Turbine/Generator Upgrades and Maintenance Presented by: Daniel Sculley, Manager Turbine, Generator & Piping Systems Engineering
APP Site Visit Octobe Octoberr 30 – Novemb November er 4, 4, 2006 2006
Topics • • • •
Turb Turbin ine e Bla Bladi ding ng & Ste Steam am Path Path Upg Upgra rade des s Turb Turbin ine e Sto Stop p / Con Contr trol ol Valv Valve e Upg Upgra rade des s Turb Turbin ine e Cont Contro roll Syst System em Mod Moder erni niza zati tion on Generator Im Improvements
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Topics • • • •
Turb Turbin ine e Bla Bladi ding ng & Ste Steam am Path Path Upg Upgra rade des s Turb Turbin ine e Sto Stop p / Con Contr trol ol Valv Valve e Upg Upgra rade des s Turb Turbin ine e Cont Contro roll Syst System em Mod Moder erni niza zati tion on Generator Im Improvements
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Steam Path Improvements • More More than than 20 unit units s in in pla plan n for for upgr upgrad ade e • Efficiency gain – Aerodynamic blade profiles – Improved inter-stage sealing sea ling – Reduction of sidewall secondary flow losses
• Reduc ductio tion in in fu futur ture O& O&M co costs sts – Extend time between overhauls – Reduction of solid particle erosion damage da mage – Less coal burned 3
Glen Lyn 6 Series 235MW (GE) HP/IP
Nine (9) Units (Subcritical, 1957 - 1961) • • • • • • • •
Integral control valve chest girth weld creep Purchased complete spare in 1990 Exchanged on other 8 units (1991 – 2004) New rotors – replaced “C” grade materials New nozzles, diaphragms (Rows 1,9,10,12) Reassemble non-outage; 4-week reduction Cost = $8 Million (US) first unit installed, approx. Cost = $4 Million (US) subsequent units, approx. 4
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Glen Lyn 6 Series 235MW (GE) HP/IP 9 Results 9 Restored CV chest with improved girth weld 9 Improved HP efficiency by 1.5% - 2.0% 9 2.5 MW and 35.28 kcal/kWh (140 Btu/kWh) gain 9 Erosion minimized, reduced repairs 9 Extended inspection intervals to 10-11 years 9 Re-inspections begun in 2001 confirm benefit
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1300 MW Series (Alstom) HP
Six (6) Units (Supercritical, 1973 – 1989) • • • • •
Use of spare rotor/inner casing assembly Replaced all stationary/rotating rows (28) Reuse rotor and re-round inner casing Modified seal strips for steam swirl stability Cost = $6 Million (US) per unit installed, approx.
9 Results 9 Blading
Efficiency > 92.0%, increase of 4.7% 9 20 MW and 28.5 kcal/kWh (113Btu/kWh) 9 Improved rotor stability against steam swirl 9 3 Units completed - - 1 with premature degradation 7
600,800 MW Series (GE) HP/IP
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Eight (8) Units (Supercritical, 1967 – 1972) • To date, four have been converted • New nozzles, diaphragms, seals • Reblade spare rotor; reuse shells • Cost = $6.5 Million (US) per unit installed, approx. Results 9 82.8% - 86.3% HP section efficiency 9 11MW gained on 800MW Series 600 MW Series HP fell short of expectations by up to 3.5% due to overstated recoverable losses by OEM. 8
Effect of Advanced Design Steam Path
Efficiency Degradation of HP Turbines 88 86 84
ML#2 BS#2 CD#1
y c n 82 e i c i f 80 f E
MR#5
ADSP Original Design Normal Overhaul
BS #2
78 76 74 0
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4
6
8
10
12
Time (Years)
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Big Sandy Unit 1 HP-IP/SFLP
One (1) unit, W design (Subcritical, 1963) • HP turbine complete and IP/SFLP turbine rotor and inner casing – install 2008 • Inefficient original design • Internal components subjected to erosion and distortion • Creep damage evident • No spare blade rings or rotors
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Original Design Issues Efficiency Turn-around
Curtis Stage
(Pressure Loss)
(Poor Efficiency)
Conventional Cylindrical Airfoil (Poor Efficiency) 11
Existing Maintenance Issues Reliability
Large Dia. Inner Casing (CrMo casting) (Distortion, Rubbing)
L-0 Shrunk-on Disc (SCC Potential)
Stage 1 Blade Root Distortion Stages 2-4 Blade Untwist
IP/SFLP Rotor 44 years Old
L-0 Blade Fatigue Life (Blade Failure)
Large Blade Ring (Distortion, Rubbing, Blade Leaning)
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New HP Section Design ACC Packing (Active Clearance Control)
Integral Inner Casing
Separately supported blade rings and balancing ring
Monoblock No Bore Rotor Rateau control stage
3-D Reaction Blades (ISB) 13
New IP/LP Section Design 25in ISB
ACC Packing (Active Clearance Control)
Mono block no bore rotor No Shrink-fit
Integral Inner Casing
Separately-Supported Blade Rings
3-D Reaction Blades (ISB) 14
Big Sandy Unit 1 Expectations 9 Anticipated
Results
– Improved reliability and design efficiency – HP efficiency +4.1% to 88.9% – IP efficiency +3.1% to 94.6% – Expect +18 MW at original design steam flow – Includes replacement throttle/governor valves – Installed cost $18Million (US), approx.
