Stepped Wind Tower Flange Connection for Self-Sealing Fatigue Resistance
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Solution Overview
Problem
Wind tower flanges face high cycling loads and fatigue issues due to bending moments, and existing L-type flanges with high displacement openings pose challenges for implementing additional sealing systems to protect against environmental conditions.
Innovation Solution
A flange connection system featuring self-energized flange rings with a radially extending portion and stepped contact surfaces, which creates a static connection with high contact pressure, allowing for self-sealing and enhanced fatigue resistance, and optionally incorporating seal rings for additional protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If L-type flanges with high displacement opening are used, then ease of assembly is improved, but sealing performance deteriorates requiring additional sealing systems
Solution Approach 1:
The flange face is segmented into multiple contact zones with different heights (stepped configuration), creating distinct sealing regions. The first contact surface is at a higher elevation than the second contact surface, allowing separate sealing functions for different load conditions while maintaining assembly ease.
Solution Approach 2:
Different regions of the flange contact surface are given different local properties through the stepped design. The first contact surface region provides primary sealing under normal conditions, while the second contact surface region provides secondary sealing under high load conditions, with each region optimized for its specific function.
2Reliability
If additional sealing elements are added to protect against environmental conditions, then sealing performance is improved, but device complexity increases
Solution Approach 1:
The flange connection system performs sealing automatically through its own structural features (stepped contact surfaces and seal pockets) without requiring external sealing elements. The geometry of the flange faces and the presence of seal pockets enable the connection to seal itself under various load conditions.
Solution Approach 2:
The stepped flange design serves multiple functions simultaneously: structural load bearing, self-sealing under normal conditions, and secondary sealing under high load conditions. The seal pockets serve both as sealing chambers and as features that guide proper flange alignment during assembly.
3Strength
If flange connection is designed for high bending moment loads, then strength is improved, but fatigue resistance deteriorates due to cyclic loading
Solution Approach 1:
The transition from the flange ring to the flange neck employs an elliptical or curved geometry instead of sharp corners. This curved transition distributes stress more evenly and eliminates stress concentration points that would initiate fatigue cracks under cyclic loading, while still maintaining the strength required for high bending moments.
Solution Approach 2:
The geometry of the flange connection is optimized with specific parameters including the stepped contact surface heights, the elliptical transition curvature, and the seal pocket dimensions. These parameter optimizations enable the connection to withstand high bending moments while minimizing stress concentrations that lead to fatigue failure.
Data Source
AI summary
A flange connection system, including a pair of flange rings each including a neck portion and a radially extending flange portion. The radially extending flange portion includes a distal face including a contact surface that protrudes from a remainder of the distal face. The radially extending flange portion includes a plurality of circumferentially spaced bolt holes extending parallel to a center axis. The distal face including a first seal pocket radially inward of the contact surface and a second seal pocket radially outward of the contact surface, wherein in an assembled condition, the contact surface of the first flange ring is disposed against the contact surface of the second flange ring, a first seal ring is disposed in the first seal pockets, and a second seal ring is disposed in the second seal pockets.