News & View, Volume 45 | Proving Performance What Distinguishes an ISO-Compliant Product Certification Agency?

News & Views, Volume 45 | Proving Performance – What Distinguishes an ISO-Compliant Product Certification Agency?

By:  Andy Coughlin

News & View, Volume 45 | Proving Performance What Distinguishes an ISO-Compliant Product Certification Agency?Whether it’s fair-trade coffee, sustain-ably harvested lumber, energy efficient appliances, or other certified products, consumers and companies look for products that have high standards of origin, production, and performance.  Structural Integrity Associates’ TRU Compliance mark is no different.  Our mark shows buyers a product has undergone rigorous assessment for seismic, wind, and blast performance to nationally recognized standards.   

However, not all agencies conform to the internationally recognized set of standards that govern a product certification agency, allowing it to be impartial, objective, and accountable to the public.  The standard ISO/IEC 17065 Conformity assessment — Requirements for bodies certifying products, processes and services spells out requirements that make agencies like TRU Compliance accountable to its clients and to the public.  The requirements in TRU Compliance’s Certification Manual are broad, but they generally fall into the three categories below.

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News & View, Volume 45 | The Importance of HRSG HP Evaporator Tube Internal Deposit Evaluation

News & Views, Volume 45 | The Importance of HRSG HP Evaporator Tube Internal Deposit Evaluation

By:  Barry Dooley

News & View, Volume 45 | The Importance of HRSG HP Evaporator Tube Internal Deposit EvaluationEvaluation of High Pressure (HP) Evaporator Tube Deposits is important for several reasons:

  • Determining if flow-accelerated corrosion (FAC) might be occurring in the lower pressure circuits.
  • Regular evaluations can provide information on the internal deposit deposition rate, which is information necessary to help prevent under-deposit corrosion damage mechanisms.
  • Provides information necessary to develop an optimized cycle chemistry for HRSGs.
  • Can help determine if the HRSG needs to be chemically cleaned.

The leading heat recovery steam generator (HRSG) tube failure mechanisms are FAC, thermal and corrosion fatigue, and under-deposit corrosion (UDC) and pitting. The corrosion products released by the FAC mechanism are transported from the affected area (typically the feedwater or lower pressure systems) and can eventually reach the HP evaporator tubing, so understanding the deposition in the HP evaporator is an important step in determining if FAC might be occurring. Deposition on the inside of HP evaporator tubing is also a precursor to any of the under-deposit corrosion HRSG tube failure mechanisms.

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Structural Integrity’s Critical Infrastructure Group Mentoring Students from the University of California, San Diego

Structural Integrity’s Critical Infrastructure Group Mentoring Students from the University of California, San Diego

Structural Integrity’s Critical Infrastructure Group Mentoring Students from the University of California, San DiegoStructural Integrity  is mentoring students from the University of California, San Diego during their senior design Capstone project. The goal of the mentorship is to give the students real-life working experience through participation in a design project with industry mentors. The students are learning how to develop forces on equipment during earthquakes and how to design anchorage so that the equipment remains in place and functional during and following an earthquake. At the end of the project, the students will write a report and make a presentation to their Professor, their classmates and other industry mentors.

News & View, Volume 44 | Failed Grade 91 “Soft” Pipe Bend - A Case Study Failure Occurred With Less Than 35,000 Operating Hours

News & Views, Volume 44 | Failed Grade 91 “Soft” Pipe Bend – A Case Study – Failure Occurred With Less Than 35,000 Operating Hours

By:  Kane Riggenbach and Tony Studer

News & View, Volume 44 | Failed Grade 91 “Soft” Pipe Bend - A Case Study Failure Occurred With Less Than 35,000 Operating HoursGrade 91 steel is widely used in tubes, headers and piping of superheaters and reheaters because of its higher strength at elevated temperature compared to low alloy steels such as Grade 22.  The improved strength is a result of a tempered martensitic microstructure with a fine distribution of carbonitride precipitates.  This microstructure is achieved through careful heat treatment: normalizing, tempering, and subsequent forming and post weld heat treatments.  If these heat treatments are not performed properly, then the strength of the material essentially reverts to that of a low alloy steel like Grade 22, and is usually accompanied by a reduction in hardness, leaving the Grade 91 material in a so-called “soft” condition.

This article summarizes a case study for Grade 91 material in the “soft” condition, which was responsible for a steam leak after only 5 years of operation, illustrating how this material condition can result in forced shutdowns and safety hazards.  It is because of these consequences that it is recommended to have a Grade 91 life management program to understand if your plant may have such vulnerability.

