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UPRATE OPTIONS FOR THE

MS900A HEAVY-DUTY GAS TURBINEJennifer E. Gill

GE Power Systems

Schenectady, NY

ABSTRACTThe GE MS9001 heavy-duty gas turbine has gone

through a series of uprates since its original

introduction to the market in 1975. These uprates are

made possible by technology advances in the design

of new machines based on information accumulated

through tens of thousands of fired hours, new

materials and GE’s continuing research.

This paper will discuss evolutionary design

advances in critical components for the GE MS9001

series of turbines. It will also discuss how the latest“E” technology advances can be applied to enhance

the performance, extend the life and provide

economic benefits by increased reliability and

maintainability of all earlier MS9001B and

MS9001E turbines.

The following “E” technology uprate packages

will 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°C

The paper also describes options for reducing

emissions, tradeoffs and expected reductions, and,

GE programs for uprating, either as a single project

or phased in over time.

INTRODUCTIONThe past decade has seen unprecedented pressures

on both utilities and independent power producers to

hold the line on new investments, to become more

effective in operations and maintenance, and to bemore efficient in producing power. Modernizing and

uprating their installed fleet of turbines is emerging

as an economically attractive solution. An uprate

offers these benefits:

• Performance improvements in output and heat

rate

• Extension of inspection intervals while

shortening 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 extension

Uprates are made possible as a result of GE’s

underlying design philosophy which is to maintain

interchangeability of components for a given frame

size such that components can be installed in earlier 

vintage units with little or no modifications. Installing

the latest technology hardware and taking advantange

of the highest firing temperatures allowsowners/operators to remain competitive in the

marketplace. Virtually every key component in the

MS9001 series has gone through significant design

improvements since the first MS9001B was shipped

in 1975. Buckets, nozzles, shrouds and combustion

components have undergone multiple evolutions

 based on new designs, manufacturing techniques,

materials and field experience. Figure 1 illustrates the

 basic MS9001E configuration.

Uprates make very good investments, with most

exhibiting prompt payback. Each turbine application

must be evaluated on its own merits, but paybacks

under two years have been registered. Uprates can be

 phased in according to the outage schedule, or 

installed in a single outage, with appropriate advance

scheduling.

Gas Turbine reference codes (e.g., FT5X for an

MS9001 B to E advanced technology uprate have

 been added to the text and to many of the figures and

tables for easier correlation to other published

information on specific uprate packages or 

components.

MS9001 HISTORYThe first MS9001, shipped in 1975 as a model

MS9001B for the 50 Hz market, incorporated design

experience from the successful MS7001B. Operating

with a design firing temperature of 1840 F/1004 C

(base load), the same firing temperature as the

MS7001B, the MS9001B design represented an

increase of 42% in output over the MS7001B. This

introductory design incorporated the air-cooled stage

1 buckets and nozzles and stage 2 bucket material

improvements based on the MS7001B design

experience gained prior to 1975. As seen in Figure 2,

the output of the MS9001 has increased by 45% based on technology improvements through 1994, not

including the EC or F/FA product lines.

Introduced in 1978, the MS9001E, incorporated

the experience gained from MS7001E production and

operation as well as the design improvements that

had evolved since the MS9001B was first introduced.

The introductory firing temperature was

1955°F/1068°C.

As apparent from performance increases, the

MS9001E has seen many design improvements since

it was introduced as an MS9001B, with one obvious

change being the increased firing temperature.

Advances in materials, coating and cooling

technology have supported a series of firing

temperature increases. The current firing

temperature of the latest MS9001E is

2055°F/1124°C. All earlier vintage MS9001E gas

turbines can be uprated to the 2055°F/1124°C firing

temperature.

CURRENT MS9001E

COMPONENT TECHNOLOGYProduct technology derived from ongoing new

 product development, field service reports and new

materials and techniques has resulted in

improvements to combustion liners, transition pieces,

high flow inlet guide vanes and all stages of buckets,

nozzles and shrouds.

The component improvements can be applied

individually or as a complete uprate package,

depending on schedule, budget and machine

condition. Design improvements and rationale will be

described, as well as their effect on performance andmaintenance.

COMBUSTION SYSTEM

COMPONENTSEfforts to advance the combustion system are

driven by the need for higher firing temperatures and

for compliance with regulatory requirements to

reduce 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/hr 106 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/hr kJ/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 pieces

with sophisticated materials and processing

requirements. Combustion system upgrades can be

supplied as a package or as individual options.Depending on the option chosen and other machine

conditions, upgraded combustion system components

 produce substantial improvements in component life

and/or for extensions in recommended combustion

inspection 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 cooled

through louvered punches in the liner body. The body

could experience cracking due to stresses inherently

introduced during the manufacturing process. The

louvered liner was replaced with a slot-cooled liner 

with the introduction of the first MS9001E. Both

liners are shown in Figure 3. The slot-cooled liner 

 provides a more uniform distribution of cooling air flow for better overall cooling. Air enters the cooling

holes, impinges on the brazed ring and discharges

from the internal slot as a continuous cooling film.

The liner material is Hastelloy-X, a nickel-base

alloy, which has not changed since the introduction of 

the MS9001B in 1975. Today, however, a thermal

 barrier coating (TBC) is applied to the liners. The

TBC consists of two materials applied to the hot side

of a component (Figure 4): a bond coat applied to the

surface of the part and an insulating oxide applied

over the bond coat. This TBC provides a 0.015-inch

insulating layer that reduces the underlying base

material temperature by approximately 100°F/38°C.

