Search Results for power plant components

Grade 91 steel, while increasingly popular in high-temperature power plants for both retrofit and new construction applications, faces significant challenges with Type IV cracking at the outer parent side edge of the weld heat affected zone. This structural integrity issue has led to extensive weld inspection requirements and, in severe cases, the premature replacement of grade 91 retrofit headers before their intended design life. This paper presents a method for estimating Type IV cracking timelines in operating grade 91 components by analyzing crossweld Type IV data to determine when Type IV life deviates from parent life. By combining test results from various temperatures, the method generates a generalized prediction of Type IV life that can be extrapolated to any temperature of interest, providing a practical lower bound estimate for service life of the weakest grade 91 material. This approach, which can be applied to service operating conditions to establish realistic inspection timelines for plant components, has already successfully identified early-stage Type IV cracking in two retrofit headers and is being expanded to additional grade 91 components.

The impression creep test method using a rectangular indenter has been well established and the applicability of the technique has been supported by the test data for a number of metallic materials at different temperatures and stresses. The technique has proved to be particularly useful in providing material data for on-site creep strength assessments of power plant components operating in the creep regime. Due to these reasons, “standard” assessment procedures using the impression testing method are needed in order for the technique to be more widely used. This paper will first address some key issues related to the use of the impression creep test method, involving the data conversion method, typical test types and validity of the test technique etc. Then some recommendations on a number of practical aspects, such as the basic requirements of test rigs, “standard” specimen geometry, indenter dimensions, sampling procedures for scoop samples, specimen preparation, temperature and loading control, and displacement measurement, are briefly addressed. Finally, applications of the test data to assist with the risk management and life assessment programme of power plant components, particularly those with service-exposed materials, using data obtained from scoop samples, are described. Proposals for future exploitation and for improvement of the technique are addressed.

A 9Cr-3W-3Co-VNbBN steel, designated MARBN ( MAR tensitic 9Cr steel strengthened by B oron and N itrides), has been alloy-designed and subjected to long-term creep and oxidation tests for application to thick section boiler components in USC power plant at 650 o C. The stabilization of lath martensitic microstructure in the vicinity of prior austenite grain boundaries (PAGBs) is essential for the improvement of long-term creep strength. This can be achieved by the combined addition of 140ppm boron and 80ppm nitrogen without any formation of boron nitrides during normalizing at high temperature. The addition of small amount of boron reduces the rate of Ostwald ripening of M 23 C 6 carbides in the vicinity of PAGBs during creep, resulting in stabilization of martensitic microstructure. The stabilization of martensitic microstructure retards the onset of acceleration creep, resulting in a decrease in minimum creep rate and an increase in creep life. The addition of small amount of nitrogen causes the precipitation of fine MX, which further decreases the creep rates in the transient region. The addition of boron also suppresses the Type IV creep-fracture in welded joints by suppressing grain refinement in heat affected zone. The formation of protective Cr 2 O 3 scale is achieved on the surface of 9Cr steel by several methods, such as pre-oxidation treatment in Ar gas, Cr shot-peening and coating of thin layer of Ni-Cr alloy, which significantly improves the oxidation resistance of 9Cr steel in steam at 650 o C. Production of a large diameter and thick section pipe and also fabrication of welds of the pipe have successfully been performed from a 3 ton ingot of MARBN.

This paper reports on the latest in a series of projects aiming at the qualification of new and proven materials in components under a severe service environment. In the initial stages of the project (HWT I & HWT II), a test loop at Unit 6 of the GKM Power Plant in Mannheim was used to study the behavior of components for advanced ultra-supercritical (A-USC) plants made from nickel alloys at 725 °C under both static and fluctuating conditions. Due to recent changes in the operation modes of existing coal-fired power plants, the test loop was modified to continue operating the existing nickel components in the static section while applying thermal cycles in a different temperature range. HR6W pipes and valves were added to the bypass of the static section, and all components in the cyclic section were replaced with P92, P93, and HR6W components. The test loop achieved approximately 9000 hours of operation and around 800 cycles with holding times of 4 and 6 hours. After dismantling the loop, nondestructive and destructive examinations of selected components were conducted. The accompanying testing program includes results from thermal fatigue, fatigue, thermal shock, and long-term creep tests, focusing on the behavior of base materials and welds, particularly for HR6W, P92, P93, and other nickel-based alloys. Additionally, test results on dissimilar welds between martensitic steel P92 and nickel alloys A617 and HR6W are presented. Numerical assessments using standardized and numerical lifetime estimation methods complement the investigations. This paper provides insights into the test loop design and operational challenges, material behavior, and lifetime, including advanced numerical simulations and operational experiences with valves, armatures, piping, and welds.

