WESTERN TURBINE USERS

The gold standard in aero meetings

Jon Kimble, president, Western Turbine Users Inc (WTUI), wrapped-up the organization’s 21st Annual Conference and Exhibition in Palm Springs last spring by summarizing the meeting’s highlights and announcing that the 2012 conference will be held at the Pasadena Conference Center next March 18-21. 

The Palm Springs meeting was a big success by any measure. There were over 900 participants; more than 140 companies represented at the vendor fair; a robust technical program; vibrant interactive discussions at the LM2500, LM5000, LM6000, andLMS100 breakout sessions; and fun social events.

   Informal interviews with owner/operators in the hall all were positive. Most focused on the excellent content of the breakout sessions and the value of ensuing discussion forums. Everyone had compliments for the organization’s all-volunteer corps of officers, directors, and breakout-session chairs (Callout 1).

1. Western Turbine officers, directors


 

     What WTUI seems to do better than any other user group is train attendees to operate, inspect, and maintain gas turbines—in this case, GE Energy’s Land and Marine engines. “Lessons” are conducted primarily by the five depots licensed by the OEM to inspect and repair these gas turbines: TransCanada Turbines (TCT), Calgary; MTU Maintenance Berlin-

Brandenburg GmbH, Ludwigsfelde,Germany; Air New Zealand Gas Turbines (ANZ),Auckland; Avio SpA,Rivalta de Torno,Italy, and IHI Corp,Tokyo.

   In terms of deliverables, each registered owner/operator receives a notebook which may have 100 slides—sometimes more—developed by the depots for the brakeout section  the user selected. A typical depot notebook contains the following material:

  • Engine fleet statistics, manuals, and definitions.
  • A review of recent service bulletins (SB) and service letters (SL) issued by the OEM.
  • A summary of depot findings since the last meeting. This information is invaluable for anyone planning an outage.
  • Causes of performance loss and how to correct them.
  • Critical parts life management.
  • Engine preservation, handling, and transportation.
  • Expectations with regard to maintenance intervals.

   Session book in hand, it’s easy to follow the presentations and jot down additional notes where necessary. And if you step out of the room to take an important call, WTUI has you covered. CEO Sal DellaVilla and his colleagues at Strategic Power Systems Inc, Charlotte, attend every session to take notes which then are posted in the user-only portion of www.wtui.com. SPS’s notes form the basis for the summaries of the 2011 breakout sessions included in this report.

   President Kimble told the editors that the 2012 conference program would be similar in arrangement to this year’s. The meeting will officially start on Monday morning and run until noonWednesday. Unofficially, the event begins early Sunday morning when the golfers tee off for the annual Western Turbine tournament. Tennis competition is scheduled to start aroundnoon.

   WTUI conducts one or more orientation sessions for newcomers; these are held after Sunday’s sporting events. The LM engine familiarization workshop, which runs for about an hour and a half in the late afternoon, always gets high marks from newcomers. Typically, one-third of the user attendees at the annual meeting are first-timers, many unfamiliar with one or more engines supported by the group.  The crash course, taught this year by Bob Boozer of PPL University Park LLC, is excellent preparation for the breakout sessions beginning Monday morning. Acronyms used in casual conversation by this group are defined below.

2. Acronyms to remember 

   The engine familiarization workshop was followed by an ORAP® new user orientation program conducted by Lynne Bellizzi of SPS. She explained that the Operational Reliability Analysis Program is an automated system for monitoring and reporting RAM-D (reliability, availability, maintainability, durability) data for gas and steam turbines worldwide.

   SPS is an unbiased third party that provides turbine users the means to benchmark their assets against the fleet regarding inspection intervals, time-to-repair statistics, component failure rates, best practices, etc. Unit-specific information also is provided to owner/operators. SPS works 

closely with WTUI to support LM users.

   Tuesday afternoon typically is reserved for one last visit to the exhibit hall and special technical presentations by industry consultants and equipment suppliers. Topics are carefully selected by the WTUI officers and board of directors.

   Kimble reminded that the group’s mission is to provide a forum for the exchange of technical, operations, and maintenance information and experience, with the goal of improving the reliability and profitability of generating facilities powered by GE aeros.

   LM users who have never attended a WTUI conference probably cannot imagine the value associated with participation. It is the rare attendee who returns to his or her plant without an idea for saving several thousand dollars in maintenance and/or operations. Comradery is a defining characteristic of this group, enabling the helpful exchange among delegates.

Monday Morning

WTUI XXI officially began with Chairman Kimble’s welcome, recognition of directors, officers, and session chairs, Treasurer Wayne Kawamoto’s annual financial report, and a review of the conference agenda.

The depots

Kimble moved quickly through the boilerplate and introduced the depots, each one making a short presentation. Here’s a summary of what was said:

   AirNew Zealand. Richard Ison,  who recently stepped up to the executive suite from his position as general manager ofANZGas Turbines, opened by offering his company’s experience to assist owner/operators challenged by the loss of key personnel through retirements. He then announced that John Callesen, well known to LM veterans, would replace him as GM under a new company logo.

   The big news was that ANZGT had formed a partnership with Consolidated Asset Management Services (CAMS) and Redwood II Operating Co LLC to provide enhanced inspection and repair services to North American customers. ANZGT Field Services (www.anzgtfs.com),Bakersfield,Calif, headed by GM Frank Oldread, a former WTUI director, offers the following:

  • All GEK Level 1 and 2 maintenance—including laser alignment, trim balance of engines and generators, borescope inspections, etc.
  • Semi-annual inspections, including gas generator and package support systems.
  • Depot repair and overhaul support for gas generators and power turbines.
  • Due diligence support, including physical condition, SB compliance, and spare-parts inventory assessments.

   IHI Corp. A company spokesperson opened by thanking the world community for its support during the tsunami, adding that senior management was unable to participate in this year’s conference because of commitments at home to assist in the recovery.

   Eiji Okuyama, manager of the sales and marketing department in IHI’s Power Systems Div, was promoted to VP of US activities which include a business office in New York City; the Los Angeles Service Center operating under Ken Udea, stationed engineer; and a recently announced affiliation with Reed Services of Wyoming Inc, perhaps best known for its inspections of LM engines.

   A promotional video discussed the company’s shop capabilities and offered short presentations by overhaul foremen and a customer testimonial. The company has an agreement with the OEM to package LM-series gas turbines and to date has provided more than 80 units worldwide. IHI has a Level 4 depot qualified to service LM2500 and LM6000 engines.

    TransCanada Turbines.  Dale Goehring, director of projects updated the group on the company’s facilities, which now include a Level 4 depot inCalgaryand overhaul centers in Houston, Bakersfield, Calif, Syracuse, NY, and Glasgow, Scotland. TCT’s East Windsor (Conn) and Liverpool (England) shops moved to more spacious quarters in Syracuse and Glasgow, respectively. Both locations have Level 2 tooling and spare-parts inventory.

   Goehring stressed TCT’s commitment to quality and safety excellence (employees have signed personal-safety contracts). He said the company had three dozen experienced service personnel in the field worldwide.

   MTU Maintenance.  The group was told the company had a busy year in 2010: Experienced field service personnel were hired, a shop was opened in New Braunfels, Tex, and test cells were upgraded. New Braunfels is equipped to perform Level 2 overhauls on LM6000s and LM2500s; the company has a Level 4 depot for LM2500, LM2500+, and LM6000 in Germany. A new service center is under construction inThailand. MTU is upgrading its inspection capabilities and is offering modifications to provide water injection for NOx control.

    Avio  is equipped to overhaul and repair LM2500, LM6000, andLMS100 engines and also to manufacture several components for the OEM inBrindisi—including complete IP- and power-turbine modules for theLMS100.

   In the last few years, the company has installed new equipment to expand its special repair capabilities. Avio is especially proud of its test cells and work areas for component cleaning, surface treatments, and nondestructive examination.

OEM aggressively pursues aftermarket  

Dave VanderShee provided an overview of GE Aero Energy’s efforts to upgrade its service and overhaul capabilities for the LM2500, LM5000, and LM6000 engines—a market that the OEM shares with both licensed and unlicensed depots.

   Mentioned were the development of Level 2 service centers in Kaluga, Russia, Lincoln, UK, and Perth, Australia (2012); the first Level 4 facility in Latin America, scheduled for ribbon-cutting in September 2011; expansion of test-cell capabilities in Houston; and a build-out of the monitoring and diagnostic center serving the aero community.

   VanderShee said there are more than 900 LM engines in North Americaand that the company had four-score lease engines available. He added that the company was approaching 300 service reps worldwide, 70 of those in the US and Canada.

LM2500+G4 DLE

The final presentation before coffee and the engine breakout sessions was by Jack Kelly, project manager for Jacobs Energy & Power Solutions. He discussed design details on what Kelly said was the world’s first 60-Hz LM2500+G4 DLE installation—at the Univ of Texas’ 120-MW Austin powerplant (Figs 1-3).  

   Jacobs was the owner’s engineer on the project, which included demolishing and removing a gas turbine/HRSG power train installed in 1965 to make room for the new cogen unit. The heat-recovery steam generator behind the G4 was designed and built by Express Integrated Technologies LLC,Tulsa.

   The LM2500+G4, commissioned at the end of 2009, operates about six months of the year. A sister unit—G4 with Express HRSG—was in the final stages of construction at nearby Texas A&M at the time of the meeting. The 32.5-MW (net) G4 was the “right-size” generating unit for theAustincampus.  The university’s relatively low wintertime electric requirement (average annual load is about 41 MW) is not a good fit for the generating facility’s other gas turbine, rated 45 MW. 

   Kelly discussed the models used and optimization programs run to assure that the new gas turbine and its HRSG would satisfy campus electrical and thermal requirements as intended.

   Heat rate for the G4 is just under 9100 Btu/kWh (LHV). Maximum emissions over the temperature range of 10F to 100F: 25 ppmvd for both NOx and CO (corrected to 15% O2) at loads down to 75% of the turbine’s full-load rating.

   Kelly reported only two issues of significance during the first few months of operation:

  • Interposing relays between the Woodward MicroNet™ Plus digital control system and the fuel control system failed several times causing multiple trips.
  • Spiked “high oil” level signals from the turbine and generator lube-oil tank level transmitters caused four trips—two from each transmitter.

