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GAS TURBINE OPERATION AND MAINTENANCE. P2M FTUI September 2008. Operating Factors Affecting Maintenance. Type and quality of fuel Condensate, contaminants, etc Starting Frequency Thermal cycles Load cycles Thermal cycles Environment Abrasive and corrosive condition. - PowerPoint PPT Presentation
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GAS TURBINE OPERATION AND MAINTENANCEP2M FTUISeptember 2008
Operating Factors Affecting Maintenance• Type and quality of fuel
– Condensate, contaminants, etc• Starting Frequency– Thermal cycles• Load cycles– Thermal cycles• Environment– Abrasive and corrosive condition
Inspection Interval
Following table shows the operating hours at which inspection should be performed for operation on gas fuel and continuous duty
Recommended Inspection Interval
Note: (1) Hours mean Ëquivalent Operating Hours”reflecting the operation conditions of Gas Turbines
“Roll-in and Roll-out” Procedure
One (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
Inspection Procedure Inspection Items
Combustor Inspection Dismantling combustor basket
•Visual inspection & NDT (1) of fuel nozzles, combustor baskets and transition pieces•Visual inspection of turbine blade row 4 and vane row 1 and 4•Visual inspection of compressor IGV, blade row 1 and vane row 1
Turbine Inspection Lifting the upper housing of the turbine
•Visual inspection and NDT (1) of turbine blades, vanes and seals•Combustor inspection is carried out at the same time
Major Overhaul Inspection
Lifting the upper housing of the turbine and compressorLifting the rotor
•Visual inspection & NDT (2) of all components from expansion joint of the inlet air to the first expansion joint of the exhaust gas•Inspection 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 Inspection
No 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 Inspection
No 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 OGV’s blade and diaphragm (1)
(1): Visual Inspection(2): Roll-in & Roll-out Parts
Turbine Inspection Schedule(for one (1) Gas Turbine)
Major Overhaul Inspection
No 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
diaphragm
No 8. Exhaust turbine and compressor casing
No 9. Compressor blade ring No 10. Turbine blade ring #1,
#2, #3 and #4 Turbine journal brg and thrust
brg Rotor (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 Time
The 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 “EOH”Equivalent Operating Hours To 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 Evaluation
1. Deteriorationa. Creep under High Temperatureb. Low Cycle Fatiguec. Metal Loss by Surface Oxidation & Corrosion
2. Life diagnosisa. Load Cyclesb. Start / Stop Frequencyc. Fuel Qualityd. Environmente. Maintenance Practice
Life diagnosis procedure is decided based on each customer’s operational conditions
Life Evaluation Method
Evaluation for Maximum Use-up Turbine Blade
Metallurgical Analysis γ’ phase Creep Rupture Property
Turbine Vane Metallurgical Analysis Precipitated Carbide Tensile Property
Life Evaluation Process for Turbine Blade
Life Evaluation Process for Turbine Vane
Life Extension Technology
Reheat Technology
High temp. heating of deteriorated super alloy
Decomposition & re-solution of hypertrophied γ’ phase and intergranular carbide
Standard heat treatment the material
Recovery of mechanical properties
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