The steam generation systems (SGS) of concentrated solar power (CSP) plants employ multiple heat exchangers arranged in series to convert thermal energy collected from the sun via a heat transfer fluid (HTF) to produce superheated steam in the Rankine cycle. Common CSP plant designs are based either on parabolic trough or central tower technology. The major Rankine cycle components consist of preheaters, evaporators, steam drums, superheaters, steam turbines, and water/air-cooled condensers, all connected through steel piping. For CSP plants capable of reheating the steam for improved efficiency, reheaters are also included in the Rankine cycle. In central tower design with directly heated water as the HTF, the receiver can also be considered part of the Rankine cycle. Operating experiences of CSP plants indicate that plant reliability is significantly impacted by failures in various components of the Rankine cycle. Many damage mechanisms have been identified, which include corrosion, thermal fatigue, creep, and stress corrosion cracking, among others. Much of the damage can be attributed to poor water/steam chemistry and inadequate temperature control. While damage in the Rankine cycle components is common, there is generally lack of comprehensive guidelines created specifically for the operation of these CSP components. Therefore, to improve CSP plant reliability and profitability, it is necessary to better understand the various damage mechanisms experienced by linking them to specific operating conditions, followed by developing a “theory and practice” guideline document for the CSP operators, so that failures in the Rankine cycle components can be minimized. In a major research project sponsored by the U.S. Department of Energy (DOE), effort is being undertaken by EPRI to develop such a guideline document exclusively for the CSP industry. This paper provides an overview of the ongoing DOE project along with a few examples of component failures experienced in the Rankine cycle.

Steel castings of creep-resistant steels are critical components in the high and intermediate pressure turbine sections of fossil fuel-fired power plants. As plant efficiencies improve and emission standards tighten, steam parameters become more stringent, necessitating constant enhancement of material creep resistance. Steel foundries alone cannot conduct necessary material development at an appropriate scale, so all power plant component suppliers cooperate to define optimal chemical compositions, perform test melts, creep tests, microstructure investigations, and test pilot components, such as through the COST program developing new 9-12%Cr cast steel grades. This paper illustrates a steel foundry's role in COST, describing the transfer of these new cast steel grades from research into commercial production of heavy cast components, outlining incurred problems, process development cycles, comparisons with low-alloy steels, welding tests, base material/weld investigations, heat treatment optimization, and casting of pilot components/weldability test plates to verify castability of larger parts and make necessary adjustments. Parallel to ongoing COST creep tests, the steel grades were introduced into commercial large component production, involving solutions to process-related issues, with over 180 components successfully manufactured to date, while further COST program developments present ongoing challenges.

In response to the need to reduce carbon dioxide gas emissions, Japan has been actively researching 700°C-class thermal power plants with a focus on improving overall plant efficiency. This technological advancement is fundamentally grounded in advanced materials development, encompassing the creation of high-strength alloys, fireside corrosion-resistant materials, and steamside oxidation-resistant alloys. A significant challenge emerged as some of the developed materials fell outside the scope of existing domestic technical standards. Moreover, the potential failure modes for advanced ultra-supercritical (A-USC) components operating at 700°C were anticipated to differ substantially from those observed in traditional ultra-supercritical (USC) components at 600°C. Consequently, researchers systematically examined and analyzed the potential failure modes specific to 700°C A-USC components, using these insights to establish comprehensive performance requirements. The research initiative, which commenced in June 2006, was strategically planned to develop a draft technical interpretation by March 2011. This paper provides a detailed overview of the investigative process, encompassing the comprehensive analysis of failure modes, the derivation of performance requirements, and the progression toward developing a new technical interpretation framework for high-temperature power plant components.

