, a number of early USC units worldwide are operating at
were built to research the optimum capillary condensation medium and
steam conditions close to 600°C and 27 MPa (1100°F and 4000 psi),
to test sensing capabilities up to 100°C (212°F). Results demonstrated
offering substantial efficiency improvements relative to conventional
that sensors can measure pH and chloride with reasonable accuracy in
subcritical and supercritical plants. Advanced USC plant technology
the steam phase. The work also established the viability of capillary
promises substantially higher efficiencies and lower pollutant and carbon
condensation as a way to maintain a continuous electrolyte layer in a
dioxide (CO2) emissions than these state-of-the-art units and even the
nanoporous medium, a prerequisite for on-line monitoring (1012206,
next-generation plants being pursued in international research.
2007).
“Continuing technology development and demonstration programs in
Ongoing technology development activities focus on testing a redox
Europe and Japan focus on materials capable of withstanding steam
potential sensor, together with efforts to combine sensors for pH,
conditions up to 700°C,” reports Vis Viswanathan, EPRI Technical
chloride, and oxidizing-reducing potential in one PTZ probe suitable
Executive, Materials Applications. “The U.S.-centered activities target
for in-field testing and commercialization. EPRI will work with an
an even more ambitious operating envelope.”
instrument manufacturer and select a host site for a 2008 demonstration
The first five-year phase of the U.S. program has made substantial
project.
progress relating to the materials and processes required for economical
boiler operation at temperatures approaching 760°C (1400°F). Two
Contact: Mia Caldwell, mcaldwell@epri.com, 650.855.2771
major domestic boiler manufacturers completed conceptual design of
Turbine and Boiler Materials Development
for Advanced Ultrasupercritical Coal Plants
750-MW boilers and established heat balance diagrams. Alloys with the
creep strength required to withstand target temperatures and stresses at
different locations in the boiler have been identified and tested for times
Collaborative efforts are under way to develop steam turbine materials
exceeding 30,000 hours.
technology for advanced ultrasupercritical (USC) coal plants,
The fire-side and steam-side corrosion resistance of selected alloys and
complementing a successful U.S. program to create the foundation for
the efficacy of various coatings and claddings have been evaluated, and
pulverized-coal (PC) boilers capable of operating at temperatures of up
the weldability and fabricability of the alloys have been demonstrated by
to 760°C (1400°F) and pressures of up to 35 MPa (5000 psi).
Throttle Conditions at Turbine Inlet
(Key Conditions D Cyde Limitation)
732˚C (1350˚F)
34.5 MPa (5000 psi)
SH Outlet
736˚C (1356˚F)
36 MPa (5250 psi)
manufacturing prototype header and superheater sections. The effects
761˚C (1401˚F)
8 MPa (1142 psi)
760˚C (1400˚F)
7.8 MPa (1128 psi)
LP Turbine
HP
Turbine
IP Turbine
Condenser
877˚F (470˚C)
Makeup
Attemperation
Boiler
38˚C (100˚F)
Deaerator
LP Heaters
HP Heaters
333˚C (631˚F)
32 MPa (5641 psi)
4 HP Heaters
Extracted Steam 554˚C, 540˚C, 467˚C, 331˚C
(1030˚F, 1003˚F, 873˚F, 628˚F)
Condensator
Polisher
5 LP Heaters
Through an EPRI-government-industry program, component materials and fabrication methods have been developed for advanced ultrasupercritical
power plants, and two U.S. boiler manufacturers have created designs and energy balance diagrams for high-efficiency 750-MW units.
continued on page 12
Materials & Chemistry Report
13314787
11
August 2007
Project Updates
continued from page 11
of welding and other fabrication processes on design margins have
conditions when firing fuels containing different sulfur levels. EPRI
been defined for some of the alloys, and reference stress approaches for
continues to coordinate all technical activities, while Energy Industries
eliminating undue conservatism in boiler design have been explored.
of Ohio is providing overall project administration.