   Investigation of the first problem revealed that issues with the interposing relays occurred when the voltage dropped below the 10 V dc specified. The Woodward MicroNet system did not require interposing relays, so they were removed; no failures were reported during trial runs.

   Regarding the second issue, the trips appeared to result from spikes in signal levels rather than from a true rising level. This was verified by slowing the sample time for the level sensors. Further research revealed a misapplication of the sensors selected. Investigators learned that any debris or moisture contacting the sensors could cause an output spike. Solution: All oil-level indicators were replaced with guided-wave radar level transmitters.

Special presentations

No Western Turbine conference program would be complete without special presentations that go beyond the scope of the engine breakout sessions. The first of these was by Houston-based energy consultant Mark Axford (Axford Consulting LP), who updated attendees on “the state of the industry” Tuesday morning.

Market outlook

Axford began by recalling his predictions for 2010 orders made a year earlier:

Total capacity of frames and aeros booked in 2010 for installation in the US would be down 9% compared to 2009, he had said. The market analyst was close, but too optimistic. Sales were off 17%.

  • Worldwide, he predicted, the capacity ordered would be up 7% year over year. Axford was real close: Bookings were up 7.5%.

   He is optimistic about 2011. Axford’s crystal ball suggests a 25% increase inUSsales of gas turbines rated 10 MW and higher (capacity basis) over 2010. His confidence is buoyed by two facts: Sales in 2010 were about 25% below pre-recession activity, and GT orders have never fallen in three consecutive years—both 2009 and 2010 were down year over year. Worldwide, he predicts 15% growth. Note that Axford’s expectations do not include any possible boost in gas-turbine bookings because of looming nuclear concerns.

   The electric power industry has experienced several boom-and-bust cycles in its history; the turbine OEMs have also. Example: GE Energy captured 100% (1378 MW) of theUSaero business up for grabs in 2010; a year earlier, it finished in second place behind Rolls Royce with 32% of the orders. Units ordered last year: sevenLMS100s, six LM6000PCs, two LM6000PFs, one LM2500PE, seven LM2500+G4s.

   Aero GT orders from outside theUSin 2010 totaled 5476 MW. Rolls Royce and Pratt & Whitney divided 12% of the market; GE grabbed the remainder. The LM2500 was the most popular engine, taking 48% of worldwide orders by capacity.

   Latin America was the most active region, capturing 27% of the capacity; North America took 21%, followed by Australia (17%), Asia (12%), Europe and Middle East (10% each), and Africa (3%).

   Orders for frame engines in North America totaled 4628 MW last year, with Siemens capturing 71% of the business (two SGT-800s, a dozen 501Fs, three 501H); GE got the rest on sales of only seven 7FAs (six of those to Mexico’s CFE) and one 7EA.

Fleet performance update

Strategic Power Systems’ Tom Christiansen treated theWTUI membership to an analysis of trends in gas-turbine service factors from 1995 through 2010 which reflected increasing cyclic operation of aeroderivative engines installed inNorth AmericaandWestern Europe.

   ForNorth America, he said, the service factor for all aeros in the company’s ORAP® database decreased from an average of 62% during 1996-2000 to 37% in 2006-2010. Average engine starts during the two periods went from 77 to 100.

   He then compared the preceding “all-aeros” numbers to those for the LM engines operated by the Western Turbine members. LM machines recorded an 83% service factor during 1996-2000 and 42% in 2006-2010. Average engine starts for the two periods rose from 77 to 132.

   InEurope, the average service factor (starts) for aeros was 76% (47) during 1996-2000 and 58% (70) in 2006-2010.

   Christiansen also compared reliability and availability figures over time for three engine classes: aero, E-class, and F-class engines. That information is available in “Changing duty cycles and gas turbine reliability—a look back,” published in the 1Q/2011 issue (access article at www.ccj-online.com).

Technical presentations

Tuesday afternoon there were six technical presentations—three conducted in parallel in each of two one-hour time slots beginning at 3 pmwhen the exhibit hall closed. Thumbnails of those presentations follow. The complete presentations are available at www.wtui.com for active Western Turbine members only. Membership in this group offers tremendous value to owner/operators of GE aeros; consider joining today if you haven’t already done so.

Turbine package design, Toshiaki Sato, Power Systems Div, IHI Corp. 

   Sato reviewed the company’s turbine-package design process, covering such critical systems and equipment as the following:

  • Air inlet system.
  • Heat rejection and cooling.
  • Fuel system.
  • NOx water system.
  • Lube oil system.
  • Bleed air extraction.
  • Starting system.
  • Accessory drive.
  • Electrical system.

   Special attention was given to the air inlet, fuel, and lube-oil systems. Sato explained that the air inlet system consists of pre, main, and HEPA filters in series and had an anti-icing system. The prefilter is rated MERV 7-8 (G4), the main filter MERV 15, and HEPA capable of removing 99.95% of particulates 0.3 micron and larger. While HEPA does not have widespread support in theUS—at least not yet—80% of Japanese gas turbines were said to have them.

   The liquid-fuel, NOx-water, and lube-oil systems were explained by way of flow diagrams. A checklist of possible features to consider for your next lube-oil system was included.

   NERC regulatory update, Chris Siplin, Wood Group Power Plant Services. 

   Siplin has been keeping Western Turbine Users informed about NERC regulations for the past few years. As his company’s regulatory compliance manager, he must keep up to date on all aspects of NERC requirements. Siplin spent about half his time at the podium discussing NERC’s compliance behaviors and the penalties for not following regulations to the letter.

   Bear in mind that fines can be considerable—possibly even exceeding $1 million. Fines are determined, in part, by the level of infraction. For example, a Level 1 infraction relates to lack of detail, missing dates, etc; Level 2, lack of training, uncontrolled documents; Level 3, overlooked requirements, inconsistent history of documentation; Level 4, disregarding requirements, missing documents.

   Key actions to avoiding penalties include the following:

  • Appoint a NERC subject-matter expert.
  • Implement a thorough NERC program.
  • Involve executive management.
  • Train personnel thoroughly.
  • Retain electronic and hard copies of controlled documents (central filing system).
  • Acknowledge and respond to all NERC requests in a timely manner.
  • Self-certify.
  • Self-report when necessary. Get the corporate legal team involved.
  • Don’t submit more information than is required.
  • If documents are referenced—such as performance tests—provide them and file them.
  • All reliability standards are applicable even if they do not apply to your site.
  • Have the facility manager lead the audit with support from your NERC expert.

   Cycles tracking and critical-parts management experience. The term “cycles tracking” got special emphasis in the plant manager’s lexicon about seven years ago when the OEM assigned life limits to hot parts and required owner/operators to track engine cycles—specifically normal start/stop, trip from load, and partial cycles (step change). This followed a somewhat similar directive from the FAA for on-wing engines.

   Goal: To achieve the highest level of operational safety by assuring that design-life limits of critical parts—rotors and disks, for example—are not exceeded. The editors were told by one attendee that the requirement to track cycles is specified in engine O&M manuals. Some plants in the fleet are tracking cycles, but others still have no system in place for doing so.

   A panel was put in place byWTUI to find out how LM owner/operators were approaching the challenge. There were three participants: Ed Jackson of Missouri River Energy Services, Chris Heiberger of Wellhead Services Inc, and Dan Dowler of Encana Corp.

   Each participant explained the system his plant had developed to track cycles. The approaches differed, but all three of the self-developed solutions achieved the objective by providing the information required. None of the panelists said his plant was replacing parts based on results, but it was obvious to one attendee with considerable knowledge on the subject that this was coming—sooner rather than later.

   The same expert, while commending the plants for their initiative, suggested that the individual approach does not meet the intent of the directive because it’s a fleet issue, not a customer issue. The proverbial fly-in-the-ointment is rotable parts. If the data have no pedigree, he said, you only will know the impact your operations have had on the lives of individual parts.

   A better approach, he continued, might be to have an industry-wide data acquisition and analysis service track parts from plant to plant, machine to machine, and through repair processes. The service provider would alert owner/operators when parts in their machines were approaching end of life.

   Engine/component repair services, Brian Hulse, Wood Group Pratt & Whitney. 

   If you were looking at the program and didn’t know the man, you might have thought his would be another “empty” slide show by a sales guy. No way. Hulse has user blood, although he earns his livelihood today as engineering and program development manager for the Jacksonvilleshop of Wood Group Pratt & Whitney Industrial Turbine Services LLC, an independent full-service depot serving the LM2500 community.

   Hulse was a user back in the early days of WTUI. You’ll find his name on the group’s Honor Roll recognizing the service of past and current officers and members of the Board of Directors. Sure he wants your business, but banging the drum and tooting the horn is not Hulse’s style. He would rather share his deep knowledge of LM engines and repair processes to help owner/operators make better buying decisions. And that’s exactly what he did for his time at the podium.

   Checklist 1: What to ask of the depot following a forced outage. A depot visit is either planned or not, Hulse began. When an engine is forced out of service, here are some of the things you might consider asking the shop to do:

  • Conduct an incoming engine test, if possible.
  • Do a forensic teardown if appropriate.
  • Gather and evaluate all available data.
  • Try to “box the problem” tightly to avoid work-scope creep.
  • Ask for an engineering report.
  • Discuss avoidance strategies with the depot to prevent recurrences, if appropriate.

   Checklist 2: Component repair considerations. Drivers for component repairs on any shop visit include structural defects, changes in critical dimensions (assembly or functional), and loss of coatings. Here’s how you might approach what to do:

  • Prioritization of repairs should be at the top of your list.
  • Fix or buy/barter new/repaired parts.
  • Check length and chord on compressor blades.
  • Use data gathered to identify and focus on weak areas.
  • Track your scrap! It may be repairable in the future, or have some other value.

   Checklist 3: What to consider before finalizing your plan for control system retrofits and upgrades. Nothing lasts forever, especially control systems. Ten years after COD, for example, your control system may no longer be supported by the OEM or you may have interface issues. Or, perhaps, increased functionality is necessary, or failure rates are unacceptable, or the gas turbine has been retasked or reconfigured. When evaluating retrofits and upgrades, ask yourself these questions:

  • How long has the equipment been available?
  • Where else is the equipment being used?
  • Will the supplier share a customer list?
  • What is the source of the “core” program?
  • What is the time-stamp accuracy of the “first-out” indication?
  • What is the historical and trending capacity?
  • Is there sufficient CPU capacity/speed for subroutine programming?
  • Is there room for I/O expansion?
  • Are the HMI controls logical and intuitive?
  • Can the program be tailored to the staff knowledge/skill level?
  • Is O&M training part of the package?
  • Can/will a full factory acceptance test be performed prior to implementation?
  • Will the system be fully documented?
  • Can staff make a reasonable array of program changes?