The addition of TBC also mitigates the effects of 

uneven temperature distribution across the metal.

With the MS9001E firing temperature increase to

2055°F/1124°C, the thickness of the liner was also

increased by approximately 10 mils to accommodate

the higher temperatures.

Transition Piece (FR1D)

GT24927.ppt

Slot-CooledLiner 

LouveredLiner 

Figure 3. Improved slot-cooled liner vs. original

louvered 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 parallel

system, 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” system

consisting 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 which

the combustion gases had to flow, thus providing a

more direct flow path. The canted design made it possible to shorten the transition section of the

transition piece, and therefore shorten the overall

length of the transition piece.

When the firing temperature was increased to

2055°F/1124°C, the “canted” arrangement was

upgraded to the “canned” arrangement. The “canned”

arrangement consists of a longer transition piece with

a thicker slot-cooled liner, as previously mentioned.

The longer transition piece essentially pushes the

liner out of the wrapper. Outer combustion casings as

seen in Figure 5. The transition piece was lengthened

 by adding a 15-inch long cylinder to the forward end.

While the transition piece length was increased, the

curved section remained the same, thereby retaining

its stiffness. The transition piece was lengthened to

relocate the transition piece-liner interface, in order to

minimize wear induced by the compressor discharge

flow. Figure 5 illustrates the differences between the

current 9E production “canned” arrangement, the 9E

“canted arrangement and the 9B parallel combustor.

Early 9B turbines utilized a thin-walled transition

 piece constructed of Hastelloy-X material. The

original 9E transition piece was a thick- walledHastelloy-X. In the mid 1980s, the transition piece

MS9001B Parallel Arrangement

MS9001E Canted Arrangement

GT25006.ppt

MS9001E Canned Arrangement

Figure 5. MS9001 combustion system comparison

Old Design Aft Bracket

GT21369A.ppt

Redesigned Aft Bracket

TransitionPiece

TransitionPiece

 AftEnd

Figure 6. Comparison of transition piece aft bracket

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material was changed to Nimonic 263 which is a

nickel-base alloy with better strength characteristics

than Hastelloy-X. Nimonic 263 demonstrated

superior creep life and could increase the inspection

interval to 12,000 hours. The Nimonic 263 transition

 pieces are coated with thermal barrier material,

thereby reducing metal temperatures and increasing

component life.

The Nimonic 263 transition piece has a positive

curvature body and aft bracket that reduces cracking

at the bracket weld area by allowing the transition

 piece to pivot about the pin during thermal cycles. Acomparison of the original and redesigned aft bracket

design is shown in Figure 6.

GE has recently designed a new Nimonic transition

 piece for the MS9001B to provide a substantial

increase in creep strength over the current design.

The uprate potential of the current MS9001B

machines is limited by the inability of the current

transition piece to withstand higher firing

temperatures. This improved transition piece enables

these units to be uprated beyond their current rated

firing temperature. Additionally, this improved

transition piece is required for these units to realize

the full benefits of the Extendor™ Combustion

System.

Extendor™ Combustion System

(FR1V/FR1W)

All GE heavy-duty gas turbines require periodic

combustion inspections due to TBC coating erosion,

wear and material creep. GE has developed a product

 – Extendor™ – to increase combustion inspection

intervals. The Extendor™ combustion system, shown

in Figure 7, decreases combustion component wear 

and increases combustion inspection intervals by

reducing the relative movement and associated wear 

of parts in the combustion system. Application of the

Extendor™ wear system extends transition piece

inspection intervals up to 24,000 hours. Figure 8

details the improved combustion wear inspection

intervals.

Customer savings occur with the elimination of labor costs associated with combustion inspections

and reduction of component repair costs. Extendor™

can be applied as a component modification during

routine maintenance or as a complete retrofit.

Extendor™ is currently available for MS9001 series

gas turbines with slot-cooled liners and Nimonic

transition pieces.

Dry Low NOx Combustion System

(FG2B)

Customers without diluent supplies for injection

 purposes can achieve NOx  emission requirements

through the use of Dry Low NOx  combustors. The

DLN combustion system for the MS9001E is shown

in Figure 9. The DLN combustion system reduces

 NOx  emissions without steam or water injection on

gas fuel units. This is done by fuel staging, with lean

fuel 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 lower 

temperature rises across the combustor.

The DLN combustor (Figure 10) has six

individual fuel nozzles in the primary combustion

zone, and a single fuel nozzle in the secondary

combustion zone. The DLN combustion system

offers lower NOx  emission levels on gas fuel-fired

units without parts life reduction associated withwaer or steam injection NOx  reduction systems.

Emission levels of 15 ppmvd at 15% O2 or less can

 be reached by using the DLN combustion system.

TURBINE COMPONENTSThere have been significant design and material

improvements made to the turbine components since

the first MS9001B was manufactured. The improved

component designs can withstand higher firing

temperatures due to advanced materials and coatings,

as well as the addition of air cooling for some of the

components. This section will describe the evolution

of these technologies. The latest technology

components now used in current production

MS9001E 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 the

leading edge, which reduces thermal gradients and,

therefore, cracks. The Blunt Leading Edge (BLE)

design, shown in Figure 11, was used as the first

MS9001E stage 1 bucket.

