gt mtc. practices

8/11/2019 GT Mtc. Practices

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GAS TURBINE MTC.

PRACTICES

GE FRAME 6B,9E & 9FAGAS TURBINES


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GAS TURBINE

Principle of working :- Works on BratonCycle with two nos. Adiabaticprocesses of compression & expansionin compressor and turbine respectivelyand two constant pressure processesi.e. Heat addition in combustionchambers and exhaust in atmosphere.


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WORKING PRINCIPLE

BRATONCYCLE


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The Actual Thermodynamiccycle

For all practical reasons theactual thermal efficiencywill depend on

Pressure ratio Turbine inlet Temp Compressor inlet temp Efficiency of Compressor and

Turbine


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GAS TURBINE

Principle of Operation:- Rotor is initiallybrought to speed by starting means.Atmospheric air is drawn into the compressor

and raised to static pressure more than theatmospheric. This high pressure air isallowed to pass through continuous flowCombustion Chambers where fuel is ignitedwith high voltage igniters. The product ofcombustion is expanded in the turbine whichcause it to spin and thus applying a torque tothe driven accessories i.e. Generator


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WORKING PRINCIPLE


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9/59Time

1

2

3

4

0

0-1 Cranking1-2 Purging2-3 Speed down to firing speed3- Firing3-4 Warm up4-5 Acceleration5-6 Full Speed no load

5 6

Torque converter angle

Fuel

Speed


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MAINTENANCE PLANNING

TO KEEP LOW COST OF OPERATION& HIGH AVAILABILITY OF M/Cs, AWELL PLANNED MTC. PROGRAMMEIS REQUIRED


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FACTORS AFFECTING MTC.PLANNING

TYPE OF FUEL USEDFIRING TEMPERATUREOVERSPEED OPERATION OF M/C

DESIGN FEATURESDUTY CYCLEPARTS AVAILABILITYON SITE MTC. CAPABILITY

DIAGNOSTIC & EXPERT SYSTEM OFANALYSISMFRS RECOMMENDED MTC. PROGRAM


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DUTY CYCLE

MTC. PLANNING IS AFFECTED BYNATURE OF OPERATION PHILOSOPHY I.E.PEAKING OR BASE LOAD OPERATIONS,STANDBY OPERATION & NO. OF STARTS& SHUTDOWNS.

GAS TURBINE WEARS IN DIFFERENTWAYS FOR DIFFERENT SERVICEREQUIREMENTS AND DUTY CYCLES.

THERMAL MECHANICAL FATIGUE IS THELIMITER FOR CYCLIC OPERATION ANDCREEP, OXIDATION, HOT CORROSION ARETHE LIMITER FOR CONTINUOUS DUTYAPPLICATIONS


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CYCLIC DUTY OPERATIONS

EFFECTSTMFHCFRUB/ WEAR

FOD


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CONT. DUTY OPERATIONS

EFFECTSCREEPRUPTURE

HCFCORROSIONOXIDATIONEROSIONRUB/WEARFOD


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OPERATING DUTY DEFINITION

FiredDuty Service Factor Hrs/Starts

Stand-by 90 % >>50


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FIRING TEMPERATUREFIRING TEMP. IS THE LIMITING FACTORFOR LOAD ON THE TURBINE. HIGHER THEFIRING TEMP. SHORTER WILL BE THE

MTBI. HIGH FIRING TEMP. MAY BE DUETO- PEAK LOAD OPERATION OF M/CWET CONTROL CURVE OPERATION OF M/C

WITH STEAM/WATER INJECTION OR WITHINLET FOGGINGPART LOAD OPERATION OF M/C INCOMBINED CYCLE


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TYPE OF FUEL USED

WITH USE OF HEAVY FUELS IN GTs, THEMTC. INTERVALS ARE REDUCED AS DUETO BURNING OF HEAVY FUELS RADIANT

THERMAL ENERGY IS RELEASEDRESULTING INTO REDUCTION OF HGPSPARES LIFE. ALSO PRESENCE OFCORROSIVE ELEMENTS IN THE HEAVY

FUELS HOT CORROSION IN HGP SPARESIS INCREASED.

CONTD .


