The Power Plant Control Users Group conducts is sixth annual symposium at the Power Users Combined Conference, August 28 – 31, in the Omni Atlanta Hotel at CNN Center. The group, organized in 2018 to provide an open forum through in-person meetings and online seminars, disseminates information of value to owner/operators regarding the operation, maintenance, inspection, troubleshooting, and repair of control systems tasked with maximizing equipment performance and reliability.
While controls user groups serving the electric power industry typically focus on a given product—the Siemens T3000, for example—PPCUG presentations and discussions cover systems and equipment made by all OEMs and suppliers.
Technical program for the upcoming meeting was developed by an all-volunteer steering committee of industry engineers with deep controls experience identified in the sidebar and accompanying photo. An overview of the presentations scheduled for the week beginning August 28 follows.
PPCUG steering committee, 2023
Chair: David Martorana, operations program director, Tenaska
Vice Chair: Richard Chiafolo, consulting engineer, DominionBrian Hall, maintenance specialist, TECO Energy
Jason Justice, principal engineer, Southern Company
Eric Mui, controls engineer, Talen Energy
Peter So, director of project management and development, Calpine
Expectation is that most of the presentations will be made available to owner/operators through the Power Users website a few months from now—except for those by GE and Siemens-Energy. Access the GE PowerPoints at https://mydashboard.gepower.com; the Siemens-Energy presentations on the company’s Customer Extranet Portal, https://siemens.force.com/cep.
Slide decks from 2022 and earlier meetings already are accessible to registered users. If you are not registered, sign up now at www.powerusers.org: It’s easy and there’s no charge.
You can get a good idea of the fine work this organization performs by perusing the summaries of presentations made by both users and vendors last year. They follow the 2023 overview immediately below. You’re likely to find some best practices and lessons learned ripe for implementation at your plant.
Monday, August 28. The morning program begins with two presentations by Beamex: “Using Metrology Fundamentals in Calibration to Drive Long-Term Value” and “Optimal Testing Parameters for Process Instrument Calibration.”
GE takes the podium after the break, speaking to the following topics:
- Asset performance management.
- Dispatch optimizer.
- PII—getting the most out of your PI system.
The afternoon is dedicated to training, with ABB, GE, and Process Innovations leading the “beginner” program before the afternoon recess. For maximum benefit, participants are urged to bring their own devices and to connect to their systems.
The program for experienced attendees following the break focuses on GE’s Mark VIe turbine and plant control systems, including fundamentals of maintenance and troubleshooting, as well as on system architecture by ABB and Process Innovations.
Tuesday, August 29. ABB starts the day with “A Practical Approach to Alarm Management and Rationalization” and “Innovative Combined-Cycle Control Philosophy.” Following the morning break, PSM speaks to “Operational Intelligence—Augmenting Your Plant with Self-Learning Algorithms and AI-driven Analytic Capabilities,” and Black & Veatch to “Using Real-Time Data Analytics to Improve Asset Reliability and Performance Across a Combined-Cycle Fleet.”
GE has the afternoon program. Here are its talking points:
- GE and Nexus together: Moving forward (cyber, HMI, platform, lifecycle).
- Pre-start checks.
- Sliding-pressure control and auto governor testing.
- Technology refresher.
- Alarm rationalization.
- Advanced attemperator controls.
- Lessons learned from the field.
Tuesday’s technical program ends at 5 when the three-hour Vendor Fair begins.
Wednesday, August 30. Emerson presents first, on advanced system logic. HRST follows on duct-burner flame-detector controls. After the morning break, Siemens-Energy takes command of the podium until the afternoon recess. Lunch interrupts from noon to 1 p.m.
Here’s the Siemens-Energy lineup:
- Steam-turbine modernization options for combined-cycle plants.
- Live visualization of plant and equipment engineering.
The challenges of effective OT cyber monitoring. - Plant flexibility and integration with intermittent generating assets.
- Low-load operations.
- Operator training through web-based virtual plant simulators.
These presentations close out Day Three:
- I&C training and outage support, Endress+Hauser.
- Lessons learned of controls replacement with obsolete equipment, MD&A.
- Battery Energy Storage System black start.
Thursday, August 31, the final day of the conference, morning only, is planned for a series of user and vendor presentations—possibly as many as eight. But details were not available at press time. Follow program developments on the PPCUG pages of the Power Users website at www.powerusers.org. Alternatively, you can come up to date when you register for the conference.
With the 2023 Power Plant Controls Users Group (PPCUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website.
Migrate to EGD Mark VI-to-Ovation Interface
A representative from Emerson explains how to migrate from a “traditional” GSM-to-Ovation interface to an Ethernet Global Data (EGD) interface and the many advantages which can accrue to the user—including accessibility of Mark VI alarm and events, avoiding an OPC connection thereby increasing communication speed, availability of monitored points in all Ovation applications, and capability to run in parallel with Mark VI HMI. The direct interface sets the stage for remote start/operation, single-window control room, Mark VI HMI replacement, and advanced supervisory functions in Ovation.