According to cost-performance analyses, the economic viability of
The parallel USC turbine materials development program was launched
advanced USC plant designs will arise in large part from an energy
in October 2005 by the Ohio Coal Development Office and the U.S.
conversion efficiency exceeding 45% and a nearly 30% reduction in
Department of Energy’s National Energy Technology Laboratory
emissions relative to current PC technologies. These attributes will
(DOE/NETL) with cost sharing and technical participation from
allow for reduced fuel costs and for construction and operation of
EPRI, Alstom Power, General Electric (GE), and Siemens. Oak Ridge
smaller fuel handling and environmental control systems. The fuel,
National Laboratory (ORNL) is providing technical support under
balance-of- plant, and waste disposal savings will more than offset
direct funding from DOE/NETL. Major task areas and responsibilities
projected increases in materials costs required to support operation
are displayed in the figure below.
under advanced USC conditions.
During the first year of the program, much of the work focused on
Cost-competitiveness is expected even in the absence of climate
preliminary selection of candidate materials, coatings, and component
policies that, by assigning a price to CO2 emissions, will further
fabrication techniques potentially suitable for advanced USC steam
increase the relative cost of lower-efficiency, higher-emitting coal-fired
turbines and on the design of appropriate testing protocols.
technologies.
In early laboratory work, alloys for integral rotor applications have
Studies also have shown that advanced USC plants could, with
been subjected to temperatures up to 760°C (1400°F), leading
relatively little additional equipment, operate under oxyfuel combustion
to identification of some materials with particularly promising
conditions, where the fuel is burned in an oxygen-rich environment
characteristics. Ongoing testing will provide the data required
rather than regular air to yield a flue gas with high CO2 concentration.
for detailed turbine design studies; analyses of cost-benefit trade-
This approach would greatly improve the economics of CO2 capture,
offs; and a roadmap for future technology development, demonstration,
establishing advanced USC plant technology as an option for achieving
and deployment.
near-zero emissions.
EPRI projects that collaborative industry/government efforts to develop
Ongoing boiler materials work is expected to deliver the engineering
advanced USC plant technology could lead to initial commercial
knowledge required to select appropriate alloys and coatings for
deployment by around 2015.
economical PC plants capable of operating under advanced USC steam
Design & Economic Studies (Alstom)
Assistance (Siemens & GE Energy)
Review State of the Art and Identify
Candidates for 760˚C Application (All)
Oxidation & Erosion Studies
(Siemens, Alstom)
Rotors, Buckets, & Bolting
Non-Welded Rotors
(GE)
Mechanical Properties
of Materials (GE)
Contact: Vis Viswanathan, rviswana@epri.com, 650.855.2450
Materials property data characterization,
microstructural and steam int. studies (ORNL)
Castings
(Siemens)
Welded Rotors
(Siemens, Alstom)
Welability Studies
(Siemens, Alstom)
Mechanical Properties
(Siemens, Alstom)
Mechanical Properties
(Siemens)
A collaborative three-year project on turbine materials for high-efficiency coal-fired power plants (760°C; 1400°F) is under way with technical
participation from Alstom, EPRI, General Electric, Siemens, and Oak Ridge National Laboratory.
Materials & Chemistry Report
13314787
12
August 2007
Technology Innovation
Nanocoating Development for Waterwall
Protection
Results to date from laboratory experiments indicate that coatings
In early 2007, the U.S. Department of Energy (DOE) awarded a
selective oxidation, nanostructured coatings require about one-third the
integrating chromium and/or aluminum additives at the nanoscale
offer a number of benefits over conventional coatings. Owing to
aluminum or one-half the chromium content to establish protective,
three-year, $2.4 million project to EPRI to support the development
thin, and continuous thermally grown oxides. The oxides are more
of nanotechnology-based coatings for improving corrosion resistance
adherent and more resistant to thermal cycling and spalling than
of waterwalls in conventional and advanced coal-fired boilers. This
protective scales forming on conventional coatings, and they are much
project will build on initial strategic research by EPRI that highlights
more resistant to oxidation and corrosion.
the promise of nanocoatings in fossil plant applications.
