News & Views, Volume 52 | Online Monitoring of HRSG with SIIQ™/in Ben Ruchte, Combined Cycle, Company News, Fossil Power, Heat Recovery Steam Generator (HRSG), Kane Riggenbach, Monitoring, Monitoring Case Study, News, News and Views/by Structural Integrity
A CASE STUDY ON IMPLEMENTATION AT A 3X1 COMBINED CYCLE FACILITY (ARTICLE 1 OF 3)
By: Kane Riggenbauch and Ben Ruchte
SI has successfully implemented a real-time, online, damage monitoring system for the Heat Recovery Steam Generators (HRSGs) at a combined cycle plant with a 3×1 configuration (3 HRSGs providing steam to a single steam turbine). The system is configured to quantify and monitor the life limiting effects of creep and fatigue at select locations on each of the HRSGs (e.g. attemperators, headers, and drums – see Figure 1). The brand name for this system is SIIQ™, which exists as a monitoring solution for high energy piping (HEP) systems and/or HRSG pressure-part components. SIIQ™ utilizes off-the-shelf sensors (e.g. surface-mounted thermocouples) and existing instrumentation (e.g. thermowells, pressure taps, flow transmitters, etc.) via secure access to the data historian. The incorporation of this data into SI’s damage accumulation algorithms generates results that are then displayed within the online monitoring module of SI’s PlantTrack™ data management system (example of the dashboard display shown in Figure 2).
This article will be part of a series discussing items such as the background for monitoring, implementation/monitoring location selection, and future results for the 3×1 combined cycle plant.
- Article 1 (current): Introduction to SIIQ™ with common locations for monitoring within HRSGs (and sections of HEP systems)
- Article 2: Process of SIIQ™ implementation for the 3×1 facility with a discussion of the technical foundation for damage tracking
- Article 3: Presentation of results from at least 6+ months, or another appropriate timeframe, of online monitoring data
BASIS FOR MONITORING
The owner of the plant implemented the system with the desire of optimizing operations and maintenance expenses by reducing inspections or at least focusing inspections on the highest risk locations. The system has been in place for a few months now and is continuously updating risk ranking of the equipment and ‘action’ intervals. The ‘action’ recommended may be operational review, further analysis, or inspections. This information is now being used to determine the optimum scope of work for the next maintenance outage based on the damage accumulated. Like many combined cycle plants, attemperators are typically a problem area. Through monitoring, however, it can be determined when temperature differential events occur and to what magnitude. Armed with this information aides in root cause investigation but also, if no damage is recorded, may extend the inspection interval.
HRSG DAMAGE TRACKING
Many HRSG systems are susceptible to damage due to high temperatures and pressures as well as fluctuations and imbalances. Attemperators have been a leading cause of damage accumulation (fatigue) through improper design/operation of the spray water stations (Figure 5). In addition, periods of steady operation can result in accumulation of creep damage in header components (Figure 6) and unit cycling increases fatigue and creep-fatigue damage in stub/ terminal tubes and header ligaments (Figure 7). Monitoring the damage allows equipment owners to be proactive in mitigating or avoiding further damage.
Traditionally, periodic nondestructive examinations (NDE) would be used to determine the extent of damage, but in HRSGs this can be challenging due to access restraints and, in the case of the creep strength enhanced ferritic (CSEF) materials such as Grade 91, damage detection sensitivity is somewhat limited until near end of life. Continuous online monitoring and calculations of damage based on unit-specific finite element (FE) models (sometimes referred to as a ‘digital twin’) with live data addresses this issue.
Reliable life consumption estimates are made by applying SI’s algorithms for real-time creep and fatigue damage tracking, which use operating data, available information on material conditions, and actual component geometry.
SIIQ tracks trends in damage accumulation to intelligently guide life management decisions, such as the need for targeted inspections, or more detailed “off-line” analysis of anomalous conditions. This marks a quantum leap forward from decision making based on a schedule rather than on actual asset condition.
SIIQ can be configured to provide email alerts (Figure 7) when certain absolute damage levels are reached, or when a certain damage accumulation over a defined time frame is exceeded. In this way, the system can run hands-off in the background, and notify maintenance personnel when action might be required.