“Direct EGD Interface with GE Mark VI and Mark VIe”
Full suite of control, M&D solutions
Katie Koch, PSM, made clear that PSM has solutions for optimizing your control and M&D systems, and they include assistance with 24/7 M&D, optimization algorithms (Autotune, FlexRamp, FlexStart, and FlexFuel), hardware and interface replacements and upgrades, fleet-level benchmarking, actionable intelligence for performance improvements, and even a full digital twin. Twelve engine platforms, eight combustion systems, and nine control systems make up the company’s experience base with these solutions.
Single HMI, control retrofits
MD&A’s Control Systems Division offers a variety of services for steam turbines, gas turbines, and generator exciters ranging from consulting and field engineering (including owner’s engineer) to replacement parts for legacy systems. Presenter Joe Hovorka dwelled at length on MD&A’s IBECS HMI which unifies and simplifies multiple legacy control system HMIs into one interface. IBECS is compatible with all major digital turbine controls, Hovorka noted. Seven case studies are presented, with attached one-page summaries of successful recent projects.
“Controls and Excitation Overview”
Automate generator gas-manifold purge
Mark Williams, Environment One Corp, stressed that automating the purging process can significantly reduce purge time required, consume less CO₂, and protect personnel in the event of an emergency. Slides review options for automating valves, tie-in points, example P&ID, and sample automation purge screen.
“Operator- Initiated Generator Purge/DHCP Upgrades”
Remedies for real-world controls issues
The range of issues detailed in this presentation from a seasoned controls expert working for a major fleet owner/operator almost defies current trends in user conference presentations. Each issue may not apply at your plant, but together they comprise almost a control engineer’s log of issues and remedies.
Included are turbine-oil leak-detection alarm, water ingress into GT exhaust and accumulation under the plenum from offline water wash, excessive gas flow at startup (TIL2319), enhancement of ECC correction algorithm for UCSB (TIL2290), auto NOₓ bias adjustment, liquid fuel system reliability, emergency bearing oil pump test prior to startup, steam injection bias, compressor bleed valve (CBV) flow issues, action of CBVs during startup, load commutated inverter (LCI) cross-connect, and isochronous control.
With the 2023 Steam Turbine Users Group (STUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website.
Cut L-0 blade damage repair costs in half
David Archambeault, EthosEnergy Group, told STUG attendees that they can cut costs of damaged L-0 ST/G blades by 40% to 50% using in-situ repair techniques rather than by replacing blades. The slides take you through repair case studies of the most common damage mechanisms—water-droplet erosion (Fig 6), foreign object damage, and cover or tenon cracking.
“In-situ Repair and Upgrade of L-0 Steam Turbine Blades”
Consider PAG fluids for EHC, lubrication
The theory of the case presented here is that polyalkalene glycol fluids (PAG) are superior to phosphate esters in electrohydraulic control (EHC) applications and to petroleum-based oil (mineral) for lubrication. Paul Jarvis, Oilkleen, explains that in EHC systems, PAG fluids exhibit hydrolytic stability, meaning they will not degrade when exposed to water contamination. In lube-oil systems, PAG fluids can eliminate varnish formation. Photos supplied of reservoirs after years of service with PAG are dramatically cleaner than with alternatives.
“Keys to a Successful Conversion”
Cycling damage illustrated—and remedied
A plethora of ST/G cycling damage/failure mechanisms and major structural repairs are discussed and illustrated in a set of slides from Brian Grant, Advanced Turbine Support. While most are focused on the L-0 stage, low-pressure section diaphragm nozzles and moisture drains and high-pressure packing gland seals also get attention (Fig 7). Closing words of advice: Do not rely only on info supplied by the OEM when planning repairs or assessing contingencies.
Integrated monitoring lowers EFOR, cost per kilowatt-hour
The potential benefits of a comprehensive asset management and equipment reliability program, anchored by an integrated monitoring platform, are clear in at least four cases involving large power companies (Fig 8). So says David Bramhall, Cutsforth, who led the audience through a description of the company’s InsightCM™ monitoring platform, with a focus on vibration and electromagnetic interference (EMI).
An eye-popping result at one plant: After putting together a list of equipment to inspect during an outage based on EMI readings, one plant added the isolated phase bus, not originally on the outage target list. Subsequently, 13 insulators were discovered to have moisture damage, which would likely have led to a forced outage in the near future.