“Laboratory work suggests that nanocoatings could mitigate fire-
Fire-side corrosion of waterwall tubing is the primary cause of forced
side corrosion in subcritical and supercritical boilers and provide the
outages and availability losses in conventional coal plants, costing U.S.
protective capabilities needed in ultrasupercritical environments,”
power producers alone almost $150 million each year. Existing mitigation
notes David Gandy, EPRI Manager, Fossil Materials & Repair. “The
measures—including weld overlays and thermal spray coatings—offer
some protection, especially in subcritical boilers. However, field
challenge now is to create coatings suitable for real-world application.”
experience indicates that weld overlays can create additional problems,
Strategic research by EPRI is continuing in conjunction with the three-
while conventional coating technologies cannot provide long-term
year DOE project, which was awarded under an initiative targeting
protection in supercritical units. In ultrasupercritical (USC) and
cost-effective technologies to improve performance and economics of
advanced (USC) boilers, much higher operating temperatures and
advanced coal-based plants offering near-zero emissions. Work focuses
on the design of nanocoatings and the development of processing
capabilities optimized for waterwall applications in conventional and
USC boilers. Computational modeling techniques will be applied to
evaluate alternative coating compositions and predict their performance
and lifetime. The effectiveness of the application process and the
metallurgical and mechanical properties of the nanocoatings will be
evaluated in simulated boiler environments using coals from three
different regions.
pressures are anticipated to create more severe fire-side tube corrosion
challenges.
EPRI initiated Technology Innovation (TI) work in 2006 to explore the
use of nanotechnology to develop coatings with protective capabilities
beyond those achievable with conventional materials. An expert team
was convened to review information from the published literature,
vendor surveys, university research, and industry experience. A new
report summarizes what is known about the abilities of nanocoatings to
Contact: David Gandy, davgandy@epri.com, 704.595.2198
resist oxidation, corrosion, and erosion in boiler environments (1014805,
2007). It incorporates information on the composition, structure,
continued on page 14
properties, processes, surface preparation methods, and application
procedures associated with conventional and advanced corrosion- and
erosion-resistant coatings.
Ni-10% Cr
Conventional
Ni-20% Cr
Conventional
Nano-structured waterwall coatings applied using innovative materials
processing techniques offer potential both for reduced costs and improved
in-service performance.
Ni-11% Cr
Nanostructure
Materials & Chemistry Report
13314787
13
August 2007
Technology Innovation
continued from page 13
Advanced Feedwater Filtration Options
In a project funded through the Innovator’s Circle program, EPRI
A new EPRI report identifies and evaluates existing and emerging
on the horizon (1014483, 2006). TI results indicate that, in most
filtration technologies potentially suitable for removing corrosion
circumstances, the best available solution today for corrosion product
products from feedwater systems in high-temperature, high-pressure
control is proper selection and optimization of chemistry.
reviewed commercially available filtration systems and new technologies
power plant environments.
Commercial feedwater filtration products may prove cost-effective in
Left unchecked, corrosion products can form deposits conducive to
niche applications, while filtration systems used in other industries
chemical attack on heat transfer surfaces in conventional fossil and
appear transferable to operation under typical feedwater conditions.
nuclear steam-electric plants and heat-recovery steam generators. Sound
Examples include flow-through devices with magnetic or metal alloy
chemistry management programs can minimize corrosion product
filter elements and cross-flow filters with metal alloy or ceramic elements.
formation and transport, while periodic chemical cleaning is practiced
In addition, some emerging filtration techniques could be relevant, but
as needed to remove deposits.
will require further development.
“By reducing corrosion product transport, advanced filtration
Before feedwater filtration systems optimized for current and advanced
technologies could further reduce or eliminate the need for chemical
generating plants become a reality, many technical issues must be
cleaning,” says Kevin Shields, EPRI Manager, Water Chemistry.
addressed relating to design, installation, operation, and maintenance
“Development of effective feedwater filtration systems would thus
in retrofit applications and new units. The next steps are to assess
reduce cleaning-related outage times and costs, but more important, it
operational compatibility for different plant configurations and to
would help curtail deposition on heat transfer surfaces, which is a root
appraise the expected cost, benefit, and net value of such filters.
cause of some major component degradation mechanisms.”
Also, EPRI will maintain a watch on emerging filtration options.
Results could help identify feedwater filtration technologies considered
worthy of testing under retrofit plant conditions using small units
capable of processing relatively low flows in the temperature and pressure
conditions of interest.
A base program project to further assess designs that may offer near-term
potential for enhanced corrosion product control is under way in 2007.
EPRI will develop guidance for effective application of condensate filters
to remove metal oxides during startup in peaking and cycling units.
