Wind Turbine Anchor Bolt Replacement Method
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Solution Overview
Problem
The existing methods for replacing anchor bolts in wind turbine foundations are time-consuming and costly, requiring disassembly of the turbine, which is not feasible while the turbine is operational, leading to potential weakening of the foundation and reduced life expectancy.
Innovation Solution
A method involving drilling a core around the anchor bolt, removing it, and inserting a replacement bolt that is tensioned and coupled to the foundation using internal threads and an insert, allowing for in-situ replacement without disassembling the turbine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the tower is removed from the foundation to replace anchor bolts, then the anchor bolts can be replaced, but the wind turbine assembly time and productivity are significantly reduced
Solution Approach 1:
The foundation is segmented into a removable upper portion and a stationary lower base flange. The upper foundation portion containing the damaged anchor bolts can be removed and replaced without affecting the lower base flange that remains embedded in the ground, enabling anchor bolt replacement while preserving the permanent foundation structure.
Solution Approach 2:
A reusable anchor bolt assembly serves as an intermediary component between the removable upper foundation and the permanent lower base flange. This assembly can be detached, repaired or replaced, and reattached, avoiding the need to remove the entire tower while still enabling anchor bolt replacement.
2Ease of repair
If the tower is removed from the foundation to replace anchor bolts, then the anchor bolts can be replaced, but the cost of disassembly and reassembly increases
Solution Approach 1:
By segmenting the foundation into removable and permanent portions, only the necessary upper section needs to be disassembled for anchor bolt replacement, significantly reducing the scope and cost of disassembly and reassembly operations compared to removing the entire tower structure.
Solution Approach 2:
The foundation design provides different properties to different portions: the lower base flange is designed to remain permanently embedded in the ground with high stability, while the upper foundation portion is designed to be removable for maintenance. This local differentiation reduces the cost of repairs by making only the necessary local changes.
3Ease of operation
If anchor bolts are not sufficiently post-tensioned, then the anchor bolts may loosen over time, but the foundation life expectancy is reduced
Solution Approach 1:
The reusable anchor bolt assembly includes pre-installed anchor bolts that are properly tensioned before the upper foundation portion is attached to the lower base flange. This preliminary tensioning ensures that the anchor bolts maintain sufficient post-tensioning from the start, preventing future loosening and extending foundation life.
Solution Approach 2:
The design allows for inspection and replacement of anchor bolts through the removable upper foundation portion, enabling ongoing monitoring of post-tensioning levels. If anchor bolts show signs of loosening, they can be detected and replaced, providing feedback-based maintenance that prevents foundation degradation.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A method of replacing an anchor bolt used to support a wind turbine to a foundation. The method includes providing the wind turbine and the foundation supporting the wind turbine. The foundation includes a lower base flange, at least one anchor bolt extending between the lower base flange and a lower tower flange of the wind turbine, and a rigid body at least partially formed around the at least one anchor bolt. The method further includes drilling a core in the lower tower flange and the rigid body circumferentially around the anchor bolt and removing the anchor bolt and the core to create a cavity. The method further includes inserting a replacement anchor bolt into the cavity and coupling the replacement anchor bolt to the lower base flange. The replacement anchor bolt may then be tensioned.