Onsite - Combined Cycle Journal

Participate in the Generator Expert Skill Register

By Team-CCJ | July 29, 2022 | 0 Comments

Clyde Maughan has spearheaded several generator-themed industry initiatives in his 70-plus years (yes, 70+) of unselfish service to power producers, most recently the Generator Expert Skill Register.

Finding a well-qualified generator expert for a specific assignment sometimes can challenge plant management, particularly so during these unsettling times of pandemics, global supply-chain issues, and shortages of just about everything.

Given the ongoing tsunami of personnel changes at generating companies, OEMs, and specialty service companies, many in yesterday’s pool of generator experts may well have moved on. How do you find the person you need?

Maughan came up with the Skill Register idea—perhaps best described as a “yellow pages” directory online—while snowed in at his Schenectady (NY) home a couple of years ago. He partnered with CCJ General Manager Scott Schwieger launch the Register, now hosted at https://www.ccj-online.com/generator-expert-skill-register.

They invite every engineer with deep generator experience to register and provide the requested background information and skill description summary. This allows the generator owner’s staff to review the posted material at https://www.ccj-online.com/generator-experts and communicate directly with those who seem to best fit the requirements for the task at hand.

This is a win-win: Qualified engineers often do not know who needs their services and the generator owner/operator rarely has a current list of problem-solvers.


Spring migration, collector changeout, flex-link systems

By Team-CCJ | July 29, 2022 | 0 Comments

James Joyce, operations manager, MD&A’s Generator Repairs Div, speaking at the 2022 conference of the 7F Users Group, May 23-27, in the Fairmont Dallas Hotel, focused on three topics of particular importance to owner/operators of 7FH2 generators: Spring migration, collector changeout, and flex-link systems.

All styles of 7FH2s—Gens One, Two, and Three, plus 324s—are affected by amortisseur spring axial movement under the body wedges of the generator rotor (addressed in TIL-2106), which can cause blockage of cooling-air passages. If a whole row moves, Joyce added, it can halt cooling to all the rows. MD&A has a patented corrective repair, described as the insertion of a “top hat” which locks all the slots together so they can’t move, that can be done “with relative ease.”


Joyce then moved on to a case study of an onsite repair of a collector ring completely destroyed (without affecting field windings) by flashover induced by carbon buildup. The old, deformed rings were removed, and replaced with new ones fabricated in the shop, keeping the bore copper sleeve intact. Users should visually inspect brushes for carbon buildup and remove it if found, then change the polarity.

TIL-2106 also recommends visual inspection for cracking in flex-link connections (photos) during an outage. There’s no standard borescope inspection technique for this, especially the bolt threads. MD&A (and others) stock pre-2014 and post-2014 (following an OEM mod) “universal-sized” flex links with “standard stainless-steel bolting.” Really old units may have to mitigate asbestos in the conforming putty. Electrical testing should be performed pre- and post-replacement, and users are encouraged to “change polarity, swapping wire leads, once every minor outage.

Joyce’s presentation is available to registered owner/operators in the 7FUG Conference Archives section of the Power Users website at www.powerusers.org.

Correcting stator-core looseness in generators for gas and steam turbines

By Team-CCJ | July 29, 2022 | 0 Comments

Jamie Clark of AGT Services kicked off the vendor presentations at the 2022 conference of the 7F Users Group, May 23-27, at the Fairmont Dallas Hotel, by addressing stator-core looseness in generators for gas- and steam turbines. Perhaps to jolt the audience awake after breakfast, Clark noted that there’s a “huge uptick” in stator-related problems” and later in his remarks quantified and expanded on his assertion: Generator emergent work during outages is up 30% in the industry for hydrogen-cooled units.

The litany of issues Clark addressed should make users quake in their boots until you realize that “the 7F generator fleet is 20-25 years old on average and the life of a stator is 20-25 years by design.” One big common phenomenon: The whole core gets longer after thousands of cycles, he explained; as you might suspect, peaking and load-following units are most affected.

Most of the looseness is compression-based, not related to vibration or thermal conditions, and “the problems are at the turbine end, not the collector end.”

Owner/operators of the MHI-built 7FH2s (about 50 worldwide) perhaps should be quaking in their boots. These units are “losing teeth and failing,” Clark said, adding that MHI issues “can be catastrophic” and full stator rewinds are required. TIL-2260, addressing these issues with MHI units, was revised in February 2021 to include root-cause analysis findings.

