ger4217a

GE Power Systems

Uprate Options for theMS6001 Heavy Duty GasTurbineDavid J. TaylorOlivier CrabosGE Energy Services, EuropeGE Power Systems, Schenectady, NY, USA

GER-4217A

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© 2002–2003 General Electric Company. All rights reserved.

Uprate Options for the MS6001 Heavy Duty Gas Turbine

GE Power Systems ■ GER-4217A ■ (12/03) i

Contents

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1MS6001 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1CM&U Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Simple Cycle Performance Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Impact of the Gas Turbine CM&U on Combined-Cycle Performance . . . . . . . . . . . . . . . . . . . . . . 4

Combustion System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Liners (FR1G) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Transition Pieces (FR2B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Cross Fire Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6CL-Extendor (FR1V / FR1W). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Dry Low NOx (FG2B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Steam Injection (SI) for NOx Control (FG1B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Water Injection (FG1A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Compressor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Inlet Guide Vanes (FT4C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Increase in IGV angle (FT4M). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Compressor Blading and Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Stage 17 and EGV Vanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Turbine Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Buckets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Stage 1 Buckets (FS4A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Stage 2 Buckets (FS4B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Stage 3 Buckets (FS3K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Nozzles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Stage 1 Nozzle (FS2J) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Stage 2 Nozzle (FS1P) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Stage 3 Nozzle (FS1R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15


GE Power Systems ■ GER-4217A ■ (12/03) ii

Contents (cont’d)

Turbine Section (cont’d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Shrouds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Stage 1 Shrouds (FS2Y) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152nd and 3rd Stage Shrouds (FS2T and FS2U) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Additional Sealing Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Brush Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17High Pressure Packing Seal (FS2V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Stage 2 Nozzle Interstage Brush Seal (FS2Z) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Abradable Coatings 1st Stage Shroud (FS6A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

PG6571B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Gas Turbine Firing Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Speed Increase (FP4D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19PG6581B — New Unit Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Life Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Installing Individual Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Controls Upgrades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21MS6001 Uprate Experience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

ABSTRACTSince the GE MS6001 heavy-duty gas turbine wasintroduced to the market in 1978, GE has devel-oped many uprates in performance andimprovements in availability and reliability forthis model size.

Based on new material applications and infor-mation accumulated from millions of hours ofoperational experience, GE has been able todevelop a series of new heavy-duty gas turbinemodels. This development work resulted inproducts and improvements for all the earliermodels of heavy-duty gas turbines.

This paper will discuss how this developmentwork has been applied to each of the criticalcomponents for the MS6001 series of turbines.It also discusses where the latest technologyadvances can be applied to enhance the per-formance, extend the life, and provide econom-ic benefits from increased reliability and main-tainability of all earlier MS6001 turbines. Allthese uprates can be applied as a single projector individually phased in over time.

INTRODUCTIONIn today’s deregulated market, owners/opera-tors of all gas turbines need to maximize the per-formance of their assets. In many cases it mayprove economically attractive to modernize anduprate their installed fleet of turbines.

The MS6001 Gas Turbine can achieve uprateimprovements in the following areas:

■ Performance output and heat rate

■ Extension of intervals between inspec-tions

■ Availability and reliability improvements

■ Emission reductions

■ Life extension

If the gas turbine is installed in a combined-cycleplant, the uprates applied to the turbine can bechosen to optimize complete plant perform-ance.

Uprates are made possible as a result of GE’sunderlying design philosophy—to maintaininterchangeability of components for a givenframe size so they can be installed in earlier vin-tage units with little or no modifications.Installing the latest technology hardware andtaking advantage of the highest firing tempera-tures allows owners/operators to remain com-petitive in the marketplace. Virtually every keycomponent in the MS6001 series has gonethrough significant design improvements sincethe first MS6001A was shipped. Buckets, noz-zles, shrouds and combustion components haveundergone multiple evolutions based on newdesigns, manufacturing techniques, materials,and field experience.

MS6001 HistoryOriginally introduced in 1978, the MS6001A gasturbine was scaled from the successful MS7001Egas turbine and had a modest firing tempera-ture of 1850°F. It was upgraded almost imme-diately (in 1981) to the MS6001B machine witha firing temperature of 2020°F.

The MS6001 is a single-shaft, two-bearing gasturbine designed for either 50 or 60 Hz powergeneration. Since its introduction more than900 of these units have been shipped by GE andits manufacturing/business associates. Operat-ing worldwide in both simple-cycle and com-bined-cycle modes, these gas turbines haveproven to be very robust and reliable machines.

Many design improvements have been made tothe MS6001B to bring it to the current AO(Advanced Order) model list definition of thePG6581B. (See Table 1.)


GE Power Systems ■ GER-4217A ■ (12/03) 1

The PG6541B rating was introduced in 1987with several improvements that increased air-flow through the gas turbine and reduced cool-ing and sealing losses. These included:

■ Blunt leading edge 1st stage buckets

■ GTD-450 - high flow IGV (angle 84°)

■ Inboard (Universal) 1st stage nozzle

In 1995 GE announced an AdvancedTechnology Uprate Program for the MS6001 toensure that it remained a competitive optionfor owners/operators. (See Figure 1.) The UprateProgram’s main features were:

■ Improved cooling and sealing features

■ Improved materials

■ Increased speed

■ Improved turbine aerodynamics

■ Increased firing temperature

The Advanced Technology Program broughtthe MS6001 in 1997 up to the PG6571B rating.This rating was only available as a retrofit package.

In 1999, engineering teams in the U.S. andFrance pooled ideas and developed thePG6581B rating. Details of this developmentwork and changes made to the MS6001B arecovered later in this paper.

CM&U ProgramThe Conversions, Modifications and UprateProgram offers a wide range of improvementsfor the installed fleet of GE turbines (all framesizes and models). These CM&U packages areoffered as individual packages or can be appliedin groups. Each package is defined by a four-digit Source Book code. These codes are refer-enced in this paper and in all contract proposaldocuments generated by GE.

Simple Cycle Performance ImprovementsMany of the following CM&U packages help toimprove the overall performance of the simple-cycle gas turbine. Table 2 and Table 3 list the



Table 1. MS6001 performance history

Figure 1. Cross section of MS6001 gas turbine

ExhaustTurbine Ship Firing Temp. Output* Heat Rate* Flow Exhaust Temp.Model Dates °F/°C kW BTU/kWhr 103 lb/hr °F/°C

MS6431A 1978 1850/1010 31,050 11,220 1,077 891/477MS6441A 1979 1850/1010 31,800 11,250 1,112 901/483MS6521B 1981 2020/1104 36,730 11,120 1,117 1017/547PG6531B 1983 2020/1104 37,300 10,870 1,115 1005/541PG6541B 1987 2020/1104 38,140 10,900 1,117 999/537PG6551B 1995 2020/1104 39,120 10,740 1,137 1003/539PG6561B 1997 2020/1104 39,620 10,740 1,145 989/532PG6571B** 1997 2077/1136 40,590 10,600 1,160 1005/541PG6581B 2000 2084/1140 41,460 10,724 1,166 1016/546

* ISO with distillate fuel, STD combustor, no inlet or exhaust losses** Available as retrofit only



Source RequiredGas Turbine Heat Rate Improvements Book for +42°F PG6541 PG6551 PG6561

Table 2. Delta changes in gas turbine output as a result of each CM&U package

Source RequiredGas Turbine Output Improvements Book for +42°F PG6541 PG6551 PG6561

Table 3. Delta changes in gas turbine heat rate as a result of each CM&U package

expected delta changes in performance, foreach of these individual modifications. Thesemodifications can be applied one at a time or alltogether. The gains indicated in these tablesare additive.

