Spacer-Tube Stud Bolt Assembly for Wind Turbine Flange Joints
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Solution Overview
Problem
The limited load-bearing capacity of conventional L-flange connections in tall wind turbine towers poses a constraint, and existing flange connection technologies do not adequately address the need for a fast and secure connection that can handle the increased loads of modern wind turbines with longer rotor blades.
Innovation Solution
A stud system comprising a stud bolt with a head end, threaded end, and intermediate portion, along with a spacer tube that prevents the stud bolt from slipping into the flange opening, allowing pre-installation on flanges, and a method for connecting flanges using these stud systems to form a permanent connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional L-flange connections are used, then the structure is simple and easy to manufacture, but the load-bearing capacity is limited
Solution Approach 1:
The flange connection is segmented into multiple functional zones: a bolt circle for primary fastening and an X-shaped aperture pattern for enhanced load distribution. This segmentation allows each zone to serve specific structural purposes, thereby increasing overall load-bearing capacity while maintaining manageable complexity through functional division.
Solution Approach 2:
The flange design transitions from the symmetric L-flange configuration to an asymmetric X-flange pattern with inclined openings. The asymmetric X-shaped aperture arrangement optimizes stress distribution under complex loading conditions, enabling the connection to handle higher loads that symmetric configurations cannot efficiently support.
2Reliability
If flanges are connected using traditional methods, then the connection can be made, but the threads and surfaces are at risk of damage during assembly
Solution Approach 1:
Stud bolts are pre-installed into the flange openings before the mating flange is positioned. This preliminary action ensures that the threaded portions are already in place and properly oriented, eliminating the risk of thread damage that would occur if bolts were forced into aligned holes during final assembly. The pre-installed studs simply receive the mating flange's fasteners without risk of misalignment damage.
Solution Approach 2:
The stud bolt acts as an intermediary element between the two flanges. Instead of directly forcing fasteners through aligned holes (which risks thread and surface damage), the stud bolts serve as intermediate receivers that the mating flange's fasteners engage with. This intermediary mechanism decouples the alignment requirement from the fastening action, protecting threads and surfaces from damage.
3Productivity
If flanges are connected with pre-installed studs, then assembly is faster, but the studs may slip into the openings and damage threads
Solution Approach 1:
A spacer tube serves as a temporary intermediary component that fits over the pre-installed stud bolts. This spacer tube prevents the stud bolts from slipping further into the openings during the assembly process, thereby protecting the threads from damage. The spacer tube is removed after the mating flange is properly positioned and secured, having fulfilled its protective function throughout the critical assembly phase.
4Power
If taller towers are constructed to accommodate longer rotor blades, then the wind turbine capacity increases, but the load-bearing capacity of L-flange connections becomes insufficient
Solution Approach 1:
The tower structure is segmented into multiple sections connected by standardized flange assemblies. Each flange connection is designed as a self-contained unit with the X-shaped aperture pattern that can handle the increased loads from taller towers and longer rotor blades. This segmentation allows the connection design to be optimized for high load-bearing capacity while maintaining modularity for easier manufacturing and assembly.
Data Source
Figure 1
Figure 2~3
Figure 4~5D
AI summary
The invention describes a stud system (4) for connecting a first flange (1) to a second flange (1) of a tower (5), the flanges (1) comprising annular arrangements of openings (1thru) in the first flange (1) corresponding to annular arrangements of threaded blind openings (1_part) in the second flange (1), the stud system (4) comprising: - a stud bolt (2) with a head end (2a), a threaded end (2d) and an intermediate portion (2c) between the head end (2a) and the threaded end (2d) and - a spacer tube (3) partly encompassing the stud bolt (2), wherein the stud bolt (2) comprises stopping means (2b) at the head end (2a), preventing the spacer tube (3) from slipping over the head end (2a), and wherein the spacer tube (3) is constructed such that it can be removed laterally from the stud bolt (2).