Materials.

The original MS9001B stage 1 bucket was IN-738, a precipitation-hardened, nickel-base super 

alloy. In 1987, the material was changed to an

Equiaxed (E/A) GTD-111, also a precipitation-

hardened, nickel-base super alloy, a greater low cycle

fatigue strength than IN-738. GTD-111 also provides

the industry standard in corrosion resistance.

Coatings.

Lean andPremixing

Primary Zone

Secondary

Fuel Nozzle(1)

PrimaryFuel Nozzles

(6)

GT15050B

Dilution ZoneSecondary Zone

Centerbody

Venturi

End 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 Fuel

Nozzle Assembly

Compressor Discharge Casing

Transition

Piece

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 Extendor  TM9E

Hours

Figure 8. Typical MS9001B vs. MS9001E

maintenance

Original Designand ThermalGradients

GT21321A.ppt

Blunt Nose BucketWith ImprovedThermal Gradients

Figure 11. Sharp and blunt leading edge bucket

design 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 of 

turbulated cooling holes, the bucket coating was

changed to GT-29 INPLUS. This coating is a

vacuum plasma spray with an aluminide coating on

the bucket exterior and the internal cooling hole

 passages. In 1997 the coating was changed again to

GT-33 INCOAT. GT-33 is a vacuum plasma spray

coating like GT-29, but offers an increased resistance

to through cracking. “INCOAT” refers to an

aluminide coating on the cooling holes passages.

GT-33 INCOAT is GE’s new standard coating for 

stage 1 buckets, however GT-29 INPLUS is stillavailable and is recommended when burning

corrosive 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 design

contains air-cooled stage 2 buckets, as shown in

Figure 12.  The addition of air cooling allows for 

higher firing temperatures. In order to replace non

air-cooled stage 2 buckets with the new air-cooled

 buckets, the 1/2 wheel spacer must be replaced with

the new design that allows air to flow to the stage 2

 bucket.

This bucket can be supplied without internal

cooling air passages as a direct part replacement for 

the MS9001B. With this option, the 1/2 wheel spacer would not have to be replaced. While lower in cost,

the non-air-cooled version of this bucket would not be

able to withstand an increase in firing temperature

above 1905°F /1040°C.

Tip Shroud.

The shroud leading edge was scalloped (Figure

13), the shroud tip was thickened between the seal

teeth, and the underside of the shroud was tapered.

Scalloping the leading edge decreased the stress at the

top 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 teeth

to the bucket tip rails. These cutter teeth were

designed for use with the new Honeycomb stage 2

shrouds. The “twisted rail” design cutter teeth,

standard on all new stage 2 buckets, essentially

rotates the tip rails by 0.5 degrees, causing the tip

rails of each bucket to be offset relative to the

 preceding and subsequent buckets. This offset createsthe cutter tooth. required with honeycomb shrouds.

During transients when the bucket tip clearance is the

smallest, the cutter teeth cut a path through the

honeycomb material in the shroud, thus minimizing

the steady-state clearance. Stage 2 buckets with

cutter teeth are required for use with honeycomb

shrouds, but can also be used with the traditional

design shrouds. Cutter teeth can also be applied to

 buckets in good condition with fewer than 48,000

hours 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 was

changed to IN-738, a precipitation-hardened, nickel-

 base super alloy which provided an increase in

elevated temperature strength and hot corrosion

resistance. In 1992, the material was changed to

GTD-111, also a precipitation-hardened, nickel-base

super alloy, to improve rupture strength. In addition

to a higher rupture strength, GTD-111 has higher low-cycle fatigue strength.

Coating.

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

INPLUS coating was added. INPLUS coating refers

to PLASMAGUARD GT-29 with an overaluminide

aluminide coating on the internal cooling passages.

Like the stage 1 bucket, the standard coating was

changed to GT-33 INCOAT in early 1997. GT-33

INCOAT consists of GT-33, a vacuum plasma spray

coating, on the exterior of the bucket and an

aluminide coating on the interior of the cooling hole

 passages. GT-33 INCOAT provides superior 

through crack resistance relative to GT-29 INPLUS.

GT-29 INPLUS is still available and is recommended

for use in corrosive fuel applications.

Stage 3 Bucket (FS2K)

The MS9001B stage 3 bucket has experienced

changes in design, manufacturing process and

material.

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 the

 performance improvements shown in Figures 35 and

36.

The trailing edge was thickened, and the chord

length increased. Like the stage 2 buckets previously

described, the shroud leading edge was scalloped, the

shroud tip was thickened between the seal teeth, and

the underside of the shroud was tapered. These design

changes resulted in an increase in creep life of the

 bucket.

Like the stage 2 buckets, the most recent change

was to add cutter teeth to the bucket tip rails. Thesecutter teeth are required for use with stage 3

honeycomb shrouds, as previously described. Current

 production stage 3 buckets include cutter teeth.

Cutter teeth can be added to the stage 3 buckets in

good condition with fewer than 48,000 hours of 

operation in a qualified service shop.

In order to use the 9E bucket on a 9B machine, the

stage 3 shrouds must be replaced or modified. Figure

15  illustrates the machining points on the shroud

which is required for the modification. Additionally,

due to interference with the angel wing,owners/operators may elect to machine the exhaust

frame to facilitate rotor removal, however it is not

required.

