WTUI: A changing of the guard

Vice President Mike Raaker shocked the largest lun­cheon audience in the history of the Western Turbine Users Inc (WTUI) Tuesday, April 8, when he announced that Jim Hin­richs was retiring as pres­ident of the organization after 17 years at the helm. Hinrichs, a man of relatively few words was true to form: A few “thank-yous,” a short good-bye, and he was gone. There was no curtain call.

Only minutes earlier, Hinrichs had informed the group that both Secretary Jack Dow and his wife, Gae, the conference coordinator, were retiring.

Jon Kimble, a former director, was elected to fill Hinrichs’ oversize presiden­tial shoes. Kimble’s day job is at Wellhead Electric Co, which owns and operates six powerplants in Califor­nia. He is only the third president in the history of WTUI. Other officers and directors of the group are identified in Sidebar 1.

1. Western Turbine officers, directors

President: Jon Kimble, Wellhead Services Inc
Vice Presidents:
Mike Raaker, Raaker Services LLC
Bill Lewis, PPL Edgewood Energy
Jim Bloomquist, ChevronTexaco
Secretary: Chuck Casey, City of Riverside
Treasurer: Wayne Kawamoto,  Corona Energy Partners Cogen­eration Plant
Directors:
Jim Amarel, Energy Services Inc
Mark Breen, Wood Group Power Operations Inc
Alvin Boyd, City of Pasadena
David Merritt, GWF Energy LLC
Frank Oldread, CAMS Juniper LLC
Mike O’Brien, Calpine-Kennedy Operators Inc
Harry Scarborough, MMC Energy North America LLC
Supporting Member:
Wayne Feragen, webmaster, E I Colton LLC

According to VP Raak­er, who also serves as the organization’s “official” historian, WTUI was incorporated in California in 1990. Hinrichs became presi­dent about a year after that. The first meeting of LM users (four plants were rep­resented) took place in 1980; the ad hoc group met regularly until incorpora­tion. Raaker and Treasurer Wayne Kawamoto are the only remaining officers/board members who have been active in the organization since it was formalized.

The 2008 Conference and Exhibition at San Diego’s Town and Country Hotel, April 6-9, set an all time attendance record with 831 participants. It broke the record established just last year when 725 peo­ple came to the event in Phoenix. The increase in attendance reflects both the growing fleet of engines supported by the user group and the value of its program content.

Two more impressive stats from the 2008 meeting:

  • The exhibition hall allowed the users to visit with 121 companies.
  • Twenty-one countries were represented at the meeting: United States, Canada, Scotland, New Zea­land, Belgium, India, Den­mark, Malaysia, Tanzania, Sweden, The Netherlands, Ecuador, Italy, Germany, United Kingdom, Brazil, Chile, Colombia, Spain, Brunei, and Japan.

Recall that the Western Turbine Users is a membership organization of LM2500, LM5000, LM6000, and LMS100 aeroderiv­ative gas-turbine (GT) users, third-party parts suppli­ers, and services providers. 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—simple cycle, cogeneration, and combined cycle—using these engines.

Owner/operators of LM engines 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 at least thousands of dollars in maintenance and/or operations. Comradery is a defining characteristic of this group so the interchange among user delegates is especially good and ideas flow easily.

The Western Turbine meeting is a challenge for an editor to cover because so much is going on all the time. For example, the core of the conference is a series of five breakout sessions totaling more than eight and a half hours for each engine type—two sessions open to all conference attend­ees, three user-only. The breakouts for each LM engine are conducted in parallel.

Likewise, many of the prepared technical presentations in the after­noon of the second day (Tuesday) are conducted in separate rooms in the same time slot.

Users responsible for multiple engine types are challenged like the editors by wanting to be in two or three places at the same time, but the WTUI officers and board of directors have solved that problem by pub­lishing a proceedings—certainly the most comprehensive package offered by any GT user group.

Each user attendee receives a CD with detailed presentations on maintenance procedures and repair methods—including excellent pho­tography—prepared by the depots for the breakout sessions. Those, togeth­er with the actual session minutes compiled by President/CEO Sal Del­laVilla and his colleagues at Strate­gic Power Systems Inc, Charlotte, are sufficient to satisfy the information needs of virtually every attendee.

This report is divided into four major sections: introduction, break­out sessions, technical presentations, and depot profiles. Note that there are now five depots participating in the Western Turbine meeting: Trans-Canada Turbines (TCT), Calgary; MTU Mainte­nance Berlin-Brandenburg GmbH, Ludwigsfelde, Ger­many; Air New Zealand Gas Turbines (ANZ), Auck­land; Avio SpA, Rivalta di Torino, Italy; and IHI Corp, Tokyo, Japan.

Warmup

WTUI meetings officially start on Monday morning and run through noon Wednesday; unofficially they start early Sunday morning when the golfers tee off for the annual Western Turbine Tournament. A few others opt for tennis at noon; the majority “do” brunch. These leisure activities are a great warmup for a busy week, allowing veterans and newcomers to get acquainted before the sessions begin.

Unlike most other groups serv­ing GT users, WTUI conducts one or more orientation sessions for new­comers; these are held after Sunday’s fun events. Typically, one-third to one-half of the user attendees at an annual meeting are first-timers and many are unfamiliar with one or more engines supported by the group. Almost certainly, newcomers find themselves lost in the alphabet soup of acronyms this group uses in casual discussion (Sidebar 2). Morse code might be easier to understand.

In San Diego, Board Member Frank Oldread of CAMS Juniper LLC, Bakersfield, Calif, con­ducted the new-user orienta­tion and LM engine famil­iarization from 4 pm until shortly before the exhibition opened at 6.

Users come to the meeting with the expectation of tak­ing back to their respective plants ideas that will improve safety and/or performance and facilitate maintenance. That’s tough to do unless you’re up to speed on engine components/parts and know your acronyms. Oldread preps you on Sunday so you will be able to take meaningful notes and participate confidently in the discus­sion as soon as the meeting opens.

2. Acronyms to remember

AGB—Accessory gearbox (also called the transfer gear­box)
CPLM—Critical-parts life management
CFF—Compressor front frame
CRF—Compressor rear frame
DLE—Dry, low emissions combustor
DOD—Domestic object damage
FFA—Front frame assembly
FOD—Foreign object damage
GG—Gas generator (consists of the compressor and hot sections only)
GT—Gas turbine (consists of the gas generator pieces with the power turbine attached)
HGP—Hot gas path
HPC—High-pressure compressor
HPCR—High-pressure compressor rotor
HPCS—High-pressure compressor stator
HPT—High-pressure turbine
HPTN—High-pressure turbine nozzle
HPTR—High-pressure turbine rotor
IGB—Inlet gearbox
IGV—Inlet guide vane
LM—Land and marine
LPC—Low-pressure compressor (not on LM2500; just LM5000 and LM6000)
LPCR—Low-pressure compressor rotor
LPT—Low-pressure turbine
LPTR—Low-pressure turbine rotor
LPTS—Low-pressure turbine stator
NGV—Nozzle guide vane
OEM—Original equipment manufacturer
PT—Power turbine (turns a generator, pump, compres­sor, propeller, etc)
PtAl—Platinum aluminide
RCA—Root cause analysis
SAC—Single annular combustor
SB—Service bulletin
SL—Service letter
TAT—Turnaround time
TBC—Thermal barrier coating
TGB—Transfer gearbox (also called the accessory gearbox)
TMF—Turbine mid frame and thermal mechanical fatigue
VBV—Variable bleed valve (not on LM2500; just LM5000 and LM6000)
VIGV—Variable inlet guide vanes
VSV—Variable stator vane

Oldread really does start at the beginning. First slide is an elemen­tary conceptual drawing of a GT. All it tells you is that there’s a compres­sor, combustion section with burner and fuel injector, turbine section, output shaft, and exhaust duct. Next you learn that LM stands for land and marine—GE’s powerplant, plat­form, and marine versions of flight engines. For example, the engine for the LM2500 is based on the engine used in the L-1011, the one in the LM6000 is based on the engine for the Boeing 747ER.

Looking at cutaway drawings of the three engines fully assembled the machines look pretty simple, but then Oldread breaks out the assem­bly drawings showing how the dozen and a half (or so) principal engine components fit together. These com­ponents include front frame, com­pressor stator, compressor rotor, gearbox, high-pressure turbine rotor, rear frame, etc. To sit in a breakout session without having had a primer like this, you’d be lost five minutes into the discussion.

After digging into the details of key components (for example, the number of stages in the compressor for each machine), Oldread explains where temperature, pressure, and speed pickups are located, and pres­ents an overview of performance-enhancement auxiliaries: STIG (steam injection for NOx control and power augmentation), water injec­tion for NOx control, Sprint for power augmentation, and DLE (dry, low emissions) combustion systems.

Oldread then went through the organization of the engine technical manuals. He showed the newcomers how to find the engine service bul­letins—putting emphasis on deter­mining the applicability of the SBs to the user’s engines. Next, Oldread explained the planning information for SBs, including the compliance, priority coding, and cost informa­tion.

