7F Digital Conference: Week 3 starts tomorrow, focuses on rotors, lubricants, repair of HGP parts

Week Three of the 7F Users Group’s innovative 2020 Digital Conference begins tomorrow at 1 p.m. Eastern with Tim Null, O&M team manager at Eastman Chemical Co’s 7FA.03-powered 2 × 1 combined-cycle cogen facility, presenting a case history on the Texas plant’s experience in finding and eliminating the source of water contaminating its lube-oil system.

Week Two of the conference, like Week One, characterized by meaningful discussion and presentations sharing valuable lessons learned, exceeded expectations. Nearly 600 owner/operators registered for the meeting. Sessions are scheduled for the next three weeks (including this week), closing July 16. Registration remains open for users only at no charge.

The content is compelling and easy to access; plus, no travel required, no additional cost to the plant. Q&A following the presentations is more robust and efficient than at most face-to-face meetings which have “dead” time as microphones are passed around the room and attendees gravitate to email. And don’t forget the perspective gained through use of the live polling system accessible by all attendees.

Tomorrow’s Auxiliaries Session, chaired by Entergy Corp’s Bryan Graham, has an open discussion period scheduled after Null’s presentation. Later in the program are the following special technical presentations, by vendors, that have been vetted by the 7F Steering Committee:

Attendees will have access to these speakers after their presentations during a “private” vendor fair for both suppliers, enabling a deeper dive into specific details of value to their plants.

The Rotor Session, directed by Matt Dineen of Duke Energy, chair of the 7F Users Group’s 2020 meeting, debuts on Wednesday at 1 p.m. The feature presentation is on rotor maintenance experiences. Vistra Energy’s Seth Story, will help attendees extract the most value from their assets.

Immediately following rotor Q&A and open discussion, Glenn Turner, Doosan’s VP of Engineering, will present on the following topics:

    • DART/AGP parts program development.

    • 04 parts repair development.

Turner and colleagues will be in Doosan’s “booth” at the exclusive virtual vendor fair that follows this session where they will be available to answer your questions.

Posted in 7F Users Group | Comments Off on 7F Digital Conference: Week 3 starts tomorrow, focuses on rotors, lubricants, repair of HGP parts

7F Digital Conference: Week 2 user, vendor presentations recapped here

Editor’s note: What follows are summaries of user and vendor presentations made last Tuesday and Wednesday. They illustrate the value of participation in both the 7F Users Group’s 2020 Digital Conference and the organization’s upcoming 30th Anniversary Meeting at the Marriott St. Louis Grand, May 24-28, 2021. To dig deeper, PowerPoints or video recordings of the presentations, are now available on the Power Users website to registered owner/operators. Registration is easy if you don’t already have a “library card.”

River Road’s non-chemical approach to cooling-tower algae control

River Road Generating Plant, a 7F-powered 1 × 1 combined cycle, originally used chlorine for algae control in its cooling tower. At the first NPDES permit renewal, the state of Washington’s Dept of Ecology compelled the facility to eliminate the use of chlorine and shift to bromine.

After several years of bromine use, the plant began to experience intense blooms of a resilient and chemically resistant form of filamentous blue-green algae, which was out of control in spring and summer. Algae could grow more than 2 ft/day on sunny days, requiring cleaning of the forebay trash screens every two or three days. A crane was required to dispose of the nominal 2-ton harvest.

With chemical solutions limited, plant management challenged staff to explore the following non-chemical options: electrocoagulation, ozone generation, ultraviolet light, ultrasonic devices, magnetic devices, modulated molecular oscillation pipe wraps, lattice oscillation devices, radio-frequency generators, and cooling-tower shading.

One of the first steps was the trial of an ultrasonic device designed to kill the type of algae affecting the plant in its single-cell form—before it could morph into colonies. The floating transducers emit ultrasonic sound waves that oscillate in frequency, and change periodically, to kill multiple types of biological growth and to prevent mutant strains from developing.

Ultrasonic waves create a so-called “sound barrier” at the water/air interface that prevents some types of algae from floating to the surface for photosynthesis; without surface light, algae die.

Bacteria are killed as well. This means colonies of bacteria are not available to adhere to cooling-tower surfaces. The strand-type algae found at the plant will not attach to surfaces that do not have a layer of biofilm, and the offending cells pass through the system. But while providing a substantial reduction in algae growth, ultrasound did not eliminate the algae infestation during the summer.

Sun shades were considered because algae require sunlight for photosynthesis. This low-tech solution helped to reduce algae growth and the cost of chemical treatment.

RF devices. Ultrasound and sun shades together reduced the amount of algae dramatically, but not completely. Radio-frequency devices, which successfully helped control the effects of biological growth and silica in small cooling towers for HVAC systems, were tested next. The underlying theory is that radio frequency disrupts the lifecycle of the algae in its single-cell form.

Plant and vendor personnel worked together to develop and implement an industrial-scale test plan. The speaker displayed results slides at intervals of about 10 days over a six-week period and the results were compelling. The last slide showed no algae were present. The test was repeated and results were the same. Another benefit: Silica drops to the bottom of the tower basin and is removed during blowdown.

While the benefits of RF devices are impressive—including improved personnel safety, reduced chemical consumption, longer intervals between cleanings of condenser tubes—the speaker pointed out that you never completely eliminate algae because the cooling tower is open to atmosphere. Thus, bromine still is injected, but only every fifth day.

Benefits still to be quantified include the reduction in calcium silicate scale in the condenser and plate heat exchangers, and the reduction in cooling-tower chemicals possible—such as silica dispersant. Stay tuned to CCJ for updates.

GCE replaces exciter during peak demand with minimal financial impact

One of Green Country Energy’s 9A4 generators experienced a ground-fault trip on its Kato brushless exciter because of a winding insulation failure—after nearly 18 years (about 80,000 hours) of service. The nominal 800-MW plant is equipped with three 7F-powered 1 × 1 combined cycles; the steam turbines are married to 9A4 air-cooled generators.

Routine inspections and tests were conducted over the years and the exciter historically had been reliable. The stator had been removed numerous times, the rotor never.

The plant’s highly capable staff was challenged to remove and replace the exciter during a period of peak demand while limiting financial impact. This included the following actions:

    • Reduce peak-demand forced-outage penalties to the extent possible.

    • Locate a replacement exciter.

    • Evaluate the risks and rewards of performing repairs onsite.

Several hurdles were encountered:

    • Kato no longer manufactured replacement brushless exciters for the 9A4. An interesting finding given the 9A4 had been introduced only 20 years earlier.

    • No direct-replacement brushless exciter was available from an alternative manufacturer.

    • Removal and installation of the exciter rotor requires specialty tooling that the plant didn’t have.

