GAS TURBINE 4

External Services (Gas Turbines)

1HDGT.PPT/

Heavy-Duty Gas Turbine Operating and Maintenance Considerations


2HDGT.PPT/

A Maintenance Program should:

Optimize owner’s maintenance costs

Maximize equipment availability


3HDGT.PPT/

Case 2

1,000 Hrs/Yr400 Starts/Yr

HGP at 3 years, not 24 years

Case 1

8,000 Hrs/Yr160 Starts/Yr

HGP at 3 years

Because not all customers operate their gas turbines the same,

not all customer maintenance programs are the same.

BHEL Provides Guidance for Customer Maintenance Planning


4HDGT.PPT/

Factors Affecting Maintenance Planning and Maintenance Program

MaintenanceProgram

MaintenanceProgram

ManufacturersRecommendedMaintenance

Program

ManufacturersRecommendedMaintenance

Program

DiagnosticsDiagnostics

AvailabilityNeed

AvailabilityNeed

On-SiteMaintenance

Capability

On-SiteMaintenance

Capability

DesignFeaturesDesign

Features

UtilizationNeed

UtilizationNeed

DutyCycleDutyCycle

EnvironmentEnvironment

Cost ofDowntimeCost of

Downtime

Type ofFuel

Type ofFuel

ExpertSystems

ExpertSystems

ReserveRequirements

ReserveRequirements


5HDGT.PPT/

Potential Failure Modes

Continuous Duty Application– Creep Deflection– Creep Rupture– Corrosion– Oxidation– Erosion– High-Cycle Fatigue

Hot-Gas-Path Components

Cyclic Duty Application– Themal Mechanical

Fatigue– Rubs/Wears


6HDGT.PPT/

GE Bases Gas Turbine Maintenance Requirements on Independent Counts of Starts & Hours

Fatigue Limits Life

Failure Region

DifferentMechanismLimit Life

OxidationCreep,

Corrosion& Wear

Limit Life

DesignLife

HoursGE Inspection

Recommendation

CompetitionInspection

Recommendation(Equivalent Hours Per Start)

GE InspectionRecommendation

StartsDesign

Life


7HDGT.PPT/

GE vs. Equivalent Hours Approach

0

200

400

600

800

1000

1200

0 4 8 12 16 20 24 28

EOH METHOD

GEMETHOD

Case 24000 Hrs/Yr300 Starts/YrGE Every 4 YrsEOH Every 2.4 Yrs

Case 18,000 Hrs/Yr160 Starts/YrGE Every 3 YrsEOH Every 2.1 Yrs

Fired Hours (x1000)

Starts


8HDGT.PPT/

Maintenance Cost and Equipment Life Are Influenced by Key Service Factors

Fuel

Firing Temperature

Steam/Water Injection

Cyclic Effects (Start-up rate, number of trips)

Air Quality

Service Factors Different From the Reference ConditionService Factors Different From the Reference Condition**Can Increase Maintenence Cost & Reduce Maintenence IntervalsCan Increase Maintenence Cost & Reduce Maintenence Intervals

Service Factors Different From the Reference ConditionService Factors Different From the Reference Condition**Can Increase Maintenence Cost & Reduce Maintenence IntervalsCan Increase Maintenence Cost & Reduce Maintenence Intervals


9HDGT.PPT/

Maintenance FactorsHot Gas Path (Buckets & Nozzles)

Typical Max Inspection Intervals (MS6B/Ms7EA)Hot Gas Inspection 24,000 hrs or 1200 StartsMajor Inspection 48,000 hrs or 2400 Starts

Criterion is Hours or Starts (Whichever Occurs First)

Hours Factors

FuelGas 1Distillate 1.5Crude 2 to 3Residual 3 to 4

Peak Load 6 Water/Steam Injection

Dry Control 1 (GTD-222)Wet Control 1.9 (5% H20)

