special risks for steam turbine operation due to changed energy … thumm_special... · 2013. 8....

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

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© 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 ?

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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

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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

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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

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Steam Turbines, Some Key ComponentsL-0 blade

rotor

Last stage blade

vanes

Source: Siemens

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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

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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

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Risk Evaluation for Steam Turbine operation

Loss Experience

Technology Level

Field Experience

Repair Options

OperationParameters

Maintenance Concept/Budgets

Operational Excellence

Protection

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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

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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

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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

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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%

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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

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Operation Conditions Germany

high wind and solar production mainly impacts hard coal based production

nuclear and lignite withmoderate and hard coal withhigh load variation

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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

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© 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)

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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

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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 )

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© 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

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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

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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

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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

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Increased Risks due to changed loads (4)

Increase of:- wear and tear- corrosion- fatigue- damage risk

Flexibility

Max Capacity

Min Load

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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

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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 ;-)

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Max Capacity

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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

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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

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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

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IncreasedFlexibility

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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

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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 ?

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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

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02/ 2012 © Copyright Allianz

Results: Temperature Differences

Diff. Temp of load cycle, Valve 4

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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

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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

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Reducedminimumloads

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Blade Failures caused by low load

L-1

L-0

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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.

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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

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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

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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

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Identifying low load failures:Discoloration and / or build up of scale

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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)

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Identifying low load failures:Analysis of operational data

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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

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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

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Risk IncreaseAgeing of turbine fleet

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Wear and TearCorrosionFatigueMaterial DamageBusiness Interuption

Risk Balance

RiskIncrease

Changed Risk Balance…

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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 !

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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: stefan.thumm@allianz.com

Allianz Global Corporate & Specialty AG

Dr. Martin EckelEngineering Claims Germany, Head of Complex Claims Telephone: +49 (0)89 3800 13229Email: martin.eckel@allianz.com

Dr. Rüdiger BeauvaisRisk Consultants Engineering Germany, Senior Risk EngineerTelephone: +49 (0)89 3800 4385Email: ruediger.beauvais@allianz.com

© 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.