Clark reported data on post TIL-2260 repairs for six MHI turbine ends (TE) and TE coolers that the AGT Services shop was involved with, and found two TEs were missing no iron, one was previously missing iron, and three with AGT repairs had no prior adverse reports or issues. Three of the TE coolers showed 100% looseness at the core outer diameter, for the full length of the core, and presence of iron oxide at the inside and outside diameters. These units required belly-band tightening, stator re-wedging, and full-core re-torquing to 3000 ft-lb.


All GE 7FH2s will show signs of turbine-end iron looseness, Clark stated, and Model 324 units coupled to steam turbines are showing signs of outside space block (OSSB) migration (photo). OSSB can cause a unit to “go to ground, experience a phase fault, and melt iron and copper.”

Why the OSSB issues? Clark explained it with three factors: (1) Axially loose core, predominantly on the turbine end, (2) poor bonding of OSSBs to the core compression flange, and (3) after startups, the core expands radially and axially, tearing the “relatively thin OSSB dovetail out at the keybar. On cool down, the core-compression flange retracts but leaves the OSSB where it was. This repeats every operating cycle. Eventually, the OSSB cuts through the bottom filler and into the bottom bar groundwall insulation, resulting in a stator ground.

Viewing the photos Clark provides in his slides, along with additional material on repair strategies and causes of damage, will enhance your understanding of these issues. His presentation is available to registered owner/operators in the 7FUG Conference Archives section of the Power Users website at www.powerusers.org.

2022 BEST PRACTICES AWARDS: Six plants earn Best of the Best honors in CCJ’s annual Best Practices program

By Team-CCJ | July 1, 2022 | 0 Comments

The COMBINED CYCLE Journal and the steering committees of the industry’s leading gas-turbine users groups—including 7F, 501F, 501G, 7EA, 7/9HA, Western Turbine, Frame 6B, 501G, 501D5-D5A, AOG, and V—collaborate to expand the sharing of best practices and lessons learned among owner/operators of large frame and aeroderivative gas turbines.

Thirty-five plants listed below participated in the 2022 Best Practices Awards program with eight selected by industry experts for Best of the Best honors. Details of the Best Practices submitted will be published in future issues.

CCJ launched the industry-wide Best Practices Awards program in late 2004. Its primary objective, says General Manager Scott Schwieger, is recognition of the valuable contributions made by plant and central-office personnel to improve the safety and performance of generating facilities powered by gas turbines.

Industry focus today on safety, outage management, and performance improvement—including starting reliability, fast starting, thermal performance, emissions reduction, and forced-outage reduction—is reflected in the lineup of proven solutions submitted this year.

2022 Best of the Best GT-based Plants

CPV Towantic Energy Center

Owned by Competitive Power Ventures
Operated by NAES Corp

  • Significant implementation of insurance recommendations reduces facility risk and annual cost of insurance premium increases
  • Cost-effective solutions to achieve SPCC certification, minimize spill risk and increase site safety
  • Custom weather protection for collector house assembly eliminates nuisance trips and moisture damage
  • Remaining ZLD without the initial infrastructure

C.T. Genelba

Pampa Energía S.A.

  • Predictive maintenance on SGT5-2000E gas turbine combustion chambers

Empire Generating Co LLC

Owned by Empire Acquisitions LLC
Operated by NAES Corp

  • Fall protection system continuous improvement project

Fairview Energy Center

Owned by Competitive Power Ventures
Operated by NAES Corp

  • Selection and optimization of remote monitoring and diagnostics
  • Enhanced DCS monitoring screens designed to improve starting reliability
  • Installation of redundant ammonia injection equipment reduces the probability of NOx exceedance

McIntosh Power Plant

Lakeland Electric

  • HRSG modifications to increase back pressure capability increase MW output
  • Mitigation efforts to protect 501G combustion turbine rotor through bolts
  • On-line monitoring and non-destructive testing to monitor the condition of steam turbine blades

St. Charles Energy Center

Owned by Competitive Power Ventures
Operated by Consolidated Asset Management Services

  • Improving safety and reliability with active wireless high energy piping monitoring

2022 Best Practices GT-based Plants

Amman Levant Power Plant

AES Jordan PSC

      • LFO day tank overflow shutoff valve improvements

Anson and Hamlet Generation Plants

North Carolina Electric Membership

  • Repair of PWPS FT8-3 dual-fuel nozzles

Athens Generating Plant

Owned by Kelson Energy
Operated by NAES Corp

      • Plant safety improvements
      • Water treatment enhancements

BASF Geismar


  • Increased equipment protection using duct burner firing overrides

Central Eléctrica Pesquería


  • Collector brush enhancement upgrade
  • Improved generator grounding brush system
  • UF 1500 module valve actuator upgrade
  • Dewatering pumps retrofit project
  • Redundant heat exchanger improves ZLD system operations