   Failure analysis, David Christie, IMR Test Labs. 

   Christie presented several case histories to illustrate how detailed analysis can identify the root cause of failure and help prevent a recurrence. He outlined the steps to take when preparing parts to submit for failure analysis and what information to provide. Finally, Christie described what to expect in a good failure-analysis report.

   The first failure he described occurred 10 years ago in a JT9D engine for a Boeing 747. A loud explosion and flames occurred shortly after takeoff but the engine was shut down and the flight continued to its destination.

   The uncontained failure was characterized by the fracture of an LP turbine disk (A286 austenitic superalloy) wherein the fifth-stage disk rim separated from the web, the LPT casing ruptured, and the cowling and outer casing were damaged. Foreign object damage was caused to the adjacent engine as well as to the airframe.

   Tear down by the engine manufacturer revealed 56 of 60 cooling-air holes covered with plasma-spray coating material (95Ni-5Al). The repair had been performed 1532 cycles/7357 hours prior to failure. Lack of cooling induced high thermal stresses in the radial direction and caused the disk rim temperature to increase by about 400F to 1265F. Metallurgical examinations were conducted by three independent parties and results were in agreement. Christie offered several photos of the failed wheel and photomicrographs to support the conclusions.

   Christie’s second case history concerned a bearing failure. A pump moving liquid butane sustained a fire and explosion at its motor. The fire burned for two hours before being extinguished using saltwater; the motor bearing and shaft had failed. The $64 question: What failed first—the shaft or the bearing? You might want to access the presentation at www.wtui.com and see if you can figure out the answer from the many photos offered—before reading the next paragraph.

   Investigators came to the following conclusions:

  • Bearings overheated locally because of friction (not because of fire).
  • Bearings likely suffered lubrication starvation.
  • The brass ball cage distorted and bearing balls moved out of position, thereby allowing the shaft to wobble, seize, twist, and finally fracture.
  • The pump seal was destroyed, allowing butane to leak out. Concurrently, the rotating shaft contacted shrouds, causing sparking and ignition.

   Failure analyses for bolts and a bull gear also are included in the presentation.

   Perhaps of greatest value to all who listened to Christie were his suggestions on what to do following an event requiring failure analysis. He recommended summarizing the event this way to assure understanding by the analysts assigned:

  • Describe the events as they unfolded, from before the failure up to packing the parts for shipment.
  • Provide detailed photography of the failure site and the current condition of parts. Include photos of normal equipment condition—both as assembled and individual parts.
  • Add any other information you or your team feels is relevant.

   Where to start: It’s important to follow safety and quality procedures “by the book,” Christie told the group. Document everything, he continued. Collect written observations from personnel in the area when the damage occurred—including operators. Contact the laboratory engaged to conduct the failure analysis to determine if photographs are sufficient or if an onsite exam might be warranted.

   Gathering of the bits and pieces brought these suggestions from the speaker:

  • Determine the identity of each piece and label it as it is removed from the scene.
  • Keep notes during any disassembly and provide photo documentation.
  • If corrosive material is on the pieces, rinse it off and dry the pieces with gentle compressed air or alternative.
  • Wrap sharp or delicate parts in lint-free cloth and bag each piece separately.
  • Avoid touching critical surfaces, particularly if corrosion/contamination is suspected.
  • Resist the urge to “fit the pieces back together.” This usually damages the fracture surfaces and compromises the analysis.
  • Obtain samples of relevant fluids—such as lubricants, pumped fluids, cooling water.

   Background information is a vital complement to the failure data. Here’s what you should provide investigators—at a minimum:

  • Operating time (hours; cycles if relevant).
  • Date of first commercial operation.
  • Operating conditions: temperatures, environment, type of operation (continuous, cyclic, etc), downtime conditions, operating speed (rpm), fuel type, lubrication schedule, etc. Include details of operating practices.
  • Maintenance and re-fit history—specifically, any recent work done on parts or the assembly, past or current maintenance issues, etc.
  • Materials data, specifications, and drawings for relevant parts and assemblies.
  • Contact information for parts suppliers and/or subcontractors.
  • Details on recent changes in operations and parts suppliers.

   Microfiltration of cooling-tower blowdown water in a ZLD application, George Davies IV, Turlock Irrigation District; Charles Cruz, PE, Separation Processes Inc; Donn Thomas and Ramraj Venkatadri, Pall Power Generation. 

   The focus of the presentation, reducing operating costs with improved reverse-osmosis (RO) pretreatment, is a valuable lesson learned but likely is of limited interest to LM users because their plants generally are not equipped with cooling towers and ZLD systems. In fact, the plant around which the case study was developed has frame engines. For a backgrounder on the 250-MW 2 x 1 combined cycle, access “A breed apart from the industry norm,” 4Q/2006, at www.ccj-online.com.

   The article describes the extensive zero-liquid-discharge system at theWalnutEnergyCenter, which helps in understanding where the microfiltration (MF) unit fits in the circuit. The issuesTurlockfaced with its five-year-old wastewater treatment system included the following:

  • Very frequent cleaning of RO membranes.
  • Frequent change-out of RO membranes.
  • Fouling or plugging of ion-exchange pretreatment equipment.

   Water quality was unacceptable for zeolite softeners and weak-acid cation softeners, in addition to the RO system. Problems were traced to unsatisfactory performance of the media filters installed with the ZLD system—including high turbidity and particle counts and an unacceptable silt density index (SDI).

   Pilot tests of an MF unit were conducted on media-filter effluent and directly on cooling-tower blowdown. Performance was best on the latter. Turbidity was consistently below 0.1 NTU; SDI improved from an SDI5 of 20 to an SDI15 of about 2.5.

   Removal of the three media filters (8.5 ft diam x 15 ft high), associated piping, and supports allowed the plant to shoehorn into the space created two standard Pall AP-6 MF units, a 35,000-gal MF feedwater tank, new waste sump for MF microscreen backwash, and MF unit drains. The retrofit project was accomplished with a 21-day shutdown—including demolition work, installation of new equipment, startup, and commissioning.

Exhibit hall

The editors talked to many company representatives during the three days the exhibit hall was open. The objective: Get the details on new products and services and learn about the issues equipment and services providers are seeing first-hand during plant visits. In the case of Western Turbine, the exhibition is particularly meaningful: Users get the details on the engine in the breakout sessions, but little else.

   The vendor fair is where they learn about all the services and auxiliary equipment required to make a plant operate safely, efficiently, and reliably, including: valves, generators, water treatment, heat-recovery steam generators, air filters, turbine inlet cooling alternatives, compressor cleaning, etc. Many ideas for improving the bottom line can be identified in the interviews summarized below.

   Double the life of LM2500HPTblades. 

   LM2500 Row 1 and 2 turbine blades are limited to 50,000 service hours using conventional repair techniques. Standard service practice is to perform a strip and replacement of external airfoil coatings at 25,000 hours and then retire the blades at 50,000.

   Technical reasons for retirement at 50K: The internal protective coating is exhausted at this point, and the blade alloy has weakened because of its long-term exposure to high temperatures.

   Lloyd Cooke told the editors and users visiting the Liburdi Turbine Services booth that his company had an “advanced repair” process unique in its ability to remove the exhausted internal coating. The metallurgist said the chemical process first removes the internal oxides and then the coating material.

   After both the internal and external coatings are stripped, he continued, the blades can be processed through high-temperature heat treatments—so called FSR™ or full-solution rejuvenation—that restore new-part properties and strength. Coatings then are applied to the internal and external airfoil surfaces and the parts are effectively “zero-houred” and prepared for a second 50,000-hr service interval.

   Cooke said that Liburdi’s advanced repair process has been used successfully for more than 15 years to extend the lives of HP blades for the LM1600 and the Rolls-Royce RB211. Experience with the latter includes reliable service of some blade sets for 100,000 to 120,000 hours.

   The full-solution repair, Cooke continued, also has enabled buckets on some GE frames to achieve 100,000-120,000 hours of service. The process is offered to owner/operators of LM2500s as an alternative to the “conventional” repair. It must be requested by the owner or operator at the time of overhaul. The advanced repair has been licensed to and installed by several overhaul services firms.

   Cleaning catalyst properly takes know-how, experience. 

   Clean catalyst is a prerequisite for efficient turbine operation within permit limits. The majority of gas-turbine-based powerplants installed in the last decade are equipped with an SCR for NOx control, most of those also have CO catalyst. Telltale indicators of plugged or fouled catalyst include an increase in pressure drop between the engine and stack exit, a decrease in power output, and/or an increase in ammonia slip.

   Jeff Bause of Groom Industrial Service Group suggests a thorough visual inspection of catalyst when the possibility of plugging or fouling exists. In most cases, you’ll see a blanket of insulation on the face of the catalyst; sometimes fines will collect in the pitch of the material. Look for a crack in the transition liner to locate the source of the insulation. Another foulant is the chemical byproducts of tube leaks.

   The cleaning technique Groom uses is to blow very clean, very dry air through the catalyst from the downstream face while vacuuming the upstream side. This is done until no foreign material is being collected by the vacuum. As cleaning proceeds, any catalyst blocks that have shifted during operation are returned to their proper position and the gasket material around the blocks is replaced as necessary.

   Not all jobs are the same, Bause said. Some catalysts have multiple layers that are so close together one layer must be removed to clean the second. A typical job is planned using boiler drawings so there is no delay when the cleaning crew shows up onsite. Groome does its work turn-key from the installation of scaffolding to its removal.

   The company has designed several different nozzles and developed multiple procedures to assure optimal cleaning no matter what the catalyst type or manufacturer. CO catalyst generally has a torturous path, Bause said, and debris often gets stuck in the catalyst turns. An SCR catalyst can have a torturous path but normally is straight-through. Groome recommends the plant owner/operators install instrumentation to monitor the pressure drop across individual catalyst beds.