“Corrosion product levels can be very high at startup, particularly if
cycle chemistry is not properly managed during the shutdown and
layup,” states Shields. “Use of condensate filters sized to handle startup
flows and to subsequently be taken out of service could represent a costeffective solution.”
Contact: Kevin Shields, kshields@epri.com, 410.374.0110
New approaches to feedwater filtration could help remove the corrosion
products that can cause major problems as they travel through watersteam circuits and deposit and accumulate on heat transfer surfaces, as
shown at left and in the above cross-section.
Materials & Chemistry Report
13314787
14
August 2007
Featured Products
X20 CrMoV12-1 Steel Handbook
(1012740)
Visit www.epri.com to download or order these documents and to access
EPRI’s comprehensive portfolio of Materials and Chemistry products
for conventional and combined-cycle plants.
This handbook, part of a continuing series, compiles important
Condensate Polishing State of Knowledge
Assessment (1012208)
metallurgical information regarding power plant applications of X20
CrMoV12-1 steel. This material has been used since the early 1960s in
superheater and reheater tubes, main steam pipes, boilers, turbine cases
Properly designed and operated condensate polishing (CP) systems are
and blades, and other high-temperature components where high creep
essential for excellent cycle chemistry performance at fossil plants, but
strength, corrosion, and oxidation resistance are desired. The guidebook
these systems find limited use in existing units and are not routinely
provides easy access to data and guidelines on metallurgy, properties
installed in new plants. This report reviews commercially available and
(including physical, mechanical, creep, and fatigue properties),
emerging CP technologies in the context of present-day cycle chemistry
fabrication issues, and material specifications.
requirements and the needs and concerns of management, technical,
and operating personnel. Deep-bed CP technology represents the state
Heat Recovery Steam Generator (HRSG)
Chemical Cleaning Guidelines Case
Studies (1012756)
of the art, and a variety of short- and long-range R&D activities could
help expand its use and enhance its performance as a cycle chemistry
improvement measure in retrofit and new applications. Near-term needs
are to improve understanding of operating and environmental discharge
requirements, to address tradeoffs relating to capital costs and life-cycle
Chemical cleanings of HRSGs can impose substantial costs. Failure to
benefits, and to interest manufacturers in making further technology
clean or to use proper cleaning practices may contribute to chemistry
improvements.
control problems and subsequent evaporator tube damage and failure.
Based on recent industry experience, this report supplements EPRI’s 2003
guidelines (1004499) by detailing approaches for the effective planning
and performance of chemical cleanings, as well as for the application of
nonchemical options (for example, hydrojetting) to remove deposits. It
presents case studies of operational cleanings, including information on
reasons for cleaning, characteristics of deposits, cleaning procedures,
and results. The case studies also document problems experienced and
describe lessons learned from not maintaining cycle chemistry, not
assessing water-side cleanliness, and not implementing cleanings as
indicated in EPRI guidelines.
Proceedings: International Conference on
the Interaction of Organics and Organic
Cycle Treatment Chemicals with Water,
Steam, and Materials (1013630)
A 2005 conference was organized to evaluate current knowledge and
experience and to identify R&D needs regarding the presence of organics
in water-steam cycles and the use of organic additives. Presentations
and discussions concluded that there is no irrefutable quantitative
evidence that organics or their decomposition products are directly
involved in component damage. A more thorough understanding of
Understanding available condensate polishing system designs and
associated operating requirements is essential for optimal selection and
use of this cycle chemistry management technique.
Materials & Chemistry Report
13314787
continued on page 16
15
August 2007
Featured Products
continued from page 15
Fossil Plant Cycle Chemistry Instrumentation
and Control—State-of-Knowledge Assessment (1012209)
decomposition products and chemical properties (surface tension,
viscosity, and solubility) is required. Additional research also is needed
on the application of organics as treatment chemicals, for shutdown
and layup, and for improved power plant efficiency. Follow-on EPRI
work is planned to allow the current suite of cycle chemistry treatment
Effective monitoring of the purity of water and steam is an integral
guidelines to be revised.
part of productive cycle chemistry management programs. On-line
monitoring is preferable to conventional grab sample analysis because it
Plant Guide to Turbine Disk Rim Inspection
(1013459)
minimizes the time needed to identify and respond to out-of-specification
conditions. It also provides early warning of equipment malfunctions
and facilitates control of chemical additions and overall conditions.