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 the

material. The combination of the induced and creep

strains resulted in potential creep-rupture cracks,

further propagated by high-cycle fatigue. GE

developed a new manufacturing process for theMS9001E bucket which eliminates the need for the

cold 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, a

 precipitation-hardened, nickel-base alloy. To improve

elevated temperature strength and hot corrosion

resistance, the bucket material was changed in 1992to IN-738, a precipitation-hardened, nickel-based

super alloy.

NOZZLES

Stage 1 Nozzle (FS2J)

The MS9001 stage 1 nozzle has evolved through

four generations, each improving on the preceding

one, starting with the MS9001B 4-vane nozzle. The

second generation, designed for the MS9001E, was

used primarily for clean fuel applications. The third

generation – the Universal Fuel Nozzle – was

significant because it is applicable for gas, distillate

and ash-bearing fuels. The fourth generation, known

as the Chordal Hinge Nozzle, incorporated GE

Aircraft 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 will

discuss the design improvements brought about in

each generation. A comparison of the cross-sections

of each generation is shown in Figure 16.

Several design modifications were made to the

original MS9001B stage 1 nozzle to develop the

MS9001E clean fuel stage 1 nozzle. One of the most

dramatic changes was made in response to the vanefillet cracking problem (Figure 17) caused by high

thermal stress induced by the high thermal gradient

across the sidewall/vane interface. By decreasing the

number of vanes per segment, structural redundancy

and the thermal stresses were reduced, thus

minimizing the vane fillet cracking. The original 9B

stage 1 nozzle had four vanes per segment and

required 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 the

support ring and nozzle was moved downstream.

At the same time that the number of vanes per 

segment was reduced, the shape of the airfoil was

optimized and the vanes were rotated to reduce the

throat area. The new airfoil shape and reduction in

throat area increased the pressure ratio. Installing thisdesign into an MS9001B can increase the pressure

ratio by as much as 6%.

The suction side wall thickness of the nozzle

airfoil at the pitch section was increased by 13%,

which effectively reduced the aerodynamic-induced

mechanical stress and increased the creep life of the

 part. The stress level was further reduced by the

addition of an internal center rib. The center rib is

shown in Figure 18.

The Universal Fuel Nozzle was developed from

the clean fuel nozzle in response to the need to burn

residual fuels, as well as clean fuels. The airfoil

shape was rounded making it more blunt and the

entire cooling system was redesigned. The pressure

side cooling holes were replaced with slots and placed

closer together to provide more uniform

cooling(Figure 19). Trailing edge cooling was also

added as seen in Figure 19. This improved cooling

design decreased surface metal temperature by as

much as 5% thus minimizing cracking, airfoil

 ballooning, 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 film

cooling 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 was

implemented to minimize torsional forces exerted on

the sidewall near the nozzle-retaining ring interface.

In 1992, a tangential support lug consisting of an

integrally cast side support lug with a milled radial

slot was introduced to the stage 1 nozzle inner sidewall. A support pin and bushing were also added to

secure the nozzle segment. A lockplate and a single

retainer bolt were used to keep the support pin in

 place. This arrangement provided additional

tangential support for the nozzle.

The forth and current generation of stage 1 nozzle

is the chordal hinge nozzle introduced in 1994. This

nozzle is the result of two major design changes

maintaining the philosophy of burning both clean and

heavy fuels. The first design change was made to

reduce the leakage between nozzle segments and between the nozzle and support ring. The chordal

hingewhich incorporates the latest in GE Aircraft

Engine sealing technology, was added. The chordal

hinge refers to a straight line seal on the aft face of 

the inner side wall rail which ensures that the seal is

maintained even if the nozzle rocks slightly. The

chordal hinge and the new sidewall seal design are

illustrated in Figure 20. The chordal hinge reduces

the leakage between the nozzle and the support ring.

The leakage between the nozzle segments was

decreased by improving the sidewall, or spline seals.

The second major change was to improve the

sidewall cooling. As the firing temperature increased

over the development of the MS9001E, the nozzle

was exposed to higher temperatures, causing

oxidation and erosion to occur on the sidewalls. Toreduce the oxidation and surface erosion, the cooling

effectiveness was increased. The overall cooling

effectiveness was improved by relocating some of as

seen in Figure 21.

When the chordal hinge nozzle was introduced, the

original tangential pin hardware was replaced with a

single piece bushing/tangential pin to secure the

nozzle and a flat lockplate with two retainer bolts

was used to keep the bushing/tangential pin in place

(Figure 22). More recently the tangential pin

hardware has been eliminated–field inspections haveindicated that the hardware is not required. In

addition to eliminating the hardware, the forward

flange on the support ring has been eliminated

(Figure 23). These design modifications make the

universal nozzle and chordal hinge nozzle completely

interchangeable with no support ring modifications

required.

As seen in (Figure 16), the 9B stage 1 nozzle and

the 9E clean fuel nozzle support ring interface is

Final DesignPresent Design

HookMachining

Relief 

Improved

Seal

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 or 

Chordal Hinge stage 1 nozzle. Therefore, to install

the chordal hinge stage 1 nozzle in a unit that

currently has the 9B stage 1 nozzle or the 9E clean

fuel nozzle, a new support ring must also be

 provided. As previously mentioned, when installing

the chordal hinge stage 1 nozzle in a machine that

currently has the Universal stage 1 nozzle, a newsupport ring is not required because the location of 

the support ring interface is the same for both

designs.

