Details of a Steam Path Audit Paul Roediger Encotech, Inc.

Overview of Presentation: Audit Overview Benefits Chronology Measurements Calculations Results / Report Conclusion

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

Benefits OPENING AUDIT Identification of degradation Cost-effective maintenance actions CLOSING AUDIT Quality check on maintenance performed during the outage Performance improvement resulting from individual maintenance actions Expected return-to-service performance

Required Resources Computer Loss Calculation Software One or Two Auditors Measurement Tools Radial Packing Gauge 6” Digital Caliper Tape measure Ball Gauges Surface Roughness Comparator

Maintenance Action Items for B/C > 3.5

Maintenance Action Items for B/C < 3.5

Chronology Model On Site Analysis / Report

Model Create model using the Thermal Kit Design heat balance (VWO) Turbine cross section Clearance and steam seal diagram First stage shell pressure curve

SPA On-Site Time-Line Disassembly Reassembly

Measurements Geometry Clearances Surface roughness Damage Solid Particle Erosion Throat Openings Steam 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 joint Measure Stationary Blade Geometry Measure top half tooth heights Measure packing clearances Inspect shell sealing surfaces

On Site - Day 2 Rotor Removed Measure solid particle erosion damage Measure deposit thickness Measure stationary and rotating blading surface roughness Inspect for mechanical damage

On Site - Day 3 Measure bottom half tooth heights Measure trailing edge thickness Measure turbine geometry Inspect snout rings

Analysis / Preliminary Report Input data & analysis Print Steam Path Audit reports Give 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 W = Flow (lb/h) K = Packing type constant C = Rubbed coefficient A = 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

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

Dollar Value of Heat Rate Degradation (Based on G.T.H.R.) FC = Cost of fuel $/million BTU’s GR = Rating of turbine in KW CF = Turbine capacity factor in % 8760 = Hours in a Year BE = Boiler Efficiency = $8,012.20 / year

Annual Fuel Savings - $ Year R - Rating of turbine in KW CF - Turbine capacity factor in % F - Cost of fuel $/million BTU’s HR - Change in heat rate in % SHR - Station heat rate BTU’s/KW HR Example: = $650,430/year

Cost of Lost Capacity Where: L = lost revenue $/year K = percentage of year at max. capacity (%) M = average wholesale price of power ($/(MWh)) R = unit capacity (kW) D = degradation in performance (%) For: K = 50% M = 45 $/(MWh) R = 600,000 kW D = 1% L = 1,182,600 $/year

Results OPENING AUDIT Quantification of losses measured in pre-outage test Listed cost-effective maintenance actions CLOSING AUDIT Quality check on maintenance performed during the outage Performance improvement resulting from individual maintenance actions Expected return-to-service performance

Opening Audit Loss Heat Rate Loss by Category

Opening Audit Loss Heat Rate Loss by Casing

Opening Audit: Summary

HP Casing - Loss Summary

HP Casing – Tip Spill Strips Opening Audit

HP Casing – Tip Spill Strips Closing Audit

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

Economic Assumptions

Conclusion Usually not everything is worth replacing or repairing The Opening Audit will identify degradation and B/C ratio The Closing Audit will quantify the expected recovery The audit results should be reconciled with the enthalpy drop tests.

Conclusion It 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.

Questions? 1-888-Encotech ((518) 374-0924)