CPV Valley Energy Center

Owned by Competitive Power Ventures and Diamond Generating Corp
Managed by Competitive Power Ventures
Operated by DGC Operations LLC

  • Implementation of mobile electronic logging for operations, maintenance, and compliance
  • Employee-driven lighting enhancements for improved visibility at an indoor plant
  • Reduced outage time by implementation of steam turbine fast cooldown logic and procedures
  • Severe winter weather operations

Energía del Valle de México I

Owned by EVM Energia del Valle de Mexico Generador SAPI de CV
Operated by NAES Corp

      • Implementation of system to optimize gas chromatographs reduces consumables and maintenance costs

Essential Power Newington LLC

Owned by Essential Power LLC
Operated by Cogentrix Energy Power Management

  • Electronic contractor safety orientation program
  • Auxiliary boiler online instrumentation
  • Cooling tower chemical injection automation
  • Overhead door warning lights

Griffith Energy

Owned by Griffith Energy LLC
Operated by Consolidated Asset Management Services

  • Control-valve trim retrofit project yields significant savings

Kings Mountain Energy Center

Owned by Carolina Power Partners LLC
Managed by CAMS
Operated by NAES Corp

  • Steam turbine EHC fluid conditioning system
  • Remote user cybersecurity

Kleen Energy Systems, LLC

Owned by EIF Kleen, LLC
Operated by NAES Corp

  • Generator breaker moisture intrusion mitigation project

Lawrence County Generating Station

Owned by Hoosier Energy and Wabash Valley Power Assn
Operated by NAES Corp

      • Operator rounds software streamlines site O&M

Liberty Electric

Vistra Corp

  • Easy SDS file access enhances operator and contractor safety

Magnolia Power Project

Owned by Southern California Public Power Authority
Operated by Burbank Water and Power

  • Remaining agile in a changing generation landscape

Mid-Georgia Cogen

Owned by Rockland Capital
Operated by IHI Power Services

  • Combustion turbine fuel gas DP transmitter failure logic
  • Combustion turbine evaporative cooler supply water modification

Milford Power LLC

Owned by Starwood Energy Group and JERA Co
Operated by NAES Corp

      • Repurposing unused plant equipment for new service

MPC Generating

Owned by Mackinaw Power
Operated by Cogentrix Energy Power Management

  • Hydrogen cooling system upgrade

Pleasant Valley Station

Great River Energy

      • Fuel oil unloading piping modifications for faster offloading, extended fuel oil run times and increased resiliency during extreme cold weather events

River Road Generating Plant

Owned by Clark Public Utilities
Operated by General Electric

      • Hazard hunt program
      • Benefits of keeping a spare set of gas turbine inlet filters
      • Remote electronics for hotwell level transmitters
      • Ammonia piping upgrade project
      • MOV additions to manual steam valves

Rolling Hills Generating LLC

Owned by Eastern Generation LLC
Operated by Consolidated Asset Management Services

      • Excitation transformer termination cabinet humidity monitoring

Rumford Power LLC

Cogentrix Energy Power Management

      • Providing value through energy efficiencies
      • Hot-start efficiencies providing value

Salem Harbor Station

Owned by Footprint Power Salem Harbor Development, LP
Operated by NAES Corp

      • Winter readiness testing upgrades

Saudi Aramco Power Generation Sites

Saudi Aramco

  • Benchmarking a large gas turbine fleet to streamline O&M

Sentinel Energy Center

Diamond Generating Corp

  • Energy control and LOTO

State Line Power Station

Owned by Liberty Utilities and Evergy
Operated by Liberty Utilities

  • Second life for RO water

Walton County Power

Owned by Mackinaw Power
Operated by Cogentrix Energy Power Management

  • Gas room ventilation upgrade
  • Water wash system upgrade

Washington County Power

Owned by Gulf Pacific Power LLC
Operated by Cogentrix Energy Power Management

  • Electric fire pump testing procedures

Whitewater Cogen

Owned by LSP Whitewater LP
Operated by NAES Corp

  • Operational tag program identifies systems status

Worthington Generation Station

Owned by Hoosier Energy Rural Electric Co-op
Operated by NAES Corp

      • LM6000 package fan pulley/belt guards

Power Users forms Legacy Turbine Users Group (LTUG) for 7E, 6B, and Frame 5 Owners

By Team-CCJ | July 1, 2022 | 0 Comments

In the world of power generation there is a significant number of mature frame gas turbines that are the backbone for industrial settings and power generation. There are several well-established user groups that support owner/operators by sharing lessons learned, technical knowledge, and troubleshooting support. It’s critical that these groups maintain a strong presence in the industry to support and benefit both the users and suppliers that keep the equipment running. Combine that with a changing industry, a pandemic, shrinking budgets, and an aging workforce you now have challenges in keeping influential groups afloat.