    • The repair cycle for rewinding the exciter would require a lengthy forced outage.

The goal was to develop a plan to minimize the forced-outage impact by locating and installing a replacement exciter while the failed exciter was repaired and put in the GCE warehouse. Luckily, a new old-stock spare exciter was located at a partner facility that the plant had shared parts with previously.

Finding the Kato instructions for exciter rotor removal and replacement vague and inaccurate, staff reached out to other plants to discuss their lessons learned and best practices. Some owner/operators reported success, others said there were complications that led to complete removal of the generator field for offsite repairs—attributed to binding of the exciter rotor on the generator shaft.

Thus, the solution was to purchase the spare exciter identified and manufacture in-house the specialty tooling required for removal and replacement. That tooling has since been loaned to at least one other plant.

The bottom line: Plant staff took what easily could have been a three-week outage and completed it in six days, the speaker acknowledging that this was possible because of industry cooperation in obtaining the new exciter and the sharing of experiences by others to develop a good work plan.

ExxonMobil, GE collaborate on development of energy-efficient turbine oil

Mobil SGC™ 918 EE is a new turbine oil designed to provide energy-efficient benefits in GE 7FA and 6FA gas turbine/generators. Developed jointly by ExxonMobil and GE, it is the first product to meet GEK 121603, the OEM’s energy-efficient turbine-oil specification. The new formulation is based on Mobil DTE 932 GT, which the presenter said has been used successfully throughout his company’s frame fleet for the last decade.

According to the user presenting, the new oil provides an overall turbine efficiency improvement when compared to conventional ISO 32 viscosity grade lubricants. Performance was measured in a GE-designed bearing rig, the 7HA test stand, and during 7FA and 6FA field demonstrations.

The speaker reviewed the technical evaluation process used by personnel at the 7F-powered cogen plant charged with the investigation. But before digging into the details, he polled the audience with these two questions:

1. Have you changed the type of lube oil in your gas turbine? Attendee feedback: Yes, 29%; considering it, 20%; no, 51%.

2. For those who did not respond with a “no,” 60% said they performed a full technical evaluation, 18% had the lube-oil suppler to do the evaluation; the remainder simply relied on the experience of others.

The evaluation process described by the speaker began with two 2-hr brainstorming sessions in which key participants participated. After back-and-forth calls over about a week’s time to iron out details, work began with a gathering of P&IDs for the turbine involved in the demonstration. These were used to identify all components and instruments that comprise the following systems: lube oil, hydraulic oil, trip oil, lift oil, and generator seal oil.

Next step was a review of system components by machinery engineers from the plant owner/operator, lubrication experts, and OEM personnel to identify potential concerns with the lower viscosity of SGC 918 EE compared to that of the DTE 932 GT currently used. Note: Because the new formulation is based on the current oil, the evaluation team excluded from review the compatibility of coatings and elastomers with the SHC 918 EE.

The speaker then described the type of matrix used to guide the technical evaluation process. This slide might be of benefit to others considering an oil change—that is, any oil change, not necessarily a switch to SHC 918 EE. One illustration offered concerned lift oil: Would a system adjustment be necessary because of the different viscosity? In this case the answer was “no.”

Another one of the concerns evaluated involved hydrogen seals on the generator: Would there be a need to increase generator seal-oil flow and hydrogen consumption to maintain generator H2 purity? The lower viscosity dictated a change to a bolted seal to maintain hydrogen purity.

The sump for the gas turbine selected to demonstrate the value of SGC 918 EE in an industrial setting has been filled with the new oil; a July restart is planned. Connect to the 7F Forum for progress reports as they become available.

As generators age and unit cycling increases bad things can happen

AGT Services’ Jamie Clark has been on a mission for the last couple of years presenting at the annual meetings of all major users groups to alert owner/operators about the significant increase in generator failures his company and other service firms are seeing. These failures are related in large part to unit cycling and age, with lapses in attention to detail during inspection and maintenance contributing.  Recall that most generators at 7F combined-cycle plants were designed for baseload, not cycling, service.

Clark’s presentation last week at the 7F Users Group’s 2020 Digital Conference, “Five minor generator inspections turn into three majors for repairs,” illustrated the dramatic increase in the amount of emergent work some users are experiencing and its costly impact on both maintenance budgets and schedule.

His 7F presentation was similar to one he gave in June 2019 to the Frame 6 Users Group, attesting to the existence of an industry-wide problem, not one affecting a given frame.

Clark began his 7F presentation with a chart illustrating the dramatic increase in the number of starts experienced by a combined-cycle plant in Maine in the last decade compared to the start stats for the facility’s first eight years of service. He then polled attendees, asking how the number of starts in the last 10 years compared to years earlier at their plants. Nearly one-third of the users reported up to a 50% increase in the number of starts; 11% said their starts had doubled; 3% said starts had more than doubled.

Next, he asked the users to share their most common “unplanned” stator repair/upgrade finding during an outage. If you think it is endwinding dusting/greasing or resonance repair, you’re correct. Well over half the respondents said “yes” to that. Other choices were belly-band tightening or new install, stator re-wedging (full or partial), and stator core looseness.

Clark then highlighted the primary areas of the stator affected by cycling, including the following:

    • Endwinding vibration/loosening, noting the higher risk for strand-to-strand series connections.

    • Core looseness impacts, such as keybar rattle/belly bands and loss of core compression.

    • Slot support system—including wedge system and side packing/ripple springs.

The speaker stressed that all stator parts are designed to work together as a system. Example: Bellybands restrain keybars and when loose allow keybars to “rattle” producing iron oxide particles.Add in some oil and you have greasing that lubricates the connections, further compromising tightness.

Later Clark would address the many areas of concern cycling poses for fields—including slot component migration, turn insulation migration, copper distortion, braze failures, issues with collector systems, and brushless exciters.

There’s much you can learn from industry generator O&M experience to improve the reliability and availability of your plant. If you were unable to participate in the AGT Services session, access the recording on the Power Users website. How much you learn in only one hour might be surprising.  

Come up to speed on today’s turbine tooling  

Plant personnel are always challenged to perform outages faster, safer, better than previously; improved tooling might be one way to help you achieve those goals. But it’s difficult to keep up with new developments in a demanding plant environment. A virtual conference benefits in this regard, facilitating learning via field videos of actual work and simulations.

Enerpac had three experts—Mike Beres, Chris Stocker, and Phil Giagnacova—presenting on tooling solutions during its 1-hr session at the 7F 2020 Digital Conference last week. “Optimize maintenance: From turbine decoupling to rotor removal and alignment” was illuminating. It covered turbine-case removal, a safe and efficient coupling-bolt solution, turbine rotor removal, generator rotor removal, journal turning (field machining), etc.

