Gas Turbine Maintenence Aspects

8/12/2019 Gas Turbine Maintenence Aspects

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Heavy-Duty Gas TurbineOperatingand MaintenanceConsiderations

YDERABAD


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2HDGT.PPT/

HYDERABAD GT INSPECTIONS

Running Inspections

Standby Inspections

Shutdown Inspections


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Running Inspection DataParameters to be monitored -Summary

Speed

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

HYDERABAD


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4HDGT.PPT/

HYDERABAD

RUNNING INSPECTIONSOPERATIONAL DIAGNOSTICS

Start up

Increased Startup time

Jaw clutch disengagement at a lower speed

Higher vibrations during critical speeds

- Indicative of unhealthy starting means /turbine bearings


5/38 5HDGT.PPT/

HYDERABAD Critical speedsTypical (Fr-5P)

First critical1900 rpm

Second critical3250 rpm

Third critical5200 to 5600 rpm

Critical speedsTypical (Fr-6B)

First critical1650 to 1880 rpm

Second critical3260 to 3900 rpmThird critical7050 to 7350 rpm


6/38 6HDGT.PPT/

HYDERABAD Critical speedsTypical (Fr-9E)

First critical980 rpm

Second critical1300 rpm

Third critical2300 rpm

Critical speedsTypical (Fr-6FA)

First critical 1840 rpm

Second critical 4743 rpm


7/38 7HDGT.PPT/

HYDERABAD


Load Limitation / Hunting

Unable to maintain load

Unable to increase load

- Indicative of clogged hydraulic filters and / ordamaged fuel pump and / orrelief valve

RUNNING INSPECTIONS


8/38 8HDGT.PPT/

HYDERABAD


Combustion Trouble / exhaust spread

Increasing trend in exhaust temperature spread

Changing pattern of exhaust temp. spread with load

- Indicative of unequal fuel distribution tofuel nozzles

RUNNING INSPECTIONS


9/389HDGT.PPT/

HYDERABAD


Lower Loads under similar conditions

Higher Exhaust Temperature under similar

conditions

- Indicative of compressor fouling


10/381HDGT.PPT/

HYDERABAD STANDBY INSPECTION

Inspections carried out during Off-peakperiods when Unit is not running for a longduration

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

Put the unit on ratcheting / barring gear for atleast 30 mindaily

Crank the Turbine once in a Fortnight to drive awayMoisture

Run the Gas Turbine FSNL once every month to avoidcorrosion to turbine wheel dovetails


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A Maintenance Program should:

Optimize owners maintenance costs

Maximize equipment availability

PERIODIC SHUTDOWN INSPECTIONSHYDERABAD


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Factors Affecting Maintenance Planning andMaintenance Program

Maintenance

Program

ManufacturersRecommendedMaintenance

Program

Diagnostics

Availability

Need

On-Site

Maintenance

Capability

DesignFeatures

Utilization

Need

DutyCycle

Environment

Cost ofDowntime

Type of

Fuel

Expert

Systems

Reserve

Requirements

HYDERABAD


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Case 2

1,000 Hrs/Yr

400 Starts/Yr

HGP at 3 years, not 24 years

Case 1

8,000 Hrs/Yr

160 Starts/Yr

HGP at 3 years

Because not all customers operate their gas turbines the similarl

not all customer maintenance programs are the same.

BHEL Provides Guidance for Customer Maintenance Planning

HYDERABAD


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Maintenance Cost and Equipment LifeAre Influenced by Key Service Factors

Fuel

Firing Temperature

Steam/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

HYDERABAD


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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.

HYDERABAD


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1HDGT.PPT/

HYDERABAD

Operation of Gas Turbine inExtended lean-lean base

mode in DLN-1 units has amaintenance factor of 10


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Maintenance Factor Definition

IDEAL INTERVAL = Interval for Continuous Base Loadon Clean Natural Gas

RECOMMENDED

INTERVAL = Ideal Interval determined fromapplication of maintenance factors

HYDERABAD


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Maintenance Factors Summary

Maintenance Requirements are Based on an IndependentCount of Hours and Starts

Certain Operating Factors Reduce Maintenance Intervals

Peak Load

Steam/Water Injection >2.2% Liquid Fuel

Trips From Load

Fast Starts

Exceeding BHEL Specification Limits can SignificantlyIncrease Maintenance Factors and Reduce Component Life

Equations for Establishing Application Specific Hot GasPath Maintenance Intervals are Available

HYDERABAD


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Exh.

Temp.

TimeStart-up Shutdown

Light-offAcceleration

Warm-up

Full SpeedNo Load

Full Speed

No Load

Load Ramp

Base Load

Fired Shutdown

Trip

Unload Ramp

Turbine Start/Stop Cycle

540 Deg C

HYDERABAD


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% Load

T

rip

Severity

Fa

ctor

01

2

3

4

5

67

8

9

10

0 20 40 60 80 100 120

Base

FSNL

For trips during Start-up

Acceleration, assume

Trip Severity Factor = 2

Maintenance Factor - Trips from Load

HYDERABAD


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Heavy-Duty Gas Turbine

CombustionHot-Gas-Path

Major

Shutdown Inspect ions

Major inspectionHot-Gas-Path

Inspection

CombustionInspection

Special Inspect ion s

Borescope

IGV Bushing insp.

