Life extension by effective life time management. Andreas Klenk Materials Testing Institute University of Stuttgart

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1 Life extension by effective life time management Andreas Klenk Materials Testing Institute University of Stuttgart

2 Introduction Lifetime management Why? Safety Availability Reducing maintenance efforts and costs Why is extended lifetime management often being avoided Costs Implications in the design phase and at the beginning: Who is responsible - who is interested in who is paying for? Experience from other technical sectors Safe Life X - network to use synergies in ageing assessment 2 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

3 Introduction Lifetime management Where is advanced lifetime management applied previously? - Some Examples Nuclear Power plants: Safety issues in the focus, strong regulations to ensure safe and reliable operation of plants and individual components Fossil fired power plants Pressurized equipment: Safety issues according to specific regulations, surveillance More pronounced: Availability reducing outages Reducing maintenance efforts and costs 3 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

4 Outline Introduction What can we learn from other applications? Basic requirements for advanced life assesment Conclusions for Wind Energy applications Summary Outlook 4 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

5 Basis Safety Concept Quality Quality Through Through Production Production Principle Principle Optimisation Qualification Control Design Material Manufacturing Multiple Multiple Parties Parties Testing Testing Principle Principle Independent Quality Assurance Worst Case Principle R & D Work Failure Investigation Plant Plant Monitoring Monitoring Documentation Documentation Principle Principle Continuous / Repeated In-service Monitoring Surveillance Non Destructive Examination Validation Principle Codes and Standards Design and Operation Fracture Mechanics Irradiation Non Destructive Examination Clear Target: Ensure safe and reliable operation of nuclear plants Safety demand due to high risk during operation Costly Not directly applicable, but: Basis Safety Independent Redundancies PRINCIPLES: Basis Safety Concept : Exclusion of Catastrophic Failure Incredibility of Catastrophic Failure Principle Kussmaul, K., German Basis Safety Concept rules out Possibility of Catastrophic Failure, Nuclear Engineering International 12 (1984), pp. 41/46 Quality Assurance and documentation of the asbuilt-state Monitoring and documentation Validation: Design and operation assessment, reliable life prediction analysis 5 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

6 Number of component failure Life time management Schematic description of failure/damage development Life time according to design Failures due fabrication, lack of quality Failure due to life time expenditure Additional service loading Loading according to design I II III Inspection - large intervalls - Recognition and identification of early stages of damage, risk-based life assessment Service time h Flexible inspection intervalls - adjusted on life time consumption and damage development condition based monitoring 6 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

7 Life time consumption TRD 301, EN Case study - piping system in coal plant LIFE TIME CALCULATION - MONITORING T Check of plausibility Interpolation if necessary Average wall temperature: Use of algorithms, if no direct measurement availlable Algorithms for stress, strain calculation (Standards): s, Ds bzw. De As built geometry Creep rupture curve e Z Fatigue curve e W p plausibility check Interpolation if necessary 7 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

8 Case study coal plant piping Total life time consumption Linear damage accumulation: creep + fatigue e Life time calculation - TRD 301, 508, AD 2000, EN e z e w 1 Specific measures have to be taken exceeding specific degrees Uncertainties: Scattering material characteristics Deviation design geometry and as built geometry, Uncertainties in determining operational data (pressure, temperature) and use of analytical equations for stress and strain calculation Influence of manufacturing on material characteristics Linear damage accumulation rule Additional loading not foreseen in original design Kriechschädigung TRD und 316 SS (austenitische Stähle) ASME N / 4 Cr1Mo (niedriglegierte Stähle) ASME N47 Ermüdungsschädigung HA10_1.OPJ Ni-Fe-Cr Alloy 800H (Nickelbasislegierungen) ASME N47 8 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

9 Case Study - Isometric view of live steam line GKM power plant Commissioned: 1965 Operation time: > h Design parameters: h, 245 bar / 530 C To Do: Calculation of life time consumption of individual components Ranking of criticality Determination of critical components Evaluation of possible life time extension Recommendations about inspections and maintenance Status: Calculated lifetime consumption at individual components (especially pipe bends) > 200% in year 1998 Non destructive tests yielded no distinctive material damage Replacement of pipe bends and destructive testing showed thermal degradation of the material 9 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

10 Case Study Approach: Evaluation of data supplied by the customer (GKM) Updating of component geometry data, plausibility check etc Calculation of component specific total lifetime consumption (creep + fatigue) by means of ALIAS software (certified by TÜV): Results Ranking (examples) Life time consumption in different time periods Component Replica (VGBrating) Exhaus tion Very high amount of life time consumption at individual components - High component stresses / High operation temperatures 10 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