The format was to review the “current state” of each of these applications and then demonstrate the “future state.” To illustrate: The current state of turbine-case removal relies on fixed slings and mechanical turnbuckles. The risks posed by these methods include working from height, ergonomic issues, large heavy components, insufficient adjustability. The future state using the equipment demonstrated focused on hydraulic turnbuckles and adjustable rigging beams. They permit precision adjustment and from a hanging load, allow control away from the lift, and have ergonomic benefit.

The company’s space-efficient ETCT (Enhanced Turbine Coupling Tool) solution was said to save more than six hours in tensioning a 7F coupling than the same job would take with a tool commonly used today. The time to tension joints on four 7FAs at one plant with current-state tooling was estimated at 32 hours. Enerpac tensioned the four units in just over nine hours. This is particularly impressive performance given 60% of users said coupling was on the critical path for their outage.

The recorded session soon will be available for viewing, complete with videos and simulations, on the Power Users website.

MD&A’s session focuses on Mark VI/VIe controls, HGP parts, fuel nozzles, generators

MD&A divided its two-hour session last Wednesday into four parts so crammed with information of value to O&M personnel that having recordings of each segment available on the Power Users website benefits both those who missed the presentations and those who didn’t but want to clarify some points. The video format used is convenient, enabling you to identify the information you want quickly.

What follows is a TV Guide-type summary of the material presented:

    • A Mark VI/VIe presentation by Senior Controls Engineer Joe Clappis focuses on the Toolbos/ToolboxST trend recorder a/k/a trender. It is used for capturing and analyzing data and for troubleshooting—more specifically, for analyzing trip history data (hourly data between trips/stops, trip display data, and information captured by the dynamic data recorder. If you’re unfamiliar with this tool, listen to the half-hour video. Clappis is a highly knowledgeable controls engineer, excellent presenter, experienced teacher, and patient. You might just be introduced to an element of the Mark VI/VIe that can save you considerable analytical time.

    • Lifetime extension of 7FA HGP components was covered by Engineering Manager Jose Quinones, PE. Life-limiting factors of HGP parts, lifetime extension steps, implementation of repairs, and upgrades/modifications/improvements are included in the presentation. Quinones moves quickly through this material and you may have to listen to him a second time to confirm specific points. Perhaps the most valuable portion of the presentation is case histories that begin with evaluation of field condition, repair options, possible improvements for life extension, and results.

    • Fuel-nozzle end-cover-insert life extension was discussed by GM Joe Palmer of MD&A’s Fuel Nozzle Services Div. He covered system and product lifecycle analysis, technical advancements and life extension, and testing and validation. The graphics used to explain the cracking issue, design enhancements, and repairs are of great value to the unfamiliar user.

    • 7FH2 field-winding shorted turns and groundwall failure by James Joyce, a generator specialist at MD&A essentially is a short course the explains what shorted turns are, what causes them, and how to test for shorted turns online and offline. The hot spots and thermal vibration that result from shorted turns are explained. Explanation of rewind and patch-repair options for dealing with shorted turns follows. Groundwall insulation failure is explained in the second part of the presentation. Damage and causes are described along with the recommended repair.

Posted in 7F Users Group | Comments Off on 7F Digital Conference: Week 2 user, vendor presentations recapped here

Easily connect with and view presentations from key suppliers @ 7FUG 2020

One of the unique aspects of the 7F Users Group’s 2020 Digital Conference is the opportunity to interact online with the OEM and nearly 50 third-party solutions providers. Ten companies in the latter group were selected by the steering committee to conduct live technical presentations of one or two hours during Weeks Two, Three, and Four of the five-week program ending July 16.

The remaining solutions providers participated in the conference with virtual booths in the Vendor Fair conducted Tuesday and Wednesday of Week One. They connected directly with users via video (or audio) conferencing platforms. They also provided recorded technical presentations for users to access on-demand throughout the year, which can be viewed below.

In case you missed the opportunity to visit with one or more of these companies at the Vendor Fair, the editors provide below brief summaries of the products/services they showcased along with links to that information. The names of experts to contact for details are included.

Suppliers not included in the list below will be profiled in CCJ ONsite before our coverage of the 7F meeting concludes on July 20.

Allied Power Group 

Introducing APG Nexgen™ combustion technologies

APG President Jim Masso reviews the company’s recent acquisitions—Nexgen (advanced fuel systems), Texas Metal Printing (3D printing of turbomachinery components), and Eta Technologies (largest non-OEM V-series engine component and repair supplier)—and then summarizes the company’s capabilities in NDT, metallurgy, chemical stripping, grit blasting, rotor repair, and onsite field service. APG’s coating technology and capabilities are discussed next along with comprehensive combustion repair. A shop tour is included.

Custom engineered solutions for F-class owner/operators follow—including problem diagnosis and RCA capabilities, calibration and flow testing, and parts reconditioning. A technology solution of interest to many users is the company’s brazed insert replacement for the 7FA fuel nozzle. Engineered solutions include output and firing-temperature increases, 7FA.04 repairs, life extension, etc.

GTC Control Solutions

Operational tips through case studies, TIL 1524 and 1275 implementations, LVDT calibration

Chief Engineer Abel Rochwarger, respected by many in the industry for his controls expertise (and his unique brand of comedy), helps users understand the factors that determine “single points of failure” and how to identify them, plus the not-so-evident aspects of the relevant Technical Information Letters that can be learned only after implementation.

The takeaways: Users with Mark VI controls will learn about previously unknown/undisclosed failure modes, how to determine if their control systems are potentially susceptible to them, and what the options are for avoiding future occurrences. Personnel from plants with Mark V controls will come up to speed on two new cards from GTC that can help extend the lives of their panels.

Bonus discussion: Average versus core-by-core LVDT calibration.

Nel Hydrogen

Hydrogen generation ensures reliable hydrogen supply for CCGT powerplants

Dave Wolff discusses the use of onsite hydrogen gas generation as a safer, more economical alternative than delivered hydrogen for generator cooling. Users will gain an understanding of how ultra-pure, pressurized, dry hydrogen gas is produced onsite from electricity and water using the company’s compact Proton Exchange Membrane electrolyser. Applicable system drawings are included.

Nitto Inc 

Introducing hydrogen detection tape

The physical properties of hydrogen gas make leaks extremely difficult to detect. Finding leaks quickly is important to ensure personnel safety and to protect critical plant assets. Dr Nahid Mohajeri, GM of advanced polymer technology at Nitto, explains the company’s industrial-grade adhesive tape, which is applied to hydrogen-system components most likely to leak—such as flanges. The tape changes color from amber to black when exposed to even the smallest amounts of hydrogen—concentrations of 1%, for example. Powerplant experience is shared along with lessons learned. 