Hinrichs opens meeting

When Hinrichs looked out at the sea of members gathered for the opening session, he knew this was the last time he’d be doing this, but nobody else did—at least no one who was going to tell anyone else. You have to wonder what he was thinking. Perhaps, “How did we come this far this fast?” There were 40 attendees in 1990 and more than twenty times that number in 2008.

The opening general session start­ed promptly at eight on Monday morning and covered much the same ground as had for the last several years: introduction of officers and board members, review of conference agenda and social events, election of new board members, treasurer’s report, etc. Hinrichs kept this por­tion of the program right on schedule so the ensuing technical sessions packed with information prepared by the depots were not short-changed on time.

Raaker closed out the plenary ses­sion with an entertaining historical perspective of WTUI and the energy industry in general covering the last quarter of a century.

Engine breakout sessions

LM2500 breakout

Session chair and discussion leader for the LM2500 sessions was John Baker, O&M manag­er, Bethpage Energy Center (Calpine Corp), Hicksville, NY. The LM2500 depot pre­sentation was led by John Leedom, ANZ Gas Turbines, with support from Nico Brademann and Christian Poppel of MTU Maintenance.

Leedom began by review­ing the agenda:

  • Capabilities of the independent depots.
  • Engine fleet statistics.
  • Recent service letters (SLs) and service bulletins (SBs).
  • O&M Manual and Industrial Repair Manual (IRM) limits.
  • Depot findings.
  • Life management of critical parts.
  • Field service maintenance.
  • Engine preservation, handling, and transportation.
  • Expected maintenance intervals and aftermarket services.

One of the first things mentioned by Leedom for the benefit of first-timers was that the OEM does not mail hard copies of the SBs to users; access to this information is through the GE website. He suggested to users in attendance that, if they had not already done so, they should request from their service represen­tative the access disk required for downloading the SBs and register on the website.

As is typical at most GT user group meetings, the moderator will start at the front end of the machine and work his way back through the exhaust section asking if anyone has questions or comments on, or issues with, the major components along the way.

Baker began with the compressor front frame (CFF, Sidebar 2 trans­lates acronyms used throughout this report), gearboxes, and starting sys­tem. No major issues were identi­fied. In the HPCS, however, one user spoke of leakage at Stage 15/16, with the VSV identified as the root cause. Another participant said one of his units had a CRF with a cracked noz­zle. Metal fatigue was identified as the culprit and the OEM replaced the nozzle. Then a problem was found in the diffuser and that too was fixed.

There were a few thoughts on the combustor. Perhaps the most impor­tant was that coating had spalled on one machine, passed downstream, and caused several turbine blades to fail. Another user with a dual-fuel engine said he changes-out combus­tors during both the spring and fall outages to maintain high reliability. An attendee offered that users who choose to run with the OEM’s hot-sec­tion extended-life hardware can get a letter from GE that authorizes plant personnel to run the machine hotter.

Discussion moved to the turbine section with a user reporting that a crack in the TMF of a base-load machine was identified during an HGP inspection. He said the OEM recommended a vibration analy­sis, stating that acoustics can be a major issue during startups and shutdowns.

A navy participant talked about the value the military saw in LPTS inspections. That got shoreside per­sonnel thinking a formal procedure for LPTS inspections in land-based engines should be developed. No one could remember a significant prob­lem occurring in this section of the machine, but perhaps the industry has just been lucky.

Users debated the OEM’s recom­mendation to conduct an ultrasound inspection on the TRF thin flange. They believed the bigger failure risk was bolts coming loose and doing major turbine damage.

LM5000 breakout

Session chair and discussion leader for the LM5000 sessions was Jim­mie V Wooten Jr, turbine mainte­nance supervisor, CAMS Juniper LLC, Bakersfield, Calif; recording secretary, Bob Steele, engineering director, SPS. More than 30 users attended the two open sessions con­ducted by the depots on the first day of the conference, a significant increase over 2007—this despite con­tinued attrition of operating engines. Recall that GE no longer builds the LM5000 and some owners have opted to replace their machines with an LM6000 rather than fix them.

ANZ Gas Turbines’ Chris Martin and MTU Maintenance’s Peter Kil­ian teamed up to make the depot presentation, which began by review­ing fleet status: 61 units capable of operating, plus nine user spares, 14 GE lease engines, and four machines available for sale from the OEM. The total number of engines in the fleet today, 88, is down eight from last year.

A review of applicable service bul­letins and service letters was next. As mentioned in the previous section reviewing the LM2500 breakout ses­sions, SBs are available only through the OEM’s website; copies are no lon­ger printed and mailed to customers. SBs released since the 2007 meeting are listed in the LM5000 Breakout Session Book developed by the depots and distributed to users who attend­ed the session.

These handouts are extremely valuable at the deckplates level. Reviewing them on the WTUI web­site is not nearly as productive as sit­ting in a room with experts who walk users through the content, thereby allowing you to add complementary notes.

A clarification for owner/operators who may have been out of the room at the beginning of the first session: SB 209 is NOT optional as stated in the handbook; it must be performed. The option is whether to do the work in the field or at a depot.

Next, the differences between the guidelines presented in the Opera­tions and Maintenance (O&M) Man­ual and those in the Industrial Repair Manual (IRM) were discussed. An example helped to put the differences in perspective: The O&M Manual does not allow field repair of cracks in HPC rotor blades; however, the IRM allows the repair of cracks by depots—within well-defined limits of crack size.

Introductory topics complete, depot findings since the previous meeting then were discussed in detail, start­ing with the compressor and mov­ing back through the machine to the turbine section. Highlights are pre­sented below.

Low-pressure compressor rotor (LPCR):

1. Compressor fouling and the need to keep blades clean was the first topic. Online and offline washes at a frequency recommended by the OEM is critical to this effort. Failure to maintain blades in a clean condi­tion means expensive, time-consum­ing cleaning by hand during outages.

2. Discussion moved to the ero­sion-related effects of inlet fogging. Coatings are considered a possible solution, but it was reported that GE has not investigated their use to this point. Last year one user reported adding a coating to the spinner cone and to the leading edge of S0 blades. This year’s update, reflecting about 1000 hours of operation on the coat­ing, was not encouraging. The owner/operator said the coating was not “holding up.”

3. A Stage 0 blade failure was reported—the first in many years. Investigator said it appears limited to offshore platform applications and that the cause most probably corro­sion pitting initiated by salt in the sea air. GE was said to be working with platform operators to address corrosion in the early stages of the compressor; coatings are being con­sidered.

4. Locked blades are conducive to LPC vibration and CFF cracking. Vibration that cannot be addressed with trim balancing is a sign of locked blades. If necessary, blades can be cleaned and restacked in the field to correct the problem. Experts say a vibration velocity of 0.2 to 0.3 inches per second (ips) is normal for the LPC. If you are seeing 0.5 ips, blades may be locked. Higher veloci­ties can contribute to cracking of the front frame.

Front frame assembly (FFA):

1. Cracks in the FFA were a head­line item again as they have been for the last several years. Cracking was reported on both the inner and outer radial struts and the webbing—or weldment area. Three cracked frames had been found in the six months before the meeting. Users asked if the cracks are more prevalent for some reason or if they’re being found because inspections are more rigor­ous. There was no definitive answer.

Mention was made of cracks “com­ing together” and material being lib­erated. There also was one report of a crack occurring in the vent strut and causing an oil leak.

Lead times for repairs are long, typically 40 days for the work itself; expect an investment of two months including removal, reinstallation, and transportation to/from the repair facility. Regarding repair procedures, “green” welds are not longer permit­ted; crack repairs require full heat treatment.

GE has made some changes to remove stress risers. The first of these mods has been in service for about three years without need for re-repair.

2. There is an improved seal to cor­rect disbonding of the stationary air/oil seal. Installation requires replac­ing both the stationary and rotating seal segments. Cracking of the No. 3 bearing stationary air/oil seal has been experienced on only two engines in the last three years.

3. It is acceptable to run without the SPC Stage 4 bumper strip if dis­bonding occurs.

Air collector:

1. Air-collector distortion is anoth­er hold-over item from previous meetings. A SB is in preparation to provide guidance on modifications to alleviate the problem.

2. Replacement of “elephant ear” brackets was mentioned as one way of addressing wear of forward engine mounts. It’s possible to do onsite, but engine realignment is necessary.

Inlet gearbox:

1. Migration of the roller-bear­ing inner race has occurred. Note that this is not the same thing as the duplex bearing discussed at last year’s meeting. No repair procedure for LM engines is available at this time.

2. There is a new procedure for bonding the oil-pump slinger that applies adhesive around the rotor. Access the depot notes for guidance.

High-pressure compressor rotor (HPCR):

1. There are two different con­figurations for the HPCR—one with a spool shaft, the other with a rear shaft. The second is of interest here. Fretting can occur on the bore of rear shaft and, if significant, scrapping of the shaft may be necessary.

2. Disbonding of the HPCR Ves­pel® strip has been reported.

HPC blades. Cracks in the com­pressor-blade root area—and in extreme cases missing blade roots—have been attributed to “tip clang” on Stages 3 through 5 because of stall or trip conditions. OEM’s recommen­dation is to replace R3 through R5 blades during depot visits to prevent failures. There is no official interval limit; GE can assess your situation and suggest when a depot visit is should be made.