“An Integrated Monitoring Platform Approach”
Poor maintenance, ops aggravate valve issues
Dennis Watson, Independent Turbine Consultants, had some pretty stark words and observations for the STUG audience. Valve maintenance is a basic aspect of ST/G upkeep but is being neglected, he said. Most plants in his experience are not properly matching temperatures during starts and stops, aggravating oxide buildup.
Most germane to his presentation, though, is that when valve vendors tell users that oxide cleaning is “extra” cost, they interpret that as “optional” even though “80% of valve-stem sticking problems are caused by high-temperature oxides and inadequate removal when “cleaned.” And grit blasting does not clean valve surfaces, it only polishes them. Check out the slides to learn how to do better—such as applying honing techniques with 50 and 80 grit Emery cloth for deeper cleaning of critical components (Fig 9) and try bar tests to check balance chamber concentricity to the valve-stem bushing.
With the 2023 Combined Cycle Users Group (CCUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website.
Perfect storm, but the lightning was arc flash
When someone lists operator error, equipment failure, instrument failure, hardware and software issues, and acts of God/nature as causes, you know the plant had a bad day. In fact, “perfect storm” doesn’t do justice to the human and equipment failures which preceded the potentially catastrophic arc-flash event on the 230-kV transmission line at an outdoor plant in the Northeast with no black-start capability.
Fortunately, no one was injured—just a 10-in. hole in the ground below the T-line (Fig 6)—and there was no collateral damage to the plant but the ensuing outage lasted more than half a day. But the industry should be collectively grateful that these are the kinds of good people who volunteer to present at CCUG to help others learn from their experiences.
An accident at the commercial warehouse facility next door caused the loss of the T-line when a worker on a manlift was attempting to change out some street lighting bulbs near the line. Operator and crew, who had just recently qualified in the powerplant control room, made some errors (not helped by unclear procedures) starting the emergency diesel/generator (EDG) and a three-minute sequence turned into 15. But the normal feed breaker had failed to open on loss of ac power, so the EDG couldn’t synch to the 480-V bus. The list goes on.
The recommendations following this event are a veritable safety minute expanded. Among the measures taken here:
- Install physical barrier 20 ft on either side of the T line with hazard signage.
- Revise procedures to include what to do if the normal power breaker does not open.
- Change EDG controller layout to eliminate sequence confusions.
- Remove light poles under the T-line.
“Plant Trips and Lessons Learned”
40 is the new 30—extending the life of your HRSG
The primary message delivered by Anand Gopa Kumar, HRST, is that the life of an HRSG can be extended to 30+ years, and even up to 40, with good O&M practices driven by data analysis. Kumar reviews HRST’s assessment process, then applies it in several case studies focused on (1) impacts from attemperator hunting as illustrated in Fig 7, (2) HP-evaporator feed pipe stress, (3) creep life assessment of an HP superheater, and (4) recurring and economizer failures. Findings are ranked based on priority and a criticality score of 1 to 100.
“HRSG Life Extension and Long-Term Planning: A Data Driven Approach”
Field testing, remote monitoring of critical pumps
Pump performance degrades over time as components wear and clearances erode. So you should periodically field-test your critical pumps at full-load conditions (Fig 8), advocates Jay Marchi, ProPump Services LLC, to optimize efficiency, identify issues, plan for maintenance, and keep availability high and costs at a minimum. New technologies are available for field testing and assessing pumps and drivers, and “they are only going to get better.” Users experiencing loss of expertise or budget pressures should also consider remote monitoring to “bring the experts to your rotating equipment.”
“Advantages of Periodic Field Testing of Critical Pumps”
Up your game in filters
By no means should users think that an E10 final filter is “the maximum filter class” for a gas turbine, says Florian Winkler, EMW filtertechnik GmbH. Winkler illustrates his message with extensive ISO 29461 test data comparing E10, E11, and E12 HEPA filters running on a W501F gas turbine for 5000 hours (Fig 9) for a range of parameters. “Better filtration always pays off,” he concludes.
“Better Filtration Pays for Itself – The Impact of (H)EPA GT Filters”
With the 2023 Generator Users Group (GUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website.
Fixators: What you should know about them
User group meetings are a great place to learn from the industry’s top talent in the owner/operator, vendor, and consultant communities. Information shared may include new regulatory initiatives and how they could impact plant operations, findings by colleagues that might affect your facility as well, case histories of importance, and backgrounders on equipment and components of significance that you might know little about.
At the 2022 GUG meeting, several backgrounders received high marks from attendees—including one on fixators (Fig 3), a continuously adjustable alignment wedge assembly for machine mounting. Important to recognize is that fixators are not shims, and the speaker presented a table comparing the two.
Suppliers of fixators claim they allow faster alignments than shims on new installations because you avoid the need for jacking up a machine, installing the shims, and then lowering the machine to check if it is level. If not, the process is repeated until the result is satisfactory.