Factors Impacting Maintenance

Starts Factors

Trip From Full Load 8 Fast Load 2 Emergency Start 20


10HDGT.PPT/

Maintenance Factors Reduce Maintenance Interval

0

200

400

600

800

1000

1200

1400

0 4 8 12 16 20 24 28

Starts FactorsTrips, Fast Starts

Hours Factors• Firing Temp• Steam/H2O Injection•Fuel Type

Fired Hours (x1000)

Starts


11HDGT.PPT/

Estimated Effect of Fuel Type on Maintenance

Residual

MaintenanceFactor

Distillates

HeavyLight

Natural Gas

7 8 9 10 11 12 13 14 15

Fuel Percent Hydrogen by Weight in Fuel

20


12HDGT.PPT/

Hot Corrosion

Life

Oxidation is Limiting Factor

Corrosion becomes Limiting Factor

Na Concentration in Combustion Products

Component surface saturated with condensated corrosive deposits. Life limited primarily by kinetics of thecorrosion reaction.


13HDGT.PPT/

Life Factor

Change in firing temperature - degrees F

Peak rating ofTf + 100 F (65 C) has life factor of 6

Bucket Life Firing Temperature Effect

(MS6001B/MS7001EA/MS9001E)

(MS5001P Uncooled bucket)

0.01

0.1

1

10

100

-200 -100 0 100 200


14HDGT.PPT/

Example 1:

A unit which has operated at Peak Load (+100 F) for 100 hours would have to be operated at - 50 F for 833 hours to maintain a maintenance factor of ONE.

MF =

833 hrs (0.4) + 100 hrs (6.0)

(833 + 100) hrs=

Factored HoursActual Hours

= 1


15HDGT.PPT/

Example 2:

Determine the Maintenance Factor for a unit which operates at Base Load for 6000 hours, Peak Load for 600 hours, and at -50 F Firing Temperature for 15000 hours.

MF =

6000 hrs (1.0) + 500 hrs (6.0) + 1500 hrs (0.4)

(6000 + 1500 + 500) hrs=

Factored HoursActual Hours

MF = 1.2


16HDGT.PPT/

1000

1500

2000

2500

20 40 60 80 100 120

Firing Temp.

Fo

% Load

57 VIGV

84 VIGV

Close IGVs 84 to 57 deg

Tf constant @2020 F

o

o

Close IGVs 84 to 57 deg

Tx constant @ 700 deg F

Heat Recovery

Simple Cycle

Firing Temperature and Load

Heat Recovery vs Simple Cycle


17HDGT.PPT/

1

10

-200 -150 -100 -50 0 50

5

Maximum Heavy FuelFiring Temperature

Delta Firing Temperature Fo

Maintenance Factor Residual

Crude

Heavy Fuel Maintenance Factors(MS6001B/7001EA/9001E)

2


18HDGT.PPT/

Steam/Water Injection and Nozzle Creep Deflection

3rd StageNozzle

2nd StageNozzle

Steam/Water Injection Impacts Stage 2/3 Nozzle Maintenanceand Life

Increases Nozzle Gas Loads

Increases Downstream Deflection Rate

Decreases Maintenance Interval

GTD-222 Nozzle Alloy MinimizesThis Effect


19HDGT.PPT/

Steam/Water Injection Increases Metal Temperature of

Hot-Gas-Path Components

Steam/Water Injection and Bucket/Nozzle Life

• Water Effects Gas Transport Properties:- Thermal Conductivity increases- Specific Heat increases- Viscosity remains steady

• This increases Heat Transfer Coefficients which increases metal temperature and decreases bucket life

Example (MS7001EA Stage 1 Bucket):3% Steam increaes bucket metal temperature 15 F and decreases Life -33%at constant firing temperature


20HDGT.PPT/

0

10

20

30

40

50

Dry Control

Wet Control 3% Steam Inj.TF = 2020 F

Load Ratio = 1.10

3 % Steam Inj.TF = 1994 F

Load Ratio = 1.08

Exhaust Temperature

F

Compressor Discharge Pressure (psig)

0% Steam Inj. TF = 2020 F

Load Ratio = 1.0

Exhaust Temperature Control CurveDry Versus Wet Control

Steam Injection for 25 ppm NOX

o

o

o

o


21HDGT.PPT/

Maintenance Factors Reduce Maintenance Interval

0

200

400

600

800

1000

1200

1400

0 4 8 12 16 20 24 28

Starts FactorsTrips, Fast Starts

Hours Factors• Firing Temp• Steam/H2O Injection•Fuel Type

Fired Hours (x1000)

Starts


22HDGT.PPT/

Exh.Temp.

