GER-3928A

UPRATE OPTIONS FOR THEMS900A HEAVY-DUTY GAS TURBINE

Jennifer E. GillGE Power SystemsSchenectady, NY

ABSTRACTThe GE MS9001 heavy-duty gas turbine has gone

through a series of uprates since its originalintroduction to the market in 1975. These uprates aremade possible by technology advances in the designof new machines based on information accumulatedthrough tens of thousands of fired hours, newmaterials and GE’s continuing research.

This paper will discuss evolutionary designadvances in critical components for the GE MS9001series of turbines. It will also discuss how the latest“E” technology advances can be applied to enhancethe performance, extend the life and provideeconomic benefits by increased reliability andmaintainability of all earlier MS9001B andMS9001E turbines.

The following “E” technology uprate packageswill be described:

• MS9001 “B to E” turbine uprates• MS9001E firing temperature increase to

2020°F/1104°C• MS9001E firing temperature increase to

2055°F/1124°CThe paper also describes options for reducing

emissions, tradeoffs and expected reductions, and,GE programs for uprating, either as a single projector phased in over time.

INTRODUCTIONThe past decade has seen unprecedented pressures

on both utilities and independent power producers tohold the line on new investments, to become moreeffective in operations and maintenance, and to bemore efficient in producing power. Modernizing anduprating their installed fleet of turbines is emergingas an economically attractive solution. An uprateoffers these benefits:

• Performance improvements in output and heatrate

• Extension of inspection intervals whileshortening their duration

• Availability and reliability improvements• Emission reductions

GT25018

Figure 1. MS9001E Simple-Cycle single-shaft heavy-duty gas turbine

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• Life extensionUprates are made possible as a result of GE’s

underlying design philosophy which is to maintaininterchangeability of components for a given framesize such that components can be installed in earliervintage units with little or no modifications. Installingthe latest technology hardware and taking advantangeof the highest firing temperatures allowsowners/operators to remain competitive in themarketplace. Virtually every key component in theMS9001 series has gone through significant designimprovements since the first MS9001B was shippedin 1975. Buckets, nozzles, shrouds and combustioncomponents have undergone multiple evolutionsbased on new designs, manufacturing techniques,materials and field experience. Figure 1 illustrates thebasic MS9001E configuration.

Uprates make very good investments, with mostexhibiting prompt payback. Each turbine applicationmust be evaluated on its own merits, but paybacksunder two years have been registered. Uprates can bephased in according to the outage schedule, orinstalled in a single outage, with appropriate advancescheduling.

Gas Turbine reference codes (e.g., FT5X for anMS9001 B to E advanced technology uprate havebeen added to the text and to many of the figures andtables for easier correlation to other publishedinformation on specific uprate packages orcomponents.

MS9001 HISTORYThe first MS9001, shipped in 1975 as a model

MS9001B for the 50 Hz market, incorporated designexperience from the successful MS7001B. Operatingwith a design firing temperature of 1840 F/1004 C

(base load), the same firing temperature as theMS7001B, the MS9001B design represented anincrease of 42% in output over the MS7001B. Thisintroductory design incorporated the air-cooled stage1 buckets and nozzles and stage 2 bucket materialimprovements based on the MS7001B designexperience gained prior to 1975. As seen in Figure 2,the output of the MS9001 has increased by 45%based on technology improvements through 1994, notincluding the EC or F/FA product lines.

Introduced in 1978, the MS9001E, incorporatedthe experience gained from MS7001E production andoperation as well as the design improvements thathad evolved since the MS9001B was first introduced.The introductory firing temperature was1955°F/1068°C.

As apparent from performance increases, theMS9001E has seen many design improvements sinceit was introduced as an MS9001B, with one obviouschange being the increased firing temperature.Advances in materials, coating and coolingtechnology have supported a series of firingtemperature increases. The current firingtemperature of the latest MS9001E is2055°F/1124°C. All earlier vintage MS9001E gasturbines can be uprated to the 2055°F/1124°C firingtemperature.

CURRENT MS9001ECOMPONENT TECHNOLOGY

Product technology derived from ongoing newproduct development, field service reports and newmaterials and techniques has resulted inimprovements to combustion liners, transition pieces,high flow inlet guide vanes and all stages of buckets,nozzles and shrouds.

The component improvements can be appliedindividually or as a complete uprate package,depending on schedule, budget and machinecondition. Design improvements and rationale will bedescribed, as well as their effect on performance andmaintenance.

COMBUSTION SYSTEMCOMPONENTS

Efforts to advance the combustion system aredriven by the need for higher firing temperatures andfor compliance with regulatory requirements toreduce exhaust emissions. Relatively simple parts in

PG9111B

PG9141E

PG9157E

PG9151E

PG9161E

PG9171E

PG9231EC

PG9301F

PG9311FA

GT18469 “I”

1975-81

1978-81

1981-83

1983-87

1988-91

1991

1996

1993-94

1994

ModelShip

Dates

85,200

105,600

109,300

112,040

116,930

123,450

165,700

209,740

223,760

ISOPerformance*

kW

*Base Load Distillate Fuel, Includes 0/0 Inches H2O Inlet/Exhaust Pressure Drops

1840/1004

1955/1068

1985/1085

2000/1093

2020/1104

2055/1124

2200/1204

2300/1260

2350/1288

FiringTemp. °F/°C

2.736/1.241

3.155/1.431

3.183/1.444

3.214/1.458

3.222/1.461

3.231/1.466

4.044/1.834

4.804/2.179

4.819/2.186

Air Flow(106 lbs/hr106 kg/hr)

10,990/11,592

10,700/11,286

10,700/11,286

10,570/11,149

10,290/10,854

10,080/10,632

9,870/10,411

10,080/10,632

9,630/10,158

Heat Rate(Btu/kW/hrkJ/kWh)

945/507

953/512

968/520

977/525

980/527

998/537

1,037/558

1,082/583

1,097/592

ExhaustTemp. °F/°C

Figure 2. MS9001 Performance History

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early gas turbines are now complex hardware pieceswith sophisticated materials and processingrequirements. Combustion system upgrades can besupplied as a package or as individual options.Depending on the option chosen and other machineconditions, upgraded combustion system componentsproduce substantial improvements in component lifeand/or for extensions in recommended combustioninspection intervals.

