1. Russia Power 2010
Turbo Services
Maintenance of V94.0/V94.2 series of gas turbines
Dr Shaun West and Sjef Mattheij MSc, Sulzer Turbo Services
| slide 1

2. Contents
Turbo Services
 Background
 Component life analysis

Corrosion and oxidation

Material degradation

Creep

Fretting

Fatigue
 Rotor life management
 The manufacture of gas turbine blades
 Summary
| slide 2

3. Sulzer Turbo Services’ experience
- over 15 years of know how developed
Turbo Services
V94.2 series
Total V-series
Combustion component repairs (burners,
star plates, mixing chambers, hot gas
casings)
50 sets of parts
76 sets of parts
Blade and vane repairs
672 sets of parts
1485 sets of parts
16 inspections
28 inspections
35 projects
56 projects
37 sets of parts
93 sets of parts
10 units
11 units
Field services
(mechanical, controls, fact finding, minor and
major inspections)
Rotor services
(de-stacking, inspection, restacking,
balancing, NDT, life assessment)
New and replacement parts (consumables,
combustion section, turbine section)
Long-term service agreements
| slide 3

4. 15 years of component repair experience
- development of proprietary know how
Turbo Services
 Repair experience starting in the 1990s

Compressor section

Burners

Flame tubes

Hot gas casings

Power turbine
 Build up of proprietary know how

Based on earlier and later V-series units

Based on repairs of gas turbines of other
OEMs

Based on operator feedback
| slide 4

5. 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

IGA

NDT

Welding

Overlay repair by slurry-brazing

Blending

Heat treatment

Coating (where applicable)
 Sulzer inspection techniques

X-ray

Boroscope inspections

Thermographic analyses
| slide 5

6. 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

Welding

Overlay repair by slurry-brazing

Blending

Heat treatment

Coating (where applicable)
 Sulzer inspection techniques



X-ray inspection
Visual inspection of internals
Dimensional inspection: tooling
| slide 6

7. Repair of combustion parts
- metallurgical understanding key to repairs
 Known operational issues
Turbo Services
 Repair processes

Nitration of IN617

Assessment of damage

Fatigue cracking

Restoration of shape

Distortion/overheating

Solution heat treatment

Removal of damaged areas
 Sulzer inspection techniques

Visual inspection

Repair and replacement of damaged parts

Dimensional inspection: tooling

Stress relieve heat treatment

Metallurgical inspections

Thermal Barrier Coating application

Hard facing and assembly of auxiliaries
| slide 7

8. 2001 the first major overhaul
- planning and know how key to success
Turbo Services
 Scope

Site works (fact finders, QA, site management, technical advisors…)

Rotor removal, de-stack, re-stack and balancing

All blades and vanes repaired

Replacement of consumables
 Challenges

Unit has been build within existing power plant

Unit was an early .0 version
| slide 8

9. Inspection challenges
- rotor line out is a critical issue
Turbo Services
 Correct procedures are required
 Attention to x, y and z direction (more
than with annular combustors
 Correct tolerances on repair mixing
chambers and HGC
Know how is key to success
| slide 9

10. 10 years experience with replacement parts
- new parts based on repair experiences
Turbo Services
 Special tooling critical for the component
repair
 Experience based on repair and manufacture
of many different silo combustion systems
 Weld procedures important to maintain
dimensional integrity
| slide 10

11. Contents
Turbo Services
 Background
 Component life analysis

Corrosion and oxidation

Material degradation

Creep

Fretting

Fatigue
 Rotor life management
 The manufacture of gas turbine blades
 Summary
| slide 11

12. Corrosion and oxidation
- three different damage mechanisms
Cr 2 O 3
Protective layer
Turbo Services
TBC
Al 2 O 3
Inter-diffusion
Thermo mechanical fatigue
Attack
Type II
Hot Corrosion
500
600
Type II
Type
Hot Corrosion
700
800
Temperature (°C)
900
Oxidation
1000
1100
| slide 12

13. Material degradation
- material strength reduces over time
Material Degradation
 Gamma prime strengthens super
Dissolution and growth of γ’- precipitates
alloys
Turbo Services
 Heat treatments can restore the
Sulzer Turbo Services
structure
 Time at high temperature causes
Gamma Prime Size / Temperature distribution
rounding of the crystals
LE
CC
CV
TE
TIP
MIDDLE
ROOT
γ’ precipitate size changes with time & temperature
| slide 11
| slide 13

14. Creep
- Creep damage cannot be recovered
Turbo Services
 Slow deformation at constant stress
level at high temperatures ( T >
0.4Tm )
 Material properties are important, like
grain size and volume of γ’precipitates
 Creep is a thermally activated
 Strain rate increase with stress and
temperature
 Life time reduces with increase in
stress and temperature
| slide 14

15. Fretting
- damage minimization is key
Turbo Services
 Material removal as a result of sliding wear

Contact between to surfaces

Vibration
 Transition pieces

Seals

Mounting brackets
 Wear resistant coatings or linings are
usually efficient (W-Cr carbides, Stellites)
| slide 15

16. 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
∆σ [MPa]
LCF
Fatigue limit
HCF
100
1000
10000
100000
1000000 10000000
Number of cycles [#]
| slide 16

17. 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 17

18. Low cycle fatigue
- start/stop related
Turbo Services
IN939 vanes suffering LCF following imbrittlement of the base material
| slide 18

19. Contents
Turbo Services
 Background
 Component life analysis

Corrosion and oxidation

Material degradation

Creep

Fretting

Fatigue
 Rotor life management
 The manufacture of gas turbine blades
 Summary
| slide 19

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
Example of FEA on rotor disk
| slide 20

21. Contents
Turbo Services
 Background
 Component life analysis

Corrosion and oxidation

Material degradation

Creep

Fretting

Fatigue
 Rotor life management
 The manufacture of gas turbine blades
 Summary
| slide 21

22. The manufacture of gas turbine blades
- over 35 years of experience
Turbo Services
 Reverse engineering started in 1980s

Supporting Russian gas pumping units

Many different designs for different units
 Key processes

Measurements
(parts and fit with adjacent parts)

Understanding the design intent

3D-CAD drawings

Casting

Machining
| slide 22

23. Contents
Turbo Services
 Background
 Component life analysis

Corrosion and oxidation

Material degradation

Creep

Fretting

Fatigue
 Rotor life management
 The manufacture of gas turbine blades
 Summary
| slide 23

24. Summary
- driving towards improved performance
Turbo Services
Condition based maintenance supported by Sulzer can:
 Extend operational life
 Have a positive impact on total maintenance costs
 Helps to allow informed decisions concerning ‘repair’ or ‘replace’
 Provide the necessary information on critical components to manage component
life, turbine life and inspection intervals.
C&I sites services


Trouble shooting / hot line / remote condition monitoring

Compressor


Mechanical site services
Planned and
unplanned
maintenance
Parts
Blades and vanes
Combustion system
Repairs
LTSAs
Rotor
Component




| slide 24

25. Turbo Services
| slide 25