News & Views, Volume 49 | Inspection Optimization- Probabilistic Fracture Mechanics

News & Views, Volume 49 | Inspection Optimization: Probabilistic Fracture Mechanics

By:  Scott Chesworth (SI) and Bob Grizzi (EPRI)

News & Views, Volume 49 | Inspection Optimization- Probabilistic Fracture Mechanics

The goal was to determine whether the frequency of current inspection requirements was justified or could be optimized (i.e., increase the interval of certain inspections to devote more attention to higher-value inspections and thereby maximize overall plant safety).

Executive Summary

Welds and similar components in nuclear power plants are subjected to periodic examination under ASME Code, Section XI.  Typically, examinations are performed during every ten-year inspection interval using volumetric examination techniques, or a combination of volumetric and surface examination techniques.  Nuclear plants worldwide have performed numerous such inspections over plant history with few service induced flaws identified.

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News & Views, Volume 49 | Materials Lab Featured Damage Mechanism - Soot Blower Erosion

News & Views, Volume 49 | Materials Lab Featured Damage Mechanism: Soot Blower Erosion

News & Views, Volume 49 | Materials Lab Featured Damage Mechanism - Soot Blower ErosionBy:  Wendy Weiss

Soot blower erosion (SBE) is caused by mechanical removal of tube material due to the impingement on the tube wall of particles entrained in the “wet” blower steam. As the erosion becomes more severe, the tube wall thickness is reduced and eventually internal pressure causes the tube rupture.

Mechanism

SBE is due to the loss of tube material caused by the impingement of ash particles entrained in the blowing steam on the tube OD surface.  In addition to the direct loss of material by the mechanical erosion, SBE also removes the protective fireside oxide. (Where the erosion only affects the protective oxide layer on the fireside surface, the damage is more properly characterized as erosion-corrosion.) Due to the parabolic nature of the oxidation process, the fireside oxidation rate of the freshly exposed metal is increased. The rate of damage caused by the steam is related to the velocity and physical properties of the ash, the velocity of the particles and the approach or impact angle. While the damage sustained by the tube is a function of its resistance to erosion, its composition, and its operating temperature, the properties of the impinging particles are more influential in determining the rate of wall loss.

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News & Views, Volume 49 | Rapid Assessment of Boiler Tubes Using Guided Wave Testing

News & Views, Volume 49 | Rapid Assessment of Boiler Tubes Using Guided Wave Testing

News & Views, Volume 49 | Rapid Assessment of Boiler Tubes Using Guided Wave TestingBy:  Jason Ven Velsor, Roger Royer, and Ben Ruchte

Tubing in conventional boilers and heat-recovery steam generators (HRSGs) can be subject to various damage mechanisms.  Under-deposit corrosion (UDC) mechanisms have wreaked havoc on conventional units for the past 40-50 years and have similarly worked their way into the more prevalent combined cycle facilities that employ HRSGs.  Water chemistry, various operational transients, extended outage periods, etc. all play a detrimental role with regards to damage development (UDC, flow-accelerated corrosion, pitting, etc.).

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News & View, Volume 49 | Piping Fabricated Branch Connections

News & Views, Volume 49 | Piping Fabricated Branch Connections

By:  Ben Ruchte

Fabricated branch connections represent a common industry issue in combined cycle plants. Many are vulnerable to early damage development and have experienced failures.  Despite these challenges, a well-engineered approach exists to ensure that the baseline condition is fully documented and a life management plan is put in place to help reduce the overall risk to personnel and to help improve plant reliability.