Combustion Liners (FR1G/FR1H)The MS9001B/E series consists of 14 combustion

chambers. The original combustion liner on the

MS9001B was the louvered liner, which was cooledthrough louvered punches in the liner body. The bodycould experience cracking due to stresses inherentlyintroduced during the manufacturing process. Thelouvered liner was replaced with a slot-cooled linerwith the introduction of the first MS9001E. Bothliners are shown in Figure 3. The slot-cooled linerprovides a more uniform distribution of cooling airflow for better overall cooling. Air enters the coolingholes, impinges on the brazed ring and dischargesfrom the internal slot as a continuous cooling film.

The liner material is Hastelloy-X, a nickel-basealloy, which has not changed since the introduction ofthe MS9001B in 1975. Today, however, a thermalbarrier coating (TBC) is applied to the liners. TheTBC consists of two materials applied to the hot sideof a component (Figure 4): a bond coat applied to thesurface of the part and an insulating oxide appliedover the bond coat. This TBC provides a 0.015-inchinsulating layer that reduces the underlying basematerial temperature by approximately 100°F/38°C.The addition of TBC also mitigates the effects ofuneven temperature distribution across the metal.

With the MS9001E firing temperature increase to2055°F/1124°C, the thickness of the liner was alsoincreased by approximately 10 mils to accommodatethe higher temperatures.

Transition Piece (FR1D)

GT24927.ppt

Slot-CooledLiner

LouveredLiner

Figure 3. Improved slot-cooled liner vs. originallouvered liner

Liner

GT11701D

Coating Microstructure

Top Coat

Bond Coat

Figure 4. Thermal barrier coatings 1

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The original 9B combustion system was a parallelsystem, with the combustion liner parallel to thecenterline of the rotor. When the first 9E was

developed, the combustion system was redesigned.The redesigned system was a “canted” systemconsisting of a shorter transition piece and the slot-cooled liner. Shortening the length of the “transition”section of the transition piece increased its stiffness.The canted design reduced the angle through whichthe combustion gases had to flow, thus providing amore direct flow path. The canted design made itpossible to shorten the transition section of thetransition piece, and therefore shorten the overalllength of the transition piece.

When the firing temperature was increased to2055°F/1124°C, the “canted” arrangement wasupgraded to the “canned” arrangement. The “canned”arrangement consists of a longer transition piece witha thicker slot-cooled liner, as previously mentioned.The longer transition piece essentially pushes theliner out of the wrapper. Outer combustion casings asseen in Figure 5. The transition piece was lengthenedby adding a 15-inch long cylinder to the forward end.While the transition piece length was increased, thecurved section remained the same, thereby retainingits stiffness. The transition piece was lengthened torelocate the transition piece-liner interface, in order tominimize wear induced by the compressor dischargeflow. Figure 5 illustrates the differences between thecurrent 9E production “canned” arrangement, the 9E“canted arrangement and the 9B parallel combustor.

Early 9B turbines utilized a thin-walled transitionpiece constructed of Hastelloy-X material. Theoriginal 9E transition piece was a thick- walledHastelloy-X. In the mid 1980s, the transition piece

MS9001B Parallel Arrangement

MS9001E Canted Arrangement

GT25006.pptMS9001E Canned Arrangement

Figure 5. MS9001 combustion system comparison

Old DesignAft Bracket

GT21369A.ppt

RedesignedAft Bracket

TransitionPiece

TransitionPiece

AftEnd

Figure 6. Comparison of transition piece aft bracket

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material was changed to Nimonic 263 which is anickel-base alloy with better strength characteristicsthan Hastelloy-X. Nimonic 263 demonstratedsuperior creep life and could increase the inspectioninterval to 12,000 hours. The Nimonic 263 transitionpieces are coated with thermal barrier material,thereby reducing metal temperatures and increasingcomponent life.

The Nimonic 263 transition piece has a positivecurvature body and aft bracket that reduces crackingat the bracket weld area by allowing the transitionpiece to pivot about the pin during thermal cycles. Acomparison of the original and redesigned aft bracketdesign is shown in Figure 6.

GE has recently designed a new Nimonic transitionpiece for the MS9001B to provide a substantialincrease in creep strength over the current design.The uprate potential of the current MS9001Bmachines is limited by the inability of the currenttransition piece to withstand higher firingtemperatures. This improved transition piece enablesthese units to be uprated beyond their current ratedfiring temperature. Additionally, this improvedtransition piece is required for these units to realizethe full benefits of the Extendor™ CombustionSystem.

Extendor™ Combustion System(FR1V/FR1W)

All GE heavy-duty gas turbines require periodiccombustion inspections due to TBC coating erosion,

wear and material creep. GE has developed a product– Extendor™ – to increase combustion inspectionintervals. The Extendor™ combustion system, shownin Figure 7, decreases combustion component wearand increases combustion inspection intervals byreducing the relative movement and associated wearof parts in the combustion system. Application of theExtendor™ wear system extends transition pieceinspection intervals up to 24,000 hours. Figure 8details the improved combustion wear inspectionintervals.

Customer savings occur with the elimination oflabor costs associated with combustion inspectionsand reduction of component repair costs. Extendor™can be applied as a component modification duringroutine maintenance or as a complete retrofit.Extendor™ is currently available for MS9001 seriesgas turbines with slot-cooled liners and Nimonictransition pieces.

Dry Low NOx Combustion System(FG2B)

Customers without diluent supplies for injectionpurposes can achieve NOx emission requirementsthrough the use of Dry Low NOx combustors. TheDLN combustion system for the MS9001E is shownin Figure 9. The DLN combustion system reducesNOx emissions without steam or water injection ongas fuel units. This is done by fuel staging, with leanfuel to air ratios dependent upon premixing fuel with

Fuel Nozzle toFloating Collar

Crossfire Tube,Retainer & Stop

T/P H Block toBullhorn

TransitionPlace SealFrame

Liner Hula Sealto TransitionForward Sleeve

GT20550

Figure 7. ExtendorTM combustion system

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hot compressor discharge air to yield lowertemperature rises across the combustor.

