fossil power Archives

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

April 20, 2021/in Combined Cycle, Fossil Power, Heat Recovery Steam Generator (HRSG), Materials Laboratory, News and Views, Wendy Weiss /by Structural Integrity

By: 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.

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

April 20, 2021/in Ben Ruchte, Jason Van Velsor, News and Views, Non-Destructive Evaluation, Roger Royer /by Structural Integrity

By: 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.).

News & Views, Volume 49 | Piping Fabricated Branch Connections

April 20, 2021/in Ben Ruchte, Combined Cycle, Fossil Power, Heat Recovery Steam Generator (HRSG), Materials Lab, News and Views /by Structural Integrity

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.

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

April 20, 2021/in Ben Ruchte, Combined Cycle, Fossil Power, Heat Recovery Steam Generator (HRSG), Jason Van Velsor, Matt Freeman, Monitoring, News and Views /by Structural Integrity

By: 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.

Structural Integrity Associates Announces the Appointment of Steve Gressler as Vice President, Fossil

April 23, 2020/in Company News, Fossil Power /by Structural Integrity

Structural Integrity Associates, Inc. (SI), a leader in engineering and technology in the power and oil & gas industries, today announced the appointment of Steve Gressler as Vice President of its Fossil business. Gressler will report to Mark Marano, SI President and Chief Executive Officer.

Mr. Gressler is a metallurgical engineer with over 30 years of experience in metallurgy, failure analysis, and the damage assessment of fossil power generation equipment and distributed heating and cooling systems with an emphasis on piping, boilers, headers, and balance of plant equipment. He is a principal contributor to engineering life cycle programs and procedures, risk assessments, analysis tools, and technologies to assess service degradation in low alloy and creep-strength enhanced ferritic steels. His current work focuses on the development, integration, and deployment of nondestructive testing and damage tracking technology in addition to engineering consulting and materials assessments.

Since joining Structural Integrity Associates in 1997, Steve has been a principal contributor to the methodologies applied for life assessment of high temperature and critical piping components. This includes characterization of creep and fatigue damage in longitudinal seam welds, girth welds, and header ligaments. It also extends to the engineering of data management systems used for aiding decision-making processes.

Marano noted, “Steve brings metallurgical leadership and technology development experience to the SI leadership team and is an integral part of our new customer focused strategy. Steve’s knowledge of the fossil business, tenure with SI, and relationships with our clients will accelerate our journey to create value for power and oil industry customers as a highly valued engineering and technology partner.”

Gressler received a Bachelor of Science in Metallurgical Engineering from the University of Pittsburgh and is a Registered Professional Engineer. Steve is also a prior recipient of the SI Riccardella Innovation Award for Prioritization Method for Fossil Plant Piping.

News & View, Volume 47 | Surface Preparation – A Pivotal Step in the Inspection Process

March 3, 2020/in Ben Ruchte, Clark McDonald, Combined Cycle, Fossil Power, Heat Recovery Steam Generator (HRSG), Materials Lab, Materials Laboratory, News and Views, Non-Destructive Evaluation, Steve Gressler /by Structural Integrity

By: Ben Ruchte, Steve Gressler, and Clark McDonald

Properly inspecting plant piping and components for service damage is an integral part of proper asset management. High energy systems constructed in accordance with ASME codes require appropriate inspections that are based on established industry practices, such as implementation of complimentary and non-destructive examination (NDE) methods that are best suited for detecting the types of damage expected within the system. In any instance where NDE is used to target service damage, it is desirable to perform high quality inspections while at the same time optimizing inspection efficiency in light of the need to return the unit to service. This concept is universally applicable to high energy piping, tubing, headers, valves, turbines, and various other power and industrial systems and components.

News & Views, Volume 47 | Metallurgical Lab Case Study: Corrosion Fatigue in WaterWall Tubes Increasingly A Safety Concern as Coal Plants Cycle

March 3, 2020/in Ben Ruchte, Fossil Power, Materials Lab, Materials Laboratory, News and Views /by Structural Integrity

By: Ben Ruchte

It is well known that conventional coal-fired utility boilers are cycling more today than they ever have. As these units have shifted to more of an ‘on-call’ demand they experience many more cycles (start-ups and shutdowns, and/or significant load swings) making other damage mechanisms such as fatigue or other related mechanisms a concern.