HPC stator. Discussion focused on the need to carefully inspect vari­able stator vanes (VSVs) located behind the bridge connections. Depot representatives said that if a lever arm is bent 4 deg or more, one stage of compressor blades forward of the bent arm and two stages of blades downstream must be replaced. Gaug­es for measuring the degree of bend­ing experienced by lever arms are available through the OEM.

Dirt can exacerbate VSV prob­lems, contributing to pin and bushing wear. A user reported replacing VSV bushings every 18 months.

Compressor rear frame (CRF):

1. Several SBs relate to the CRF mid flange. For example, SB 204 introduces a mid-flange replacement repair. It is optional, but highly rec­ommended; if not implemented, peri­odic onsite inspections are required. Note that SB 197 and SB 203 still apply even if SB 204 is implemented.

2. GE has reduced the vibration limits for the LPC although it has not yet lowered the levels for the HPC.

3. CRF oil-tube wear and cracking have been experienced at strut exit areas. Oil leaks have resulted. SL 5000-06-01 recommends replacement of all oil tubes (supply, scavenge, air) and brackets at overhaul.

The combustor discussion essen­tially was confined to information contained in the depot handout—an invaluable reference for plan­ning outages and conducting main­tenance. One additional note: MTU Maintenance said that it has coated the bridge area of the dome heat shields to prevent burning.

HPT first-stage nozzles:

1. Monitoring of temperature spreads can help avoid first-stage nozzle burning. Experience indi­cates that the worst wear some­times appears in the cooler locations. Thinking is this may be caused by water injection.

2. A “quick” flow test can be per­formed on first-stage nozzles using GE tooling.

3. Latest nozzles have a new cooling pattern which currently is undergoing a complete in-service evaluation.

HPT second-stage nozzle assembly:

1. Rub damage caused by blade tips contacting the first-stage shroud is typical, with greatest evidence of rubbing in the 6 o’clock position. Upgrade of the shroud material to Rene 5 as suggested in SB 177 has addressed some of the problems. While some erosion still occurs, there are no known cases of shroud drop.

2. Second-stage shrouds were said to be relatively reliable.

3. Cracking of the air-filter screen required to support the HPT outer seal was discussed next. Occasional­ly, cracking is so severe that material is liberated; however it is not a threat to damage the engine.

4. Cooling tubes for the second-stage nozzles often are found turned and partially disintegrated, or miss­ing retaining hardware. This topic is aired at almost every WTUI meeting, but users do not find that such dete­rioration causes a loss of cooling flow or problems with the second-stage nozzles.

HPT rotor (HPTR). The two rotating knife-edge seals on the rear part of the HPTR aft shaft often exhibit heavy rub damage from con­tact with the cooling and vent seal in the forward part of the TMF C-sump. Full-load trips and high vibration are thought to contribute significantly to such wear, which if allowed to contin­ue unchecked could render the part unserviceable.

Turbine mid frame (TMF):

1. So-called “clocking” of the TMF liner has the potential for caus­ing engine failure. Experience with clocking pins is that they slow liner movement but have not eliminated the problem. Issue exists only with Hastek liners installed in mature engines; the newer HS188 (a cobalt-based superalloy) liners do not require pins because this material does not lose ductility like Hastek.

Important: G17, G18, and G19 liners are of HS188. However, when the J-seal mods were made (see next item) and part numbers updated to G20, traceability to material (Hastek or HS188) was lost. The depots can help you identify the liner material in your unit if unknown.

2. The J-seal has been of concern for a long time. Recall that it seals between the rear surface of the TMF aft outer flange and the front face of the mating flange on the LPT stator. SB 202 explains the new set-up for the J-seal based on the LM2500+; it has worked well with no issues reported to date.

3. Discussion on the TMF closed with mention of the bracket attach­ments on strut caps. Check them periodically to be sure they are not loaded or loose. A field replacement procedure is being developed for the strut caps.

Low-pressure turbine (LPT) stator case assembly:

1. Case cracks have been expe­rienced. When cracking occurs, the case must scrapped; it is not repair­able. A user asked why the cracking happened and hypothesized that it may have been caused by insufficient cooling of the case when steam injec­tion was off. His thought was that with bleed air being used to purge/prevent backflow from the turbine, the case could be subject to exces­sively high temperatures. No one could say for sure.

2. Users reported broken anti-rotation stops on LPT shrouds. Depot experts said that if only a few are broken, shrouds can be rearranged to prevent large gaps. If too many stops are broken, they should be repaired or the shrouds replaced.

LPT rotor:

1. A couple of years ago, fluores­cent penetrant inspection of a rotor disk by a depot revealed crack indi­cations between adjacent rim bolt holes. Low-cycle fatigue was said to be the cause. Problem was solved with a change in the manufacturing process. Talk to your depot if you have any questions regarding non-destructive examination procedures to verify disk health without rotor disassembly.

2. Users reported cases of tip shroud-lock wear.

Performance effects. Reasons for poor performance were reviewed. The depot notebook presents details. Oops: The effects of engine refurbishment in the presentation are for a CF6-50, so ignore the last two columns.

Engine vibrations are an on-going issue. Numerous SBs and SLs have been published to address it. However, vibration is manageable, with slow starts and careful cranking on shutdown being vital to achieving that goal. A presentation by the OEM included important details available only to attendees. If you’re feeling left out, be sure to attend the next meeting.

The critical-parts life manage­ment (CPLM) discussion brought the following points to light:

1. LPC, HPC, HPT, LPT, and pow­er-turbine rotors all are impacted by cyclic limits.

2. Only a couple of users indicated that they are monitoring critical-parts life. Perhaps some attendees saw a colleague with his or her hand raised and didn’t participate in the count. It’s difficult to believe that virtually everyone wouldn’t be doing this.

3. The fleet-leading engine was said to have compiled 150,000 hours of service at the time of the meeting.

4. Poor record-keeping and/or lost records—particularly those relating to the refurbishment of hot-section parts—have made it difficult for some users to figure out where their engines are with respect to parts life. But diligent record-keeping from this point forward can eliminate that unknown in only a few years.

User-only sessions are infor­mative as well as therapeutic. Only behind closed doors can you get the insider’s view of how well vendor fixes really work, if upgrades truly are meeting expectations, and if the nagging problem you have really is unique in the industry as the OEM claims. Here are a few sound bites extracted from about three hours of user-only discussion:

  • FOD screens. A couple of users reported cracking of their screens. One said the epoxy called for in the SB is no longer available com­mercially.
  • LPC rotor. One participant echoed something said in the depot ses­sions—to be on the look-out for locked blades.
  • FFA. Cracks have appeared much earlier in the life of the unit than the OEM said, and they are big enough to be seen with the naked eye. Only one shop for repairing FFA cracks as noted in the depot session and turn times are long.
  • LPC stator, Stage 4. Disbonding of Teflon on the air/oil seal was noted and discussed.
  • VBV. One user said that actua­tor seals were missing when his engine came back from the shop. The group questioned why they are there if not required.
  • HPC. VSV bushings are replaced every 18 months by one operator.

Lever arm measurements always indicate wear, so bushings are just replaced regularly to avoid blade issues.

Another site experienced new and significant vibrations after implement­ing SB-185 during a major overhaul. The No. 3 bearing was destroyed. Depots said the threadless air duct was the source of the vibrations, which spiked to about 4 ips at startup and during power-up/down of the unit.

  • Combustion system. One user reported getting 50,000 hours on combustors with STIG, anoth­er only 25,000 hours with water injection.
  • HPT, Stage 2 nozzles. Cooling-tube twisting noted in the depot sessions continues to occur, but doesn’t adversely affect operation. Users questioned the need for cooling tubes, but the OEM has not offered a real answer.
  • TMF crack appeared after only a couple of thousand hours of opera­tion on a newly overhauled engine. Excessive air leakage at the struts caused high package tempera­tures. There was much discussion on this topic as attendees dis­sected the machine and offered their opinions as to why the crack­ing occurred. Where, other than at a Western Turbine meeting, could you gain access to this many knowledgeable people at one time in one place? And you’re not pay­ing a consulting fee!
  • AGB. Excessive wobbling of the accessory gearbox was the underly­ing reason for a front frame repair. An accelerometer was installed. It indicates that some wobbling con­tinues to exist. A thorough analy­sis has not yet been done.
  • Power turbine. Here’s a useful idea for owner/operators troubled by high lube-oil temperatures: Move the oil lines off the engine. Another user reported a small crack at the brazed joint for the oil supply tube that caused a fire, coking, and plugging of the scav­enge filters. The engine had been overhauled only 18 months earlier at a non-GE shop.

Overhaul intervals always stimulate meaningful dialog. One user with a spare PT and a Metal­SCAN system (Gastops Ltd, Otta­wa, Ont) operates its PTs 75,000 hours between overhauls—50% longer than the recommended 50,000-hr interval. Noted during this exchange was the need to order parts well in advance of any PT overhaul because they gener­ally are long-lead-time items and can adversely impact the critical path. Someone offered that if a PT is needed in a hurry, MTU Main­tenance had a spare.