Leveling and alignment by way of fixators is much simpler: For initial leveling, turn the adjustment screws a couple of turns and check. If not level, repeat. For alignment, identify the low points among the 16 or more fixators that might be installed on an F-class generator and raise to the degree necessary using the adjustment screws.
The presenter said his company had fixator issues on about 10% of its generators so equipped. Most often, vibration—sometimes attributed to a soft foot—was the underlying cause. Three case histories give the details.
Given fixator adjustments may be required over the life of your generator, experts recommend inspecting them at every turbine major, minor, and hot-gas-path inspection and cleaning and lubricating as required. Be prepared: Some fixators might have to be replaced.
“Fixators: Not as Fixed as You’d Expect”
Keeping flex links in top condition helps promote generator reliability
Flexible links provide an electrical connection between two rigidly mounted conductors, thereby allowing relative thermal growth/movement between them. Links may be of the laminated, wire-braid (Fig 4 left), and wire-rope type. Common locations include (1) between generator terminals and isolated-phase bus, (2) main leads and bushings, (3) connection rings and main leads, and (4) neutral bushings or Y point.
Common issues include the following:
- Mechanical failure attributed to (1) broken wires or laminations caused by fatigue or fretting, (2) incorrect installation, and (3) material creep/deformation.
- Overheating (Fig 4 right) caused by loose hardware, poor mating surfaces, and/or corrosion; poor ventilation; marginal connection or hardware design.
- Inattention to installation/maintenance best practices. It’s important to digest OEM bulletins, properly torque connection bolts, maintain a high level of cleanliness, follow OEM procedures to the letter, etc.
Causes of three flexible-link failures are described in detail in the slide deck. Plus, corrective and preventive actions are provided for each. This is “not difficult stuff.” It’s all about learning the correct way to install and maintain your equipment and staying committed to the task at hand.
Owner, OEM, industry colleagues, user group share info to resolve main-lead issue
Unplanned outages of a particular generator model traced to failures of main leads experienced by several owner/operators were a topic of discussion on the GUG and IGTC (International Generator Technical Community) forums early in 2021. Users were concerned because the failures occurred within months of the OEM performing NDEs that indicated the main leads were fine.
The OEM responded within a few months, recommending replacement of the main leads. The most likely cause, it said, was copper separation at the main-lead flange braze joint which could result in a generator ground fault and damage to surrounding components. The improved main-lead design offered has a more robust joint between the main-lead flange and the main-lead conduit.
The presenter said his company has eight of the 49 affected units and that no failures had occurred at any of its sites. An NDE inspection at one plant revealed no findings. The owner’s concern was the hefty hit on its budget if all of the susceptible main leads were replaced. Plus, there was a 45-week lead time associated with the OEM’s repair.
Have a look at the slide deck to see how the owner developed its own repair with help from industry colleagues to upgrade its main leads, saving time and money in the process.
“Main and Neutral Leads Mod for Modular Units”
What grounding-brush issues may be telling you
Shaft grounding can be accomplished by using a carbon brush, soft metal-bristled brush, or soft metal strap (often braided) to ride on the shaft surface and safely discharge voltages which can build up within the shaft train. The author explains where shaft voltages come from and what 
happens when a shaft grounding brush (SGB) malfunctions (it could cause a nuisance trip).
Next comes a series of slides that explain how you can identify a malfunction before it impacts operations—for example:
- High shaft voltage.
- No/low shaft brush current.
- Bearing and seal electrolysis. Fig 6 shows that this damage is “real,” possibly requiring repair or replacement. Vibration conducive to a forced outage also is a possibility.
- Magnetization of components.
- Artificial vibration. An orbital plot of this phenomenon is included.
Artificial rotor-winding ground indication. Point made: Online rotor-winding-to-ground resistance measurements may be influenced by induced voltage.
Users are advised to check brushes weekly for functionality or need for replacement. Responsible persons should be alerted if a significant SGB event occurs or recurring minor events are experienced. Also, check turbine and generator parts and rotors for residual magnetism; degauss down to 2 G or less, if possible.
With the 2023 Combined Cycle Users Group (CCUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website. See part one of the CCUG recap series here.
Get up to speed on vibration
Samuel Starnes, Reliability Testing Services Inc, kicked off the CCUG training session on the first morning of the meeting with a 117-slide tutorial on vibration analysis which included as sub-topics three units of measure (acceleration, displacement, velocity); location and mounting of probes (Fig 1) and sensor selection; data collection, quality, trending/alarming, analysis, and reporting; common machine faults; and case studies. If you prefer not to read a textbook on the subject, this will serve as a substitute. 
“CCUG Training Session: Basics of Vibration Analysis”
Online HRSG inspection links offline inspection, maintenance
Amy Sieben, I.A.F.D., advocates for combining external thermographic inspections of HRSG casing, penetrations, and doors (Fig 2), and internal “inspection” by monitoring control room parameters and basic HRSG design parameters—including pinch points, approach temperatures mass flows, pressures, and others.
