News & Views, Volume 52 | Understanding the Effects of Hydrogen Blending on Pipeline Integrity

/in , , , , , , , /by

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.  

Figure 1. FCG rate curves in hydrogen (solid lines) versus air (dashed lines).

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. 

 

Figure 2. Fracture toughness reduction as a function of hydrogen partial pressure for different pipe grades.

HYDROGEN EMBRITTLEMENT
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.

Figure 3. Improvement in POR and PORR for different integrity assessments.

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.

Get News & Views, Volume 52

Contact Us

News & Views, Volume 52 | PEGASUS: Development for TRISO Fuel and Advanced Reactor Applications

/in , , , /by

DEVELOPMENT FOR TRISO FUEL AND ADVANCED REACTOR APPLICATIONS

By:  Bill Lyon

The Pegasus code allows the user to develop more realistic models of fuel behavior by utilizing an innovative 3D framework that delivers a more detailed and rigorous solution. This solution allows the user to remove conservative assumptions, simplifications, and uncertainties resulting from 2D or 1D simplified/empirical solutions. 

Figure 1. A PEGASUS TRISO fuel particle model and mesh showing geometry and composition

Remove the conservativism and start using the calculated operational margins to increase efficiencies and reduce the capital outlay for refueling.

QUICK FACTS

  • Independently developed 3D FEM code; fuel vendor independent code provides best-estimate performance modeling
  • Focused on fuel structure
  • Provides high-fidelity results
  • Addresses existing fuel performance
  • Aids in the development of advanced fuel designs
  • Ready for Gen IV Reactors and TRISO Fuels

BENEFITS REALIZED

  • Reduced conservatism
  • Increased efficiencies
  • Potential for significant fuel cost savings

INTRODUCTION
The PEGASUS nuclear fuel behavior code is a robust 3D, finite element modeling (FEM) computational software platform capable of thermo-mechanical and structural non-linear analyses of nuclear fuel and reactor components. Focused initially on light water reactor (LWR) fuels and materials, PEGASUS is being adapted and applied to a broader range of emerging industry priorities for proposed Gen IV (Generation IV) advanced reactor designs such as high-temperature gas (HTGRs) and molten salt-cooled reactors (MSRs). These applications require modeling various fuel forms, geometries, and materials such as high assay, low enrichment uranium (HALEU), advanced cladding alloys, and other fuels with integrated containment such as tri-structural isotropic (TRISO) fuel particles and encapsulated particle fuel types. PEGASUS is perfectly positioned to evaluate these challenging structures with realistic modeling and simulation results.

TRISO-BASED FUELS AND MATERIALS DEVELOPMENT
One of the significant efforts underway in the continued development of PEGASUS is the introduction of material constitutive and behavioral models for TRISO fuel and the materials that comprise this fuel form. The initial research on the needed material property and behavior model data comes from a variety of sources, including the Department of Energy’s (DOE’s) Advanced Gas Reactor (AGR) fuel development and qualification experimental program [1] and numerous DOE-supported modeling efforts such as those from Hales et al. [2,3]. In parallel to those efforts, geometric modeling and meshing techniques specifically designed to address the complex TRISO fuel geometric configurations are being explored and developed. These exploit the CAD-like modeling environment and the already available automated meshing tools and capabilities in PEGASUS.

TRISO fuel forms are comprised of multi-layered particles embedded into fuel compacts of various compositions and shapes. The TRISO particle layers are designed to encapsulate and contain the nuclear fuel and the fission products produced during operation. It is this characteristic that creates the robust nature of TRISO-based fuels. The fuel particles are typically composed of a fuel kernel, such as uranium oxycarbide (UCO), surrounded by layers of 1) a porous carbon buffer, 2) an inner pyrolytic carbon (PyC) shell, 3) a silicon carbide (SiC) layer, and 4) an outer PyC shell. The orientation and relative thicknesses of these layers are shown in Figure 1, which depicts a basic PEGASUS TRISO particle model.

Material constitutive models have been developed for UCO fuel, porous and pyrolytic carbon, and SiC and are currently being tested for application in PEGASUS.

TRISO FUEL CONFIGURATIONS AND MODELING DEVELOPMENT
In addition to conventional FEM-based modeling and meshing capabilities, PEGASUS also contains several tools explicitly designed to facilitate advanced reactor and fuel analysis. These include: 1) a 3D and hybrid 2D/3D meshing capability to optimize computational efficiency (currently under development), 2) a “spherical mesh object” tool to generate 3D/2D spheres and embedded spheres for modeling TRISO and fully encapsulated TRISO fuel forms, and 3) a “spiral extrusion” tool which can generate complex, spiral 3D fuel geometries and meshes such as those required for helical multi-lobed advanced fuel designs.

The spherical mesh object and spiral extrusion tools are unique to PEGASUS and, to our knowledge, not found in any other fuel performance or general-purpose FEM code. 

Figure 2. Example TRISO particle distribution: (a) micrograph of a TRISO fuel compact (adapted from Nelson [5]), (b) random particle distribution pattern algorithm output.