The DLN combustor (Figure 10) has sixindividual fuel nozzles in the primary combustionzone, and a single fuel nozzle in the secondarycombustion zone. The DLN combustion systemoffers lower NOx emission levels on gas fuel-firedunits without parts life reduction associated withwaer or steam injection NOx reduction systems.Emission levels of 15 ppmvd at 15% O2 or less canbe reached by using the DLN combustion system.

TURBINE COMPONENTSThere have been significant design and material

improvements made to the turbine components sincethe first MS9001B was manufactured. The improved

component designs can withstand higher firingtemperatures due to advanced materials and coatings,as well as the addition of air cooling for some of thecomponents. This section will describe the evolutionof these technologies. The latest technologycomponents now used in current productionMS9001E can be retrofitted to earlier models.

BUCKETS

Stage 1 Bucket (FS2H)Four major changes have been made since the

original MS9001B stage 1 bucket was introduced.

Design.The original design’s sharp leading edge has been

blunted to allow more cooling air to flow to theleading edge, which reduces thermal gradients and,therefore, cracks. The Blunt Leading Edge (BLE)design, shown in Figure 11, was used as the firstMS9001E stage 1 bucket.

Materials.The original MS9001B stage 1 bucket was IN-

738, a precipitation-hardened, nickel-base superalloy. In 1987, the material was changed to anEquiaxed (E/A) GTD-111, also a precipitation-hardened, nickel-base super alloy, a greater low cyclefatigue strength than IN-738. GTD-111 also providesthe industry standard in corrosion resistance.

Coatings.

Lean andPremixing

Primary Zone

SecondaryFuel Nozzle

(1)

PrimaryFuel Nozzles

(6)

GT15050B

Dilution ZoneSecondary Zone

Centerbody

VenturiEnd Cover

Outer Casing Flow Sleeve

Figure 10. Dry Low NOx combustor

GT25007A

Flow Sleeve

Case,Combustion

Outer

Wrapper

Primary Fuel Nozzle &Combustion Cover

Assembly

Secondary FuelNozzle Assembly

CompressorDischarge Casing

TransitionPiece

Figure 9. MS9001 dry low NOx combustion system

Combustion Liners

Transition Pieces - Thin Wall

- Thick Wall

- Nimonic

Hot Gas Path

Major

Significant Savings in Maintenance CostGT25218

3,000

3,000

8,000

12,000

24,000

48,000

8,000

----

8,000

12,000

24,000

48,000

24,000

----

----

24,000

24,000

48,000

9B ExtendorTM9EHours

Figure 8. Typical MS9001B vs. MS9001Emaintenance

Original Designand ThermalGradients

GT21321A.ppt

Blunt Nose BucketWith ImprovedThermal Gradients

Figure 11. Sharp and blunt leading edge bucketdesign comparison

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The first 9E bucket coating, platinum aluminide,was applied to stage 1 buckets in order to preventoxidation and corrosion. In 1991, with the addition ofturbulated cooling holes, the bucket coating waschanged to GT-29 INPLUS. This coating is avacuum plasma spray with an aluminide coating onthe bucket exterior and the internal cooling holepassages. In 1997 the coating was changed again toGT-33 INCOAT. GT-33 is a vacuum plasma spraycoating like GT-29, but offers an increased resistanceto through cracking. “INCOAT” refers to analuminide coating on the cooling holes passages.GT-33 INCOAT is GE’s new standard coating forstage 1 buckets, however GT-29 INPLUS is stillavailable and is recommended when burningcorrosive fuels.

Stage 2 Bucket (FS2F)The stage 2 bucket has changed significantly since

the original bucket was introduced.

Cooling.The original MS9001B stage 2 bucket did not

have internal air cooling. The MS9001E designcontains air-cooled stage 2 buckets, as shown inFigure 12. The addition of air cooling allows forhigher firing temperatures. In order to replace nonair-cooled stage 2 buckets with the new air-cooledbuckets, the 1/2 wheel spacer must be replaced withthe new design that allows air to flow to the stage 2bucket.

This bucket can be supplied without internalcooling air passages as a direct part replacement forthe MS9001B. With this option, the 1/2 wheel spacerwould not have to be replaced. While lower in cost,the non-air-cooled version of this bucket would not beable to withstand an increase in firing temperatureabove 1905°F /1040°C.

Tip Shroud.The shroud leading edge was scalloped (Figure

13), the shroud tip was thickened between the sealteeth, and the underside of the shroud was tapered.Scalloping the leading edge decreased the stress at thetop of the fillet. The final design (Figure 14) resultedin a 25% reduction in stress levels and an 80%increase in creep life over the original design.

GT24908.ppt

Core Plug

EnlargedView A-A

CoolingHole

A A

Figure 12. MS9001E stage 2 air-cooled bucket

GT21361A

Figure 13. Scalloping of bucket shroud

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The most recent design change added cutter teethto the bucket tip rails. These cutter teeth weredesigned for use with the new Honeycomb stage 2shrouds. The “twisted rail” design cutter teeth,standard on all new stage 2 buckets, essentiallyrotates the tip rails by 0.5 degrees, causing the tiprails of each bucket to be offset relative to thepreceding and subsequent buckets. This offset createsthe cutter tooth. required with honeycomb shrouds.During transients when the bucket tip clearance is thesmallest, the cutter teeth cut a path through thehoneycomb material in the shroud, thus minimizingthe steady-state clearance. Stage 2 buckets withcutter teeth are required for use with honeycombshrouds, but can also be used with the traditionaldesign shrouds. Cutter teeth can also be applied tobuckets in good condition with fewer than 48,000hours of operation in a qualified service shop.

Materials.The original bucket was made of U-700, a

precipitation-hardened, nickel-base alloy. Since then,there have been two changes to the bucket material.For early MS9001E production, the material waschanged to IN-738, a precipitation-hardened, nickel-base super alloy which provided an increase inelevated temperature strength and hot corrosionresistance. In 1992, the material was changed toGTD-111, also a precipitation-hardened, nickel-basesuper alloy, to improve rupture strength. In additionto a higher rupture strength, GTD-111 has higherlow-cycle fatigue strength.