Steam turbine disk rim cracking is a result of localized stress, steam
This report describes proven options for real-time monitoring of key
chemistry contaminants, temperature influences, operating conditions,
parameters, and it provides information on both recently developed and
and other contributors. This report provides comprehensive guidance
emerging techniques. In the latter category are approaches for direct
for plant staff contracting for nondestructive (NDE) inspection
monitoring of electrochemical corrosion potential and corrosion rate,
services to inform the run/repair/replace decision process for the
which could lead to significant improvements in cycle chemistry control
highly stressed disk rim area. It includes an overview of surface and
and corrosion prevention.
volumetric NDE methods for two predominant disk blade attachment
configurations. Information is also provided regarding inspection
Upcoming Events
personnel qualifications and inspection procedure review and
oversight. Finally, software applications are described for determining
Listed below are events scheduled for upcoming months.
Visit “Events” at www.epri.com for registration and technical
information on conferences, workshops, classes, teleconferences,
and advisory meetings sponsored by EPRI’s Materials and
Chemistry programs.
critical crack size in the disk rim area and performing remaining
life assessment using a varity of material, stress, and operational
factors.
EPRI Generation Sector Program/Council Advisory Meetings
Denver, Colorado
September 17–21, 2007
5th International Conference on Advances in Materials Technology
for Fossil Power Plants
Marco Island, Florida
October 3–5, 2007
International Conference on Boiler Tube and HRSG Failures
and Inspections
Calgary, Alberta, Canada
October 16–18, 2007
Winter EPRI Turbine/Generator Users Group (TGUG) Meeting
San Diego, California
January 21–25, 2008
Workshop on Grade 91/92 Steels
Clearwater Beach, Florida
Proper inspection is critical to the effective detection, management, and
mitigation of steam turbine disk rim cracking.
Materials & Chemistry Report
13314787
April 7–9, 2008
16
August 2007
Recent Deliverables
Listed below are products completed since May 31, 2006. Visit www.epri.com to download or order these and other products from EPRI’s materials
and chemistry programs.
Product ID
Product Name and Release Date
1012201
Fossil Plant High-Energy Piping Damage: Theory and Practice; 6/26/07
1013666
Technology Innovation: Oxide Growth and Exfoliation on Alloys Exposed to Steam; 6/26/07
1015268
Steam Turbine Generator Notes 2007; 6/20/07
1012757
Boiler and Heat Recovery Steam Generator Tube Failures: Theory and Practice; 3/30/07
1012212
Guidelines for Reducing the Time and Cost of Turbine-Generator Maintenance Overhauls and Inspections - 2006; 3/30/07
1013358
The Grades 11 and 12 Low Alloy Steel Handbook; 3/30/07
1014670
Carbon Steel Handbook; 3/29/07
1014813
Electrochemical Corrosion Potential (ECP) of Hollow Copper Strands in Water Cooled Generators; 3/28/07
1012207
Boiler Water Deposition Model for Fossil-Fueled Power Plants; 3/26/07
1014837
Technology Innovation: Creep-Fatigue Damage Accumulation and Interaction Diagram Based on Metallographic Interpretation of
Mechanisms; 3/26/07
1013359
Fracture Toughness of Aged Boiler Drums; 3/26/07
1013360
Stress Corrosion Cracking of Grade 91 Materials; 3/26/07
1012743
Circumferential Seam Weld Cracking: An Interim Report; 3/26/07
1014721
Technology Innovation: Repair of Flow-Accelerated Corrosion in Fossil Power Plants; 3/26/07
1012209
Fossil Plant Cycle Chemistry Instrumentation and Control–State-of-Knowledge Assessment; 3/22/07
1012744
Fossil Power Plant Components Failure Analysis Guideline; 3/22/07
1012758
Evaluating and Avoiding Heat Recovery Steam Generator Tube Damage Caused by Duct Burners; 3/20/07
1014831
