Allianz Global Corporate & Specialty
Special Risks for Steam Turbine Operation due to changed energy markets
Stefan Thumm, Dr. Martin Eckel, Dr. Rüdiger Beauvais, 4.11.2013, Munich
© Allianz Global Corporate & Specialty AG, 08.11.2013
2
© Allianz Global Corporate & Specialty AG, 08.11.2013
Claims, Allianz Zentrum für Technik (AZT)and the Allianz Risk Consultants Network (ARC)
Underwriting
RiskManagement Claims
Client
• Common support for underwriters, clients and loss adjusters with pre- and post loss expertise and services.
• ARC Global network of more than 260 engineers, specialists and industry experts.
• AZT services include in-depth failure analysis, failure prevention and evaluation of prototypical technologies
• AZT is an independent service provider within the ARC network. Services are provided to AGCS clientsand independently via the Allianz Risk Consulting GmbH.
AZT
3
“Our perspective on damage and risk”
Wear and Tear
4
“Our perspective on damage and risk”
MultilineInterdisciplinary
OperationConditions
Design
Handling
Material Issues
Wear and Tear
LifetimeConsumption
5
Why the changed energy markets lead tonew risks for steam turbines
Can you mitigate these risks ?
6
Table of contents 1 General Technology and Risk Aspects
2 The new energy world
3 Consequences for Steam Turbines
4 Description of Increased Risks
5 Some Examples
6 Risk Mitigation
7
Table of contents 1 General Technology and Risk Aspects
2 The new energy world
3 Consequences for Steam Turbines
4 Description of Increased Risks
5 Some Examples
6 Risk Mitigation
8
Steam Turbines, Some Key Facts
Largest single steam turbine set: ~1650 MW
Max. Lengths of rotor trains: ~ 65 m
Weight of a LP rotor: 300 t
Max. LP Exhaust Area: 30 sqm
Min. radial clearance: 0,3 mm
Value up to : 200 Mio €
Laval: 1883Antique Heron wheel Today
9
Steam Turbines, Some Key ComponentsL-0 blade
rotor
Last stage blade
vanes
Source: Siemens
10
Steam Turbine Evolution (1)Development Steam Turbines in Fossil Fired Power Plants in Germany
1970 2000 2020 Time
560
580
600
Supercritical
Mature Technology
Current marketintroduction
R&D ongoingNi-basematerials
Life Steam Temperature(°C)
620
Subcritical
1980 1990 2010
700
Max.Unit Capacity(MW)
800
900
1000
1100 Neurath F, G
Niederaußem K
Lippendorf R,SHeyden
Scholven G
11
Steam Turbine Evolution (2)
Length of Last Stage Blade (LSB), development steps 3000 rpm
1990 Time
1000
1100
48 inch longest LSBof many manufacturers
2005 - 2012
2000 2010
1200
1300
1400
1500mm
steel
titanium
12
Risk Evaluation for Steam Turbine operation
Loss Experience
Technology Level
Field Experience
Repair Options
OperationParameters
Maintenance Concept/Budgets
Operational Excellence
Protection
13
Transfer into standardized risk assessment tool
identical and consistent for all lines of business
providing qualitative and quantitative results
Global network management, Expert Teams and Lessons Learned providebest practice and consistency
Local risk information captured by ARC engineers
.. transformed into risk quality describing ..
.. and processed to the business
Portfolio
5,06,6
-5,0
2,2
-10,00
-5,00
0,00
5,00
10,00
Pla
nt A
Pla
nt B
Pla
nt C
Pla
nt D
1,3
4,4
0,02,3
0
20.000.000
40.000.000
60.000.000
80.000.000
100.000.000
120.000.000
Pla
nt A
Pla
nt B
Pla
nt C
Pla
nt D
-10
-5
0
5
10
14
Table of contents 1 General Technology and Risk Aspects
2 The new energy world
3 Consequences for Steam Turbines
4 Description of Increased Risks
5 Some Examples
6 Risk Mitigation
15
In 2012 the renewable share generated was 22%of which 11,3 % are solar + wind
Quelle : BDEW 2012
19%
11%6%
22%
16%26%
Electricity generation in Germany 2012 : 617 MRD KWh
Hard coal
Gas
Oil, pumpstorage ,othersRenewables
Nuclear
Lignite7,30%
5,80%
3,30%
4,60%
0,80%Waste
Solar
Hydro
Biomass
Wind
16
In 2012 the renewable share generated was 22%of which 11,3 % are solar + wind
Quelle : BDEW 2012, and AZT estimates
However:Steam Turbinesstand for 2/3 ofgeneration
19%
7,5%6%
16,2%
16%26%
Electricity generation in Germany 2012 : 617 MRD KWh
Hard coal
Gas
Oil, pumpstorage ,othersRenewables
Nuclear
Lignite
~3,5%
~3,5%
17
The first day in Germany with Green energyproduction peaking over conventional generation
0
10
20
30
40
50
60
70
Electricity Generation in Germany on ?
Coal + Nuclear Wind Solar
GW
Source : IWR 2013
Your guess ?