   Install a clutch, provide ancillary services. 

   Morgan Hendry, SSS Clutch Company Inc, told the editors he’s seeing more interest in clutches these days as rapid deployment of intermittent renewables—wind in particular—forces grid companies to contract for ancillary services—such as fast-start generation, voltage support, etc.

   Having a clutch allows plant operators to disconnect the generator from its driver when, for example, it is more important to regulate reactive power for grid voltage support than it is to produce kilowatt-hours. The clutch typically is retrofitted on a non-geared machine by breaking the coupling that connects a gas or steam turbine and its generator and moving the latter a short distance to provide the space required. A geared retrofit is easier and less costly because the clutch is built into the existing gearbox.

   When the clutch is open, the generator behaves as a motor. Its field is controlled by a voltage regulator to either produce or absorb reactive power as needed. Advantage of the so-called synchronous condenser is the ease with which the amount of correction can be adjusted.

   Hendry said his company recently provided clutches to the engine OEM for four new LM6000s being installed at a major East Coast utility. They are replacing tired FT4s which suffer high losses in spinning reserve (fast start) service. With the clutch open on an LM6000 and its generator connected to the grid, the “motor” draws only about 400 kW, which is far less expensive than operating a hard-coupled turbine/generator at low load.

   When power is needed, the gas turbine is started and comes up to speed (the generator already is at speed). The clutch then engages automatically and the unit spins idle for a short time and is loaded to meet demand. The nameplate rating can be reached in about eight minutes.

   HRSG inspection and maintenance planning. 

   Bremco Inc’s Bill Kitterman talked about the problems some operators are experiencing from wear and tear on transition ducts (Fig 4). After heat-recovery steam generators operate for 10 years or so under today’s demanding service conditions—such as daily cycling and fast ramping—you can expect damage to the liner that allows insulation to be sucked downstream, he said.

   Fouling of CO catalyst is one possible problem when insulation goes airborne. Insulation exposed to high heat over a long period deteriorates and the resulting powder is carried along with the exhaust gas stream, limiting catalyst effectiveness. In some severe cases, it might not be possible to meet the permitted CO emissions limit at full load and vacuuming of the catalyst face will be necessary.

   Fouling of the SCR catalyst is another possibility. This can compromise NOx destruction and possibly cause over-feeding of ammonia. The latter could increase ammonia slip beyond permitted limits. Reducing power output might be a short-term fix, but eventually the catalyst will have to be cleaned.

Finally, any foreign material in the exhaust gas stream that gets by the catalyst beds is likely to contribute to plugging of the finned heat-transfer sections in the back end of the unit, thereby reducing efficiency.

   To minimize the possibility of catalyst and finned-tube fouling, Kitterman suggested regular walk-downs of your HRSGs with a thermal imaging gun to identify hotspots. Followup internal inspections of the liner area should be conducted to determine the extent of damage and to plan the necessary maintenance.

   Borescoping the LM6000: What not to overlook 

   Mike Hoogsteden of Advanced Turbine Support Inc has been around gas turbines most of his adult life. Early in his career he was a commercial pilot; today he manages the field service activities of Florida-based Advanced Turbine Support. Hoogsteden’s inspection career began shortly after ATS opened for business and he has been crawling over engines and performing borescope inspections since. He has seen first-hand most kinds of damage that occur on both frame and aero engines.

   Hoogsteden offered his thoughts on three areas that LM6000 owner/operators should be sure not to overlook on their next inspections:

  • Inlet gearbox spline. This is a tight area to navigate but the borescope can gain access and do a good job of identifying such things as sludge formation, wear, dirt, metal chips, tooth wear, etc. A clean bill of health gives a user confidence in employing condition-based maintenance programs to reduce cost.
  • HP compressor rubs, which are most likely to occur on the LM6000 in the area of stages 5 and 6. The telltale indication: Rub marks on the case. Hoogsteden noted that casing rubs on aeros are not as severe as those experienced on F-class frames, where rolled metal and burned blade tips often are in evidence.
  • HP turbine, stage 1 blades. Check for hot-gas erosion and coating loss. You can expect to find coating loss beginning at about 8000 to 10,000 hours.

   Hoogsteden stressed that there is much more to look at than the areas identified above. Regarding the time requirement for a proper inspection, Hoogsteden said it takes about eight to 10 hours to inspect a machine fully prepped for the activity. That can stretch to a maximum of about 12 hours if findings warrant a more detailed investigation.

   Factor the generator into your maintenance planning. 

   It’s highly improbable that anyone is more passionate about generators than National Electric Coil’s Howard Moudy, a frequent speaker at user-group meetings. He pulled the editors into the NEC booth as they walked down the aisle to share his thoughts on generator maintenance.

   Moudy’s primary message: Users have to rethink maintenance intervals. What may have been accepted practice 10 years ago is not appropriate for today’s machines. Tighter design tolerances and more demanding operating conditions (faster starts and loading, for example) demand more frequent inspections and maintenance.

   He pointed to end windings as a case in point. Today’s end windings are narrower, taller, and longer than those of the past because the smaller generator packages are operating at higher voltages and increased outputs. The new configuration is difficult to keep tight and the resulting vibration contributes to dusting and greasing.

   When did you last check the exhaust silencers? 

   David Clarida, Integrity Power Systems, knows gas-turbine inlet and exhaust systems. He had years of experience in the design, installation, and maintenance of front and back ends for aeros and frames with GE Energy and Braden Manufacturing LLC before launching Integrity Power Systems (IPS) a couple of years ago.

   Clarida suggested that one area users might be overlooking in annual inspections today is the condition of exhaust silencers. Noise is becoming more of a concern as eco-friendly gas-fired plants are located closer to load centers. A little inspection and maintenance goes a long way in avoiding noise complaints from neighbors.

   Clarida said exhaust silencers can be installed in horizontal ductwork just ahead of the stack breeching or in the stack proper and a visual inspection for condition is relatively easy. He suggested checking the stack periodically on startup to see if insulation is present; also, examining the perforated plates to verify their integrity. What happens is the high-velocity exhaust gas stream sucks insulation out of the silencer and as the quantity of insulation decreases, the metal suffers thermal damage conducive to failure.

   It’s rare that an owner/operator pays much attention to exhaust silencers, so it should not be a surprise that the low-bid offshore supplier might use thinner gauge steel than the spec calls for and not do much in the way of fabrication quality control. It is unlikely that the intended design lifetime will be achieved.

   Duct balloons reduce corrosion of gas turbines during layup. 

   Peaking gas turbines often remain out of service for prolonged periods—the shoulder months for example. In some climes that’s enough time for corrosion to do some serious damage to exhaust system components.

   Duct balloons can help minimize metal attack by preventing the free flow of moisture-laden air through the unit by putting one balloon in the inlet, one in the stack, Gary Werth, G R Werth & Associates, told the editors. Recall that the pressure differential between the compressor inlet and the top of the stack drives the flow of air.

   Duct balloons are designed to expand larger than the actual duct size to assure a tight seal. The material used typically is the nylon fabric Cordura®, sometimes referred to as ballistic nylon. The material weights used range from 400 to 1600 denier. For comparison purposes, consider that the flag outside your post office probably is 200 denier.

   Prevent compressor-blade erosion. 

   The LM6000 Sprint is equipped with water spray injection at the engine inlet for interstage cooling of the compressor. Water injection contributes to water droplet erosion of some compressor stages and such leading-edge erosion can cause serious problems. This dictates that the operator remove the engine every 12,000 hours and replace the blades in four compressor stages. 

   To minimize the need for costly re-blading, a titanium nitride coating can be applied to compressor blades to protect against erosion. TiN is a very hard, smooth, and thin coating that has been proven successful for many years in preventing erosion of compressor blades for aircraft turbo-prop engines. 

   Lloyd Cooke said Liburdi Turbine Services introduced the erosion protection coating over 10 years ago and since that time it has been used extensively on Rolls Royce and GE turbo-prop flight engines operating in harsh environments—for example, military helicopter and cargo planes landing on unimproved runways and ingesting dust and sand. The coating is tested and approved by Rolls-Royce and has been used on all USAF T56 engines operating in severe environments for the past eight years. It achieves three times the service life of uncoated compressor blades.

   What Liburdi recommends for the LM6000 Sprint is known as Generation III of the original TiN coating. It offers superior toughness, corrosion resistance, and protection against water droplet erosion. Some operators are now considering applying this proven coating to blades in vulnerable compressor stages of the LM6000—in some cases along with the uncoated blades to compare the benefits. The intent is then to be able to have all compressor blades for the Sprint perform for full service intervals, just as the non-Sprint variant of the engine.

Engine breakout sessions

LM2500

Session chair and discussion leader for the LM2500 breakout sessions was John Baker. At the time of the meeting he was O&M manager for Calpine Corp’s Bethpage Energy Center, Hicksville, NY. Baker currently is a plant manager for Riverside (Calif) Utilities. Session secretary was Chad Flowe of SPS. The depot presentation was led by MTU Maintenance’s Christian Czmok. He was supported by Chris Martin ofANZGT, Kevin Singh of TCT, and Claudio Vinci of Avio.

   Czmok began by reviewing the operating status of the LM2500 fleet and recent service bulletins and service letters pertaining to the engine. Keep in mind that not all SBs pertain to every engine model. Users should carefully review each publication an determine its applicability for their machines. Once again, owner/operators were reminded that access to the SBs and SLs was via GE’s customer web center.

   Engine stats compiled in summer 2010 indicated that the LM2500 fleet (all models) numbered more than 1400 units—slightly more than 1000 equipped with single annular combustors and nearly 400 with dry, low-emissions combustion systems. Fleet operating hours (all engines) had passed 57-million hours, with SAC units accounting for more than 49 million. The high-time SAC engine was at 220,000 hours, the high-time DLE unit half that number.

   Also of interest: Almost 20% of the nearly 1000 base LM2500 engines are DLE-equipped, while more than half of the LM2500+ and LM2500+G4 units have single annular combustors. The high-time LM2500+, SAC-equipped unit had operated for more than 100,000 hours by summer 2010. 

   Introductory material complete, depot findings since the previous meeting were reviewed and discussed in detail, starting with the compressor and moving to the turbine.

