Details of aSteam Path Audit

Paul RoedigerEncotech, Inc.

Overview of Presentation:

Audit OverviewBenefitsChronologyMeasurementsCalculationsResults / ReportConclusion

Audit Overview :

Inspection of the steam path(Comparison to new & clean conditions)

Results: clear priority for maintenance decisions

Benefit: maintenance dollars used with the highest return

Verification of maintenance

Overview:

What: Inspection of the steam path (determined by VWO heat balance conditions)

When: Immediately after steam path is exposed and again after maintenance has been performed

BenefitsOPENING AUDITIdentification of degradationCost-effective maintenance actions

CLOSING AUDITQuality check on maintenance performed during the outagePerformance improvement resulting from individual maintenance actionsExpected return-to-service performance

Required ResourcesComputerLoss Calculation SoftwareOne or Two AuditorsMeasurement Tools

Radial Packing Gauge6” Digital CaliperTape measureBall GaugesSurface Roughness Comparator

Maintenance Action Itemsfor B/C > 3.5

Heat Rate Heat Rate Benefit Benefit Repair cost Action Item (Btu/kWh) ($1,000) ($1,000) Benefit/Cost ______________________________________________________________________________ Sharpen HP stg 6 interstage packing 3.1 9.3 0.3 31.0 Sharpen HP stg 4 interstage packing 2.8 8.4 0.3 28.0 Sharpen HP stg 5 interstage packing 2.6 7.8 0.3 25.0 Sharpen HP stg 2 interstage packing 2.5 7.5 0.3 25.0 Sharpen HP stg 3-6 interstage packing 7.0 21.0 1.2 17.5 Replace IP stg 1 tip spill strip 13.0 39.0 4.0 9.8 Polish HP nozzles 13.0 39.0 4.0 9.8 Replace IP stg 2 tip spill strips 9.0 27.0 4.0 6.8 Polish IP nozzles, exhaust side 8.0 24.0 4.0 6.0 Second reheat stage minor repairs 10.0 30.0 8.0 3.8 Replace top half snout rings 23.0 69.0 19.0 3.6 ______________________________________________________________________________

Maintenance Action Itemsfor B/C < 3.5

Sharpen stg 1 tip spill strip 0.3 0.9 0.3 3.0 Replace IP stg 3-6 tip spill strips 12.0 36.0 16.0 2.3 Sharpen stg 2 tip spill strip 0.2 0.6 0.3 2.0 Replace stg 2 interstage packing 4.0 12.0 7.5 1.6 Replace stg 6 interstage packing 3.5 10.5 7.5 1.4 Polish LP Nozzles, exhaust side 3.0 9.0 7.0 1.3 Replace stg 4 interstage packing 3.0 9.0 7.5 1.2 Replace stg 5 interstage packing 3.0 9.0 7.5 1.2 Second reheat stage major repairs 15.0 45.0 55.0 0.8 Replace bottom half snout rings 2.0 6.0 19.0 0.3 ______________________________________________________________________________ Total repair cost for B/C >3.5 45.4 Total repair cost for B/C < 3.5 127.6

Chronology

Model

On Site

Analysis / Report

Model

Create model using the Thermal Kit

Design heat balance (VWO)Turbine cross sectionClearance and steam seal diagramFirst stage shell pressure curve

SPA On-Site Time-Line

TURBINE O UTAG E

S h u t d ow n S t a rt u p

Pre-Outage Test Opening SteamPath A udit

Closing SteamPath A udit

Upgrade andMaintenanc e

Pos t-OutageTes t

Disassembly Reassembly

Measurements

GeometryClearancesSurface roughnessDamage

Solid Particle ErosionThroat OpeningsSteam Path Length

Clearance Measurements

What Tooth Throttles Steam?