Throughout the development of the MS9001 stage

1 nozzle, the nozzle material, FSX-414, has not been

changed. FSX-414 is a cobalt-base super alloy which

 provides excellent oxidation, hot corrosion and

thermal fatigue resistance, and has good welding and

casting characteristics. This material’s superior 

 properties warrant its continued use in this

application.

Stage 2 Nozzle (FS1P)

The original MS9001B stage 2 nozzle had a

tendency to creep as reflected in the tangential

downstream deflection (Figure 24), resulting in more

frequent nozzle repairs. In order to minimize the

tangential deflection, a series of design changes were

implemented. The first step was to add internal core

 plug air-cooling to the nozzle, which resulted in a

decrease in metal surface temperature. All MS9001E

units have air-cooled stage 2 nozzles.

The next major change was to increase the chord

length (Figure 25), which reduced stress levels in the

vanes and improved creep resistance. In late 1991,

the original nozzle material (FSX-414) was replaced

with GTD-222, a nickel-base alloy previously

described, because of its superior creep strength.

Figure 26 provides a comparison of the nozzle creep

deflection of GTD-222 and FSX-414. An aluminide

coating was added to protect against high

temperature oxidation.

With the material change to GTD-222, less

cooling flow for the nozzle was required, due to thematerial’s superior high temperature creep properties.

The cooling was decreased by inserting a longer 

tuning pin in the stage 1 shroud and decreasing the

size of the cooling hole in the aft face of the shroud.

For better distribution of cooling air, the nozzle core

 plug was redesigned and the size of the pressure side

cooling holes was decreased. Reducing the cooling

flow yields an increase in output. The MS9001E will

see an increase in output of approximately 1.0% with

either the one- or two-piece stage 1 shroud with new

tuning pins in conjunction with the GTD-222 stage 2

nozzle. (The original one piece shroud must have the

aft cooling hole size reduced in order to realize the

full performance benefit). Because the existing

MS9001B stage 2 nozzle is not air cooled, installing

this air-cooled stage 2 nozzle will result in an output

loss 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 the

stage 2 nozzle diaphragm based on the success of the

High Pressure Packing and No. 2 bearing brush

seals. The seal between the diaphragm and the 1-2

spacer regulates the amount of cooling air flow

 between the first aft and the second forward

wheelspaces. The current seal is a labyrinth seal with

a series of short and long teeth on the diaphragm and

high and low lands with teeth on the spacer. Thestage 2 nozzle cooling air comes in through the stage

1 shroud and enters the nozzle core plug via the

 plenum formed between the outer sidewall of the

nozzle and the turbine shell. The air flows through

the nozzle core plug; some of the air exits the nozzle

via the trailing edge cooling holes and the remainder 

of the cooling air flows into the cavity between the

diaphragm and the nozzle. This air flows to the first

aft wheelspace and through the diaphragm/spacer 

seal (inner stage packing) to the second forward

wheelspace.

Our experience on MS7001 and MS9001 gas

turbines shows that these wheelspace temperatures

run significantly cooler than the design limit. Based

on this experience, the cooling flow can be reduced

 providing additional output without affecting parts

life. The brush seal design will utilize a brush seal in

 place of the middle long tooth on the diaphragm. This

 brush seal is expected to provide a performance

improvement due to the reduction in cooling flow.

This design is currently being tested on an

MS7001EA; test results should be available by the

end of 4Q 1997. The stage 2 nozzle diaphragm

 brush seal for the MS9001E will be available by 3Q

1998.

Stage 3 Nozzle (FS1R)

The original stage 3 nozzle, like the stage 2 nozzle,experienced tangential deflection. In order to decrease

the tangential deflection, thus minimizing the creep,

three design changes were made. First, the chord

length was increased to reduce overall airfoil stress

levels. Secondly, an internal airfoil rib, similar to the

one for the stage 1 nozzle, was added to provide

additional stability and increase the component’s

 buckling strength. Finally, in 1992, the material was

changed from FSX-414 to GTD-222. Unlike the

stage 2 nozzle, an aluminide coating is not necessary

due to lower temperatures seen in stage 3. Since this

nozzle is not aircooled there is no performance benefit 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 two

 pieces rather than one. The original one piece design

did not provide adequate LCF life at the higher firing

temperature. The two piece design is film cooled

using airflow from the stage 2 nozzle to inhibit

cracking. The film cooling required additional  flow

which translates into a performance loss. This

 performance loss can be regained by installing theGTD-222 stage 2 nozzle with the appropriate tuning

 pins for the stage 1 shroud. The two-piece stage 1

shroud design is only required for the

2055°F/1124°C firing temperature.

The main advantage of the two piece design is that

it allows the damaged caps to be replaced without

having to remove the shroud block bodies or turbine

nozzles. Each piece of the shroud block is made of a

different material. The body and hook fit are made of 

310 stainless steel and the cap is made of FSX-414.

GE is currently developing a new one piece design

shroud to regain the lost performance associated with

the two piece design. This new shroud will be made

of Haynes HR-120 which, in conjunction with some

design modifications to the original one piece design,

will provide sufficient LCF life at 2055°F firing

temperature. The new design will also incorporate

improved inter-segment seals to reduce leakage. This

material is used in the latest design stage 1 shroud for 

the MS6001B as well as the MS7001EA. This

design will be available in early 1998.