TimeStart-up Shutdown

Light-offAcceleration

Warm-up

Full SpeedNo Load

Full SpeedNo Load

Load Ramp

Base Load

Fired Shutdown

Trip

Unload Ramp

Turbine Start/Stop Cycle


23HDGT.PPT/

% Load

Mai

nt.

Fac

tor

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 20 40 60 80 100 120

Effect of Start Cycle Max Load Level


24HDGT.PPT/

Low Cycle Fatigue Life Sensitivities First-Stage Bucket

Normal Startup/Shutdown Normal Start & Trip

1 Trip Cycle = 8 Normal Shutdown Cycle

+

-

+

-

Strain- %

Strain- %Temperature Temperature

TMAXTMAX

Leading Edge Temperature/Strain


25HDGT.PPT/

% Load

Trip

Sev

erit

y F

acto

r

0123456789

10

0 20 40 60 80 100 120

Base

FSNL

For trips during Start-upAcceleration, assume Trip Severity Factor = 2

Maintenance Factor - Trips from Load


26HDGT.PPT/

Heavy-Duty Gas Turbine

Combustion

Hot-Gas-Path

Major

Shutdown Inspections Major inspectionHot-Gas-Path

Inspection

CombustionInspection


27HDGT.PPT/

CombustorDesign

NOx

EmissionsLevel (ppm) Diluent

Fuel

GasHours/Starts

DistillateHours/Starts

Dry

Steam

Water

Steam

Water

Standard Liner

65

42

8,000/800

----

----

8,000/400

6,500/300

8,000/800

8,000/400

6,500/300

3,000/150

1,500/100

MS7001EA Combustion Inspection Intervals

Extendor Combustion System Wear Kit IncreasesCombustion Inspection to as Much as 24,000 Hours


28HDGT.PPT/

Base Line Recommended Inspection Intervals Base Load - Gas Fuel - Dry

Factors That Can Reduce Maintenance Intervals

Fuel

Load Setting

Steam/Water Injection

Peak Load Tf Operation

Trips from Load Start Cycle HGP Hardware Design

Type ofInspection

Combustion

Hot-Gas Path

Major

Hours/Starts

12000/800

MS32/52/51 Upgrade

Eliminated/1200

4800/2400

8000/800

24000/900

48000/2400

12000/800

24000/1200

48000/2400

MS6B MS7E/EAMS9E/7FA/

9FA

8000/800

24000/1200

48000/2400


29HDGT.PPT/

Maintenance Factor Definition

IDEAL INTERVAL = Interval for Continuous Base Load on Clean Natural Gas

RECOMMENDED INTERVAL = Ideal Interval determined from

application of maintenance factors


30HDGT.PPT/

N2 / N3 Material

GTD-222 / FSX-414GTD-222FSX-414

GTD-222 / FSX-414

HGPI Hours Based CriterionMS6001/7001/9001

Maintenance Interval(Hours)

=24000

Maintenance FactorWhere:

Maintenance Factor = Factored Hours

Acutal Hours

Factored Hours = (K + (M x I)) x (G + 1.5 D + Af H + 6 P)

Actual Hours = (G + D + H + P)G = Operating Hours on Gas FuelD = Operating Hours on Distillate FuelH = Operating Hours on Heavy Fuel

Af = Heavy Fuel Severity Factor (Residual Af = 3 to 4, Crude Af = 2 to 3)