News & Views, Volume 52 | An SIIQ™ Primer/in Company News, Monitoring, News, News and Views/by Structural Integrity
POWER PLANT ASSET MANAGEMENT
SI’s technology differs from most systems by focusing on MODELING OF DAMAGE MECHANISMS (e.g. damage initiation and subsequent rate of accumulation) affecting components that, if a failure were to occur, would impact safety and reliability.
SIIQ™ is part of the next-generation approach for managing assets through online monitoring and diagnostic (M&D) systems. The advancements in sensor technology, signal transmission (wired or wireless), data storage, and computing power allow for ever more cost-efficient collection and analysis of ‘Big Data.’
The online monitoring module of SI’s PlantTrack™ data management system can retrieve operating data from OSIsoft’s PI data historian (or other historians, for that matter – see below for typical architecture). Access to data from the historian is critical for moving beyond the stage of detecting adverse temperature events from the local surface-mounted thermocouples. Examination of pertinent data from select tags (as seen in Figure 3 of the article beginning page 29) is reviewed by SI experts to help derive a more optimal solution to mitigate further events. The benefit of the real-time monitoring is to detect improper operation and diagnose prior to damage progressing to failure. Continuously monitoring the condition allows for early remediation and potentially avoiding a failure that would result in loss of unit availability and possible personnel injury. Further, if monitoring indicates no issues are occurring, it may justify deferring a costly inspection.
News & Views, Volume 52 | Forecasting the Life of a Mass Concrete Structure, Part Two/in Andy Coughlin, Company News, Concrete Modeling & Analysis, Critical Structures, Keith Kubischta, News and Views/by Structural Integrity
A CASE STUDY FROM THE FERMILAB LONG BASELINE FACILITY
By: Keith Kubischta and Andy Coughlin, PE, SE
REFRESHER OF PART 1
From part one of the article (see News and Views Volume 51), we looked at the performance of a unique tubular mass concrete structure – the decay region of Fermilab’s Long Baseline Neutrino Facility – under complex thermal loading and thermal expansion. In the process of colliding subatomic particles in an accelerator and beaming them across the country underground, the facility contends with a massive amount of heat, an active nitrogen cooling system to remove energy, and shielding necessary for the surrounding environment. As we discussed in Part 1, Structural Integrity assisted with the design of the concrete structure by calculating the pertinent structural and thermal behavior under normal operation. Now for Part 2, we focus on forecasting the future life of the structure using advanced capabilities in analysis and delve into the actual life of this concrete structure while considering the construction process, a 30 year planned cycle of life, and how these influence planning for structural monitoring systems. In doing so, we attempt to answer a larger question: What can we learn from this structure that could be applied to other past and future structures?
These methods are not only applicable to new structures. Armed with the knowledge we can gain from record drawings, visual inspection, and non-destructive examination, SI is able to predict the life of concrete structures, new and old, giving key insights into their behavior in the future.
HEAT OF HYDRATION
In understanding the life of a structure, we must first start at the beginning as the concrete is first poured where another heat transfer takes place. Contrary to popular belief, concrete does not “dry”, rather it “bakes” itself during the curing process. As concrete is poured, it begins heating up internally through an exothermic hydration reaction between water and cement. The effect of the heat of hydration can usually be ignored in typical thin-walled structures. In larger mass concrete structures, however, the heat generation can cause significant degradation and built-in damage that can affect the structural performance throughout the entire life of the facility.
A secondary subroutine as part of the ANACAP models is used for heat of hydration specific for construction analysis to convert the temperature rise into volumetric heat generation rate for thermal analysis. When heat is trapped deep inside the structure and can’t escape, the concrete exhibits a temperature rise similar to the curve in Figure 2, which is a function of the concrete mix proportions.