In order to improve thermal efficiency of fossil-fired power plants through increasing steam temperature and pressure high strength martensitic 9-12%Cr steels have extensively been used, and some power plants have experienced creep failure in high temperature welds after several years operations. The creep failure and degradation in welds of longitudinally seam-welded Cr- Mo steel pipes and Cr-Mo steel tubes of dissimilar metal welded joint after long-term service are also well known. The creep degradation in welds initiates as creep cavity formation under the multi-axial stress conditions. For the safety use of high temperature welds in power plant components, the complete understanding of the creep degradation and establishment of creep life assessment for the welds is essential. In this paper creep degradation and initiation mechanism in welds of Cr-Mo steels and high strength martensitic 9-12%Cr steels are reviewed and compared. And also since the non-destructive creep life assessment techniques for the Type IV creep degradation and failure in high strength martensitic 9-12%Cr steel welds are not yet practically established and applied, a candidate way based on the hardness creep life model developed by the authors would be demonstrated as well as the investigation results on the creep cavity formation behavior in the welds. Additionally from the aspect of safety issues on welds design an experimental approach to consider the weld joint influence factors (WJIF) would also be presented based on the creep rupture data of the large size cross-weld specimens and component welds.

Components exposed to the highest temperatures and mechanical loading in 700°C power plants are predominantly manufactured from nickel-based alloys, with ongoing material development for boiler and turbine components in this challenging temperature regime. This paper presents comprehensive investigations of various components, including tubing, membrane walls, and thick-walled structures constructed from nickel-based alloys. Qualification programs for boiler components have demonstrated the applicability of Alloy 617, with similar extensive programs and investigations currently underway for Alloy 263 and Alloy 740. Researchers have conducted detailed experiments and investigations to optimize and qualify welding consumables, aiming to transfer critical knowledge directly to component manufacturing processes. Recognizing the complexity of material performance, the study emphasizes the necessity of long-term material qualification, which extends beyond traditional creep behavior assessments to include detailed investigations of deformation capabilities following extended aging periods. These comprehensive evaluations are crucial for ensuring the reliability and performance of advanced high-temperature power plant components under extreme operational conditions.

This study addresses the welding challenges encountered when joining Haynes 282, a heat-resistant superalloy, to 3.5NiCrMoV high-strength low alloy steel (HSLA) for advanced power plant applications, particularly in thick-section components like rotors. The project demonstrated successful thick-section dissimilar metal welding up to 76 mm (3 in.) using two techniques: keyhole tungsten inert gas welding and conventional gas tungsten arc welding with Haynes 282 filler metal. Various groove weld geometries were evaluated, supported by computational weld modeling to predict and minimize weld distortion. The results validate these welding approaches for critical power plant components requiring both high-temperature performance and cost-effectiveness.

Creep behavior and degradation of creep properties of advanced 9-12%Cr ferritic steels are phenomena of major practical relevance, often limiting the lives of power plant components and structures designed to operate for long periods under stress at elevated temperatures. Because life expectancy is, in reality, based on the ability of the material to retain its high-temperature creep strength for a period of at least twice the projected design life, methods of creep property assessment based on physical changes in the material that are likely to occur during service exposure rather than simple parametric extrapolation of the short-term data are necessary. This work attempts to highlight the problem areas just in this respect. The proposed approaches are illustrated by recent experimental results on advanced high creep strength 9-12%Cr ferritic- martensitic steels (P91 and P92).