Parker Hannifin Corp – Energy Division

Reduce maintenance concerns and costs associated with gas-turbine fuel control valves

Jim Hoke, Parker’s capital projects manager for power generation, provides users technical information on the company’s line of electrohydraulic servo valves required for decision-making. The valves are approved by GE for use on its gas and steam turbines for the following applications: control of gas and liquid fuels, steam-valve actuators, inlet guide vanes, and stop/ratio actuators. 

Key takeaways from the presentation include these:

    • Parker’s “soft-fail” electrohydraulic servo valves if plugged will not cause the downstream actuator to fully extend or retract—it will remain in place. However, the valve can be spring-biased to move the actuator to a preferred safe position.

    • The product is a drop-in replacement for many servo valves in use—including hydraulic mounting and electrical connections.

    • Large orifice diameters allow contaminants to pass through instead of obstructing flow.

    • Hydraulic spool, designed with a significant chip shear force, enables continued operation in hydraulic systems experiencing varnish buildup.

    • The robust design allows extended intervals between PMs, calibrations, and tests.

Dekomte de Temple 

Fabric expansion joint solutions for 7F CCGT plants

Jake Waterhouse, group technical director at Dekomte, is a frequent speaker at user-group meetings. Here he discusses the benefits of retrofitting the 7F flex seal, used where the diffuser transitions to the cold casing, with a high-quality fabric solution for longer life and greater durability in cycling plants. Other applications for fabric expansion joints include the HRSG inlet and outlet.

Inspection (visual and thermographic) is the first step in understanding the existing condition and technical requirements to develop a tailored long-term reliable solution, says Waterhouse. Another input to the decision-making process is a review of operational criteria to identify to the degree possible expected operating parameters going forward.

Waterhouse shows with drawings and photos the details of the company’s expansion-joint offerings and presents case studies to illustrate the challenges posed by different gas-turbine models and the successful solutions implemented.

Conax Technologies

Power Division capabilities overview

If you’re unfamiliar with Conax Technologies, which manufactures temperature sensors, compression seal fittings, and cable harness assemblies, watch the 2-min video for an overview of the company’s capabilities and products for generating plants. In addition to standard off-the-shelf products, custom-engineered solutions are available to address the industry’s most demanding challenges.

Here’s a shortlist of products and services available from Conax:

    • Exhaust-gas thermocouples.

    • Sensor cable assemblies.

    • Bearing temperature sensors and seal feedthroughs.

    • Temperature-sensor harness assemblies.

    • Vibration analysis, accelerated lifecycle qualification testing.

Donaldson Company, Gas Turbine Systems

Technology solutions providing more power to you

Donaldson’s Casandra Light and Mike Carlson walk you through the company’s Three Pillars of Filtration methodology focusing on efficiency, water tightness, and pulse recovery rate to provide your plant the optimal filtration solution. Case histories illustrate the value in adopting Three Pillars.

ESC/Spectrum

Optimizing your data acquisition system with StackVision: Best practices, sound advice

Andy Taer brings you up to date on the Austin (Tex) company and its data acquisition system software—including StackVision™ and SpectraView® Prism—for continuous emissions monitoring systems.

Products and services, in addition to the DAS software, include the following:

    • Software IT services—including hosting, upgrades, and system migration server management.

    • Software customer support, documentation, and training services.

    • 8864 Data Controller hardware.

    • CEMS maintenance and training.

    • Stack testing for RATA, permit compliance, and engineering studies.

    • Repair and calibration of CEMS equipment.

    • Mobile testing systems and parts for CEMS.

    • Compliance reporting services.

Hilco

Coalescer separator, oil mist eliminator help bring fluid contamination problems under control

Two short videos illustrate how the company’s equipment works and the results it offers in terms of water and contaminant removal. Hilco goes beyond filters to provide a full-service fluids-management process—from obtaining samples to analysis to consulting to field service.

The total oil maintenance service offered by the company contributes to a reduction in new oil purchases, lower disposal costs, less wear of lubricated parts, and less downtime.

Team Hilco posits that the reliability and efficiency of any filtration system depends chiefly on cartridge quality. The company offers a full line of cartridges for virtually every application—depending on size, filtration efficiency, and dirt-holding capacity. Most fluids serving in powerplants generally can be restored to a like-new condition. Hilco’s world-class laboratory offers a full suite of test capabilities to support industrial filtration and fluid analysis.

Posted in 7F Users Group | Comments Off on Easily connect with and view presentations from key suppliers @ 7FUG 2020

Commentary: The value of remote technical support during generator inspections, maintenance

Clyde V Maughan, president, Maughan Generator Consultants

Cost-containment initiatives over the past several years have encouraged the move to more offsite technical support of outages in powerplants. More recently, Covid-19 travel restrictions have made onsite technical support difficult. Thus, offsite support via video-chat technology has become more common. This has encouraged discussions questioning the adequacy of such offsite support. Recently, a roundtable was convened on this topic on the website of the International Generator Technical Community (IGTC).

Participants requested examples of successful specialist remote support. Response was high: six from engineers employed by owner/operators, 36 from consultants. Few of the responses provided information on successful remote support; most were comments on the adequacy of offsite support (sidebar). Owner responders all preferred onsite support but considered remote support as having value.

Remote support. Offsite support can have important benefits to owner/operators. Most importantly, perhaps, is that the convenience of remote support expands the available pool of consultants and the travel money saved can be used for second, possibly third, opinions.

Why is this important? Not all “experts” are experts on all topics; some, in fact, may not be expert at all. But when a generator owner/operator brings an “expert” onsite, that individual likely will be the only expert with whom it will talk. There have been incredible errors made by such “experts.” Here are three examples:

Unqualified expert. On a routine inspection of a large, modern generator the owner brought in a local “expert” who advised misuse of a common stator winding test. This resulted in a recommendation to rewind, which cost close to $100 million in unnecessary rewind and replacement-power costs.

OEM engineer error. A 20-yr misunderstanding by OEM engineers of a stator-winding wear mechanism on a line of large generators resulted in rewind and loss-of-generation costs approaching a billion dollars.

Multiple experts onsite. A very large, very old 4-pole generator with asphalt stator windings was being operated 40 hours annually in a university research laboratory. During a field-out inspection, both an OEM engineer and an independent consultant recommended the following: “Rewind now or risk catastrophic failure.” A consultant with extensive experience on asphalt windings recommended the plant “Hipot the winding at 1.5E, and plan for the next field-out inspection 200 years from now.” The university is following the latter recommendation and avoiding a difficult $3-million rewind—at least for now.

Had the owners in the first two examples been able to tap into a pool of competent consultants and obtain the guidance of a second or third opinion, these very costly situations might have turned out quite differently. Furthermore, the second example illustrates the potential value to owners of having access to a pool of skilled experts when an OEM may be recommending questionable actions.

