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Structural Integrity is uniquely positioned to help power plant owners and operators meet the lifecycle challenges that face coal or gas fired plants, and combined cycle plants. We provide engineering and condition assessment services to the fossil power industry with more than thirty years’ experience tackling some of the biggest industry challenges such as seam welded piping, dissimilar metal welds, turbine bore cracking, and creep strength enhanced ferritic steels. Our success is rooted in an integrated, multidisciplinary approach that combines engineering analysis, advanced nondestructive examination, and materials evaluation combined with state-of-the-art digital solutions, to provide targeted and scalable asset lifecycle management solutions for fossil plant owners and operators.
In conventional coal and gas fired fossil plants, boilers are the most likely source of for a forced outage due to the plethora of damage mechanism that affect tubes, headers and piping. Because of this, Structural Integrity has well-defined techniques to optimize reliability through condition assessment and lifecycle management of various boiler components.
Most conventional fossil-powered generating stations have hundreds of thousands of operating hours and were originally designed for baseload duty. Today, these plants operate flexibly, experiencing load cycling, low load operation, start-stop cycles, and fast ramp rates which drive damage mechanisms that may not have been seen in the past. Superimposed on this are financial and resource constraints - reduced maintenance budgets, staff reductions, and fewer, shorter outages. Modern ultrasupercritical plants must endure higher operating temperatures and are constructed from newer materials with complex metallurgy that can result in challenges such as premature creep failures and oxide exfoliation which can occur even early in life.
Our comprehensive, integrated approach to boiler lifecycle management includes risk-based activities such as cycle chemistry review, inspections, fitness-for-service and metallurgical analysis that allows owners to operate with greater reliability, availability, and safety.
Pressure part failures not only raise personnel safety concerns, but they can be a major source of lost revenue for fossil-fired power plants. To minimize the potential for failures, unplanned outages and related business interruption and repair costs, we provide a comprehensive boiler asset management program that begins with a pressure-part audit (reviewing past operation, failures, inspections, etc.) to assign a health index to each component, and provide recommendations for future inspections, repairs and replacements.
Dispositioning cracking and damage is important to identify when repairs or replacements are necessary, particularly in headers and connecting piping where repairs can be complex. Fitness-For-Service (FFS) evaluations provide predictions of crack growth and remaining life to help set inspection intervals and provide critical defect sizes to guide disposition of NDE results. More generally, FFS assessments can explore the impact of changed operation (temperatures, ramp rates) and provide insight into failure modes such as leak before break.
To get to the root cause of boiler tube failures it is important to properly diagnose the underlying damage mechanism. Also, as part of a life management program, it is informative to occasionally remove tubes from service to understand their microstructural condition. We provide comprehensive tube failure and condition assessment services at our metallurgical laboratory and, with our knowledge of root causes, we can provide recommendations to avoid future failures. In addition to boiler tubes, we can also evaluate the root cause of other component failures from around the plant.
One of the critical aspects to proactive boiler life management is the detection of damage before a failure occurs. Along with periodic destructive analyses and analytical life assessments, non-destructive examinations are key to ensuring unit reliability. Our team of experienced engineers and NDE professionals use state-of-the-art ultrasonic and eddy current methods to detect and quantify damage in a range of boiler components including: circumferential cracking in water-walls, damage in tube dissimilar metal welds, and ligament cracking in headers (to name a few).
Cycle chemistry is a major factor in many of the damage mechanisms that affect boiler tubes. The optimization of cycle chemistry practices requires an understanding of industry best practices, familiarity with many boiler designs, and a detailed understanding of the possible damage mechanisms that can occur. Structural Integrity is the industry leader in reviewing cycle chemistry to avoid tube failures due to mechanisms such as corrosion fatigue, under deposit corrosion, pitting attack, and stress corrosion cracking.
The Header Online Damage Tracking App available in SI’s PlantTrack software provides real-time health status of headers and terminal tubes. There are many features in headers that are susceptible to service damage due to temperature fluctuations and imbalances. Cyclic (start/stop) operation can result in accumulation of fatigue damage at tube stub connections, or ligament cracks between tube bore holes. Periods of steady operation can result in accumulation of creep damage in header ligaments, branch connections, or seam welds. Stub/terminal tubes entering the header can also suffer creep and fatigue damage, as well as wall loss due to oxidation. Prediction of useful lifetime requires tracking of thermal transients and operating pressures and temperatures. Tracking conditions that lead to creep and fatigue damage in real-time, based on SI’s algorithms that use existing instrumentation combined with component geometry, provides accurate life consumption estimates. This allows trends in damage accumulation to be tracked and trended and gives engineers data to make better run, repair, replace decisions.