Stage 2 and 3 Shroud Blocks (FS2Tand FS2U)

Stage 2 and 3 shroud blocks provide bucket tip

sealing. The original seal was labyrinth seal. In an

effort to provide better sealing in this area,

honeycomb material was recently applied to both the

stage 2 and 3 shrouds. Honeycomb seals are designed

to reduce bucket tip leakage, resulting in an

improvement heat rate and output. Honeycomb

shrouds are illustrated in Figure 28.

Honeycomb will allow contact between the bucket

tip and casing shrouds during transient operation and

will provide relatively tight clearances during steady

state operation. The cold clearances for the labyrinth

seal were set based on avoiding contact between the

shrouds and the bucket tips during transients.

Honeycomb seals are designed for contact between

the bucket tips and shrouds to occur during

transients, thus providing relatively tighter clearances

during steady-state operation.

Honeycomb seals are made of a high-temperature,

oxidation resistant alloy with 1/8 inch cell size and 5

mil foil thickness is brazed between the teeth on the

shrouds. “Cutter teeth” on the leading edge of the

shrouded stage 2 and 3 bucket tip rails will “cut” the

honeycomb material away when contact occurs

during transients. This produces steady-state running

clearances which are, on an absolute basis, no larger than the difference between the steady-state and the

transient clearances. The effective clearance is

actually tighter than the absolute clearance, since the

resulting groove in the honeycomb provides a tighter 

labyrinth seal than could be obtained with solid

materials.

Installation of honeycomb shrouds requires

 buckets with cutter teeth. As previously mentioned,

current production stage 2 and 3 buckets have cutter 

teeth. Additionally, buckets with fewer than 48,000

hours of service can have cutter teeth applied in a

qualified service shop.

COMPRESSOR COMPONENTSThe first four stages of the MS9001B compressor 

were completely redesigned for the MS9001E model.

Because new compressor casings and all new

compressor rotor and stator blades would be required

to upgrade the MS9001B compressor to the later 

design compressors, this is usually not economically

feasible and not typically quoted as part of a turbine

uprate.Instead, the existing MS9001B compressor can be

re-bladed with the same design/length blades, with

special blade coatings or materials available for 

certain applications. Until recently, a NiCad coating

was applied to the first 8 stages of the compressor.

 NiCad coating helps prevent corrosion pitting on the

 blades by combining a tough barrier coating of nickel

with a sacrificial cadmium layer. NiCad coating has

 been replaced by GECC1. GECC1 provides the same

 protection as NiCad without the use of cadmium.

Both GECC1 and NiCad possess outstanding

corrosion 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 is

called the High Pressure Packing (HPP). The HPP is

designed to regulate the flow of compressor discharge

air into the first forward wheel space. The HPP

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clearance determines the amount of flow to the wheel

space. Ideally this flow is limited to the amount

required for first forward wheelspace cooling. With

the conventional labyrinth tooth/land seal packings on

the inner barrel, the minimum clearance that can be

tolerated is dictated by the expected rotor 

displacements during transient conditions and by

wheelspace cooling requirements. If a rub does occur,the labyrinth teeth can be damaged and cause

excessive leakage through the packing. A 20 mil rub

is equivalent to a loss of approximately 1% in output.

Two different designs have been used to reduce

leakage through the HPP. New units built since

April, 1994 have shipped with a honeycomb seal on

the inner barrel (similar to the design used for stage 2

and 3 shrouds previously described). Retrofitting

honeycomb seals would involve removing the rotor,

and replacing the aft stub shaft with a new design

with cutter teeth. The inner barrel would also have to

 be replaced. A new brush seal arrangement has been

developed that provides the same level of 

 performance improvement associated with

honeycomb seal and requires fewer modifications to

the unit. The HPP brush seal is shown in Figure 29.

Rub-tolerant brush seals are designed to withstand

rotor excursions and maintain clearances in this

critical area. Metallic brush material is used in place

of one of the labyrinth teeth on the inner barrel. With

 brush seals at the high pressure packing, the unit will

 be able to sustain initial performance levels over an

extended period of time because the inevitable rubwill not increase the clearance. In order to retrofit a

 brush seal, the existing inner barrel must be removed

and replaced with an inner barrel of a brush seal. The

inner barrel with brush seal is designed for use with

the existing compressor aft stub shaft with high/low

lands. High pressure packing brush seals, which are

available for both the 9B and the 9E, provide 1.0%

increase in output and 0.5% improvement in heat rate

when replacing the original labyrinth design. The

high pressure packing brush seal provides 0.2%

improvement in both output and heat rate relative to

the honeycomb design.

No. 2 Bearing Brush Seals

The 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 provide

a tighter seal than the original labyrinth seal. Since

any air that leaks past these seals into the bearing

housing does not perform any additional work in the

turbine, any reduction in this flow will result in an

increase in performance. This upgrade has been

tested in the field, but the performance benefit has not

yet been quantified. Brush seals for the No. 2 bearing

are illustrated in Figure 30.