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TYPE OF FUEL USEDFUEL USED IN GAS TURBINE IS THE KEYFACTOR IN DECIDING THE MTC.PLANNING. THE SEVERITY FACTOR FOR

VARIOUS FUELS ARE AS FOLLOW - GAS - 1 DISTILLATE - 1.5

CRUDE - 2 TO 3RESIDUAL - 3 TO 4


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BASE LINE OPERATION

GAS TURBINE OPERATION ON GASFUEL FOR CONTINUOUS DUTY CYCLEWITH NO STEAM/ WATER INJECTION ISCALLED BASE LINE OPERATION .

IN BASE LINE OPERATION MTC.INTERVAL BETWEEN TWO INSPECTIONS

IS THE MAXIMUM AS THE MTC. FACTORIS UNITY.


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OVER SPEED OPERATION

MTC. FCATOR FOR OVER SPEEDOPERATION OF MACHINE-

SPD100 101 102 103 104 105

MF 1 1.2 1.4 1.6 1.8 2


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DESIGN FEATURES

ALL THE CASINGS STARTING FROM INLETPLENUM TO EXHAUST CASING ARE SPLIT

AT HORIZONTAL CENTRE LINE TOACCESS INTERNALS FOR INSPECTION/REPLACEMENT. BRGS., IGV, COMP.STATOR BLADES, NOZZLES, SHROUDSETC, CAN BE REPLACED WITHOUTACTUALLY LIFTING THE TURBINE ROTOR


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MFR. RECOMMENDED MTC.PROGRAMME

AS PER GE FOLLOWING PREVENTIVE MTC.INSPECTIONS ARE CARRIED OUT ON GTs

BOROSCOPIC INSPECTIONCOMBUSTION INSPECTION (CI)HOT GAS PATH INSPECTION (HGPI)MAJOR INSPECTION (MI)


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COMBUSTION INSPECTION

DURING CI, FUEL NOZZLES ANDCOMBUSTION CHAMBERS OF GASTURBINE ARE DISASSEMBLED FORINSPECTION AND BOROSCOPICINSPECTION IS CARRIED OUT FORCOMPRESSOR AND TURBINEPORTION

CONTD....


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DURING CI FOLLOWING SPARES AREINSPECTED/ REPLACED

FUEL NOZZLESCOMBUSTION LINERSTRANSITION PIECESX. FIRE TUBESRETAINERSEND SEAL BLOCKS

BULL HORNEND SEALS


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RECOMMENDED INTERVAL FOR CI ISAS GIVEN BELOW-

TYPE OFINSP

RECOMMENDED HRS/STARTS

6B 9E 9FA

CI DLN 12000/450 12000/450 8000/450

NONDLN

12000/1200 8000/900 -


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CALCULATION FOR MTC. INTERVAL FOR CI BASED ONHRS CRITERION -

MTC. INTERVALS (HRS)= RECOMMENDED HRS

MTC. FACTORMTC. FACTOR = ANNUAL FACTORED HRS

ANNUAL ACTUAL HRS

ANNUAL FACTORED HRS = G+ 1.5D + 3H + 6PANNUAL ACTUAL HRS = G + D + H + P

G = ANNUAL HRS OF OPR. ON GAS FUELD = ANNUAL HRS OF OPR. ON DISTILLATE FUELH = ANNUAL HRS OF OPR. ON HEAVY FUELP = ANNUAL HRS OF OPR. ON PEAL LOAD



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HOT GAS PATH INSPECTION

DURING HGPI, FUEL NOZZLES,COMBUSTION CHAMBERS ANDTURBINE PORTION OF GASTURBINE ARE DISASSEMBLED FORINSPECTION AND BOROSCOPICINSPECTION IS CARRIED OUT FOR

COMPRESSOR PORTIONCONTD....