A wealth of data, information, and knowledge about a boiler is generated throughout its history. SI’s PlantTrack software includes a boiler module that provides users with a simple user-interface to permanently record tube leaks, repairs, and inspections, and map that data to interactive plant-specific drawings. It further allows users to create individual component inspection plans based on the operating history and geography. Also available is real-time damage tracking that continuously reports the instantaneous consumed life of critical components.
A coal fired plant in the US Midwest had plans to replace their entire finishing superheater based on what they considered a long service life, even though no failures had occurred. Structural Integrity's Materials Science Center examined four tube samples, looking at the microstructure and measuring the hardness, dimensions, and internal oxide. The results were fed into our proprietary boiler tube life model and determined that the tubes had been operating at lower temperatures than expected, and therefore had a significant remaining useful life yet. The plant was able to cancel the costly replacement, resulting in significant savings.
A boiler in operation more than 50 years with hundreds of dissimilar metal welds in the Superheater had experienced several failures. Structural Integrity performed a field inspection that found a few DMWs inside the furnace were at end of life and needed repair, but also noticed most of the Penthouse DMWs had questionable indications. With the plant facing the expensive prospect of extending the outage to repair all the penthouse DMWs, we examined samples in our metallurgical lab and determined those indications were due to welding flaws rather than creep damage. Analysis showed sufficient remaining life to postpone repairs until the next planned outage, allowing the plant to get back online as scheduled and avoiding the costly outage extension.
An aging coal plant in the US was challenged to produce a 10 year plan for capital improvements, but realized past inspections did not provide a clear picture of the remaining useful life of boiler and piping components. Structural Integrity was called to apply its health, consequence, and confidence methodology to benchmark the health of these systems. The output was a set of ‘component assessment snapshots' that provided a relative risk ranking. The highest risk components were then inspected, and their health re-assessed to determine the remaining useful life. The plant now plans to continuously update the component assessment snapshots to guide future outage and budgets.
Solving the
facing modern ultra-supercritical plants
The Heat Recovery Steam Generator (HRSG) is a vital part of a Combined Cycle (CC) plant, capturing the exhaust heat from the combustion turbine and converting that into steam. Being sandwiched between the combustion turbine and steam turbine puts the HRSG in a unique position having to accommodate requirements imposed by both those turbines. As a result, HRSGs experience significant thermal transients, operate under wide range of loads, and experience high steam temperatures and pressures. The HRSG is commonly provides all the feedwater heating, and frequently incorporates multiple pressure evaporators. Consequently, the HRSG can experience a huge range of damage mechanisms. To compound this, many HRSGs were originally intended for base-load operation and are now required to cycle. Modern HRSGs, now feature steam temperatures in excess of 1100F and utilize a number of modern alloys, which bring their own set of challenges. Fortunately, we have solutions to help you with life management of your HRSG.
We offer HRSG operational dependability assessments, creep and fatigue evaluations, component failure root cause analysis, water chemistry evaluations and training, P91/CSEF testing and assessment, design life analyses, and many other services to ensure more reliable HRSG operation.
HRSG tubes and headers (as well as drums and interconnecting piping) can suffer a wide range of damage mechanisms including thermal shock, corrosion-fatigue, flow accelerated corrosion, under-deposit corrosion, creep and fatigue. SI can provide audits of HRSG design and operation to evaluate which damage mechanisms may be active, assess likely lifetime and recommend inspection methods and inspection intervals, or suggest operational enhancement to mitigate damage, or design upgrades that may be worth considering. Our evaluations include assessments of the impact of cycle chemistry and selected water treatment regime. We also extensively evaluate thermal transients, including condensate formation/management (drain sizing), ramp rates, buoyancy, flow instability and imbalances. Evaluations can include assessment of steam drums to address drum nozzle cracking, or other potential concerns such as drum internal design/arrangement (e.g. dealing with swell on startup or during burner firing). Key headers can also be selected for detailed creep and fatigue assessment. This provides a comprehensive life management plan for the HRSG pressure parts based on sound engineering.