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LP Turbine Performance Retrofits • AEP experience driven by reliability issues • Stress Corrosion Cracking on blades, disks and Low Cycle Fatigue on blade attachments • Flow limit for L-1 rotating blade causes curtailment • LP turbine exhaust limit = 140 mm HgA (5.5 in HgA) • Frequently caused summer time curtailments
Solution = LP Turbine Upgrade
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LP Turbine Performance Retrofits • Four (4) BB73 W LP steam paths “ruggedized” • Improved material properties to resist SCC and LCF • Aerodynamic improvements to blades and inlet / exhaust flow guides • Improved seal design to reduce leakage • Full load capable to 203 mm HgA (8 in HgA) backpressure 9
Improved performance: 3.4MW, 22.4 kcal/kWh (89 Btu/kWh) 17
Stop/Control Valve Upgrades • Material Damage – Thermal fatigue, creep
• Reliability – Tight shutoff, leaks
• Maintenance – Weld repair to valve body, seats, bolt holes
• Design Improvement – Improve O&M – Reduce pressure drop
1 3 0 0 M W SV C V U p g r a d e
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1300 MW Series SV/CV Upgrades • Original Design – Pressure drop across combined valves = 5.1% – Limited steam flow at VWO + 5% overpressure – Significant solid particle erosion damage – Expensive repairs performed every 2-3 years
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1300 MW Series SV/CV Upgrades • New Design – Separate stop and control valve chambers – Actual pressure drop across valves = 2.08% – Achieved 32 MW increased generation capability without changing boiler conditions – Updating valve actuators to digital controls
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Turbine Control System Upgrades • • • • •
Converting original MH and analog EH controls to digital Integrated into plant Distributed Control System Reuse or modify hydraulic systems Use fire resistant fluids Expectations – Enhanced control – Fewer unit trips – Faster startup/ramp rates – Online testing of turbine valves and protective devices
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Turbine Control System Upgrades 9 Results 9 Smooth,
rapid rollups to synchronous speed 9 CV position and load ramping optimized by stress probe 9 CV stroke ramped according to test throttle pressure 9 Improved reliability during protective device checks 9 Lower peak speeds reached during turbine trip 9 Reduction in boiler tube leaks due to “soft” trips All contribute to improved reliability and performance 24
Generator Improvements • Inspection Intervals (typical) – Field in-place ( 5 years) – Field removed (10 years) – Perform routine cleaning, testing, repairs 9Goal: Achieve high reliability through design life of insulation systems
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Generator Rewinds • Rewinds Offer Opportunity for Improvement – Required for reliability and maintenance purposes – Efficiency improvements are small added benefit
• Stator Windings – Asphalt stator bar insulation replaced with modern epoxy-mica insulation – Potential for increased copper cross-section in original slots – Improved cooling gas or water flows reduce operating temperature and extend design life
• Stator Cores – Inspect and test for looseness, hot spots, resonance – Several cores replaced (full, partial) – Reference papers available in Breakout Session 26
Generator Rewinds • Fields – – – –
Replace retaining rings with 18Mn 18Cr material Improve end turn blocking design and materials Restore/replace copper and replace all insulation Optimize cooling gas flow
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Summary • • • • • • •
AEP has been retrofitting turbine generator equipment with efficiency improvements for more than 15 years. Experience with OEM and non-OEM solutions. Economic benefit drives the HP and IP turbine retrofits. Must consider design improvement vs. restoration improvement. Turbine valve design could provide upgrade potential. Turbine control integration can produce thermal benefits. Reliability benefit drives the LP turbine and generator retrofits (typically). Some small efficiency improvements are possible.
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Breakout Session • Two Sessions on Tuesday Afternoon • Expert Attendees – Steve Molick – Turbine Services Manager – Jim Michalec – Staff Engineer, Generators – Alex Manukian – Sr. Engineer, Turbines – Jim Cable – Sr. Engineer, Turbines, Controls – Dan Sculley – TG&PSE Manager
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