Slant Tooth Packing

Honeycomb Packing

Mechanical Damage

Solid Particle Erosion

Throat Opening Measurements

Ball Gauge Measurement

Surface Roughness Measurement

Miscellaneous Leakage Measurements

Cover Deposits

Nozzle Repair

On Site - Day 1

After Top is Lifted

Inspect horizontal jointMeasure Stationary Blade GeometryMeasure top half tooth heightsMeasure packing clearancesInspect shell sealing surfaces

On Site - Day 2Rotor Removed

Measure solid particle erosion damageMeasure deposit thicknessMeasure stationary and rotating blading surface roughnessInspect for mechanical damage

On Site - Day 3

Measure bottom half tooth heightsMeasure trailing edge thicknessMeasure turbine geometryInspect snout rings

Analysis / Preliminary Report

Input data & analysisPrint Steam Path Audit reportsGive preliminary presentation on

site

Calculations

Martin’s Formula

General Flow Equation

Dollar Value of Heat Rate

Annual Fuel Cost Savings

Cost of Lost Capacity

Martin’s Formula Calculation

General Flow Equation

k

k

k

p

p

p

p

k

k

v

pKCAW

1

1

2

2

1

2

1

1 11

*5.2406

W = Flow (lb/h)K = Packing type constantC = Rubbed coefficientA = Area (sq in.)P1 = Upstream Pressure (psia)v1 = Upstream specific volume (ft 3/lb) P2 = Downstream Pressure (psia)k = Isentropic exponent (1.3 typical)2406.5 = Unit conversion constant

Common Tooth Types

coefficient:2 TEETH: 0.403 TEETH: 0.334 TEETH: 0.295 TEETH: 0.26

SINGLE – AXIALFlow Equation

coefficient: 0.57

ROTATINGBLADE

STATIONARYBLADE

SINGLE – RADIALFlow Equation

coefficient: 0.57

DOUBLE STRAIGHTFlow Equation

coefficient: 0.70

TWO SINGLEFlow Equation

coefficient: 0.46

DOUBLE & SINGLEFlow Equation

coefficient: 0.52

STEPFlow Equation

TIP SPILL STRIP CLEARANCE

Ken Cotton Chart – Reference Table [449]

kW loss per mil excess clearance per stage:7+ ((591.9 – 500) / (500 – 100)) x (7.0 -2.5) = 8.03 kW/mil

][ )t(C)tC(GAP L+L+R+R2

1=ave

C GAPave =1

8ave

ti

i 1

8

1-34

Dollar Value of Heat Rate Degradation(Based on G.T.H.R.)

610*

8760***

BE

CFGRFCHRDV

FC = Cost of fuel $/million BTU’sGR = Rating of turbine in KWCF = Turbine capacity factor in %8760 = Hours in a YearBE = Boiler Efficiency

000,000,1*82

8760*75*000,500*00.2HRDV

= $8,012.20 / year

1-35

Annual Fuel Savings - $ Year

000,000,000,10

*8760**** SHRHRFCFRAFS

R - Rating of turbine in KWCF - Turbine capacity factor in %F - Cost of fuel $/million BTU’sHR - Change in heat rate in %SHR - Station heat rate BTU’s/KW HR

Example:

000,000,000,10

9900*8760*0.1*00.2*75*000,500AFS

= $650,430/year

1-36

Cost of Lost Capacity

710

8760*D*R*M*KL

Where: L = lost revenue $/yearK = percentage of year at max. capacity (%)M = average wholesale price of power ($/(MWh))R = unit capacity (kW)D = degradation in performance (%)

For:K = 50%M = 45 $/(MWh)R = 600,000 kWD = 1%

L = 1,182,600 $/year

ResultsOPENING AUDITQuantification of losses measured in pre-outage testListed cost-effective maintenance actions

CLOSING AUDITQuality check on maintenance performed during the outagePerformance improvement resulting from individual maintenance actionsExpected return-to-service performance

Opening Audit LossHeat Rate Loss by Category

Opening Audit LossHeat Rate Loss by Casing

Opening Audit: Summary Change In Power Loss G.T.H.R. Audit Category kW Btu/kWh Interstage Packings 502.8 19.91 Tip Spill Strips 2333.2 81.87 Shaft End Packings 1166.2 34.44 Steam Seal System Loss 0.0 0.00 Miscellaneous Leakages 33.5 1.76 Flow Path Damages 149.8 4.36 Flow Change Impact 0.0 0.00 Surface Roughness 947.3 40.28 Trailing Edge Thickness 0.0 0.00 Cover Deposits 10.2 0.53 Hand Calculations 0.0 0.00 Turbine Total 5142.9 187.71