Impact of the Gas Turbine CM&U onCombined-Cycle PerformanceWhere the gas turbine is installed in combined-cycle applications, modifying the unit toimprove output and heat rate will change itsexhaust characteristics, resulting in changes tothe steam production and hence combined-cycle performance.

As a rule, any modification that reduces com-pressor losses and/or cooling airflow will resultin more gas turbine output at a reduced heatrate, with more energy available in the exhaust.This leads to an improvement in steam pro-duction and hence gains in combined-cycle out-put and overall efficiency.

Modifications that lead to the turbine sectionbecoming more efficient, again result in more

output and reduce heat rate for the simple-cyclegas turbine, but also result in a reduction inexhaust energy available for steam production.However, the net effect on the overall plant inmost cases is a small increase in output and aslight reduction in overall heat rate.

GE can provide detailed performance calcula-tions for the gas turbine as well as the estimatedoverall plant performance. (See Table 4.)

COMBUSTION SYSTEM

The combustion system—containing fuel noz-zles, liners, transition pieces, X-fire tubes, flamedetectors and spark plugs—consists of 10reverse-flow combustion chambers arrangedconcentrically around the periphery of thecompressor discharge casing. (See Figure 2.)

Liners (FR1G)Combustion liners are slot-cooled, which pro-vides a uniform distribution of cooling airflowon the inside of the liner body. The liner mate-



Table 4. Change to exhaust energy for each CM&U

Approx %Source Required Change in

Gas Turbine Output Improvements Book for +42°F Exhaust Energy

GTD-222 Stage 2 Nozzle FS1P X 0.50Stage 2 Honeycomb Shroud FS2T –0.20Stage 3 Honeycomb Shroud FS2U –0.2086° IGV Setting FT4M 0.705163 RPM Load Gear* FP4E 1.00High Pressure Packing Brush Seal FS2V 0.20Stage 2 Nozzle Interstage Brush Seal FS2Z 0.40Stage 1 Shroud with Cloth Seals FS2Y X 0.60Improved Cooling Stage 1 Nozzle FS2J X –0.30Increase Tfire to 2084°F FT4P X 2.90

GTD-111 DS Perimeter Cooled Stage 1 Bucket FS4A X _Improved Cooling 6 Hole Stage 2 Bucket FS4B X _IN-738 Stage 3 Bucket FS2K X –GTD-222 Stage 3 Nozzle FS1R X –Uprate Transition Piece with Cloth Seals FR2B X –TBC Liners FR1G X _

Total Change in Exhaust Energy 5.60

rial is Hastelloy-X, a nickel-based alloy that wasintroduced for combustion liners in the 1960s.

Liners are now Thermal Barrier Coated (TBC)to insulate the base metal from the combustiongases. (See Figure 3a and Figure 3b.) TBC consistsof two materials applied to the inside surface ofthe liner—a bond coat applied to the surface,and then an insulating oxide applied over thebond coat. Application of TBC reduces basemetal temperature, which leads to a reduction

in component cracking and an overall reduc-tion in thermal stress.

Transition Pieces (FR2B)

Transition Piece (TP) creep can be a significantproblem for many MS6001B units fitted withoriginal Hastelloy-X TPs. TP creep is the defor-mation of the transition piece body near theend frame caused by gradual relaxation ofmaterial due to high temperatures and associat-



Figure 3a. Slot-cooled liner with TBC applied

Top Coat

Bond Coat

Liner Coating Microstructure

Figure 3b. Thermal barrier coating

Figure 2. Cross section through combustion system

ed stresses over time. To overcome this prob-lem Nimonic-263—a precipitation strength-ened, nickel-based alloy with higher strengthcapability than Hastelloy-X—end frames werefitted to the Hastelloy-X body. This becamestandard for production in late 1995. TheNimonic-263 end frame provides a substantialreduction in TP creep.

With the higher firing temperatures associatedwith Advanced Technology Uprates, the body ofthe transition piece as well as the aft frame are

changed to Nimonic-263. In addition to an all-Nimonic construction (both body and aftframe), the design includes a redesigned aftsupport bracket, cloth seals, and Extendor™features, discussed later. (See Figure 4.)

The redesigned aft bracket is mounted to theaft frame instead of the transition piece body.With the previous design, which mounted theaft bracket on the transition piece body, an areaof relatively high stress was created. This stresscould eventually lead to body creep on theHastelloy-X design. The Nimonic-263 materialresists this creep, but the reconfiguration of theaft bracket eliminates the source of the stress

altogether.

Cloth seals are designed to reduce the leakagebetween the transition piece and the first stagenozzle that occurs with the original floating sealdesign. The end of the seal that interfaces withthe first stage nozzle is similar to the originalfloating seal. The end of the seal that is insert-ed into the transition piece aft frame is con-structed by wrapping three layers of metalliccloth around a flexible metal shim. This flexi-bility allows the seal to maintain contact withthe aft frame as unit operation causes relativemotion between the two components.

Cross Fire TubesThe ten combustion chambers are intercon-nected by means of cross fire tubes. Thesetubes enable flame from the fired chamberscontain spark plugs to propagate to the unfiredchambers during startup.

CL-Extendor (FR1V / FR1W)

All gas turbines require periodic combustioninspections. For any given machine, the dutycycle, the type(s) of fuel used, and the amountof water and steam injected are the key factorsin determining the recommended combustioninspection intervals. These factors directly influ-ence the amount of material creep, thermalstress, wear of combustion components andTBC coating erosion.

The CL-Extendor Combustion System canincrease combustion inspection intervals by sig-nificantly reducing combustion componentwear.

The CL-Extendor extended inspection intervalsystem is a unification of the successful"ExtendorTM" offered by GE for many years and"CLE" a product offered by GE’s French manu-facturing associate, which has now become part



Figure 4. Full Nimonic-263 transition piecewith cloth seals

of GE Energy Products Europe (GEEPE). GEhas taken the best parts of each product to pro-duce CL-Extendor. It is available for units withstandard diffusion combustion systems andDLN combustion systems. CL-Extendor extendstime between inspection intervals by:

■ Reducing the relative movementbetween combustion components

■ Reducing forces and vibrations at wearinterfaces

■ Providing for critical clearance controlat wear interfaces

■ Using proven wear-resistant materialcouples developed by GE

CL-Extendor can be applied to combustioncomponents by modifying existing hardware at

an authorized GE Service Center or by havingCL-Extendor features built into (or "pre-applied" to) new combustion components dur-ing the manufacturing process. (See Figures 5a,5b, and 5c.)