The most recent short-term energy outlook provided by the U.S. Energy Information Administration (EIA) indicates the share of electricity generation from coal will average 25% in 2019 and 23% in 2020, down from 27% in 2018. While the industry shifts towards new construction of flexible operating units, some of the safety issues that have been prevalent in the past are fading from memory. The inherent risks of aging seam-welded failures and waterwall tube cold-side corrosion fatigue failures are a case in point. It is well known that conventional coal-fired utility boilers are cycling more today than they ever have. As these units have shifted to more of an ‘on-call’ demand they experience many more cycles (start-ups and shutdowns, and/or significant load swings) making other damage mechanisms such as fatigue or other related mechanisms a concern. The following case study highlights this point by investigating a cold-side waterwall failure that experienced Corrosion Fatigue. While this failure did not lead to any injuries, it must be stressed that the potential for injuries is significant if the failure occurs on the cold-side of the tubes (towards the furnace wall).

News & Views, Volume 47 | Materials Lab Featured Damage Mechanism: SH/RH Fireside Corrosion in Conventional Coal Fired Boilers

March 3, 2020/in Fossil Power, Materials Lab, News and Views, Wendy Weiss /by Structural Integrity

By: Wendy Weiss

Superheater/reheater fireside corrosion is also known as coal ash corrosion in coal fired units.

MECHANISM
Coal ash corrosion generally occurs as the result of the formation of low melting point, liquid phase, alkali-iron trisulfates. During coal combustion, minerals in the coal are exposed to high temperatures, causing release of volatile alkali compounds and sulfur oxides. Coal-ash corrosion occurs when flyash deposits on metal surfaces in the temperature range of 1025 to 1200oF. With time, the volatile alkali compounds and sulfur compounds condense on the flyash and react with it to form complex alkali sulfates such as K₃Fe(SO₄)₃ and Na₃Fe(SO₄)₃ at the metal/deposit interface, which are low melting point compounds. The molten slag fluxes the protective iron oxide covering the tube, exposing the metal beneath to accelerated oxidation.

News & Views, Volume 46 | Metallurgical Lab Featured Damage Mechanism: Waterwall Fireside Corrosion (WFSC) in Conventional Boilers

July 1, 2019/in Fossil Power, Materials Laboratory, News and Views, Wendy Weiss /by Structural Integrity

By: Wendy Weiss

Industry experience shows that waterwall tubing in conventional boilers can be susceptible to fireside corrosion, depending on fuel type, firing practice, etc. In boilers where fireside corrosion has been identified as a maintenance issue, wastage rates of 5 to 25 mils/year are not uncommon. Since the mid 1990s, the installation of low NOx burner systems designed to lower NOx emissions has significantly increased the wastage rates in some boilers. Operators of subcritical boilers have reported wastage rates as high as 30 mils/year, while those operating supercritical boilers have reported rates exceeding 100 mils/year in the worst cases. These higher damage rates have resulted in an increase in tube failures, and operators have struggled to accurately define the extent of the damage and install the appropriate mitigating technologies.

News & Views, Volume 46 | Plant Integrity Assistant – There’s an App for That!

July 1, 2019/in Fossil Power, Matt Freeman, News and Views, PlantTrack /by Structural Integrity

By: Matt Freeman

PlantTrack App now available

Plant engineers must often answer ‘what damage is this piece of equipment susceptible to, and what can we do about it?’ or ‘how much longer can this component continue operating’? A free app is now available in both the Google Play store and the Apple App store to help answer these and other equipment integrity questions (see figure 1).

The PlantTrack App is a plant integrity assistant that provides life calculators, damage mechanism guides, technical articles, lab sample submittal form, and other functions relevant for plant engineers. While it is geared towards fossil (both coal and gas) power plants, it has applicability for equipment at other plants as well. For subscribers to the PlantTrack web application, the mobile app also provides a dashboard view of inspection history, action items, damage tracking results, etc. Users of the PlantTrack software will recognize some of the features from the ‘PlantTrack Tools’ that have previously been available through a web browser.

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