Advanced Engineering for G47 Mainframe Cracks
The occurrence of cracks in the mainframes of G47 and V47 wind turbines is a widely recognized issue in the wind energy sector, especially in localized areas of the mainframe associated with welded joints. These cracks are typically caused by stress concentration factors arising from both the structural design of the mainframe and its manufacturing process. When this structural configuration is subjected to the cyclic loads inherent to wind turbine operation, the risk of fatigue cracking at critical points increases significantly. In response to this, Nabla Wind Hub applies advanced engineering solutions to identify, analyze, and mitigate these structural damages, extending asset life and ensuring safe and efficient operation.
Gamesa G47 Mainframe most critical Checkpoints
This case study focuses on a specific wind farm experiencing structural damage in a significant portion of its fleet of Gamesa G47 wind turbines. Due to cracks and deterioration in the mainframes, several machines were out of service, resulting in high operational costs for the client. The main goal of the project was to design and validate a damage mitigation plan to keep as many turbines operational as possible, while minimizing downtime and associated costs.
To develop an effective damage mitigation plan, a detailed analysis of the structural condition of each turbine was conducted, specifically focusing on the type and progression of the cracks detected in the mainframes. The technical approach was based on evaluating the feasibility of crack-arrest holes, a technique widely used in structural engineering to slow crack propagation by redistributing stress at the crack tips, thus reducing peak stress concentrations.
Global model with crack-arrest holes
In the first phase, following a field inspection and measurement campaign, the affected wind turbines were classified into different groups based on the length of the existing cracks. These ranged from 150 mm — the threshold established by the supplier — to over 300 mm in the most critical cases.
Next, the site’s wind conditions were analyzed, and aeroelastic simulations were carried out to develop a representative model of the G47 wind turbine’s dynamic behavior. This aeroelastic model served as the foundation for a Finite Element Analysis (FEA), in which both the cracks and the crack-arrest holes were incorporated to validate their effectiveness.
During this analysis, different combinations of crack lengths and hole diameters were evaluated, ensuring that the structural components maintained integrity under both extreme loading and fatigue conditions. The results showed a significant reduction in stress concentrations at the crack tips when the arrest holes were introduced, confirming the suitability of this solution to extend the service life of the affected wind turbines and ensure their safe operation.
The implemented mitigation plan, tailored to the specific conditions of the wind farm, allowed wind turbines to be classified by criticality level and addressed with differentiated solutions: some wind turbines were returned to normal operation, while others were operated with certain limitations, depending on the degree of identified damage and risk level. This strategy led to a significant reduction in costs associated with prolonged downtime and structural repairs (e.g., welding), improving overall asset availability.
Nabla recommends ongoing monitoring through periodic NDT (Non-Destructive Testing) inspections using penetrating liquids to track crack development and ensure structural behavior remains within expected margins.
Thanks to this approach, part of the wind farm’s production capacity was recovered, minimizing the economic impact of downtime and providing an effective, safe, and cost-efficient technical solution to a recurring structural problem in this type of wind turbine.