Operational and design reviews are performed to provide insight into cycle chemistry and possible concerns with the HRSG and other components in the water-steam system (e.g. steam turbine or condenser). This will diagnose concerns with water treatment regimes, chemical feeds or layup practice. The potential is identified for typical damage mechanisms such as corrosion-fatigue, flow accelerated corrosion (FAC), and under deposit corrosion. This is important because cycle chemistry influences around 70% of damage and failure mechanisms in HRSGs, while by contrast application of the optimum chemistry can eliminate the possibility of mechanisms such as FAC and under-deposit corrosion occurring. For plants that include air-cooled condensers (ACC), the FAC and cycle chemistry aspects of their operation are also included because of the importance of operating with the optimum chemistry to eliminate the possibility of serious FAC and the transport of iron corrosion products around the cycle. SI helps plant owners develop the optimum cycle chemistry to maximize availability and reliability under the flexible conditions the plant is required to endure.
With respect to combined cycle plants and HRSGs, limitations in accessing some components are expected. Further, tubing, piping, headers, and related components in these plants often have unique issues that are not experienced in conventional boiler units. For these reasons, working with Structural Integrity’s experienced resources allows for fine-tuning of inspection activities without wasting effort on lower-risk components. Specific actions to consider are affected by the age of the unit, the design and operating conditions, the historical performance of the components in question, cycle chemistry practices (which may involve a cycle chemistry review), and physical access.
With the latest in tools and technologies, Structural Integrity’s trained and experienced NDE professionals perform inspections for HRSG tubing, piping, and headers. Our methods and procedures address a wide-range of needs from oxide scale and component thickness measurements to tube and pipe weld examinations using linear phased array and TOFD technologies to specialized inspections for hydrogen damage and corrosion fatigue. In addition to our more common services, we develop custom inspection tooling and methods to evaluate specific damage mechanisms and geometries associated with new and unique issues.
Structural Integrity is an industry leader in Creep Strength Enhanced Ferritic (CSEF) steel such as Grades 91 and 92, and we have specific expertise related to the issues that these materials present. Our services address all aspects of CSEF design, procurement, fabrication, installation, operation, analysis, and inspection. Specific Structural Integrity services include field hardness mapping (on both new and in-service piping and components) to identify hardness-deficient zones, chemistry and microstructure evaluations to identify metallurgical risk factors that may result in premature failure, and in the case of components with possible service-related damage, linear phased-array ultrasonic examinations to locate cracks. For new construction, we can also review purchasing/processing specifications, welding and quality control programs, and provide vendor evaluation and on-site monitoring
Attemperators (aka Desuperheaters) have proven to be particularly problematic because of a combination of flexible operation and design deficiencies. We can review attemperator design, operation, maintenance, and control logic to identify deficiencies, assess the impact and provide advice on mitigations from modified control logic to design upgrades. We also offer online attemperator monitoring software as part of our PlantTrack software. Because the large thermal transients that can occur have caused significant cracking and through-wall leaks, there are serious implications for personnel safety and plant reliability. Hence having a good understanding of your attemperators is vital to a successful plant.
A combined cycle plant requested help with "an FAC problem" after a failure occurred at the top of the LP evaporator. The plant had planned to arrest the problem by raising the oxygen level, but a review by SI indicated the problem was two-phase FAC, which wouldn't be arrested by increasing oxygen. An assessment of the plant's cycle chemistry and a deterministic FAC analysis uncovered the feedwater operating at too low pH. Corrective actions including increased instrumentation, monitoring total iron in feedwater and drums, and gradually increasing the pH. The result is that the FAC has been arrested with no further failures.
A combined cycle plant in the western US needed to increase ramp rate significantly faster than it had traditionally operated. Structural Integrity was asked to analyze the effects of faster ramp rates so reviewed the design and operational characteristics, performed calculations of fatigue and creep damage and assessed the thermal flexibility of connected sections. The attemperator system was the limiting factor, so the plant implemented a new attemperator design and is installing SI's Attemperator Damage Tracking App to be warned if any damage occurs. As a result, the plant is now able to ramp at a rate 67% faster than before.
Offering a wide variety of services to
reliable HRSG operation
A 10-year-old combined cycle plant found indications/cracks at the toe of the HRSG HP drum downcomer nozzles in both of its HRSGs. With a short outage, dispositioning the damage and performing any repairs became the critical path so Structural Integrity was called to evaluate. The damage was corrosion-fatigue which, while common, still requires analysis and repair. With the recommended solution being to blend the welds to decrease the local stress concentration factor, calculations were performed to determine how much material could be safely removed. The quick turnaround allowed the repair to be done in confidence without having to extend the outage.
