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

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

3. 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

4. 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

5. 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

6. 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

7. Maintenance Action Items for B/C > 3.5

8. Maintenance Action Items for B/C < 3.5

9. Chronology
Model
On Site
Analysis / Report

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

11. SPA On-Site Time-Line
Disassembly
Reassembly

12. Measurements Geometry Clearances Surface roughness Damage
Solid Particle Erosion
Throat Openings
Steam Path Length

13. Clearance Measurements

14. What Tooth Throttles Steam?

15. Slant Tooth Packing

16. Honeycomb Packing

17. Mechanical Damage

18. Solid Particle Erosion

19. Throat Opening Measurements

20. Ball Gauge Measurement

21. Surface Roughness Measurement

22. Miscellaneous Leakage Measurements

23. Cover Deposits

24. Nozzle Repair

25. 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

26. 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

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

28. Analysis / Preliminary Report
Input data & analysis
Print Steam Path Audit reports
Give preliminary presentation on site

29. Calculations Martin’s Formula General Flow Equation
Dollar Value of Heat Rate
Annual Fuel Cost Savings
Cost of Lost Capacity

30. Martin’s Formula Calculation

31. 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)
= Unit conversion constant

32. Common Tooth Types

33. 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 ( ) = 8.03 kW/mil

34. 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, / year

35. 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

36. 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

37. 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

40. Opening Audit Loss Heat Rate Loss by Category

41. Opening Audit Loss Heat Rate Loss by Casing

42. Opening Audit: Summary

43. HP Casing - Loss Summary

44. HP Casing – Tip Spill Strips Opening Audit

45. HP Casing – Tip Spill Strips Closing Audit

46. Tip Spill Strips - Opening Audit

47. Tip Spill Strips - Opening Audit

48. Tip Spill Strips - Closing Audit

49. Tip Spill Strips - Opening Audit

50. HP - Repair or Replacement Cost

51. Economic Assumptions

52. 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.

53. 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.

54. Questions?
1-888-Encotech
((518) )