Fabricated branch connections between large bore pipes (including headers and manifolds) are often fabricated with a reinforced branch commonly in the form of a “catalogue” (standard size) fitting, such as an ‘o-let’. These are more prevalent in today’s combined cycle environment as compared to conventional units that used forged blocks or nozzles rather than welded-on, integrally reinforced pipe fittings. The fittings are typically thicker than the pipes in which they are installed to provide compensating reinforcement for the piping run penetration. Full reinforcement is often not achieved as the current Code requirements place all of the reinforcement on the branch side of the weld joint.  As a result,  higher sustained stresses are generated and, particularly in the case of creep strength enhanced ferritic (CSEF) steels, early formation creep cracking in the weld heat-affected zone (HAZ) can occur (known as Type IV damage – see Figure 1). The well documented challenges of incorrect heat treatment of the o-let weld can also add to the likelihood of damage in CSEF components.  Damage is therefore most likely to occur in fabricated branches that operate with temperatures in the creep range.

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News & Views, Volume 49 | Attemperator Monitoring with Wireless Sensors - Risk and Cost Reduction in Real Time

News & Views, Volume 49 | Attemperator Monitoring with Wireless Sensors: Risk and Cost Reduction in Real Time

News & Views, Volume 49 | Attemperator Monitoring with Wireless Sensors - Risk and Cost Reduction in Real TimeBy: Jason Van Velsor, Matt Freeman and Ben Ruchte

Installed sensors and continuous online monitoring are revolutionizing how power plants manage assets and risk by facilitating the transformation to condition-based maintenance routines. With access to near real-time data, condition assessments, and operating trends, operators have the opportunity to safely and intelligently reduce operations and maintenance costs and outage durations, maximize component lifecycles and uptime, and improve overall operating efficiency.

But not all data is created equal and determining what to monitor, where to monitor, selecting appropriate sensors, and determining data frequency are all critical decisions that impact data value. Furthermore, sensor procurement, installation services, data historian/storage, and data analysis are often provided by separate entities, which can lead to implementation challenges and disruptions to efficient data flow.

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News & Views, Volume 49 | Hydroelectric Penstock Inspection - Field NDE Services

News & Views, Volume 49 | Hydroelectric Penstock Inspection: Field NDE Services

News & Views, Volume 49 | Hydroelectric Penstock Inspection - Field NDE ServicesBy:  Jason Van Velsor and Jeff Milligan

Our talented experts, using the latest technology and methods, deliver unmatched value, actionable information, and engineering knowledge for the management of your most critical assets.

Many of the penstocks used in the hydroelectric power industry have been in service for over 50 years.  Often with older components, historical documents like, as-built drawings and proof of material composition no longer exist.  This information is critical for inspection, repair and replacement decisions.  SI has the expertise to assist hydro clients with everything from material verification, inspection, and fitness-for-service analysis to keep penstock assets in-service for many more years to come.

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News & Views, Volume 49 | Mission Critica-nApplications to Support the Mega-Rule

News & Views, Volume 49 | Mission Critical Applications to Support the Mega-Rule

News & Views, Volume 49 | Mission Critica-nApplications to Support the Mega-RuleBy:  Scott Riccardella, Bruce Paskett, and Steven Biles

On October 1, 2019, the Pipeline and Hazardous Materials Safety Administration (PHMSA) published amendments to 49 CFR Parts 191 and 192 in the Federal Register, issuing Part 1 of the Gas Transmission Mega-Rule.  This new regulation is commonly referred to as the Mega-Rule since it represents the most significant regulatory impact on gas transmission pipelines since the original Gas Transmission Integrity Management Program (TIMP) Regulation was issued in 2003

The original Notice of Proposed Rulemaking (NPRM) issued in April, 2016 was split into 3 Parts, with the first Part (Mega-Rule 1) including specific requirements to address congressional mandates in the 2012 Pipeline Safety Reauthorization, and other pipeline safety improvements, including:

  • Maximum Allowable Operating Pressure (MAOP) Reconfirmation (§192.624),
  • Material Verification (MV) (§192.607),
  • Engineering Critical Assessments for MAOP Reconfirmation (§192.632),
  • Analysis of Predicted Failure Pressure (§192.712),
  • Assessments Outside of High Consequence Areas (HCAs) (§192.710),
  • Additional Requirements to Evaluate Cyclic Fatigue (§192.917(e)(2)), and
  • Additional Analysis of Electric Resistance Welded (ERW) Seam Welds (§192.917(e)(4))