Coating.With the change in material to GTD-111, GT-29

INPLUS coating was added. INPLUS coating refersto PLASMAGUARD GT-29 with an overaluminidealuminide coating on the internal cooling passages.Like the stage 1 bucket, the standard coating waschanged to GT-33 INCOAT in early 1997. GT-33INCOAT consists of GT-33, a vacuum plasma spraycoating, on the exterior of the bucket and analuminide coating on the interior of the cooling holepassages. GT-33 INCOAT provides superiorthrough crack resistance relative to GT-29 INPLUS.GT-29 INPLUS is still available and is recommendedfor use in corrosive fuel applications.

Stage 3 Bucket (FS2K)

The MS9001B stage 3 bucket has experiencedchanges in design, manufacturing process andmaterial.

Design.With the introduction of the 9E, the airfoil was

rotated to take advantage of the additional airflow.The airfoil was further rotated in 1991 as part of theuprate program. These rotations are the basis of theperformance improvements shown in Figures 35 and36.

The trailing edge was thickened, and the chordlength increased. Like the stage 2 buckets previouslydescribed, the shroud leading edge was scalloped, theshroud tip was thickened between the seal teeth, andthe underside of the shroud was tapered. These designchanges resulted in an increase in creep life of thebucket.

Like the stage 2 buckets, the most recent changewas to add cutter teeth to the bucket tip rails. Thesecutter teeth are required for use with stage 3honeycomb shrouds, as previously described. Currentproduction stage 3 buckets include cutter teeth.Cutter teeth can be added to the stage 3 buckets ingood condition with fewer than 48,000 hours ofoperation in a qualified service shop.

In order to use the 9E bucket on a 9B machine, thestage 3 shrouds must be replaced or modified. Figure15 illustrates the machining points on the shroudwhich is required for the modification. Additionally,due to interference with the angel wing,owners/operators may elect to machine the exhaustframe to facilitate rotor removal, however it is notrequired.

GT21362A

Figure 14. Final configuration of bucket shroud

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Process Change.The original MS9001B stage 3 bucket was cold

straightened after being cast, inducing strain in thematerial. The combination of the induced and creepstrains resulted in potential creep-rupture cracks,further propagated by high-cycle fatigue. GEdeveloped a new manufacturing process for theMS9001E bucket which eliminates the need for thecold straightening step, thus eliminating the process-induced strain in the material.

Materials.Bucket material has recently been improved. The

stage 3 bucket was originally made of U-500, aprecipitation-hardened, nickel-base alloy. To improveelevated temperature strength and hot corrosionresistance, the bucket material was changed in 1992to IN-738, a precipitation-hardened, nickel-basedsuper alloy.

NOZZLES

Stage 1 Nozzle (FS2J)

The MS9001 stage 1 nozzle has evolved through

four generations, each improving on the precedingone, starting with the MS9001B 4-vane nozzle. Thesecond generation, designed for the MS9001E, wasused primarily for clean fuel applications. The thirdgeneration – the Universal Fuel Nozzle – wassignificant because it is applicable for gas, distillateand ash-bearing fuels. The fourth generation, knownas the Chordal Hinge Nozzle, incorporated GEAircraft Engine technology as well as improved

Modify Existing Third Stage Shroudsas Shown Above.

1

1

GT24909.ppt

Figure 15. Machining required on stage 3 shroud

GT25005

9E Clean FuelStage 1 Nozzle

9E Universal FuelStage 1 Nozzle

9B Stage 1 Nozzle 9E Chordal HingeStage 1 Nozzle

Figure 16. Comparison of 9B and 9E stage 1 nozzles

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cooling and sealing technology. This section willdiscuss the design improvements brought about ineach generation. A comparison of the cross-sectionsof each generation is shown in Figure 16.

Several design modifications were made to theoriginal MS9001B stage 1 nozzle to develop theMS9001E clean fuel stage 1 nozzle. One of the mostdramatic changes was made in response to the vanefillet cracking problem (Figure 17) caused by highthermal stress induced by the high thermal gradientacross the sidewall/vane interface. By decreasing thenumber of vanes per segment, structural redundancyand the thermal stresses were reduced, thusminimizing the vane fillet cracking. The original 9Bstage 1 nozzle had four vanes per segment andrequired 12 segments. The clean fuel nozzle has only

two vanes per segment with a total of 18 segments.As illustrated in Figure 16, the interface between thesupport ring and nozzle was moved downstream.

At the same time that the number of vanes persegment was reduced, the shape of the airfoil wasoptimized and the vanes were rotated to reduce thethroat area. The new airfoil shape and reduction inthroat area increased the pressure ratio. Installing thisdesign into an MS9001B can increase the pressureratio by as much as 6%.

The suction side wall thickness of the nozzleairfoil at the pitch section was increased by 13%,which effectively reduced the aerodynamic-inducedmechanical stress and increased the creep life of thepart. The stress level was further reduced by theaddition of an internal center rib. The center rib isshown in Figure 18.

The Universal Fuel Nozzle was developed fromthe clean fuel nozzle in response to the need to burnresidual fuels, as well as clean fuels. The airfoilshape was rounded making it more blunt and theentire cooling system was redesigned. The pressureside cooling holes were replaced with slots and placedcloser together to provide more uniformcooling(Figure 19). Trailing edge cooling was alsoadded as seen in Figure 19. This improved coolingdesign decreased surface metal temperature by asmuch as 5% thus minimizing cracking, airfoilballooning, and trailing edge bowing.

The nozzle support ring interface was moved

FilletCracks

Outer Sidewall

GT21363A

Flow

Inner Sidewall

Figure 17. Cracked center stage nozzle 1

Center Rib

Core Plugs

GT24913

Figure 18. Stage 1 nozzle airfoil pressure side filmcooling modification

Modified SlotPattern

Old HolePattern

Trailing EdgeCooling Holes

Core Plugs

Center Rib

Suction SideFilm Cooling

Holes

Pressure SideFilm Cooling

Holes

• Pressure Side Film Holes Replaced With Slots to Provide Better Coverage− Closer Spacing− Better Exit Condition

• Modification Introduced With OSW Cooling Redesign

GT24924

Figure 19. Stage 1 nozzle airfoil pressure side film cooling

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further downstream in line axially with the nozzle-retaining ring interface. This change wasimplemented to minimize torsional forces exerted onthe sidewall near the nozzle-retaining ring interface.