   Compressor front frame (CFF).  First topic was the stationary air seal. The old-style seal is made of a composite material that is prone to cracking. Damaged seals are not repairable. Replacement seal has a stainless steel body and resists cracking. Attendees were informed that an indication of composite cracking is Teflon sand-like particles in supply filters. Depots are prepared to replace damaged seals with the upgrade next time the affected engines are in the shop.

   An internal oil leak was observed during normal operation of a base engine. A pressure test at a depot shop eliminated tubes and seals as the leak source and confirmed oil was seeping from between the sump cavity and the No. 4 supply strut. No authorized repair is currently available and affected users were advised to replace the CFF.

   HP compressor rotor. There was considerable discussion on the HPCR. Topics included the following:

  • Spline adaptor wear. Red paste/sludge deposits have been found blocking the spline-adaptor oil galleries mounted on the Stage 2 disk (most often on LM2500+ engines), with heavy wear to both the adapter and the mating IGB gear shaft. Monitoring of oil pressure and A-sump scavenge-oil temperature was recommended along with a semiannual visual inspection.

   Corrective action includes (1) installation of the rugged oil nozzle with improved oil-jet impingement recommended in SB IND-160 and (2) the new spline adapter having four drain holes (SB IND-199), to improve the flow of oil through the spline interface. Finally, use of HTS (high thermal stability) oil is not recommended by the OEM (SB 10-03 R1).

   Question from the floor: How can you tell the difference between HTS and non-HTS oil? One user offered that HTS oil is black. A depot representative suggested that owner/operators reference the OEM’s qualified product list or ask their oil provider to differentiate between HTS and non-HTS oils.

  • Inlet air filtration. Leading-edge erosion of airfoils—especially IGVs and Stage 1 blades—is conducive to a crack/failure event with the potential to heavily damage the compressor and other downstream components. The group was told that engines in dusty and sandy environments were most susceptible to mechanical erosion. Owner/operators were urged to inspect and monitor airfoil erosion rate in affected engines.
  • Stage 1 blade event. Every operator’s nightmare, blade liberation occurs most often in marine environments. It is identified by a steady increase in vibration level, which will lead to an alarm unless observant operators shut down the engine manually beforehand. Blade separation above the damper section typically causes extensive compressor damage and lighter damage downstream and ahead of the power turbine.

   Erosion and/or pitting aft of the leading edge on the pressure side of Stage 1 blades is believed to be the cause and is under investigation. Frequent borescope inspections are recommended. Users were urged to shut down any GT experiencing a step-wise increase in vibration and to visually inspect Stage 1 blades through the inlet screen.

  • Stage 7 blade event. Blade separated above its platform, and like the Stage 1 event above, damaged the compressor, with lighter damage downstream and ahead of the power turbine. This unit also was in a marine environment. The incident was still under investigation at the time of the meeting and no additional details were available. A depot representative said the unit had operated only about 2000 hours when the failure occurred—this in response to a question from the floor.
  • Stage 14-16 spool. The abradable coating was found with light wear on a depot visit and was processed as a standard repair for coating refurbishment. When the aluminum coating was removed, damage to the spool was noted and the component replaced.
  • Stage 16 blades. Several incidents of platform cracking at the trailing edge have been identified during borescope inspections and the issue is under investigation by the OEM. Cracking of blade-tip corners was said to have been resolved for LM2500+ units by following recommendations in SB IND-161 and IND-162, but that platform cracking has been observed in some of these engines. Base-engine owner/operators were advised to consult SB 180. Depot representatives suggested that all usersNDEStage 16 blades when possible.

   HP compressor stator (HPCS). VSV system wear, which had been discussed at one or more meetings previously, was on the 2011 agenda. Several reasons for vanes being off-schedule—such as missing or degraded/brittle actuation-arm sleeve “top hat” bushings, worn actuation ring segment/ “bridge” connector holes, worn/loose vane actuation-arm pins—were discussed.

   The depot representative noted that general wear and tear causes “play” or looseness in the VSV actuation system and this can be exacerbated by dirty conditions. The obvious recommendation: Keep your equipment clean. Also, replace any actuation arms with bends in excess of 4 deg (as measured with an appropriate gauge, not the human eye). Reason: Air-flow disturbances that might occur are conducive to high-cycle fatigue, which can lead to blade failure/liberation.

   Compressor rear frame (CRF).  Focus was on mid-flange damage. The depots reported that radial cracks tend to propagate from unused mid-flange bolt holes and spread outward through the edge of the flange and inward through the radius and into the case wall.

   The good news for power generators is that CRF cracking is far more prevalent on marine engines than on stationary turbines. The cause of CRF cracking is HCF, which occurs because of alternating stresses in the bolt holes. The stresses are highest between 7000 and 8000 rpm, which is where most marine turbines operate.

   It was said that there’s no benefit in installing bolts in unused bolt holes in industrial engines. However, users were urged to check bolts for proper torque when practicable to prevent elongation of bolt holes. Keep in mind that welding of cracks in the CRF is not permitted; rather, the component must be replaced.

   DLE combustor.  Burning of heat shields and TBC loss typically is associated with 50,000 hours of service. Excessive TBC loss is conducive to unrepairable cracking of heat shields (75 to a set). Since design does not permit single-part replacements, the complete set must be changed-out. Best practice: Recoat heat shields with TBC as needed to prevent the onset of cracking.

   HPTStage 1 nozzle assembly.  Temperature spread and increased NOx emissions suggested removal of the Stage 1 nozzle assembly. Segments were found with damaged or missing outer seals. High temperatures and/or HCF can cause sealing plates to break and resulting air inleakage is conducive to hot spots. SB IND-221 was said to offer corrective action.

   HPTrotor (HPTR).  Some users have experience high fallout of blades at the first repair cycle; trailing-edge cracking from thermal fatigue has been noted. Corrective action: Swap-out existing airfoils with L47459G05 blades, which have improved cooling to extend creep life and resist LCF. At previous meetings, owner/operators were urged to replace their G01 blades with G03. However, the G05 design, released in 2009, is better still. Keep in mind that bucket numbers should not be mixed in a given row.

   SecondHPTrotor topic: Corrosion of Stage 1 and 2 damper assemblies has caused the loss of dampers and retention wires. Recommendation was to change-out damper assemblies on oil-fired units at 25,000 hours, gas at 50,000 hours, with the OEM’s latest hardware.

   Turbine mid frame (TMF)  received significant attention:

  • Air seal damage was the first topic. Inspections have revealed irregular grooves in honeycomb seals, deformation of the stationary LPT air seal, and cracks in seal arms. Investigators learned that seal teeth on the LPT Stage 1 disk can get caught by honeycombs and that the stationary air seal can be damaged if the power turbine is not removed properly.

   A user question: Can air seal damage be repaired in the field? A depot representative suggested that the LPT might be too cumbersome to take off in the field and recommended that the repair be made at a depot shop.

  • Missing T-5.4 deflector shield can result in damage to LPT Stage 1 blades. Such damage can be difficult, or impossible to repair, because of the coated airfoil surface. Read GEK 105056 for guidance.
  • Liner cracking/bulging. Cracking, bulging, and distortion of the outer liner are being found more frequently as engines age. TMF liner material has been changed from Hastelloy X to HS 188 to help resolve the issue. Consult SB IND-072 and IND-074 for information on steam baffles and ring that can be installed on engines using CDP steam to resist cracking.
  • Cracks in fabricated cases was another issue discussed. Attendees were referred to GEK 9266, SL I-02-001, SB IND-175 and SB IND-175 for guidance.
  • Excessive wear at the C-sump vent and ninth-stage cooling-air and oil-scavenge tube (Nos. 2 and 6 locations, respectively) was identified between the strut cap oval sleeve and tube. Recommendation: Replace both the No. 2 and 6 oval sleeves with the latest L605 material parts as indicated in SB-215.
  • Excessive wear at the oil seal drain and oil scavenge tube (Nos. 5 and 6 struts, respectively) between strut caps and tubes is associated with cracking at the aft-flange seal. Several documents were recommended for further reading, including: IND-215, IND-187, IND-190. Inspection of tubes according to SL I-04-07 was suggested as well.
  • The session chairman said the issue is associated with both cycling and base-load units in response to a question from the floor.
  • Swap-out of a fabricated case with a cast case requires a new retaining ring (L50630P01/P02) and outer seal (9084M71P02). The single-piece case was cast in a manner that increases metal thickness in areas that require a reduction in stress.

   LP turbine stator (LPTS).  The depot representatives ran through a series of slides addressing issues with the forward support ring for the case, chafing and fretting wear caused by contact of the cover and the outer lip of the LPT Stage 1 nozzle or the nozzle’s seal strip, and related areas of concern. It probably was information overload at that part of the session because the users were not inclined to discuss any of the points.

   Miscellaneous topics  included the following:

  • Bearing corrosion is more prevalent in marine environments. Moisture also gets into bearings of units being water washed and left to dry and then not operated or cranked for long periods. Corrosion to main line and gearbox bearings is a likely outcome. Application of best practices regarding operating procedures is the solution.
  • Worn tubes and the possibility of an oil or air leak can be mitigated by applying common-sense lessons learned to combat the effects of vibration, sliding, and chafing. One solution: Use tape on clams with metal-to-metal contact.

   Engine preservation, handling, and transportation.  Users were urged to follow OEM-recommended procedures during shipping and handling. Where this has not been done, there has been an above-normal incidence of bearing failures and damage. All sites might consider having their own engine container and keeping it properly maintained.

   Vibration during transportation is another area of concern. The OEM and at least some insurers strongly suggest that vehicles transporting engines have “air ride” suspension.

LM2500 package issues

The package discussion topics were developed by Chairman Baker, who led the session. He began at the filter house and went through the unit throwing out keywords to remind attendees of something that might be bothering them. Discussion topics related to the filter house included the following: prefilters, primary filters, canister filters, instrumentation, chiller coils, inlet heaters, corrosion issues, FOD screens, ventilation system issues, etc.

   As Baker continued through the package, discussion topics included fire-system issues, certifications with local fire departments, hydraulic start skids, and TCS control systems. An important question brought to the floor: Was someone coming up through the ranks to replace Nick Vourhes once he retires? Rounding out the session were discussions on turbine and generator vent fans, lube oil systems, and vibration monitoring systems.

