Together, we make your blades stronger Bladena’s new simple retrofit for increased reliability and repair of the trailing edge bonds Dr. Carsten Hein Westergaard President, NextraTEC Inc. Board member, Bladena Aps Bladena representative [email protected]Sandia National Laboratories Wind Reliability workshop 2013 August 13 – 14, 2013, Albuquerque Bladena US based service partners
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Dr. Carsten Hein Westergaard: 2013 Sandia National Laboratoies Wind Plant Reliability Workshop
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Together, we make your blades stronger
Bladena’s new simple retrofit for increased reliability and repair of the trailing edge bonds
• Design system, verification system and standards applied: – Non accommodating for critical errors; for example; lack of combined loads
verification during testing– Exclusion of important failure mode combinations; for example, breathing of panels
which leads to accelerated peeling
• Manufacturing deficiencies:– Tolerances, random and/or systematic; for example, incorrect application of fibers– Quality deviations; for example, application of glue or curing of glue bond deviations
• Unforeseen blade loading events:– Systematic; for example, by failure of sensors– Random occurrence; for example, induced by extreme weather events
• Service methods– It is very difficult to detect hairline cracks, service methods can influence the root
cause of failure mode development
• Almost always, failure is a sequence or combination of these root causes
Static safety against damage to blade skin from D-string
• A comprehensive test program of the D-String has been performed at DTU, demonstrating safety margins against damage to the supporting blade skin foam sandwich
• A string (fuse) is included for well defined protection at breaking point 1.5kN
• Field test has shown measured string loads are very low, with peaks up to 0.4kN during emergency stops
Increased reliability based on measured data• Based on the in-situ measured deformation and stress, the lifetime stress
reduction can be calculated. By using Palgren-Miners, rule the life extension can be calculated
• In the pilot projects, the measured improvement from the D-string is a 97% reduction in stress. This can be translated to: “If the blade was prone to cracks after 4 years, the life expectancy would be expanded to 40 years, i.e. a factor 10 in lifetime”