Mechanical Connector Thread Design for High Torsional Loads
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Solution Overview
Problem
Existing mechanical connectors, such as those in the Merlin™ family, face limitations in handling high torsional loads and fatigue due to their design, which affects their performance in offshore engineering applications where torsional and bending loads are significant.
Innovation Solution
The introduction of structural features like dog-clutch teeth, fitted pins, keys, splines, and interlocked thread systems, combined with modifications in the shapes of boxes and pins, and the use of assembly/disassembly fluids that solidify, enhances the connectors' ability to manage high torsional loads and fatigue, while maintaining high bending load capacities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional Merlin™ family connector designs are used, then high static and fatigue strengths are achieved for axial and bending loads, but torsional load capacities are limited and difficult to control accurately
Solution Approach 1:
The connector is divided into functional segments: the box and pin components, sealing elements, and torque transfer mechanisms (splines, keys, or dog-clutch teeth). This segmentation allows each component to be optimized for its specific function while maintaining overall structural integrity and controlling complexity through modular design.
Solution Approach 2:
The connector design integrates multiple functions into a single device: axial load transfer through threaded engagement, bending load resistance through structural geometry, torsional load transfer through splines/keys/dog-clutch teeth, and sealing through nipple seals. This multi-functionality improves torsional capacity without proportionally increasing device complexity.
2Weight of moving object
If variable outside stress diameters and inside stress diameters are implemented, then weight control and stiffness optimization are improved, but manufacturing complexity increases
Solution Approach 1:
The box and pin features variable diameters at different locations along their lengths, with larger diameters in high-stress regions and reduced diameters in low-stress regions. This local variation optimizes weight by removing material where it is not needed while maintaining stiffness and strength where required, balancing weight control with manufacturing feasibility.
3Reliability
If assembly/disassembly fluids that solidify are used, then sealing and torque transfer are enhanced, but operational temperature range is restricted
Solution Approach 1:
The assembly/disassembly fluid is selected to solidify at operational temperatures, transitioning from liquid to solid phase. This phase change provides enhanced sealing through solidification and improved torque transfer through rigidification, but requires careful selection of fluid properties to match the specific operational temperature range of the application.
Data Source
AI summary
A Merlin™ family mechanical connector provided with a thread on substantially matching frustoconical surfaces extending between two sets of nipple seals utilize assembly/disassembly fluids that solidify after the assembly and are brought to liquid state before the disassembly. They include resins or tar-like non-metals and liquid metals solidifying in single phases as well as in multiple phases like for example binary, ternary etc. eutectics. That improves already very good leak resistance of Merlin™ family connectors and benefits good heat transfer between pins and boxes. Thread angle mismatching between box and pin threads can be introduced in order to improve loading. The above modifications can be introduced to traditional connectors featuring torsional load capacities limited to frictional resistance and to connectors designed to transfer high torsional loads.