Reducing costs with condition based maintenance, IBC conference Singapore, 2010


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This paper described how costs of gas turbine ownership can be reduced based on input of condition based maintenance. Innovative thinking is required coupled with risk management.

Published in: Business, Technology

Reducing costs with condition based maintenance, IBC conference Singapore, 2010

  1. 1. Turbo Services Reducing Costs with Condition Based Maintenance Dr Shaun West and Nathan Self, Sulzer Turbo Services | slide 1
  2. 2. Sulzer Turbo Services’ experience - over 15 years of know how developed Turbo Services Frame 9E/9FA 7E/7FA Total V-series +100 sets of parts +75 sets of parts + 1500 sets of parts +1400 sets of parts + 100 inspections +25 inspections Rotor services (de-stacking, inspection, restacking, balancing, NDT, life assessment) +50 +50 projects New and replacement parts (consumables, combustion section, turbine section) +100 sets +90 sets of parts 20units 11 units Combustion component repairs Blade and vane repairs Field services (mechanical, controls, fact finding, minor and major inspections) Long-term service agreements | slide 2
  3. 3. Gas turbine segment trends - what is ‘mature’ technology today? Turbo Services G and H technologies are still maturing F-tech was first introduced 15 years ago Improvements keep being introduced to the F-tech units Most gas turbines can now be considered ‘mature’ Frame 5 Frame 7B Year of introduction Frame 9E Frame 7E Frame 6B Frame 9B V93 and Frame 7FA Frame 9FA GE V94.3a V94.2 Capacity installed in calendar year Siemens 13E2 GT13D 13E GT24 Alstom GT26 WH501D WH251B 1970 Platts, 2007 1975 1980 WH501F WH701D WH/MHI WH701F 1985 1990 1995 2000 2005 2010 | slide 3
  4. 4. How can risks and costs be controlled? - an LTSA is not for everyone Turbo Services Costs can be ‘high’ LTSAs with the manufacturer Management of technology risk for introductory technologies Can be ridged in structure Extra works normally at ‘list price’ Service delivery is more flexible Suitable for mature technologies LTSAs with a non-OEM Good tool to limit price risks Extra works normally at agreed rates Life management possibilities Management and logistics can be an issue Transactional services Costs can be lower – all technical risk remaines with the buyer Life management possibilities | slide 4
  5. 5. Sweating the asset - where can the most value be created? Turbo Services Where can additional value safely be extracted? Parts costs Repair costs Cost saving creates value Field service TA costs Field service craft labour Parts’ life extension Extension of inspection intervals Engineering judgment adds value Upgrading of capability | slide 5
  6. 6. Driving cost savings to create value Turbo Services Good procurement driving costs out Cost saving of 10% on repairs Cost saving of 10% on CI field services CI/CI/HGP/CI/CI/MI cycle What is the cost saving? Six day outage Repair costs Cost per CI 100,000USD 200,000USD 2 MI cycle (12 years) 40,000 80,000 120,000 The unit is not put at risk directly… … risk of poor outage performance … risk of poor repair life | slide 6
  7. 7. Value creation from engineering judgment Turbo Services Using engineering know how to create value Removal of combustion inspection CI/CI/HGP/CI/CI/MI cycle What is the value created? Six day outage Repair costs Generation gains Cost per CI 2 MI cycle (12 years) 100,000USD 800,000 200,000USD 1,600,000 100MWx24hx6dx25USD/MWh 360,000USD 2,880,000 5,280,000 This example is based on no additional repair costs! A little unrealistic as repairs on the combustion capitals may be more extensive The key is how to do this without putting the unit at risk… | slide 7
  8. 8. Turbo Services Key know how… … how do parts degrade | slide 8
  9. 9. Corrosion and oxidation - three different damage mechanisms Cr2O3 Turbo Services TBC Al2O3 Protective layer Inter-diffusion Thermo mechanical fatigue Attack Type II Hot Corrosion 500 600 Type I Type I Hot Corrosion 700 800 Temperature (°C) 900 Oxidation 1000 1100 | slide 9
  10. 10. Material degradation - material strength reduces over time Gamma prime strengthens super alloys Turbo Services Heat treatments can restore the structure Time at high temperature causes rounding of the crystals LE CC CV TE TIP MIDDLE ROOT γ’ precipitate size changes with time & temperature | slide 10
  11. 11. Creep - Creep damage cannot be recovered Turbo Services Material properties are important, like grain size and volume of γ’precipitates Strain [-] Slow deformation at constant stress level at high temperatures ( T > 0.4Tm ) Creep is a thermally activated process Strain rate increase with stress and temperature Life time reduces with increase in stress and temperature | slide 11