This case study provides general background to the steam leak and describes the subsequent metallurgical evaluations performed to verify that mal-heat treatment of the Grade 91 steel was the root cause of the leak.  A follow-on article (the next issue, Volume 45, of News and Views) will provide additional insight into local stresses and analytical prediction of such failures, as well as highlighting key aspects of a Grade 91 life management program.  Suffice it to say if this plant had implemented such a program, the vulnerability of the affected spool would have been identified and mitigating actions could have been taken to avoid the leak.

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News & View, Volume 44 | Weld Overlay Repair Mitigates Thermal Fatigue Flaw Growth

News & Views, Volume 44 | Weld Overlay Repair Mitigates Thermal Fatigue Flaw Growth

By:  David Segletes

A circumferential flaw in a 14-inch diameter News & View, Volume 44 | Weld Overlay Repair Mitigates Thermal Fatigue Flaw Growth suction pipe-to-elbow stainless steel weld was identified in both units of a nuclear power plant as depicted in Figure 1.  The two units are Westinghouse designed four-loop pressurized water reactor (PWR) plants and are mirror images of each other.  The pipe-to-elbow weld is the first junction remote from the hot leg piping.  The circumferential flaw at this location was first discovered on Unit 2 during the spring of 2016 and subsequently on Unit 1 in the spring of 2017.  The flaws are located at comparable circumferential positions, given the two pipes are mirror images of each other and at the same distance from the RHR nozzle.  Structural Integrity (SI) performed the flaw evaluation for each unit at the time of discovery.  The flaws are ID connected and located at the weld heat affected zone (HAZ) on the pipe side.  Although stress corrosion cracking has not be observed in the HAZ of austenitic stainless steel in PWR systems, the flaws were evaluated for both fatigue crack growth and stress corrosion crack growth.  The flaw evaluations indicated there was life remaining for a short period of operation, with the appropriate safety margin, but not sufficient to allow the client to operate the plant until the end of the operating license for the given unit.  Subsequently, a repair plan was developed to allow the units to operate to the end of the operating license.

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News & View, Volume 44 | Data Driven Solutions for the Most Difficult Problems

News & Views, Volume 44 | Data Driven Solutions for the Most Difficult Problems

By:  Andrew Crompton and Mark Jaeger

News & View, Volume 44 | Data Driven Solutions for the Most Difficult ProblemsIn recent years, SI has observed an increasing trend in the use of specialty instrumentation to solve “impossible” problems or answer “indecipherable” questions.  This shift was particularly apparent within commercial nuclear, where data-driven solutions have long been perceived as challenging due to short outage windows, personnel dose concerns, and a significant paperwork burden, among other factors.  Widespread adoption of instrumentation-based solutions creates new paths to tackling difficult/persistent problems, and shifts the industry focus for critical assets from reactionary to more of a predictive approach.  In 2017, SI assisted numerous clients with deployment of specialty instrumentation in this fashion, comprising two general scenarios: 1) new designs/modifications, and 2) repeat failures.  Each application requires different sensors and varying analytical methods, but the approach used to leverage the resultant data to solve the problem is generically applicable throughout the energy sector.  The text below details important considerations for both scenarios and highlights a successful application of the underlying process for management of thermal fatigue in reactor coolant system branch piping.

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News & View, Volume 44 | Update on Proposed Safety of Gas Transmission and Gathering Pipeline Regulation

News & Views, Volume 44 | Update on Proposed Safety of Gas Transmission and Gathering Pipeline Regulation

By:  Scott Riccardella, Erica Fisette, and Bruce Paskett

News & View, Volume 44 | Update on Proposed Safety of Gas Transmission and Gathering Pipeline RegulationStructural Integrity (SI) has significant depth and expertise in current pipeline safety regulations and dedicates substantial resources to ensure a comprehensive understanding of proposed pipeline safety regulations.  Using the most current insights relative to upcoming regulations, Structural Integrity guides our clients with strategic direction to best position their pipeline safety programs to comply with the new regulations.  Structural Integrity takes a proactive role in attending key Pipeline and Hazardous Materials Safety Administration (PHMSA) meetings such as the Gas Pipeline Advisory Committee (GPAC) meetings as well as supporting the rulemaking efforts of the American Gas Association (AGA), Interstate Natural Gas Association of America (INGAA), Pipeline Research Council International (PRCI) and other key associations.

The GPAC is a statutorily mandated Committee that advises PHMSA on proposed gas pipeline safety standards and regulations.  The Committee consist of members from Federal and State governments (PHMSA and National Association of Pipeline Safety Representatives or NAPSR), the regulated industry, and the general public. The Committee is responsible for reviewing the technical feasibility, reasonableness, cost-effectiveness, and practicability of proposed standards and regulations relative to pipeline safety.  The goal of the Committee is to provide recommended revisions and/or actions in response to standards and/or regulations proposed by the Federal Department of Transportation (DOT)/ PHMSA.

