GAS TURBINE OPERATION AND MAINTENANCEP2M FTUISeptember 2008

Operating Factors Affecting MaintenanceType and quality of fuelCondensate, contaminants, etcStarting FrequencyThermal cyclesLoad cyclesThermal cyclesEnvironmentAbrasive and corrosive condition

Inspection IntervalFollowing table shows the operating hours at which inspection should be performed for operation on gas fuel and continuous dutyRecommended Inspection Interval

Note: (1) Hours mean quivalent Operating Hoursreflecting the operation conditions of Gas Turbines

Roll-in and Roll-out ProcedureOne (1) complete set of hot parts shall be ready for Rolling-in. The parts taken out (Roll-out) shall be reused/repaired/rejuvenated prior to the next inspection

Summary of GT Inspection

InspectionProcedureInspection ItemsCombustor InspectionDismantling combustor basketVisual inspection & NDT (1) of fuel nozzles, combustor baskets and transition piecesVisual inspection of turbine blade row 4 and vane row 1 and 4Visual inspection of compressor IGV, blade row 1 and vane row 1Turbine InspectionLifting the upper housing of the turbineVisual inspection and NDT (1) of turbine blades, vanes and sealsCombustor inspection is carried out at the same timeMajor Overhaul InspectionLifting the upper housing of the turbine and compressorLifting the rotorVisual inspection & NDT (2) of all components from expansion joint of the inlet air to the first expansion joint of the exhaust gasInspection of auxiliaries, control systems and instruments

NDT (1) : Non Destructive Test (Penetrant Test)NDT (2) : Non Destructive Test (Penetrant Test, Magnetic Particle test and Ultrasonic test

Combustor InspectionNo 1. Compressor inlet (1)No 2. Turbine blade row 4 (1)No 3. Flame detector and igniter (2)No 4. Fuel nozzle (2)No 5. Combustor basket (2)No 6. Transition piece (2)

(1): Visual Inspection(2): Roll-in & Roll-out Parts

Combustion Inspection Schedule(for one (1) Gas Turbine)

Turbine InspectionNo 1. Compressor inlet (1)No 2. Flame detector and igniter (2)No 3. Fuel nozzle (2)No 4. Combustor basket (2)No 5. Transition piece (2)No 6. Turbine blade (2)No 7. Turbine vane (2)No 8. Compressor last row and OGVs blade and diaphragm (1)

(1): Visual Inspection(2): Roll-in & Roll-out Parts

Turbine Inspection Schedule(for one (1) Gas Turbine)

Major Overhaul InspectionNo 1. Flame detector and igniter (1)No 2. Fuel nozzle (1)No 3. Combustor basket (1)No 4. Transition piece (1)No 5. Turbine blade (1)No 6. Turbine vane (1)No 7. Compressor blade and diaphragmNo 8. Exhaust turbine and compressor casing No 9. Compressor blade ringNo 10. Turbine blade ring #1, #2, #3 and #4Turbine journal brg and thrust brgRotor (2)

(1): Visual Inspection(2): Roll-in & Roll-out Parts

Major Overhaul Inspection Schedule(for one (1) Gas Turbine)

Routine Maintenance

Hot Parts Expected Life TimeThe expected life of hot parts has been established based on design strength and the result of past operating experiences. The expected hot parts life hours with qualified repairs are as follows:

Definition of EOHEquivalent Operating HoursTo calculate hours of operation equivalent to base load continuous duty operation, when operation has been with liquid fuel and/or cyclic duty, it is necessary to segregate the actual hours of operation by duty (fired hours per start) and fuel (gas or oil). These segregated values are then used in the following equation to calculate the hours equivalent to operation at base load with gas fuel.

where,H = equivalent continuous duty gas fired hoursBHG = base load operating hours with gas fuel BHO = base load operating hours with distillate oil fuelPHG = peak load operating hours with gas fuel PHO = peak load operating hours with distillate oil fuelCDF = cyclic duty factor, determined from the following table

Cyclic Duty Factor Table

Hot Parts Life EvaluationDeteriorationCreep under High TemperatureLow Cycle FatigueMetal Loss by Surface Oxidation & CorrosionLife diagnosisLoad CyclesStart / Stop FrequencyFuel QualityEnvironmentMaintenance PracticeLife diagnosis procedure is decided based on each customers operational conditions

Life Evaluation MethodEvaluation for Maximum Use-upTurbine Blade Metallurgical Analysis phaseCreep Rupture PropertyTurbine VaneMetallurgical AnalysisPrecipitated CarbideTensile Property

Life Evaluation Process for Turbine Blade

Life Evaluation Process for Turbine Vane

Life Extension TechnologyReheat TechnologyHigh temp. heating of deteriorated super alloy

Decomposition & re-solution of hypertrophied phase and intergranular carbide

Standard heat treatment the material

Recovery of mechanical properties

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