Staggered Tooth Wellhead Connector Stress Distribution
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Solution Overview
Problem
Existing wellhead connector designs with minor image tooth profiles lead to unequal stress and contact force distribution, with the loading surface closest to the connector body bearing a disproportionately large percentage of stress, resulting in potential connection failure under high pressures.
Innovation Solution
A staggered contact design where initial contact is established at the lowermost end of the collet and wellhead, with additional loading surfaces engaging radially inwardly, distributing stress more evenly across the loading surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a minor image tooth profile is used on the locking dog to match the wellhead profile, then the connector can engage the wellhead teeth, but the stress and contact force are unequally distributed with the loading surface closest to the connector body bearing a disproportionately large percentage of stress
Solution Approach 1:
The tooth profile on the locking dog is designed with asymmetric spacing between teeth, where the spacing varies along the length of the locking dog. Specifically, the spacing between adjacent teeth is greater near the connector body and smaller toward the distal end, which compensates for the progressive elongation and creates more uniform stress distribution across all loading surfaces during engagement
Solution Approach 2:
Different sections of the locking dog tooth profile have different tooth spacing characteristics tailored to their specific functional requirements. The proximal teeth (near the connector body) have larger spacing to account for greater elongation, while distal teeth have smaller spacing, creating locally optimized stress distribution throughout the engagement interface
2Ease of operation
If the tooth profile on the locking dog matches the wellhead tooth profile, then engagement is achieved, but the loading surface closest to the reference line experiences the lowest percentage elongation and carries more stress
Solution Approach 1:
The locking dog tooth profile deliberately departs from a simple minor image copy of the wellhead profile by introducing asymmetric tooth spacing. This asymmetric design ensures that teeth experiencing greater elongation (those farther from the reference line) are spaced to engage more effectively, balancing the load distribution and enhancing overall connection strength while maintaining straightforward engagement
3Adaptability or versatility
If radially moving dogs with matched tooth profiles are used, then the connector can connect the body to the wellhead, but the stress concentration at the loading surface nearest the connector body increases the risk of connection failure under high pressures
Solution Approach 1:
The locking dog tooth profile incorporates asymmetric spacing that varies along the length of the dog, with larger spacing near the connector body and smaller spacing toward the distal end. This asymmetric configuration compensates for the progressive elongation that occurs during radial movement, distributing stress more uniformly across all teeth and reducing the risk of connection failure under high pressure conditions
Data Source
AI summary
In accordance with certain embodiments, the present invention provides a connector for attaching to a multi-toothed profile on a wellhead features a tooth profile that staggers loading preferably starting at a loading surface furthest from the connector body sitting on the wellhead and moving toward the connector body. The staggered loading more evenly distributes stresses on the matching loading surfaces as compared to the result of using a tooth profile on the connector that nearly exactly matches the profile on the wellhead. The joint can then take advantage of an increased preload and exhibit improved stress characteristics when operating at high loading conditions.