  • LPT. Interesting case history for any powerplant sleuth: Crack­ing of the LPT case on a STIG-equipped package was reported by the owner. Depot doing the over­haul suggested vibration was the cause. Independent Bently moni­toring system said that was not the case; there was no evidence of vibration. If vibration wasn’t the cause, what was?

The site sleuths went to work and during their investigation they noted that steam flow to the GT varies with host demand. Consensus opinion was that crack­ing probably was caused by the thermal cycles that resulted from admitting up to 40,000 lb/hr of steam (cooling effect) and later turning it off (heating). No user in attendance was injecting more than that amount of steam and one mentioned that his unit expe­riences vibration when STIG is turned on. Yet another suggested checking machine alignment.

STIG generated lots of discus­sion. Most STIG units represent­ed reported having switched to flex hose for safety and to reduce the potential for interference. One user swapped-out all valves equipped with hydraulic actuators for air-actuated valves—not only the STIG valves outside the pack­age, but also the fuel valves inside the package. The STIG valves had been moved outside the package earlier in the life of the unit to mitigate operational problems.

LM6000 breakout

Session co-chairs and discussion leaders for the LM6000 session were Bill Lewis, Edgewood Energy, PPL Generation LLC, Ronkonkoma, NY, and Bryan Atkisson, Riverside Utili­ties, Riverside, Calif; recording secre­taries were Steve Giaquinto and Rob Grier of SPS.

Dale Goehring of TCT led off the depot presentations followed by Christian Czmok of MTU Mainte­nance and Steve Woodward of TCT; Minoru Hanakata of IHI supported the presenters. Note that TCT, MTU, and IHI are the only independent LM6000 Level 4 service organiza­tions authorized by the OEM.

The LM6000 track commanded the attention of the majority of con­ference participants, with just shy of 100 signing the attendance list for the two open sessions on the first day of the meeting and nearly 150 attending the closed user sessions. Both totals exceeded the number of participants in the LM2500 and LM5000 sessions combined.

By show of hands, there was a large percentage of first-timers involved in the LM6000 track—indicative of vibrant sales over the last few years. As Consultant Mark Axford reported at the Tuesday morning plenary, 17 LM6000s were bought by US power producers in 2007. They represented 800 MW of the 3400 MW of aeros sold for domestic use last year.

Goehring started the first of his three presentations with a statistical profile of the LM6000 market sector. The PA model totals 99 (26%) of 727 LM6000s produced to date for world­wide application; the PB, 1%; PC, 65%; PD, 8%.

Nearly one-third (238) of the LM6000s built were represented at the meeting—including 64% of the PA fleet, 18% of the PB fleet, 31% of the PC fleet, and 17% of the PD fleet. Note that four PFs have been built but none were spoken for in San Diego.

Here are some important fleet demographics for LM6000s repre­sented at the 2008 Western Turbine Conference:

  • NOx reduction: 64% rely on water, 10% steam, 14% multiple meth­ods, 5% DLE (dry, low emissions) combustion system, 4% other; 3% are permitted to operate without NOx control.
  • Performance enhancement: 65% Sprint™-equipped, 5% fogging, 18% fogging and Sprint, 12% other or none.
  • Lifetime management of critical parts: 34% of the units represented are doing this, remainder are not.
  • Operational profile: Standby (less than 100 hr/yr), 11%; peaking (100 but less than 2000 hr/yr), 34%; intermediate (2000 but less than 6000 hr/yr), 25%; base load (more than 6000 hr/yr), 30%.

The presentations by Goehring, Czmok, and Woodward followed the content of the LM6000 Breakout Ses­sion Book developed by TCT, MTU, and IHI in conjunction with repre­sentatives from WTUI—specifically:

  • Service bulletins (SBs) and service letters (SLs).
  • Engine fleet statistics.
  • O&M Manual and Industrial Repair Manual (IRM) limits. Note that depots follow the IRM to the letter. When maximum repairable limits of a part are exceeded, the part is replaced.
  • Depot findings.
  • Lifetime management of critical parts.
  • Field service maintenance.
  • Engine preservation, handling, and transportation.
  • Expected maintenance intervals and aftermarket services.

Czmok reviewed applicable ser­vice bulletins and service letters fol­lowing Goehring’s statistical analysis of the LM6000 fleet. As mentioned in the previous sections reviewing the LM2500 and LM5000 breakout ses­sions, SBs are available only through the OEM’s website; copies are no lon­ger printed and mailed to customers. SBs released since the 2007 meeting are listed in the depot handout dis­tributed to users during the session.

Attention was called to the com­pliance categories of SBs and to the timing codes. “Alert” category is very important because SBs so des­ignated may reflect safety issues. Timing codes typically are flexible. Attendees were urged to first check their engine serial number(s) against those specified on the SBs to be sure they’re applicable before any work is done. Note, too, that operational pro­file (standby, peaking, intermediate, base load) and fuel used can impact SB applicability.

Preliminaries complete, Goeh­ring returned to the podium and revved it up a notch as he began the second of three presentations sum­marizing significant depot findings during the year before the meeting. At the top of the list: HPT blades often are not meeting repairable lim­its in engines using water for NOx control. Other depot findings:

  • Inner seal wear on variable IGVs—it’s repairable but some­thing owner/operators should be aware of.
  • VBV seal/linkage wear continues to be an issue throughout the fleet. It can be repaired and should be inspected semi-annually.
  • Missing lockwires from HPC VBV actuator bolts/cap screws is anoth­er ongoing problem. Lockwires sometimes are difficult to see dur­ing field inspections but it’s very important to check their integrity. Fatigue failure is attributed to vibration from air flow in the air collector; liberated wire is known to cause impact damage. By show of hands, about 10% to 15% of the attendees said they checked for missing lockwire each semi-annu­al inspection.
  • HPC bushings. Inspection is rec­ommended every 12,500 hours, but a shorter interval is recom­mended. SB 213, which replaces the canceled SB 182, suggests use of a new multi-piece bushing which can rotate during opera­tion.

Woodward took over at the podium, giving Goehring a break. He tackled the problem of oil in the HPC rotor first, which Woodward said was becoming more prevalent. He researched old presentations by both the OEM and depots back to 2004 when this was not considered a major issue. The No. 1 seal typically was good for 20,000 hours of service at that time despite the expectation of 50,000 hours.

By 2006 seal life was a growing concern and a year later one depot saw leakage at 10,000 hours on three or four engines in a row. GE was said to be analyzing the problem and considering use a metal-spray shield with less chance of delamination. Users were told that a loss of oil may mean it’s in your HPC. Look for Tef­lon in the screens. If you see it, pull the engine and send it to the depot.

Czmok returned to the front of the room to talk inlet gearbox. Changing speakers frequently keeps the presenters fresh and the audience alert. Czmok asked, “Has anyone had inlet gearbox problems?” A few hands shot up. Prior to publication of SB 220, he said, inadequate lubrication often was the cause of gearbox problems.

Specifically, inadequate spline lubrication and relative motion between the horizontal gear shaft and HPC spline adapter cause wear that can result in core speed change or inability to restart. Wear can be identified by the presence of iron oxide sludge during a borescope inspection.

SBs 220 and 225 can prevent this problem. The first document, published at the end of August 2006, introduced an oil insert and new oil nozzle. The oil insert was selected based on successful experience on the CF6-80C and LM5000 engines.

SB 225 introduced a new spline adaptor that almost doubles the oil passage area to prevent wear particles from clogging the holes. It also made adjustments to reduce contact between spline teeth.

One user recommended fulfilling the require­ments of SB 220 because SB 225 requires disas­sembly of the engine to the modular level. It is cost-effective to implement only when related maintenance is required.

Czmok continued, addressing several other issues, including these:

  • B-sump oil leaks. Some units have experienced oil leaks in the CRF, resulting in smoking, frame coking, and/or lubricant loss. RCA find­ings: Loop clamp(s) breaking and/or sliding off wear sleeves. Latter allows clamps to wear through oil tubes. Correction requires engine removal.

A borescope inspection every quarter is rec­ommended. SB 154 provides guidance on remov­al and replacement of loop clamps on air tubes and the oil manifold. A new SB, No. 233, was scheduled for release at the time of the meeting. Speculation was that it will suggest the use of brazed-on strap clamps as an alternative to loop clamps.

  • HPT diffuser cracking. SL 6000-03-06 R1 explains how to perform a borescope inspec­tion to detect a cracked diffuser on PA and PC engines, which is recommended twice annually. Although all models are affected by HPT dif­fuser distress, there’s no way to inspect PB and PD engines in the field. SB 216 introduced an improved diffuser forged from IN718. Czmok expressed optimism that SB 216 has solved the cracking problem.
  • The G39 combustor was introduced in 2005 to eliminate the following problems identified in PA and PC engines: oxidation of the splash plate, wear of the fuel nozzle/primary swirler, and spalling of TBC from the secondary swirler (refer to SB 208 R2).