The CL-Extendor reduces the effects of wear atthe following key interfaces:

■ Liner stops

■ Fuel nozzle tip to combustion liner fuelnozzle collar

■ Combustion liner hula seal to transi-tion piece forward sleeve

■ Transition piece forward supports andbracket

■ Transition piece aft picture frame seal

There are many ExtendorTM and CLE combus-tion systems in service throughout the world.Individual components for each of these lifeextension combustion systems cannot be inter-changed with each other. Thus, it is importantto provide GE with definitions of all the com-ponents in the combustion system whenrequesting repair or replacement of these com-ponents. This ensures that a correct fit will bemade during installation and that the expectedservice life of the components will be achieved.



Figure 5b. New aft bracket arrangement Figure 5c. Cloth seals for transition pieces

Figure 5a. Cross section through CL-Extendor

Emissions

Emission levels are affected when a gas turbineis uprated. There are three main emissionsabatement options available for the MS6001—aDry Low NOx combustion system, and steam orwater injection. These options are available fornew build units and for retrofitting to theinstalled fleet. (See Figure 6.)

Dry Low NOx (FG2B)

Dry Low NOx (DLN) is a two-stage premixedcombustor designed for operation on naturalgas, but capable of operation on liquid fuel. (SeeFigure 7.) The DLN system achieves low NOxlevels by thoroughly mixing the air and fuel inthe primary stage and delivers a uniform, lean,unburned fuel air mixture to the second stage.The system must operate in four distinct modes

to allow operation from startup to base load atminimum NOx emission levels over the fulloperating range of the gas turbine. Details ofthe DLN combustion system are given in GER3568G (Dry Low NOx Combustion Systems – HeavyDuty Gas Turbines).

Steam Injection (SI) for NOx Control (FG1B)Steam is injected into the compressor dischargeair stream around each of the fuel nozzles toreduce flame temperature—which leads to areduction in NOx emissions. (See Figure 8.)

The quality of steam for injection must complywith GEK101944 (Requirements for Water/ SteamPurity in Gas Turbines); typical supply conditions ofthe steam would be 325 psig with a minimum of50°F superheat. Retrofitting SI will increase thegas turbine output and reduce heat rate. (SeeFigure 9.) The quantity of steam required will



Figure 7. Cross section of DLN-1 combustionsystem

Figure 6. NOx emission levels at 15% O2 (ppmvd)

Single Shaft Units Dry Water/Steam Inj. Dry Low Nox

Firing Temp. Gas Dist. Gas Dist. Gas Dist.*Model °F/°C — — (FG1A/FG1F) (FG1C/FG1F) (FG2B) (FG2B)

MS6001B 2077/1136 148 267 42 65 9 42

*With water injection for distillate oil

Figure 8. Combustion cover with steaminjection nozzles



depend on the desired NOx level required, thefuel used and the ambient conditions.

Water Injection (FG1A)Water injection (WI) works in the same way assteam injection—reducing the flame tempera-ture, which results in low NOx emissions. Theinitial design injected water into the fuel nozzleswirler. This led to water impingement on thecombustion liner cap and body, which resultedin thermal shock and increased combustionmaintenance. The latest design is a breech-loaded fuel nozzle—where water is injected

down the center of the fuel nozzle—whichreduces the risk of water impingement. (SeeFigure 10.) Retrofitting WI will increase the out-put and the heat rate of the gas turbine. (SeeFigure 11.)

COMPRESSORThe compressor is a seventeen-stage, axial flowtype. The compressor rotor is made up of anassembly of compressor wheels and stub shaftsconnected by through bolts. The 1st stagewheel also includes the rotor stub shaft for the#1 bearing, the thrust bearing and the accesso-ry gear coupling.

Inlet Guide Vanes (FT4C)IGVs are used to control air inlet flow to thecompressor during start-up and part load oper-ation. In 1987 low camber, high-flow IGVs wereintroduced to all GE frame size gas turbines.

The new IGVs have higher reliability due to theuse of a special stainless steel alloy—GTD-450, aprecipitation-hardened, martensitic stainless

Figure 11. Effects of water injection onoutput and heat rate

11,900

11,850

11,800

11,750

11,700

11,650

11,600

11,550

11,500

11,450

11,400

41,000

40,500

40,000

39,500

39,000

38,500

38,000

37,500

37,000158 120 90 60 42

0 0.35 0.76 1.42 2.13

NOx/ppmvd @ 15% O2

WI/kg/sec

Out

put/k

W

Hea

t rat

e/kJ

/kW

hr

Output

Heat rate

Figure 10. Breech-loaded fuel nozzle

Figure 9. Effects of steam injection on outputand heat rate

43,000

42,000

41,000

40,000

39,000

38,000

37,000

36,000

11,600

11,500

11,400

11,300

11,200

11,100

11,000

10,900

10,800158 120 90 60 25

0 0.53 1.08 1.88 3.67

NOx/ppmvd @ 15% O2

SI Flow/kg/sec

Out

put/k

W

Hea

t rat

e/kJ

/kW

hr

Output

Heat rate



steel—instead of the original AISI 403SS.(See Figure 12.) These improvements include:

■ Increased tensile strength

■ High cycle fatigue resistance

■ Corrosion fatigue strength

■ Superior corrosion resistance (due tohigher concentrations of chromiumand molybdenum)

The low camber design increases the airflowacross the IGVs giving an improvement in gasturbine output and reduction in heat rate.

Increase in IGV angle (FT4M)

In 1995 the IGV angle was increased from 84 to86 degrees, allowing slightly higher airflowthrough the gas turbine and giving increasedgas turbine output but with a slight heat ratepenalty. Increasing IGV angle will require theapplication of an inlet plenum scroll on singlebase Frame 6 gas turbines. (There is anincrease in bushing wear associated with theincrease in IGV angle and hence regular inspec-tion is required. (Refer to TIL 1068-2R1.)

Compressor Blading and CoatingsOriginally Rows 1–8 were 403+Cb with a NiCdcoating and Rows 9–17 were 403+Cb withoutcoating. Since 1994, Rows 1–2 are GTD-450,Rows 3–7 are 403 with a GECC1 coating andRows 8–17 are 403+Cb. GECC1 (a GE propri-etary corrosion resistant coating) is an alumini-um slurry coating, which has a protectiveceramic top layer that provides improve corro-sion resistance.

This new GECC1 coating can be applied at a GEservice shop to existing compressor blading forall stages of the compressor. However, GECC1cannot be applied to blades made from GTD-450 stainless steel alloy.

Stage 17 and EGV VanesA limited number of 6B compressor Stator 17and EGV1 vanes have experienced high cyclefatigue or cracking. (Refer to TIL 1170-2R1.)

Metallurgical analysis of distressed and crackedvanes concluded high cycle fatigue as the causeof distress. Aerodynamic excitation of stage 17and EGV stator vanes due to flow separationresults when the aft end of the compressor isheavily loaded. Aft end compressor loadingincreases with higher pressure ratios.