Research on high chromium ferritic materials for high temperature power plant components generally concentrates on the properties of the parent steel. Weldments, however, are often the weak link, leading to premature failures and associated forced outages and high maintenance spend. Clearly, consideration of the creep performance of weld metals and associated heat-affected zones (HAZs) in these materials is important. Despite this, relevant weldment creep rupture data are not commonly available, and weldment creep rupture “strength reduction factors” are not always known. This paper provides comment on the available information on parent materials, and highlights the need for the assessment of the creep performance of weldments. Strategies for increasing HAZ creep rupture strength are reviewed, and some available weldment data are considered. Less conventional welding processes (GTA/TIG variants and EB welding) appear to provide improved creep performance of weldments. They therefore merit further study, and should be considered for welding the new steel grades, particularly in supercritical and ultra-supercritical applications.

Preface for the 2016 Advances in Materials Technology for Fossil Power Plants conference.

For four decades, the Electric Power Research Institute (EPRI) has led groundbreaking materials research in the power industry, yielding significant cost savings across fossil, nuclear, and power delivery sectors. This paper outlines EPRI's fossil-related research, conducted through three major programs: Fossil Materials&Repair (P87 Base program), Materials-Fossil&Nuclear strategic program, and a supplemental program addressing key industry initiatives. EPRI's research focuses on understanding damage mechanisms, developing improved materials, enhancing life prediction methodologies, and advancing component degradation assessment. The paper highlights the synergy between EPRI's short- and long-term research initiatives, referencing several presentations from the 6th International Conference on Advances in Materials Technology for Fossil Power Plants. By showcasing EPRI's comprehensive approach to materials research, this overview demonstrates the institute's ongoing commitment to advancing power generation technology and efficiency.

Following the successful completion of a 14-year effort to develop and test materials which would allow advanced ultra-supercritical (A-USC) coal-fired power plants to be operated at steam temperatures up to 760°C, a United States-based consortium has started on a project to build an A-USC component test facility, (A-USC ComTest). Among the goals of the facility are to validate that components made from the advanced alloys can perform under A-USC conditions, to accelerate the development of a U.S.-based supply chain for the full complement of A-USC components, and to decrease the uncertainty for cost estimates of future commercial-scale A-USC power plants. The A-USC ComTest facility will include a gas fired superheater, thick-walled cycling header, steam piping, steam turbine (11 MW nominal size) and valves. Current plans call for the components to be subjected to A-USC operating conditions for at least 8,000 hours by September 2020. The U.S. consortium, principally funded by the U.S. Department of Energy and the Ohio Coal Development Office with co-funding from Babcock & Wilcox, General Electric and the Electric Power Research Institute, is currently working on the Front-End Engineering Design phase of the A-USC ComTest project. This paper will outline the motivation for the project, explain the project’s structure and schedule, and provide details on the design of the facility.

For future carbon neutral society, a novel thermal power generation system with no CO 2 emission and with extremely high thermal efficiency (~ 70 %) composed of the oxygen/hydrogen combustion gas turbine combined with steam turbine with the steam temperature of 700°C is needed. The key to realize the thermal power plant is in the developments of new wrought alloys applicable to both gas turbine and steam turbine components under higher temperature operation conditions. In the national project of JST-Mirai program, we have constructed an innovative Integrated Materials Design System , consisting of a series of mechanical property prediction modules (MPM) and microstructure design modules (MDM). Based on the design system, novel austenitic steels strengthened by Laves phase with an allowable stress higher than 100 MPa for 10 5 h at 700°C was developed for the stream turbine components. In addition, for gas turbine components, novel solid-solution type Ni-Cr-W superalloys were designed and found to exhibit superior creep life longer than 10 5 h under 10 MPa at 1000°C. The superior long-term creep strengths of these alloys are attributed to the “grain-boundary precipitation strengthening (GBPS)” effect due to C14 Fe 2 Nb Laves phase and bcc α 2 -W phase precipitated at the grain boundaries, respectively.