   Package issues generate a valuable exchange of ideas, which can come so quickly it’s difficult to take meaningful notes. You really have to be in attendance to benefit from this part of the program.

LM5000 breakout

Session chair and discussion leader for the LM5000 breakout session was Chuck Toulou, Ripon Cogeneration LLC, Ripon, Calif; session secretary, Strategic Power Systems’ Daniel Murray. Depot presentations were made by John Leedom of ANZGT and Nico Brademann of MTU Maintenance.

   About 20 users attended each of the breakout sessions for this engine. Fleet status has changed little over the last few years because this model no longer is being manufactured. Currently there are 56 operational LM5000s (31 in theUS, 16 inEurope, and nine more scattered over the remainder of the world), plus 12 customer spares and 12 GE lease engines (only three serviceable and ready for operation). Total fleet operating hours number about 7.2 million; the high-time engine is north of 180,000 hours.

   The fleet status report was followed by a review of applicable service bulletins and service letters. In 2010, two new SBs were issued and three were revised. If you missed receiving these documents, visit the GE website to access them and to register for electronic notification of future bulletins and letters.

   Before discussing depot findings since the last WTUI meeting, a point was made about the definitions of “limits” as used in the O&M and Industrial Repair Manuals. These are good to keep in mind:

   O&M Manual.  Onsite maximum serviceable limits [RM] means that if criteria are met, no action is required for continued operation for the next 4000 hours, 450 fired starts, or annual period—whichever comes first.

   Onsite maximum repairable limits describes repair limits that can be performed in the field—that is, Level 2 maintenance.

  • Industrial Repair Manual. Maximum serviceable limits means that if criteria are satisfied, no action is required for continued operation until the next scheduled maintenance interval.

   Maximum repairable limits describes repairs (in depot) that can be performed to make the part suitable for continued operation until the next scheduled maintenance interval.

   LP compressor (LPC): 

   1. SB 5000-IND-215 was announced as planned for release to address cracking issues at the base of Stage (S) 0 blades. At the time, only three incidents had been reported and those were on offshore units. The repair, application of a special coating within the base area of the blades, is done at a depot, except for units installed on platforms.

   Serviceable limits for S0 blade cracking are presented in the O&M manual. For cracks just beginning to develop, it was said that the OEM is willing to work with users to extend serviceable limits consistent with established criteria.

  2.  One depot is investigating two recent incidents where S0 blades were pinched between the aft spinner and S0 disk. Cause is thought to be dimensional issues either with the blade dovetail length or the aft spinner, leading to vibration issues because of restricted blade movement.

   Buildup of corrosion products in disk slots could have the same effect, as discussed during the previous two Western Turbine meetings (access WTUI reports in 3Q/2009 and 3Q/2010 at www.ccj-online.com for more on this and other issues discussed here). Severe buildup has been observed in S0 and S1 disk slots—a condition conducive to excessive rotor vibration. Hand cleaning was recommended when the unit is not operating, this in addition to the standard recommended water-wash intervals.

   3. Rim bolt-hole cracks were found in the LPCR forward shaft in at least one unit during the last year. Investigation revealed the cracks originated from a corrosion pit. A similar incident was reported last year as well. Best practice for prevention is to follow preservation procedures when the engine will be out of service for an extended period.

   LPCR blade corrosion also may occur when the unit is offline. Use borescope inspection to identify metal attack and clean as necessary. Rotor corrosion issues may result if blade corrosion is not addressed in timely fashion. Improved water wash and rinse practices can mitigate the problem.

   4. Early No. 1 stationary air/oil seals made of a composite are prone to leakage and disintegration. Latter could allow debris into the LPCR S2-S4 spool, causing imbalance and high vibration. Problem is much more common on the LM6000. Recommendation was to incorporate SB 179 Rev 2 and SB 214 during the next exposure of this area.

   The OEM believes this is an unusual event and related to environmental and operational factors. Use of incorrect oil and high lube temperature could degrade the composite by breaking down the resin.

   HP compressor (HPC): 

   1. Some cracks found in S1-disk air seal serrations have propagated into the spacer-arm area and cannot be repaired. In a few instances, these axial cracks have propagated both forward and aft, connected, and caused a disk fracture event with parent metal liberating into the HPC. 

   Rub condition caused by less-than-minimum clearance between rotor seal serrations and stator S1 shrouds is thought the cause of disk cracking based on early investigatory work. What happens when a seal/spacer arm rubs, which it is not designed to accommodate, was illustrated by passing around an affected arm. The seal showed significant damage as well as oblong bolt holes. Absent a comprehensive meeting like Western Turbine, how would users get a first-hand look at a damage mechanism of concern?

   Best practice: The group was told that by following the recommendations presented in SB 216, the nominal clearance required to prevent rubbing would be maintained.

   2. The users were updated on engine vibration related to disbanding/disintegration of the vespel strip (refer to notes from WTUI 2009) and a loose air duct. They were referred to SB 184 and SB 210.

   3. When a stall is detected, operators should investigate immediately to determine the cause; sometimes it’s a pseudo stall event. A borescope inspection of the HPC is mandatory. Tip-clanging marks are evidence of a real stall event. Tip clanging is most prevalent in S3 and S9, but can be visible in other stages.

   4. Distorted, broken, and worn VSV hardware received a significant amount of attention—more so than last year. Worn pins, missing bushings, elongated pin holes, sheared lever arms, worn bearings, and worn trunnions were identified during the dialog. The speaker stressed that VSV components are relatively inexpensive and that “saving” by not replacing damaged parts increases the risk of costly damage to theHPC.

   One attendee asked if there was a standard replacement cycle for these parts. Answer was a simple “no.” Lever arms should be inspected when the unit is not in operation, the user was told, and parts replaced as necessary. Two other best practices: (1) Clean this area of the machine periodically with a suitable detergent/pressure wash to help prevent issues, and (2) inspect and tighten hardware regularly.

   Compressor rear frame (CRF), combustor: 

   There was no user discussion on these sections of the engine. Most meetings do not generate many questions on the LM5000’s combustion section. However, the CRF did produce significant discussion last year, perhaps indicating the positive effects of implementing the action items suggested in related service bulletins—such as SB 197 and SB 203.

   HP turbine (HPT): 

   1. Cracking of the S2 N filter screen was the first HPT discussion topic. The speaker said that if inspection indicates one or more support bolts have experienced severe fretting wear, or have broken, then a depot visit is necessary to replace the affected fasteners. This repair cannot be completed in the field. Bear in mind that filter-screen support is necessary to hold the HPT outer seal engaged in the combustor “fish-mouth” seal slot.

   2. HPTR forward shaft and stud/bolt was next on the agenda. A couple of incidents were reported regarding the use of incompatible bolts—specifically, hardware designed for the old style forward shaft being used with the new style shaft. Recommendation: Inspect your unit to verify that bolts do not impinge on the radius. If you identify incompatibility, the correction must be made at a depot. Read SB 213 to see what’s required.

   Turbine mid frame (TMF): 

   TMF liner clocking is an issue common to many LM5000s and most prevalent in units with high-hours liners. Attendees were told that there’s no way at present to stop liner clocking altogether. Were welding permitted in this area, perhaps clocking could be stopped. But welding currently is not allowed.

   LP Turbine (LTP). 

   1. Pitting corrosion of the LPT is occurring more often today than in the past. Suggestions: (1) Look for corrosion during borescope inspections, (2) perform water washes more frequently, and (3) use package preservation procedures when the unit is not in operation for extended periods.

   2. Cracking of the AGB No. 2 pad also is being found more often. Interestingly, the same part is used on the LM2500 but cracking was said not to be in evidence on that model. The group was urged to inspect this area periodically. If a crack is identified but no oil leak is visible, the condition is considered acceptable. However, the depot should be notified of the crack when the engine is sent to the shop. Where oil is found, the part must be replaced.

   3. LM5000 mainline bearing issues still are being found from time to time. Inspections have identified Brinelling caused by transportation/handling damage, pitting corrosion, foreign object damage, and skidding of the ball and roller elements. Owner/operators were urged to take all alarms (temperature, vibration, chip detectors, etc) seriously and to pay close attention to trends identified from the charting of lube-oil analysis results.

   Also, correct handling of bearings during hot-section inspections and maintaining bearings oil-wetted during storage are important to the health of these components.

   Performance loss and restoration was a topic of interest to virtually all in attendance. The depots offered the following as the most probable reasons for poor performance of key components for the CF6-60 aero engine—the core of the LM5000.

LP compressor:

  •             Excessive dirt.
  •             Excessive blending.
  •             Large tip clearance.
  •             Leading-edge contour.
  •             Brinelling caused by transportation/handling damage.
  •             Pitting corrosion on the rings.

HP compressor:

  •             Large tip clearance.
  •             Stator schedule error.
  •             Excessive dirt.
  •             Excessive airfoil chord width reduction caused by erosion/repairs.  
  •             Excessive FOD or blending repairs.

HP and LP turbines:

  •             Large tip clearances.
  •             Wrong nozzle area.
  •             Damage.

Also, in the case of the HP turbine, high parasitic losses (increased seal clearance, blocked cooling-air passages, large mini-nozzle area).

   The speaker pointed out that match grinding ofHPTcomponents is as critical to good performance, as is refurbishing of seals, to keep clearances near the lower limit.

   Lifetime management of critical parts  is a responsibility of owner/operators to protect against physical damage to property and to ensure the safety of plant personnel and the public at large.

   WTUI members should be maintaining cyclic life records of critical parts to enable their timely removal from service. Where such record-keeping has not been done consistently, owners can consult with the OEM regarding a “best estimate” of life expenditure and then collect and maintain follow-on data.

   Plants that do not have the tools and manpower to track parts lives might consider a third-party—such as Strategic Power Systems—to handle the task. Learn how some of the industry leaders are tracking their parts lives by reading the summary of an exclusive WTUI panel on the subject beginning at the bottom of p 24.

   The OEM put together a chart of LM5000 critical parts—26 in total—that was presented to attendees. You can find it on the www.wtui.com website by accessing the “LM5000 Breakout Session” notes in the user-only portion of the site. The chart is on p 62.

   Engine handling, transportation, storage, and preservation is a subject covered in all of the breakout tracks and is virtually the same for each engine. Key points are available in theCCJreports on the 2009 and 2010 conferences (see reference above). A logical sequel to this subject was “Tips for a Successful Depot Experience.” Success depends in large measure on the quality and quantity of engine O&M information collected since the previous overhaul and provided to the depot.

