Threaded Connection with Variable Pitch and Interference Ring
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Solution Overview
Problem
Drilling tools used in hydrocarbon recovery face challenges with high torque and bending loads, leading to potential breakage or loosening of threaded connections in subterranean formations.
Innovation Solution
A threaded connection design with a larger section modulus, featuring threads positioned at the outer diameter of one component and a tapered inner surface, combined with a connection ring for interference fit, and variable pitch or taper to balance thread loads, enhancing torque and bending capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If threaded connections are used to couple drilling tool segments, then the tools can be assembled and disassembled for transport and maintenance, but the threaded connections are subject to high torque and bending loads that can cause breakage or loosening
Solution Approach 1:
The threaded connection is divided into distinct functional zones: a box portion with internal threads, a pin portion with external threads, and a connection ring portion. This segmentation allows each component to be optimized for its specific function while working together to solve the overall problem of high load capacity with maintainable connections.
Solution Approach 2:
The threaded connection utilizes composite structural design combining different geometric configurations (tapered sections, cylindrical sections, variable pitch threads) within a single connection system. This composite approach enables the connection to simultaneously handle both assembly ease and high torque/bending loads through the synergistic interaction of its various structural elements.
2Strength
If the section modulus of the threaded connection is increased to handle higher loads, then the torque and bending capacity improve, but the complexity of the connection design increases
Solution Approach 1:
The connection features localized geometric variations including tapered sections at specific locations, variable pitch threads in certain zones, and a connection ring with interference fit capabilities. These local quality modifications concentrate structural reinforcement where most needed, achieving high section modulus without uniformly complicating the entire connection design.
Solution Approach 2:
The threaded connection incorporates variable pitch threads where the thread spacing changes along the length of the connection. This dynamic geometric feature allows the connection to adapt to varying load conditions along its length, providing higher section modulus where loads are greatest while maintaining simpler geometry in lower-stress regions.
3Strength
If threads are positioned at the outer diameter to maximize section modulus, then the bending and torque limits increase, but the risk of galling and fracture at the thread roots increases
Solution Approach 1:
The connection design incorporates a connection ring portion that provides interference fit and load distribution before the threaded portions are fully engaged under high load. This preliminary cushioning action prevents stress concentration at the thread roots, reducing the risk of galling and fracture while still allowing threads to be positioned at the outer diameter for maximum bending and torque capacity.
Solution Approach 2:
The connection ring acts as an intermediary element between the box and pin portions, providing a transition zone that distributes loads and protects the threaded connections from direct high-stress contact. This intermediary structure enables the threads to be positioned optimally for strength while the connection ring shields them from the most severe galling and fracture risks.
Data Source
AI summary
An example threaded connection includes first component and a second component. The first component may have a first outer diameter, a first threaded portion at or near the first outer diameter, and an end portion. The second component have may a second outer diameter a second outer diameter greater than the first outer diameter; a second threaded portion, at least one of the first or second sets of threads having at least one of a variable pitch and a variable taper; and an internal shoulder positioned to contact the end portion of the first component when the first threaded portion are engaged with the second threaded portion. A connection ring may be coupled to the second component and positioned to engage with a portion of the first component when the first component is positioned within the second component.