Identifying where performance is off helps you prioritize where to place attention during the outage. By doing both external and internal inspections consistently, and combining with off-line inspections during the outage, you can also track drifting performance year to year and ensure better maintenance outcomes. At the heart of Sieben’s strategies are fundamentals of HRSG design and operation, for those less seasoned.
“Online Inspection—Tying Offline Inspection and Maintenance All Together”
Winterizing, cold weather prep
Recent cold weather grid-wide events in Texas and the Northeast have prompted renewed interest in, and regulation of, formal winterization programs and plans. This Texas owner/operator tracks and manages fleet-level winter readiness action items through its centralized power optimization center (POC), with each plant having specific checklists. The POC is considered “an edge” other owner/operators may not enjoy.
Although, in response to an audience question, the presenter said not much new M&D hardware was added (some “smart” heat-trace panels mostly) at the plants (Fig 3), though some of the M&D capability at the center was enhanced. There are now five stages of “alerts” generally based on ambient temperature forecasts. An Emergency Operations Center is located adjacent to the POC, where tabletop scenario exercises are conducted annually. “There are lots of winter PM work orders to comply with regulatory requirements,” the presenter said.
The editors consider this a must-view slide deck for all personnel at plants facing new NERC, FERC, ISO, and/or fleet level requirements, especially those sites with outdoor steam turbine/generator decks.
Repair versus replace: P91 non-return valves
Bill Kitterman, Bremco, and Will Medlock, SVI Industrial, take you on a virtual onsite and in-shop tour of a non-return P91 valve replacement, followed by an in-situ seat repair for the same type of valve. Seats are not replaceable but can be refurbished (Fig 4). Valve repair can be up to 90% less expensive than a full valve replacement. Keep in mind that a valve repair of P91 material does require regular post-weld repair inspections based on accepted methods of examination until end of life or when the component is replaced.
“Case Study on Repairing versus Replacing P91 Non-Return Valves”
New HRSG inspection tools available
Shawn Gowatski, TesTex, updated attendees on three new HRSG inspection tools developed with EPRI funding:
- Low Frequency Electromagnetic (EM) Technique (LFET) to inspect finned tubes typical of economizer and evaporator sections from the outside surface for pitting and generalized wall losses.
- The “Claw,” capable of inspecting the 360-deg circumference of tube-to-header welds in the first two rows of accessible superheater and reheater tubes using the Balanced Field EM Technique (BFET).
- HRSG Internal Access Tool (Fig 5) with a remote-controlled crawler used to insert an RFET (Remote Field Eddy Current) probe into headers 6.5 in. diameter and larger to inspect evaporator and economizer section tubes from the inside
Reams of testing and support data are available in the slides.
The 13th annual meeting of the Combined Cycle Users Group, launched in San Antonio in fall 2011, is a cornerstone of Power Users’ 2023 Combined Conference in the Omni Atlanta Hotel at CNN Center, August 28 – 31. Technical program for the upcoming meeting was developed by the all-volunteer steering committee of engineers and managers identified in the sidebar and accompanying photo—many with decades of relevant experience. A preview of the presentations scheduled for the week beginning August 28 follows.
CCUG steering committee, 2023
Chair: Brian Fretwell, director of mechanical services for engineering and major projects, Calpine
Vice chair: Robert Mash, plant manager, GE Power Services, River Road Generating PlantPhyllis Gassert, program director for operations excellence, Talen Energy
Steven Hilger, PE, plant manager, NAES Corp, Dogwood Energy Facility
Jason Jauregui, production team lead, CAMS, Woodbridge Energy Center
Aaron Kitzmiller, PE, plant engineer, Luminant, Fayette Power Plant
Jonathan Miller, maintenance manager, CLECO, Arcadia Power Station
Ben Stanley, VP operations, DGC Operations
Most sessions are user only. Non-users want to participate must be approved by the steering committee to gain admission. Presenting vendors are allowed in the room only when it is their time to present.
Expectation is that most of this year’s presentations will be made available to owner/operators through the Power Users website a few months from now. Slide decks from 2022 and earlier meetings already are accessible to registered users. If you are not registered, sign up now at www.powerusers.org: It’s easy and there’s no charge.
Monday, August 28. The CCUG technical program begins in earnest with a three-hour workshop (9 a.m. to noon) on “Mastering Desuperheating and Attemperation.” Ory Selzer of IMI Critical Engineering covers physics and design evaluation before moving on to application-specific challenges in HRSG, turbine bypass, and auxiliary systems.
The afternoon session includes a roundtable on lessons learned from LOTO events followed by presentations on film-forming amines, turndown or shutdown: combatting the effects of increased cycling, and hydrogen as a fuel for gas turbines.