High-energy piping (HEP) systems in power plants contain critical components that require careful maintenance and inspection. Structural Integrity offers plant owners and operators a full range of HEP services, including HEP program development based on ASME B31.1 guidance, advanced inspection methodologies, industry-leading expertise in piping engineering and materials evaluations, and critical input for run/repair/replace decisions.
Structural Integrity offers a range of services related to HEP Program development and implementation, including analyses using our Vulnerability Index (Vindex) for risk-based inspection and PlantTrack, our knowledge/data management system. These are cost-effective tools for maximizing the efficiency of lifecycle management budgets. We promote use of real-time monitoring, finite element modelling, fitness for service analysis, non-destructive examinations, and metallurgical lab analysis for a complete HEP program.
In fossil and combined cycle plants, high-energy piping (HEP) systems, including main steam, hot reheat, cold reheat, and feedwater piping, are critical in terms of personnel safety and overall plant longevity. Because of the potential for long-term degradation of piping system materials, and the undesirable consequences of piping system failures, these systems require meticulous management. In addition, changes to the ASME B31.1 piping code have imposed regulatory requirements related to HEP programs. Structural Integrity offers its clients integrated, multidisciplinary HEP management programs to ensure the safe and reliable operation of these crucial systems.
Damage in high energy piping (HEP) components is problematic, not only from a personnel safety standpoint, but also because of the potential for significant consequences in the event of leakage or failure. Our wide range of HEP assessment services allows owners and operators to have a much higher comfort level when managing power generation assets within conventional fossil and combined cycle plants. The most successful programs rely on an integrated approach, and our methodologies are unique in the power generation industry. From design and operational reviews, evaluations of historical operating and inspection data, consideration of hanger and support records, system stress analyses (based on the current condition of the system), non-destructive examinations (NDE), material sampling and testing, and component lifing based on pipe condition and accumulated service damage, Structural Integrity can meet any need associated with piping condition assessments.
Some piping systems may operate in a regime where cycle chemistry can cause damage, such as flow accelerated corrosion (FAC), hence it is important to review the cycle chemistry as early in the life of a plant as possible, and to routinely review data to assure that undesirable conditions are avoided. Since catastrophic failure of tubing and piping can occur with little or no warning, FAC programs are designed to identify and address locations that are most susceptible to FAC damage, and to implement corrective actions to alleviate the potential for such damage to occur.
Critical engineering components and systems can exhibit problems or issues at any time. New systems can break down prematurely or fail to function as designed. Older systems can incur long-term wear or damage or fail because of other unidentified causes. Changes to the design or operation of a system may require an understanding of the current condition of the component or system. Structural Integrity can evaluate each of these scenarios using a multidisciplinary approach that includes materials specialists and analytical engineers experienced with assessing existing conditions and providing recommendations or overseeing changes to critical components or systems. We support inspection planning, serviceability assessment, remaining life prediction, repair/replacement guidance, and design evaluations of critical piping and hanger/support systems.
Structural Integrity is an industry leader in Creep Strength Enhanced Ferritic (CSEF) steel such as Grades 91 and 92, and we have specific expertise related to the issues that these materials present. Our services address all aspects of CSEF design, procurement, fabrication, installation, operation, analysis, and inspection. Specific Structural Integrity services include field hardness mapping (on both new and in-service piping and components) to identify hardness-deficient zones, chemistry and microstructure evaluations to identify metallurgical risk factors that may result in premature failure, and in the case of components with possible service-related damage, linear phased-array ultrasonic examinations to locate cracks. For new construction, we can also review purchasing/processing specifications, welding and quality control programs, and provide vendor evaluation and on-site monitoring.
Finding in-service damage in high temperature piping systems subject to creep requires different skills and procedures than performing a code-acceptance inspection. SI’s NDE professionals have been trained in advanced NDE techniques specifically designed for finding damage to equipment operating at high temperature and high pressure, including components made from advanced materials such as Grade 91. Once critical locations are determined, Structural Integrity’s NDE professionals perform high energy piping inspections with the latest in tools, technologies and techniques. Inspections for service-induced damage employs time of flight diffraction, linear and annular phased array technologies for girth welds and seam welded pipe. Also, code compliant UT examinations can be performed for new or replacement pipe installation per the requirements of B31.1 and B31.3. Once flaws are characterized, Structural Integrity’s engineers can assist with appropriate mitigation measures, including repair.