For the operating conditions covered in Part 1, the coupled 3D thermal stress analyses performed on this project were thermal conduction steady-state analyses. Construction of such a large concrete structure is subjected to additional requirements, and a Nonlinear Incremental Structural Analysis (NISA) was performed to evaluate the structure under the construction loadings. Herein, the thermal analysis during the concrete placement sequence requires a transient numerical solution methodology. This thermal analysis was used to monitor additional requirements for temperature during concrete placement, and a mechanical NISA study monitored the movement of the central cooling annulus vessel. The complete NISA coupled thermal-stress analysis simulated the entire construction phase over the period of a year and a half of the planned construction schedule. To accomplish this, the model was segmented into 164 concrete pours, each one activated (turned on) within the model on a specific day outlined in a construction schedule, as shown in Figure 3. As the concrete is poured on its specific day, the heat of hydration begins to heat up the internals of the concrete, the outside ambient temperature pulls the heat away from the concrete, and formwork insulates the heat transfer temporarily before being removed. As each new concrete segment is poured (activated in the simulation) it begins a new heat cycle, shedding heat into surrounding segments, changing surfaces that are exposed to air, or where the formwork is located. Upon completion of the thermal NISA study, Structural Integrity could advise on peak temperatures of each pour (Figure 4), compare internal to external temperatures and make optimal recommendations for insulation to keep the concrete from cooling too fast.
With the thermal NISA study completed, we then coupled the thermal with the mechanical stress analysis following a similar procedure. The model was broken up into the same 164 segments, with the reinforcement separated into individual segments. As a segment was poured, its weight was first applied as pressure on surrounding segments before the segment cured enough and took load. Formwork was considered a temporary boundary condition (simulated with stiff springs): activated then removed when appropriate. The concrete internal reinforcement was activated with each concrete segment. The cycles continue with each additional segment added. The concrete material for each segment had its own values for aging, creep, shrinkage, and thermal degradation for when the concrete was placed. The effect of creep and shrinkage could be significantly different for concrete poured on the first day and concrete that is poured a year later. Mechanical tensile strain, a proxy for cracking, was plotted as shown in Figure 5.
A critical issue of concern was the steel annulus structure at the center of the concrete tunnel. The entire steel structure was placed prior to concrete being poured around it. The steel structure was affected by the thermal and mechanical loads of each concrete pour. Structural Integrity showed this structure “breathing” as thermal/mechanical loads pass from each concrete pour into the steel structure. Armed with a complete picture from the NISA stress analysis, Structural Integrity could show the animation of annulus movement, check the out-of-roundness, and advise on reinforcement placement.
During the design phase, reinforced concrete structures are typically designed for a bounding range of expected loads, to include thermal load cycles, periodic live load variations, and/or vibration from mechanical equipment. Up to this point, the design phase analysis started from a “pristine” uncracked structure and applied the expected load with the beam and cooling at full power. Seldom is the cumulative impact of cyclic loading considered for the expected service life of the structure. Structural Integrity, having performed the NISA study, now had significantly more accurate state of the structure with expected cumulative damage already built-up. This gave us the unique opportunity to extend the analysis from the current state through the lifecycle of the structure, comparing the “pristine” to the “cumulative” case.
The expected life of the structure is 30 years of operations with the beam running for no more than nine months a year and three months off. These cycles are grouped together in either seven- or five-year blocks with a rest period of two years for maintenance or upgrades in between. The experiment starts small, ramping up the power to half the total output for the initial seven years. For the lifecycle assessment, time is still a critical element, not just for properties of concrete affected by time but the physical computational time. The transient thermal analysis would be too time intensive to run over the 30 years of life that we want to observe. To simulate the thermal cycles, the beam steady-state thermal response was calculated at each peak power level. This provided different thermal states of power, which the mechanical analysis could switch on or off as needed and interpolate between them to give a simulated ramp of power. The computational time could then be utilized on the mechanical stress lifecycle assessment.
With the completion of the lifecycles analysis, Structural Integrity could once again provide valuable information to the researchers and designers: deformations of the entire structure, deformations of the annulus, out-of-roundness of the annulus (Figure 6), estimates of crack width, etc.
Most importantly, we can answer and show comparisons between the designed load from a “pristine” model analysis to those from the “cumulative” analysis.
Even prior to the lifecycle assessment, the cumulative damage at the end of the NISA study signaled different behavior in the expected cracking (Figure 7). From the construction process, the concrete showed cracking near the boundaries between each concrete pour. These developed due to the natural thermal cycling of the construction process. The lifecycle thermal loading continued to push and pull the structure adding to the already existing cracks. Previously, the boundary point between the fixed rail and sliding rail section concentrated the thermal loading to induce significant cracking. Now the stress will be more evenly distributed throughout the upstream section. The cracking during construction provided natural thermal breaks along the whole length of the structure.