   Open discussion: 

   1. LP mid shaft, excessive twist. With regard to two shafts recently rejected as unserviceable because of excessive twist, a user asked about the availability of replacements should others be so affected. An OEM representative said this was not a common issue for the LM5000 and that a shaft could be retrieved from a retired unit if necessary.

   Another question: Where the two engines with twisted LP mid shafts running well? Answer: Yes, no operational problems that would correlate to the twisted shaft issue were reported.

   2. CFRinner diffuser panel, cracking. Parent panel material in this area liberated as cracks intersected. Cause was severe engine vibration over a long period. Event is unusual for an LM5000. Liberated parts were found in the CRF sump area.

   3. Combustor, wear and cracking. Combustor hardware revealed significant wear as well as cracks and metal liberation. Cause was thought to be high vibration but no data were available. Periodic borescope inspection was recommended.

   4. HPTS1 N support, cracking. The cracking initiates in the welds, allowing CDP air to leak across cavities and causing excessive loading on the No. 4B bearing and possibly a bearing event.

   5. No. 4B bearing events. Discussion was conducted on several issues affecting No. 4B bearings. Consensus was that this is a component requiring monitoring of both temperature and vibration. Regular borescope inspection was suggested as well. No. 4B bearing issues are not common for the LM5000.

LM6000 breakout

Session chair and discussion leader for the LM6000 sessions was Bryan Atkisson, plant manager, Riverside (Calif) Utilities; session secretaries, SPS Senior VP Tom Christiansen and Weston Trimble. Participating depot representatives were Steve Willard of TCT, Ralph Reichert of MTU Maintenance, and Ken Udea of IHI Corp.

   The breakout sessions at Western Turbine meetings are rigorous. For the experienced, they provide the opportunity to catch up on new issues identified by the depots that should be incorporated into inspection/maintenance routines. For those still getting familiar with the engine, the eight-hour program for each gas turbine, spread over the three days of the annual conference, is an invaluable training exercise.

   Participants in the LM6000 breakout numbered over 150, split about 50/50 in terms of experience. By show of hands, half of the attendees had five years or less with the engine, nearly half those less than two years.

   The first half hour or so of the breakout for each model is about the same: introductions of depot speakers, the role of authorized depots in operational success, engine fleet stats, purpose of SBs and SLs and how to access them, familiarization with the OEM’s website for customers, availability of vouchers (discount coupons for maintenance), O&M Manual versus IRMlimits (see LM5000 for details), etc. Particularly noteworthy, perhaps, is that the 1000th LM6000 was shipped just prior to the WTUI meeting

   Boiler-plate complete, group adrenaline gets pumping. Here are 25 selected LM6000 depot findings and user experiences discussed inPalm Springsthat occurred between the 2010 and 2011 meetings:

   1. DLE premixer shroud wear and cracking was identified during a 25,000-hr onsite borescope inspection of an engine fueled by natural gas and operating near base-load. The group wanted to know if this was typical. Answer: yes. Recommended action was to replace damaged parts with new.

   2. Fan mid-shaft corrosion and tang cracks were identified in an engine that had not been operating and had been sitting in the package for along time. Package was heated but high humidity and water remaining from water-washing were contributing damage mechanisms. In this case, a one-time repair was possible.

   3. AnHPTStage (S) 2 nozzle segment tilted into S2 blades, liberating a couple of those airfoils and causing significant downstream damage. Engine had operated for 14,000 hours at near baseload. Incident affected one engine; it was not a fleet problem. Suggested action: During borescope examination, be sure to check all vane airfoil radaii for cracks running parallel to the outer platform.

   4. LPC blade and case erosion on a Sprint-equipped unit stimulated helpful discussion from the group. A significant erosion groove was found in this LPC case at the drip-down edge of S0 and S1 compressor blades. Group consensus was that the OEM should redesign the manifold; a design like that used for the water wash system was suggested as a fix. Possible reason for the problem was wrong-size water droplets. Users “in the know” urged their colleagues verify water nozzle cleanliness regularly; nozzles were said to clog-up fast.

   There was more discussion on this subject the following day. Eroded nozzle holes allowing too much water flow, or improper atomization, were cited as the primary causes of leakage.

   5. No. 1 bearings have a service life of about 50,000 hours. Replacement at that time has been the standard operating procedure. GEK 98492 now offers the option to return the bearing to the manufacturer for repairs. By show of hands, not many in the room were interested in doing that. Attendees believed repairs would cost half as much as a new bearing.

   6. LPT S5 blade shroud gap. Misalignment and airfoil twist are associated with abnormal wear in tip shrouds. Result is HCF in the shank. Two events were identified with LM6000PCs.

   7. LPT fifth-stage blade fracture culminates in liberation. The group appeared surprised that a blade with only 1500 hours of service could suffer HCF, but attendees were reminded that for a blade rotating at 3600 rpm the total number of cycles over a 1500-hr period actually is quite high. Once a crack initiates it can propagate quickly to failure.

   8. Primary swirler retention. The issue discussed involved disengagement of the primary swirler. Question from the group: “Does the primary-swirler retention issue have an effect on fuel-nozzle wear?” Depot experts thought not. Continuing Q&A revealed that operators are removing nozzles earlier than 4000 hours and then borescoping; also that swirler replacement is a Level 5 item.

   9. Anti-rotation tab wear: Can you run with wear? Depots said yes, provided you have secondary tab engagement.

   10. Nozzle cooling tubes were discovered on borescope inspections to have rotated out of position as well as to have broken up. Issue has been identified most often in peaking units, the group was told, but it has been found in base-load units as well. One user reported that casing tubes on one of his units came loose in only 1000 hours and that all the nozzles had to be replaced to address the issue—obviously a big expense to correct a seemingly small problem. Depot response was “it’s a possibility but not a fleet-wide issue.”

   11. Critical parts life management discussion was relatively brief and seemed like a subject most would prefer to avoid. By show of hands, fewer than 20% of attendees were tracking critical parts (see summary of the Tuesday afternoon panel discussion on the subject, p 24). This is interesting considering the LM6000 was introduced 19 years ago and the life estimate is 20. Base-load participants indicated no parts replacement to date; one peaker owner reported anHPTS2 disk replacement in year 17; a unit in load-following service replaced its HPT S2 disk in year 16.

   12. Engine preservation was a topic on the minds of many attendees. Here are a few take-aways from the discussion:

  • Crank peakers weekly when they are not running.
  • Make sure engines shipped from the depot, even those in a pressurized shipping container, get oil every 30 to 60 days.
  • High humidity is the cause of most damage during lay-up.
  • Regarding preservation techniques for Sprint manifolds on units switching from base-load to peaking service, the only suggestion was to make sure no water is left in the lines.

   13. Sprint nozzles. About one-quarter of the attendees said they have never inspected Sprint nozzles. Recommendation was to check them after 25,000 hours of service—at least. One base-load user reported erosion on Sprint nozzle holes and said water can split-line. He wanted to know about a repair to deal with large-size droplets. Group response: Put new tips on them, but use stainless-steel parts not galvanized; the latter can erode quickly. Suggested maintenance: Periodically put Sprint nozzles in an ultrasonic cleaner and then reinstall.

   An operator told colleagues that one of his plant’s LM6000s had a split-line leak and found nine nozzles plugged, which occurred when the engine was installed onsite. A week or so later, another two nozzles were plugged. Preliminary conclusion is that bees are the cause. Eliminating the pluggage improved heat rate.

   A method for closing up gaps in the LPC system is to loosen bolts and then retighten them in the order specified by the OEM. Alternatively, you can dress the split line with RTV silicone gasket sealant and retighten.

   14. Discussion on gas-compressor oil carryover was triggered by this question from a user: “I run with natural gas and just put in a redundant gas compressor—screw type. What is the impact on oil carryover and coking?” Install an analyzer, one attendee said, it can cost upwards of $500,000 to clean up a mess created from carryover.

   One analyzer mentioned reportedly measures contaminants down to the micron level and graphs each type. An OEM rep suggested stopping the unit and cleaning it up if the analyzer confirms oil carryover. If you have enough oil to measure, he said, it’s too much.

   Another owner/operator offered: Install a coalescing filter. That suggestion was topped by one to add a filter after the coalescing filter. No one reported switching to a synthetic from mineral oil to reduce carryover potential as some European owners have tried, with a small measure of success. The OEM provided a word of caution: Be cautious of heating fuel because hydrocarbons will reform when the fuel cools downstream of the coalescing filter.

   15. HPCS3-S5 blade distress. S3 “edge of contact” coating wear and metal-to-metal contact can cause failure, attendees were told. Recent events (one S3 and one S5) revealed similar damage but no more information was available at the time of the meeting.

   16. SAC combustor. A historical perspective provided a segue to group discussion. Users were reminded that the G32 and G35 combustors often were problematic, citing fuel nozzle/primary swirler wear, splash plate oxidation, and secondary-swirler TBC spallation. The G39 was introduced via SB 208 to address these issues. Next came the G42, introduced via SB 243, to address primary-swirler retention.

   The exchange began with questions regarding the impact of gas quality and water injection rates on G32 performance. There weren’t many takers; a poll of attendees showed why: Only about 10% of the participants were operating with the G32 or the G35. The way to eliminate the issues faced by these owners apparently was to upgrade.

   17. SAC combustor swirler cracking. More than a dozen primary and secondary swirler cracking events were reported. If material is released and goes downstream, engine damage is highly likely. During borescope inspections, look for dark marks; they indicate possible cracking. Reference SL LM6000-IND-10-002 (June 2010).

   18.HPTS1 nozzle leading-edge distress. Five cases of premature distress reported. Oxidation is caused by backpressure inhibiting the flow of cooling air at the leading edge. It was said that PA and PC engines have tight tolerances and this issue does not exist in them.

   19. Check valves, 11th stage. Flaps can break at the hinges of some check valves because of separated air flow across the flap, causing fluttering and premature wear. SL LM6000-IND-024 (January 2011) addresses this issue. Specifically, valves are moved upstream so the separated air-flow region does not affect them. Change in location was said to allow valves to achieve their HGP inspection lifetimes.