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DURING HGPI FOLLOWING SPARES AREINSPECTED/ REPLACED

ALL THE SPARES OF CI + BUCKETS STG .I, II & III SHROUD STG .I, II & III NOZZLE STG .I, II & III VIGV & EXHAUST FRAME

BOROSCOPE INSPECTION OF COMPRESSOR



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RECOMMENDED INTERVAL FOR HGPIIS AS GIVEN BELOW-

TYPE OF INSP RECOMMENDED HRS/STARTS

6B 9E 9FA

HGPI 24000/1200 24000/900 24000/900


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CALCULATION FOR MTC. INTERVAL FOR HGPI BAESDON HRS CRITERION -

MTC. INTERVALS (HRS)= 24000


ANNUAL ACTUAL HRS





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MAJOR INSPECTION

DURING MAJOR INSPECTION,FLANGE TO FLANGE OF GT ISDISASSEMBLED/INSPECTED. ITINCLUDES F/N, CC, TURBINE,COMPRESSOR & BEARINGS. OTHERAUXILIARIES AND SUPPORT SYTEM

I.E. INLET PLENUM, EXHAUSTPLENUM, OIL PUMPS, AGB ETC AREINSPECTED.

CONTD....


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DURING MAJOR INSPECTION FOLLOWINGVITAL SPARES ARE INSPECTED/REPLACED

ALL THE SPARES OF HGPI +VIGV, INLET PLENUM & EXHAUST PLENUM COMPRESSORTURBINE BEARINGSAGB, MOP, AOP, EOP, ATOM. AIR COMP.STARTING MEANS, STARTING CLUTCHATOM. AIR COOLER & L.O. COOLER

MAJOR INSPECTION


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MAJOR INSPECTION

RECOMMENDED INTERVAL FOR MI ISAS GIVEN BELOW-

TYPE OFINSP

RECOMMENDED HRS/STARTS

6B 9E 9FA

MAJORINSP.

48,000/2,400 48,000/2,400 48,000/2,400


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CALCULATION FOR MTC. INTERVAL FOR MAJORIISPECTION BAESD ON HRS CRITERION -

MTC. INTERVALS (HRS)= 48,000


ANNUAL ACTUAL HRS



MAJOR INSPECTION


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LOAD Vs EXHAUST TEMPERATUREVIBRATION LEVELFUEL FLOW AND ITS PRESSUREEXHAUST TEMPERATURE & SPREAD VARIATIONSTART UP TIMECOASTING DOWN TIMEWHEEL SPACE TEMPERATURECPD & CTDINLET AIR DIFF. PRESSURE ACROSS FILTERSEXHAUST PRESSURE DROP

PERFORMANCE INDICATORS


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FACTORS AFFECTING GTPERFORMANCE/ OUTPUT

INLET AIR DIFF. PRESSURE EXHAUST GASES DIFF. PRESSURE

AMBIENT AIR TEMPERATURE GENERATING FREQUENCE STEAM / WATER INJECTION

INLET AIR FOGGINGTYPE OF FUEL USED


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EFFECT OF DIFF. FACTORS ONGT PERFORMANCE/ OUTPUT

INLET AIR & EXH. DIFF. PRESSURE(FRAME 9E)

VALUE F/CONSMP OUTPUT

INLET PRDROP

100 mm ofH2O

+ 0.4 -1.4

EXH. PRDROP

100 mm ofH2O

+ 0.4 - 0.4


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EFFECT OF INLET AIR TEMP. ONGT PERFORMANCE/ OUTPUT

MODEL PG 9001E

INLETTEMP

(F)

EXH.TEMP

(F)

HEATRATE

( )

OUTPUT( )

HEATCONSMP.

( )

AIRFLOW

( )

20 929 97 116 112 108.5

40 939 98.5 108 106 104

60 952 100 100 100 100

80 964 102.5 94 94 95.5

100 978 105 84 88 91.5

120 993 108 77 83 87.5


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MODEL PG9001E

EFFECT OF FREQUENCY ONGT PERFORMANCE/ OUTPUT

FREQUENCY(Hz)

OUTPUT( )

50.0 100

49.5 100

49.0 99

48.5 98

48.0 97

47.5 96

47.0 95


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LIFE OF HGP SPARESMODEL 9E

REPAIR REPLACEMENTF/NOZZLES CI 2 (CI)/3 (CI)

COMBUSTION LINERS CI 3 (CI)/5 (CI)TRANSITION PIECES CI 4 (CI)/6 (CI)X- FIRE TUBES CI 2 (CI)/3 (CI)BUCKETS STG. I, II & III HGPI 2(HGPI)/3(HGPI)

NOZZLES STG. I, II & III HGPI 3(HGPI)/3(HGPI)SHROUDS STG. I, II & III HGPI 3(HGPI)/3(HGPI)


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RELIABILITY

Probability of not being forced out ofservice when unit is needed

RELIABILITY = (1- FOH /PH)X100

FOH Forced Outage Hrs.PH Period Hrs.