High Energy Piping systems that operate at high temperatures are subject to life-limiting damage mechanisms such as creep and fatigue. Since failures can be catastrophic, planned repair or replacement prior to failure is critical. To aid in this planning, SI provides real-time health tracking through it’s High Energy Piping Damage Tracking App. This App is an add-on module to the PlantTrack software. Using existing instrumentation that feeds data to the App, damage due to creep and fatigue is calculated, accumulated, and tracked in real-time, providing users valuable information on the health of individual welds within the HEP system.
Piping systems are often analysed and inspected to determine or verify the integrity of welds, supports, piping segments, attachments, etc. Inspections are typically non-destructive (e.g. mag particle, phased array, UTT, visual), but can also include destructive sampling methods (e.g. boat samples). Analyses can include stress analysis, fitness-for-service, etc. In all cases, valuable data is generated that can be used for future planning and run, repair, replace decision making. The challenge is keeping this data organized, readily accessible, and shared among stakeholders such as system owners, plant staff, planners, contractors, etc. PlantTrack’s Piping module provides users with a web application and database to track not only the data collected, but the future actions to be taken. Based on past results, users can quickly plan locations to be inspected or analysed sorted by risk, last inspection date, previous indications, etc. All of this data can further be mapped/overlaid onto interactive drawings of the piping systems.
An attachment failure on the HP steam line at a combined-cycle plant raised questions on the effectiveness of the plant’s HEP life management program so Structural Integrity was called and performed a 'gap' analysis. With areas of improvement identified, SI was further engaged to enhance the program and implement a risk-based approach for inspections, analysis, and monitoring and to implement SI’s PlantTrack software for managing the program. This met ASME B31.1 requirement and addressed critical issues beyond the scope of the code. The plant now has a program that incorporates inspection, monitoring, and analysis to continually assess the condition of the HEP system.
A seam weld through wall leak on a steam line at a unit with over 250,000 operating hours was cause for concern for the plant and its owners. Structural Integrity was engaged and after a failure analysis, a stress analysis using finite element modeling, and performing NDE on the entire length of the pipe, SI was able to determine the remaining useful life of the pipe sections. Some areas were replaced while others were assigned a future inspection interval based on the lifing calculations. The unit was returned to service with the confidence that the HEP system would continue to function for many more years.
Structural Integrity provides a comprehensive service for turbine and generator inspection and life assessment services for solid rotors, rotor bores, shrunk on disks, blade attachment dovetails, turbine blades, turbine main inlet sleeves and nozzle chambers, turbine and valve casings, generator rotor dovetails, retaining rings, coupling keyways, and other critical components. Our life assessment analytical services include EPRI®-licensed SAFER-PC© rotor analysis, EPRI LPRimLife© rotor disk rim dovetail analysis, EPRI RRingLife© generator retaining ring analysis, and finite-element stress analysis of shafts, turbine disks, blades, and other components. In the case of turbine failures, our metallurgical testing laboratory also offers a full range of testing services for rotor, disk, and blade failure analyses.
Our team brings an in-depth understanding of the complexities associated with turbine and generator operation and familiarity with industry issues, including known flaw locations and orientation in similar machines. This insight and experience leads to targeted inspections that maximize resources and minimize outage times.
Structural Integrity’s Turbine/Generator Group consists of industry-experienced engineers and technical staff that have developed and implemented numerous methodologies for evaluating the current condition of many types of generating equipment. Whether the issue is rotor bore condition, solid rotor assessment, blade attachments, inspection of keyways, dovetails, or other geometric features, nozzles, sleeves, rings, or any other critical component in a turbine-generator assembly, Structural Integrity can apply state-of-the-art inspection and analytical methods to provide accurate results. This allows for re-inspection recommendations that are made with confidence and prolong asset life.
Based on industry experience, and the ability to rely on seasoned engineering staff and metallurgists from across our organization, Structural Integrity has the capability to perform advanced analytical and inspection activities to accurately answer our clients’ questions regarding their valuable turbine and generator systems. Our life assessment services include use of EPRI® and general purpose finite element software. EPRI® software used includes SAFER-PC©, LPRimLife©, and EPRI RRingLife©.
Remaining life assessments of critical turbine and generator components are typically based on deterministic or probabilistic analyses, using conservative (worst case) material property data extracted from public domain databases. When those analyses don’t meet the owner’s operational needs, characterization of material samples from the critical component may provide key information to allow continued operation of units that would otherwise be retired based on database properties. Structural Integrity offers miniature sample removal services to support accurate material property characterization.