A number of operational modes have been iden-tified that further increase the loading on thevanes, which may lead to the distress experienced:

■ Operation during periods of cold ambi-ent temperatures

■ Operation at reduced load (with closedIGV)

■ Operation with water/steam injection forNOx reduction or power augmentation

■ Low BTU gas fuel

■ Flow path disturbances from inner barrelcounter bores

Figure 12. High-flow IGV design improvementswith GTD-450 material

— Improved Airfoil Design for Higher Flow— Variable Airfoil Thickness to Maintain

Reliability— GTD-450 for Higher Tensile Strength and

Superior Corrosion Resistance— Increased Output (+1.5%)— Decreased Heat Rate (–0.3%)

VariableThicknessAirfoil

HigherPerformanceAirfoil Design

1.8

1.6

1.4

1.2

1.0

.8

.6

.4

.2

00 10 20 30 40 50 60 70

GTD 450

AISI 403SS

Mean Stress (KSI)

Alte

rnat

ing

Sres

ss A

mpl

itude

(Rat

io to

AIS

I 403

)



Counter bores, located at the inner barrel split-line, have shown to be significant contributorsto the high aerodynamic loading.

To minimize the probability of a Stator 17 orEGV vane distress, the following configurationmodifications may need to be installed with anyof the CM&U uprates detailed in this GER:

■ New inner barrel counter bore plugs.

■ Control system modification to changeturbine operating curves. This willlimit gas turbine minimum IGV angleoperation under certain low ambientand extreme operating conditions.

Analysis of the unit configuration and operat-ing parameters will allow GE to determine if theabove modifications are required.

GE is designing new-shrouded Stator 17 andEGV vanes to remove the risk of blade failure.These will be available in mid-2003.

TURBINE SECTION The MS6001 Gas Turbine has a three-stage tur-bine; the first two stages are air-cooled with the3rd stage uncooled. (See Figure 13.) It is anassembly of three turbine wheels, wheel spacersand the aft stub shaft, all connected with troughbolts.

Buckets

Stage 1 Buckets (FS4A)

The original stage 1 buckets (S1B) were madeof IN738, a precipitation-hardened, nickel-based super alloy with a LDC coating and 13cooling holes. IN738 was the standard materialfor S1B on all frame sizes in the early 1980s.

The S1B was upgraded in 1987 with the intro-duction of Equiaxed GTD-111 material, GT-29coating, 11 cooling holes, and a Blunt LeadingEdge (BLE) airfoil section. Equiaxed GTD-111was introduced because it had 20°C improvedrupture strength and was more resistant to lowcycle fatigue than IN738.

For a period of three years from late 1989, GEexperienced several failures of first stage buck-ets. Many TILs were issued to customers advis-ing them of the potential for failure togetherwith information advising on the restricted serv-ice life of each group of buckets. GE identifiedall Frame 6 gas turbines shipped by both GEand its MA/BAs and which S1Bs were fitted toeach gas turbine. GE embarked on an exerciseto have all suspect S1Bs withdrawn from service.

The failures were caused by a reduction increep rupture strength exacerbated by acceler-ated oxidation attack and high bucket metaltemperatures. This oxidation resulted fromdeterioration of the external coating and alsoby internal oxidation attack of the uncoatedcooling holes. This oxidation contributed tolocal over-temperature by partial plugging ofcooling holes and subsequent reduction increep life.

Several design changes to the buckets weremade to eliminate risk of failure. An additionalcooling hole was added to reduce bulk metaltemperature (12 cooling holes) and GT-29INPLUS coating was applied. This coating is avacuum plasma spray, with an Aluminide coat-Figure 13. Cross section through turbine shell

ing on the bucket exterior and on the internalcooling-hole passages. This coating providedhot corrosion protection and high temperatureoxidation resistance.

The directionally solidified (DS) GTD-111buckets were introduced in the mid-1990s. DSGTD-111 possesses an oriented grain structurethat runs parallel to its major axis and containsno transverse grain boundaries. The elimina-tion of the transverse grain boundaries resultsin additional creep and rupture strength.

Current Frame 6 buckets are DS GTD-111 withGT-33 INPLUS coating and 16 cooling holes.The perimeter-cooled stage 1 bucket incorpo-rates several design improvements to allow foroperation at the higher firing temperatureassociated with the 6B Advanced TechnologyUprate. (See Figure 14.)

The new bucket-cooling scheme includes aseries of 16 radial cooling holes located aroundthe "perimeter" of the bucket. Thirteen of thecooling holes include "turbulators" on theinternal surfaces of the cooling holes (from 0 to80% of the bucket span) to increase the effi-ciency of heat transfer from the bucket metal tothe cooling air. The turbulators are STEMdrilled (Shaped Tube ElectrochemicalMachining).

The buckets also incorporate a cored or hollowshank that more effectively provides air to the16 cooling holes. This feature allows for moreconsistent control of the quantity of cooling airand reduces the risk of cooling holes becomingplugged during operation.

In addition to the improvements in cooling, thenew bucket has a new airfoil profile. This pro-file has been designed with heat transfer char-acteristics appropriate for operation at thehigher firing temperature of the 6B AdvancedTechnology Uprate. This included thinning ofthe leading edge and rotating the airfoil hubsections. With all of these improvements, thebulk metal temperature of the new first stagebuckets operating at the higher firing tempera-ture will be lower than the bulk metal tempera-ture of the current buckets operating at thelower firing temperature.

GT-33 INPLUS is now the standard S1B coatingfor B and E class turbines. Like GT-29 INPLUS,it is also a vacuum plasma spray coating, butoffers increased resistance to through cracking.

GT-29 INPLUS coating is still available for unitsthat burn corrosive fuels.

Stage 2 Buckets (FS4B)

The stage 2 bucket (S2B) has undergone sever-al design changes since first introduction; it wasoriginally made from IN738 with 4 radialsmooth cooling holes and no coating.

In 1997 with the announcement of theAdvanced Technology Uprate for the 6B, a new7-cooling -hole design was introduced. Five outof seven holes were turbulated from 40% to70% of their span to improve cooling of thebucket—leading to reduced bulk metal temper-atures, even at the higher firing temperature.

At the same time, three failures of the 4-holeS2B were experienced. These failures were due



6B Advanced Technology Stage 1 Bucket

BLUNT LEADING EDGE

Tf BaseMaterial DS GTD-111Coating GT291N+Cooling 12 Smooth Holes

MeanlineShank Radial ECM

Base +35FDS GTD-111GT331N+3 Smooth/13 Turb HolesPerimeterHollow Core

PERIMETER COOLED

Figure 14. Stage 1 bucket GTD-111perimeter-cooled

to airfoil creep. TIL 1203-1R1 details failuremode and advises inspection requirements ofthese buckets. All 4-hole buckets are to bereplaced at or before 48,000 hours of opera-tion.

The current S2B design incorporates severaldesign improvements to allow for operation atthe higher firing temperature associated withthe 6B Advanced Technology Uprate and thePG6581. The material for the new stage 2 buck-ets continues to be IN738, however the bucketnow has six radial cooling holes—four of whichare turbulated from 40% to 70% of their span.(See Figure 15.) New airfoil geometry has beenutilized which allows improved cooling to thetrailing edge of the bucket.