SI then turned toward an additional question, where does all this excess heat go as the beam is cycling power? The shielding concrete is still heating up to over 60 degrees Celsius at the exposed surfaces. The air around the shielding concrete is trapped by the decay tunnel and venting conditions are unknown. We would need to produce a calculation based on the transfer of heat from the shielding concrete to the surrounding air/access tunnel, to the decay tunnel itself, and then the surrounding soil. Assuming the worst-case scenario, a point was selected along the length of the tunnel that produces maximum temperatures in the concrete. The cross section at this point is turned into a 2D model for use in a thermal analysis conducted as steady-state and transient to explore the heat transfer into the surrounding sections. A temperature profile of the decay tunnel wall was used to check its design from the thermal gradients, shown in Figure 9. The temperature of the air space between the structures can be monitored help in planning for when the tunnel can safely be accessed.
Engineers at SI are always eager to add data to our models. As this structure is constructed and put into service, the actual construction and startup sequence is likely to change, allowing for the model to be rerun and the lifecycle projection recalculated. Furthermore, data from temperature sensors and crack monitoring gauges could potentially help calibrate the model based on observed conditions to improve the accuracy of our projections moving forward. This methodology is applicable today to existing aging concrete structures where the lifecycle projection can be calibrated to existing observed conditions and data from online monitoring and non-destructive examinations.
Structural Integrity successfully developed expanded capabilities to model thermodynamics for the energy deposition and nitrogen cooling system. SI pushed the capabilities of our concrete model to capture over 30 years of construction and operations. Along the way, SI showed that our advanced modeling, combined with our advanced concrete model, positively influenced the design of the structure, and heavily supported the design and research teams with valuable information. The robustness of the calculation showed that SI is the present and future of concrete structure analysis.
SI demonstrated that our advanced modeling, combined with our advanced concrete model, positively influenced the design of this structure and heavily supported both the research and design teams with valuable information.
News & Views, Volume 52 | Understanding the Effects of Hydrogen Blending on Pipeline Integrity/in Company News, News, News and Views, Oil and Gas Pipeline, Owen Malinowski, Pete Riccardella, Pipeline Integrity, Scott Riccardella/by Structural Integrity
OIL & GAS SAFETY & RELIABILITY
By: Scott Riccardella, Owen Malinowski & Dr. Pete Riccardella
Structural Integrity Associates is focused on evaluating the impact of hydrogen blending on pipeline integrity and establishing a roadmap for our clients to maintain the safety and integrity of their aging natural gas steel transmission pipelines.
Hydrogen is widely recognized as a viable, clean alternative energy carrier. Recent advances in technology for clean hydrogen production, as well as renewed governmental and organizational commitments to clean energy, have intensified interest in utilizing the existing natural gas pipeline infrastructure to transport hydrogen from production sites to end users. Energy companies are pursuing strategic pilot programs to evaluate the capacity of their natural gas transmission and distribution pipeline systems to safely transport blends of natural gas and hydrogen. These pilot programs demonstrate the commitment of energy companies to facilitate environmentally responsible energy production and consumption while identifying and investigating potential challenges to pipeline safety and integrity associated with hydrogen blending.
KEY ELEMENTS OF THE EVALUATION INCLUDE
- Completing a critical threat review using a phenomena identification and ranking table (PIRT) process with a team of experts.
- Developing a statistical model for evaluating accelerated fatigue crack growth (FCG) in a hydrogen blend environment.
- Developing a statistical model for evaluating reduced fracture resistance (hydrogen embrittlement).
- Analyzing the impact of FCG and hydrogen embrittlement on the probability of rupture (POR) due to key threats such as stress corrosion cracking (SCC), longitudinal seam weld defects, and hard spots.
- Implementing a joint industry project (JIP) to adapt SI’s APTITUDE software tool for evaluating predicted failure pressure (PFP) and remaining life resulting from SCC and FCG in a hydrogen blend environment.
CRITICAL THREAT REVIEW
As part of a systemwide evaluation for one of our clients, a large North American Pipeline Operator, a critical threat review using a PIRT process was conducted to comprehensively understand the potential impact of hydrogen blending on steel natural gas transmission pipeline integrity. To ensure a thorough and accurate PIRT was completed, a panel consisting of experts in metallurgy, fracture mechanics, hydrogen effects on steel properties, and pipeline operations was assembled. A vital part of the process was a series of meetings conducted with the pipeline operator, systematically identifying and ranking the importance of various phenomena that could adversely affect the safety and reliability of energy transportation through the operator’s existing transmission pipeline system.