Many users, by show of hands, are still see­ing very significant wear on fuel nozzles/pri­mary swirlers. One with four LM6000s says he sees wear so severe at the 12 o’clock position nozzles must be changed after every 1500 hours of operation. Even tips with a hard carbide coat­ing apparently are not meeting expectations.

Cracked primary swirlers also are relatively common. Mention was made of G40, G41, and G42 combustors that may offer better results, but little commercial operating experience was available at the time of the meeting. Details available are presented in the LM6000 Break­out Session Book prepared by the depots.

  • DLE combustors. First genera­tion (version G01) has long heat shields, redesign (versions G02 and G03) as suggested by SB 174 has cut-back heat shields. Latter reduces wear.
  • HPT first-stage vanes made of DSR142, a high-nickel-content superalloy, typically exhibit dis­tress after 20,000 to 25,000 hours of service on engines with sin­gle annular combustors. If water injection is used for NOx control distress may be seen earlier—per­haps in as few as 12,000 to 15,000 hours.
  • Oxidation resistance and fatigue life can be improved by installing the OEM’s N5 single-crystal vane. A side benefit of the relatively new vane is that the casting was improved to address premature vibration/deflection of the inner leaf seal.
  • HPT first-stage blades have expe­rienced tip rubs accompanied by spalling of the TBC on the suc­tion side of the blade. This has occurred on blades made of both DSR142 and the single crystal N5. Recall that spalling exposes base metal to oxidation attack, there­by complicating repairs. Highest level of distress is found on blades in water-injected engines.

Prior to issuance of SB 191, when DSR142 was the material of choice, owners could expect low repair yields for blades in water-injected engines. Post SB 191, N5 seemed to meet planned hot-section intervals and was expected to have a high repair yield. A user asked what caused TBC failures on first-stage blades. Answer: TBC lost from the combustor hits the blades and chips off their TBC.

The latest SB, No. 215, intro­duced a more advanced single-crystal blade (N5+) with improved cooling of the tip and suction side. High repair yields are expected.

  • HPT second-stage vanes. Parts produced after issuance of SB 124 suffered TBC spalling as well as coating degradation and base-metal attack from oxidation. Parts produced after SB 163 was pub­lished also suffered spalling on the leading edge from thermal/mechanical fatigue and oxidation-induced coating degradation and base-metal attack. Both the post SB 124 and SB 163 parts typically serve for their expected lifetimes, but the latter perform better.

Goehring stepped to the podi­um for the third time to discuss the HPT first-stage disk. He talked about hook-bolt shear-type cracks and frac­tures that were traced to the reuse of bolts after engine overhaul. The depot manual now requires replace­ment of bolts/nuts if the nuts are removed after engine operation; also, HPT blades no longer can be changed out in the field.

A photo of an uncontained event that occurred on a CF6-80A engine—the aircraft equivalent of the LM6000—got everyone’s atten­tion, even those who had seen the pic­ture previously. Findings suggested a separation at the bottom corner edge of the aft dovetail slot. It is the sub­ject of SBs 177 and 210, which detail the inspection (former) and repair procedures (latter) recommended for all owner/operators.

Woodward relieved his TCT colleague Goehring to wrap up the session with a few comments on each of more than a dozen topics, as sum­marized below:

  • Coking of D/E sump drain has been experienced by a few users. Sump drain should be monitored periodically. Oil flow on startup and no oil flow at load is what you want. Attendees were referred to GE documents PB-LM6000-IND-0194 and SL 6000-05-03 R1 for inspection and maintenance guidelines.
  • Passive clearance control. Pre­mature hardware wear can occur within 2000 to 3000 hours of ser­vice. Worn bolts are known to cause manifold misalignment. SB 131 introduced new mounting brackets for the PA and PB mod­els to help prevent the problem. If necessary, however, the PCC sys­tem can be removed with no other effect than a small loss of engine efficiency.
  • LPT fifth-stage blades (PA engines). Woodward said blade failures have been experienced, although not very often. The sub­ject has not been given much attention in the past few years and users should be aware that the risks of old still exist. One way to address the issue is to upgrade the PA to PC/PD.
  • LPT mid-shaft. If tang cracks are identified, replace the tangs.
  • Lifetime management of critical parts. GE has identified cycling limits for major rotating parts—except airfoils—that could sud­denly fracture and threaten the structural integrity of the engine/package. The LM6000 Breakout Session Book shows a table of the 20 parts to track and gives equiva­lent cycles, limits, and factors. The OEM’s O&M manual is another place to find this information.

Users are responsible for tracking the cycles on their engine parts and for removing any parts that have reached their cyclic-life limits. Woodward said many own­ers are asking how they calculate the number of cycles on old units when the necessary data have never been collected. He said the depots can help with an estimate based on a given unit’s historical operating profile.

Other options: Charlotte-based Strategic Power Systems offers a cycles tracking service and the OEM was said to be adding cycles tracking to its control system logic.

  • Cleaning of the engine to remove deposits, fouling, etc was dis­cussed. Dry ice generally is used for this purpose; sandblasting can block cooling holes. Hand clean­ing of compressors sometimes is necessary to remove especially dif­ficult deposits.
  • Adhere to the fuel and water spec­ifications provided by the OEM to maintain your engine in proper operating condition. Woodward put up a photo that showed what can happen when you don’t burn the correct liquid fuel.
  • Keeping gearbox and bearing vent lines clear is vital to preventing an oil mist condition in the package. A photo showed what can happen if vents are not open.
  • Sensor calibration is a new service offered by the depots.
  • Importance of periodic flow test­ing of fuel nozzles was another discussion point. If out-of-spec nozzles can’t be corrected they are replaced.
  • Engine preservation. Operating regimes have changed and more units have significantly longer periods of shutdown today than previously. Suggestion was to review procedures to ensure prop­er layups. One useful reference was said to be GE Work Package 3011.
  • Engine handling. Be sure you’re using proper lift points when ship­ping engines in containers.
  • Transportation. Hire tractor/trail­ers with pneumatic air-ride sus­pension to prevent bearing dam­age.
  • Maintenance intervals. Materi­als distributed at the meeting provided valuable background on this subject—one more reason to have someone from your plant at every WTUI conference. See also SL 6000-05-03 R1.
  • Aftermarket services. Discussion included a review of maintenance and repair services offered by both the OEM and the depots. Users were encouraged to use GE-approved and substantiated repair procedures as well as genu­ine GE parts.
  • Depot experience. Woodward offered tips to owner/operators to ensure a rewarding depot experi­ence. At the top of the list was a face-to-face meeting between owner and depot representatives to discuss expectations and out­line the scope of work. Woodward also reviewed the information the depot needs on your components/parts to assure proper repairs and a successful overhaul, as well as what reports you can expect from the depot and how often.

The Tuesday user-only ses­sions were devoted to presentations by the OEM that covered many of the same topics addressed by the depots the day before, plus others. The value was that it gave owners and operators the opportunity to ask GE questions directly. Note that the GE presentation is available at www.wtui.com for registered members of the user group.

Dan Harmon started the day by outlining the agenda, discussing SBs issued over the last two years, reviewing tracking of critical parts and how important that was, identi­fying LM6000 repair resources, etc.

Bob Pearson followed Harmon with background on impor­tant recent issues, results of analytical work thus far, steps users can take to miti­gate the problem, etc. Sub­ject areas included Sprint on-engine air-manifold distress, CRF oil manifold leaks, LPC/LPT coupling nuts, SAC G39 combustor, motor control center, 11th-stage check valves, outer-band oxidation on HPT second-stage nozzles, high-pressure water injec­tion system. Pearson’s presenta­tions were in-depth and generated many questions. Answers generally were to the point and thorough.

GE’s Matt Eisert then updated the group on the company’s service programs designed to help users reduce emissions while improving efficiency, maintainability, reliabil­ity to maintain a competitive advan­tage in today’s challenging operating paradigms.

Last session. On Wednesday morning, the last user-only session featured a presentation by Dale Reed, Reed Services of Wyoming Inc, on borescope inspection techniques for the LM6000 and recent findings. He covered inspection of HPC splines and HPT diffusers, HPC bushing wear, combustor life, VBV bleed-door hinge wear, D/E sump coking, PCC forward mount bolts, B sump clamp wear, and the HPT. If you have concerns about any of these issues, access Reed’s presentation through the Western Tur­bine website.

Reed’s presentation was of particular inter­est to users who try to do their own borescope inspec­tions. He explained how he inspects certain components and showed applicable pictures to provide attendees a frame of reference for their work. Among the components highlighted were these: fuel nozzle No. 5 primary bore, venture second­ary swirler area, combustor dilution holes, HPT first-stage nozzle sup­port, seal support, and HPT diffuser.

Special presentations

No Western Turbine conference pro­gram would be complete without spe­cial presentations on subjects beyond the scope of the engine breakout sessions. Houston-based consultant Mark Axford made the first of these on Tuesday morning. His subject: Gas turbine worldwide sales in 2007. A summary of Axford’s comments is provided in Sidebar 3.

There were five special technical presentations on Tuesday afternoon. Reports on the simplified combined cycle, inlet air filtration, and erosion resistant nano-coatings for com­pressor blades were conducted in parallel in the 3 to 4 pm time slot; GT biofuel experience and genera­tor partial discharge followed from 4 to 5 pm.