The availability of talented offsite support will make obtaining the views of multiple consultants convenient and cost effective and will offer the owner ready access to multiple options.

Clyde V Maughan retired from active consulting in July 2018 at the age of 92. Today he spends free time sharing unselfishly his extensive knowledge of generators with those seeking advice. The Clyde, as he has come to be known, spent 36 years with GE before “retiring” in 1986 to form his consultancy. Much of the knowledge Maughan acquired during his 70-yr career has been shared with the electric power industry through more than two-score technical papers, more than a dozen CCJ articles, several webinars, his handbook “Maintenance of Turbine-Driven Generators,” dozens of seminars, and other avenues of communication. He also founded the Generator Users Group with help from a few industry associates and contributed significantly to the launch of the International Generator Technical Community. Almost forgot…Happy 94th Birthday, Clyde!

Becoming a generator expert. One of the technical-support issues an owner faces is selection of an appropriate consultant (expert) for the job at hand. How does an “expert” become an expert? In my attempt to understand generators over a 70-yr career, I had the privilege of learning from a dozen incredibly talented industry engineers. Most of what I know I learned listening to these dozen men. Two diverse examples: Dean Harrington (deceased) from an OEM and Jim Timperley from a utility. Most capable experts have had similar experiences. But today most consultants will not have that privilege, nor in the future is it likely to be even available.

Depending on the properties of the mind of the individual, no amount of training may make a generator expert. Reason: The generator is a highly non-intuitive and extremely complex machine. Unless a person is gifted with a mind that deals well with the non-intuitive and complex, that individual may never become an expert.

As a consultant, 25 years ago I threw caution to the wind and wrote a book on generator design, duties, and deterioration. Using this book I conducted more than 30 two-and-a-half-day seminars for over 1000 attendees. I hoped to provide sufficient information that the user participants would learn enough about the generator to differentiate between an expert and non-expert. I was not trying to make, nor could I make, experts of them in a training course.

The future. As the use and value of offsite support expands, there are several factors to consider, some of which are mentioned below:

Remuneration. The average cost for a site visit by a generator consultant today, including travel, hotel, meals, etc, probably is in the neighborhood of $15,000. That number might be reduced by one-third or more by opting for remote access.

Decision between onsite and remote support. I made about 450 onsite visits in my consulting career. Probably half could have been done well offsite with present technology. With better technology and a trained onsite owner’s engineer, three-quarters, or more, of these jobs could have been done well remotely. There are many variables in this “equation” but certainly in the future many onsite visits can and will be replaced with remote assistance. The outcome of the onsite-to-offsite transition will depend a great deal on participation by all affected parties.

Owner support onsite. Remote technical support demands that the owner have a knowledgeable, capable individual onsite. Training for this assignment can be provided by seminars that teach the fundamentals of generator design, deterioration mechanisms, inspection, test, and maintenance—as described earlier.

Capability of consultants. In an offsite world, the true expert will be able to handle many more jobs. A way for owners to share their confidential assessments of individual consultants should be developed so the best engineers will be among those considered for a particular assignment. A secure user-only website, such as that hosted by the Generator Users Group, might be considered for this purpose.

Industry conferences. Online conferences, while not ideal, have major advantages. For example, rather than spending a week away from the plant, the participant spends a couple of days attending the conference from his/her office. Think of the time/cost saving. The reach of an online meeting also is much greater because of favorable economics and convenience. It’s possible, for example, that a meeting of the Generator Users Group could attract a few hundred participants rather than the two or three score it typically hosts.

Technology advances. The ability to transmit high-resolution photographs to experts starting about 20 years ago made offsite analysis practical and jump-started the alternative to onsite evaluation. The same is true of today’s video cameras and video chat systems for offsite support.

Summing up, the evolution in technical support toward offsite support is inevitable. For it to be done well to the maximum benefit of owners, plant and central-office personnel need to take a leadership position in the transition effort.

What others think about the value of remote support

Engineers with experience in the operation and maintenance of electric generators recently shared their views on the value of remote support during an online forum. Roughly three dozen participants were involved. The editors extracted the thoughts below from what four highly experienced consultants said.  

Consultant A completed a “desk review” of an instrument-transformer failure through remote support during the pandemic, which restricted travel. The owners provided onsite inspection observations and photographs. “We were able to coordinate activities by marking up photographs as supplied and requesting additional photographs of specific areas,” he said. This extended the analysis process, but considering three days of travel time would have been required, the overall process was faster than going to the site. Project cost was reduced since there were no travel expenses and the fee for travel time was eliminated.  

While larger projects will require onsite inspections, small, less involved, projects can be performed with the excellent communications available today. “We conducted daily conference calls,” Consultant A stated, “but did not use live video since a good internet connection was not available at this location. A live video inspection would have saved time. That should always be considered. Even when travel to the site is required, starting with remote inspections of the conditions will save time overall.”  

Consultant B said that Covid-19 travel restrictions made it necessary to conduct rotor-out inspections and interpret EMI tests remotely. With that experience in hand, he believes offsite support may be a promising alternative to onsite visits in the future—at least for some tasks. He thinks OEMs already are moving in this direction to keep personnel safe in less-secure areas of the world.  

Consultant B said that while a cell phone and camera are necessary for remote access, analytical success demands more sophisticated tools and proven solutions. Plus, power producers will have to adapt to not having the comfortable onsite presence of specialists. OEMs and third-party vendors will have to change as well, taking responsibilities without their physical presence in powerplants.  

Consultant C, a metallurgist, typically is called when something is broken and plant personnel want to know what’s wrong “with this thing.” His work almost always starts out with phone calls, written communication, and photos, lots of photos. The technical process for failure analysis has not changed much in the last half century, he said, but the way you get to a successful conclusion is different in some respects.  

What is different:

    • Access to good cameras. Plant personnel generally can take the photos required for diagnosis ad for explanation of the failure process. A bit of back-and-forth is involved, but it generally works.

    • Much better computers. We can now put very clear graphics on photos and figures to explain a failure process or damage process.

    • Remote meetings are possible and with a high-quality communications system for conducting meetings, effective tutorials can be presented on a given failure/damage condition. The big benefit is that people can leave the meeting with a clear an unambiguous understanding of what happened.

    • Power generation has transitioned from a utility-dominated business with deep experience to one with assets owned by utilities and independent power producers typically having minimal (or no) central-office technical support.

What is not different:

People on the user side are overloaded and have varying levels of experience—from high to low. This means consultants have to up their game to take less time to explain complicated processes.

Consultants must make sure that a clear explanation of the analysis process and the basis of the final answers/conclusions/recommendations gets to the right people in the organization.