With any challenge there is opportunity and that’s why Power Users formed the Legacy Turbine Users Group. Currently, LTUG comprises the 7EA, Frame 6B, and Frame 5 Users Groups. In combining forces, the future for these organizations will be stronger and have opportunity to grow. Each group maintains an independent steering committee and user forum hosted by Power Users, but when conducting a technical conference, the groups will be joining together under one roof, each in its own meeting room. Power Users believes this combined group provides many benefits to the user community and suppliers.

The first LTUG technical conference will be co-located with Power Users’ Combined Conference this coming August. For the first time, companies with a mixed fleet of these turbine types will be able to travel to one conference to gain the benefit of three. Additionally, companies that may not have such diverse fleets will be able to leverage the knowledge presented by these three groups with one trip. This addresses some of the challenges we are seeing that will likely to continue. Now companies can save on travel costs by attending an all-in-one conference and not have to choose which meeting to miss in a given year. All this without losing the benefit of training, sharing of lessons learned, building valuable networks, and meeting the supplier network that supports these gas turbines.

Suppliers also benefit from this merger of user groups. Their budgets are equally stretched, and the pandemic has made it challenging to share their services and build networks. The LTUG conference provides access to a diverse group of users that utilize a similar vendor base for support, parts, and services. This efficiency provides a budget-friendly opportunity for suppliers to build valuable connections to sell services and parts.

Our inaugural LTUG conference will be held in beautiful San Antonio (Tex), August 29 through September 1 (www.powerusers.org). Plan now to participate in this seminal event to strengthen your knowledge, build your network, share your experience, and find a supplier that can help solve problems your facility is facing.

Jake English, Duke Energy
Phyllis Gassert, Talen Energy
Sam Graham, Tenaska
Edward Maggio, TVA
Ben Meissner, Cogentrix
Peter So, Calpine

Collector brush system upgrade slashes maintenance requirements

By Team-CCJ | June 6, 2022 | 0 Comments

Woodbridge Energy Center

Owned by CPV Shore LLC
Operated by CAMS
725 MW, gas-fired 2 × 1 7FA.05-powered combined cycle located in Keasbey, NJ
Plant manager: Chip Bergeron

Challenge. Woodbridge was notified four months before the planned 2020 fall outage that the generator collector brush systems serving its gas and steam turbines soon would be discontinued by the OEM. Faced with the obsolescence of a critical high-wear system, plant personnel had to move quickly to plan for the upgrade while also capitalizing on any opportunity to eliminate the various issues that plagued the existing system.

Solution. Having spent several years working with Cutsforth on the excessive brush wear and selectivity issues related to the OEM system, the company’s input was sought on the pending obsolescence issue. While upgrading to a Cutsforth system is not new and something many sites might do in their lifetimes, the team need to go one step further and find a way to reduce the weekly labor hours dedicated to brush maintenance. The OEM collector system was costing the site approximately 900 man-hours annually to maintain.

To address this issue, Cutsforth proposed its most advanced brush rigging system available (Fig 1) which came complete with the company’s Brush Condition Monitor (BCM). The latter gives staff a real-time view into the health of each brush by displaying vibration, usable life, temperature, wear rate, and location. These data are readily displayed on a local PLC, which eliminates the need to manually collect data for each individual brush. The site team also developed plans to bring the brush data directly into the control room where it can be recorded, trended, etc, using the historian.

Results. In its first six months of service, the benefits of the new collector brush system exceeded expectations. The brush selectivity and wear-rate issues that plagued the plant during its first five years of service were completely gone, along with any signs of vibration and/or collector-ring pitting. This meant that collector ring grinds, which had become annual affairs, would likely be required only once every couple of years. The saving from the reduction in ring griding alone will save the project $40,000 annually.

Additionally, the new system has reduced the man-hours required for brush maintenance by a factor of two-thirds (about 600 man-hours annually), taking what once was a significant weekly effort and reducing it to minor-task status.