Wednesday morning DellaVilla updated the group on fleet perfor­mance (Sidebar 4), GE’s Marc Horst­man reviewed operational experience with the LMS100, and Jim Amarel of Energy Services Inc talked about dual LM6000s driving a single gen­erator in Europe.

John Redding, senior VP, Advanced Power Projects Inc, Fre­mont, Calif, told attendees that sim­plified combined-cycle (SCC) technol­ogy is an easy and inexpensive way to lower the heat rate and increase the capacity of gas turbines. He presented compelling data on effi­ciency and capacity increases that a SCC upgrade offers simple-cycle LM2500+ and LM6000 engines. For details, access www.combinedcy­clejournal.com/archives.html, click 4Q/2007, click “GT upgrade technol­ogy promises more power at higher efficiency, lower emissions” on the issue cover.

David Brumbaugh, founder of DRB Industries LLC, Broken Arrow, Okla, delivered his popular “Intro­ductory Short Course on Industrial Filter Design and Applications.” Brumbaugh brought along filter and media samples to amplify the pre­sentation. Attendees could see them close up at the DRB Industries booth on the exhibition hall floor. For details, access www.combinedcy­clejournal.com/archives.html, click 2Q/2007, click “501D5/D5A Users” on the issue cover and scroll to sub­head “Have filter, will travel.”

Green fuel

Green is in and powerplant owners are scrambling to be sure they’re viewed in positive light. Burning bio­fuel is one option under consideration in many board rooms. This may well be a passing fad, but it’s important to come up to speed on this alternative energy resource so it can be discussed intelligently in regulatory hearings and other public forums.

Matt Eisert, who was on hand to participate in GE’s user-only aero technology sessions on Tuesday morning, did double duty by speak­ing about his company’s experience with biofuels Tuesday afternoon. Eisert has participated in several industry meetings recently and does an objective job discussing the pros and cons of green fuels.

The first thing users must learn is the language of biofuels. Eisert said that bioethanol and biodiesel are defined in many ways and come from a variety of sources. Always get written clarification to verify the composition of any fuel being discussed, he added. Biofuels com­monly refer to a blend of fossil and renewable fuels. For example, E10 is a 90/10 mixture of gasoline and etha­nol; B85, 15% petroleum-based diesel and 85% biodiesel. Eisert focused on pure biofuels at the Western Turbine meeting—that is, E100 and B100.

Biodiesel is made from vegetable seed oils—such as soy, rapeseed, palm, etc. A typical process begins by extracting oil from the seeds and mixing it with rendered fat/tallow to get the desired fuel properties. Meth­anol is added in the presence of a catalyst (so-called esterification) and methyl estersglycerine (biodiesel) is separated from the product stream.

For every 100 lb of seed oil, the process requires 10 lb of methanol to produce 90 lb of biodiesel and 10 lb of glycerol. Eisert put up a slide that showed how many gallons of biodiesel on average can be extracted from oil-bearing vegetation grown on one acre of land. Some examples: soybeans, 50; sunflowers, 100; palm, 600. Important to note is that corn is not used in the production of biod­iesel. Rather, corn, sugar cane, and cellulosic feedstocks are fermented to produce bioethanol.

But just because you can make biodiesel doesn’t necessarily make it a practical fuel option. At a typi­cal heat content of 118,300 Btu/gal, an LM6000 peaker operating 6 hr/day for one month would consume about 450,000 gal. If the fuel were made from soybeans, you’d need a 9000-acre harvest to run the GT for a month.

The bottom line: Biodiesel is eco­nomically viable today only if it is eligible for tax credits under your state’s Renewable Portfolio Stan­dard. And to figure that out, you’ll probably have to hire a consultant.

Fuel quality is another important concern. Eisert noted that a 2006 nationwide survey of B100 biodiesels by the National Renewable Energy Laboratory revealed that 59% didn’t meet the applicable ASTM D6751 specification. Plus, about half of the samples did not meet the GE spec for sodium + potassium (1 ppm max) and a few did not meet the OEM’s calcium spec of 2 ppm max.

3. Axford reports banner year for GT orders

A special presentation by Consultant Mark Axford on the state of the gas-turbine (GT) market was integrated into the plenary session on Tuesday morning. Axford, an expert on aero engines in power-generation service, heads Axford Consulting LP, Houston. His slides reflected a banner year for GT sales in 2007 and forecasted a slight drop in orders for 2008 compared to last year—5% in the US, 10% for the rest of the world.

Orders worldwide for GTs larger than 10 MW grew by 44% from the 48,827 MW booked in 2006 to the 70,122 sold last year (frames accounted for 61,715 MW, aeros 8407 MW). The sharp increase in market activity, Axford said, was the result of an extraordinary number of orders from countries in the Middle East (pie charts). Interestingly, GT orders placed by US power producers dropped by 12% last year to 5801 MW from 6598 MW in 2006. Anoth­er fact worth noting is that since 2003, the Middle East has ordered three times as much GT capacity as the US.

In the under-60-MW sector of the global market, frame capacity relative to aero capacity grew slightly from 2006 to 2007. Two years ago, aeros gar­nered 60% of the capacity, last year 57%. Traditionally (2003-2005), frames and aeros shared this market segment about equally, but in 2006 aeros made a sharp gain against frames. The pop­ularity of the LM6000 is one possible reason for this. To illustrate: North American power producers purchased 17 LM6000s in 2007.

Axford dissected last year’s US orders this way:

  • More than half of the GTs ordered for the US market (59%, 3423 MW) are slated for simple-cycle peak­ing service; remainder are for combined cycles (41%, 2378 MW).
  • Breakdown by engine capacity is as follows: Machines rated between 10 and 25 MW, no orders; 26-55 MW, 2024 MW; 56-125 MW, 888 MW; over 125 MW, 2889 MW (50% of the total capacity purchased).

Yet another concern is the com­patibility of biodiesel with standard LM6000 components and materi­als. GE offers a kit that enables combustion of this alternative fuel. It includes new gaskets and seals, for example. Also be aware that the lower heating value of biodiesel com­pared to petroleum-based diesel may make it necessary to install a larger fuel pump.

While bioethanol can be burned in GTs it appears less practical than biodiesel because of its much lower heating value (nominally 78,000 Btu/gal). Bioethanol is somewhat similar to naphtha and would require an entirely new fuel skid. Plus, there are lubricity and other issues to deal with—one of the latter is the need to start on gas and then switch to bio­ethanol. By contrast, GTs can start on biodiesel.

Eisert said GE has tested B99.9 in a 2 × 1 LM6000-powered combined cycle and confirmed that load varia­tion, emissions, and operability meets expectations. The biodiesel enabler kit for fuel that meets GE specifica­tions was scheduled for commercial availability before the summer. A fuel-pretreatment skid designed to clean-up lower-grade biodiesel (it costs less) to GE specs at your plant is expected before year-end.

Advancements in compressor coatings

Dr V P (Swami) Swminathan of the San Antonio-based consultancy Tur­boMet International is known in the generation sector of the electric power industry as a highly experi­enced metallurgist. He was at West­ern Turbine to present the progress in the development of erosion-resis­tant nano-coatings for LM-engine, as well as large frame, compressor blades.

While Swminathan’s work with colleague Dr Ronghua Wei of South­west Research Institute, San Anto­nio, on a program funded by the Electric Power Research Institute under the direction of David Gandy, is important, the room had some empty seats. One reason: There were three concurrent sessions in the Tuesday afternoon time slot.

Another is that most powerplant O&M personnel have not had any formal training in the science of metallurgy; they only know what components/materials last in pow­erplant service and the ones that don’t.

Coatings for compressor blades are a hot topic today because it doesn’t take much of a nick from a solid par­ticle in the inlet air stream to initi­ate the failure of a highly stressed standard-issue compressor blade—at least on some machines. Likewise, erosion of blades by liquid droplets is a major concern of owner/operators who want to saturate inlet air with water on hot days to maximize power output (Fig 1). Erosion reduces com­pressor efficiency and can contribute to airfoil failure.

Thus affordable coatings capa­ble of protecting blades and vanes against damage without compromis­ing their mechanical properties are of great interest. The work by Swmi­nathan and Wei is broad enough to have application in aeroderivative and frame GT compressors as well as in both large HP and LP steam turbines. However, only develop­ments of interest to the aeroderiva­tive-engine community are covered here.

Simply put, the objective of the EPRI program is to develop nano-technology coatings using the plas­ma-enhanced magnetron sputtering (PEMS) method to mitigate solid par­ticle erosion (SPE) and liquid droplet erosion (LDE) of compressor airfoils. A key attribute of the PEMS process is that it deposits very dense, hard and tough coatings.

Here’s the overall plan EPRI is following to develop and commercial­ize one or more coatings to improve the reliability and performance of critical GT assets and maximize the lifetimes of critical parts:

1. Select the most promising coat­ings for investigation. These included the nano-composite titanium silicon carbo-nitride (TiSiCN), nano-crys­talline titanium nitride (TiN), and multilayered nano coatings (such as a bond coat of Ti followed by a layer of TiN or a layer of TiSiCN).