Tuesday, August 29. Morning session starts with a roundtable on preparation for, and operation during, extreme hot weather and concludes with an EPRI presentation on process chemistry in combined-cycle plants. In between are user presentations on DCS replacement (Where do you start?) and high dewpoint in generator hydrogen, and vendor presos on the use of water-mist fire suppression systems to replace CO₂ and enhanced SCR and CO system management to meet today’s operational challenges.
The afternoon features the following:
- A roundtable on human and organizational performance.
- Supply-chain mitigation.
- HRSG roof liner and casing problems, why they occur, and repair options.
- Gas-turbine SCR in a changing world.
- Effects of cyclic operation on superheater link piping and manifolds.
Tuesday ends at 5 when the three-hour Vendor Fair begins.
Wednesday, August 30. The morning session opens with “Duct Burner Issues and Flame Monitoring” by HRST, followed by these presentations by Siemens-Energy personnel:
- Plant flexibility and integration with intermittent generating assets.
- Lessons learned on large forced outages.
- Asset management in an evolving market.
- Short-term layups.
Note that presentations by Siemens-Energy are not available through the Power Users website. Access them via the company’s Customer Extranet Portal at https://siemens.force.com/cep.
Amy Sieben of Industrial Air Flow Dynamics closes the morning program with “HRSG Drum Inspection.”
Wednesday afternoon is all GE Gas Power. The presentations are available only at https://mydashboard.gepower.com:
- Plant assessments for life extension.
- Transformer maintenance planning.
- Recent experience on water-chemistry challenges and FAC on in-service HRSGs.
- Benefits and methods of improving combined-cycle plant start time.
Thursday, August 31, the final day of the conference is morning-only. Two roundtables are on the program: Lack of skilled craft workers and how that can affect your maintenance outages, and Post-outage checklists—lessons learned. Remainder of the morning program will be filled by user presentations that had not been finalized at press time.
With the 2023 Steam Turbine Users Group (STUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website. See part one of the STUG recap series here.
Index of EPRI steam turbine resources
Eric Prescott, EPRI, followed his first presentation (immediately above) with an overview of EPRI’s resource locator (released April 2022) for ST/Gs, organized by equipment subsystems (Fig 1)—including steam path, high-temperature rotors and casings, low-temperature rotors and casings, secondary piping and valves, bearings and lube-oil systems, monitoring and control, and others. Resources for each subsystem are then categorized thusly:
- Operation, flexibility, and resilience.
- Maintenance.
- Component health and condition monitoring.
- Inspection
- Materials and repair.
“EPRI Steam Turbine Resource Navigator P219, Steam Turbine and Auxiliary Systems”
Users’ top concerns ‘entering no-man’s land’
The quandary many users feel about their ST/G assets was palpable during the opening roundtable discussion, perhaps best indicated by direct or near-direct quotes:
- We’re experiencing new failure mechanisms based on operating regime changes.
- “Bang for the [investment] buck on combined cycles is really low.”
- We have a 21-year-old ST/G with 40,000+ hours that’s never been opened.
- We’ve entered “into a no-man’s land on some of this stuff—we have no data points in our fleet.”
- “I’m worried about ‘Sanford & Son’ engineering being applied to these assets online.”
- “Old timers’ knowledge is no longer available.”
- “How can we ‘feel better’ about operating these assets?”
- Money for the sunset assets is being deferred, even though their end-of-life dates are being pushed farther out.
Other interests expressed included how best to laser-scan reheat stop valves in preparation for an outage, managing salt-induced damage at outside installations near the ocean, and learning of any experience with a particular vendor’s combined HP-IP turbine section. A few users were concerned with future issues like how the need for process steam in carbon-capture systems will change ST/G operating conditions and potentially require new components.
Turning gear, motor reliability may need a fresh look
The almost incalculable value of a great user’s conference presentation is learning about a forced outage or safety event that happened at someone else’s plant and making sure it doesn’t happen at yours. In that category is surely one from the Steam Turbine Users Group (STUG) on turning-gear reliability. The utility presenter was a steam-turbine expert with decades of experience.
There were two important threads woven together in this presentation: (1) A description of a catastrophic failure of a TG motor (Fig 2) at one of his utility’s plants, and (2) the larger implications for maintenance, sparing, and even the impact on the industry as a whole.
Regarding the second, the presenter noted that the TG (Fig 3) could be a “pinch point” for ST/G reliability in plants that are, or will be, starting and stopping much more frequently to follow renewables. It’s easy to forget, he added, that the TG probably was designed to operate perhaps 10 times a year, but under future operating scenarios that could increase to 500 or more (multiple starts per day).