Project participants:

Justin Hughes, production manager

Michael Armstrong, plant engineer

Best Practice: Use EMI to assess the condition of generators, transformers, HV electrical gear

By Team-CCJ | June 3, 2022 | 0 Comments

Challenge. Soon after commissioning, one of Fairview’s gas turbine/generators experienced stator-ground-fault trips attributed to isophase-bus (IPB) water ingression into potential transformer (PT) cabinets, followed by persistent lower-than-expected resistance readings. Doble Engineering was engaged to perform electromagnetic interference (EMI) testing on several components of the plant’s three power trains to assess their condition. Generators, step-up transformers (GSUs), unit auxiliary transformers (UATs), and IPB were suspect in each train (Fig 1).

Following the first trip on stator-ground-fault 64 relay, damaged cables and condensation were found in a PT cabinet (Figs 2 and 3). To learn more on the importance of addressing grounding issues in a timely manner, read “IEEE standards may not sufficiently address grounding issues in rotor, stator windings,” by Clyde V Maughan, CCJ, 2Q/2013, p 7.

Solution. Given the extensive amount of IPB and connections, the CPV and NAES engineering teams advised the plant to perform EMI testing to identify other potential sources of arcing and abnormalities. An EMI diagnostic was conducted to determine the possible origin of the problems.

Recall that EMI testing is performed online and can detect several mechanical and electrical defects on generators, IPB, transformers, and motors. Defects in the bus connections or insulators generate radio-frequency signals that can be measured.

To perform an EMI diagnostic, a radio-frequency current transformer is placed around the neutral, a safety ground, or power conduit of the asset (Fig 4) to measure and identify the signals generated from the component or system defects. The EMI diagnostic method measures a broad spectrum of radio frequencies to evaluate signal patterns—including, but not limited to, corona, partial discharge (PD), and arcing.

Additionally, a handheld device is used in conjunction with the EMI signature to further identify the defect location. This device detects the EMI signals radiated from each component or system defect, allowing the technician to measure the intensity of the activity.

EMI testing is performed while the asset is in service and is a non-intrusive technique that will not cause the equipment to trip offline. A baseline measurement is helpful but not required for the analysis; therefore, maintenance recommendations are provided starting with the very first test, and the analysis helps to prioritize maintenance based on asset condition.

The generator, IPB, UAT, and GSU for each of the three units were tested and inspected. The table summarizes the most relevant findings. The EMI signatures in Figs 5 and 6 were acquired at different grounds on each component. The frequency ranges indicated on the EMI signatures, upon further and detailed analysis of the waveforms, revealed abnormal PD and sparking activities. Fig 7 is an example of a sparking waveform.

The activities detected typically are associated with insulation deterioration, defective connections, and loose hardware inside the IPB. To pinpoint the locations of the defects, a scan was performed with a handheld device to identify areas with high radiated EMI. After a thorough analysis, an internal inspection of different sections of the bus system was recommended.

Referring to the detailed EMI report provided by Doble, the locations identified in the table were highlighted on electrical one-line and 3-phase drawings. These marked-up prints were used to plan lockouts, scaffold erection, and inspections at the next planned outage. Figs 8-10 show examples of the findings in locations identified by EMI testing.

Results. Deficiencies were identified and corrected at each suspect location identified by EMI testing.

EMI testing enabled non-outage inspections of the electrical distribution system, thereby reducing the length of outage inspections and facilitating advance planning prior to the outage start date.

Given the success of the one-time EMI survey, CPV Fairview is installing a permanent EMI detection system. The team has initially selected the ST generator, IPB, and GSU for permanent monitoring.

A permanent installation may not fit everyone’s business model. As a minimum, we recommend conducting an annual survey or as-need surveys following repairs or the installation of new equipment.

Project participants:

CPV: Joe Michienzi, Preston Patterson, Tom Favinger, Ali Bibonge

NAES: Bill Lovejoy, chief engineer; Rick Marshall, maintenance manager; Jason Havash and Aaron Roberts, I&E technicians

Doble Engineering: Roberto Martinez and Oscar Montano

Fairview Energy Center

Owned by Competitive Power Ventures (CPV)
Operated by NAES Corp
1050-MW, 2 × 1 combined cycle powered by 7HA.02 gas turbines, located in Johnstown, Pa
Plant manager: Bob Burchfield

HRSG Forum discussion centers on creep damage, elemental zinc in weld HAZ areas

By Team-CCJ | May 16, 2022 | 0 Comments

As usual, a tremendous amount of technical content was offered in two presentations during the HRSG Forum, Jan 28, 2022—No. 7 in a series organized by Chairman Bob Anderson. But the underlying message was more about the state of our industry.