Consultant D has been involved in generator inspections, failure investigations, and root-cause analyses (RCAs) for nearly half a century. He said that while performing his work remotely is possible in some cases, most engagements require an experienced eye onsite to gather important details often overlooked by the owner/operator.

To perform a proper RCA, for example, one must look at many details not available via a video inspection. Touch and smell are important, too, he noted. Plus, potential problems with language and terminology may impact communications given the international nature of power generation, and clarification may be necessary. Onsite meetings can help in this regard. Remote review of operating data is possible—provided you trust the accuracy of monitoring equipment. You might not have the necessary confidence unless you had eyes on the instrumentation.

When a generator fails, he continued, “what I hear from an initial phone call and photos usually is well off-base with respect to determining the problem and the solution.” A rule of thumb: A good failure investigation requires an extensive onsite inspection, possibly taking a day’s time, to fully assess the failure and the associated unit condition.

A thorough inspection also is likely to find other issues. An example this consultant gave: While investigating a stator winding failure, you might expect to find additional stator problems, rotor problems, air-gap problems, frozen radial dowels, surge-ring cracks, and who knows what else. A video would fall short in fulfilling this mission.

Regarding testing, Consultant D said, “I have given explicit detailed testing procedures via email and phone and received strange results. Further discussions over a month-long period finally proved the directions were not followed and the test invalid.”

On the topic of “becoming a generator expert” the consultant stressed the value of formal education, logical thinking, an innate and high degree of common sense, life-long dedication, and a love of the work. A degree in power engineering, Master’s preferred, is the ideal foundation. No matter how much on-the-job training one has, he continued, knowing power basics, symmetrical components, machine design, dynamics, forces, thermodynamics, basic chemistry, etc, is crucial in developing first-class expertise. It allows one to fit together the pieces of the puzzle. 

Posted in 7F Users Group | Comments Off on Commentary: The value of remote technical support during generator inspections, maintenance

Working safely in a powerplant with a medical implant

By some counts, says James E Timperley of J E Timperley Consulting LLC, over 300,000 electronic medical devices—such a pacemakers, defibrillators, cochlear, and neurostimulators—are implanted in Americans annually. Millions of these appliances are in service, covering all age groups in today’s population. This means that perhaps 1% of all people entering a powerplant may have some kind of electronic medical device. Providing a safe working environment for these individuals is more important than ever.

Electrical interference can pose a serious problem: It can disable any of these electronic devices. This danger can be from high-voltage electric fields, as in a switchyard, or high magnetic fields near large generators, bus systems, and/or transformers. Plant personnel normally are protected against dangerously high voltages by secure fences or metal structures.

However, high magnetic fields are another matter. Signage warning to maintain a safe distance when a microwave oven is operating has been standard for decades. Similar signage is needed for protection of people working in generating stations—including staff, contractors, and visitors. But this is an often-overlooked precaution where high 60-Hz magnetic fields are present. Such signage could be similar to the high sound-level warnings in locations where double hearing protection is required.

There are several suppliers of medical appliances. The inherent sensitivity of these devices to high electric or magnetic fields varies widely, and how a doctor programs a specific device also influences it sensitivity to outside influences. Only a physician and the device manufacturer can provide specific guidance for maximum field safety limits for each appliance.

An internet search for work-related safety protocols provides little useful information about the industrial work environment. Online information discusses warnings about exposure for a variety of commercial products—such as metal detectors, cell phones, 2-way radios, portable generators, arc welding equipment, gasoline ignition systems, electric fences, and medical procedures. There is almost no information available on the strong power-frequency electric or magnetic fields present in powerplants.

Most modern generating stations have meal-clad electrical equipment. This greatly reduces external electric (E) fields. The magnetic (B or H) field also is reduced by the metal, but penetration of these enclosures by high magnetic fields still can be a problem. Electric current of 5000 amps or higher usually poses a risk, and most powerplants will have current of this magnitude on the main bus, the auxiliary bus, near the transformers, and/or near the switchgear. All these locations easily can have extremely high gauss readings.

Measurement of magnetic fields must be conducted in the specific plant and plant environment where a worker or visitor may be exposed (photos). Contractors are available to conduct such surveys, but they must be accompanied by plant staff with an understanding of the equipment. The load when readings are collected must be recorded. Preferably, the survey will be taken at or near maximum load. In general, a high reading is considered to be 1 gauss or more.

In sum, a magnetic-field survey of a plant is not difficult to perform. With accurate measurements, and proper interpretation, areas of high magnetic fields can be determined. These areas then can be properly posted with appropriate signage.

In order for everyone onsite to be properly informed, it is strongly recommended that the high electric and magnetic fields, and the posted signage, be a topic included in the safety meetings conducted for all plant visitors. These precautions may prevent a serious medical emergency to personnel served by any of these medical devices.

Posted in 7F Users Group | Comments Off on Working safely in a powerplant with a medical implant

7F Digital Conference: Week 1 user sessions recapped here

Week One review. What follows are summaries of user presentations from last Tuesday and Wednesday. They illustrate the value of participation in the 7F Users Group’s virtual conference and next year’s F2F in St. Louis. To dig deeper, speaker PowerPoints will soon be available on the Power Users website to registered owner/operators. Registration is easy if you don’t already have a “library card.”

DAY 1: SAFETY AND COMBUSTION

Tuesday’s Safety Session, chaired by Dominion’s Chuck Spanos, followed introductory remarks by the 2020 Steering Committee Chair Matt Dineen of Duke Energy. Presentations addressed two of the industry’s hottest safety topics: Hex chrome and Covid-19 mitigation.

Hex chrome: You may be aware of it but how much do you really know?

The well-organized hex-chrome presentation is ideal for a lunch-and-learn session in the plant break room to be sure all personnel are on the same page with regard to this issue. It begins with a review of the health effects associated with exposure and provides guidance on exposure limits. Control measures to protect workers—respirators, protective clothing, increased ventilation, adjustments in the way a task is performed, etc—follow.

Cleaning methods are an important part of the presentation. Surfaces contaminated with hex chrome typically must be cleaned by HEPA-filter-equipped vacuums or by wet methods, such as wet sweeping or wet scrubbing. GE does not recommend use of dry methods for contaminant removal—especially wire brushing and compressed air—because they may cause the residue to become airborne. Also, waste material or debris contaminated with hex chrome must be collected and disposed of in sealed, impermeable bags or other closed, impermeable containers.

The OEM’s Product Service Safety Bulletin (PSSB) 20180709A-R4 and OSHA 3373 were recommended information resources. The first alerts against the use of anti-seize compounds that contain calcium and have the potential to result in the formation of hex chrome when applied to chromium-containing materials and exposed to elevated temperatures. The anti-seize compounds recommended for Frame 6, 7, and 9 gas turbines are Kluber paste HEL 46-4500 and Bonderite L-GP GP460.