Both the 7-hole and 6-hole S2B include "cutterteeth" on the bucket tip shroud rails. These aredesigned to cut a slot in the honeycomb sealmaterial on the stage 2 shroud block with nometal transfer to the bucket.

Cutter teeth have been included on all stage 2Frame 6 buckets manufactured since late 1995.

Stage 3 Buckets (FS3K)

Higher firing temperature associated with theFrame 6B uprate has led to the introduction ofIN738 as the material for the stage 3 bucket

(S3B), instead of the original U500. IN738offers superior hot corrosion resistance thanU500. Buckets now include cutter teeth similarto S2B, so that honeycomb stage 3 shrouds canbe installed.

Nozzles

Stage 1 Nozzle (FS2J)

The original material used for the first stagenozzle and still used today is FSX-414. It is acobalt-based super alloy, which has excellentoxidation, hot corrosion and thermal fatigueresistance. It requires inspection during thehot gas path inspection (HGPI @ 24,000 hrs),and is weld-repairable, which allows the nozzleto be refurbished and returned to service dur-ing future HGPIs.

There have been several generations of thestage 1 nozzle (S1N). A Universal S1N wasinstalled in the MS6001 in 1987, which allowedoperation on residual fuels (ash bearing fuels)as well as fuel gas and distillate oil.

The Universal S1N has now been modified. It iscapable of replacing nozzles based on the olderuniversal nozzle design as well as pre-universalnozzles operating on either conventional orheavy fuel. First time application of the univer-sal nozzle will require a new nozzle supportring. The key modifications include thesechanges:

■ Nozzle sidewall cooling

■ Airfoil trailing edge film cooling holes

■ New impingement hole pattern on thecore plug

■ New pressure side cooling hole pattern,

■ Improved inner segment spline seals

■ Improved sidewall seal

■ Addition of a nozzle inner sidewallimproved hinge rail



• Nickel base Alloy material• Enhanced cooling of airfoil• Contoured tip shroud for creep life improvement

Figure 15. Stage 2 bucket — improved cooling(6 cooling holes)

The major design change incorporated into theimproved cooling, stage 1 nozzle is the additionof a more efficient film-cooling pattern. Thisnew design incorporates a sidewall cooling holepattern that has been relocated to promote bet-ter coverage of the most commonly distressedarea on the nozzle sidewall, as determined bycomputer modelling and operational histories.The improved coverage pattern is achieved oncurrent production nozzles by replacing thepressure side film holes with film cooling slots,as shown in Figure 16.

The new slots are spaced more closely togetherand are combined with new cooling holes to theinter-vane space on the nozzle outer sidewall.The resulting improvement in exit conditionssignificantly increases the cooling efficiency ofthe airflow to the sidewall areas—withoutincreasing the overall airflow requirement.

The hinge design originates from proven air-craft engine technology applied to today'sheavy-duty gas turbines. The improved seal iscreated on the support lug with a new straightimproved seal ridge. This results in animproved seal at the S1N/support ring inter-face. This seal eliminates the potential leakpath due to warping and distortion sometimesassociated with the older curved support lug dis-engaging during operation. The straightimproved seal requires a redesigned shortertangential slot on the inner sidewall support

lug. This new seal—coupled with the offset ofthe support lug—combines to create a 'hinging'action downstream from the retaining ringalong the radial plane of the nozzle.

Improved inner segment sidewall spline sealsreduce leakage between nozzle segments.

Stage 2 Nozzle (FS1P)

The second stage nozzle (S2N) design, original-ly fabricated from FSX-414 material, has beenreplaced by a newer nozzle design that is fabri-cated from creep resistant GTD-222 material.This newer, nickel-based alloy significantlyreduces the downstream deflection characteris-tic of the older material. (See Figure 17.) Theoverall dimensions of the GTD-222 nozzle



GTD-222 vs. FSX-414Nozzle Creep Deflection Comparison

Time - KHR

1.2

1.0

0.8

0.6

0.4

0.2

010 20 30 5040 60

GTD-222

FSX-414

Figure 17. Stage 2 nozzle creep deflection comparison

ShapedPressure SideCooling Holes

Spline SealImprovement

Increased TrailingEdge Hole Size

Improved HingeAdditional CoolingCore Plug Modification

Uprate

Current

Figure 16. Stage 1 nozzle showing coolingand sealing modifications

remain unchanged from the previous designand are applicable as either an uprate or areplacement part for units with the oldernozzle.

FSX-414 nozzles are subject to downstreamcreep deflection due to:

■ The cantilevered design of the nozzle

■ Exposure to high temperatures

■ Downstream loading caused by axialpressure differentials across the nozzle

■ Gas reaction forces.

Analysis over time has shown that units experi-encing downstream creep deflection requireadditional monitoring leading to increasedmaintenance and repair costs.

The new GTD-222 second stage nozzle is coatedwith an aluminide coating to provide improvedhigh temperature oxidation resistance. Othermodifications include changes to the secondstage nozzle's internal core plug. Core plugmodifications allow more efficient distributionof cooling air and reduced nozzle-coolingrequirements. (See Figure 18.)

New tuning pins associated with this uprate andmodifications to the first stage shroud blocksthat include smaller cooling air orifices—incombination with core plug modifications—fur-ther reduce cooling air requirements and resultin gas turbine performance improvements.

There are two configurations of S2Ndiaphragms (referred to as "pressurized" and"non pressurized" designs). Some customershave experienced high 1AO wheelspace tem-perature problems with the pressurized design,as referred to in TIL 1243-2. The pressurizeddesign nozzle was shipped between 1997 and2002. All future S2N diaphragms will be thenon-pressurized design.

Stage 3 Nozzle (FS1R)

The third stage nozzle (S3N) was redesigned toeliminate the downstream nozzle deflection.Similar to the S2N, GTD-222 material hasreplaced the FSX-414 due to the superior creepresistance property. The chord length on theS3N was increased to improve the airfoil’s sec-tion modulus so that the bending stress levelcould be reduced.

Shrouds

Stage 1 Shrouds (FS2Y)

There are several design improvements availablefor the stage 1 shrouds (S1S). (See Figure 19.)The original material has been changed from310SS to HR-120. The new material has bothhigher inherent material strength and morefavourable time at temperature characteristics.

New spline seals replace the original pumpkinteeth design. This dramatically reduces theleakage of compressor discharge air into thehot gas path, resulting in improved turbine per-formance.

A new flexible "w" seal is also fitted between theS1S and S1N retaining ring. After a period of



Figure 18. Stage 2 nozzle cooling airflow

service or after overhaul/repair, the S1N may beslightly distorted. The flexible "W" seal accom-modates for this distortion and again preventsleakage of CD air into the HGP.

2nd and 3rd Stage Shrouds (FS2T and FS2U)

Honeycomb seals are designed to reduce leak-age associated with hot gases that flow aroundthe tips of the buckets—thereby improvingboth heat rate and output. In the past, clear-

ances between the bucket shroud tips and thecasing shrouds were set based upon expectedtransients that tend to close the clearances. Theclearance had to be large enough to allow thesetransients to occur without permitting contactbetween the bucket tip and the shroud. As aresult, the steady state running clearance is typ-ically larger than it needs to be from an effi-ciency standpoint. To provide relatively tightclearances during steady state operation, hon-eycomb seals will allow contact between thebucket tip and the casing shrouds.