A few participants, discussing aging of high-energy piping (HEP), said they were “astonished at the lack of knowledge in major NDE [non-destructive examination] firms” and that boiler OEMs “are different” these days and there are new people in the industry. You can interpret “new” as suppliers who are inexperienced, or low-balling bidders, or doing shoddy work, but also buyers who accept low bids or don’t establish the proper design specs or QA processes and protocols.

Later in the Q&A, one Forum organizer, discussing zinc issues with boiler pressure parts, said HRSG OEMs are “not giving answers [about zinc] with high confidence levels” and that it is “buyer beware” when it comes to at least one OEM.

The first presentation, “NDE, Welding, and Metallurgy: Tools Supporting the Safe, Efficient Operation of Aging HEP,” was delivered by industry veteran Jeff Henry, now with the Combustion Engineering Solutions (CES) division of Advanced Thermal Coatings (ATC).

There are many reasons why you should care about aging HEP, but if you’ve recently upgraded your gas turbine for higher output and efficiency, you are likely going to be expending the creep life of your superheater and reheater piping faster than you might have expected. This situation makes HEP components more susceptible to catastrophic failures at the weld areas.

Creep is “time-dependent strain, or changes in dimensions of the material, that accumulates in response to stress such as load and pressure.” Over time, cavities form in the metallurgical grain structure, then begin to align into cracks which represent an “advanced stage of damage.” While creep can manifest as swelling of the pipe diameter, by far the most failures occur at welds, which are omnipresent in HEP systems.

Onset of creep damage of course depends on the type of material and alloy. For Grade 22 material, the values for elevated temperature, according to Section 2, Part D of the ASME Boiler & Pressure Vessel Code, start at 952F. Code fabricated materials should last 250,000 operating hours, Henry said, as long as piping supports are properly maintained, the components are operated within design limits, and the original fabrication was conducted to within specifications. For an aging facility, that’s a lot of caveats.

Inspection is critical to identify piping condition, but indications have to be properly characterized and the root cause understood before an effective repair is executed. In response to an audience question, Henry stated that 50,000 ops hours is a reasonable inspection interval if there are no operating or structural issues. When asked if there are protocols or industry standards, he recommended EPRI’s qualification and certification program for NDE detection in high-energy piping.

Many of Henry’s slides depict damage in six defined areas of HEP welds and are not to be missed if you are responsible for an aging HRSG. Get the details by watching the recorded presentation.

The second presentation, “Casting the Die: Implications of Zinc for Pressure Part Integrity,” was given by Paul James, Uniper Technologies Ltd. Main takeaway: Presence of elemental zinc (not zinc oxides) in paint used to protect weld prep areas before fabrication makes pressure parts more susceptible to creep damage, especially in the weld heat-affected zone (HAZ). Fortunately, according to James, elemental zinc bands, beige-yellow which darkens with exposure to high temperatures, can be readily distinguished from the red lead oxide coating/primer traditionally used.

During the Q&A, an informal poll of HRSG OEM representatives was cited, with several saying they’d never heard of the issue. James’ presentation also is available for viewing at 2022 Recordings (hrsgforum.com).

MD&A webinars focus on inspection, repair, upgrade of retaining rings, turbine valve actuators, fuel-nozzle life extension, plus alarm troubleshooting

By Team-CCJ | May 16, 2022 | 0 Comments

Summaries of MD&A’s spring 2022 webinars on topics of interest to all involved in the operation and maintenance of generating plants powered by gas turbines follow. Both experienced personnel and those new to the industry might benefit from a quick read to identify topics of immediate value and then follow up by listening to recordings of the webinars of interest. All run less than an hour.

To access MD&A’s library of webinar recordings, go to MD&A Webinar Library and register for access.

Take a deep dive into failures, repairs of generator retaining rings, main leads

Retaining rings (RR) and main leads are two of the most stressed components in large combined-cycle generators and thus prone to failures. James Joyce, generator repairs ops manager for MD&A, during a Feb 24, 2022 webinar, covered the basic design and purposes of these two components, along with what can only be called gruesome photos of what they look like when in disrepair or fail from mechanical and/or electrical issues.

MD&A has developed repairs and upgraded components, which should be considered as replacements when maintenance intervals allow. The slides depict the design, manufacturing, and installation process for these upgraded parts.