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News & Views, Volume 49 - PEGASUS- Advanced Tool for Assessing Pellet-Cladding Interaction

News & Views, Volume 49 | PEGASUS: Advanced Tool for Assessing Pellet-Cladding Interaction

By:  Bill Lyon, PE and Michael Kennard

News & Views, Volume 49 - PEGASUS- Advanced Tool for Assessing Pellet-Cladding Interaction

PEGASUS provides a fully capable computational environment to solve the unique, detailed 3D analyses required for the evaluation of PCI.

In the current economic environment in which nuclear units compete with less costly energy sources, a quicker return to full power correlates to more power generated and increased operating efficiency.  This may be achieved with shorter startup post-refueling or a quicker return-to-power following any number of plant evolutions including load follow, control blade repositioning, equipment outage or maintenance, testing, extended low power operation, scram, etc.  Such strategies to increase operating efficiency may enhance the risk of pellet-cladding interaction (PCI), a failure mechanism that occurs under conditions of high local cladding stress in conjunction with the presence of aggressive chemical fission product species present at the cladding inner surface.  These conditions can occur during rapid and extensive local power changes and can be further enhanced by the presence of fuel pellet defects (e.g., missing pellet surface, MPS).  Several commercial reactor fuel failure events in the last eight years, as recently as early 2019, suggest a PCI-type failure cause.  To safely manage changes in core operation, the margin to conditions leading to PCI-type failures must be determined prior to implementation of such operating changes.

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News & Views, Volume 49 | Digital Elevation Modeling Support Pressure Tests Records and Reduce MAOP Reconfirmation Costs

News & Views, Volume 49 | Digital Elevation Modeling: Support Pressure Tests Records and Reduce MAOP Reconfirmation Costs

By:  Scott Riccardella, Bruce Paskett, and Eric Elder

§ 192.624(a)(1) of the Mega-Rule 1 requires MAOP Reconfirmation for steel transmission pipe segments if records necessary to establish the MAOP in accordance with § 192.619(a)(2) (e.g. pressure test), including records required by § 192.517(a), are not traceable, verifiable, and complete and the pipeline is located in a high consequence area (HCA) or a Class 3 or Class 4 location.

Part 192, Section 192.517(a) requires that natural gas pipeline operators shall make and retain, for the useful life of the pipeline, a record of the following information for any Subpart J Pressure Test (PT):

  1. The operator’s name, the name of the operator’s employee responsible for making the test, and the name of any test company used,
  2. Test medium used,
  3. Test pressur,
  4. Test duration,Pressure recording charts, or other record of pressure readings.
  5. Elevation variations, whenever significant for the particular test, and
  6. Leaks and failures noted and their disposition.

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News & Views, Volume 49 | Code Compliance and the Modular Construction Trend

News & Views, Volume 49 | Code Compliance and the Modular Construction Trend: What Manufacturers Need to Know to Comply with Building Codes

By:  Andy Coughlin, PE, SE

News & Views, Volume 49 | Code Compliance and the Modular Construction Trend

The modular construction industry is projected to grow globally at an annual rate of 6.9%, outpacing the growth of traditional construction.1  Modular construction has many advantages over traditional building methods, including improved quality control and shorter project durations. Factory-built systems are constructed in controlled environments with equipment and materials that are not feasible at congested job sites, and project schedules can be shortened when factory work and field work are performed in parallel.

However, modular projects may stumble without proper forethought: when fabrication takes place in a factory away from the jobsite, the building officials, inspectors, and engineers can have less oversight and less recourse to implement changes if issues are discovered in the field.  Code compliance may also be an issue when systems are designed by factory engineers rather than the engineer of record.  To mitigate these potential pitfalls, careful planning is required at the start of the project.

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