18.04.2013
18
Operation Conditions Germany
high wind and solar production mainly impacts hard coal based production
nuclear and lignite withmoderate and hard coal withhigh load variation
19
Balancing PVs
Technical min. Load duringnights
No operation on weekends
No operation 26th to 29th October due to strong wind
Operation Conditions of a german hard coal power plant
20
© Copyright Allianz Global Corporate & Specialty 13-11-08
Table of contents 1 General Technology and Risk Aspects
2 The new energy world
3 Consequences for Steam Turbines
4 Description of Increased Risks
5 Some Examples
6 Risk Mitigation
21
New situation for power plants (hard coal, CCPP)
3. Primary and Secondary power operation mode
1. Specific costs and contracts determine usage
2. Profitability difficult to maintain
Maintenance budgets and periods under question
4. Operation as consumer for capacity power (Gt´s, pump storage, NPP Biblis)
22
New operation for power plants (hard coal, CCPP)
2. Increase of operation in low and minimum loads
1. Decreased low and minimum loads
3. Increased number of starts
4. Increased load gradients
How does this work and what are the upcoming
risks out of thischallenging boundariesfor the steam turbines ?
5. Increased number and longer time of outages
23
Additional Aspect: The German Capacity of hard coal Power Generation is 36 Years old
Ref. : Public data of Umweltbundesamt, Bundesnetzagentur
The average power plant and steam turbines weredesigned for base loadand middle load (nightstand still, daily starts )
24
© Copyright Allianz Global Corporate & Specialty 13-11-08
Table of contents 1 General Technology and Risk Aspects
2 The new energy world
3 Consequences for Steam Turbines
4 Description of Increased Risks
5 Some Examples
6 Risk Mitigation
Flexibility:load ramp and
no. of starts
max. capacity
min. load
load
rang
e
time time
Change of load situation
26
2. Expected Higher Nozzle and Valve Erosion Rates
1. Increased HP-IP vibrations (partial arc admission)
3. More water droplet erosion due to lower live steam temperatures
4. Increased Exhaust Temperatures due to LP ventilation, different axial expansionincreased spray flow and erosionreduced clearance and potential rubbing
6. HP ventilation
7. IP valve vibrations
8. Changed frequency band of feed water pump turbines Increase of wear and
tear and damage risk
Minimum Load
Increased Risks due to changed loads (1)
5. Excitation of LP blades due to ventilation
27
2. Higher Nozzle, Valve and LP section Erosion Rates
1. Increased HP valve vibrations
3. Increased Exhaust Pressurecritical in air condenser applicationsincreased load on LP blades at trips
Increase of wear and tear and damage risk
Max Capacity
Increased Risks due to changed loads (2)
4. Excitation of LP blades due to Flutter Vibration
5. Changed frequency band of feed water pump turbines
28
2. LP blades + rotors with higher Low Cycle Fatigue (mech.)
1. Hot Components with higher Low Cycle Fatigue (thermal)
3. Increased risk of crack propagation especially ofprecracked or prefatigued rotating components
5. Valve seat and sealing wear
6. Stand still corrosion
Increased Risks due to changed loads (3)
Increase of wear and tear, corrosion, fatigueand damage risk
Flexibility
4. LP blades: extended operationtimes with high cycle fatigue
7. Drainage Issues in case of manualdrainage
29
Increased Risks due to changed loads (4)
Increase of:- wear and tear- corrosion- fatigue- damage risk
Flexibility
Max Capacity
Min Load
30
Table of contents 1 The new energy world
2 General Technology and Risk Aspects
3 Consequences for Steam Turbines
4 Description of Increased Risks
5 Some Examples
6 Risk Mitigation
31
What do you need to expect out of this
based on damage cases where turbines alreadyoperated under respective load conditions
based on proven engineering know how and
average ability of engineers to predict ;-)
32
Max Capacity
33
First free standing blade row
Detachment after 80.000 to 130.000 operation hours
Fußbruchstück mit Rastlinien
Example: Blade Failures on feed water pump turbines
34
Damage Causes
Fatigue fracture caused by periods of resonance due to modifiedspeed range (load uprate of main turbine)
+ pitting corrosiondue to stand stills
+ corrosion fatigue
35
Occuring at high steam flows
Self exciting mechanism
High effort to calculate
Measurable
Potential blade failures
Example: Flutter Vibrations
01/ 2011 © Copyright Allianz
Blade aplitudes
36
IncreasedFlexibility
37
L-2 after 170.000 h / 1.500 Starts L-1 after 100.000 h / 1.000 starts
Even with former moderate start/stop
sequences rotor grooves and balde roots
require attention and special
maintenance efforts
Increase of starts will reduceyears of component usage
Example: LCF in Rotor groove cracks
38
Optimizing a 40 year old mid size power generation turbine forsecondary load control
Normal Operation„4“closed, 3 MW/min
Optimization for 12 MW/min: „4“ rapid open and closing, 550°C
180 bar
Did the additional load cycles of optimization
cause the cracks in the valve inlet section
of the outer casing ?