HIGH-FLOW INLET GUIDEVANES (FT6B)

A widely used product of the MS7001F

development program is the GTD-450 reduced

camber, high-flow inlet guide vane shown in Figure

31. The new design, introduced in 1986, was quickly

applied across the entire GE heavy-duty product line

to enhance field unit performance. The reduced

camber, high-flow inlet guide vane is a flatter, thinner 

inlet guide vane designed to increase air flow while

remaining directly interchangeable with the original

IGV. The reduced camber IGV, when open to 84°,can increase power up to 4.3% and decrease heat rate

 by up to 0.7% (depending on the model of the gas

turbine) while improving corrosion, crack and fatigue

resistance. Opening the IGVs to 86° increases the

output an additional 0.4% at the expense of the heat

rate, which will increase by 0.2%.

The enhanced IGVs have higher reliability due to

the use of a special precipitation-hardened,

martensitic stainless steel, GTD-450, which is

improved over the type 403 previously used (Figure

32). Material developments include increased tensile

strength, high-cycle fatigue, corrosion-fatiguestrength and superior corrosion resistance due to

higher concentrations of chromium and molybdenum.

The modification kit includes new tight clearance,

self-lubricating IGV bushings. A new rack and ring

assembly, which controls guide vane positioning, can

 be provided for improved reliability. GTD-450 IGVs

are available for the 9000IE and the 90001B.

PACKAGING OF MS9001

SERIES UPRATESEach of the advanced technology componentsdescribed can be installed in any of the existing

MS9001 units with little or no modification.

The major component design improvements are

outlined in Figure 33. While some of these

components provide performance benefits

individually (Figure 34), the most dramatic

 performance benefits are obtained through increases

in firing temperature. Generally, increases in firing

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temperature require a series of component changes

 based on the original configuration of the unit and the

desired firing temperature. Therefore, several

different packages have been designed for the

MS9001 to provide the maximum benefit to the

customer. There are four packages for the MS9001B

and two packages for the MS9001E. In this section

each of the packages will be discussed.

MS9001B Turbine Uprates (FT6X)

The MS9001B turbine uprate is based on

installing current production MS9001E components

into the MS9001B. This uprate package contains

four different options. The performance

improvements associated with each of these options

are given in Figures 35 and 36. The major design

improvements associated with the components

included in this uprate are outlined in Figure 33. In

addition to improving performance, themaintenance/inspection intervals can be increased.

Figure 8  contrasts the inspection intervals of the

MS9001B and MS9001E for some components.

Option 1 contains the advanced technology stage 1

 buckets and nozzles and GTD-450 reduced camber 

inlet guide vanes. This option maintains the firing

temperature at 1840°F/1004°C while increasing the

thermal efficiency, which decreases the exhaust

temperature. This uprate option provides an increase

in output of 6.4% at ISO conditions, with the IGVs

open to 86°.Option 2 raises the firing temperature to

1905°F/1040°C, which is the maximum firing

temperature that can be achieved while maintaining

the original exhaust temperature. In addition to the

components supplied for Option 1, this option

includes new stage 2 buckets and nozzles, new stage

1 shroud, TBC coated slot-cooled liners, Nimonic

transition pieces and the Extendor combustion

upgrade. The stage 2 buckets are advanced-

technology GTD-111 buckets without air-cooling.

Option 2 is feasible for combined-cycle applications

where a decrease in exhaust temperature wouldreduce the overall combined-cycle efficiency and an

increase in exhaust temperature might be limited by

the Heat Recovery Steam Generator (HRSG). It

should be emphasized that the performance benefits

given in Figure 34 are based on the IGVs opened to

86°, and assume that all of the options have been

installed.

Option 3 is designed to raise the exhaust

temperature to the limit by increasing the firing

temperature to 1965°F/1074°C. In addition to the

material provided for Options 1 and 2, stage 3

 buckets, nozzles, shrouds and the turbine rotor 1/2

wheel spacer are also provided. Unlike Option 2, the

stage 2 bucket will be air cooled. This uprate option

 provides a 18.2% increase in output at 86° IGV angle

and ISO conditions.

Option 4 raises the firing temperature to2020°F/1104°C. This option includes all of the

components in Option 3, as well as a new exhaust

frame and two 100 hp exhaust frame blowers to

accommodate the increase in exhaust temperature.

Increasing the firing temperature to this level can

increase the output by 24.1% at 86° IGV angle and

ISO conditions.

Prior to the sale of any of these options, an

engineering review of the turbine/generator 

 performance will be required to ensure that the load

equipment can accommodate the increase in output.This review may indicate that the load equipment

needs to be uprated. In many cases the generator can

 be “uprated” by operating at a higher power factor.

A typical MS9001B performance study is illustrated

in Figure 37.

MS9001E Uprate to 2020°°F/1104°°C

Firing Temperature (FT6C)

This uprate package is designed for MS9001E

units with firing temperatures below 2020°F/1104°C.

Like the MS9001B turbine uprates, this package is based on installing the latest technology components

into earlier vintage machines. The material required

for the firing temperature increase is listed in Figure

34. An engineering review of the current turbine

configuration will be provided to determine the

material that will be required for the uprate. Figure

38  contrasts the combustion inspection intervals for 

various combustion systems with and without

Extendor TM

.

The increase in output associated with the uprate

is also dependent upon the original configuration of 

the unit. Figures 35 and 36 provide the performance

gains associated with each of the components as well

as the entire uprate package. Again, it is important

that the turbine/generator be evaluated to determine if 

the current load equipment can withstand the increase

in output associated with this uprate.

MS9001E Uprate to 2055°°F/1124°°C

Firing Temperature (FT6Y)

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This uprate package is designed for MS9001E

units with firing temperatures below 2055°F/1124°C.