In 1992, a tangential support lug consisting of anintegrally cast side support lug with a milled radialslot was introduced to the stage 1 nozzle inner sidewall. A support pin and bushing were also added tosecure the nozzle segment. A lockplate and a singleretainer bolt were used to keep the support pin inplace. This arrangement provided additionaltangential support for the nozzle.

The forth and current generation of stage 1 nozzleis the chordal hinge nozzle introduced in 1994. Thisnozzle is the result of two major design changesmaintaining the philosophy of burning both clean andheavy fuels. The first design change was made toreduce the leakage between nozzle segments andbetween the nozzle and support ring. The chordalhingewhich incorporates the latest in GE AircraftEngine sealing technology, was added. The chordalhinge refers to a straight line seal on the aft face ofthe inner side wall rail which ensures that the seal ismaintained even if the nozzle rocks slightly. Thechordal hinge and the new sidewall seal design areillustrated in Figure 20. The chordal hinge reducesthe leakage between the nozzle and the support ring.

The leakage between the nozzle segments wasdecreased by improving the sidewall, or spline seals.

The second major change was to improve thesidewall cooling. As the firing temperature increasedover the development of the MS9001E, the nozzlewas exposed to higher temperatures, causingoxidation and erosion to occur on the sidewalls. Toreduce the oxidation and surface erosion, the coolingeffectiveness was increased. The overall coolingeffectiveness was improved by relocating some of asseen in Figure 21.

When the chordal hinge nozzle was introduced, theoriginal tangential pin hardware was replaced with asingle piece bushing/tangential pin to secure thenozzle and a flat lockplate with two retainer boltswas used to keep the bushing/tangential pin in place(Figure 22). More recently the tangential pinhardware has been eliminated–field inspections haveindicated that the hardware is not required. Inaddition to eliminating the hardware, the forwardflange on the support ring has been eliminated(Figure 23). These design modifications make theuniversal nozzle and chordal hinge nozzle completelyinterchangeable with no support ring modificationsrequired.

As seen in (Figure 16), the 9B stage 1 nozzle andthe 9E clean fuel nozzle support ring interface is

Final DesignPresent Design

HookMachining

Relief

ImprovedSeal

Chordal HingeSeal

GT24932Lug Maching Relief

Figure 20. Stage 1 nozzle improved sidewall sealing with chordal hinge

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located further upstream than either the Universal orChordal Hinge stage 1 nozzle. Therefore, to installthe chordal hinge stage 1 nozzle in a unit thatcurrently has the 9B stage 1 nozzle or the 9E cleanfuel nozzle, a new support ring must also beprovided. As previously mentioned, when installingthe chordal hinge stage 1 nozzle in a machine thatcurrently has the Universal stage 1 nozzle, a newsupport ring is not required because the location ofthe support ring interface is the same for bothdesigns.

Throughout the development of the MS9001 stage1 nozzle, the nozzle material, FSX-414, has not beenchanged. FSX-414 is a cobalt-base super alloy whichprovides excellent oxidation, hot corrosion andthermal fatigue resistance, and has good welding andcasting characteristics. This material’s superiorproperties warrant its continued use in thisapplication.

Stage 2 Nozzle (FS1P)The original MS9001B stage 2 nozzle had a

tendency to creep as reflected in the tangentialdownstream deflection (Figure 24), resulting in morefrequent nozzle repairs. In order to minimize thetangential deflection, a series of design changes wereimplemented. The first step was to add internal coreplug air-cooling to the nozzle, which resulted in adecrease in metal surface temperature. All MS9001Eunits have air-cooled stage 2 nozzles.

The next major change was to increase the chordlength (Figure 25), which reduced stress levels in thevanes and improved creep resistance. In late 1991,the original nozzle material (FSX-414) was replacedwith GTD-222, a nickel-base alloy previouslydescribed, because of its superior creep strength.Figure 26 provides a comparison of the nozzle creepdeflection of GTD-222 and FSX-414. An aluminidecoating was added to protect against hightemperature oxidation.

With the material change to GTD-222, lesscooling flow for the nozzle was required, due to thematerial’s superior high temperature creep properties.The cooling was decreased by inserting a longertuning pin in the stage 1 shroud and decreasing thesize of the cooling hole in the aft face of the shroud.For better distribution of cooling air, the nozzle coreplug was redesigned and the size of the pressure sidecooling holes was decreased. Reducing the coolingflow yields an increase in output. The MS9001E willsee an increase in output of approximately 1.0% with

either the one- or two-piece stage 1 shroud with newtuning pins in conjunction with the GTD-222 stage 2nozzle. (The original one piece shroud must have theaft cooling hole size reduced in order to realize thefull performance benefit). Because the existingMS9001B stage 2 nozzle is not air cooled, installingthis air-cooled stage 2 nozzle will result in an outputloss of approximately 1.0% due to the air extractedfrom the system for cooling airflow.

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GE is currently developing a brush seal for thestage 2 nozzle diaphragm based on the success of theHigh Pressure Packing and No. 2 bearing brushseals. The seal between the diaphragm and the 1-2spacer regulates the amount of cooling air flowbetween the first aft and the second forwardwheelspaces. The current seal is a labyrinth seal witha series of short and long teeth on the diaphragm andhigh and low lands with teeth on the spacer. Thestage 2 nozzle cooling air comes in through the stage1 shroud and enters the nozzle core plug via theplenum formed between the outer sidewall of thenozzle and the turbine shell. The air flows throughthe nozzle core plug; some of the air exits the nozzlevia the trailing edge cooling holes and the remainderof the cooling air flows into the cavity between thediaphragm and the nozzle. This air flows to the firstaft wheelspace and through the diaphragm/spacerseal (inner stage packing) to the second forwardwheelspace.

Our experience on MS7001 and MS9001 gasturbines shows that these wheelspace temperaturesrun significantly cooler than the design limit. Basedon this experience, the cooling flow can be reducedproviding additional output without affecting partslife. The brush seal design will utilize a brush seal inplace of the middle long tooth on the diaphragm. Thisbrush seal is expected to provide a performanceimprovement due to the reduction in cooling flow.

This design is currently being tested on anMS7001EA; test results should be available by theend of 4Q 1997. The stage 2 nozzle diaphragmbrush seal for the MS9001E will be available by 3Q1998.