HP Casing - Loss Summary Change In Power Loss G.T.H.R. Audit Category kW Btu/kWh Interstage Packings 279.7 8.14 Tip Spill Strips 1787.1 52.55 Shaft End Packings 1096.4 30.73 Miscellaneous Leakages 0.0 0.00 Flow Path Damages 27.0 0.78 Surface Roughness 414.0 12.06 Trailing Edge Thickness 0.0 0.00 Cover Deposits 0.0 0.00 Hand Calculations 0.0 0.00 Total 3604.2 105.92 True Casing Efficiency Change 6.25 % True Casing Efficiency 82.84 % Apparent Casing Efficiency 82.84 %

HP Casing – Tip Spill StripsOpening Audit

Measured Design Eff Power Change In Clearance Wear Loss Loss G.T.H.R. in. in. in. % kW Btu/kWh Stage 1 0.081 0.060 0.021 1.69 84.9 2.47 Stage 2 0.063 0.040 0.023 2.91 127.3 3.70 Stage 3 0.063 0.040 0.023 3.15 143.3 4.17 Stage 4 0.136 0.040 0.096 10.68 505.5 14.74 Stage 5 0.110 0.040 0.070 7.20 352.4 10.26 Stage 6 0.106 0.040 0.066 5.02 258.7 7.53 Stage 7 0.082 0.040 0.042 2.94 159.2 4.63 Stage 8 0.077 0.040 0.037 2.73 155.7 4.53 Total 1787.1 52.55

HP Casing – Tip Spill StripsClosing Audit

Measured Design Eff Power Change In Clearance Wear Loss Loss G.T.H.R. in. in. in. % kW Btu/kWh Stage 1 0.070 0.060 0.010 2.07 104.5 3.04 Stage 2 0.031 0.040 -0.009 -0.97 -42.6 -1.24 Stage 3 0.034 0.040 -0.006 -1.51 -68.6 -1.99 Stage 4 0.029 0.040 -0.011 -1.87 -88.3 -2.57 Stage 5 0.033 0.040 -0.007 -1.37 -65.7 -1.91 Stage 6 0.042 0.040 0.002 0.13 6.8 0.20 Stage 7 0.039 0.040 -0.001 -0.06 -3.3 -0.10 Stage 8 0.087 0.040 0.047 3.90 222.3 6.47 Total 65.1 1.89

Tip Spill Strips - Opening Audit

Tip Spill Strips - Opening Audit

Tip Spill Strips - Closing Audit

Tip Spill Strips - Opening Audit

HP - Repair or Replacement Cost

Interstage Tip Spill Diaphragms / Total Packing Strips Buckets Cost

Stage 1 $3,000.00 $38,648.00 $41,648.00 Stage 2 $14,230.00 $2,915.00 $23,901.00 $41,046.00 Stage 3 $7,115.00 $2,915.00 $22,973.00 $33,003.00 Stage 4 $7,115.00 $3,115.00 $16,110.00 $26,340.00 Stage 5 $7,115.00 $2,415.00 $17,725.00 $27,255.00 Stage 6 $7,115.00 $2,815.00 $14,967.00 $24,897.00 Stage 7 $7,115.00 $1,715.00 $28,462.00 $37,292.00 Total $49,805.00 $18,890.00 $162,786.00 $231,481.00

Economic AssumptionsAssumption

Rating 320,000 kW Cap. =1 Exp. = 0 1

Capacity Factor 30 %

Fuel Cost 3.5 $/ 10 6 Btu

Fuel Cost Escalation 6 %

Discount Rate 12 %

Economic Life 4 Years

Capital Escalation Rate 5 %

Year of Expenditure 1 Year

P.V. Carrying charge 1.34

(from financial Analysis/treasurer)

ConclusionUsually not everything is worth replacing

or repairing The Opening Audit will identify

degradation and B/C ratioThe Closing Audit will quantify the

expected recovery

The audit results should be reconciled with the enthalpy drop tests.

ConclusionIt is a fair question to ask if the

degradation would have been identified and repaired without the use of an audit.

Some would. Some may not. And some repairs may take place that were not really necessary.

1-888-Encotech

((518) 374-0924)

Questions?