The speaker said he was not aware of any reported hospitalizations tied to hex-chrome exposure, which is not characterized by an “acute” attack. However, health-related effects could show up years later. A person wouldn’t necessarily know if he or she was contaminated by hex chrome or inadvertently ingested it. Those users with a nuclear background might see similarities with inadvertent exposure to radioactive material.

Covid-19: Is there anything else we should know, except accurate facts?

The speaker developed slides on what has been reported to date: symptoms, groups at high risk for severe illness, precautions, contact guidance, and employee protection. Nothing new here, and to the speaker’s credit, he didn’t spend valuable time rehashing this material. Instead he focused on a so-called outage planning heat map and changes his colleagues might consider to their outage execution plans for mitigating exposure. 

The heat map described in the presentation and available to you on the Power Users website identifies “at-risk” outages and mitigations and the value of holding regular meetings to update outage plans.

Lessons learned during recent outages suggested the following changes to consider regarding outage execution to avoid exposure:

    • Segregate shift teams. Use phone or other digital means to communicate during shift turnovers. Provide a separate trailer for each shift.

    • Maintain social distancing during morning toolbox talks and move them outside (weather permitting). Strive to conduct meetings in 15 minutes or less.

    • Eliminate weekly group safety meetings; move them online if need be.

    • Schedule breaks in a manner to minimize personnel contact.

    • Organize work on the deck plates so only necessary personnel are present and try to maintain the suggested 6-ft distancing to the degree possible. If a “safe” distance cannot be maintained, issue additional PPE to compensate.

    • Limit one person per row of seats in company vehicles.

    • Stress increased personal hygiene. Add hand-wash stations and increase cleaning frequencies in common areas as necessary to achieve goals.

    • Monitor the temperatures of workers as they enter the site.

    • Be aware of the increased potential for heat-related stress created by wearing extra PPE.

Perhaps the most important lesson learned: Day-to-day productivity has not been impacted significantly by implementation of the above rules. The biggest concern for anyone with outage responsibility: The chance of an entire job being shut down if someone in the workforce were to test positive for Covid-19. Be vigilant, maintain strict adherence to the health aspects of your outage plan.

FlameTop 3.0: A project update

The first presentation in the Combustion Session, chaired by John Rogers of SRP, reviewed one user’s experience with FlameTop 3.0™, which combines the performance improvements offered by PSM’s Flamesheet and G-Top 3.0 products. The 2 × 1 cogen plant so equipped is powered by unflared 7241 7FAs.

The shortlist of Flamesheet performance goals/results:

    • Confirmed: Turndown to 50% output while maintaining permitted NOx and CO emissions of less than 9 ppm each; achieved turndown to 40% output.

    • Confirmed: Less than 5 ppm NOx at 40% output, less than 7 ppm at full load.

    • Confirmed: Less than 9 ppm CO at 40% output, about 1 ppm at full load.

    • Confirmed: Efficiency equal to or better than gas-turbine efficiency prior to upgrade.

    • Confirmed: Efficiency at 50% load less than 130% of the full-load efficiency; less than 127% achieved.

    • Confirmed: Elimination of visible emissions on startup.

The shortlist of G-Top 3.0 performance goals/results:

    • Confirmed: Maintained all Flamesheet achievements.

    • Confirmed: Increased gas-turbine output by 5.79%.

    • Confirmed: Decreased unit heat rate by 1.71%.

    • Confirmed: Eliminated seasonal tuning.

    • Evaluating: Longer maintenance intervals made possible by different modes of operation.

After FlameTop 3.0 installation, the plant experienced several engine trips triggered by the flashback protection system. Suspected issue: Increased sensitivity to fuel-gas-skid condensate formation leading to autoignition. Combustor mods implemented in November 2019 to eliminate the problem were successful. FlameTop 3.0 was said to have allowed the cogen facility to better align with the host site’s steam and electrical demands. Satisfied customer: The second unit will be converted to FlameTop 3.0 in the fall during a hot-gas-path inspection.

FlameTop experience had been shared earlier with 7F users by Lightstone Generation’s Lawrenceburg Power. 

Lessons learned during commissioning of 7FA.04 dual-fuel units with DLN 2.6+

Three valuable experiences were shared by a user who was involved in the commissioning of two 7FA.04-powered 1 × 1 combined cycles early this year. Both units are equipped for dual-fuel firing with DLN 2.6+ combustors, and have bypass dampers. Fired hours on the units just ahead of the meeting were 3300 (68 starts) and 3100 (95 starts). Run profile: Baseload with automatic generation control (load following).

The speaker urged attendees planning a commissioning to understand how their unit’s warranty handles newly issued TILs (Technical Information Letters) to save aggravation and money down the road. His units were able to incorporate most TILs during the construction and commissioning process. However, some TILs were assigned after the units were received and would have required significant disassembly for compliance. Suggested work was postponed for a future outage.

The need to verify that no foreign materials remain in the machine when it is buttoned-up for operation was stressed. The speaker said, “The seemingly most-simple task can have severe consequences if not performed with rigor.”

During inlet-guide-vane calibrations in preparation for performance testing of one unit, damage was found on several R0 blades. Inspection revealed that a ball of duct tape had been left in the inlet and was ingested. A dozen blades were damaged and blended; there were no vibration issues afterwards. However, tape residue had reached the seventh stage and was not completely removed by water washing.

Commissioning of one unit on oil proved difficult. It could not be tuned when in the liquid-fuel mode because of high exhaust spreads. Note that these units are equipped with pressure-atomized liquid-fuel systems (acronym is XAA), which eliminate the need for atomizing air. No coking has been experienced, but operating time on oil was less than about 50 hours for each gas turbine. The user said more run time was required to fully evaluate the reliability of the liquid fuel system.

XAA is an emulsification system that mixes liquid fuel and water ahead of the end cover. The speaker reported that water injection starts at about 40 MW following a pushbutton start on oil only. Water is used to flush the fuel system after burning oil.

Learn how GE engineers found and eliminated the gremlins responsible for the operational problem by accessing the presentation on the Power Users website. To learn more about this system, request GEK 121513 from the OEM.

Using polling results to guide open discussion sessions

The 7F was the first user organization to use electronic polling as a method for guiding and contributing to topical discussions, according to the editors. Tenaska’s Christa Warren, the 7F Users Group’s vice chair for 2020 makes liberal use of polling in her interactions with the group during annual meetings. She led a brief discussion on a couple of combustion issues that appeared on agendas of previous meetings to see if there was anything new to talk about.