P = Peak Load Operating HoursI = Percent Water/Steam Injection Referenced to Inlet Air FlowM & K = Water/Steam Injection Constants

M

00

.18

.18

K

11.61

Control

DryDryDryWet

Steam Injection

< 2.2 %> 2.2 %> 2.2 %> 0 %


31HDGT.PPT/

S = Maximum Starts-Based Maintenance Interval (Model Size Dependent)NA = Number of Part Load Start/Stop Cycles (< 60% Load)NB = Number of Normal Base Load Start/Stop CyclesNP = Number of Peak Load Start/Stop CyclesE = Number of Emergency StartsF = Number of Fast Load Starts

Tn = Trips

aT n = Trip Severity Factor

n = Trip number

S

1,2001,200900900

HGPI Starts Based CriterionMS6001/7001/9001 Maintenance Interval

(Starts)=

S

Maintenance FactorWhere:

Maintenance Factor = Factored Starts

Acutal Starts

Factored Starts = (0.5 NA + NB + 1.3 NP + 20 E + 2 F +

Actual Starts = (NA + NB + NP + E + F)

Model Series

MS6B/MS7EAMS6FAMS9E

MS7F/7FA/9F/9FA

aTi Ti )

n

i = 1


32HDGT.PPT/

First-Stage Nozzle Wear - Preventive MaintenanceGas-Fired - Continuous Duty - Base Load

NozzleCondition

New Nozzle Acceptance Standards

Repaired NozzleMin. AcceptanceStandard

1st Repair

2ndRepair 3rd

Repair

Severe Deterioration

Repair CostExceedsReplacementCost

WithoutRepair

Operating Hours

10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000


33HDGT.PPT/

Combustion LinersTransition PiecesFuel NozzlesCross-Fire Tubes1st Stage Nozzles2nd Stage Nozzles3rd Stage Nozzles1st Stage Buckets

2nd Stage Buckets3rd Stage Buckets1st Stage Shrouds2nd/3rd Stage Shrouds

CICICICI

HGPIHGPIHGPIHGPI*

HGPIHGPIHGPIHGPI

5 (CI)6 (CI)3 (CI)3 (CI)

3 (HGPI)3 (HGPI)3 (HGPI)2 (HGPI)

3 (HGPI)**3 (HGPI)3 (HGPI)2 (HGPI)3 (HGPI)

5 (CI)6 (CI)3 (CI)3 (CI)



RepairInterval

Replace Interval(Hours)

ReplaceInterval(Starts)

CI = Combustion Inspection IntervalHGPI = Hot Gas Path Inspection Interval* When recoating, perform after one hours-based HGPI** Two HGPI without recoat, Three HGPI with Recoat

Estimated Repair & Replacement


34HDGT.PPT/

Maintenance Factors Summary

Maintenance Requirements are Based on an Independent Count of Hours and Starts

Certain Operating Factors Reduce Maintenance Intervals Peak Loac Steam/Water Injection >2.2% Liquid Fuel Trips From Load Fast Starts

Exceeding GE Specification Limits can Significantly Increase Maintenance Factors and Reduce Component Life

Equations for Establishing Application Specific Hot Gas Path Maintenance Intervals are Available


35HDGT.PPT/

Bucket Life Firing Temperature EffectMS6001B / MS7001EA / MS9001E

100

LifeFactor

1

10

0 50 100 150 200 250

0 25 50 75 100 125

Peak Rating+100°F (56C) T.Life Factor -6

C

Change inFiring

Temperature


36HDGT.PPT/

Operating Inspection Data ParametersSpeed

Load

Fired Starts

Fired Hours

Site Barometric Reading

Temperatures

Inlet Ambient

Compressor Discharge

Turbine Exhaust

Turbine Wheelspace

Lube Oil Header

Lube Oil Tank

Bearing Drains

Exhaust Spread

Pressures

– Compressor Discharge

– Lube Pump(s)

– Bearing Header

– Cooling Water

– Fuel

– Filters (Fuel, Lube, Inlet Air) Vibration Data for Power Train Generator

– Output Voltage

– Phase Current

– VARS

– Load Start-Up Time Coast-Down Time

– Field Voltage

– Field Current

– Stator Temp.