Strips of honeycomb material made of a high-temperature, oxidation-resistant alloy arebrazed between the teeth on the casingshrouds. "Cutter teeth" on the leading edge ofthe shrouded 2nd and 3rd stage bucket tip railswill "cut" the honeycomb material away whencontact occurs during transients. This pro-duces steady-state running clearances that are—on an absolute basis—no larger than the differ-ence between the steady state and the transientclearances. The effective clearance is actuallytighter than the absolute clearance since theresulting groove in the honeycomb provides atighter labyrinth seal than could be obtainedwith solid materials. Honeycomb shrouds alsoreduce performance degradation by maintain-ing tighter clearances throughout the life of theshroud. (See Figure 20.)



Figure 20. Stage 2 shroud with honeycomb sealing

"Bus Bar"Seal

Cloth Spline Seals

PumpkinTeeth

W-Seal

SIDE VIEW

BOTTOM VIEWCurrent Shroud Uprate Shroud

BOTTOM VIEW

SIDE VIEW

Figure 19. Improved stage 1 shrouds

Additional Sealing ModificationsTo improve overall performance of the gas tur-bine in both output and heat rate, GE has devel-oped a series of sealing technologies availablefor retrofit in all the heavy-duty gas turbineframe sizes. Some of these seals are installed onthe current production models.

Brush Seals

Brush seals are available in two locations on theMS6001. Each brush seal option uses brushseals that have been specially designed for theapplication to take into account the location’soperating conditions. Brush seals are com-prised of a pack of fine metallic wires (or bris-tles) held in a frame. Simple designs have beenused for basic sealing applications for a numberof years. Recently, advanced designs havebecome prevalent in aircraft engine and indus-trial gas turbines. In these applications, brushseals are typically used as replacements or addi-tions to labyrinth seals that are not maintainingtheir desired sealing levels, especially after anumber of transient radial excursions.

The bristles are simply displaced during theexcursion and, then, return to their positiononce the transient condition has passed.Labyrinth seals would rub under similar excur-sions introducing higher leakages beneath the

labyrinth seal. The brush seals also maintain apressure gradient across the bristle path whileminimizing leakage through the bristle pack. Abrush seal can easily accommodate misalign-ment normally not tolerated by labyrinthdesigns.

High Pressure Packing Seal (FS2V)

The HPP is designed to regulate the flow ofcompressor discharge air between the station-ary inner barrel and the compressor rotor aftstub shaft into the turbine first-forward wheel-space. The clearance between the seals on thecompressor discharge casing/inner barrel andthe compressor rotor aft stub shaft controls theflow through this area. Some of this bypass air-flow is required for cooling the turbine first-for-ward wheelspace; however, the current flow isexcessive. Controlling this bypass airflow to theminimum levels required for cooling willincrease the amount of air available to performwork in the cycle.

The original design was for a labyrinth seal,which can experience severe rubs during tran-sient operating conditions. Replacing thislabyrinth seal with a rub-tolerant brush seal con-trols this bypass airflow, leading to improved gasturbine performance (output and heat rate).(See Figure 21.) Long-term performance degra-



Figure 21. High pressure packing brush seal

dation is also reduced as the brush seal main-tains HPP seal clearances after manystarts/stops and operating hours.

Stage 2 Nozzle Interstage Brush Seal (FS2Z)

The 2nd stage nozzle/diaphragm assembly con-tains a radial high-low labyrinth seal that reducesflow leakage across the diaphragm and the tur-bine rotor from stage 1 aft into the stage 2 for-ward wheelspace. The interstage brush seal fur-ther reduces this leakage and hence reduces thecooling air (purge air) flow requirements intothe stage 1 aft wheelspace. (See Figure 22.)

Reduction of cooling airflow (reduction in loss-es) allows more air to flow through the com-bustion system, therefore improving overall gasturbine performance.

Cooling airflow to the 2nd stage forward wheel-space will be reduced, but this flow is currentlylarger than required.

Abradable Coatings 1st Stage Shroud (FS6A)

The stage 1 shroud blocks can be coated with anabradable coating on the inner circumference.The abradable coating is designed to wear awayin the event of a bucket tip rub. It allows tighterclearances between the bucket and shroud lead-ing to performance improvements.

Clearances between static and rotating compo-nents allow the combustion gas to leak past theairfoil section of the buckets. These clearancesare influenced by transient thermal growth,rotor alignment, rotor sag, and turbine shellout-of-roundness. The abradable coating com-pensates for these factors to minimize therequired clearance. This reduces bucket tipleakage, which leads to an improvement in tur-bine section efficiency.

Prior to application of the abradable coating,the shroud block is grit-blasted to remove the6-mil of hard coating typically applied by theshroud block manufacturer. The abradablecoating is a 40-mil layer of GT-50. The chemicalcomposition of this coating is CoNiCrAlY withpolyester and is suitable for use with a non-tipped blade (i.e., a blade that does not requireany type of hard/abrasive coating).

This material has proven to have the requiredproperties for both abradability and service lifeat the "E" class firing temperature.

PG6571BThis model was only available as a retrofit pack-age. All MS6001 gas turbines shipped before1999 can be uprated to this rating. It includesmany of the sealing modifications discussed



Figure 22. Stage 2 nozzle interstage brush seal

above, a speed increase and new HGP compo-nents, which allows the unit to operate at2077°F firing temperature.

Gas Turbine Firing Temperature With the introduction of the Type B MS6001 in1981, the firing temperature reference for theMS6001 was set at 2020°F. After performancedata collection and analysis by GE performanceengineers of a wide selection of PG6541 gasturbines and remodelling of GE’s "Cycledeck"program, it was determined that the true firingtemperature reference should be 2042°F. In1996 the MS6001B firing temperature refer-ence was changed from 2020°F to 2042°F, toreflect these findings.

When GE offers the +35°F firing temperatureuprate, this refers to +35°F above the true firingtemperature reference of 2042°F—which pro-vides Advanced Technology Uprate gas turbineswith a firing temperature of 2077°F. There hasbeen some confusion in sales literature whichquotes +35°F above the original reference tem-perature of 2020°F for an uprate to 2055°F.This should be 2077°F as advised above.

Current production models (PG6581) have aslightly higher firing temperature reference of2084°F. This higher firing temperature is now

available for all earlier models providing thatthe components listed in Table 5 are installed.An additional 0.2% output increase is achievedover the 2077°F firing temperature.

Speed Increase (FP4D/E)

GE introduced a speed increase for the MS6001in 1995, to increase the mass airflow throughthe turbine and hence increase output. Thisincreased the speed from 5104 rpm to 5133rpm. More recently a further speed increase to5163 rpm was introduced. All earlier Frame 6gas turbines are suitable for this increase inspeed, giving 0.5% increased output (5133 to5163), providing that the new perimeter-cooledS1Bs and the 6- or 7-hole S2Bs are fitted. Toachieve this uprate the complete load gearboxis normally replaced.