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AVAILABILITY

Probability of being available,independent of whether the unit isneeded.

AVAILABILITY = (1- UH /PH)X100

UH Unavailable Hrs.PH Period Hrs.


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EQUIVALENT RELIABILITY

Probability of a combined cycle powerplant not being totally forced out ofservice when unit is required includesthe effect of Gas & Steam cycle MWoutput contribution to plant output.

= [1-{GTFOH +B( HRSGFOH +STFOH)}X100]GTPH BPH STPH

contd.


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EQUIVALENT RELIABILITY

GTFOH = GT Forced Outage Hrs.

GTPH = GT Period Hrs.

HRSGFOH = HRSG Forced Outage Hrs.

BPH = HRSG Period Hrs.

STFOH = Steam Turbine Forced Outage Hrs.

STPH = Steam Turbine Period Hrs.

B = Steam Cycle MW output contribution


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EQUIVALENT AVAILABILITY

Probability of a combined cycle powerplant available for power generationindependent of whether the unit isneeded -includes the effect of Gas &Steam cycle MW output contribution toplant output.

= [1-{GTUH +B( HRSGUH +STUH)}X100]GTPH BPH STPH

contd.


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EQUIVALENT AVAILABILITY

GTUH = GT Unavailable Hrs.

GTPH = GT Period Hrs.

HRSGUH = HRSG Unavailable Hrs.

BPH = HRSG Period Hrs.

STUH = Steam Turbine Unavailable Hrs.

STPH = Steam Turbine Period Hrs.

B = Steam Cycle MW output contribution


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MTBF

MTBF Measure of probability ofcompleting the current run. Failureevents are restricted to forced outageswhile in service.

MTBF= SH/FO

SH Service Hrs.FO Nos. of Forced Outages


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Service Factor

Service Factor Measure ofoperational use usually expressed onan annual basis.

Service Factor = SH/PH X 100

SH Service Hrs.PH Period Hrs.


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OPERATING LEVERAGE

OPERATING LEVERAGE = FIXED COSTVARIABLE COST

OPERATING LEVERAGE IS GETTINGREDUCED AS THE PLANT GOES OLDERDUE TO REDUCTION OF FIXED COST BY

WAY OF DEPRECIATION AND INCREASEIN HEAT RATE DUE TO AGING


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CONTRIBUTION FACTOR

C. FACTOR= TARIFF/KWHVARIABLE COST/KWH

GIVE DC TO SLDC IN SUCH A WAY THATTHE CONTRIBUTION FACTOR SHOULDALWAYS REMAIN POSITIVE TO AVOIDLOSSES. THIS CAN BE DONE BY LOADINGTHE MACHINES OPTIMALLY ANDAVOIDING THE PARTIAL LOADING OFMACHINES FOR LONGER DURATION.

HEAT RATE W R T


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HEAT RATE W.R.T.LOADING

OUT PUT(%)

HR(1 0C)

HR(15 0C)

HR(32 0C)

HR(49 0C)

120 97 99 101 103

100 99 100 102 103

80 105 106 106 107

60 115 115 115 115

40 133 133 133 133


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COMPARISON DIFF MAKE


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COMPARISON DIFF. MAKEGT MODELS

OEM Conventional Advance (F/FA class) Model GT ISO

Output (MW)

Net CC Efficiency(%)

Model GT ISO Output (MW)

Net CC Efficiency (%)

GE 9E 126.10 52.7 9FA 255.6 57.1

Siemens V94.2 159.40 52.2 V94.3A

265.9 57.3

MHI* 701DA 144.09 51.6 701F 270.3 57.0

Alstom 13E2 165.10 52.9 GT 26 263.0 56.3


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FLANGE TO FLANGE VIEW OFF CLASS GAS TURBINE


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QUESTIONS ?


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K. S. YADAVManager (M-I)Pragati Power StationCell - 9717694741email [email protected]

gt mtc. practices

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