2. Apply the selected coatings by the PEMS method on substrate material used for compressor blades and vanes.

3. Conduct screening tests (SPE, LPE, hardness, adhesion, etc) on small samples to identify the most promising coatings.

4. Compare the properties of these samples with similar results from other commercial techniques.

5. Develop coating process specifi­cations for the selected coatings.

6. Conduct qualification testing by mechanical property evaluations and thermal exposure tests to simulate field service conditions.

7. Apply the selected coatings to compressor components and conduct field evaluations.

8. Commercize the technology.

Steps 1 through 6 are mostly com­plete. Results thus far favor a sin­gle layer of TiN or TiSiCN over the multi-layer coatings in cost-benefit terms, and TiSiCN may have the bet­ter pedigree with a good combination of hardness and toughness. TiSiCN is a superior coating with a hardness of 40 to 80 GPa (giga Pascals). By com­parison, the hardness of a diamond is about 100 GPa; tool steels are in the single digits.

Swminathan and Wei also have identified the process variables criti­cal to producing the best TiN and fine-grained TiSiCN nano-compos­ite coatings by the PEMS process. Deposition parameters have been optimized for various coating com­positions and reproducibility of the coatings has been verified.

Extensive mechanical test results indicate that the hard coatings do not have any adverse effect on the tensile and high-cycle-fatigue properties of the compressor-blade alloys. In some cases, the coatings improved high-cycle-fatigue strength.

Adhesion strength and resistance to solid-particle and liquid-droplet erosion of the best-performing coat­ings are very good. Full-size blade coating and engine rainbow tests are to follow.

WTUI members can access Swmi­nathan’s presentation on the group’s website (www.wtui.com); others can access it at www.turbomet.com. For more information, write swami@turbo-met.com.

LMS100 update

The OEM’s product literature infers that the LMS100 is the “all-every­thing” gas turbine. It offers simple-cycle high efficiency (44% for the PA model with single annular combus­tor; 45% for the PB model with dry, low emissions combustion system), competitive first cost, sustained hot-day power, and 10-min starts with no cycling penalty, and rapid ramp rate with no maintenance penalty (50 MW/min)—ideal attributes for a peaker.

Another benefit is that the engine’s output varies little for grid frequency reductions of up to 5%, so the LMS100 will “ride through” periods of high demand and fluctuat­ing load that might challenge other machines.

The LMS100’s high power-to-steam ratio also offers designers another power-island option for large CHP (combined heat and power) systems. To illustrate: This engine has the same thermal out­put as an LM6000 but it produces twice the electricity (a nominal 103 MW for the PA model at industry-standard test conditions, 99 MW for the PB).

For combined-cycle applica­tions, the LMS100’s relatively low exhaust temperature (less than 800F) means Rankine-cycle equip­ment can be made from convention­al materials, minimizing both capi­tal and maintenance costs. Exhaust flow is a nominal 450 lb/sec for the PB model, 20 lb/sec lower than that for the PA.

NOx emissions for both the PA and PB models are 25 ppm. Water injection requirement for the PA to achieve 25 ppm is 60 gpm.

GE’s Marc Horstman reviewed the engine’s design and operational benefits in a half-hour presentation Wednesday morning. He stressed the reliability-based design approach that incorporates successful compo­nents from both the company’s frame and aero engines (Fig 2).

To illustrate: The six-stage low-pressure compressor was derived from the MS6001FA; the so-called “supercore,” which includes the 14-stage HPC, combustor, and HPT, is derived from the CF6-80C2 and CF6-80E1 aircraft engines that power many Boeing 747s and 767s.

At the time of the Western Tur­bine meeting, Horstman said the first LMS100 placed in service at Basin Electric Power Co-op’s Groton Generating Station in South Dakota had accumulated 1771 operating hours and 225 starts. Plus, it had operated in the synchronous-con­denser mode for grid support four dozen times.

Groton has demonstrated the OEM’s claim of 10 minutes from cold metal to full power as well as the machine’s guaranteed output, heat rate, and emissions levels. For a back­grounder on this plant, access www.combinedcyclejournal.com/archives.html, click 4Q/2006, click “Groton” on the issue cover.

A second unit at the Groton site was scheduled for commercial opera­tion in 2Q/2008; Unit 3 is expected in service for the 2009 summer peak. Horstman said that GE now has 29 LMS100s in operation, under con­struction, or on order—all are water-injected PAs, all simple-cycle. Eigh­teen engines are in the US and all but a half dozen are gas-only.

Service intervals at this stage are the following:

  • Every 4000 hours, conduct bore­scope inspection. Planned outage duration is 12 hours including the cooldown time.
  • Every 25,000 hours, hot-gas-path (HGP) inspection. Spare module—combustor, HPT, IPT—is installed and the unit restarted within four days; owner’s engine is sent to the shop for overhaul.
  • Every 50,000 hours, major inspec­tion. Same as HGP, plus power turbine overhaul and inspection of the following major components: booster, intercooler, scroll frames, HPC, aft shaft, and hydrodynamic bearings. Roller and ball bearings are replaced. There is a 60-day turn on all this work which can be reduced to four days if rotating spares are installed while shop work is done.

Meet the depots

Five authorized service providers for GE aero engines (so-called “Depots”) play a major supporting role in the Western Turbine Users’ annual con­ference and exhibition. Their collab­orative participation in the engine breakout sessions, plus the devel­opment of materials to facilitate understanding of O&M issues, allows attendees to return home confident that demanding operational objec­tives are achievable.

The well-illustrated breakout-ses­sion manuals provided allow users to focus on what’s being said rather than on taking notes, thereby maxi­mizing the absorption of knowledge. These manuals also are important for plant-level training, extending the value proposition of WTUI mem­bership.

The depots provide many of the same services, but there are differ­ences in their offerings. For example, not all depots service all engines, not all depots are qualified to Level 4, etc. The thumbnail sketches below are intended to clarify what each company does and how it serves customers. Listing is in alphabetical order by company name.

Air New Zealand

www.airnewzealandgasturbines.co.nz

Voice: +64 9 256 3201

Fax: +64 9 255 8079

E-mail: gasturbines@airnz.co.nz

Engines serviced: LM5000 (gas gen­erators only); LM2500 (exceptions: G4, LM2500+, and DLE models).

Air New Zealand Gas Turbines, a wholly owned entity of Auckland-based Air New Zealand Ltd, is locat­ed adjacent to that city’s interna­tional airport. The company is a global Level 4 service provider for the engines noted above.

It offers Level 1, 2, and 3 ser­vices onsite. ANZGT’s value proposi­tion includes assisting in decision-making to maximize the value of your assets, resolving onsite issues quickly, one-stop source for parts, modules, and complete engines, and leasing arrangements.

Perhaps the company’s aero ser­vices are best summarized this way: field service, complete repair and overhaul, module exchange, engine test, total logistics.

Note that when depot-level sup­port is required, field-service per­sonnel are available to remove the engine, transport it to the shop, and reinstall it after repairs and testing are complete.

Specific capabilities include the following:

  • Nondestructive examination. Flu­orescent-particle, magnetic-par­ticle, ultrasonic, thermographic, and borescope inspections.
  • Materials testing—including sam­ple preparation. Test capabilities under temperature-controlled con­ditions include tensile, bending, sheer, peel, hardness, cyclic.
  • Component coating. Three-doz­en different coatings/thicknesses are offered. Application processes include plasma spray, thermal arc (HVOF), and metalizing tech­niques.
  • Mobile electroplating. Selective brush plating of silver, copper, nickel, and cadmium.
  • Balancing: Dynamic (two plane) and static (single plane).
  • Coordinate measurement. Con­firmation of dimensions in a temperature- and humidity-con­trolled atmosphere using a Ren­shaw motorized measurement system.
  • Specialized machining—including internal and external grinding, CNC turning and milling (hori­zontal and vertical).
  • Specialized welding—including TIG to AWS.D17.1:2001; Dabber TIG, electron beam, spot welding; magnesium and aluminum alloys, nickel/cobalt alloys, titanium.
  • Heat treatment. Facilities include low- and high-temperature fur­naces, plus an Abar vacuum fur­nace calibrated for an argon atmo­sphere.
  • Fuel-system component testing rigs are available for fuel-flow and pressure testing.
  • Maintenance and reliability plan­ning. Expertise in developing and recommending maintenance pro­grams based on reliability and cost; assist in planning procedures and processes, work flow, and cost monitoring.
  • Calibration. Aviation IANZ and ISO 17025 standards approved for the following categories: force, thermal, pressure, electri­cal, dimensional, flow. Total-care management service available.

Avio

www.aviogroup.com

Voice: +1 703 547 8468

Fax: +1 703 547 8596

E-mail: cdewey@aviousa.com

Engines serviced: LM2500, LM6000 (field-service support only)

Avio specializes in the overhaul and repair of LM2500s and also manufactures several components for the OEM (inlet and accessory gearboxes, front frame assembly, turbine rear frame, bellmouth, plus design and manufacture of the tur­bine control system). The company also has deep experience in LM2500 package design and assembly and in onsite maintenance of this engine. Avio’s depot is in Brindisi (southern Italy) where dedicated teams are responsible for all activities from disassembly to final assembly (Figs 3, 4).

