INTRODUCTION TO LEADING EDGE REPAIR AND PROTECTION
Wind turbine leading edge protection has been one of the most talked about topics when it comes to wind turbine maintenance. The leading edge is responsible for the blade’s aerodynamic efficiency and power output. For this reason, the leading edge protection (LEP) gets the most attention nowadays.
In one of our previous posts “Maintaining Renewable Energy”, we touch upon the maintenance issues encountered in the wind power turbine as a whole, and the solutions Belzona offers for the repair and protection of each part of the turbine. In this post, our focus is the leading edge protection.
What is a leading edge?
The leading edge of a blade is the foremost edge of the airfoil or the part of the blade that first contacts air.
Leading Edge Wear and Tear
Cause of the leading edge damage can vary based on the terrain a wind farm is located in. Typically, leading edge defects can be caused by wet (rain, sleet, hail, snow) and/or dry (dust, abrasive air, bugs) atmospheric and environmental particulates. Lightning strikes and surface icing are two other atmospheric phenomena that might cause tear and, in some extreme cases, even rupture in the blade. The life expectancy of an unprotected leading edge at the manufacturer’s facility can be significantly decreased. According to Windy Systems Magazine, eroded leading edges will reduce the aerodynamic efficiency of the blades, and many sites have measured decreased power production by as much as 12%.
Leading Edge Protection
In recent years, more blade manufacturers have started offering various type of LEP including tapes and protective coatings. However, that is not the global trend. Many wind farms currently in operation face the challenge of protecting the damaged blades and keeping the turbines running and producing energy.
BELZONA HOW-TO
The solutions offered by Belzona are suitable to be applied on new build equipment as a preventative measure, as well as to repair and protect damaged equipment already in operation. In this post, we demonstrate the repair of a blade that had been damaged in service.
Leading Edge Protection Drawing
Belzona’s wind-specific solutions can repair and protect the leading edge of turbine blades using Belzona 5711 and Belzona 5721. Eroded blades must first be rebuilt to the original profile, before being overcoated with a protective coating.
For this repair, we use Belzona 5711, Belzona 5721, Belzona 9111 (Cleaner/Degreaser), and a few tools from our machine shop. The first step is preparing the surface. Using a handheld sander, remove the existing coating and apply Belzona 9111 (Cleaner/Degreaser) to remove all loose particles and achieve optimal adhesion. After equalising the filling levels, a specialised mixing nozzle is then attached to a Belzona-issued cartridge containing Belzona 5711. The mixed product is applied onto the repair area using an electric cartridge gun. A flexible plastic former should then be used to smooth out the surface, sculpting the product to the blade’s original geometry.
After 30 minutes at 20°C (68°F), the repair can be overcoated with Belzona 5721 for long-lasting LEP. Belzona 5721 is mixed thoroughly for a minimum of two minutes until a uniform material is achieved, before decanting the mixed product into a cartridge for extended working life and ease of application. After ensuring that the product is flowing freely, beads are applied onto the leading edge of the blade before being smoothed with a flexible closed cell former. The product is then allowed to cure before the blade is returned to service; this typically takes five hours at 20°C (68°F).
VIDEO: BELZONA 5711 PRODUCT INTRODUCTION - REPAIR SOLUTION FOR WIND TURBINE BLADE DAMAGE
Step 1: Surface Preparation
Prepare the surface area with a sander. If necessary, clean and degrease the area with Belzona 9111.
Step 2: Equalise filling levels
Extrude a small bead of Belzona 5711 to equalise the filling levels before attaching the specialised mixing nozzle to the cartridge.
Step 3: Apply Belzona 5711
Apply the mixed Belzona 5711 directly from the cartridge onto the prepared blade.
Step 4: Smooth out the product
Using a flexible plastic former, contour the Belzona 5711 to the blade’s original geometry.
Step 5: Allow product to solidify
Leave to solidify according to atmospheric conditions. Belzona 5711 can be overcoated with Belzona 5721 after 30 minutes at 20 °C (68 °F).
Step 1: Mix Belzona 5721
Mix Belzona 5721 thoroughly for a minimum of two minutes to achieve a uniform material.
Transfer the mixed product into a cartridge. This will extend the pot life of the coating and increase the ease of application.
Once the product is flowing freely, apply beads of Belzona 5721 directly onto the blade, over Belzona 5711 – Belzona 5721 can also be applied to other areas of the blade which have not needed rebuilding with Belzona 5711. However, surface prep would be required.Step 4: Smooth to the blade
Smooth to the blade with a flexible closed cell foam former.Step 5: Allow product to cure fully
Allow to cure before returning to service. This will typically be 5 hours at 20 °C (68 °F).Completed Application
Yulia Burova, Marketing Director, Belzona Inc., Miami FL, USA
Dear Yulia. I have studied your article with great interest. R&D A/S, Denmark has developed and delivered 6 Rain Erosion Tester to major blade supplyer and Coating companies. We are interested to start a dialog with your company. Please let me know who to contact in your organization.
Thanks in advance.
Ole