Proceedings: Eighth International Conference on Cycle Chemistry in Fossil and Combined Cycle Plants with Heat Recovery Steam
Generators, June 20–22, 2006, Calgary, Alberta Canada; 3/20/07
1012210
Simulated Boiler Corrosion Studies Using Electrochemical Techniques; 3/15/07
1012206
Development of Steam Phase Sensors; 3/15/07
1012748
Guideline for Welding Creep Strength-Enhanced Ferritic Alloys; 3/12/07
1012762
Heat Recovery Steam Generator Repair Welding Technologies to Address FAC In Tube Bends; 3/12/07
1014805
Technology Innovation: State of Knowledge Review of Nanostructured Coatings for Boiler Tube Applications; 3/12/07
1012741
Thermal Fatigue of Waterwalls Associated with Water Cannons; 3/8/07
1012742
Refining the Probability of Failure for the Risk Management Process; 3/8/07
1012759
Guidelines for the Nondestructive Examination of Heat Recovery Steam Generators; 2/27/07
1012203
Guidelines for New High Reliability Fossil Plants; 2/26/07
1012204
Development of Model to Predict Stress Corrosion Cracking and Corrosion Fatigue of Low Pressure Turbine Components; 2/26/07
1014741
Technology Innovation: Detection of Circumferential Cracking in Weld Overlays on Boiler Tubes; 2/15/07
1014717
Project Management Guidance When Upgrading Steam Turbines at Nuclear and Fossil Power Plants; 1/15/07
1013044
SAFER-PC Version 2.2, Stress and Fracture Evaluation of Rotors - Personal Computer, Version 2.2; 12/22/06
1012220
Turbine Cycle Heat Rate Monitoring: Technology and Application; 12/20/06
1014598
Productivity Improvement for Fossil Steam Power Plants, 2006; 12/18/06
1013459
Plant Guide to Turbine Disk Rim Inspection; 12/18/06
1008125
Boiler OIO 2.0 - Boiler Overhaul Interval Optimization Software, Version 2.0; 12/15/06
1012200
EPRI Staff ASME Code Support 2006; 12/14/06
continued on page 18
Materials & Chemistry Report
13314787
17
August 2007
Recent Deliverables
continued from page 17
Product ID
Product Name and Release Date
1013462
Turbine-Generator Auxiliary Systems, Volume 2: Turbine Steam Seal System Maintenance Guide; 12/14/06
1012216
Generator On-Line Monitoring and Condition Assessment; 12/11/06
1013460
Torsional Interaction Between Electrical Network Phenomena and Turbine-Generator Shafts; 12/4/06
1013461
Turbine Overspeed Trip Modernization; 12/4/06
1013458
Main Generator Rotor Maintenance; 11/27/06
1014482
Technology Innovation: Proceedings of the Expert Workshop on Creep-Fatigue Damage Interaction; 11/20/06
1014483
Technology Innovation: Assessment of Advanced Feedwater Filtration for Electric Power Generating Stations; 11/13/06
1012756
Heat Recovery Steam Generator (HRSG) Chemical Cleaning Guidelines Case Studies; 11/13/06
1012208
Condensate Polishing State of Knowledge Assessment; 11/8/06
1014557
Ultrasonic Inspection of Generator Rotor Dovetails with Limited Inspection Surface; 11/8/06
1014391
Technology Innovation: The Detection of Circumferential Cracking in Weld Overlays on Boiler Tubes - Modeling Study; 9/18/06
1012740
X20 CrMoV12-1 Steel Handbook; 9/18/06
1014405
Technology Innovation: Fossil Power Plant Cost and Performance Trends: Cycling Units 1970 - 2002; 8/31/06
1013630
Proceedings: International Conference on the Interaction of Organics and Organic Cycle Treatment Chemicals with Water, Steam,
and Materials; 8/30/06
1013629
Proceedings: International Conference on Boiler Tube and HRSG Tube Failures and Inspections; 8/29/06
1014363
Application of Nondestructive Evaluation Technologies at Xcel Energy; 7/24/06
1010177
RLSM 1.0 - Remaining Life Simulation and Monitoring, Version 1.0 on CD for Win 2000/XP; 7/3/06
1010620
Boiler Condition Assessment Guideline; 6/8/06
1013284
Evaluation of the AEA Technology Engineering Services AIS Rotor Bore Ultrasonic Imaging System; 6/5/06
Supplemental Projects
Listed below are projects open for participation by members of EPRI’s fossil plant Materials and Chemistry programs. Visit www.epri.com to
download project overviews.
