Basic Of Gas Turbine Operating And Maintenance Considerations

(For Power Generation)

Prepared By : Mohd Sarizal Bin Abu BakarDate : 29/1/2009Reference : Power Generation Handbook

: GE Manual

Reminder : This presentation is for MARS training purpose only any reproduction should be directed for MARS permission

Why GT Users Need A Good Operating And Maintenance Consideration??

Why GT Users Need A Good Operating And Maintenance Consideration??

For User : To get a maximum of the life span of the equipments

For MARS: Catastrophic damages like the one occurred on this blade is beyond repairable meaning NO BUSINESS!!However a very good maintenance practices by clients means a longer operating and late business for us. So you neither want a very clever clients nor the bad ones!! (Kidding)

SO Seriously.. Why GT Users Need A Good Operating And

Maintenance Consideration??

• Advanced planning is essential to reduced downtime• To get a minimum downtime for inspection and overhauls

(components repair included)• Can perform on-site inspection and maintenance• To get a maximum value of their parts :

-Replace VS Refurbish which one is more cost saving??? -Extended refurbish is it worth the money save vs the risk ??

So what factors are should be take into account for Maintenance Planning

Alternative Approaches: Replace v Refurbish

Time

New New

Refurbish 1

Refurbish 2Refurbish 3

Replace: Both Approaches

Condition

Overhaul 1 Overhaul 2 Overhaul 3 Overhaul 4

Alternative Approaches: Extend Outage Intervals

Condition

Time

New

Refurbish 1

Refurbish 2

Replace: Both Approaches

Overhaul 1 Overhaul 2 Overhaul 3

ExtendOverhaul 1

ExtendOverhaul 2

Extended refurbish 1

Which Part Require the most careful attention for maintenance??

• HOT GAS PATH• -Combustors and the section exposed to the hot gases discharged from combustors.• These include:1. Combustion liners2.Cross fire tubes3. Transition Pieces 4. Turbine Nozzles 5. Turbine stationary shrouds 6. Turbine Buckets

Parts that require periodic maintenance??

1. Control devices2. Fuel metering3. Gas turbine auxiliaries

Maintenance features for Heavy Gas Turbine

• Most of the components can be maintained on site•All of casings, shells and frame of the machine are horizontally split along the centre line. The upper halves can be lifted individually to provide access to the internal parts.•All stator vane can be removed circumferentially they can be inspected and replaced without removing the rotor. •The nozzle (stationary blades) can be removed for inspection, repair or replacement without removal of the rotor following removal of turbine shell•The weight and weight profile of the turbine buckets are recorded in sets and be replaced without needing to rebalance the rotor •The bearing housing and liners are horizontally split along centerline and can be inspected and replaced if necessary •All of the packings for seals and shafts are separate from the main bearing housings and casing thus can be removed and replaced•The fuel nozzles, combustion liners and flow sleeve can be removed and inspected without removing combustor or lifting the casing

Type of inspections (shutdown inspection) • Borescope Inspection (B.I)-Visual inspections of the internal components using optical borescope that penetrates the compressors and turbine through designated holes -Normally will determine the next progress of shutdown if any deficiencies are found the casings and shells from turbine or compressors must be removed to perform the require repairs. Usually perform together with combustion inspection • Combustion Inspection (C.I)-Shutdown inspection of fuel nozzles, liners, transition pieces, cross fire tuberetainers, spark plug assemblies, flame detectors and combustor flow sleeves -Inspection will cover : cracking, corrosion, oxidation, erosion, debris, F.O.D,wear-Spark plug electrodes and insulators will be checked -Consumables items like seals, lockplates, nuts, bolts and gaskets are normallyReplaced.-Visual inspection for first stage turbine nozzles will be perform -Calibration purge and check valves -If test facilities are availabe the removed fuel nozzles, T.P, C.L can be bench testedand repaired on site

Combustion Inspection (what to inspect??)

• Hot Gas Path Inspection- Inspection of all components that were in contact with thehot gas. - The top half need to be removed-All T.P and first stage nozzle need to be removed-Inspection including :oxidation, cracking, corrosion, wear, deterioration,

F.O.D, rubs and build up deposits -Inspection of turbine vanes will be done in place, a FPI will be perform -Bucket tip clearances will be recorded-Replacing faulty instrumentation

-Notes: 1) First stage nozzles experienced the highest temperature thus inspect for

cracking and oxidation 2) Second stage nozzles and third stage nozzles deflection and closure axial

clearance normally will be send to refurbishment, record deflection measurement

3) Inspect for coating degradation at turbine buckets, the exposed base material will increase creep rate of the turbine and accelerating its failure due to reduction of strength

4) Spare part should be available to avoid extension in HGPI

HGPI –What to inspect??

Major Inspection• Examination of all of the internal rotating and stationary components

from inlet to exhaust of the machine basically its cover work of HGPI and CI with extra examination on other parts

• Depending on result of previous inspection (B.I & H.G.P.I)• All parts subjected to wear are inspected • The typical requirements for this inspections are:

1-Inspection off all radial and axial clearances against their original value (MARS doesn’t possess this)2-Inspection of casings, shells, frames and diffusers for cracks and erosion3-Inspection of rotor and stator compressor blades for rubs, impact damage, corrosion pitting, bowing and cracking 4-Inspection of turbine stationary shrouds for clearance, erosion, rubbing, cracking and build up deposits5-Inspection of seals, hooks fit, diapraghm 6-NDT for bucket and wheel dovetails7-Inspection of coating at 1st stage bucket, replaced if necessary 8-Inspection of exhaust system for cracks, broken silencer panels and insulation panels 9-Inspection of alignment of GT to generator and Gt to accessory gear

M.I –what to inspect??

Rotor Blade Removal (M.I)

Fuel Nozzles Inspection (C.I)

Transition Pieces Inspection (C.I)

Removal Of upper half (HGPI)

Borescope Port

Borescope Inspection

Borescope Inspection

Hot Gas Path Inspection

1 st stage nozzle inspection

Liner Inspection (C.I)

Cross Fire Tube inspection (C.I)

Rotor Inspection

Typical Service Factors

• Hot Gas Path Inspection : 24,000 Hrs or 1,200 starts

• Major Inspection:48,000 Hrs or 2,400 starts

Services Factors For G.E Engines

Note: For G.E Engine there is no E.O.H, G.E depend on start cycle and O.H

Factors influencing equipment life

• 4 major factors:• 1) Cyclic effects• 2) Firing Temperature• 3) Fuel• 4) Steam/Water Injection

Limiter life Criteria of GT engines• Continuous Duty Application

• 1) Rupture • 2)Creep Deflection • 3)High Cycle Fatigue• 4)Corrosion • 5)Oxidation • 6)Erosion• 7)Rubs/Wear• 8)F.O.D

• Cyclic Duty Application (Peaking)

• 1) Thermal Mechanical Fatigue• 2) High cycle fatigue• 3) Rubs/Wear• 4) F.O.D

Location of inspection (shutdown inspection)

Location of inspection (shutdown inspection)

GE Frame 5

Frame 7 Rotor

• Thank You

• Q& A Sessions