The company recently has installed new equipment to expand its special repair capabilities. It is especially proud of its test cells and work areas for component cleaning, surface treat­ments, and nondestructive examina­tion. Some of the specialized processes Avio offers are these:

  • Nickel graphite seal surface replacement.
  • Silver seal surface replacement.
  • Silver plating restoration of all required parts.
  • Coating replacement (nickel alu­minide) using the plasma spray process.
  • Tip grinding of compressor blades to guarantee minimize clearances.
  • Restoration of rear flange by weld buildup and Triballoy 800 applica­tion.
  • Crack repair by TIG welding.

Specific service capabilities relat­ed to the LM2500 include the follow­ing:

  • Module and engine repair at the Brindisi depot.
  • Onsite preventive and corrective maintenance.
  • Warehouse/spares management.
  • Training.
  • Support equipment.
  • Logistics support analysis.

IHI Corp

www.ihi.co.jp/powersystems/english/index.html

Voice: +81 3 6204 7724

Fax: +81 3 6204 8776

E-mail: plobello@poweronex.com, minoru_hanakata@ihi.co.jp

Engines serviced: LM2500, LM6000

IHI Power Systems Div of IHI Corp (formerly known as Ishikawa­jima-Harima Heavy Industries Co Ltd, which was established in 1853) offers a life-cycle support package for gas-turbine customers. It has three components: Planning (feasi­bility studies), packaging, and main­tenance.

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 the only Level 4 depot in Asia qualified to service LM2500 and LM6000 engines.

It is now increasing its mainte­nance services for the Americas, especially for LM6000s, and has assigned Poweronex responsibility for coordinating this effort. Peter LoBello is directing this work from Boca Raton, Fla.

IHI’s shop facilities are located in Mizuho and Kure. At the Miz­uho Works, the company can repair almost all component parts for the LM6000, ensuring smooth imple­mentation of high-quality overhauls (Fig 5). Kure Works is equipped with a GT test cell (Fig 6) for confirming proper balance, etc, after overhauls are complete.

MTU Maintenance

www.mtu.de

Voice: +49 3378 824 313

Fax: +49 3378 824 72313

E-mail: ulf.kliemank@mtu.de

Engines serviced: LM2500, LM5000, LM6000—all types of each engine

MTU Maintenance Berlin-Bran­denburg GmbH, based in Ludwigs­

3. Avio mechanics reassemble an LM2500 (left)

4. Avio machinist works on an LM2500 compressor rotor assembly felde, south of Berlin, is an MTU Aero Engines affiliate with more than 25 years of experience in serving the aero community. It has serviced more than 600 engines in that time and currently has 100 gas turbines under long-term service agreements (LTSAs). The Ludwigsfelde works is the center of excellence for all MRO services associ­ated with the LM engines.

4. GT operating hours trend upward

Strategic Power Systems Inc’s founder, Sal DellaVilla, is a “regular” on the Western Turbine Users program Wednesday morning—the last day of the meeting. Recall that SPS, which specializes in the collection and analysis of powerplant O&M data, has worked closely with WTUI since the organization’s incorporation.

The WTUI officers and directors realized early on that having performance-related information for aeroderivative engines across the industry would benefit all participating users in their efforts to improve operations. They wanted to track the availability and reliability of their operating assets as a fleet and endorsed SPS’s ORAP® system for that purpose.

ORAP (for Operational Reliability Analysis Program) is an automated system for monitoring and reporting the RAM-D (reliability, availability, maintainability, durability) of power and process plants equipped with gas and/or steam turbines. Data currently are tracked on well over 2000 units worldwide.

DellaVilla had half an hour to explain the SPS value proposition to newcomers and to update the group on O&M trends. Bullet points on value included the following:

  • Aligning multiple plants into a common culture—one with identical RAM metrics, calculations, and report formats.
  • Delivering unbiased, third-party performance data for benchmarking your plants against each other and the fleet as a whole.
  • Developing a scalable process that fosters a best-in-class culture across a growing portfolio.
  • Establishing a process for identifying critical spares.
  • Ensuring that parts-life and inspection plans fol­low OEM recommendations cost-effectively (access www.combinedcyclejournal.com/archives.html, click 3Q/2005, click “Proactive management of GT parts” on the issue cover).

Perhaps of greatest interest to the entire audience was the statistical information that DellaVilla presented. Using LM2500 data as an example, he showed the sig­nificant increase in number of operating hours for aeros in 2007 compared to aggregate data for the five years 2003-2007.

Engines in standby/peaking service started two times more frequently in 2007 than the five-year data would have predicted; service hours per start for these units were down dramatically. The table at right also shows that units in cycling duty didn’t start as often as in past years, but they ran almost twice as long per start in 2007. Trend-busting continued in the base-load/continuous category as well with starts off slightly and service hours per start up dra­matically.

One probably would expect reliabil­ity to drop with an increasing number of starts and that was the case for the standby/peaking units. Theoretically, the converse also should be true: Reliability should increase with fewer starts. And it did for base-load/con­tinuous machines. However, the num­ber of failures jumped significantly with fewer starts for units in cycling duty.

Then DellaVilla compared all aeros, E frames, and F frames in the SPS database against each other for 2007 and the five-year 2003-2007 period. Here are those results:

  • Simple-cycle units, service factor (hours operated as a percentage of total hours in a year). F frames had the highest service factor (2007/five years) at 53.1%/52.7%, aeros were next at 46.3%/45.3%, and E frames last at 36.9%/35.0%. Thus each group oper­ated more in 2007 than it had in the last five years (average, annual basis).
  • Simple-cycle units, fired hours per start. Once again the F frames led the group with 43.65 (2007 hours)/46.2 (hours per start averaged over the last five years), E frames were next at 40.78/42.1 hours, and aeros last at 31.6/35.4 hours. Thus fired hours per start were down across the board.

Notable is that 80% of the repair work on LM engines is completed internally, resulting in cost and turn­around-time advantages to users without sacrificing quality—the thinking here is that repair beats replacement (Fig 7). The company’s repair network includes shops in the German cities of Hannover and Munich and in Malaysia. At MTU’s test-cell center, LM2500 and LM6000 engines are tested under real-load conditions (Fig 8) without restric­tions with respect to grid synchroni­zation. LM5000s are tested on a jet-engine test bed.

MTU scope of services ranges from onsite repairs and module exchanges worldwide to compre­hensive depot repair and overhaul activities. Onsite services include the following:

  • Resources are available 24/365.
  • Hotline for troubleshooting and engineering support.
  • Local field-service representa­tives in the Americas and Asia/Pacific.
  • Periodic inspections as well as Level 1 and 2 maintenance.
  • Rotable units, tooling manage­ment, spare-parts supply/manage­ment.
  • Remote monitoring and trend analysis.
  • Vibration surveys, trim balancing, laser alignment, DLE mapping.

Principal shop capabilities:

  • GE-approved Level 4 depot.
  • Hot-section replacements/refur­bishment.
  • Overhaul/repair of gas generators and power turbines.
  • Customized scopes of work.
  • Engineering support for each engine type.

Among MTU’s other services for owner/operators are training (engine familiarization, borescope, and con­trols courses); LTSAs with availabil­ity guarantee; performance guaran­tees and restoration; and engines and modules for lease.

TransCanada Turbines

www.tcturbines.com

Voice: +1 403 219 6600

Fax: +1 403 219 6601

E-mail: info@tcturbines.com

Engines serviced: LM2500, LM2500+, LM6000—including all variants of each engine, including DLE

TransCanada Turbines (TCT), a joint-venture company owned equal­ly by TransCanada Corp and Wood Group, provides a complete range of engine overhaul and refurbish­ment services for the engines listed above. Plus, it offers a wide variety of customized products and servic­es—including field service, rotable exchanges, scheduled maintenance and inspections, and repair services.

TCT operates two licensed over­haul facilities in Calgary, Alta, Canada—one dedicated to LM engines. Both facilities are quali­fied to ISO 9000:2001 and are with­in minutes of Calgary International Airport. Services include parts sup­ply, onsite maintenance, Service Bulletin and Service Letter imple­mentation, troubleshooting, engine testing and calibration, and repair and overhaul.

The company owns and operates a Category 1 test cell in Calgary, which it uses for testing the LM2500 and some non-GE engines. LM6000s are tested at a local power station against a live grid. It replicates the customer’s actual operating conditions.

In addition to the two depots in Calgary, TCT has four strategically located field-service offices/shops: Glasgow, Scotland; Bakersfield, Calif; Syracuse, NY; Houston, TX. Each is qualified to ISO 9000 and equipped with Level 2 tooling, spare parts, and certified technicians. A field-service organization extends the company’s reach to virtually every GT-based generating facility worldwide, on shore and off.

Finally, TCT’s Package Power Parts business is based in the Hous­ton field-service office. Its charter includes parts sales, service, techni­cal guidance, and balance-of-plant services for owners and operators of LM2500 and LM6000 engines and packages. ccj