HYDERABAD


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Base Line Recommended Inspection IntervalsBase Load - Gas Fuel - Dry

Factors That Can Reduce Maintenance IntervalsFuel

Load Cycle

Steam/Water Injection

Peak Load Operation

Trips from Load

Start Cycle

HGP Hardware Design

Type of

Inspection

Combustion

Hot-Gas Path

Major

Hours/Starts

12000/800

MS32/52/51

Upgrade

(Standard)

Eliminated/1200

48000/2400

8000/900

24000/900

48000/2400

12000/1200

24000/1200

48000/2400

MS6BStandard

DLN1MS6FA & 9FA

DLN2

MS9E

Standard

& DLN1

8000/450

24000/900

48000/2400

HYDERABAD


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Maintenance InspectionsCombustion 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 andTurbine

Potential Actions:Inspect for:Key Hardware

Combustion Liners

Combustion Covers

Fuel Nozzles

Transition PiecesCross Fire Tubes

Flow Sleeves

Check Valves

Spark Plugs

Flame Detectors

Flex Hoses

Repair/Refurbishment

Liners

Cracking/Erosion/Wear

TBC Repair

Transition PiecesWear

TBC Repair

Distortion

Fuel Nozzles

Plugging

Erosion/Wear

Cross Fire TubesWear/Burning

Criteria: Op. & Instr. Manual TILs

Service Engineers

Inspection

Methods: Visual

LP

Borescope

Availability of On Site

Spares Is Key to

Minimizing Downtime

WORK SCOPE:

HYDERABAD

i i


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Maintenance InspectionsHot Gas Path Inspection - Key Elements

Foreign Objects Damage


CrackingCooling Hole Plugging

Remaining Coating Life

Nozzle Deflection/Distortion

Abnormal Deflection/Distortion

Abnormal Wear

Missing HardwareClearance Limits


Nozzles (1,2,3)

Buckets (1,2,3)

Stator Shrouds

IGVs & Bushings

Compressor Blading

(Borescope)

Repair/Refurbishment

Nozzles

Weld Repair

Reposition

Recoat

Buckets

Strip & Recoat

Weld Repair

Blend


Service Engineers

Inspection

Methods: Visual

LP

Borescope

WORK SCOPE: Combust ion Inspect ion wo rk scope +

Availability of On Site

Spares Is Key to

Minimizing Downtime

HYDERABAD

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Maintenance InspectionsGT Major Inspection - Key Elements

Foreign Objects Damage


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 Buckets

Coating DeteriorationFOD/Rubs/CrackingTip Shroud DeflectionCreep Life Limit

Nozzles Deterioration IGV Bushings Wear

Bearings/Seals Boring/Wear Compressor Blades

Corrosion/ErosionRubs/FOD


Service Engineers

Inspection

Methods: Visual

LP

Borescope

WORK SCOPE: Combust ion Inspect ion Work Scope +HotGas Path Inspect ion Work Scope +

Availability of On Sit

Spares Is Key to

Minimizing Downtim

HYDERABAD

E ti t d R i / R l t C l


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2HDGT.PPT/

HYDERABADEstimated Repair/ Replacement Cycles

Repair Replacement

Starts Hours

Liners CI 5CI 3CI

TPs CI 6CI 4CI

Fuel Nozzles CI 3CI 2CI

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

R i / R l t C l Lif E t i


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2HDGT.PPT/

HYDERABAD

FIRST STAGE NOZZLE WEAR - PREVENTIVE MAINTENANCELIFE EXTENSION

Repair/ Replacement CyclesLife Extension

Without repair

Repaired Nozzle

Min AcceptabilityStandard

NozzleCondition

Severe Deterioration

New Nozzle

Acceptance Standard

First repair

2nd repair

3rd repairRepaircostexceeds

replacementcost

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

Operating Hours

SPARE PARTS PLANNING CONSIDERATIONS


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3HDGT.PPT/

HYDERABADSPARE PARTS PLANNING - CONSIDERATIONS

Repair / replacement intervals

Cost

Procurement cycle time

Repair cycle time Vs. Inspection down time

Shelf life

Storage facilities

Environment

Transport facilities

Borescope Inspection


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3HDGT.PPT/

HYDERABAD Borescope Inspection

BORESCOPE INSPECTION CRITERIAACCESS AREA INSPECT FOR

Compressor Blades Foreign object damage

Dirt buildup

Corrosion

Tip Erosion

Trailing Edge thinning

Stator blade root erosion

Tip clearances



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3HDGT.PPT/

HYDERABAD


Combustion Carbon build-up

(Liner and transition piece) Hot spots

Cracking

Bulging

Wear

Missing metal or thermal

barrier coating




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3HDGT.PPT/

HYDERABAD


Turbine Nozzles Foreign object damage

Corrosion

Blocked cooling holes

Cracks

Trailing edge bowing

Erosion

Burning




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3HDGT.PPT/



Turbine buckets Foreign object damage

Corrosion

Blisters

Erosion

Cracks

Tip clearance

Missing metal



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3HDGT.PPT/


BORESCOPE

RIGID BORESCOPE

FLEXIBLE BORESCOPE

VIGV Bushing Inspection


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3HDGT.PPT/

HYDERABAD VIGV Bushing Inspection

1. Set vanes to full open position

2. Set up dial indicator to

measure motion normal to the

vane chord. Position the

indicator to read as close to the

vane inner button as possible

3. Deflect vane in a tangentia

direction (perpendicular to the

air flow direction) to both sides

of the bushing clearance and

record full dial indicator

reading.

AirflowDirection

VIGV

VIGV in fullyOpen Position

84

DialIndicator

VIGV Bushing Inspection


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3HDGT.PPT/

HYDERABAD VIGV Bushing Inspection

DOWN TIME REDUCTION


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3HDGT.PPT/

HYDERABAD

SPECIAL DESIGN FEATURES FOR EASY MAINTENANCE

Casings are horizontally split

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

All bearing housings are horizontally split and bearings can be

replaced 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 accessible

for inspection and maintenance.

DOWN TIME REDUCTION

Gas Turbine Maintenence Aspects

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