39
Data Aquisition
α / Wm-
2K-1
Boundary Conditionsanalysis of operational dataestimation of heat transfersdetermination of a load cylce
Geometryno drawings or CADoptical 3 D scanFE model
40
02/ 2012 © Copyright Allianz
Results: Temperature Differences
Diff. Temp of load cycle, Valve 4
41
Resulting stress
Stress vs time at crack location
ΔσFE
Location of highest stress matches with observed crack location
Optimization of operation leads to crack growth,
But: Value of stress amplitude shows that additional factors need to increase the stress locally.
Stress amplification can be caused by low casting quality
42
Other consequences of increased load ramps
The consequences are
-Increased maintenance costs and outage time for repair
- reduced remaining lifetime
LCF-cracks at an HP-Casing
LCF-cracks at stationary bladingof IP-turbine
43
Reducedminimumloads
44
Blade Failures caused by low load
L-1
L-0
45
The problem with low loads
„This is like diving your car in 1st gear only“
Source: ASME paper 1986 „Design Criteria for ReliableLow-Pressure Blading“, Meinhard Gloger, et al.
46
The problem with loaw loads: excitation by ventilation
• CFD calculation: vortex area depending on individual exhaust cone
• Rule of thumb: below 25 % nominal flow ventilation must be expected
Source
47
Identifying low load failures: Fatigue Fracture
ventilation
Low load
Random blade excitation
Fatigue Fracture
Danger of rotor failure
4848
Identifying low load failures: Droplet erosion at the trailing edge close to the root
ventilation
Low load
Backflow with saturated steam
Droplet erosion
Increased notch factor and risk of crack growth
49
Identifying low load failures: Tip rubbing
1 2 3 45
67
8
9
10
11
12
13
14
15
16
17
18
1920
2122
2324252627282930
3132
3334
35
36
37
38
39
40
41
42
43
44
4546
4748
4950 51 52
Blade Row L-1:■ fractured■ tip rubbing■ ok
ventilation
Low load
Local temperature increase
Local temperature increase
Additional Elongulation of blades
50
Identifying low load failures:Discoloration and / or build up of scale
51
0%
2%
4%
6%
8%
10%
12%
14%
0 bis 1 1 bis 1,1 1 ,1 bis 1,2 1,2 bis 1,3 1,3 bis 1,4 1,4 bis 1,5 1,5 bis 1,6 1,6 bis 1,7 1,7 bis 1,8 1,8 bis 1,9 1,9 bis 2,0
=> Pressure ratio over last stage below 1 (at load over 200MW)
51
Identifying low load failures:Analysis of operational data
52
Other consequences of low load operation
This is not easy and not fast to repair
Erosion of casing splitting LP-Last stage blading drop erosion
LP-Last stage stationary blading erosion
53
Table of contents 1 General Technology and Risk Aspects
2 The new energy world
3 Consequences for Steam Turbines
4 Description of Increased Risks
5 Some Examples
6 Risk Mitigation
54
Risk IncreaseAgeing of turbine fleet
55
Wear and TearCorrosionFatigueMaterial DamageBusiness Interuption
Risk Balance
RiskIncrease
Changed Risk Balance…
56
Wear and TearCorrosionFatigueMaterial DamageBusiness Interuption
Individual plant analysisApropiate Operational MeasuresTailor Made concepts of ManufacturersAwarenessRisk Control
RiskIncrease
RiskMitigationMeasures
Risk Balance
…requries individual and joint approach…
…to mitigate new risksDevelopment needs not only to considerefficieny and costs but also flexibility and reliability !
57
Loss control programs
Client services
Monitoring and coordinationCRM programs
Risk improvements and loss mitigation concepts
Business Continuity
Engineering Consulting
Special services
Know-How transfer
Loss analysis & support
Laboratory forensics
Emerging Risks Observation
Lessons Learned generation
Loss Control programs help mitigate the new risks
Additional Services bundled / unbundled
Technical risk assessment
Underwriting services
DTR (Desk Top Review)
MFL/PML calculation and risk evaluation
Risk Survey
Recommendation tracking
Core Service/ Portfolio protection
Prototype Evaluation….
58© Allianz Global Corporate & Specialty AG, 08.11.2013
Contacts
Stefan ThummAllianz Risk Consulting GmbH – Allianz Zentrum für Techink, Operational ManagerTelephone: +49 (0)89 3800 6643Email: [email protected]
Allianz Global Corporate & Specialty AG
Dr. Martin EckelEngineering Claims Germany, Head of Complex Claims Telephone: +49 (0)89 3800 13229Email: [email protected]
Dr. Rüdiger BeauvaisRisk Consultants Engineering Germany, Senior Risk EngineerTelephone: +49 (0)89 3800 4385Email: [email protected]
© Allianz Global Corporate & Specialty AG 2013. All rights reserved. Information contained in this document is provided without liability forinformation purposes only and is subject to change without notice. No representation or warranty is given or to be implied as to the completenessof information or fitness for any particular purpose. Reproduction, use or disclosure to third parties, without express written authority, is prohibited.