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News & View, Volume 44 | A First-of-a-Kind NDE Innovation from SI The first PDI qualified manually-encoded DM Weld Procedure

News & Views, Volume 44 | A First-of-a-Kind NDE Innovation from SI – The first PDI qualified manually-encoded DM weld procedure

By:  Jason Van Velsor, Joe Agnew, and Owen Malinowski

News & View, Volume 44 | A First-of-a-Kind NDE Innovation from SI The first PDI qualified manually-encoded DM Weld ProcedureDetermining a course of action once in-service damage is discovered often requires applying a multi-disciplinary approach that utilizes Nondestructive Examination (NDE), analytical techniques such as stress analysis, and metallurgical lab examination.  Such was the case recently for a combined cycle plant where indications were found through NDE on the inlet sides of two identical main steam stop/control valves but were not seen on the outlet side.  In this case, Structural Integrity (SI) did not perform the field NDE but was requested to perform analytical and metallurgical assessments of the welds.  The welds in question joined the 1Cr-1Mo-1/2V (SA-356 Grade 9) main stop/control valve body castings to Grade 91 piping, so the welds represent a ferritic-to-ferritic dissimilar metal weld (DMW).  See the Dissimilar Metal Welds in Grade 91 Steel, (page 15) for further information. The welds were made using a 1Cr-1/2Mo (AWS type B2) filler metal, which matches the chromium content of the valve body, but is significantly undermatching in strength to both the valve body material and the Grade 91 piping. 

The course of action taken was to perform local stress analysis and remaining life estimates for the downstream (outlet) connections of the valves to assess likelihood of future damage and establish an appropriate re-inspection interval.  Detailed metallurgical analysis was also performed on a ring (entire circumference) section removed from one of the upstream welds (which exhibited both surface and volumetric indications in the weld metal) in order to provide insight into the damage mechanism and inform the stress analysis and remaining life estimates.

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News & View, Volume 44 | Example Grade 91 High Energy Piping DMW Joint Stress and Metallurgical Analysis

News & Views, Volume 44 | Example Grade 91 High Energy Piping DMW Joint Stress and Metallurgical Analysis

By:  Ben Ruchte

News & View, Volume 44 | Example Grade 91 High Energy Piping DMW Joint Stress and Metallurgical AnalysisDetermining a course of action once in-service damage is discovered often requires applying a multi-disciplinary approach that utilizes Nondestructive Examination (NDE), analytical techniques such as stress analysis, and metallurgical lab examination.  Such was the case recently for a combined cycle plant where indications were found through NDE on the inlet sides of two identical main steam stop/control valves but were not seen on the outlet side.  In this case, Structural Integrity (SI) did not perform the field NDE but was requested to perform analytical and metallurgical assessments of the welds.  The welds in question joined the 1Cr-1Mo-1/2V (SA-356 Grade 9) main stop/control valve body castings to Grade 91 piping, so the welds represent a ferritic-to-ferritic dissimilar metal weld (DMW).  See the Dissimilar Metal Welds in Grade 91 Steel, (page 15) for further information. The welds were made using a 1Cr-1/2Mo (AWS type B2) filler metal, which matches the chromium content of the valve body, but is significantly undermatching in strength to both the valve body material and the Grade 91 piping. 

The course of action taken was to perform local stress analysis and remaining life estimates for the downstream (outlet) connections of the valves to assess likelihood of future damage and establish an appropriate re-inspection interval.  Detailed metallurgical analysis was also performed on a ring (entire circumference) section removed from one of the upstream welds (which exhibited both surface and volumetric indications in the weld metal) in order to provide insight into the damage mechanism and inform the stress analysis and remaining life estimates.

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News & View, Volume 44 | Planned and Emergent Outage Support Structural Integrity is on Your Team

News & Views, Volume 44 | Planned and Emergent Outage Support – Structural Integrity is on Your Team

By:  Terry Herrmann

News & View, Volume 44 | Planned and Emergent Outage Support Structural Integrity is on Your TeamWhile the 2018 Spring outage season is mostly behind us, we all know a key element in being able to provide safe, reliable, clean and economic power to energy consumers is how successfully plant outages are accomplished.   I know from personal experience how good planning, including contingency planning, has significantly reduced outage durations (see Figure 1).  I worked my first outage in 1981.  It ran 110 days and was punctuated by rework, surprise discoveries and last-minute procurement of materials and services.  By the late 1990s the industry had established outage milestones for design changes, significantly improved the level of detail in schedules, performed more work with the plant on line and implemented focused outage control organizations.  Except for major activities like condenser retubing, power uprates and emergent issues that impact the scheduled critical path, outage durations today are almost exclusively associated with refueling activities.

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