11 Case Study - considering influencing parameters Results Evaluation of decisive influence variables Significant influence on calculated life time consumption: Scatter in material data Example for impact on creep life consumption Uncertainties in loading characterisation: Normal conditions Impact on fatigue life consumption T reduced by 5K II + T changing velocity limited to 4,59 K/min 11 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

12 Case Study - perspectives from life assessment Scenarios Course of the calculated life time consumption is lower/higher than black design curve: Reasons: p/t (operation) </> p/t (design) As built geometry / Operational Malfunctions Material characteristics above lower bound / additional loads Consequence: Life time extension for first scenario is possible without changing operation mode (curve 1) or Increasing operation parameters p/t (curve 2) second scenario only by decreasing load (curve 3) 12 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

13 Case study - identifiying critical components Application of risk based life assessment procedure 13 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

14 Summarizing basic requirements Effective lifetime management 1. Critical components have to be identified, showing largest amount of life time consumption 2. Global and local loading situation at the individual component must be identified and reflected by the computation methods used 3. Life time consumption has to be calculated on the basis of recorded operation data 4. Specific load situation and material dependent damage mechanisms have to be considered 5. Material data considering the specific load situation must be available 6. An effective non destructive testing concept for monitoring detected early stages of damage must be available 7. Traceable and comprehensive documentation of manufacturing, operation. 14 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

15 Consequences for wind turbine applications Quality assurance, inspection and lifetime optimisation of wind turbines Ensured quality during manufacturing and mounting well defined state at begin of life Intelligent monitoring for the determination of actual structural loads Application of probabilistic methods for RBI (Risk based Inspection) on the basis of the RIMAP/CEN CWA method according to VGB R506 critical components Application of more detailed analyses for life assessment Application of improved NDT methods Fatigue strength verification, determination of error tolerances, admissible defect sizes with theoretical and experimental methods 15 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

16 Monitoring Example: Fatigue life monitoring of structural members and foundation (e.g. grout) by deformation measurement on tower M, N, Q 16 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

17 Risk based management procedures The RIMAP / CEN CWA method according to VGB R506 is already successfully used in power plants: Define boundary conditions Data gathering and validation Multiple steps risk analysis Decision making and optimisation Taking measures Evaluation of results - Probability of Failure (PoF) - Consequence of Failure (Cof) - Risk (PoF x CoF) - Operation Surveillance - Inspection - Maintenance Evaluation of critical components 17 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

18 More detailed analysis Advanced calculation tools - fatigue CMF: Complex Multiaxial Fatigue Complex multiaxial fatigue concept - MPA Stresses &Strains Input & Calculation Calculation of critical surface FP - Fatigue damage par. FP mean curves Uni/multiaxial tests Standards Direct calculation Beanspruchung Loading (Component) (Bauteil) Evaluation Bewertung Beanspruchbarkeit Load bearing capability (Probe) (Material) 18 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

19 Material data knowledge about material behavior Determination and validation of material properties 10 Dehnungsamplitude e a strain amplitude Manson-Coffin-Gleichung Manson-Coffin-Equation 1 0,1 elastischer Anteil Elastic Plastic plastischer Anteil 0, Lastwechsel Cycles to failure bei Anriß 19 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

20 Summary and conclusions Prerequisites for life time extension are documented quality Advanced lifetime management based on operational data (monitoring) and validated knowledge of material properties using appropriate methods (state of the art, risk based methods, advanced analyses) Principles and (partly) mechanisms and procedures of other technical sectors can be used for advanced lifetime management of wind turbines 20 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

21 Summary and conclusions - Safe Life X Title: Safe Life Extension management of aged infrastructures networks and industrial plants From Sept to August 2015 To build cost-effective solutions to handle the problem of infrastructures aging in the next 10 years ( ) by providing specifications for new RDI projects EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014 Courtesy: Steinbeis R-Tech (Advanced Risk Technologies) 21

22 Safe Life X - Objectives To improve synergy between several industry sectors To identify the good (best) practices To define a strategic research agenda (SRA) and an implementation strategy (Roadmap) To initiate and develop pre-standards and standards 22 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014

23 Thank you for your attention 23 EWEA Workshop: Analysis of operating Wind Farms, Malmö, 9-10 Dec 2014