– Vibration


37HDGT.PPT/

Deterioration of Gas Turbine Performance Due to Compressor Blade Fouling

8

6

4

2

0

-2

-4

-6

-8

-10

-12

-14

Heat RateIncrease

%

OutputDecrease

%

-1 -2 -3 -4 -5 -6 -7 -8

5% Loss ofAirflow

Fouling

Fouling

Pressure Ratio Decrease - %


38HDGT.PPT/

Maintenance Inspections Hot Gas Path Inspection - Key Elements

Foreign Objects Damage

Oxidation/Corrosion/Erosion

Cracking

Cooling Hole Plugging

Remaining Coating Life

Nozzle Deflection/Distortion

Abnormal Deflection/Distortion

Abnormal Wear

Missing Hardware

Clearance Limits

Potential Actions:Potential Actions:Potential Actions:Potential Actions:Inspect for:Inspect for:Inspect for:Inspect for:Key HardwareKey HardwareKey HardwareKey Hardware

Nozzles (1,2,3)

Buckets (1,2,3)

Stator Shrouds

IGV’s & Bushings

Compressor Blading(Borescope)

Repair/Refurbishment Nozzles

Weld RepairRepositionRecoat

BucketsStrip & RecoatWeld RepairBlend

Criteria:Criteria: Op. & Instr. ManualOp. & Instr. Manual TIL’sTIL’s Field EngineersField Engineers

Inspection Inspection Methods:Methods:

VisualVisual LPLP BoroscopeBoroscope

Combustion Inspection Work Scope – Plus:Combustion Inspection Work Scope – Plus:

Availability of On SiteAvailability of On SiteSpares Is Key to Spares Is Key to

Minimizing DowntimeMinimizing Downtime


39HDGT.PPT/

Maintenance Inspections Combustion Inspection - Key Elements

Foreign Objects Abnormal Wear Cracking Liner Cooling Hole Plugging TBC Coating Condition Oxidation/Corrosion/Erosion Hot Spots/Burning Missing Hardware Clearance Limits Borescope Compressor and

Turbine


Combustion Liners

Combustion Covers

Fuel Nozzles

Transition Pieces

Cross Fire Tubes

Flow Sleeves

Check Valves

Spark Plugs

Flame Detectors

Flex Hoses

Repair/Refurbishment Liners

Cracking/Erosion/Wear

TBC Repair Transition Pieces

WearTBC RepairDistortion

Fuel NozzlesPluggingErosion/Wear

Cross Fire TubesWear/Burning



VisualVisual LPLP BoroscopeBoroscope

Availability of On SiteAvailability of On SiteSpares Is Key to Spares Is Key to

Minimizing DowntimeMinimizing Downtime


40HDGT.PPT/

Maintenance Inspections GT Major Inspection - Key Elements

Foreign Objects Damage Oxidation/Corrosion/Erosion Cracking Leaks Abnormal Wear Missing Hardware Clearance Limits


Compressor Blading

Turbine Wheels Dovetails

Journal and Seal Surfaces

Bearing Seals

Inlet System

Exhaust System

Repair/Refurbishment Stator Shrouds

Oxidation/Corrosion/Erosion

BucketsCoating DeteriorationFOD/Rubs/CrackingTip Shroud DeflectionCreep Life Limit

NozzlesSevere Deterioration

IGV BushingsWear

Bearings/SealsBooring/Wear

Compressor BladesCorrosion/ErosionRubs/FOD



VisualVisual LPLP BorescopeBorescope

Combustion Inspection Work Scope Combustion Inspection Work Scope Hot–Gas Path Inspection Work Scope – PlusHot–Gas Path Inspection Work Scope – Plus

Date post:	12-Nov-2014
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