High temperature components with notches, defects and flaws may be subject to crack initiation and crack propagation under long-term service conditions. To study these problems and to support an advanced remnant life evaluation, fracture mechanics procedures are required. Since a more flexible service mode of power plants causes more start up and shut down events as well as variable loading conditions, creep-fatigue crack behavior becomes more and more decisive for life assessment and integrity of such components. For steam power plant forged and cast components, the crack initiation time and crack growth rate of heat resistant steels were determined in long-term regime up to 600 °C. Component-like double edge notched tension specimens have been examined. The results are compared to those obtained using the standard compact tension specimen. Crack initiation time and crack growth rate have been correlated using the fracture mechanics parameter C*. The applicability of the stress intensity factor K I to describe the creep crack behavior is also being assessed. A modified Two-Criteria-Diagram was applied and adapted in order to recalculate crack initiation times under creep-fatigue conditions. Recommendations are given to support the use of different fracture mechanics parameters in order to describe the long-term crack behavior under creep and/or creep-fatigue conditions.

The application of cold weld repair techniques in the power industry has been well documented. This type of repair is only considered when a conventional repair (involving post-weld heat treatment) is impracticable or the penalties of time and cost for conventional repair are sufficiently high. A typical cold weld repair in the UK has involved low alloy ferritic steel (½Cr½Mo¼V, 2¼Cr1Mo) components welded with nickel based SMAW consumables or ferritic FCAW consumables. Modified 9Cr steel components have been used in UK power plant since the late 1980’s for a number of applications, such as superheater outlet headers, reheat drums and main steam pipework. The problems associated with this material have also been well documented, particularly premature type IV cracking of welds on creep weakened modified 9Cr steel. RWE Generation UK have developed modified 9Cr cold weld repairs on headers, pipework and tubes. These repairs have been underwritten with extensive testing. This paper will describe the work performed on developing T91 cold weld repairs and where they have been applied on power plant.

A United States-based consortium has successfully completed the Advanced Ultra-Supercritical Component Test (A-USC ComTest) project, building upon a 15-year materials development effort for coal-fired power plants operating at steam temperatures up to 760°C. The $27 million project, primarily funded by the U.S. Department of Energy and Ohio Coal Development Office between 2015 and 2023, focused on validating the manufacture of commercial-scale components for an 800 megawatt power plant operating at 760°C and 238 bar steam conditions. The project scope encompassed fabrication of full-scale components including superheater/reheater assemblies, furnace membrane walls, steam turbine components, and high-temperature transfer piping, utilizing nickel-based alloys such as Inconel 740H and Haynes 282 for high-temperature sections. Additionally, the team conducted testing to secure ASME Code Stamp approval for nickel-based alloy pressure relief valves. This comprehensive effort successfully established technical readiness for commercial-scale A-USC demonstration plants while developing a U.S.-based supply chain and providing more accurate cost estimates for future installations.

There are main drivers for the design and assessment of steam turbine components of today such as demands for improved materials, higher plant cycling operation, and reduced life-cycle costs. New materials have been developed over the last decades resulting in advanced martensitic 9-10CrMoV steels already applied in different types of turbines successfully. Heavy cyclic loading getting more importance than in the past results in utilization of the fatigue capabilities at high and low temperatures which might lead to crack initiation and subsequent crack propagation. Fracture mechanics methods and evaluation concepts have demonstrated their applicability to assess the integrity of components with defects or crack-like outage findings. Based on realistic modelling of the failure mechanism, accurate prediction of crack sizes at failure state can be improved defining the appropriate damage criteria. Ductility is a main aspect for robust design but its value definition can depend on component type, design rules, real loading conditions, service experience, and material characteristics. The question which direct material parameter is able to serve as limit value in design and how it can be determined has to be solved. Examples of advanced analysis methods for creep crack growth and fatigue interaction involving the crack initiation time show that the reserves of new martensitic 9-10Cr steels in high temperature application can be well quantified. The creep rupture elongation A u and the loading conditions in the crack far field are main factors. If the A u value is sufficient high also after long-time service, the material remains robust against cracks. Investigations into the influence of stress gradients on life time under fatigue and creep fatigue conditions show that e.g. for 10CrMoWV rotor steel crack growth involvement offers further reserves. The consideration of constraint effect in fracture mechanics applied to suitable materials allows for further potentials to utilize margin resulting from classical design. The new gained knowledge enables a more precise determination of component life time via an adapted material exploitation and close interaction with advanced design rules.