Stage 3 Nozzle (FS1R)The original stage 3 nozzle, like the stage 2 nozzle,

experienced tangential deflection. In order to decreasethe tangential deflection, thus minimizing the creep,three design changes were made. First, the chordlength was increased to reduce overall airfoil stresslevels. Secondly, an internal airfoil rib, similar to theone for the stage 1 nozzle, was added to provideadditional stability and increase the component’sbuckling strength. Finally, in 1992, the material waschanged from FSX-414 to GTD-222. Unlike thestage 2 nozzle, an aluminide coating is not necessarydue to lower temperatures seen in stage 3. Since thisnozzle is not aircooled there is no performancebenefit like the stage 2 nozzle.

SHROUD BLOCKS

Stage 1 Shroud Blocks (FS2C)The stage 1 shroud block was redesigned for the

MS9001E 2055°F/ 1124°C firing temperature uprate

Film Cooling Relocated to Cover Distressed Area

GT24895

Current Design Redesign

Figure 21. Stage 1 nozzle improved outer sidewall film cooling

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program in 1991 (Figure 27) and consists of twopieces rather than one. The original one piece designdid not provide adequate LCF life at the higher firingtemperature. The two piece design is film cooledusing airflow from the stage 2 nozzle to inhibitcracking. The film cooling required additional flowwhich translates into a performance loss. Thisperformance loss can be regained by installing theGTD-222 stage 2 nozzle with the appropriate tuningpins for the stage 1 shroud. The two-piece stage 1shroud design is only required for the2055°F/1124°C firing temperature.

The main advantage of the two piece design is thatit allows the damaged caps to be replaced withouthaving to remove the shroud block bodies or turbinenozzles. Each piece of the shroud block is made of adifferent material. The body and hook fit are made of310 stainless steel and the cap is made of FSX-414.

GE is currently developing a new one piece designshroud to regain the lost performance associated withthe two piece design. This new shroud will be madeof Haynes HR-120 which, in conjunction with somedesign modifications to the original one piece design,will provide sufficient LCF life at 2055°F firingtemperature. The new design will also incorporateimproved inter-segment seals to reduce leakage. Thismaterial is used in the latest design stage 1 shroud forthe MS6001B as well as the MS7001EA. Thisdesign will be available in early 1998.

Stage 2 and 3 Shroud Blocks (FS2Tand FS2U)

Stage 2 and 3 shroud blocks provide bucket tipsealing. The original seal was labyrinth seal. In aneffort to provide better sealing in this area,honeycomb material was recently applied to both thestage 2 and 3 shrouds. Honeycomb seals are designedto reduce bucket tip leakage, resulting in animprovement heat rate and output. Honeycombshrouds are illustrated in Figure 28.

Honeycomb will allow contact between the buckettip and casing shrouds during transient operation andwill provide relatively tight clearances during steadystate operation. The cold clearances for the labyrinthseal were set based on avoiding contact between theshrouds and the bucket tips during transients.Honeycomb seals are designed for contact betweenthe bucket tips and shrouds to occur duringtransients, thus providing relatively tighter clearancesduring steady-state operation.

Honeycomb seals are made of a high-temperature,oxidation resistant alloy with 1/8 inch cell size and 5mil foil thickness is brazed between the teeth on theshrouds. “Cutter teeth” on the leading edge of theshrouded stage 2 and 3 bucket tip rails will “cut” thehoneycomb material away when contact occursduring transients. This produces steady-state runningclearances which are, on an absolute basis, no largerthan the difference between the steady-state and thetransient clearances. The effective clearance isactually tighter than the absolute clearance, since theresulting groove in the honeycomb provides a tighterlabyrinth seal than could be obtained with solidmaterials.

Installation of honeycomb shrouds requiresbuckets with cutter teeth. As previously mentioned,current production stage 2 and 3 buckets have cutterteeth. Additionally, buckets with fewer than 48,000hours of service can have cutter teeth applied in aqualified service shop.

COMPRESSOR COMPONENTSThe first four stages of the MS9001B compressor

were completely redesigned for the MS9001E model.Because new compressor casings and all newcompressor rotor and stator blades would be requiredto upgrade the MS9001B compressor to the laterdesign compressors, this is usually not economicallyfeasible and not typically quoted as part of a turbineuprate.

Instead, the existing MS9001B compressor can bere-bladed with the same design/length blades, withspecial blade coatings or materials available forcertain applications. Until recently, a NiCad coatingwas applied to the first 8 stages of the compressor.NiCad coating helps prevent corrosion pitting on theblades by combining a tough barrier coating of nickelwith a sacrificial cadmium layer. NiCad coating hasbeen replaced by GECC1. GECC1 provides the sameprotection as NiCad without the use of cadmium.Both GECC1 and NiCad possess outstandingcorrosion resistance in neutral and sea saltenvironments.

High Pressure Packing Seal (FS2V)The seal between the compressor discharge casing

inner barrel and the compressor aft stub shaft iscalled the High Pressure Packing (HPP). The HPP isdesigned to regulate the flow of compressor dischargeair into the first forward wheel space. The HPP

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clearance determines the amount of flow to the wheelspace. Ideally this flow is limited to the amountrequired for first forward wheelspace cooling. Withthe conventional labyrinth tooth/land seal packings onthe inner barrel, the minimum clearance that can betolerated is dictated by the expected rotordisplacements during transient conditions and bywheelspace cooling requirements. If a rub does occur,the labyrinth teeth can be damaged and causeexcessive leakage through the packing. A 20 mil rubis equivalent to a loss of approximately 1% in output.

Two different designs have been used to reduceleakage through the HPP. New units built sinceApril, 1994 have shipped with a honeycomb seal onthe inner barrel (similar to the design used for stage 2and 3 shrouds previously described). Retrofittinghoneycomb seals would involve removing the rotor,and replacing the aft stub shaft with a new designwith cutter teeth. The inner barrel would also have tobe replaced. A new brush seal arrangement has beendeveloped that provides the same level ofperformance improvement associated withhoneycomb seal and requires fewer modifications tothe unit. The HPP brush seal is shown in Figure 29.