PG6581B - New Unit ConfigurationIn 1997, GE’s French manufacturing associate,which is now part of GEEPE, decided to upratetheir current production MS6001 (thePG6551B model with 5114 rpm turbine speed).

Output and efficiency improvements wereachieved by:

■ Increasing firing temperature to2084°F/1140°C



Table 5. All components required to operate at a higher firing temperature

Components Required for Increase Sourcein Firing Temperature to 2084°F (FT4P) Book

■ Reducing leakages in the hot gas path

■ Reducing inlet and exhaust pressurelosses

These improvements were introduced in threesteps to achieve the PG6BEV2 model rating. SeeTable 6 for each of the improved features.

After the acquisition of GE’s French manufac-turing associate in June 1999, engineeringteams in the U.S. and France pooled ideas anddeveloped the current PG6581B rating.

The final configuration of the PG6581B is aharmonization of the PG6BEV2 developed inFrance and the PG6571B (developed as part ofGE’s CM&U uprate program in the U.S.). SeeFigure 23 and Figure 24 for the final PG6581Bconfiguration.

The major differences to the PG6571B model are

■ 13th compressor stage extraction forstage 2 nozzle cooling. (See Figure 25.)

■ High performance exhaust diffuser.(See Figure 26.)

Redesigning the MS6001 achieved an increase of6% in output and a decrease of 0.6% in heatrate—resulting in improved competitiveness forthe MS6001 in today’s deregulated market. SeeFigure 27 for a performance comparison betweenthe PG6561B and the PG6581B models.

First shipment of the new unit PG6581B was inSeptember 2000. See Table 7 for the currentinstalled fleet of 61BEV2 and 6581B units.

LIFE EXTENSION

Maintenance The maintenance schedule for the MS6001 isbased on publication GER-3620 (Heavy-DutyGas Turbine Operating and MaintenanceConsiderations). This advises on the types ofmaintenance required, the time between main-



OPTION 6561B 6BEV 6BEV2

Speed IncreaseIncrease in speed to 5163 rpm X X X

Pressure losses reductionVertical inlet X X XHigh performances exhaust diffuser X X

Leakages reductionOuter sealing strips on S1 nozzle XChordal hinge on S1 nozzle XBraided seal on stage 1 shroud XHPP Seal improvement (brush seals) X

Increase in firing temperatureIncrease in firing temperature (1140°C) XS1 Bucket – GTD-111 DS, turbulators XS2 Bucket – GTD-111, turbulators X XS1 Nozzle – improved cooling XS2 Nozzle – new engine X13th stage bleed and improved

shroud cooling X XCombustion

Dry low NOx using natural gas XDry low NOx using distillate XCombustion Life Extendor™

Table 6. AGT PG656B/6BEV/6BEV2 improved features



Figure 23. PG6581B configuration (PG6BEv2 and PG6571B harmonization)

6581 Upgraded Components

VerticalInlet

Firing Temp.Increase

Stage 1Shroud

HPPS withBrush Seal

13th Stage Extraction

Combustion System

Stage 1 & 2Buckets

ExhaustSystem

Stage 1Nozzle

ImprovedSealing

Figure 24. PG6581B upgraded components

Stage 13 Extraction• Compressor Discharge Casing — Bleed Belt Incorporated into Casing

• Extraction System Pipework

• Turbine Casing – Bosses for Pipe Flange Attachment

• Second Stage Nozzle Cooling with Radiation Shield

Figure 25. 13th compressor stage extraction for stage 2 nozzle cooling

tenance and all the factors that affect mainte-nance scheduling.

Table 8 shows the maintenance intervals forFrame 6 for the different firing temperaturesand combustion systems. These intervals arebased on a reference condition of gas fuel, NoSI or WI, and base load operation.

Installing Individual PartsCustomers may order components as individualparts—and not the complete uprate—to suittheir own turbine component service life, andscheduled overhaul requirements. All uprateparts are interchangeable with existing compo-

nents and can be integrated into the gas tur-bines current configuration.

As new technology parts are installed, comple-tion of the uprate can be scheduled and con-trols modified to achieve the required perform-ance and/or maintenance objectives.

Controls UpgradesFrame 6 gas turbines have been shipped withSPEEDTRONICTM Mark II, Mark IV and MarkV control systems. All these systems can beupgraded to the latest Mark V or Mark VI con-trol system.

Control system upgrades offer much improvedgas turbine reliability with:

■ Digital control

■ Triple Modular Redundancy (TMR)

■ Protection against loss of availability ofspares

Full details of Mark V and Mark VI control sys-tems can be found in GER 3658D (SPEEDTRON-IC™ Mark V Gas Turbine Control System) and GER4193 (SPEEDTRONIC™ Mark VI Turbine ControlSystem).

MS6001 Uprate Experience

GE has successfully uprated seven MS6001s tothe PG6571B model rating to date. TheMS6001B uprate experience is listed in Table 9.



Exhaust Diffuser

• Improved performances in reducing exhaust pressure losses• Minimized design change: — same shaft line level and length — same generator interface — same exhaust casing and struts• Two configurations available — lateral and vertical exhaust

Figure 26. High performance exhaustdiffuser

Figure 27. Performance data comparison between PG6561B and PG6581B model

PG6561B* PG6581B**

Output 39,640 kW 42,100 kWHeat Rate (LHV) 11295 kJ/kWh 11227 kJ/kWhPressure Ratio 12.03 : 1 12.2 : 1Exhaust Flow 525 t/h 530 t/hExhaust Temperature 531°C 548°C

* ISO conditions, Methane, STD combustor, 4/2.5 inlet/exhaust pressure drop** ISO conditions, Methane, STD combustor, 2.55/2.52 inlet/exhaust pressure drop

Many other customers have chosen to installcurrent MS6001 new technology components assingle spare part replacements, when existingcomponents reach the end of their service life.This is done with a view to increasing firing tem-perature when all components in Table 5 havebeen installed.

The first MS6001B uprate to 2077°F/1136°Cwas successfully completed in spring 1997 at theMidset, Cogen site. Because this was the firstuprate of its kind, extensive testing was com-pleted to monitor compressor and turbine per-formances. Successful testing of five unitsoccurred between 1997–1998, resulting in aver-age performance improvements better thanexpected.

Uprates on differently rated MS6001s also have

been completed, including several on the morerecent PG6551B and PG6561B models.

SUMMARYGE has an uprate package available for allFrame 6 turbines in the field. These upratescan be done during scheduled outages on apiece-meal basis or all at the same time, depend-ing on when existing hardware is life expire.

GE would be happy to provide detailed techni-cal proposal for owners of GE Frame 6 gas tur-bines and establish performance improvementsfor those specific turbines. If the gas turbine isinstalled in Combined Cycle (CC), Cogen, orCombined Heat and Power (CHP), GE can alsoadvise on the impact to the steam cycle, fromperforming these uprates.