The PIRT panel reviewed all known pipeline integrity threats and identified potential unknown or unexpected threats that could be influenced by the presence of hydrogen in the operator’s transmission pipeline system. The process also assigned priorities for future research that may be needed to support that objective.
ENHANCED FATIGUE CRACK GROWTH
Significant research exists on the effect of hydrogen on FCG of pipeline steels and was referenced in this exercise. To gather the most relevant information possible, the project team compiled and analyzed data from numerous client-specific FCG tests of samples taken from the pipeline system in the targeted environment. These sample systems were exposed to equivalent hydrogen blend levels of 5%, 10%, 20%, and 100%. Over 2,200 data points were compiled and analyzed to develop trend curves and associated statistical variability. Data exhibited a significant increase in FCG rates (Figure 1) at relatively low hydrogen blend levels. ASME Code Case 2938 was reviewed and empirically fit with the analyzed data.
Hydrogen is known to have an embrittling effect on carbon steels, such as those used in gas transmission pipelines. When an internal pipe surface is exposed to high-pressure hydrogen or a high-pressure mixture of hydrogen and natural gas, hydrogen gas can disassociate into hydrogen atoms, which can then be adsorbed into the steel and lead to material property degradation (such as reduced fracture resistance). Dislocations and defects in the steel can also act as hydrogen traps, leading to even higher hydrogen concentrations at the location of already vulnerable manufacturing defects and service-induced cracks. Reduced fracture resistance at such sites could increase the adverse effect on pipeline integrity by leading to more frequent pipe failure events.
Based on available data from the literature and input from the PIRT expert panel, the project team developed trend curves of percent reductions in fracture resistance due to hydrogen exposure (knockdown factors) relative to fracture toughness in air. From this analysis, a reasonably conservative approximation, including statistical variability, was developed for the region of interest (hydrogen/natural gas blend levels up to 20% – Figure 2). Additional research and data analysis are currently underway that may further validate the relationship and better study this effect at low hydrogen partial pressures, as well as confirm the knockdown effect on lower toughness pipeline materials, such as electric resistance welded (ERW) seam welds.
PROBABILISTIC FRACTURE MECHANICS
SI has developed Synthesis™, a Probabilistic Fracture Mechanics (PFM) tool that calculates the probability of rupture (POR) for various cracks and crack-like defects that have caused oil and gas pipeline failures. The software incorporates statistical distributions of all important parameters in a pipeline fracture mechanics calculation that uses a Monte Carlo analysis algorithm that randomly samples from each distribution and runs millions of simulations to estimate the probability of rupture versus time. To evaluate the impact of hydrogen blending, Synthesis has been adapted to incorporate the effects of hydrogen on pipeline steel properties (enhanced FCG and hydrogen embrittlement) and thus the ability to compare PORs with and without hydrogen blending. The modified software was then applied to several pipelines in the operator’s system to determine the POR ratio between various hydrogen blend levels and pure natural gas. Additionally, Synthesis can evaluate the effects of various mitigation measures, such as hydrotests and In-Line Inspections, that could be applied before injecting hydrogen (Figure 3). The calculated PORRs will allow the operator to prioritize pipelines and associated mitigating actions that may be more or less favorable for hydrogen blending.
APTITUDE™ JOIN INDUSTRY PROJECT
SI has also established a JIP to adapt the APTITUDE PFP software program to handle some additional challenges presented with blending hydrogen with natural gas. Advancements include modifications that address enhanced FCG and hydrogen embrittlement. Further research to close gaps identified during the PIRT process is also being pursued through PRCI and other forums. Availability to join the JIP still exists, but space is limited – Please contact us if you would like to participate.