Rub-tolerant brush seals are designed to withstandrotor excursions and maintain clearances in thiscritical area. Metallic brush material is used in placeof one of the labyrinth teeth on the inner barrel. Withbrush seals at the high pressure packing, the unit willbe able to sustain initial performance levels over anextended period of time because the inevitable rubwill not increase the clearance. In order to retrofit abrush seal, the existing inner barrel must be removedand replaced with an inner barrel of a brush seal. Theinner barrel with brush seal is designed for use withthe existing compressor aft stub shaft with high/lowlands. High pressure packing brush seals, which areavailable for both the 9B and the 9E, provide 1.0%increase in output and 0.5% improvement in heat ratewhen replacing the original labyrinth design. Thehigh pressure packing brush seal provides 0.2%improvement in both output and heat rate relative tothe honeycomb design.

No. 2 Bearing Brush SealsThe Frame 9E is a three bearing machine that

includes two air seals in the No. 2 bearing housing–one on either side of the bearing. The brushes providea tighter seal than the original labyrinth seal. Sinceany air that leaks past these seals into the bearinghousing does not perform any additional work in the

turbine, any reduction in this flow will result in anincrease in performance. This upgrade has beentested in the field, but the performance benefit has notyet been quantified. Brush seals for the No. 2 bearingare illustrated in Figure 30.

HIGH-FLOW INLET GUIDEVANES (FT6B)

A widely used product of the MS7001Fdevelopment program is the GTD-450 reducedcamber, high-flow inlet guide vane shown in Figure31. The new design, introduced in 1986, was quicklyapplied across the entire GE heavy-duty product lineto enhance field unit performance. The reducedcamber, high-flow inlet guide vane is a flatter, thinnerinlet guide vane designed to increase air flow whileremaining directly interchangeable with the originalIGV. The reduced camber IGV, when open to 84°,can increase power up to 4.3% and decrease heat rateby up to 0.7% (depending on the model of the gasturbine) while improving corrosion, crack and fatigueresistance. Opening the IGVs to 86° increases theoutput an additional 0.4% at the expense of the heatrate, which will increase by 0.2%.

The enhanced IGVs have higher reliability due tothe use of a special precipitation-hardened,martensitic stainless steel, GTD-450, which isimproved over the type 403 previously used (Figure32). Material developments include increased tensilestrength, high-cycle fatigue, corrosion-fatiguestrength and superior corrosion resistance due tohigher concentrations of chromium and molybdenum.

The modification kit includes new tight clearance,self-lubricating IGV bushings. A new rack and ringassembly, which controls guide vane positioning, canbe provided for improved reliability. GTD-450 IGVsare available for the 9000IE and the 90001B.

PACKAGING OF MS9001SERIES UPRATES

Each of the advanced technology componentsdescribed can be installed in any of the existingMS9001 units with little or no modification.The major component design improvements areoutlined in Figure 33. While some of thesecomponents provide performance benefitsindividually (Figure 34), the most dramaticperformance benefits are obtained through increasesin firing temperature. Generally, increases in firing

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temperature require a series of component changesbased on the original configuration of the unit and thedesired firing temperature. Therefore, severaldifferent packages have been designed for theMS9001 to provide the maximum benefit to thecustomer. There are four packages for the MS9001Band two packages for the MS9001E. In this sectioneach of the packages will be discussed.

MS9001B Turbine Uprates (FT6X)The MS9001B turbine uprate is based on

installing current production MS9001E componentsinto the MS9001B. This uprate package containsfour different options. The performanceimprovements associated with each of these optionsare given in Figures 35 and 36. The major designimprovements associated with the componentsincluded in this uprate are outlined in Figure 33. Inaddition to improving performance, themaintenance/inspection intervals can be increased.Figure 8 contrasts the inspection intervals of theMS9001B and MS9001E for some components.

Option 1 contains the advanced technology stage 1buckets and nozzles and GTD-450 reduced camberinlet guide vanes. This option maintains the firingtemperature at 1840°F/1004°C while increasing thethermal efficiency, which decreases the exhausttemperature. This uprate option provides an increasein output of 6.4% at ISO conditions, with the IGVsopen to 86°.

Option 2 raises the firing temperature to1905°F/1040°C, which is the maximum firingtemperature that can be achieved while maintainingthe original exhaust temperature. In addition to thecomponents supplied for Option 1, this optionincludes new stage 2 buckets and nozzles, new stage1 shroud, TBC coated slot-cooled liners, Nimonictransition pieces and the Extendor combustionupgrade. The stage 2 buckets are advanced-technology GTD-111 buckets without air-cooling.Option 2 is feasible for combined-cycle applicationswhere a decrease in exhaust temperature wouldreduce the overall combined-cycle efficiency and anincrease in exhaust temperature might be limited bythe Heat Recovery Steam Generator (HRSG). Itshould be emphasized that the performance benefitsgiven in Figure 34 are based on the IGVs opened to86°, and assume that all of the options have beeninstalled.

Option 3 is designed to raise the exhausttemperature to the limit by increasing the firing

temperature to 1965°F/1074°C. In addition to thematerial provided for Options 1 and 2, stage 3buckets, nozzles, shrouds and the turbine rotor 1/2wheel spacer are also provided. Unlike Option 2, thestage 2 bucket will be air cooled. This uprate optionprovides a 18.2% increase in output at 86° IGV angleand ISO conditions.

Option 4 raises the firing temperature to2020°F/1104°C. This option includes all of thecomponents in Option 3, as well as a new exhaustframe and two 100 hp exhaust frame blowers toaccommodate the increase in exhaust temperature.Increasing the firing temperature to this level canincrease the output by 24.1% at 86° IGV angle andISO conditions.

Prior to the sale of any of these options, anengineering review of the turbine/generatorperformance will be required to ensure that the loadequipment can accommodate the increase in output.This review may indicate that the load equipmentneeds to be uprated. In many cases the generator canbe “uprated” by operating at a higher power factor.A typical MS9001B performance study is illustratedin Figure 37.

MS9001E Uprate to 2020°°F/1104°°CFiring Temperature (FT6C)

This uprate package is designed for MS9001Eunits with firing temperatures below 2020°F/1104°C.Like the MS9001B turbine uprates, this package isbased on installing the latest technology componentsinto earlier vintage machines. The material requiredfor the firing temperature increase is listed in Figure34. An engineering review of the current turbineconfiguration will be provided to determine thematerial that will be required for the uprate. Figure38 contrasts the combustion inspection intervals forvarious combustion systems with and withoutExtendorTM.