Because of the impact that even small failures can have on unit operation, consequential damage, repair timelines, and potential for future issues, turbine component failures are critical in terms of causal analysis. Structural Integrity’s metallurgists and engineers have extensive experience in evaluating the damage mechanisms and causes of turbine component failures. SI has the resources to apply a multidisciplinary approach to failure investigation, wherein technical staff in SI’s Material Science Center collaborates with analytical engineers, turbine specialists, and plant engineers to answer tough questions surrounding turbine failures and identify appropriate corrective actions.
Vibration monitoring is critical in power generation applications where vibrations can damage equipment, resulting in significant downtime and loss of revenue. It is particularly helpful to analyze turbine vibration data in greater detail during major events like startups and shutdowns, or before and after maintenance activities. Our experts can dive deeply into existing data and recommend additional instrumentation and diagnostics when needed. To monitor the potential for torsional fatigue damage on turbine generator shafts, we developed a product called Transient Torsional Vibration Monitoring System (TTVMS) to measure and record transient torsional events for subsequent analysis of shaft torsional fatigue life.
Structural Integrity provided an independent assessment of a repowered vintage steam turbine, after the OEM had recommended replacement. Component assessment included critical welds, piping, valves, turbine rotors and casings. The assessment consisted of material sampling, nondestructive inspection, and life assessment. Material sampling activities provided critical material properties. The nondestructive inspection activities identified damage that was recorded and dispositioned. For life assessment, analytical tools were applied to quantify operating stresses, predict progression rates, and develop component life estimates. The independent assessment identified 20+ years of service life for all major components, with recommended re-inspection intervals of 5-20 years, dependent on component.
A 1970's vintage Generator rotor was boresonic inspected by the OEM, after which the OEM recommended a bottlebore of a portion of the rotor bore, to remove indications that the OEM determined were life-limiting for continued operation of the rotor. Due to the cost involved, the owner wanted Structural Integrity's opinion. SI re-inspected and gathered material samples from the bore then performed an analysis of the rotor using the EPRI SAFER-PC code. SI's analysis indicated the rotor could continue to operate without a bottlebore and the owner was provided with a suitable re-inspection interval.
Minimizing risk and maximizing reliability are the key goals for an effective asset management program. An essential part of any effective program is a system that will warehouse the associated data. Simply storing the data is not sufficient, however. The data management system must be capable of mining and analyzing the data to transform that data into information which can be used to make informed and effective decisions. Through intuitive interaction with this information, knowledge is developed that helps you to proactively manage your plant. To that end, Structural Integrity has developed our data management program, PlantTrack™.
PlantTrack is a powerful, web-based software solution with features designed specifically for the power industry. PlantTrack helps utilities to manage all types of data related to power plant design, construction, operation, specifications, inspections, maintenance and repairs, and failure investigations. In addition to offline data management, online monitoring and engineering assessment capabilities can be added, providing an integrated solution for asset health management of stationary power plant components.
The PlantTrack boiler module provides users with a simple user-interface to record tube leaks, header cracks, repairs, and inspection data, and map that data to interactive plant-specific drawings. It further allows users to create individual component inspection plans based on the history and geography (location). The PlantTrack Boiler Module is a critical tool to assist in eliminating repeat tube leaks by facilitating root cause analysis, focus and speed up outage activities with defined acceptance criteria, as well as plan future inspections and repair actions with confidence based on predicted future tube conditions.
The PlantTrack piping module provides users with a web application and database to track not only the data collected such as weld inspections and hanger walkdowns, but the future actions to be taken. Based on past inspection results, users can quickly generate a list of locations or welds to be inspected in future outages, sorted by risk, last inspection date, previous indications, etc. All this data can further be mapped (overlaid) onto interactive drawings of the piping systems. This can greatly improve communication and collaboration with key stakeholders at your facility.
The PlantTrack balance of plant module allows users to manage the information, data, and knowledge for heavily engineered equipment such as turbines, pressure vessels, and environmental equipment. As with the piping and boiler modules, the application allows users to interact with data to plan when and where to perform inspections, as well as when and where to take corrective actions. Like the other modules, it considers risk, history (timeline), and geography (locations) and allows users to visualize data overlaid on equipment drawings to make and track decisions.
Life consumption of thermal power plant components is directly related to changes in load conditions. This relationship is becoming increasingly significant as more power stations are forced to react quickly to changes in the power grid, although most were originally designed for steady state operation. PlantTrack’s ability to interface with plant data historians and installed instrumentation, combined with Structural Integrity’s analytical capabilities, has enabled solutions for monitoring critical components and assessing their health status in real-time. This data is then available in a web-based format in PlantTrack, which has the additional benefit of saving utility engineers travel time between plants. Online damage tracking modules are available for attemperators, headers, tubing and piping of conventional coal and combined cycle plants.