Structural Integrity Associates and C2C Technical Services Announce the Formation of SI Solutions in Partnership with Jumana Capital/in Company News, News/by Structural Integrity
CHARLOTTE, NC – Structural Integrity Associates (“SI”) www.structint.com, a leading specialty engineering consultant in the power and utility industry, and C2C Technical Services (“C2C”) www.c2ctechnicalservices.com, a leading electrical engineering and electrical field service company, are pleased to announce the formation of SI Solutions, LLC (“SI Solutions”) in partnership with Jumana Capital (“Jumana”) www.jumanacapital.com, a Houston, TX-based private investment firm specializing in partnerships with entrepreneur led companies.
SI was founded in 1983 in San Jose, CA, as an engineering and consulting firm dedicated to the analysis, control, and prevention of structural and mechanical failures with a core focus on critical equipment and structures in the power generation and utility infrastructure. Living true to the motto, “Powered by Talent and Technology,” SI has established itself as an innovative and responsive resource for answering any challenge ranging from R&D to engineering, metallurgy, fabrication, and non-destructive evaluation (NDE).
Texas City, TX-based C2C provides electrical engineering and specialty field services, including automation, instrumentation, electrical services, and technical staffing services for critical infrastructure maintenance within the renewables, petrochemical, and refining sectors.
SI Solutions will be a leading provider of mission-critical power and infrastructure engineering, testing, and maintenance services focused on existing assets. The platform will have more than 500 employees and nine offices, serving customers across the U.S. and internationally. The leadership team of SI Solutions will be comprised of the management teams of both SI and C2C, including C2C founders Charles Roachell and Craig Miller. Mark Marano, the former COO of the Westinghouse Electrical Company, came out of retirement to become the CEO of SI in February 2020 and will be the CEO of SI Solutions, in addition to remaining the CEO of SI. The CFO of SI Solutions will be Michelle Digilormo; Cam Tran will serve as Executive Director of HR.
“The SI Solutions platform with SI and C2C is the perfect fit for both companies. The combination enhances both platforms’ ability to grow and better serve client needs through additional investments in research and development, technical capabilities, field service offerings, and geographic reach. I am very excited about the future of SI Solutions,” said Mark Marano, CEO of SI.
“We are proud of what we’ve built at C2C and are excited to continue to drive growth in this next chapter”, says Charles Roachell, founder and co-president of C2C, “we believe our partnership with SI creates a best-in-class engineering and specialty service platform, led by a culture of safety and best practices. We will deliver the highest quality services to our customers and employees. We are excited to take the next step in building our platform”.
“The cultural fit of SI and C2C is unmatched in the industry”, says Craig Miller, founder, and co-president of C2C. “We value our highly skilled employee base and believe the combination of SI and C2C will create excellent opportunities for our employees to continue their professional and personal development. SI Solutions has an extremely bright future that we’re thrilled to be a part of”.
Chris Martin, Chief Investment Officer and Managing Director of Jumana Capital remarked, “SI Solutions is extremely well positioned to help meet the growing needs for asset management, compliance, maintenance, repair, and upgrade within the power generation, utility infrastructure, chemical, refining, and critical structures sectors in the United States and abroad. We are building something extraordinary and are excited for what the future holds for SI Solutions”.
Manager of Marketing and Communications
Structural Integrity Associates, Inc
High Energy Piping (HEP) Seminar 2023/in Company News, High Energy Piping (HEP), News/by Structural Integrity
January 31ST – February 2ND 2023
Our High Energy Piping (HEP) Seminar for the Power Industry will be held over 2.5 days (January 31st – until noon on February 2nd) in Austin, TX. During this time, we’ll share our comprehensive expertise on specific topics geared towards being proactive with regards to managing these assets. As the energy landscape has shifted and the call for more flexible operation has increased, it’s important that strategies are in place to ensure personnel safety and unit reliability are maintained. SI aims to provide attendees with a rich educational experience surrounding the following technology areas to provide a holistic review of component health:
THIS SEMINAR IS ESPECIALLY RELEVANT FOR
- Plant Managers
- System Engineers and Managers
- Corporate Piping Engineers
- Engineering and Maintenance Managers
- Anyone interested in gaining knowledge of high energy piping systems is welcome
- Ben Ruchte – Director, Senior Metallurgist
- Kane Riggenbach – Senior Consultant, Analytical Services
- Steve Gressler – Technical Director/Account Executive
Development and Management of an HEP program
- Elements of a program
- Components and systems included
- Code requirements
- Best practices
Stress analyses (explanation of the intricacies, when, what, and how to apply)
- Creep redistribution
- Creep lifetime prediction
- Creep crack growth
- Fatigue: aspects of cycling (operational data needs)
Metallurgical analyses (lab tour of SI’s Materials Lab, which may include an interactive review of samples)
- Piping damage mechanism
- Industry issues
- Grade 91 refresher/update
Application of NDE (new techniques, post-processing methods, when, what, and how to apply)
- Code versus serviceability examinations
- Post-processing methods
- Spray-on transducers
- Technique and component matching
Continuous monitoring and data management
- Data to be managed
- Online monitoring damage tracking
Tuesday, January 31st – Thursday, February 2nd
8:00am to 5:00pm Tues. and Wed. 8:00am to 12:00pm on Thurs.