The utility in question has many 40- to 55-year-old ST/Gs from a variety of OEMs. Unfortunately, all four of the utility’s steam-turbine experts, each with 40+ years of experience, left under an early-out program. Now the utility is planning to have 16 GW of solar and 5 GW of wind over the coming years. These are conditions familiar to many utilities. But the catastrophic failure of a TG motor caused by imbalance set off alarm bells, especially since a spare motor was not available and the unit was out for an extended period.
In spring 2019, plant personnel noticed pieces of steel from the TG bull gear in the oil sump (Fig 4 left), and deformation of the gear teeth (Fig 4 right). The root cause was determined to be an attempted engagement of the TG by the control system during full-speed operation resulting from the failure of a solid-state relay.
With this event as a backdrop, the presenter then turned to a tutorial of sorts on the function of the TG, basic nomenclature, different types of gearing and motors, motor interlocks, the importance of the air or hydraulic supply in the lock out/tag out (LOTO) boundary, proper tools for rigging a bull gear, and other topics.
Some of the recommendations for adjusting TG maintenance and sparing include:
- Have a spare motor, ideally one that could serve several different ST/Gs; spare bull (ring) and pinion (clash) gear; chain (if your unit has one); and several solenoids, even a complete assembly.
- Install a black-start unit with permanent reaction arm.
- Identify proper tools and their location so they can be available quickly in the event of an unexpected outage.
- Discuss issues with operations and visually inspect at least once a year prior to an outage.
- Measure and set correct backlash during outage.
- Inspect the lubrication system during outages or more frequently.
- Pull the TG out during major outages for a complete test.
- Have a battery pack to turn the rotor as backup.
To dive deeper into keeping your TG reliable, the presenter suggests obtaining a copy of EPRI Report No. 1019645, “Turbine Generator Auxiliary Systems, Volume 6: Turning Gear Maintenance Guide,” published in 2010.
“Turning Gear Maintenance and Failure”
Inspect LP crossover bellows at every opportunity
If you have aging ST/Gs from this particular OEM (check out the slides to find out), be aware that several units with over 100,000 operating hours have experienced significant recent failures of the LP crossover bellows. Two presenters from two different utilities teamed up to describe failures and remedies at three units in their respective fleets (not all are combined cycles). One presenter advised the audience to “inspect these components at every opportunity.”
When the staff at one plant pulled the cover and insulation off of an “indoor unit with a generous turbine deck,” he described what was found: “It was ugly.” At another plant, an unexpected steam leak was heard, although the unit operated for an additional nine days. Cause was determined to be metal fatigue caused by repeated expansion and contraction and steam-pressure stress (Fig 5); no operational data anomalies were identified around the period of the event.
At one plant, the replacement component was upgraded to 2-ply Inconel 625. At another, the 2-ply 16-gage Type 316 stainless steel was upgraded to 2-ply 16-gage Inconel; a third unit ended up with 18-gage Inconel because of supply-chain issues.
These are not the only failures of this component worldwide the OEM has experienced.
“Crossover Bellows—Two Failure Modes”
User roundtable discussion
A variety of experiences were reported during the roundtable following the Day One presentations. One user reported having a bellows in the condenser gland seal piping “fall into the bottom of the condenser only two years after it was replaced.”
Apparently, several to many users are experiencing issues with turning gears. Advice passed around the room: Watch amps on the motor; check bearing temperatures – bearing metal temperatures “can be deceiving”; check eccentricity; and pay attention to vibration. One user reported a bowed-rotor event resulting from a TG issue.
Another audience member asked if anyone was experiencing issues with the glands to the exhaust hood of a side-exhaust ST/G.
With the 2023 Generator Users Group (GUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website. See part one of this GUG recap series here.
Stator-bar failures traced to insulation voids
A member of the GUG steering committee spoke about his company’s experience regarding premature failures of stator windings attributed to manufacturing issues. Of particular concern was that some failures occurred even after all electrical tests had been passed. Resulting lost production obviously had a negative impact on the bottom line.
Most of the failed bars had voids in their insulation (Fig 1)—typically in the transition/bend area. Speaker reviews the types of tape available and the pros and cons of using each, plus proper taping procedures, electrical testing, etc. Rewind issues at two of the utility’s plants contribute to the learning experience.
“Stator Winding Manufacturing Issues”
Learn from experience gained by colleagues
A major utility’s four-person generator brain trust shares its findings on the topics below—nuggets for virtually every owner/operator.
- Stator rewind lessons learned: winding support-cone findings (misaligned phase-lead banks), step found between new and existing iron after restack (Fig 2), bottom coils damaged during installation, modified wedges to prevent partial blockage of core vents, FME event.
- Partial rewind resulted in a full rewind: OEM used third-party winders. Their lack of experience and familiarity with winding design contributed to extensive growth in project scope, plus work quality issues. Bar and tie damage were a result.