The many audience questions elicited additional valuable contributions to the presentation, including the following:

  • There is no such thing as “severe” retaining ring cracks. If there are any cracks, the component should be replaced, and preferably upgraded at the same time. Plus, cracks on the outer diameter end means there are cracks on the inner diameter end and it’s time to replace.
  • High-speed balancing is strongly recommended after retaining-ring replacement.
  • Follow OEM maintenance schedules for when inspections are due, but generally every two to three years and during a major overhaul.
  • Standard NDE for RRs is a dye penetrant test; radiographic tests are not normally performed.
  • A complete RR replacement takes five to seven days, depending on whether the size in question is in stock.
  • Damage to the RR from a motoring event will depend on the amp load and length of time; one type of damage mechanism could be arcing on the dovetail slots.
  • Continuous cycling will greatly impact the main leads.
  • MD&A is not aware of cracking issues with 18/18 RRs but cracks could show up in five to 10 years as operating hours are gained.
  • “Top tooth” cracking is rare, but does exist; perhaps 2% to 3% of units are susceptible.

To access MD&A’s library of webinar recordings, go to MD&A Webinar Library and register for access.

Sweat the small stuff when it comes to steam-turbine valve actuators

If you think your combined-cycle steam-turbine valve actuators are one of those “set and forget” components, think again. As Anthony Catanese explains during the Feb 15, 2022 webinar hosted by MD&A, “Turbine Valve Actuator Operational Issues and Upgrades,” even the most robust actuators, such as GE’s “legacy EHC,” running in a baseload plant may last up to 30 years, but “when they fail, they fail spectacularly.”

Actuators all function pretty much the same from a fundamental mechanical point of view, says Catanese—hydraulic force to open, spring force to close. But some designs are more complicated than others by virtue of their many bells and whistles (Rexroth) and/or more components (legacy Westinghouse). Check out the video if you’re looking for a refresher on fundamentals about the various popular designs.

Catanese’s recommendations for spares and maintenance intervals were the heart of the material. Generally, he says, plants should keep half a set of servos and solenoids in stores, although a full set is preferred, and filters, of course, should be changed regularly and oil kept clean. People tend to think less about the LVDTs and switches. Catanese suggests keeping one or two of these handy at all times.

As for preventive maintenance, legacy GE units should be sent to the shop every 10 to 15 years, legacy Westinghouse every five to eight years, and Rexroth and combined-cycle LP actuators every four to eight years. The rest of Catanese’s slides explain, through photographs of typical long-term damage to internal components, why disassembling, repair, and inspection during regular maintenance intervals is so vital: You want to identify issues before the actuator fails.

Insights gleaned from the Q&A:

  • If your actuator is experiencing stickiness or sluggishness, nine times out of 10 the problem will be with the servo.
  • Be sure to test disc springs if/after they’ve been coated—most sites neglect to do this.
  • If one disc spring in the stack cracks, replace them all; otherwise, the forces will not be uniformly distributed during closing.
  • MD&A is the only “sanctioned” non-OEM service firm for Rexroth actuators.

To access MD&A’s library of webinar recordings, go to MD&A Webinar Library and register for access.

Don’t fear the Mark VI Trender in your toolbox: It’s your friend!

If you are leery of using the Toolbox Trend Recorder/Trender function in the Mark VI and VIe control systems when your gas turbine is running, Joe Clappis, senior engineer, MD&A Control System Div, has a message for you: Don’t be! You don’t need a password and you can’t alter the turbine’s control logic. Clappis encouraged his audience during the webinar, “Troubleshooting Alarms and Trips with High-Speed Data Capture,” Feb 22, 2022, to get familiar with Trender, which he calls the “the best tool in the Toolbox.”

Unlike data historians, which typically capture data at rates of once per second or slower, Clappis noted, Trend Recorder takes data as fast as once per 40 milliseconds. Low-speed data capture is best for slow-moving long-term trends—such as bearing metal temperatures and vibration. High-speed data capture allows you to analyze control valves, combustors, inlet guide vanes, exhaust temperature spreads, and other variables which can change far more quickly.

Trend Recorder also captures alarms and events in addition to raw data and all the data can be viewed in graphical form.

“Users often send us screen shots, or smart-phone camera photos of HMI views, and ask us to troubleshoot a particular problem or event, but these are often not helpful,” Clappis lamented. However, data summarized and presented in Trender can be extremely useful. You can study starts and shutdowns, compare “good starts to bad starts,” study DLN combustor mode transfers, and identify intermittent issues. Or Clappis and company can give you a higher-level diagnosis if you send them Trender files.

Many of Clappis’ slides showed the audience how to find Trend Recorder/Trender from the Mark VI home page, create and save a Trend Recorder file in Toolbox or ToolboxST, analyze data, simplify screen views and graphics, and drill down to actionable data. Clappis distinguished between actionable data and anecdotal data, like “I saw this happen and it never happened before!”