   Someone asked how long they could run with broken valves. Not recommended, an expert said. If a rotor cooling pipe were to fracture, it could have significant adverse impact on rotor life.

   20. LPT S5 blade-shroud gap. There was quite a buzz in the meeting room when attendees were told of two unscheduled engine removals after roughly 40,000 hours of service caused by LPT S5 blade-shank separations. The events were associated with abnormal wear in tip shrouds conducive to HCF in blade shanks.

   Users were told that a gauge had been developed to forewarn of a potential problem and allow corrective action. A service letter also was in preparation at the time of the conference.

   21. Fuel metering valve loss of control initiated an over-temperature condition. Specifically, the fuel metering valve opened full (100%) during part load operation. Engine did not overspeed. Gremlin was found in the logic.

   22. VBV expansion-joint material distress. Two units reported apparent tears in their expansion joint materials in less than 4500 hours of service. Recommended action: Replace existing expansion-joint material with silicon armacid. A few others reported the same issue.

   23. A user had a problem with high temperatures on the hydraulic starters for two units. It surfaced during shutdown, when the units were in the 15-min cool-down crank. A few others had similar experiences. One offered no solution, another said the temperature control valve was found installed backwards at his plant and the problem was solved when that error was corrected, another found the thermostat installed upside down.

   Bring your problems to Western Turbine and the chances are good someone else has experienced them and can at least offer one or more paths to a possible solution.

   Later in the session the subject of spline wear on hydraulic starters was introduced. The discussion leader asked how many users were inspecting for spline wear. Only a few raised their hands. There was no reply regarding issues with replacing worn parts; in fact, no one said they knew of a procedure for overhauling a clutch. Here are several comments from attendees:

  • Clutch engaged when the engine was running and blew the clutch to pieces.
  • Base-load unit had its clutch seize during startup. Now clutches are overhauled every 10,000-12,000 hours.
  • A couple of clutches at one plant were losing oil, but personnel didn’t know from where. Turned out the seals were bad. All oil would leak out of a clutch within about 8000 hours.
  • Carbon seal overheated on one unit within two months following its installation. Seal had to be replaced for a second time.

   24. AGB seal failure. An attendee reported a leaking carbon seal in the accessory gearbox where the starting clutch engages. A colleague said his plant changed to a non-OEM carbon seal; the original OEM seal failed because of overheating. Another suggested that the seal may have cracked during installation by over-torquing bolts. Users helping users.

25. A user made a short presentation on feedback problems with fuel gas valves. He opened by asking how many users have experienced a gas-valve failure. By show of hands: about 20%.

   We have two dual-fuel PCs, he continued, which usually run on gas, sometimes oil. The engines are peakers and back up a nuclear plant. One unit with about 1500 hours of service was coming out of a water wash when it “hung up,” the valve remained open, and plant staff thought water got in the engine.

   Personnel blew out the water, restarted the engine, and it ran fine. Months later, the valve stuck again at 14%. Unit was shut down, valves were cycled, and the issue cleared up. After that, valves were exercised weekly. Finally, the valve was replaced and the issue disappeared altogether.

   When starting up on the early fall, the valve stuck at 80%, tripping the unit. The valve would not return to the 0% setting and it was replaced again. The valve manufacturer performed an RCA, finding only some wear on the valve sleeve. That was attributed to the valve cycling from 0% to 100% to 0%. Dither caused valve shaking at 0% even thought it was turned off.

   Rust was found in the gear head and the bearings were shot. Water entered the valve during water washing. The valve manufacturer said it was thinking about design modifications to correct the situation. Several users reported having the same or similar problem:

  • An operator of PCs inAlbertasaid his plant had an issue with valves closing on startup when they got to 87% open. Also, he sees valves floating around 0%.
  • Another user reported the same issue with the same machine.
  • Terminal board connection was said to be the issue with another unit.
  • An LM2500 operator said his plant had a vertically mounted fuel valve and that condensation of water in the fuel allowed contaminated water to accumulate in the valve. Valve was reoriented to the horizontal position and the issue cleared up.

LMS100 breakout

Session chair and discussion leader for theLMS100 sessions was Don Haines, facility manager, Panoche Energy Center, Firebaugh, Calif; session secretary, Jeanfils Saint-Cyr of Strategic Power Systems.

   Chairman Haines opened the meeting with a recap of last year’s major issues and his expectations for 2011. Hydraulic oil leaks were a top discussion point in 2010, he reminded, and most of those issues had been resolved with the OEM’s help.

   For 2011, Haines stressed training and elimination of operator errors as key goals. Operator training is critical, he said, and most of this activity should be accomplished in the early stages of commissioning. Qualified operators, Haines continued, contribute to success by identifying issues before they become problems.

   Remote monitoring by the OEM can help in this regard. Plus, feedback from the GE Monitoring andDiagnosticCenter, contributes to operator education. One plant using this service reported that theM&DCenteridentified a strut-tube crack in the exhaust end before it became problematic. The key indicator was a step-change increase in temperature at the “B” sump location. A package inspection revealed that a strut tube had cracked and a piece of it had blown out.

   Another “catch” noted during the discussion involved a fuel-gas meter. At this plant, the operational meter had been replaced with a recently certified meter that was indicating high fuel flow relative to normal fuel flow for a given load. TheM&DCenterreported this to the plant and the meter was replaced.

   The take-away from the gas-meter incident is that no plant should accept repaired or new parts or equipment without a QC check by qualified station personnel. Everything looks good in the box; you don’t want to accept on “looks” and find out later, when the part is needed to maintain engine operation, that it is unable to meet expectations.

   At a 7EA User Group meeting a couple of years ago, a presentation by the president of Gas Turbine Controls was straight and to the point in this regard. The subject was replacement/repaired circuit boards. The only foolproof way to test circuit boards, he said, was to install them in the control cabinet and operate with them. They can pass all shop tests but suffer damage during shipment or uncrating.

   Best practice: replace the operating control board with the refurbished board to verify the latter’s integrity. You can put the board removed in the storeroom with the confidence that it will work when needed.

   Fleet report card. Most attendees are interested in an overview of fleet statistics, in general to see how their plants stack up against the others. This is particularly true for a young fleet, like the LMS100. Recall that at the time of the 2009 meeting only five units were in commercial service and just a handful of users attended this breakout.

   By the 2010 conference, 17LMS100s were producing power at 10 plants in five countries. Thirteen of those units at six plants in three countries were represented inSan Diego. This year, 21 units were operating at a dozen plants in six countries and as many as eight machines were scheduled for commissioning or installation. The breakout inPalm Springshosted about three dozen users.

   Fleet operating hours through 2010 approached 63,000, starts exceeded 11,000. The high-time engine was just a few hours shy of 15,000.

   Fleet RAM (reliability, availability, maintainability) stats are presented below. They were compiled by Strategic Power Systems based on the 16 LMS100s reporting data through the company’s ORAP® system for the period January 2008 through December 2010.

  • Availability, engine only (including the intercooler), 94.7%.
  • Availability, simple-cycle plant (including engine, generator, and station equipment), 87.7%.
  • Reliability, engine only, 97.8%.
  • Availability, simple-cycle plant, 94.6%.

   Starting reliability as reported by the OEM was 97.8% based on a 12-month rolling average through December 2010. The OEM’s expected goals for a mature product—defined as 100,000 total service hours—is 99.2% reliability, 97.1% availability.

   The meeting notes, compiled by SPS’s Saint-Cyr, are voluminous and based primarily on GE’s fleet-wide findings between the 2010 and 2011 conferences. Anyone having supervised O&M activities through the adolescent years of a new turbine model is aware of the lengthy punch list that must be worked through before the engine achieves maturity and performance is relatively predictable.

   Many issues discussed inPalm Springsalready have been resolved and others will be resolved shortly. The OEM’s valuable contribution to the collective knowledge through its presentations cannot be overstated. For most of the three dozen or so items reviewed, GE personnel provided background on the issue, progress in the RCA if applicable, product improvements implemented or being considered, recommended field action, etc.

   Details are available to LMS100 owner/operators at www.wtui.com and on the OEM’s customer website.

   A presentation by the user with the high-time engine pointed to several punch-list items demanding attention. These included the following:

  • Tubesheet warpage in air inlet house. The problem was traced to poor manufacturing quality, substandard welds in particular.
  • Foreign object damage (FOD) caused by deterioration of the inlet screen at the bellmouth has proved to be a bigger problem than expected because of inaccessibility.
  • Intercooler seal deterioration at 4000 hours required removal of both the upper and lower seals. Speaker reported that the OEM was working on a design change.
  • Hot spots on theIPTframe.
  • Deterioration ofHPCmidspan support shrouds.
  • Combustor crack at 14,500 hours.

   The speaker summed up his plant’s experience to date this way: 23% of the outages were minor and package-related; 25% of the outages were major and unplanned; 52% of the outages were attributed to logistical, transport, and tooling issues. Regarding the relatively high percentage of logistical and transport issues, note that this plant is located inSouth America.

   Lessons learned. Here’s a sampling of issues/lessons learned during the group discussion:

  • NOx water stop valve intermittent failure. Corrective action: Replaced solenoid.
  • VSV hydraulic pressure failure. Unit trip at 15 MW was attributed to gross error in the VSV demand versus feedback signal. It was found that the VSV hydraulic supply pressure decreased to the point that the VSVs would not follow demand asHPCpressure increased. User kept the engine in operation by changing out the defective regulator in the VSV Womack hydraulic-pressure manifold with one from a used manifold until a new regulator was available.
  • Balance-piston air tubing failure. Tubing was installed upside down. One of the challenges of installing, commissioning, and operating a new model of gas turbine is the lack of experience of all involved. Often, no one is sure of the pathway to success until the engine is operated; learning by trial and error.
  • NOx–water filter differential-pressure lines were installed improperly. Suggested action: Hand-trace tubing to ensure proper installation.
  • Some sites reported leaks in fuel-nozzle hoses and the presence of high combustible-gas levels in the package. Suggested action: Test hoses during maintenance.
  • Control-cabinet cooling systems have been problematic. At least 15 failures have been reported fleet-wide. The discussion provided attendees a procedure for a nominal 10-minute load survey that can identify defective cooling systems. This is important to do because loss of cabinet cooling can adversely impact reliability. CCJ