  12. 12. Fretting - damage minimization is key Turbo Services What: material removal as a result of sliding wear Contact between two surfaces Vibration Where: transition pieces Seals Mounting brackets Fix: wear resistant coatings or linings are usually efficient (W-Cr carbides, Stellites) | slide 12
  13. 13. Cyclic fatigue - regular visual inspections are important High cycle fatigue Turbo Services Low cycle fatigue Large number of cycles until failure (>100,000 cycles) Low number of cycles until failure (<100,000 cycles) Crack initiation can take a long time Crack initiation period relatively short Required stress amplitude is relatively low Stress amplitude is high Vibration can be caused by: Tip rubbing Resonance Aerodynamic instabilities Δσ [MPa] LCF Fatigue limit HCF 100 1000 10000 100000 1000000 10000000 Number of cycles [#] | slide 13
  14. 14. High cycle fatigue - catastrophic compressor failure Turbo Services Excitation caused by: single VIGV closing, blade rub etc Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 | slide 14
  15. 15. Low cycle fatigue - start/stop related Turbo Services IN939 vanes suffering LCF following imbrittlement of the base material | slide 15
  16. 16. Repair of blades - metallurgical understanding key to repairs Known operational issues Turbo Services Repair processes IN 738/Sicoat 2231 Striping of coating Cracking leading edges (row 1) Heat treatment Inter-granular attack NDT Sulzer inspection techniques Welding X-ray Overlay repair by slurry-brazing Boroscope inspections Blending Thermographic analyses Heat treatment Coating (where applicable) Sections used for creep testing #14844 #14843 #14847 #14845 #14837 #14846 #14842 | slide 16
  17. 17. Repair of vanes - metallurgical understanding key to repairs Known operational issues Turbo Services Repair processes Nitration of IN 939 Striping of coating Fatigue cracking Heat treatment Distortion NDT Sulzer inspection techniques Welding X-ray inspection Overlay repair by slurry-brazing Visual inspection of internals Blending Dimensional inspection: tooling Heat treatment Coating (where applicable) | slide 17
  18. 18. Turbo Services Case Studies | slide 18
  19. 19. Blade re-design to meet a customer’s needs A customer found that their blades were failing early in life due to a deformation on the shroud of the turbine blades Turbo Services Original with shroud Working with the customer and their insurance company, a tailor-made solution was developed The new design has proven itself in operation The new design provides lower operational risk because the deformation no longer plagues the machine Modified without shroud Major cost saving: 24kEOH parts now lasting 24k+24kEOH | slide 19
  20. 20. Rotor life management - extending operation safely Turbo Services Rotor material can become brittle Replica and phased array NDT are two assessment tools Rotor operational history important Rotors can suffer low cycle fatigue Finite element modeling provides stress data Some damage can be repaired/replaced Major cost saving: A new rotor can cost 5M USD An unplanned failure will cost the owner and insurer +10M USD each Example of FEA on rotor disk | slide 20
  21. 21. Damaged turbine stub shaft - repaired and fit for service Turbo Services Emergency shut down damaged turbine stub shaft Stub shaft was machined, welded and then machined to original dimensions Rotor rebuilt and put back into operation Speed was key for the owner Major cost saving: Rotor returned to service within 30 days | slide 21
  22. 22. Extending outages - removing an unplanned 8000EOH inspection Turbo Services Review of the weak parts of the turbine Upgrades on the weakest areas Flow down of advanced technologies Transfer of technologies used on other units Understanding of the full hot gas path FE analysis Temperature mapping CFD Modes of degradation Own (S West) experience Burner segment plates – early failure Weaknesses from fretting and overheating Solution – low risk, based on coatings | slide 22
  23. 23. Frame 9FA compressor - strip, replace, rebuild of the compressor Turbo Services Reverse engineering Determination of natural frequencies 3D scanning Physical component Finite element measurement Computational fluid dynamics 3D solid model Over 20 F-tech rotors | slide 23
  24. 24. Making run/no-run decisions - I am stuck in the middle… Turbo Services Engineering judgment helps you to make better decisions Helps to create value and save cost ‘We need to have a decision - NOW!’ ‘What’s the risk of running on?’ ‘There are high prices available - we’re losing opportunity’ ‘I don’t want to know the technical details..’ ‘How long can we run safely for?’ ‘How long will it take to fix and how much will it cost’ | slide 24
  25. 25. Turbo Services | slide 25