heavy duty gas turbine maintenance from ge

Heavy-Duty Gas Turbine Operating

and Maintenance Considerations

2HDGT.PPT/

GT INSPECTIONS

• Running Inspections

• Standby Inspections

• Shutdown Inspections

3HDGT.PPT/

RUNNING INSPECTIONS PRE START UP CHECKS

• AC Lube Oil Pumps “ON”on Auto

• Ratcheting / Barring is OK.

• EOP is tested

• All MCC modules are switched ‘ON’ and are kept on ‘AUTO’

• Cooling Water level is OK

• Lube Oil Level is OK & Oil temp. normal

• Visual Inspection of Machine is OK

4HDGT.PPT/

RUNNING INSPECTIONS CHECKS DURING STARTUP

• Flame is sensed in all Flame Scanners

• Exhaust Temperatures are uniform and Spread is normal

• Acceleration is Smooth and Time taken is in line with earlier

values

• Rise in Exhaust Temperature is Uniform

• Exhaust Temperature profile is OK and Spread Values are

within Limits

5HDGT.PPT/

• Rise in Wheelspace Temperature is Uniform

• Vibrations are within Limits and as per earlier values

• Bearing Oil Drain Temperatures are Normal

• Opening of Jaw Clutch (Not applicable for Fr9E & Fr6FA) is

at approx. at the same Speed as earlier

RUNNING INSPECTIONS CHECKS DURING STARTUP CONTD.

6HDGT.PPT/

RUNNING INSPECTIONS PARAMETERS TO MONITOR

Pressure

Lube OilHydraulic OilTrip OilComp. DischargeInlet Air Filter DPCooling water

Temperatures

Lube Oil HeaderBrg. DrainsComp. InletComp. DischargeExhaustWheelspaceCooling Water Outlet

7HDGT.PPT/

OTHERS

VibrationsNoise, RubsStartup TimeCoast Down TimeFired StartsFired Hours

GENERATOR

VoltageCurrentLoadStator Temperatures

RUNNING INSPECTIONS PARAMETERS TO MONITOR-CONT’D

Operating Inspection Data Parameters -Summary

SpeedLoadFired StartsFired HoursSite Barometric ReadingTemperatures

Inlet AmbientCompressor DischargeTurbine ExhaustTurbine WheelspaceLube Oil HeaderLube Oil TankBearing DrainsExhaust Spread

Pressures– Compressor Discharge– Lube Pump(s)– Bearing Header– Cooling Water– Fuel– Filters (Fuel, Lube, Inlet Air)

Vibration Data for Power TrainGenerator

– Output Voltage – Phase Current– VARS– Load

Start-Up TimeCoast-Down Time

– Field Voltage– Field Current– Stator Temp.– Vibration

9HDGT.PPT/

RUNNING INSPECTIONS OPERATIONAL DIAGNOSTICS

Start up

Load Hunting

Combustion Trouble / exhaust spread

Lower Loads

Higher Temperatures

10HDGT.PPT/

STANDBY INSPECTION

Inspections carried out during Off-peak periods when Unit is not running

• Check Battery system, Oil levels, instrument calibrations, replacement of various filters & servicing of accessory systems etc.

• Crank the Turbine once in a Fortnight to drive away Moisture

A Maintenance Program should:

Optimize owner’s maintenance costs

Maximize equipment availability

PERIODIC SHUTDOWN INSPECTIONS

Factors Affecting Maintenance Planning and Maintenance Program

MaintenanceProgram

MaintenanceProgram

ManufacturersRecommended

MaintenanceProgram

ManufacturersRecommended

MaintenanceProgram

DiagnosticsDiagnostics

AvailabilityNeed

AvailabilityNeed

On-SiteMaintenance

Capability

On-SiteMaintenance

Capability

DesignFeaturesDesign

Features

UtilizationNeed

UtilizationNeed

DutyCycleDutyCycle

EnvironmentEnvironment

Cost ofDowntimeCost of

Downtime

Type ofFuel

Type ofFuel

ExpertSystemsExpert

Systems

ReserveRequirements

ReserveRequirements

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 similarly

not all customer maintenance programs are the same.

BHEL Provides Guidance for Customer Maintenance Planning

Maintenance Cost and Equipment Life Are Influenced by Key Service Factors

FuelFiring TemperatureSteam/Water InjectionCyclic Effects (Start-up rate, number of trips)Air Quality

Service Factors Different From the Reference Condition*Can Increase Maintenance Cost & Reduce Maintenance Intervals

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

Potential Failure Modes

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

Hot-Gas-Path Components

Cyclic Duty Application– Thermal Mechanical Fatigue– Rubs/Wears.

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 6Water/Steam Injection

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

Factors Impacting Maintenance

Starts Factors

Trip From Full Load 8Fast Load 2Emergency Start 20

17HDGT.PPT/

Operation of Gas Turbine in Extended lean-lean base mode in DLN-1 units has a maintenance factor of 10

Maintenance Factor Definition

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

RECOMMENDEDINTERVAL = Ideal Interval determined from

application of maintenance factors

Maintenance Factors Summary

Maintenance Requirements are Based on an Independent Count of Hours and StartsCertain Operating Factors Reduce Maintenance Intervals

Peak LoadSteam/Water Injection >2.2%Liquid FuelTrips From LoadFast Starts

Exceeding BHEL Specification Limits can Significantly Increase Maintenance Factors and Reduce Component Life Equations for Establishing Application Specific Hot Gas Path Maintenance Intervals are Available

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 Fuel20

Exh.Temp.