Lone Star Court
10901 Domain Drive Austin, Texas 78758
We have negotiated a rate of $199/night plus taxes, you must book before January 10th to receive group rate. For reservations call 855-596-3398 and mention “SI HEP Seminar” to receive the group rate. Or you can book online using our booking link HOTEL REGISTRATION.
REGISTRATION CLOSED 2023
News & Views, Volume 51 | Optical Microscopy Applications and Benefits/in Clark McDonald, Company News, Materials Laboratory, News and Views/by Structural Integrity
By: Clark McDonald
In the world of metallurgical failure analysis, areas of interest on broken parts can be colorful or drab, three-dimensional or flat, and most importantly, very big or very small. A big part of failure analysis work is telling the story, explaining the failure mode, or in some cases, showing that critical piece of evidence that explains why a metal component has failed. From wide-angled lenses to extremely high magnification scanning electron microscope imagery, documentation of failed components is a big part of the presentation.
In this edition of Structural Integrity’s Lab Corner, we wanted to provide some interesting content related to that middle-of-the-road region of magnification; closer than macro-photography but farther away than the 100X to 5000X magnifications that cover most of the applications requiring scanning electron microscopy. In other words, the comfortable world of optical microscopy, where colors, shapes, and even surface textures are part of the story. To do this, we’ve chosen some images that show the usefulness of quality optical microscopic documentation. Each of the provided examples include a brief description along with specific comments on the benefits of optical microscopy for that project, where applicable.
News & Views, Volume 51 | Drone Inspections/in Company News, Jason Van Velsor, News and Views, Non-Destructive Evaluation, Robert Chambers/by Structural Integrity
SI EXPANDED CAPABILITIES
By: Jason Van Velsor and Robert Chambers
Structural Integrity (SI) has recently added drones to our toolbox of inspection equipment. Using drones, inspectors are able to complete visual inspections safely and more efficiently. Applications of drones for visual inspections include plant and piping walkdowns, structural inspections and atmospheric corrosion monitoring (ACM) of exposed pipeline.
Pipe hanger walkdowns at fossil and combined cycle plants are part of a routine inspection process. During these inspections, the inspector is required to view and mark down pipe hanger positions and assess their condition. While some hangers provide easy access for the inspector, this is not always the case. Some of these may be located in elevated positions that require the plant to build out scaffolding, which not only increases the cost, but also can put the inspector at risk when working at elevation. With the use of drones, the inspector can fly up to the pipe hangers from a safe location and get a live high-resolution video feed from the camera mounted on the drone. Saving pictures and the video footage can also allow the inspector to go back and review the footage at a later time.
ACM is another example where drones have proven to be a useful tool. ACM inspections of outdoor above ground pipelines are typically done by
walking down the pipeline and recording any signs of atmospheric corrosion. There are many occasions where the pipeline will be elevated or cross over rivers and railroads, requiring scaffolding or fall protection. By using a drone to fly along the pipeline, the inspection can be completed much more efficiently and safely. In situations where a GPS signal is available, such as outdoor pipeline inspections, the GPS coordinates can be saved with each photo. Custom SI-developed software can then automatically compile the acquired images and create a KML file to be viewed in Google Earth, allowing the client to get an overview of the inspection results.
Moving forward, SI plans to utilize these drones for more than just visual inspections. Possible applications could include using drones to perform ultrasonic thickness testing or Structural Integrity Pulsed Eddy Current (SIPEC™) examinations. All of SI’s pilots in command hold valid FAA Part 107 certificates and pilot registered drones.
