turbine generator upgrades & maintenance

8/8/2019 Turbine Generator Upgrades & Maintenance

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Presented by:

Daniel Sculley, Manager

Turbine, Generator & Piping

Systems Engineering

APP Site Visit

October 30 ± November 4, 2006

Turbine/Generator

Upgrades andMaintenance

Turbine/Generator

Upgrades andMaintenance



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Topics

Turbine Blading & Steam Path Upgrades

Turbine Stop / Control Valve Upgrades

Turbine Control System Modernization Generator Improvements



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Steam Path Improvements

More than 20 units in plan for upgrade

Efficiency gain ± Aerodynamic blade profiles

± Improved inter-stage sealing

± Reduction of sidewall secondary flow losses

Reduction in future O&M costs

± Extend time between overhauls ± Reduction of solid particle erosion damage

± Less coal burned



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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 ³C´ 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.



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Glen Lyn 6 Series 235MW (GE) HP/IP

ResultsRestored CV chest with improved girth weld

Improved HP efficiency by 1.5% - 2.0%

2.5 MW and 35.28 kcal/kWh (140 Btu/kWh) gain

Erosion minimized, reduced repairs

Extended inspection intervals to 10-11 years

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.

Results

Blading Efficiency > 92.0%, increase of 4.7%20 MW and 28.5 kcal/kWh (113Btu/kWh)

Improved rotor stability against steam swirl

3 Units completed - - 1 with premature degradation



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600,800 MW Series (GE) HP/IP

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

82.8% - 86.3% HP section efficiency

11MW gained on 800MW Series

600 MW Series HP fell short of expectations by up to3.5% due to overstated recoverable losses by OEM.



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Effect of Advanced Design Steam Path

Effi i i f HP i

BS #

#BS#

D#

#5

74

7

7

4

4

i (Y )

E f f i

i ADSPigina Design

o ma ve ha



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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 andinner 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

EfficiencyTurn-around

Pressure Loss

Curtis Stage

Poor E iciency

Conventional Cylindrical Air oil

Poor E iciency



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Existing Maintenance Issues

Reliability

Large Blade Ring

Distortion, Rubbing,

Blade Leaning

L-0 Blade Fatigue Li e

Blade Failure

L-0 Shrunk-on Disc

SCC Potential

Large Dia. Inner Casing CrMo casting

Distortion, Rubbing

Stage 1 Blade Root Distortion

Stages 2-4 Blade Untwist

IP/SFLP Rotor

44 years Old



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New HP Section Design

Monoblock

No Bore Rotor

Separately supportedblade rings andbalancing ring

3-D Reaction Blades

ISB

ACC PackingActive Clearance Control

Integral Inner Casing

Rateau control stage



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New IP/LP Section Design

ACC PackingActive Clearance Control

Mono block no borerotor

No Shrink- it

Separately-SupportedBlade Rings

3-D Reaction Blades

ISBIntegral Inner Casing

25in ISB



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Big Sandy Unit 1 Expectations

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 LowCycle 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 ³ruggedized´

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

Improved performance: 3.4MW, 22.4 kcal/kWh (89Btu/kWh)



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Stop/Control Valve Upgrades

Material Damage ± Thermal fatigue, creep

Reliability

± Tight shutoff, leaks Maintenance

± Weld repair to valvebody, seats, bolt holes

Design Improvement ± Improve O&M

± Reduce pressure drop

1 3 0 0 M W r



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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 particleerosion damage

± Expensive repairsperformed every 2-3 years



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1300 MW Series SV/CV Upgrades

New Design ± Separate stop and control

valve chambers

± Actual pressure dropacross valves = 2.08%

± Achieved 32 MW increasedgeneration capabilitywithout changing boiler conditions

± Updating valve actuators todigital 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

Results

Smooth, rapid rollups to synchronous speed

CV position and load ramping optimized by stress

probeCV stroke ramped according to test throttle pressure

Improved reliability during protective device checks

Lower peak speeds reached during turbine trip

Reduction in boiler tube leaks due to ³soft´ trips

All contribute to improved reliability and performance



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Generator Improvements

Inspection Intervals (typical)

± Field in-place ( 5 years)

± Field removed (10 years) ± Perform routine cleaning, testing, repairs

Goal: Achieve high reliability through designlife 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 operatingtemperature 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



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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 withefficiency 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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Questions

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