The increase in output associated with the uprateis also dependent upon the original configuration ofthe unit. Figures 35 and 36 provide the performancegains associated with each of the components as wellas the entire uprate package. Again, it is importantthat the turbine/generator be evaluated to determine ifthe current load equipment can withstand the increasein output associated with this uprate.

MS9001E Uprate to 2055°°F/1124°°CFiring Temperature (FT6Y)

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This uprate package is designed for MS9001Eunits with firing temperatures below 2055°F/1124°C.This package will provide the advanced technologycomponents to increase the firing temperature of anearlier vintage MS9001E to 2055°F/1124°C, thehighest firing temperature available on an MS9001E.The material required for the firing temperatureincrease is listed in Figure 34. The material requiredfor a given unit will vary depending on the currentturbine configuration. An engineering review candefine the material that will be required for theuprate.

The increase in output associated with the uprateis dependent upon the original configuration of theunit. Figures 35 and 36 provide the performancegains associated with each of the components as wellas the entire uprate package. Again, it is importantthat the turbine/generator be evaluated to determine ifthe current load equipment can withstand the increasein output associated with this uprate.

ABSOLUTE PERFORMANCEGUARANTEES

The performance uprates discussed in this paperare based on airflow or firing temperature increasesdirectly related to performance increases, expressedas “percentage” or “delta” increases. Quantifyingturbine performance degradation is difficult due tothe lack of consistent and valid field data. In addition,several variables exist; including site conditions andmaintenance characteristics, operation modes, etc.which affect turbine performance and degradationtrends. Delta uprates, providing a percentage change,are consistent with or without turbine degradationfactors. Absolute guarantees must factor indegradation losses to calculate the final expectedperformance level. Therefore, the absoluteperformance guarantees offered usually appearslightly different than delta percentage changes inorder to account for turbine degradation.

LIFE EXTENSIONOwners can also take advantage of technology

improvements by using state-of-the-art components toreplace older component designs during major and/or hotgas path inspections instead of replacing in kind. Theadvanced technology components yield an increasedservice life when used in machines that fire attemperatures lower than that for which the componentwas designed.

EMISSIONSEmission levels are affected when the gas turbine

is uprated, and these levels must be accounted for inplanning. Emission control options reduce theemission levels, and Figure 39 compares typical NOxemission levels before and after uprates for many ofthe options discussed. Individual site requirementsand specific emission levels can be provided with anyuprate study.

CONTROL SYSTEMSUPGRADES

The MS9001 turbines are controlled by theSPEEDTRONIC™ Mark I through Mark Vgeneration controls. Several control systemenhancements and upgrades are available for allvintages of gas turbine control systems. More reliableoperation is offered by today’s superior controltechnology. Enhanced operating control can berealized by units with older control systems. “ControlSystem Upgrades for Existing Gas Turbines in the1990s” (GER-3659) details available control andinstrumentation upgrades available for the MS9001series.

MS9001 Uprate ExperienceThe MS9001B is a scaled version of the

MS7001B and the MS9001E is a scaled version ofthe MS7001E; therefore, the confidence level on theMS9001B/E uprate is very high based on asuccessful history in MS7001B/E uprate experience.

GE has successfully uprated twelve sets ofcomplete MS7001B/EA uprate hardware on fieldunits. Figure 40 lists the MS7001 uprate experiencelist to date. Additionally, dozens of upgrades anduprates are being reviewed with customerscontinually. Yet, many other customers have chosento install current design 7EA components as singlespare parts replacements just as components arerequired.

The first MS9001E to 2055°F/1124°C uprate wassuccessfully completed at ESB Ireland in 1990.Because this was the first uprate of its kind, extensivetesting was completed to monitor compressorperformance and start-up characteristics. Uponsuccessful testing it was concluded that the 9E to2055°F/1124°C uprate program would be offered.To date the uprate at ESB is the only full unit firingtemperature uprate package that GE has completed,

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however dozens of customers have realized theperformance benefits associated with many of thelatest technology components on a individual basis.

INSTALLING INDIVIDUALMS9001E PARTS FOR

UPGRADE/MAINTENANCESome customers may prefer to order certain

components only as individual parts. For thesecustomers, GE can develop a staged uprate programto meet their individual needs. Design technologybenefits, and material and maintenance improvementsallow upgrade components to be integrated on anindividual basis as an alternative to a complete upratepackage. As new technology parts are installed,completion of the uprate can be scheduled andcontrols modified to achieve the new design firingtemperature or other uprate objectives.

SUMMARYGE has an advanced technology uprate package

available to uprate all GE design MS9001 heavy-duty gas turbines. These advanced uprate technologypackages provide significant savings derived fromreduced maintenance, improved efficiency, output,reliability and life extension. Regulatoryrequirements may necessitate the need for emissioncontrols due to changes in emission levels whenuprating the gas turbine, and modifications areavailable to significantly reduce emissions. Today’stechnology and enhanced production componentsallow customers to bring their aging turbines back tobetter than new condition based upon these offerings.

REFERENCES1. Beltran, A.M., Pepe, J.J. and Schilke, P.W.,

“Advanced Gas Turbines Materials andCoatings,” GER-3569, GE Industrial & PowerSystems, August 1994.

2. Brandt, D.E. and Wesorick, R.R., “GE GasTurbine Design Philosophy,” GER-3434, GEIndustrial & Power Systems, August 1994.

3. Brooks, F.J., “GE Gas Turbine PerformanceCharacteristics,” GER-3567, GE Industrial &Power Systems, August 1994.

4. Davis, L.B., “Dry Low NOx CombustionSystems For Heavy-Duty Gas Turbines,” GER-

3568, GE Industrial & Power Systems, August1994.

5. Dunne, P.R., “Uprate Options for the MS7001Heavy-Duty Gas Turbine,” GER-3808, GEIndustrial and Power Systems, 1995.

6. Johnston, J.R., “Performance and ReliabilityImprovements for Heavy-Duty Gas Turbines,”GER-3571, GE Industrial & Power Systems,August 1994.

7. GEA-12526 (8/95), 12220.1 (1/94) MS9001EGas Turbines: Conversions, Modifications andUprates.