Figure 3. Cross-sectional view of embedded TRISO particles in a 3D fuel compact matrix.

These modeling capabilities allow PEGASUS to be used to investigate very detailed mechanical and structural effects in highly complex fuel forms. For example, the mechanical interaction between TRISO fuel layers, including the effects of cracking, debonding, and asphericity, can be modeled explicitly. Future work is planned to integrate damage-mechanics modeling capability into PEGASUS that is specifically applicable to TRISO-based fuels.

Given the complexity of typical TRISO fuel forms, another critical aspect for analysis is the development of a consistent methodology for generating configurations that mimic the distribution of TRISO particles in a fuel matrix. A technique has been developed based on a “passive randomization method” originated by Sukharev [4] that yields distribution patterns approximating those of TRISO fuels observed during fuel examinations. An example of an early application of this technique is shown in Figure 2, which compares a fuel micrograph to a generated TRISO particle configuration pattern.

For application in PEGASUS, geometric configurations such as shown in Figure 2b are converted into 2D and 3D FEM meshes with TRISO kernels embedded in meshed substrates using automated tools. Models such as these can provide the bases for computational studies of TRISO fuel performance, from detailed kernel multilayer response to interactions between multiple kernels and their surrounding matrix. Several examples of TRISO meshes generated with PEGASUS are shown in Figures 3, 4, and 5. Figure 3 illustrates the cross-section of a 3D TRISO fuel compact with embedded TRISO particles. The appearance of multiple particle sizes is an indication of varying particle depths within the matrix. This figure was generated using the spherical object meshing tool in PEGASUS.

Figure 4. Cross section of an array of discrete 3D TRISO particles embedded into a graphite compact pellet.

A more complex 3D model of encapsulated TRISO particles is shown in Figure 4.  This model features a sparse particle distribution generated using the randomization technique applied in Figure 2b coupled with 3D automated meshing capabilities. This model was meshed in PEGASUS using an automated scripting tool and tested early in the development project using simplified approximations of thermal and mechanical properties of the kernel and matrix materials. Boundary conditions simulating prototypic gas reactor conditions were used in the simulation. Figure 5 shows the plotted temperature distribution from a portion of the model in figure 4.

Figure 5. Temperature distribution in a cross-section of a 3D slab of a TRISO compact matrix model under prototypic gas-cooled reactor conditions.

Further development of the TRISO fuel modeling capabilities in PEGASUS is ongoing. Detailed 3D modeling of TRISO kernels with irregular geometries such as non-uniform thicknesses and shapes in the pyrolytic carbon and SiC layers has been identified as a high priority as we advance. Additional priorities for future development include 1) implementation of mechanistically based, deterministic TRISO kernel and fuel compact failure models integrated into the material constitutive relations and 2) the calculation and tracking of fission product species diffusion and concentrations which incorporate the effects of chemical interactions, kernel layer, and substrate cracking.

SUMMARY
The PEGASUS nuclear fuel behavior code is an advanced, independently developed 3D FEM computational software program capable of conducting complex, coupled thermo-mechanical and structural non-linear analyses. The role of PEGASUS is envisioned as complementary to existing regulatory-based assessment and licensing tools, where there is a need to address conservatism, perform an independent assessment, or provide additional fidelity to laboratory-sponsored research where wider materials, phenomena, or fidelity is needed. Current development activity is focused on application to proposed GEN IV advanced reactor designs featuring unique fuel materials and design configurations such as TRISO-based ceramic fuels to be deployed in HTRGs and MSRs. Future development work on PEGASUS will continue along multiple avenues, emphasizing TRISO constitutive and deterministic failure model development, implementation, and modeling. In summary, PEGASUS provides high fidelity and independent advanced analysis capability that can be used to address existing fuel performance. It allows for less conservatism and accelerates the development, design, and regulatory processes for new fuel concepts and advanced fuel designs such as those employing TRISO-based fuels.

References

  1. D. A. PETTI, G. BELL, and the AGR Team, “The DOE Advanced Gas Reactor (AGR) Fuel Development and Qualification Program,” INEEL/CON-04-02416, 2005 International Congress on Advances in Nuclear Power Plants, May 15-19, 2005.
  2. J. D. HALES et al., “Multidimensional Multiphysics simulation of TRISO particle fuel,” J. Nucl. Mat. 443 (2013) 531-543.
  3.  J. D. HALES et al. “BISON TRISO Modeling Advancements and Validation to AGR-21 Data,” INL/EXT-20-59368, September 2020.
  4.  A. G. SUKHAREV, Optimal strategies of the search for an extremum, U.S.S.R. Computational Mathematics and Mathematical Physics, 11(4), 1971.
  5. A. T. NELSON, Features that Further Performance Limits of Nuclear Fuel Fabrication: Opportunities for Additive Manufacturing of Nuclear Fuels, ORNL/SPR-2019/1183, May 2019.