- Use of improper materials: Capping compound used for series connections was of an older formulation than used today, with lower thermal transfer properties. This resulted in specialized online monitoring post rewind and potential derate of the machine. The fix requires installation of a new inner nozzle shield to increase cooling.
- Bar manufacturing issues, in particular a lack of consistency in the shape of replacement bars which caused tolerance, alignment, and bar-to-bar spacing issues.
- Non-seg bus phase-to-phase fault.
- Generator terminal and PT-cabinet water intrusion.
Why proper alignment is critical to rewind success
Speaker provides a valuable backgrounder on the importance of correct alignment of stator-endwinding support system components during a rewind and follows with a case history of what went wrong on the rewind of a 7A6 generator when new connection rings were not properly supported during installation. Key elements of the presentation include the following:
- A review of the stator winding support system, including core iron/frame and slot components (filter materials and slot wedging system). Plus, endwinding support components.
- A review of the purpose of the support system, including: mechanical support the stator winding, allow for thermal expansion/contraction, and minimize/restrain dynamic forces during normal operation and fault events.
- Imperative that the endwinding support system is correctly aligned prior to winding installation. Challenges such as the complex 3-D shapes of stator bars/coils are covered. Points to remember: The installed position must accommodate thermal expansion without binding, provide adequate spacing to prevent the risk of voltage stress, and assure a uniform and symmetric endwinding assembly to withstand operational forces and fault events.
“Importance of Correct Alignment of Stator Endwinding Support System Components During Rewind”
With the 2023 Power Plant Controls Users Group (PPCUG) approaching August 28-31 in Atlanta, part of the greater Power Users Combined Conference, reviewing some of the content from last year’s meeting should encourage you to attend or send someone from your organization to experience this valuable content in person. Presentation abstracts below are based on information available only to end users in the slide decks posted at www.powerusers.org. Those seeking deeper dives into specific topics should note the presentation titles in italics at the end of each summary and access the source material on the website. See part one of this recap series here.
Differentiate alarm audio tones
Most plants with digital control systems suffer from alarm overload in the control room and have applied better methodologies to reduce the number of alarms, prioritize them, and reduce the burden on operators without sacrificing their attention to the ones that matter. A unique feature of the alarm methodology described here, by a large-fleet user, is applying unique audio tones to indicate alarm priority.
Two real-world examples are included: A generator-field ground-detector test from the human machine interface (HMI) and turbine lube-oil leak detection.
“Alarm Management: Generator FGD Testing, Leak Detection”
OEM versus non-OEM: Get R.E.A.L.
“OEM and non-OEM suppliers are battling these days for the customer, and in some cases are practically giving away the hardware.” So states John Downing from TC&E, a division of AP4 Group, in reviewing the merits of choosing one over the other, mostly illustrated through a series of questions posed to the audience. Four areas—reliability, efficiency, affordability, and longevity (R.E.A.L.)—are explored.
Plan for supply-chain disruptions
During a suite of vendor presentations, two OEMs addressed supply-chain challenges. One said a major chip supplier announced “allocations” around the primary CPU in the family of controllers used in the Mark VIe. The other OEM rep said lead times have been extended by 50% to 100% since 2019, but also implied that the worst was over.
“Our procurement systems were not really that sophisticated,” one presenter admitted, addressing internal supply-chain issues. “We had too many single-source suppliers, poor visibility into sub-sub-suppliers, and no end-to-end forecasting.” This apparently has been rectified, in part through multi-vendor sourcing agreements and digital surveillance capability over sub-suppliers. The only recourse for users has been to postpone obsolescence-related replacements, collaborate more tightly on advance planning for upgrades, and expect and be prepared for controller failures.
OEM presentations are not posted on the Power Users website. To access Siemens-Energy slide decks, write galen.george@siemens-energy.com. For GE, log into your MyDashboard account on the GE website.
Partner with a controls specialist
John Emery, Nexus Controls (currently part of GE Vernova), urged users to consider a partnering arrangement with a controls specialist firm for “fully integrated controls and cybersecurity solutions.” World-class training services, preventive maintenance, remote diagnostics, and even remote service are available, along with in-kind and upgraded components, and advanced software.
Supply-chain struggles to continue through 2023
Carrying on the prevalent theme from controls OEMs, Jaime Butler, Nexus Controls (currently part of GE Vernova) included a few valuable slides which help explain the supply-chain disruptions most users are experiencing for chips and other electronic components. The global pandemic was only one of the drivers.
Unfortunately, the conclusion is that, while inventory for unconstrained components will continue to build, products dependent on field programmable gateway arrays (FPGA), power management integrated circuits (PMIC), and microcontroller units (MCU) will continue to struggle. Butler suggests several proactive solutions to mitigate risk.