News & Views, Volume 51 | Materials Lab Featured Damage Mechanism/in Company News, Heat Recovery Steam Generator (HRSG), Materials Laboratory, News and Views, Wendy Weiss/by Structural Integrity
PITTING CORROSION IN CONVENTIONAL FOSSIL BOILERS AND COMBINED CYCLE/HRSGS
By: Wendy Weiss
Pitting is a localized corrosion phenomenon in which a relatively small loss of metal can result in the catastrophic failure of a tube. Pitting can also be the precursor to other damage mechanisms, including corrosion fatigue and stress corrosion cracking. Pits often are small and may be filled with corrosion products or oxide, so that identification of the severity of pitting attack by visual examination can be difficult.
Pitting is a localized corrosion attack involving dissolution of the tube metal surface in a small and well-defined area. Pitting corrosion can occur in any component in contact with water under stagnant oxygenated conditions. Pitting in economizer tubing is typically the result of poor shutdown practices that allow contact with highly-oxygenated, stagnant water. Pitting also may occur in waterwall tubing as a result of acidic attack stemming from an unsatisfactory chemical cleaning or acidic contamination.
Pits that are associated with low pH conditions tend to be numerous and spaced fairly close together. The pits tend to be deep-walled compared to the length of the defect. A breakdown of the passive metal surface initiates the pitting process under stagnant oxygenated conditions. A large potential difference develops between the small area of the initiated active pit (anode) and the passive area around the pit (cathode). The pit will grow in the presence of a concentrated salt or acidic species. The metal ion salt (M+A-) combines with water and forms a metal hydroxide and a corresponding free acid (e.g., hydrochloric acid when chloride is present). Oxygen reduction at the cathode suppresses the corrosion around the edges of the pit, but inside the pit the rate of attack increases as the local environment within the pit becomes more acidic. In the event that the surfaces along the walls of the pit are not repassivated, the rate of pit growth will continue to increase since the reaction is no longer governed by the bulk fluid environment. Pitting is frequently encountered in stagnant conditions that allow the site initiation and concentration, allowing the attack to continue.
The most common cause of pitting in steam touched tubing results from oxygen rich stagnant condensate formed during shutdown. Forced cooling and / or improper draining and venting of assemblies may result in the presence of excess moisture. The interface between the liquid and air is the area of highest susceptibility. Pitting can also be accelerated if conditions allow deposition of salts such as sodium sulfate that combine with moisture during shutdown. Volatile carryover is a function of drum pressure, while mechanical carryover can increase when operating with a high drum level or holes in the drum separators. Pitting due to the effects of sodium sulfate may occur in the reheater sections of conventional and HRSG units because the sulfate is less soluble and deposits on the internal surfaces. During shutdowns the moisture that forms then is more acidic.
In conventional units, pitting occurs in areas where condensate can form and remain as liquid during shutdown if the assemblies are not properly vented, drained, or flushed out with air or inert gas. These areas include horizontal economizer tubes and at the bottom of pendant bends or at low points in sagging horizontal tubes in steam touched tubes.
In HRSGs, damage occurs on surfaces of any component that is intentionally maintained wet during idle periods or is subject to either water retention due to incomplete draining or condensation during idle periods.
Attack from improper chemical cleaning activities is typically intensified at weld heat affected zones or where deposits may have survived the cleaning.
Pits often are small in size and may be filled with corrosion products or oxide, so that identification of the severity of pitting attack by visual examination can be difficult.
Damage to affected surfaces tends to be deep relative to pit width, such that the aspect ratio is a distinguishing feature.
The primary factor that promotes pitting in boiler tubing is related to poor shutdown practices that allow the formation and persistence of stagnant, oxygenated water with no protective environment. Confirming the presence of stagnant water includes:
- analysis of the corrosion products in and around the pit;
- tube sampling in affected areas to determine the presence of localized corrosion; and
- evaluation of shutdown procedures to verify that conditions promoting stagnant water exist.
Carryover of sodium sulfate and deposition in the reheater may result in the formation of acidic solutions during unprotected shutdown and can result in pitting attack. Similarly flyash may be pulled into reheater tubing under vacuum and form an acidic environment.
SIGN UP FOR OUR NEWSLETTER
*Join the conversation. Sign up to receive emails, events, and latest information!