Get News & Views, Volume 52

Contact Us

SI Appoints New Leadership

/in , /by
Read more

News & Views, Volume 52 | Online Monitoring of HRSG with SIIQ™

/in , , , , , , , , , /by

Figure 1. Typical components that are monitored with the pertinent damage mechanisms in mind.

A CASE STUDY ON IMPLEMENTATION AT A 3X1 COMBINED CYCLE FACILITY (ARTICLE 1 OF 3) 

By:  Kane Riggenbach 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).  

Figure 2. Example dashboard of the health status and ‘action’ date for a variety of components.

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.

Figure 4. Examples of damage observed by SI on attemperators.

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.

Figure 5. Examples of creep damage observed by SI on header link pipe connections (olets).

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. 

Figure 6. Examples of creep/fatigue damage observed by SI at tube-to-header connections.

Figure 7. Examples of online monitoring alerts generated from SIIQ

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.

Get News & Views, Volume 52

Contact Us

News & Views, Volume 52 | An SIIQ™ Primer

/in , , , /by

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.

Figure 1. Typical architecture for connection to data historian.

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 above 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.

Get News & Views, Volume 52

Contact Us

Structural Integrity Associates and C2C Technical Services Announce the Formation of SI Solutions in Partnership with Jumana Capital

/in , /by

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”.

 

Media Contact
Chris Sydor
Manager of Marketing and Communications
Structural Integrity Associates, Inc
info@structint.com
704-977-1361

High Energy Piping (HEP) Seminar 2023

/in , , /by

January 31ST – February 2ND 2023

COURSE DESCRIPTION

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
  • Metallurgists
  • Engineering and Maintenance Managers
  • Anyone interested in gaining knowledge of high energy piping systems is welcome

INSTRUCTORS

  • Ben Ruchte – Director, Senior Metallurgist
  • Kane Riggenbach – Senior Consultant, Analytical Services
  • Steve Gressler – Technical Director/Account Executive

COURSE TOPICS

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
  • PlantTrack™
  • Online monitoring damage tracking

EVENT DETAIL

Event Date
Tuesday, January 31st – Thursday, February 2nd

Duration
8:00am to 5:00pm Tues. and Wed. 8:00am to 12:00pm on Thurs.

Individual Price
$1,195

Location
Lone Star Court
10901 Domain Drive Austin, Texas 78758
Telephone: 512-814-2625

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

Structural Integrity Associates | News and Views, Volume 51 | Optical Microscopy | Applications and Benefits

News & Views, Volume 51 | Optical Microscopy Applications and Benefits

/in , , , /by

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.

Figure 1. Two- and three-dimensional color images of an aluminum annode plate showing light-colored deposits that have caused uneven wastage. The 3D image shows the extent of material removal in locations where deposits are not present. Normal wastage in this application should be uniform.

Figure 2. Two- and three-dimensional color images showing fastener thread flank damage and a crack origin near the root of the upper thread. The 3D image shows that the crack origin is located on the thread flank rather than at the deepest part of the thread root.

Figure 3. Two- and three-dimensional images of a copper heat exchanger tube that has been damaged from under-deposit corrosion (UDC). The image at left shows the typical appearance of the ID deposits. The center image shows a region of damage surrounding a pinhole leak. The 3D image provides an idea of the depth of internal corrosion in the tube.

Figure 4. Two- and three-dimensional images of a region of damage on an internal surface of a feedwater pump. The image at left shows the appearance of brownish deposits found within the corroded region of the pump surface. The 3D image provides an indication of the depth and shape of the corrosion damaged region.

Figure 5. Two dimensional stitched image of a weld cross section showing cracking emanating from a shallow weld root. Porosity is also visible in multiple locations in the weld.

Figure 6. Images of a region of damage on the exterior of a heat exchanger tube where wastage has occurred near the tube sheet. The upper right image is a view of the leak location with an overlay of lines showing the position where the surface profile was documented as well as the depth profile (overlaid and in the lower image). The upper left image, which has an appearance similar to an x-ray, is a side view of the 3D image of the tube surface.

Get News & Views, Volume 51

Contact Us

News & Views, Volume 51 | Drone Inspections

/in , , , , /by

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.

Figure 1. Drone image of a dent on an elevated section of 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. 

Figure 2. Google Earth view of image locations

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.

Get News & Views, Volume 51

Contact Us
Structural Integrity Associates | News and Views, Volume 51 | Pitting Corrosion in Conventional Fossil Boilers and Combined Cycle:HRSGs

News & Views, Volume 51 | Materials Lab Featured Damage Mechanism

/in , , , , /by

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. 

Figure 1. Severe pitting in a tube from a package boiler

Mechanism 

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. 

Figure 2. Pitting on the ID surface of a waterwall tube

Typical Locations

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. 

Features

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. 

Root Causes

Figure 3. Pitting on the ID surface of an economizer tube

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: 

  1. analysis of the corrosion products in and around the pit; 
  2. tube sampling in affected areas to determine the presence of localized corrosion; and 
  3. 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.

Get News & Views, Volume 51

Contact Us