Product ID
Product Name and Release Date
1014905
Demonstration of Early Detection of Flow Restrictions in Water-Cooled Generators
1014771
Detecting the Presence of Turbine-Generator Torsional Oscillations Using Generator Flux Probe
1014718
Torsional Interaction Between Steam Turbine-Generators and Power System Disturbances
1014456
Evaluation of Supercritical Boiler Waterwall Cracking Due to Thermal Fatigue
1014568
Turbine-Generator Boresonic System Evaluation
1014464
Providing Access for Inspection of Corrosion-Fatigue Damage in Waterwalls and Subsequent Repair
1014546
Development of Model for Optimizing Explosive Cleaning to Avoid Tubing Damage
1014539
On-Line Monitoring of Shorted Laminations in Generator Stator Core
1014424
Productivity Improvement Expert Reviews (PIER)
1014350
Development of Digital Radiographic System for Examination of Waterwall Tubes for Corrosion- Fatigue
1013716
On-Line Monitoring of Generators and Large Motors Using Electromagnetic Interference (EMI) Analysis Interest Group
1011286
Remaining Life Assessment of Grade 91 Superheater and Reheater Tubing Subject to Long-Term Overheat-Creep Damage
Materials & Chemistry Report
13314787
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August 2007
Materials & Chemistry Staff Experts
EPRI’s fossil plant Materials and Chemistry experts manage R&D projects and provide application services primarily through the following
programs:
• Boiler Life and Availability Improvement (63)
• Boiler and Turbine Steam and Cycle Chemistry (64)
• Steam Turbines, Generators, and Balance-of-Plant (65)
• Fossil Materials and Repair (87)
• Heat-Recovery Steam Generator (HRSG) Dependability (88)
• Thermal Fatigue Cracking in the Waterwalls of Supercritical Boilers (171)
Listed below are EPRI staff members, main program affiliations, contact information, and areas of expertise:
Mia Caldwell (64, 87)
Kevin Shields (64, 88)
Senior Project Manager
Manager, Water Chemistry
mcaldwell@epri.com, 650.855.2771
kshields@epri.com, 410.374.0110
• Boiler Corrosion Monitoring
• Cycle Chemistry
• Low-Temperature Corrosion
• HRSGs
• High-Temperature, Thick-Section Fatigue
• Chemical Cleaning and
Condensate Polishing
• Condenser Tube Failure
Kent Coleman (87)
Manager, Boiler Life & Availability
Vis Viswanathan (87)
kcoleman@epri.com, 704.595.2082
Technical Executive, Materials Applications
• Conventional and Advanced
Fossil Plant Materials
rviswana@epri.com, 650.855.2450
• Welding and Repair of Boiler
Components and Piping
• Condition and Remaining Life Assessment
• Conventional and Advanced
Fossil Plant Materials
David Gandy (63, 87, 88),
Manager, Fossil Materials & Repair
Stan Walker (63, 87, 88)
davgandy@epri.com, 704.595.2198
Manager, Fossil NDE Center
• Steam Turbine, Boiler and Combustion
Turbine Materials and Coatings
swalker@epri.com, 704.595.2081
• Welding and Repair
• NDE Technology Development
and Application
• Condition and Remaining Life Assessment
• Boiler Components, Piping, and HRSGs
• Nanotechnology Applications
Paul Zayicek (65)
Alan Grunsky (65),
Project Manager, Steam Turbines, Generators,
and Balance-of-Plant
Manager, Nuclear Steam Turbine-Generator
Initiative; Steam Turbine, Generators, and
Balance-of-Plant
pzayicek@epri.com, 704.595.2154
• NDE Technology Development
and Application
agrunsky@epri.com, 704.595.2056
• Steam Turbines, Generators,
and Auxiliary Systems
• Steam Turbines
Materials & Chemistry Report is produced by, and distributed to
funders of EPRI’s fossil plant Materials and Chemistry programs (63,
64, 65, 87, 88, 171). Contact: Kevin Shields, kshields@epri.com;
410.374.0110.
• Inspection and Repair Methods
• Failure Analysis
Materials & Chemistry Report
13314787
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August 2007
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EPRI brings together members, participants, the Institute’s scientists
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August 2007
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