YCE: provider of applied structural engineering solutions
The repair activities are carried out according to the most updated technical standards DNV-GL and IEC.
YCE Repair System: priorities of blade repair design
Complete repair of the blade at height, from both the structural and aerodynamic point of view
We design and build all spare parts in-house:
- in the absence of as-built data we perform reverse engineering of the blade structure;
- we build the moulds needed;
- we produce in our factory the spare parts needed for our reconstruction work.
We perform specific R&D activity:
- advanced structural repair techniques;
- LPS retrofits for many blade models;
- anti-ice coating application.
Exceptional shell damage and YCE repair techniques
Lightning strikes generate a heat-shock that reaches temperatures above 3,000°C for some tenths of a second. The presence of unrepaired cracks and minor damage on the surface of the blade causes the leaking of water inside the blade. When this water is subject to very high temperatures, the instant evaporation causes the resulting gases to expand very rapidly: a violent explosion takes place.
Since this happens during bad weather conditions, the wind tower generator is at the same time subject to high winds: the explosion causes the two shells (that form the blade shape) to split open and be torn away.
The repair procedure for such damage involves the reconstruction at height of the blade, using spare shells:
- damaged parts are removed, application area is cleaned and rectified;
- damaged blade is reconstructed using spare shells;
- detailed final reconstruction of the airfoil is made by bodywork and the final sacrificial layer (the layer that protects blades from several damage causes) is reconstituted.
YCE repair techniques provide for the reconstruction at height.
YCE has developed specific repair procedures for traditionally built blades and for the more innovative “one-shot” Siemens blades.
However, such damage can be prevented: constantly monitoring and evaluating the state of the blades allows for early identification of critical conditions and the subsequent timely planning of maintenance, thus reducing the probability of extraordinary damage.
Structural damage to spar and composite sandwich laminates
Following YCE procedures, as per best practices based on internationally approved technical rules, partially damaged structural parts are reconstructed by substituting the missing fibres, respecting orientation and volume.
Particular attention is paid to the original specification of the blade in the area of the repairs, especially when the damage extends over a wide area.
Work is carried out in line with YCE procedures within specific weather ranges, according to material specifications and techniques used.
Monitored data includes temperature and humidity.
The materials used are included in YCE structural engineer’s specific operating instructions to the field team.
Erosion and cosmetic damage
Erosion and the ageing of the sacrificial layer are the root cause of structural damage leading to long downtimes.
YCE has developed specific techniques to address the deterioration of the sacrificial layer, which is the layer that protects blades from several damage causes (UV rays, erosion, etc.).
Timely maintenance of the sacrificial layer ensures rotor blades have a longer worklife.
Most rotor blades, even the newest designs, are damaged by lightning strikes. Apart from the immediate damage caused by the lightning (the formation of plasma that burns the sacrificial layer of the blade), overheating caused by the intensity of the current through the earthing system causes the vaporization of the water that leaked inside the blade.
The instantaneous transformation of this water into gas and its immediate expansion may cause mechanical damage to the tip area.
YCE research has developed a retrofit that improves LPS (Lightning Protection System): YCE LPS retrofit®.
YCE LPS retrofit® prolongs the lifecycle of the blades by extending the electrical attraction area of the receptor, mechanically strengthening the blade tip
and improving the Lightning Protection System.