For those unfamiliar with data analysis, monitoring, and/or control systems, it’s best to follow along with the recording of Clappis’ webinar with your Mark VI screens in view. He gives explicit instructions for how to navigate within the Toolbox and Trender.

Finally, OEMs typically configure data historians and high-speed data recorders poorly, usually trying to capture too much data too fast, but also often not capturing the right values for certain types of troubleshooting. Factory configurations are not tailored to the site, or require much special training to extract the value from the data. “You have to be dedicated to learning the system,” Clappis stated.

As a caution, Clappis reminded participants that Trend Recorder is not a substitute for long-term data archival and retrieval. In response to an audience question, Clappis noted that the Mark IV does not include a trending program, the Mark V, “sort of.” A feature called View Tools can collect data on a limited number of data points.

To access MD&A’s library of webinar recordings, go to MD&A Webinar Library and register for access.

More attention to fuel-nozzle upgrades, repairs pays huge dividends

Blind faith in your OEM’s DLN fuel-nozzle component repair and replace recommendations could kill your outage budget, and that’s not all. That was the underlying message during the Feb 17, 2022 MD&A webinar, “Gas Turbine Fuel-Nozzle Flow Issues,” led by the tag team of Joe Palmer, general manager, and Pat Murphy, director of the company’s Fuel Nozzle Services Group, formerly ICS.

Fuel-nozzle overhaul is often the lowest cost area of a scheduled outage, and therefore not at the forefront. That’s a shame, stressed Palmer and Murphy, because many combustor issues originate with the fuel nozzles. Thus, there are other important benefits of upgraded fuel nozzles—easier tuning at startup, reduced temperature spreads, and less risk of lean blowout. Improperly maintained fuel nozzles also adversely impact the life of major hot-gas-path (HGP) components.

MD&A has developed, and fully warrants, upgraded fuel nozzle components for 7FA DLN 2.0- and 2.6-equipped engines (and combustors of other models), especially the subassembly wear parts. Remanufactured nozzles from MD&A are warranted as “like new” and can operate nearly “indefinitely.” For example, upgraded outer/center nozzles, using several part calculation strategies, could operate for nearly 148 factored years! Meanwhile, the OEM claims a 48,000-hr lifecycle for its component. The as-new quality parts are a fraction of the cost of OEM replacement components, claims MD&A.

The third-party solutions provider’s new end-cover insert can operate over seven repair cycles. MD&A’s improved brazing process and choice of braze material have greatly improved cover life. Plus, the amount of cyclic insert braze cracking has been reduced. Several of the slides are dedicated to explaining and illustrating the detail of this component “case study.”

The company offers an exclusive “in-situ flow testing” method, which helps pinpoint nozzle issues and solutions. “Component balancing and set balancing of fuel nozzles also can avoid a separate combustor inspection (CI) and extend run time to the next HGP outage.” The exclusive testing is an alternative to a complete nozzle system teardown for pinpointing flow variances and accurately and expediently addressing them.

To access MD&A’s library of webinar recordings, go to MD&A Webinar Library and register for access.

Thermal performance audit key to extracting more dollars from older plants

By Team-CCJ | May 16, 2022 | 0 Comments

The road to net zero carbon by, well, pick your date, 2030, 2035, 2050, is paved with pledges, promises, mandates, and political rhetoric, but the landscape will most surely be dotted with gas-fired combined cycles making megawatt-hours when the variable renewable resources are not, according to Jeff Schleis, gas-turbine product manager, EthosEnergy.

In a recent webinar, Schleis reviewed net-zero-carbon trends at the national level, offered some insight gleaned from Black & Veatch’s Annual Strategic Directions Report (a survey of industry leaders on top-of-mind issues and investment scenarios), and compiled three recent net-zero forecasts on one graph. Register here to view the recording.

Upshot of the last is that variable generation could exceed firm in less than 20 years. That represents opportunity for gas-fired combined cycles, but you have to be intentional about it. Schleis advocates conducting a thermal performance audit (TPA) to identify the gaps in performance, or where an older plant can extract additional value.

Equipment degrades over time, he said; the goal of the TPA is to analyze historical operating data and glean info from the operators to build a plant model that captures current equipment condition. Then you compare existing performance to original design, and individual turbines to each other, to determine where the gaps are, and what investment is required to close those gaps and extract the dollars.

The balance of Schleis’ slides is a deep dive into a case study on a 4 × 2 plant “designed to be very flexible.” High-level results were presented. The one audience question directly relevant to the presentation queried the time it takes to conduct the example TPA and the “timeframe for improvements.” Schleis answered that the study takes six to eight weeks depending on plant complexity.

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