A rural cooperative had an active HEP life management program but was struggling to manage the information used to support the program. As a solution, Structural Integrity's HEP PlantTrack Module was implemented. Since the program has been implemented, the process of planning for outages has been significantly streamlined. With the risk ranking and past history readily available and overlaid on drawings, the engineer/planner can quickly select the locations and generate a bid-package that includes the design information in short order. This has reduced the amount of time needed for planning outage inspections and ensured the work is focused on the most appropriate locations.
A supercritical plant in the US wanted a robust life management program for the components made from Creep Strength Enhanced Ferritic (CSEF) steel. The plant chose to implement Structural Integrity's HEP Online Damage Tracking App to provide real-time indications of how much life has been consumed at various locations. Using the app, the plant and corporate engineers view both the up-to-date life consumption and the trend of how life consumption rate has varied during different operating regimes. This information is viewed alongside inspection data to give the best assessment of overall equipment health.
Structural Integrity is an industry leader in materials testing, condition assessment, and failure analysis. The metallurgical experts at our Materials Science Center in Austin, Texas, a state-of-the-art laboratory, are well-equipped to tackle the toughest industry problems related to material performance. Our services include characterizing the condition of existing materials, identifying damage mechanisms such as thermal degradation, creep, oxidation, corrosion, and fatigue, evaluating the root cause of failures, and providing useful information for the ongoing use of components and materials that remain in operation.
When a tube, pipe, turbine blade, or other important component fails, identifying the damage mechanism and the cause of the failure is critical for developing remedial actions and preventing recurring failures. Knowing the real reason for the failure allows for implementation of the most appropriate corrective actions, which is especially important considering that applying the wrong corrective actions can allow future similar failures, or worse, can lead to new damage or failures. Our experienced metallurgists apply a variety of testing methods and their years of experience to reach accurate and useful conclusions.
The condition of a component’s microstructure can reveal information about fabrication and heat treatment, deterioration from damage mechanisms such as thermal aging, creep and embrittlement, or changes related to short-term failure events. Microstructural examination also helps determine the mode and cause of various corrosion and cracking mechanisms, based on the morphologies observed at component surfaces, in corrosion pits, or along fracture surfaces. Microstructural evaluation is typically done by Structural Integrity experts using a metallographic microscope but can also be performed using digital or scanning electron microscopes, when necessary.
Examination of fracture surfaces can help establish the cause of a fracture by providing information about the crack origin, the mode of propagation, and the age. Partial fractures can be opened in the laboratory and examined using similar means. Fractography is normally performed by visual examination, optical examination (stereomicroscope), and at high magnifications using digital or scanning electron microscopes. Fractography is often performed using energy dispersive X-ray spectroscopy, which is used to identify and evaluate elemental contamination on fracture surfaces or in areas of corrosion damage.
Scale and deposit buildup can reduce efficiency by acting as barriers to heat transfer, promote corrosion by allowing corrosive species to concentrate, or result from corrosive attack. Structural Integrity uses energy dispersive X-ray spectroscopy in conjunction with scanning electron microscope examination to identify the elements present in bulk deposits or in situ (within pits and cracks). Powder X-ray diffraction techniques can be used to identify compounds in bulk deposit samples. In general, these analyses of scale and deposits can often determine the nature, sources, and effects of deposits.
We use quantitative chemical analysis to ensure that component alloys meet the intended material specifications. Samples must typically be about the size of a nickel or larger to obtain accurate results. For some alloys, such as creep strength enhanced steels, trace elements that create a metallurgical risk factor and contribute to failure can also be identified.
Structural Integrity obtains hardness data to assess material condition, including evaluation of softening or microstructural transformation from overheating. Hardness values can also be used to estimate tensile strength for most ferrous materials. In the case of Grade 91 material, which is a common creep strength enhanced ferritic steel used in the power industry, hardness testing can be used as a screening tool to confirm appropriate post-weld heat treatment and associated creep properties.
Cryo-cracking is a technique that combines microstructural analysis and fractography to evaluate the presence of incipient creep damage or other unique forms of damage. We employ this technique most commonly on plug samples from long-seam welds in high energy piping to verify NDE findings and help determine the remaining useful life.
