Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 222222
Loughborough University

Centre for Innovative and Collaborative Construction Engineering

2011

Ujjwal Bharadwaj

Dr Ujjwal Bharadwaj

Thesis

Methods for Risk Based Life Management for Offshore Structures and Equipment

Project Title

Methods for Risk Based Life Management for Offshore Structures and Equipment

Company

TWI Ltd

Supervisors

Academic:
Professor V Silberschmidt
J Andrews

Industrial:
Mr John Wintle
Dr Lee Smith

Director of Research:
Professor Dino Bouchlaghem

Research Period

2005 - 2010

Methods for Risk Based Life Management for Offshore Structures and Equipment

Current state of the art

The periodicity and extent of wind turbine maintenance is based on recommendations from the original equipment manufacturer (OEM) who, in a large number of cases, carries out the work. For mechanical components the maintenance plans are based on experience gained from the operation of on-shore wind turbines and the OEMs' product performance knowledge. Guidelines for structural components are based on experience gained from the off-shore oil & gas operations and reflect the very high emphasis that is placed on safety by that industry. The result is that the turbine maintenance schedules for both turbines and structures are not optimised for their role or environment. This, in turn, leads to higher maintenance costs coupled to reduced availability and operating life. This helps prevent the cost of renewable energy reducing to a more commercially attractive level.

Objectives

The objective of the project is to enable a reduction in life cycle costs of offshore wind farms thereby contributing to an overall goal to achieve wind energy prices which are attractive to consumers. The project will develop the specification for a software tool that will establish optimum risk-focussed inspection and maintenance planning.

Outputs

The proposed output is a specification for a software tool which integrates life/risk models, reliability statistics and on-line monitoring data. The software would be used to (i) establish optimum, risk-focused inspection and maintenance planning and (ii) enable selection of cost effective design, engineering or material modifications to mitigate risks and extend maintenance intervals and operating life.

Research tasks

1. Identify damage and degradation mechanism for offshore wind turbine structures and turbine mechanical/rotating equipment.
2. Develop probabilistic models based on predictive life analysis for structural degradation mechanisms covering several tower and foundation designs.
3. Collate historical functional fault and failure data for turbine/mechanical parts and formalise as customised databases for relevant designs. Establish reliability models.
4. Perform consequence analysis taking account of availability loss and safety issues and combine with probability/reliability modes to provide predictive schemes for the evaluation of risk exposure with time.
5. Develop algorithms for inspection and maintenance scheduling.
6. Develop risk-cost optimisation schemes.
7. Produce a software design specification with modules for a) risk-focussed inspection and maintenance planning and b) cost effective risk mitigation and extended maintenance intervals.
8. A pilot implementation on a designated wind farm may be used to demonstrate and validate the key features of the risk model and procedural specification.

Technical description of the proposed innovation

The project will address the integrity management of the wind turbines, tower and foundation structures using a risk management approach designed to accommodate reliability databases as well as structural health monitoring data. A formal integrated approach will be adopted based on the principles of risk-based maintenance. Such approaches are recognised in other sectors where the cost-benefits are proven. Probabilistic structural-mechanical life models will be developed and calibrated for simulated loadings and environment. A Reliability database will be incorporated, particularly for rotating equipment. Each of these will yield evaluations of increasing failure probability with time. Consequence costs particularly associated with availability loss will be used in association with the probability analysis and projected failure modes to quantify the evolution in overall risk exposure during operation. The methodology will be incorporated in a specification for a software tool to enable risk-based planning of inspection and maintenance timing and focus for given wind farm and throughout several wind farms. The tool will also enable the impact of various risk mitigation measures to be assessed and optimum measures selected through a risk-cost optimisation process. In particular a feedback route to identify and select design, engineering or materials modifications to achieve maintenance frequency targets will be delivered. The project represent an innovative approach to wind farm design, inspection and maintenance coupled with an extensive knowledge of fault and failure histories as experienced by current, mostly non-UK, offshore operators

Bharadwaj, U.R., Silberschmidt, V.V, Wintle, J.B. (2012). A Risk-based Approach to Asset Integrity Management, Journal of Quality in Maintenance Engineering, Vol. 18 (4), pp. 417-431.
http://dx.doi.org/10.1108/13552511211281570

Bharadwaj, U.R. … et al. (2009). Optimisation of resources for managing competing risks, 10th International conference on Engineering Structural Integrity Assessment, EMAS, 19-20 May, 2009, Manchester, UK.
http://www.twi-global.com/technical-knowledge/published-papers/optimisation-of-resources-for-managing-competing-risks-may-2009/

Bharadwaj, U.R. … et al. (2008). A risk based approach to spare parts inventory management, International Mechanical Engineering Congress and Exposition (IMECE), ASME, November 2-6, 2008, Boston, Massachusetts.
http://apem-journal.org/Archives/2011/APEM6-3_173-184.pdf

Bharadwaj, U.R. … et al. (2007). A practical approach to risk based assessment and mainternance optimisation of offshore wind farms, Proceedings of OMAE2007 26th International Conference on Offshore Mechanics and Arctic Engineering, June 10-15, 2007, San Diego, California, USA.
http://www.twi-global.com/technical-knowledge/published-papers/a-practical-approach-to-risk-based-assessment-and-maintenance-optimisation-of-offshore-wind-farms-june-2007/

 

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Loughborough University
Leicestershire
LE11 3TU

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