This package will provide the advanced technology

components to increase the firing temperature of an

earlier vintage MS9001E to 2055°F/1124°C, the

highest firing temperature available on an MS9001E.

The material required for the firing temperature

increase is listed in Figure 34. The material requiredfor a given unit will vary depending on the current

turbine configuration. An engineering review can

define the material that will be required for the

uprate.

The increase in output associated with the uprate

is dependent upon the original configuration of the

unit. Figures 35 and 36  provide the performance

gains associated with each of the components as well

as the entire uprate package. Again, it is important

that the turbine/generator be evaluated to determine if 

the current load equipment can withstand the increasein output associated with this uprate.

ABSOLUTE PERFORMANCE

GUARANTEESThe performance uprates discussed in this paper 

are based on airflow or firing temperature increases

directly related to performance increases, expressed

as “percentage” or “delta” increases. Quantifying

turbine performance degradation is difficult due to

the 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 degradation

trends. Delta uprates, providing a percentage change,

are consistent with or without turbine degradation

factors. Absolute guarantees must factor in

degradation losses to calculate the final expected

 performance level. Therefore, the absolute

 performance guarantees offered usually appear 

slightly different than delta percentage changes in

order to account for turbine degradation.

LIFE EXTENSIONOwners can also take advantage of technology

improvements by using state-of-the-art components to

replace older component designs during major and/or hot

gas path inspections instead of replacing in kind. The

advanced technology components yield an increased

service life when used in machines that fire at

temperatures lower than that for which the component

was designed.

EMISSIONSEmission levels are affected when the gas turbine

is uprated, and these levels must be accounted for in

 planning. Emission control options reduce the

emission levels, and Figure 39 compares typical NOx

emission levels before and after uprates for many of 

the options discussed. Individual site requirements

and specific emission levels can be provided with any

uprate study.

CONTROL SYSTEMS

UPGRADESThe MS9001 turbines are controlled by the

SPEEDTRONIC™ Mark I through Mark V

generation controls. Several control system

enhancements and upgrades are available for all

vintages of gas turbine control systems. More reliable

operation is offered by today’s superior controltechnology. Enhanced operating control can be

realized by units with older control systems. “Control

System Upgrades for Existing Gas Turbines in the

1990s” (GER-3659) details available control and

instrumentation upgrades available for the MS9001

series.

MS9001 Uprate Experience

The MS9001B is a scaled version of the

MS7001B and the MS9001E is a scaled version of 

the MS7001E; therefore, the confidence level on theMS9001B/E uprate is very high based on a

successful history in MS7001B/E uprate experience.

GE has successfully uprated twelve sets of 

complete MS7001B/EA uprate hardware on field

units. Figure 40  lists the MS7001 uprate experience

list to date. Additionally, dozens of upgrades and

uprates are being reviewed with customers

continually. Yet, many other customers have chosen

to install current design 7EA components as single

spare parts replacements just as components are

required.The first MS9001E to 2055°F/1124°C uprate was

successfully completed at ESB Ireland in 1990.

Because this was the first uprate of its kind, extensive

testing was completed to monitor compressor 

 performance and start-up characteristics. Upon

successful testing it was concluded that the 9E to

2055°F/1124°C uprate program would be offered.

To date the uprate at ESB is the only full unit firing

temperature uprate package that GE has completed,

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however dozens of customers have realized the

 performance benefits associated with many of the

latest technology components on a individual basis.

INSTALLING INDIVIDUAL

MS9001E PARTS FOR 

UPGRADE/MAINTENANCESome customers may prefer to order certain

components only as individual parts. For these

customers, GE can develop a staged uprate program

to meet their individual needs. Design technology

 benefits, and material and maintenance improvements

allow upgrade components to be integrated on an

individual basis as an alternative to a complete uprate

 package. As new technology parts are installed,

completion of the uprate can be scheduled and

controls modified to achieve the new design firing

temperature 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 technology

 packages provide significant savings derived from

reduced maintenance, improved efficiency, output,

reliability and life extension. Regulatory

requirements may necessitate the need for emission

controls due to changes in emission levels when

uprating the gas turbine, and modifications are

available to significantly reduce emissions. Today’s

technology and enhanced production components

allow customers to bring their aging turbines back to

 better than new condition based upon these offerings.

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

“Advanced Gas Turbines Materials and

Coatings,” GER-3569, GE Industrial & Power 

Systems, August 1994.2. Brandt, D.E. and Wesorick, R.R., “GE Gas

Turbine Design Philosophy,” GER-3434, GE

Industrial & Power Systems, August 1994.

3. Brooks, F.J., “GE Gas Turbine Performance

Characteristics,” GER-3567, GE Industrial &

Power Systems, August 1994.

4. Davis, L.B., “Dry Low NOx Combustion

Systems For Heavy-Duty Gas Turbines,” GER-

3568, GE Industrial & Power Systems, August

1994.

5. Dunne, P.R., “Uprate Options for the MS7001

Heavy-Duty Gas Turbine,” GER-3808, GE

Industrial and Power Systems, 1995.

6. Johnston, J.R., “Performance and Reliability

Improvements for Heavy-Duty Gas Turbines,”

GER-3571, GE Industrial & Power Systems,August 1994.

7. GEA-12526 (8/95), 12220.1 (1/94) MS9001E

Gas Turbines: Conversions, Modifications and

Uprates.