Table 7. PG6BEV2 and PG6581B Fleet

Country Ex Works Model Comments

France 5/28/99 6BEV2 DLN 1 (gas only)Spain 10/14/99 6BEV2 STD (dual fuel)Spain 11/18/99 6BEV2 STD (dual fuel)France 1/19/00 6BEV2 DLN 1 (gas only)France 1/31/00 6BEV2 DLN 1 (gas only)Spain 5/29/00 6BEV2 STD (dual fuel)Wisconsin/USA 8/29/00 6BEV2 DLN 1 (dual fuel)Wisconsin/USA 9/14/00 6BEV2 DLN 1 (dual fuel)Philadelphia/USA 11/30/00 6581B DLN 1 (gas only)Philadelphia/USA 11/30/00 6581B DLN 1 (gas only)Philadelphia/USA 11/30/00 6581B DLN 1 (gas only)Philadelphia/USA 10/11/00 6581B DLN 1 (gas only)Philadelphia/USA 10/11/00 6581B DLN 1 (gas only)Philadelphia/USA 10/20/00 6581B DLN 1 (gas only)Philadelphia/USA 6/13/01 6581B DLN 1 (gas only)Philadelphia/USA 6/26/01 6581B DLN 1 (gas only)Philadelphia/USA 7/16/01 6581B DLN 1 (gas only)Philadelphia/USA 7/25/01 6581B DLN 1 (gas only)Philadelphia/USA 8/21/01 6581B DLN 1 (gas only)Philadelphia/USA 9/12/01 6581B DLN 1 (gas only)

Over 70 PG6581B units sold to date

Country Description CM&U DateUSA PG6001 +35 Degree Uprate – MS6001B 1997USA PG6001 +35 Degree Uprate – MS6001B 1997USA PG6001 +35 Degree Uprate – MS6001B 1997USA PG6001 +35 Degree Uprate – MS6001B 2001USA PG6001 +35 Degree Uprate – MS6001B 2001USA PG6001 +35 Degree Uprate – MS6001B 2002USA PG6001 +35 Degree Uprate – MS6001B 2002USA PG6001 +35 Degree Uprate – MS6001B 2003AIM PG6001 +35 Degree Uprate – MS6001B 2003UK PG6001 +35 Degree Uprate – MS6001B 2003UK PG6001 +35 Degree Uprate – MS6001B 2003UK PG6001 +35 Degree Uprate – MS6001B 2003

Mexico PG6001 +35 Degree Uprate – MS6001B 2003Spain PG6001 +35 Degree Uprate – MS6001B 2003/2004



Summary of Recommended Combustion Inspection Intervals With and Without CL Extendor

Frame Size for 6541/51/61B (2042°F) 6571/81B (2072–2084°F)Combustion Type Standard DLN Standard DLN

Non CL-ExtendorFired Starts 800 Service Factor 400 Service Factor 800 Service Factor 400 Service FactorFactored Hours with

standard T/P 12,000 ref 12,000 ref NA NAGas, no inj. (dry) 12,000 1.0 12,000 1.0 NA NAGAS, Ext. L-L (dry) NA NA 4,000 3.0 NA NAGas, w/ stm inj. 12,000 1.0 NA NA NA NAGas, w/stm aug. 12,000 1.0 3,000 4.0 NA NAGas, w/water inj. 6,000 2.0 2,000 6.0 NA NADist, no inj. (dry) 8,000 1.5 2,667 4.5 NA NADist, w/stm inj. 8,000 1.5 NA NA NA NADist, w/stm aug. 8,000 1.5 NA NA NA NADist, w/water inj. 4,000 3.0 1,333 9.0 NA NA

CL-ExtendorFired Starts 800 Service Factor 400 Service Factor 800 Service Factor 400 Service FactorFactored Hours with

standard T/P* 24,000 ref 24,000 ref NA NAFactored Hours* with

advanced T/P (Gas/Dry) NA NA 24,000 ref 24,000 refGas, no inj. (dry) 24,000 1.0 24,000 1.0 24,000 1.0 24,000 1.0GAS, Ext. L-L (dry) NA NA 8,000 3.0 NA NA 8,000 3.0Gas, w/stm inj. 24,000 1.0 NA NA 24,000 1.0 NA NAGas, w/stm aug. 24,000 1.0 6,000 4.0 24,000 1.0 6,000 4.0Gas, w/water inj. 12,000 2.0 4,000 6.0 12,000 2.0 4,000 6.0Dist, no inj. (dry) 16,000 1.5 5,333 4.5 16,000 1.5 5,333 4.5Dist, w/stm inj. 16,000 1.5 NA NA 16,000 1.5 NA NADist, w/stm aug. 16,000 1.5 NA NA 16,000 1.5 NA NADist, w/water inj. 8,000 3.0 2,667 9.0 8,000 3.0 2,667 9.0

NOTES:1. 24,000 is the goal for CL-Extendor which is expected to be validated from field experience.

Table 8. Maintenance intervals

Table 9. MS6001B full uprate experience list (firing temperature +35°F)



List of FiguresFigure 1 Cross section of MS6001 Gas TurbineFigure 2 Cross section through combustion systemFigure 3a Slot-cooled liner with TBC appliedFigure 3b. Thermal barrier coatingFigure 4 Full Nimonic-263 transition piece uprate with cloth sealsFigure 5a Cross section through CL-ExtendorFigure 5b New aft bracket arrangementFigure 5c Cloth seals for transition piecesFigure 6 NOx emission levels at 15% O2 (ppmvd)Figure 7 Cross section of DLN-1 combustion systemFigure 8 Combustion cover with steam injection nozzlesFigure 9 Effects of steam injection on output and heat rateFigure 10 Breech loaded fuel nozzleFigure 11 Effects of water injection on output and heat rateFigure 12 High-flow IGV design improvements with GTD-450 materialFigure 13 Cross section through turbine sectionFigure 14 Stage 1 bucket GTD-111 perimeter-cooledFigure 15 Stage 2 bucket improved cooling (6 cooling holes)Figure 16 Stage 1 nozzle showing cooling and sealing modificationsFigure 17 Stage 2 nozzle creep deflection comparison Figure 18 Stage 2 nozzle cooling airflowFigure 19 Improved Stage 1 shroudsFigure 20 Stage 2 shroud with honeycomb sealingFigure 21 High pressure packing brush sealFigure 22 Stage 2 nozzle interstage brush sealFigure 23 PG6581B configuration (PG6BEV2 and PG6571B harmonization)Figure 24 PG6581B upgraded componentsFigure 25 13th compressor stage extraction for stage 2 nozzle coolingFigure 26 High performance exhaust diffuserFigure 27 Performance comparison between PG6561B and PG6581B model

List of TablesTable 1 MS6001 performance historyTable 2 Delta changes in gas turbine output as a result of each CM&U packageTable 3 Delta changes in gas turbine heat rate as a result of each CM&U packageTable 4 Changes to exhaust energy for each CM&UTable 5 All components required to operate at a higher firing temperature (+35°F)Table 6 AGT PG6561B/6BEV/6BEV2 improved featuresTable 7 PG6BEV2 and PG6581B fleetTable 8 Maintenance intervalsTable 9 MS6001B full uprate experience list (firing temperature: +35°F)



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