Structural Integrity uses in-place metallography and replication for microstructural analysis when examining large components that cannot be easily moved or when destructive sample preparation is difficult or not permissible. In-place metallography allows for quick, on-site evaluation of a component’s metallurgical condition or of damage mechanisms that have resulted in component failure.
An elbow from a Grade 91 high pressure steam drain line failed, resulting in a need for immediate repair/replacement. SI was asked to perform metallurgical testing to identify the failure mode and to provide information in support of the overall failure investigation. The elbow was found to have an abnormal internal shape, which was attributed to the original manufacturing process, and the failure was attributed to internal erosion along the extrados of the elbow. In addition to the localized erosion and wall thinning, incipient cracks were identified at the internal corners created by the abnormal shape, although these features were not directly related to the failure.
Structural Integrity was asked to analyze multiple failures of finned, 90Cu10Ni heat exchanger tubes that occurred shortly after an in-kind replacement. The previous tubes had reportedly lasted for more than twenty years. Examination and testing revealed that the tubes failed due to ID pitting corrosion primarily at locations where surface deposits were present. Tubes of this type rely on a passivated surface layer to prevent localized corrosive attack, and this protective layer was not present on the new (replacement) tubes. In the course of analyzing and identifying the failure mechanism, SI was able to provide information to potentially guide the client in "seasoning" the new tubes in order to reduce the chance for ongoing failures.
Structural Integrity was asked to perform metallurgical testing of a failed, high pressure, austenitic stainless steel check valve component. The analyses performed on the submitted valve component included fractography, metallography, hardness testing, chemical composition analysis, and energy dispersive spectroscopy. The failure mode was identified as stress corrosion cracking (initiation region) with propagation via environmentally assisted cracking (corrosion fatigue). Elongated inclusions identified within the austenitic microstructure were oriented parallel to the crack and likely affected the crack propagation process. In addition, smeared metal on the inner surface of the component was associated with machining processes during the original manufacture of the valve component.
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Cycle chemistry in fossil and combined cycle plants plays an under-appreciated, but critical role in plant reliability. Although cycle chemistry is often out of the spotlight, water and steam cycle products and practices have a very strong influence on component damage accumulation. Because the water and steam touch virtually all components within a power plant, non-optimized practices result in unintended (and often avoidable) damage in boiler and HRSG tubes, condenser tubes and feedwater tubes and piping, and steam turbines.
Structural Integrity has knowledgeable chemists and engineers that can help clients take control of complicated plant cycle chemistry, optimize plant performance, and promote long-term savings. Services include review of cycle chemistry programs, optimization of feedwater and boiler water treatment, optimization of HRSG cycle chemistry, elimination of flow-accelerated corrosion (FAC), elimination of steam turbine phase-transition zone damage, instrumentation consulting, and plant personnel training. If a component failure occurs, Structural Integrity has extensive experience with metallurgical testing and failure analysis to identify causative factors to prevent future or recurring failures.
During an inspection of a low pressure (LP) steam turbine, cracks were found emanating from the L-0 blade attachment areas. SI's metallurgical investigation revealed stress corrosion cracking and extensive pitting on phase transition zone (PTZ) surfaces with all the cracks initiating at pits. The chemistry assessment of the plant revealed: a) frequent condenser leaks of the brackish water above the plants shutdown limits, b) no measurements of drum carryover, and c) no shutdown protection for the LP turbine using dehumidified air. Cycle chemistry influenced failure and damage in the PTZ of the LP steam turbine include stress corrosion cracking and corrosion fatigue. Such failures are less frequent than boiler tube failures, but the damage resulting can be enormous. SI suggested that these deficiencies should be corrected and that a chemistry manual should be developed.
An east coast US triple-pressure combined cycle plant requested help with "an FAC problem" in the low pressure (LP) evaporator. They reported that the failure and damage was at the top of the evaporator close to the outlet header downstream of a bend in the tube and they were planning to arrest the problem by raising the oxygen level. A quick review by SI of the internal surface of the failure and other similarly positioned tubes indicated that the problem was two-phase FAC, which wouldn't be arrested by increasing oxygen. The field findings of two-phase FAC were later verified by examining tube samples at SI's Material Science Center. A two-day comprehensive assessment was conducted of the plant's cycle chemistry and a deterministic FAC analysis performed which uncovered the cause of the FAC being the feedwater operating at too low pH. Several corrective actions were taken including increased instrumentation, development of a program to monitor total iron in feedwater and drums, conducting a baseline chemistry monitoring, and gradually increasing the pH. The result is that the FAC has been arrested with no further failures.