TimeStart-up Shutdown

Light-offAcceleration

Warm-up

Full SpeedNo Load

Full SpeedNo Load

Load Ramp

Base Load

Fired ShutdownTrip

Unload Ramp

Turbine Start/Stop Cycle

540 Deg C

% Load

Trip

Sev

erity

Fac

tor

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

Heavy-Duty Gas Turbine

CombustionHot-Gas-PathMajor

Shutdown Inspections

Major inspectionHot-Gas-Path

InspectionCombustionInspection

Special Inspections

BorescopeIGV Bushing insp.

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

Factors That Can Reduce Maintenance IntervalsFuelLoad CycleSteam/Water InjectionPeak Load Operation

Trips from LoadStart CycleHGP Hardware Design

Type ofInspection

Combustion

Hot-Gas Path

Major

Hours/Starts

12000/800

MS32/52/51 Upgrade (Standard)

Eliminated/1200

48000/2400

8000/900

24000/900

48000/2400

12000/120024000/1200

48000/2400

MS6BStandard& DLN1

MS6FA & 9FA DLN2

MS9EStandard& DLN1

8000/450

24000/900

48000/2400

Maintenance Inspections Combustion Inspection - Key Elements

Foreign ObjectsAbnormal WearCrackingLiner Cooling Hole PluggingTBC Coating ConditionOxidation/Corrosion/ErosionHot Spots/BurningMissing HardwareClearance LimitsBorescope Compressor and Turbine

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

Combustion LinersCombustion CoversFuel NozzlesTransition PiecesCross Fire TubesFlow SleevesCheck ValvesSpark PlugsFlame DetectorsFlex Hoses

Repair/Refurbishment Liners

Cracking/Erosion/Wear TBC Repair

Transition Pieces WearTBC RepairDistortion

Fuel NozzlesPluggingErosion/Wear

Cross Fire TubesWear/Burning

Criteria:Criteria: Op. & Instr. ManualOp. & Instr. ManualTIL’sTIL’sService EngineersService Engineers

Inspection Inspection Methods:Methods:

VisualVisualLPLPBorescopeBorescope

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

Minimizing DowntimeMinimizing Downtime

WORK SCOPE:WORK SCOPE:

Maintenance Inspections Hot Gas Path Inspection - Key Elements

Foreign Objects DamageOxidation/Corrosion/ErosionCrackingCooling Hole PluggingRemaining Coating LifeNozzle Deflection/DistortionAbnormal Deflection/DistortionAbnormal WearMissing HardwareClearance Limits


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. ManualTIL’sTIL’sService EngineersService Engineers



WORK SCOPE: Combustion Inspection work scope +WORK SCOPE: Combustion Inspection work scope +



Maintenance Inspections GT Major Inspection - Key Elements

Foreign Objects DamageOxidation/Corrosion/ErosionCrackingLeaksAbnormal WearMissing HardwareClearance Limits


Compressor Blading

Turbine Wheels Dovetails

Journal and Seal Surfaces

Bearing Seals

Inlet System

Exhaust System

Repair/RefurbishmentStator Shrouds

Oxidation/Corrosion/ErosionBuckets

Coating DeteriorationFOD/Rubs/CrackingTip Shroud DeflectionCreep Life Limit

Nozzles DeteriorationIGV Bushings WearBearings/Seals Boring/WearCompressor Blades

Corrosion/ErosionRubs/FODCriteria:Criteria: Op. & Instr. ManualOp. & Instr. Manual

TIL’sTIL’sService EngineersService Engineers



WORK SCOPE: Combustion Inspection Work Scope + WORK SCOPE: Combustion Inspection Work Scope + HotHot––Gas Path Inspection Work Scope +Gas Path Inspection Work Scope +



28HDGT.PPT/

Estimated Repair/ Replacement CyclesRepair Replacement

Starts Hours

Liners CI 5CI 3CI

TPs CI 6CI 4CI

Fuel Nozzles CI 3CI 2CI

N#1,2,3 HGPI 3HGPI 3HGPI

B#1 HGPI 3HGPI 2HGPI

B#2,3 HGPI 4HGPI 3HGPI

Shroud#1 HGPI 2HGPI 2HGPI

Shroud#2,3 HGPI 4HGPI 3HPGI

Typical and informative only. Depends upon GT type and size

29HDGT.PPT/

FIRST STAGE NOZZLE WEAR FIRST STAGE NOZZLE WEAR -- PREVENTIVE MAINTENANCE PREVENTIVE MAINTENANCE –– LIFE EXTENSION LIFE EXTENSION

Repair/ Replacement Cycles – Life Extension

30HDGT.PPT/

SPARE PARTS PLANNING - CONSIDERATIONS

• Repair / replacement intervals

• Cost

• Procurement cycle time

• Repair cycle time Vs. Inspection down time

• Shelf life

• Storage facilities

• Environment

• Transport facilities

31HDGT.PPT/

Borescope Inspection

32HDGT.PPT/


33HDGT.PPT/


BORESCOPE

RIGID BORESCOPE

FLEXIBLE BORESCOPE

34HDGT.PPT/

VIGV Bushing Inspection

35HDGT.PPT/

VIGV Bushing Inspection

36HDGT.PPT/

SPECIAL DESIGN FEATURES FOR EASY MAINTENANCE• Casings are horizontally split

• With upper half of casings removed, it is possible to remove nozzles and inspect buckets without removing rotor

• All bearing housings are horizontally split and bearings can bereplaced without removing the rotor.

• Large blades are moment weighed and sequenced to avoid rebalancing of rotor after site replacement.

• Components like governing components, fuel nozzles, combustion components are mounted type for easy maintenance.

• All major accessories are separate assemblies and are accessiblefor inspection and maintenance.

DOWN TIME REDUCTION

heavy duty gas turbine maintenance from ge

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