One subject was fuel-nozzle damage, which had been experienced by 56% of the attendees. As for cause, 28% of the respondents named fuel contamination; “other” and “unknown” received 64% of the votes. Warren put up photos of fuel-nozzle damage on the screen to get some feedback. One user said that at least some of the damage shown likely came from burning because the flame was not detached from the nozzle like it should be. Another offered that proper use of atomizing air is critical to nozzle damage control. Yet another said most damage he has seen was on PM2 and PM3 nozzles. High NOx and ammonia were said to be key indicators of fuel-nozzle damage.

Another topic was the adverse impact of cold weather on operability. Here are the questions Warren asked the group:

    • Do you have autotune installed? More than three-quarters (78%) of the responding attendees said “yes,” with 63% of the users equipped with a GE system.

    • Do you have issues during cold weather with high-dynamics alarms that require an operator response? Answers: No, 45%; rarely, 41%; frequently, 14%.

One comment was that model-based control works well, except possibly in cold weather. Suggestion for those with issues: Operator intervention to possibly change NOx, for example.

DAY 2: COMPRESSOR AND AUXILIARIES

The Compressor Session, with Warren at the helm, opened Day Two of the user presentations. Topics were Row 1 damage from inlet FOD and the value of pressure-washing inlet guide vanes.

Inlet-duct liner-attachment failure releases heavy vinyl material that damages R1 blades

This presentation should be reviewed by personnel at any plant with an inlet duct, or inlet silencers, manufactured by J&G Steel. The speaker reported on his plant’s issues linked to manufacturing errors made by the vendor since a 2016 borescope inspection found insulation in the cooling passage of a first-stage nozzle. TIL-1995 (April 2016), “Silencer/Inlet Bleed Heat Duct Inspection,” was the first response by the OEM; TIL 2173 (December 2019), “Inlet Silencer Panel Inspection,” was the second.

The CliffsNotes version of this presentation is that pieces of the vinyl moisture/noise barrier, located between the inner liner and the mineral-wool insulation/outer wall of the inlet duct, were released when stitch welds failed. The welds, which anchored the inner liner to support plates for the insulation system, were ground flat in error, weakening those joints. Vibration likely caused the weakened welds to fail.

The speaker said the damage to the Row 1 compressor blades resembled ice damage. All first-stage blades were removed, without pulling the rotor. Two of the blades with bent corners were blended; three blades with more substantial damage were replaced.

Pressure-wash IGVs to restore efficiency

This presenter’s plant pressure-washes the bellmouths and inlet guide vanes of its gas-turbine compressors every quarter—sometimes more frequently if a drop in performance so dictates. The pressure-wash idea was pursued after a roll of paper towels used for cleaning the IGVs was left inside the machine prior to restart and caused considerable damage.

The gas turbines operate in a challenging process environment and foul quickly. The pressure washer is operated by plant personnel at 3200 psig; the nozzle is held 2 to 3 in. from the vane surface. A typical cleaning procedure is as follows:

    • With IGVs in the closed position, saturate the vanes and bellmouth with water.

    • Coat the vanes and bellmouth with ZOK [link] at full concentration. A manual pump-up sprayer is ideal for this purpose.

    • Allow the ZOK to soak in and loosen the debris for about 10 minutes. Important not to let the ZOK fully dry because that would make it much harder to remove.

    • Pressure-wash the vanes and bellmouth with water.

    • Open the IGVs and repeat the process. An added benefit of opening the IGVs is that you clean the first two or three compressor stages as well.

    • Offline water-wash the entire compressor before returning the unit to service.

At this plant, pressure-washing the IGVs alone boosts output of the 7FA.03 gas turbine by 4 to 6 MW. These numbers increase, of course, if a full compressor water wash follows the pressure-wash step. Plant personnel can complete a pressure wash in less than two hours. A full water wash and pressure wash takes about eight hours.

Readers considering a pressure wash will benefit from reviewing the presentation, which offers valuable details and safety hints.

Get more than a glimpse into battery storage/GT peaker integration design

If you want to stay on the cutting edge of gas-turbine facility design, access this presentation on grid-scale battery energy storage systems (BESS), made Wednesday, June 17, during the first segment of the Auxiliaries Session, chaired by Bryan Graham. Owner/operators are getting acquainted with a variety of grid-scale BESSs. But one thing’s for sure: Many of them will be destined for existing gas-turbine and combined-cycle facilities.

This presentation reviews a 7.4-MWh lithium-ion BESS designed to black start a 2001-vintage 150-MW 7F.03 simple-cycle gas turbine/generator. The batteries are specified for a 10-yr life based on one charge/discharge cycle per month. Note that black-start equipment often is started for test purposes more than for an actual black start.

Replete with extensive electrical one-line and circuit diagrams, the slides should be especially attractive to electrical engineers. Other users will take note of the detailed sequence-of-events descriptions for how the BESS and gas turbine (with an upgraded load commutated inverter, LCI) work together during synchronization and startup.

Grid-scale battery geeks will benefit by learning about the extensive BESS fire suppression system, which is comprised of three major subsystems:

    • An extensive lithium-ion gas detection monitoring array in each of the battery enclosures. Each enclosure contains 21 individual sensors connected up into two controllers.

    • A spray suppression system inside the enclosures which deploys a fluid mixture of 30% inert gas and 70% potassium particulate.

    • A water spray nozzle system in between the enclosure rows to prevent heat transfer from one enclosure to others across the walkway.

Battery enclosure temperature control is critical for BESS systems; each enclosure is equipped with two 100% redundant 6-ton HVAC units comprised of a 13,000- to 67,000-Btu/hr chiller, 15-kW heater, and variable-speed blower operating between 850 and 1700 cfm.

Startup posed several challenges and lessons for others. For example, the harmonic filters were designed based on the original LCI design data. However, the live data captured during unit start revealed the noise was much worse. So, the harmonic filter was redesigned for the actual data, which doubled its size.

The black-start procedure required many revisions after several failed start attempts caused by logic oversights, wiring and hardware issues, etc. However, after the first successful startup, everyone on the project was surprised that the battery had still retained 94% state of charge, a key measure of the depth of the cycle, battery life, and performance.

Lube-oil conditioner upgrade

There have been significant improvements in lube-oil polishing technology since this baseload 1 × 1 STAG 107FA plant began commercial operation at the end of 1997. Its lube-oil system has a single 10,000-gal tank serving both the gas and steam turbines.

A portable oil conditioning unit purchased in 2000 had reached end-of-life and plant personnel jumped at the opportunity to purchase a modern system equipped with the latest filtration capabilities and instrumentation to dramatically reduce both particulate count and moisture content.

A review of this presentation is a good first step for those dissatisfied with the performance of their lube-oil conditioning system.  

Posted in 7F Users Group | Comments Off on 7F Digital Conference: Week 1 user sessions recapped here